Santa Cruz Astronomy Club

Our galaxy, the Milky Way, is a massive spiral. It’s actually in one of the top tiers of galaxies in the Universe, tipping the cosmic scale at several hundred billion times the mass of the Sun.

We’re stuck inside it, so it’s difficult to get the big picture; imagine trying to understand the shape of a forest after being plopped down inside of it, halfway between the center and the edge. And, oh yeah, you’re stuck there, unable to move.

Astronomers have an advantage over our lost forest dweller, though: We have telescopes that allow us to see a lot of our galaxy (including using radio waves and other forms of light that allow us to peer deeply into it and tease out some answers). We can also see lots of other galaxies and learn from them. And we also have math and physics, which allow us to investigate why they form the shapes they do.

Our investigations have led to two new results that are both pretty cool. One is that we have a better understanding of the way those spiral arms might form. The other is the arm we happen to be in is bigger than we thought.

I’m Perturbed

The galaxy is a really huge flat disk, with the spiral arm pattern in it. Stars nearer the core orbit the center of the galaxy faster than ones farther out, and so you might expect the arms to wind up over time. But they don’t. That led astronomers to think of them like density waves, like traffic jams with stars instead of cars. A traffic jam isn’t a solid thing; cars enter it on one side, slow down, make their way through it, and leave on the other side. Over time, the jam is still there, but the individual cars come and go. That’s a density wave.

Spiral arms are similar. The problem is we don’t understand how they get started or why they last so long. But a new idea has come along that may answer both.

Astronomers created a computer model of a galaxy disk made up of 100 million stars (test particles, as they’re called) and let them interact through gravity. They also added huge clouds of gas and dust called giant molecular clouds (GMCs) to the simulation and let them orbit as well. What they found is that the GMCs poked at the smoother gravity of the disk, perturbing it. Over time, as the stars circled the galactic center, the effect was to create a spiral pattern in the disk, just like those seen in real galaxies. Not only that, but once created, the spiral pattern persisted even after the GMCs were removed (which can happen; they collapse to form stars in the real Universe).

This new result is interesting because it solves some problems of the older ideas. One was that the arms are self-sustaining through their own gravity, but a lot of simplifying assumptions had to be made for that to be true. The new simulations show the arms are able to stick around without those assumptions. Their simulations also show that once created, local fluctuations in the density of stars in the arm act to perturb the disk, creating the conditions needed to sustain the arms, even once the “seed” perturbers go away.

Sustaining the arms has been a long-standing problem in galactic physics, and this may be the solution. Of course, there’s always more to learn and more things to add to the models. I expect this will be a fruitful course of investigation for a long time.

Strong Arm

The Sun orbits the center of the galaxy roughly once every 240 million years or so. It passes in and out of spiral arms as it does so, and we’ve known for some time that we are between two major arms: the Perseus arm (because you can see it in the direction of the constellation Perseus) and the Sagittarius arm.

It was thought we were in a weak spur, called the Local Arm, a small linear feature that branches off a major arm at a steep angle. But new observations using the Very Long Baseline Array radio observatory indicate that our Local Arm is not just a spur, but either a large branch off the Perseus arm or a major arm unto itself.

They did this by looking at star-forming gas clouds using the radio array. A fancy technique called interferometry allowed them to get very precise measurements of the positions of the clouds. They then observed the clouds over time, as the Earth orbited the Sun. Our changing position relative to those clouds is tiny but enough to see a small shift in their position. This technique is called parallax, and it’s been used for a long time to determine the distance to nearby stars. Now we can use it with radio arrays to get accurate distances and positions for some objects much farther away. The astronomers used this to map the three-dimensional location of these clouds, essentially mapping out the local arm.

What they found is that the pitch angle, the angle at which our arm curls away from the galactic center, is low; in other words, it only curls away very slowly and doesn’t stick out, pointing away from the galactic center like spurs do. They also found it’s very long, more than 15,000 light-years end-to-end. The Milky Way is about 100,000 light-years across, so this is a substantial distance.

So it looks like we’re not in a spur, but a bona fide previously unknown arm. Go us!

The Way of the Milk

What I like about both of these new results is that we’re finding surprising things about the Milky Way, even though we’re inside it. It’s like living in a house your whole life and then finding a new room in it, or one that was bigger than you thought, and that the house wasn’t originally constructed the way you thought it was.

In some ways our own galaxy is the hardest to study. You live inside your head, but without a mirror, you’d never know what your face looks like; it’s easier to see other people and extrapolate from that. We do that with galactic astronomy, and with new techniques and better computers we can get a better grasp of our own house.

And although this might all seem esoteric and weird, it’s not. Well, it is, but it really is also about where we live. If you go outside on a dark evening in the (Northern Hemisphere) summer months, the Milky Way dominates the sky. You can see it as a white fuzzy glow stretching across the entire sky. For millennia we had no idea what that light was, but now we know it’s the combined might of hundreds of billions of stars, a disk so huge it takes light 1,000 centuries to cross it, and it’s home.

And every day, we get better at understanding it.

The Kennedy family name is laden with history and brings to mind a definite set of characteristics: glamor, power, intelligence, wealth, influence. Kennedys have had their name on a president, numerous senators, representatives, ambassadors, and other high office holders.

The Kennedy dynasty, if you wish to call it that, has seen its share of triumphs and disasters, of course. I need not go into detail; scores of books have been written about them, from putting humans on the Moon and the championing of civil rights to personal tragedies of assassination, death, scandal, and more.

Most of these issues are in the past. But there is an ongoing problem associated with a Kennedy, one I consider extremely troubling. Specifically it’s with Robert F. Kennedy Jr., who is an attorney, a radio host, and an environmental activist.

He is also, as it happens, a full-blown anti-vaccination conspiracy theorist.

And I do mean full-blown. RFK Jr. has a long history of adhering to crackpot ideas about vaccines, mostly in the form of the now thoroughly disproven link to autism. He’s been hammering this issue for a decade now, and his claims appear to be no better and no more accurate now than they were when he first started making them.

To be clear, I am a parent myself, and when my daughter was an infant, my wife and I fretted over this issue. Concerned about her development and health, we did the research and found that the overwhelming benefits of vaccination far outweighed the very slight actual risks. That is why our daughter is fully vaccinated, as are both my wife and I. We keep our booster and flu shots up to date as well.

So the anti-vax claims of Kennedy are very concerning to me. I’ve written about him before, but he came to my attention again when Keith Kloor at Discover magazine noted Kennedy was the keynote speaker at the 2013 AutismOne/Generation Rescue Conference. Both AutismOne and Generation Rescue claim to be about advocating for people touched by autism—and there is no doubt their concern is genuine—but when you scratch the surface you find they also advocate dangerous nonsense about medicine and treatment.

To give you an idea of what these organizations are about, Generation Rescue is fronted by notorious anti-vaxxer Jenny McCarthy, about whom I’ve written many times (here is a post with plenty of links about her)—but if you want a great overview of why McCarthy is so bad, read this open letter to Oprah Winfrey about her in 2009. Nothing has changed since that was written. Generation Rescue has a well-known advocacy for anti-science, commonly misinterprets real science, and has a history of nasty attacks on those who point out their logical fallacies.

AutismOne, for its part, is just as bad. In 2010 the group issued a letter in support of Andrew Wakefield calling him a “hero” and invited him to speak at this year’s conference. This is the same man who is largely responsible for the modern anti-vax movement due to his unethical and fraudulent research that led to a paper linking vaccines and autism in 1998. That paper was later withdrawn by the Lancet, and many of the co-authors disavowed it. His misdeeds are being widely blamed for the current measles epidemic in Wales and other countries.

Together, these two groups put on the conference, which is a veritable what’s what of nonsensical and, in many cases, unproven autism “therapies,” from homeopathy to bleach enemas. And yes, you read that correctly.

Which brings us back to RFK Jr. I wasn’t at all surprised he’d be a speaker, even the keynote, for a joint convention between these two groups. In many ways, the modern anti-vax movement owes as much to him as to Wakefield. In 2005, he published a remarkable essay in Salon and Rolling Stone called “Deadly Immunity,” linking the preservative thimerosal to autism. The article was overwhelmingly ridden with factual errors, so much so that Salon later took the extreme measure of removing the article from its archives. But the damage was done. Kennedy had helped mainstream the fear of vaccines.

In the ensuing years he has hardly eased up. Kennedy has a radio show called Ring of Fire where he advocates for various issues and causes. In 2011 he had Boyd Haley, a retired chemist and promoter of various “alternative” treatments, on as a guest. This is a man the medical skeptic Orac calls a “crank” and who has had several run-ins with the Food and Drug Administration because of his claims for some of the products he sells, which have not been shown to be effective and safe.

Kennedy’s interview with Haley is on YouTube:      

On the radio show, Kennedy and Haley discuss thimerosal, and it’s an astonishing litany of false anti-vax talking points. Because of possible health concerns at the time, thimerosal was essentially removed from all vaccines years ago; the only exception is the multidose flu vaccine. As the Centers for Disease Control puts it,

Since 2001, no new vaccine licensed by FDA for use in children has contained thimerosal as a preservative, and all vaccines routinely recommended by CDC for children younger than 6 years of age have been thimerosal-free, or contain only trace amounts of thimerosal, except for multi-dose formulations of influenza vaccine. The most recent and rigorous scientific research does not support the argument that thimerosal-containing vaccines are harmful. However, CDC and FDA continually evaluate new scientific information about the safety of vaccines.

If thimerosal were the cause of autism, we should see a drop in autism rates once the use of the preservative was stopped. Those rates did not drop; in fact, they've increased over time (likely due to better diagnoses rather than an actual increase in prevalence).

That was a case-closed moment for the idea that thimerosal caused autism. However, RFK Jr. and Haley, as true conspiracy theorists do, simply dismiss that inconvenient truth. They claim that the studies were flawed, even fraudulent, that ethylmercury (used in thimerosal) is dangerous, that “massive fraud” is going on, that the Amish don’t get autism (an old canard that is simply untrue); they claim anything and everything except that thimerosal has never been shown to have an association with autism.

Incidentally, going full-tilt-conspiracy at the very end of that interview, Kennedy calls the scientists and doctors at the CDC “criminals” because “they are poisoning kids.” Wow. These people he defames have devoted their lives to researching, understanding, and mitigating the effects of diseases that sicken and kill millions of people around the world, and Kennedy dismisses them out of hand, accusing them of harming children.

Since Kennedy gave the keynote address for the AutismOne/Generation Rescue convention in May, I can only assume his stance is still virtually fact-free. The AutismOne site says this about his speech:

[Kennedy has] been involved in the fight to hold government health agencies responsible for the vaccine-induced autism epidemic. Kennedy's article Deadly Immunity chronicled the cover up by the CDC and FDA blasting the agencies for putting politics before science. He comes to the conference with a new book that further exposes the dangers of thimerosal and ongoing corruption of the CDC.

So it’s clear his stance has not changed from firm denial of reality, fitting in with the conference’s aims at large. Unfortunately, I have seen neither a transcript nor video of his speech. I hope one becomes available; I’m obviously quite curious about precisely what he had to say.

I’ll note former Rep. Dan Burton (R-Ind.) spoke at this conference as well. He has long advocated anti-vax quackery, even participating in shameful hearings in Congress about it. It goes to show you that some anti-science knows no partisan bounds; it’s hard to imagine many other issues the conservative congressman and Kennedy would agree on.

That’s an important point. A lot of anti-science tends to be a wholly owned subsidiary of the Republican Party: climate-change denial, evolution denial, stem-cell research, anything going against the more fundamental tenets of religion. Some of these are actually incorporated into the party’s planks. The Democrats are more diverse (and haven’t embraced their own flavors of anti-science in the party planks), but progressives do cleave to some anti-science, most broadly things like being against GMO foods and supporting “alternative” medicine. This is peculiar to me; I’d think a priori most progressives would be more likely to embrace science, but in these specific cases, at least, they’ve abandoned it.

I find that disappointing. I think of myself as a progressive in many ways, though I take things on a case-by-case basis. By definition a progressive wants to move forward, to look to the future, rather than look back to a semi-mythical “good ol’ days.” That progress must include embracing science, the evidence behind it, and the methodology that leads to amore accurate understanding.

Progressives may be more inclined to listen and believe what Kennedy has to say simply because of his name. But they also need to know that facts, evidence, huge numbers of studies, and reality itself are at odds with his claims. Like Wakefield, McCarthy, Generation Rescue, and AutismOne, Kennedy is saying things that are not only utterly wrong but also dangerous.

With outbreaks of preventable diseases around the world and people, including babies, dying from them, the claims of the anti-vaxxers constitute a public health threat. The more people who understand that, the less likely we’ll be to see epidemics from diseases that have no business infecting people in the 21st century.

My opinion: Don’t listen to crankery, whether it’s from Kennedy or an autism advocacy group. Instead, talk to your board-certified doctor. If he or she recommends getting your vaccinations, do it.

For further reading, I recommend these articles about Kennedy and his denial of reality:

Is Robert F. Kennedy Jr. Anti-Science? by Keith Kloor
Should Obama’s Cabinet Include RFK, Jr.? at Skeptic Dad
Politics and Science – The RFK Jr. Test by Steve Novella
Can antivaccinationists knock it off with the autism Holocaust analogies already? (RFK, Jr. edition) by Orac
Inside the Vaccine and Autism Scare by Rahul Parikh at, ironically, Salon

Over the weekend, I wrote about a surprise solar storm that sparked aurorae over the northern United States, including an amazing pink display photographed by Brad Goldpaint.

He took enough pictures of the event to create a phenomenal (if too short) time-lapse video of the event, including a surprise at the very end: a pass of the International Space Station.

An interesting thing happens around 40 seconds into the video: A series of white patches can be seen moving right to left. They look to be above the dark clouds (which move the opposite way). Brad brought them to my attention; I suspect these are just high-altitude clouds glowing softly, but I’m not sure. I am pretty sure they are not aurorae themselves, since they’re white. An aurora can be green, red, blue, purple, or pink, but white is a combination of colors that is, as far as I can tell, essentially impossible to create in this way. (It would need a very specific blend of those component colors, which is highly unlikely.) So I’m leaning toward them being clouds. Opinions?

Over the next few days there will be a great series of passes by the ISS over the United States. You can find out if you can see it by going to Heavens Above (have your latitude and longitude handy), or ISS Astroviewer, or the Real Time Satellite Tracker. It’s fun to watch it move across the sky, and knowing that there are six human beings on it right now.

Astronaut Chris Hadfield returned safely to Earth in May after spending several months in space. During that time, he took amazing and beautiful pictures of our world from his high perch, and when he came home, many people worried that it would mean a cessation of such photographs.

Worry no more. Italian astronaut Luca Parmitano tweeted this jaw-dropper just this morning:

Wow. (You really want to click that to embiggen it, too.) When Parmitano tweeted it, he said, “The low sun creates beautiful contrasts with the #clouds: I just don’t get tired of it! #volare.” He didn’t say whether the Sun was rising or setting, and I couldn’t squeeze the info from the picture saying when it was taken. But either way, the long, long shadows coming from the clouds are lovely.

And I noticed something rather fun in the picture, too. The shadows look nearly but not quite parallel; on the sides of the picture the shadows are angled slightly outward. However, I think this is an illusion: They are actually parallel, but what you’re seeing is perspective. It’s exactly the same as a pair of railroad tracks appearing to converge in the distance at what’s called the vanishing point.

For all intents and purposes, the Sun is infinitely far away in this picture; the photo only covers a few hundred kilometers (at most) left to right, but the Sun is 150 million kilometers away. That means the direction to the Sun is the same for any cloud in this shot (I’m ignoring the curvature of the Earth, which isn’t important), and in turn that means their shadows are parallel. But Parmitano was shooting at a slight angle, pointing his camera toward the Sun a bit and not straight down. That adds perspective to the shot, like looking along railroad tracks as they go off in the distance. And that’s why the shadows don’t look parallel, even when they are.

I don’t think we have to worry about the new Space Station crew not holding on to the long tradition of tweeting beautiful views from space. And just to drive that point literally home, American astronaut Karen Nyberg tweeted this the other day:

Her caption? Simply, “Sunset.” It was the first picture she took from her new home. I think Expedition 36 is going to work out just fine.

On June 2, 2003, the European Space Agency launched the Mars Express probe to the red planet. It arrived later that year, entering orbit and starting its mission to study the Martian climate, atmosphere, and geology and to look for signs of water on the surface.

Although the attempt to set the lander Beagle 2 on the surface resulted in the lander's loss, the orbiter has been far more successful. To celebrate the 10th anniversary of launch, the ESA released this devastating picture of the north polar ice cap of Mars:

You really want to click that picture to embiggen it. It’s lovely—a mosaic of 57 separate pictures, enough to cover the 1,000-kilometer-wide (600-mile-wide) ice cap.

The ice there is mostly water ice, permanently frozen. However, there’s a thin layer of frozen carbon dioxide—dry ice—that coats it every winter and sublimates (turns directly from a solid into a gas) every summer. That means the ice cap changes all the time, making it a target of study.

I’m fascinated by the swirls in the ice. The Martian atmosphere is thin, only about 1 percent as thick as Earth’s, but it’s enough to carry dust aloft and to erode features into the surface. The spiral pattern is most likely the result of those prevailing winds. Amazingly, over long periods of time, those spiral arms move, rotating around the pole, like the arms of a pinwheel (or a galaxy). Oddly, the arms move in the opposite direction of the wind. As the wind blows down the warmer, sunward-facing side of a trough, it picks up water vapor and ice. When it blows across the other side, which is colder, it deposits that water as ice. So the wind erodes the ice in the upwind direction and deposits it downwind. Over time, that means the ice appears to migrate in the opposite direction the wind blows.

That’s pretty wild. Mars is a surprising place, with dust devils, avalanches, ancient lake beds, and now counter-rotating aeolian-carved boreal icy spiral arms. It never ceases to amaze me.

Congratulations to the Mars Express team for their anniversary! May we continue to explore our local worlds for many, many more years.

The number of exoplanets—worlds orbiting other stars—grows almost daily, with about 900 such planets confirmed at this time. But the vast majority are found through indirect means: their affect on their host star, or the way their gravity distorts the light of background stars, or how much light they block when they pass between us and their star.

Only a very few have been seen directly, literally having them seen distinct from their host star in an image. Fewer than a dozen have been detected this way, and even then the existence some of those is contested (I have a gallery of all the known directly imaged exoplanets as well). But now we can (almost certainly) add another one: HD 95086 b. And a bonus: it’s the lowest mass such exoplanet seen yet.

The star, HD 95086, is very young (only about 10-17 million years old or so) and a bit more massive and hotter than the Sun. It’s about 300 light years away, making it relatively close by on a galactic scale.

The planet is technically a candidate planet, because we can’t be 100 percent sure it’s actually a planet. It could, for example, be a background star, but the astronomers who discovered it rate that possibility as very low. They observed the star three times; once in January 2012 and again in February and March of 2013. The star is close enough to Earth that its actual motion in space can be detected—as the Sun and this star orbit the center of the galaxy, their relative positions change slightly with time. It’s small, but measurable. The object appears to move along with the star, which it wouldn’t do if it were some distant background star (like how mountains in the far distance appear to stand still but nearby trees whiz by as you drive down a road).

All in all, it looks good for this to be a bona fide planet, so from here on out I’ll call it that, but be aware, to be clear, we can’t be completely sure.

Because the planet is so young, it’s still radiating away the heat leftover from its formation. Astronomers used the Very Large Telescope to observe HD 95086 b in the infrared, where it’s brightest; that makes it easier to separate out from the blinding light of its star. From its brightness and color, the astronomers estimate the planet has four to five times the mass of Jupiter, keeping it well within the mass scale of what we call a planet, and also making this the lowest mass planet ever directly seen—the next lowest one is probably about seven times Jupiter’s mass.

HD 95086 b orbits the star at a distance of 56 times the distance of the Earth to the Sun (more than 10 times farther than Jupiter is from the Sun). That’s a minimum distance, assuming a circular orbit, and assuming the orbit is face-on to us. If it’s inclined, perspective shrinks the actual distance from the planet to the star, like a disk held at an angle gets thinner and looks like an ellipse.

This is not at all an Earth-like planet, I’ll note. It’s massive, so it’s almost certainly a gas giant like Jupiter, and it’s hot, probably about 730° C (1350° F) at the tops of its clouds. That’s hot enough to melt tin! It’s cool enough to have water vapor and methane in its atmosphere though. Anyway, it’s three quadrillion kilometers—2,000,000,000,000,000 miles—away. So don’t bother packing your bags.

Still, every planet we can see directly is an important addition to our bag of knowledge. We have many different ways of detecting exoplanets, and each way helps us understand more about them. Direct imaging of an exoplanets is still a very difficult thing to do, because planets are dim, stars bright, and the separation between the two very, very small.

But we’re getting better. The technology is improving, with new and clever ideas coming along that reduce the glare and bring out the faint light of alien worlds. As time goes on, we’ll find more and more of these, discovering ones ever smaller and with lower mass, and even be able to detect their atmospheric constituents. It’s an amazing feat, and one of the triumphs of modern astronomy.

In 2010, a very unusual asteroid was discovered. P/2010 A2 (LINEAR), as it’s named, looked more like a comet: It had a long tail stretching away from it. (Even the name is like a comet’s; the P stands for the “periodic” comet’s orbit.) Observations by Hubble taken a little while later showed it was even weirder: There was a bright dot that was ostensibly the solid part, but it was crisscrossed by streaks that looked as if the object had broken up!

It’s not a comet, though. Follow-up observations showed no gas at all in the tail as you’d expect from an actual comet; all they revealed was dust consistent with chunks about 1 centimeter across (about the size of a six-sided die) or smaller—the crisscross features were due to chunks of material flung off the main body into space. Clearly, this was an asteroid, not a comet. So why does it have a tail?

One possible explanation for this bizarre object is that the rock was hit by another smaller asteroid, an impact that would’ve had the explosive yield of a nuclear weapon, disrupting the asteroid and blasting out thousands of tons of dust. Another possible cause is a subtle process called the YORP effect, where the very gentle pressure of sunlight spun up the asteroid, increasing its rotation until it broke apart.

Observations at the time showed the tail was a few tens of thousands of kilometers long. But new observations taken with the One Degree Imager (ODI) camera on the WIYN telescope show the tail is far longer than first thought: It stretches away from the solid rock by a distance of at least 1 million kilometers, 2 1/2 times the distance from the Earth to the Moon!

The picture taken by the ODI shows just how long the tail is; despite being more than 100 million kilometers away from Earth, the tail is long enough to stretch out of the camera’s field of view.

[Grab the slider with your mouse to scroll between the image and an annotated one; note that this feature doesn’t work on mobile devices, which should display the two images separately.]

The image needs a little explanation. The asteroid—which is small, probably on the order of 100 meters across—is essentially invisible. Multiple exposures keeping the moving asteroid centered blurs out stars, making stubby streaks. The tail is obvious, far longer than the starry smears. A satellite makes a short trail cutting across the image at the upper left as well. The tail actually extends in front of the asteroid a little due to our viewing perspective and is at least 850,000 km long just in this image.

Observations taken over time indicate that whatever event created this tail happened about 3.5 years ago; the tail has been changing with time, giving astronomers a handle on its age. Whatever happened to it happened not long before it was discovered. The fact that the tail is this long is unexpected and will help astronomers understand the asteroid itself as well as the nature of the event that created this display.

Only a handful objects like this have been seen. Some appear to be asteroids that still have ice frozen in them; those tend to be in the outer part of the asteroid belt, far enough from the Sun that water exists as an ice. P/2010 A2 is inside that line, so any water on it is most likely long gone.

In 2007, Comet Holmes had a sudden disruptive event that created a huge expanding shell of dust around it that was visible to the naked eye even though the comet was past the orbit of Mars at the time—I saw it myself, and it was amazing. It’s possible that a smaller rock slammed into it, but it may have simply been a buildup of gas inside the comet bursting out.

We’re still somewhat new at finding objects like this, so we’re still learning about them. We’ve only visited a few comets and asteroids up close, but more space missions are either on their way or being planned for future encounters. These missions will yield huge amounts of knowledge about the leftover debris in our solar system. Asteroids can hit the Earth and cause havoc, they contain vast resources valuable for future crewed space missions, and they hold scientific value as some of the basic and ancient ingredients of the formation of the planets themselves.

Learning more about them is important for any and all of these reasons. Plus? They’re surprising, and that’s always a great first step on the path to scientific understanding.

Alan Friedman is a photographer whose pictures of the Sun frequently grace this blog. (See related posts at the bottom of this article.) They are always unusual and beautiful, but even so, this one threw me for a moment:

Ewwwww. The Sun is moldy!

Alan took this shot on May 15, and it’s actually a combination of two separate pictures of the Sun using two different filters that show two different physical process on our star.

The outside edge was taken using a filter that lets through the light from warm hydrogen gas. This filter, called an H-alpha filter, accentuates the flow of hydrogen gas under the Sun’s strong magnetic field. Plumes of such material erupt from the surface and when seen against the dark of space are called prominences.

For the solar disk, though, he got tricky. He used a filter that lets through light preferentially emitted by calcium atoms in the solar atmosphere. Calcium under the influence of the Sun’s magnetic fields tends to emit this particular flavor of light, so it traces features called plages, where the Sun’s magnetic field is burbling and bubbling around. Plages look like thin webbing or filaments stretching across the solar surface. In sunspots, the magnetic field can be so strong it shuts off this mechanism, so there isn’t as much light emitted by calcium.

So why do the sunspots look bright and the plages dark? Because for just the disk, Alan inverted the image, making it negative! So in the light of calcium, the dark spots look bright and the bright plages look dark. It makes the Sun look like an orange getting eaten up by mold.

If you invert Alan’s image you see more clearly what I was describing above:

Of course, now the hydrogen light from the Sun’s edge is negative, so the prominences look dark. You can’t have everything. But the light emitted by calcium is at about 400 nanometers wavelength, which looks blue to our eye, so this is closer to what it really looks like.

I’m not sure if Alan’s method has scientific use or not; astronomers sometimes use negative images to see fainter objects, since our eyes are better at picking out dark things against a bright background than vice versa. In this case, though, maybe the artistic value is enough.

So here’s an interesting question: Calcium is relatively rare in the solar atmosphere compared to hydrogen. In fact, there are roughly 500,000 hydrogen atoms for every one calcium atom on the Sun. So why is calcium seen so strongly on the Sun? You’d think hydrogen would be a half-million times stronger!

It has to do with the temperature and density of the solar surface. Hydrogen has a single electron around its nucleus. When that electron absorbs energy in the form of light, it jumps to a higher level, and it can only absorb very specific amounts of energy. It’s like climbing a flight of stairs: It takes a certain amount of energy to get you from one step to the next, and if you lack the energy, you can’t go up. (Try going up a half a step and see what happens—nothing.) The same is true in reverse: The electron emits light at very specific energies when it jumps down from one level to the next.

Calcium is similar, but the energy levels are different; some of the steps the electron can make are smaller and take less energy than for hydrogen. The light we see from the Sun depends on these steps the electrons make, and it’s just easier for calcium to emit (or absorb) that light than hydrogen given the conditions near the solar surface. So even though there’s much less of it, it’s way easier for calcium to get itself noticed.

Also, this particular light is emitted by calcium that has lost an electron in its outer shell (each atom normally has 20 electrons, with two in the outer shell). That means it’s ionized and can be heavily influenced by magnetic fields. That’s why it is a good tracer of the plages, where the Sun’s magnetism is the right strength to yank around the ionized calcium atoms.

Calcium is pretty useful in astronomy. It can be used to trace solar magnetic activity, as well such activity in other stars. This particular light from calcium only comes from stars roughly the same temperature as the Sun, so it can be used to gauge stellar temperatures, too.

And one final note. Guess where all the calcium in the Universe comes from? Exploding stars.

What goes around, comes around.

Related Posts:

Seriously Jaw-Dropping Picture of the Sun
The Boiling, Erupting Sun
No Words
Awesomely Blemished Inverted Solar Beauty
Close-Up of a Solar Monster

Amateur astronomers—and I count myself among them; those of us who go out under the night sky and observe it just for the love and joy of it—often discount the Moon. Perhaps worse, and more unfairly, we actively dislike it: Its bright orb glows fiercely, washing out the fainter objects that are already difficult to see.

But the Moon is itself a target of interest and beauty. Every phase reveals new details on its surface, with hills, mountains, crater rims, and sinuous valleys casting shadows and revealing relief.

When the Moon is full, though, the Sun is shining straight down on it from our viewpoint. Shadows disappear, our perception of elevation is erased, and the flat disk looks eerie and more like the alien world it is.

"Amateur" astronomer Fred Locklear, aka zAmb0ni, used his 20 cm (8”) Celestron telescope to create the mosaic of the full Moon of May 25, 2013 at the top of this article, and it’s simply stunning. Mind you, I had to shrink it a lot to get it to fit here. A lot. The original image is 6000 x 6000 pixels, and scanning over it will feel like flying over the Moon’s surface. He created this picture using frames from video he shot through the telescope, taking the best ones to create the mosaic, and then doing some standard processing to clean and sharpen them.

One cool thing about the full Moon is that the angle of sunlight highlights features like ray patterns: collapsed plumes of dust and rock ejected from ancient impacts. This debris lies on Moon’s surface, forming long delicate fingers stretching away from craters. Over vast periods of time, sunlight and micrometeorite impacts darkens the dust, turning it gray like the rest of the surface, so young craters look fresher, brighter, as do their rays. They're easy to spot all over the surface, but the king of them all is Tycho, at the Moon’s southern latitudes:

Even this shot was scaled down to fit here; again you should look at the full-size picture to grasp this. Tycho (the location of the Monolith excavation in the movie “2001”) is such an amazing crater that it’s one of my favorites to observe whenever it’s illuminated, but especially at full Moon. It’s truly a wonderful sight to see.

It’s easy to take for granted things we see all the time, especially the ones that might otherwise interfere with our plans. But sometimes it’s the obstacle itself that should be the goal.

 

Related posts:

Majestic Mountains of the Moon (featuring Tycho)
Hubble Shoots the Moon. Again. (also feat. Tycho)
The Extraordinary Face of the Moon
Side View of the Moon
Pow! ZOOM! To the Moon!
Celestron's Capture the Universe 2010 Astrophoto winners!

Sometimes, the Sun surprises us. Late last night (May 31, 2013), a minor but unexpected magnetic storm from the Sun reached Earth. These usually occur after a decent-sized solar flare or coronal mass ejection, but neither was seen before hand. The event wasn’t big enough to cause any major mishaps (like power outages), but it was powerful enough to create auroral displays across the northern United States.

Brad Goldpaint, whose beautiful photos have been featured here on the blog many times in the past (see Related Posts below), happened to be at Crater Lake last night photographing the Milky Way, when the sky erupted. He got some incredible shots of it, including this one:

Yegads! Aurorae (or the northern/southern lights) are due to atoms and molecules of gas in our atmosphere glowing after getting whacked by the onslaught of subatomic particles from the Sun after a solar storm. They’re commonly green and red, but pink coloring is more rare. That’s due to nitrogen molecules in the upper atmosphere, and is generally weaker than the more dominant green and red. [Note: in the photo you can see the Andromeda Galaxy off to the right, and the wonderful Double Cluster in the middle.]

The lights were seen as far south as Salt Lake City; on Twitter, Michael Ross sent me a picture he took from there that also clearly shows the pink aurorae. That’s about the same latitude as Boulder! As it happens, it was cloudy last night when I poked my head out the window. Oh well.

So my record is still unbroken: I’ve never clearly seen an aurora (many years ago I saw a faint dull red patch near the northern horizon when I lived in Maryland; there was a strong aurora that night farther north, but I’ve never been able to confirm that’s what I saw). So I’m not at all jealous that Brad has not only seen many aurorae, but plenty of pink ones, too! Pink is one of my favorite colors—purple is my absolute favorite, and is also seen sometimes with pink lights—so maybe, just maybe, one day I’ll be favored to witness such a thing in the sky.

If it’s clear tonight, I’ll take a look. You should too. That’s always good advice: Look up! You never know what you might see.

Related Posts

Aurora, In the Pink
Followup: More Pink Aurorae
Shimmering Purple Aurora After a Powerful Solar Storm
Rekindled Flame
The Skies Reflect Our Spinning World

I was reading one my favorite science blogs, It’s OK to Be Smart, and was amazed by a video about something I’ve never seen or even heard of before: Prince Rupert’s Drops. These are tear-drop-shaped glass blobs with long, thin tails, made by dropping molten glass in water. They’re interesting, but when you try to shatter them, they become holy-cow-where-has-this-been-all-my-life amazing.

The video is from the remarkable Smarter Every Day video series. This is one of those rare times I don’t really need to explain anything; the host does a great job taking care of that. Watch the whole thing. It’s truly cool.

[Update (June 1, 2013 at 23:00 UTC): It has been brought to my attention that at about the one minute mark in the video, the host uses the word "pansy" to describe someone else in the video. This word has negative connotations in the gay community; it's been used as a homophobic slur in the past and many in the gay community are offended by it. I was unaware of its use in the video when I posted it; I simply missed it. I certainly don't endorse the use of words that marginalize groups of people, and I apologize for that. I will keep the video up, because its scientific value is high, but also because it's already started a dialogue here (and on the original YouTube page) which can help open up more understanding.]

[Make sure you have it set to the highest resolution.]

How about that? Glass is a fascinating subject, but I literally had no idea about this. So look at that: I learned something, and it’s OK to be smarter every day.

Say hello to my little rocky friend: Asteroid (285263) 1998 QE2 has a moon!

The asteroid pair is currently on a relatively near pass of Earth, sailing by us at a closest approach of just under 6 million kilometers (3.6 million miles) later Friday. Asteroids that get this close are of particular interest to astronomers, because that means we can use radio telescopes to bounce radar off them, which can lead to a better determination of their size, shape, speed, and position.

Using the Goldstone telescope in California, astronomers were surprised to find that 1998 QE2 is actually a binary asteroid, a big rock being orbited by smaller one. Here’s the video of the two (the moon is the bright spot seen moving vertically over time):

Statistically, it’s not shocking that 1998 QE2 has a moon; about 16 percent of near-Earth asteroids bigger than 200 meters across have companions. The primary is about 2.7 kilometers (1.7 miles) across, as previously estimated, and the moon is about 600 meters (2,000 feet) across. More observations are planned over the next few days, including using the Arecibo radio telescope, which will provide higher-resolution data.

Mind you, the radar data is a bit weird. It’s not showing you an actual picture of the asteroid. The vertical axis is showing distance to the asteroid—if there’s a hill you’d see it poke up toward the top, and a crater would be a depression. The horizontal axis, though, is actually the velocity at which the asteroid is spinning. The faster the rock spins, the more smeared out it is left to right; one that doesn’t spin at all would look like a vertical line. I know, it’s weird, but it’s the way this kind of radar observation works.

Not only that, but we’re illuminating it with the radar pulses, so when you look at the picture or video, it’s like the radio telescope is off the top of the frame, shining down on the asteroid. Imagine holding an orange in one hand and a flashlight in the other; you’re illuminating one side, not the whole thing. Radar reflections are strongest from the point on the asteroid directly under the radar beam, so that becomes the bright edge in the image. The reflections tend to get weaker near the edge, so it fades toward the bottom, giving it that odd crescent shape.

The moon looks curiously bright in the radar imagery, but I’m not sure why; I haven’t heard any comments about this yet—that may simply be because it’s small, so we don’t see it fade as much toward its edges like we do in the bigger rock. Think of it like having all its light compressed into fewer pixels, so each pixel is brighter.

From these data we now know that the main asteroid spins about once every fours hours at the most—previously it was thought to have a 5.3-hour spin. That old estimate was based on its light curve—that is, brightness variations as it spins. Imagine a dark ball with a single white spot on it. As it spins, you’d see it get brighter every time the white spot comes into view, and that can be used to peg its rotation. It’s not always 100 percent accurate, though, as it wasn't in this case. There are several dark features on the asteroid that may be craters, but they might also be patches of material that absorb radar so they simply look darker. We should know better soon as more data come down.

The moon spins more slowly—you can see it’s not very smeared out in the radar data. It probably takes a day or so to rotate once, but the actual rate is still not well known.

The very presence of the moon is a good thing. By measuring how long it takes to go around the primary, the mass of the primary can be found using math known for centuries (the more massive the big asteroid, the faster the moon will go around it at a given distance). We also know the size of the primary, so that means we can find its density, and therefore what it’s made of (probably mostly rock). Those numbers should be coming in over the next few days.

And finally, using the radar we get the precise position and velocity of the asteroid over time, and that allows a much better determination of its orbit around the Sun. We know that 1998 QE2 is not a threat to Earth, but it’s still nice to show that more clearly.

Of all the data we’re getting on this asteroid pair, the radar is the most precious because of the treasure trove we get from it. Just by bathing it in radio light and watching for the reflection we get a better orbit for it, we see it’s a binary, and we can determine its mass and even composition… all from millions of kilometers away.

That’s pretty amazing. There’s nothing like going to an asteroid and seeing it up close—and there are plans to do that—but we can learn a lot from the safety of our home planet too. Not bad for a bunch of apes who only recently figured out how to get into space in the first place.

On Friday, May 31, 2013 at 20:59 UTC (4:59 p.m. EDT), the asteroid 1998 QE2 will make its closest approach to Earth. Not that it’s all that close: It will miss us by six million kilometers (3.6 million miles), or 15 times the distance to the Moon. That’s good, because the asteroid is 2.7 kilometers (1.7 miles) across.

To be clear, we're safe from this particular asteroid; this pass is only close in an astronomical sense. It’s still so far that you’ll need a decent telescope just to see it at all (it’ll get to a brightness of about magnitude 10—the faintest star you can see with the naked eye is 50 times brighter), and this is the closest it’ll get to us for literally hundreds of years.

Still, it’s a big rock and close enough that astronomers are taking note. It’s a prime target for radar observations, and the Goldstone observatory will be pinging it during the pass. Those observations should resolve surface features on QE2 just a few meters across. NASA’s JPL put together a short video about all this:

As with any near pass of an asteroid, conspiracy theories abound. Forgive me if I don’t give them any air by linking to them, but I've seen these claims come and go a dozen times in the past. Silliness like NASA is hiding evidence the asteroid will hit us; the asteroid will connect with the Earth electromagnetically and cause storms, and so on ad nauseum. The only things these breathless (and baseless) claims have in common is that they are always wrong, yet they always pop up again the next time an asteroid comes within a few million klicks of us. Either conspiracy theorists have a short memory, or their audience does.

I have to admit, this kind of nonsense is cramping my sense of humor. Given the asteroid’s designation and size, I really want to say it’s titanic. But I’ll refrain.

Anyway, NASA has a bunch of talks, interviews, and other activities about the asteroid planned for today and tomorrow. Instead of getting worked up over nonsense, here’s a chance to learn about the reality of asteroids, what we can discover about them, and what role they play in the understanding of our solar system. I bet you’ll find, as always, that reality is far, far more amazing than fantasy.

I recently got a new camera, a Canon Rebel T4i [affiliate link] for the photo nerds out there. I’ve been testing it out, playing with the lighting and video modes, seeing what works best. I needed to make a short video to get a solid test of how it performs, so I figured, why not have some fun? So here’s the Wine Cork Magic Trick, performed by yours truly [a higher-res version is on YouTube as well]:

Let me note: I filmed this video first, then looked for the music after I had already edited it. I like Kevin MacLeod’s Royalty Free Music, and his song “Bad Ideas” seemed to fit what I needed. When I added the audio track into the video, I couldn’t believe how well it matched the action. Seriously, the way the final couple of seconds played out wasn’t planned at all. So maybe this video really is magic after all.

And knowing how much I had to practice this, I bet you'll think it's magic if you try it for yourself. It helps to wait a while before, um, making the wine corks available, too.

Tip o' the black top hat to Richard Saunders and Alynda Brown for showing me this trick many years ago.

Planetary Resources, Inc.—the company that wants to mine asteroids—has a new project they've just announced: They're crowdfunding a space telescope.

Yup, you read that right. PRI has a Kickstarter page set up to fund a small (20 cm, or 8”) telescope that will orbit the Earth. It will take pictures of our planet from above, and astronomical objects, too. Different funding levels will give people different access to the telescope. In a clever twist, if you back it at the $25 or above level, you can upload a picture of yourself that will be displayed on a small screen, and the satellite will take a picture of your picture with the Earth as a backdrop.  

This is one step of PRI’s overall goal to eventually mine asteroids. The company’s plan is a series of steps leading to that ultimate goal, including launching several small telescopes to observe the Earth and sky, survey the sky to find near-Earth asteroids, create small probes that can visit and study asteroids, and eventually mine them for useful materials. I have a detailed description of their plans from when they first announced them in 2012.

This crowdfunded space telescope, called ARKYD, is a way for them to test out their abilities to launch and use such a satellite. PRI has already invested quite a bit of money into the development of a series of telescopes—mostly to look for asteroids, but this new one has different goals and therefore a different design. While they are still putting their own money into designing and building it, the Kickstarter is a way to get people involved personally. It has a series of astronomical filters on it (for the nerds out there: UV (< 300 nm), B, V, R, [OIII], Hα, 1 μm, and a clear (luminence) filter) which means you can create near-true-color pictures, too. It’s not a huge telescope, and you don’t get vast amounts of time, but it should be fine to get nice shots of bright nebulae and galaxies.

PRI President and Chief Engineer Chris Lewicki explains it in this video:

My personal opinion is that this is a legit effort, and should work pretty well. I like the idea of people using it to observe objects they want—getting something like this in the hands of kids in classrooms will do a huge amount positive outreach. You can donate your time to scientists or classrooms, too.

I’ll be curious to see if some of the claims pan out; for example, they talk about finding asteroids with ARKYD, but given the size and filter choice it’s not optimized for it. The ‘scope should find quite a few rocks, but discovering new ones is a tough game these days. It generally takes big telescopes with lots of time to find previously undiscovered asteroids; most are very faint. But it could find a few, which is enough for PRI’s initial purposes.

The other claims look solid enough. Given the small size and low mass, launching ARKYD isn’t all that expensive, and the running costs can be covered if they get enough money pledged. A million dollars is doable via Kickstarter; as I write this they already have more than $40,000 pledged before the official announcement was even made public (the Kickstarter page went live a bit early to test it out). I know my geeks, and I suspect PRI will meet their goal pretty quickly.

Bottom line: I think this is a good idea, it can work, and if it does it’ll be a great way to get the public excited about space exploration and discovery. The team is solid (I saw a few old friends in the video, and the engineering team is made of lots of ex-NASA folks who have tremendous experience in robotic planetary and space exploration), and the goal is reachable.

I might kick some money their way myself. I know a few cosmic objects I wouldn’t mind observing, and it’s a fun idea. They don’t list a launch date, since that’s difficult to determine so far in advance. But stay tuned; when I find out more I’ll let you know!

Centaurus A (or Cen A to its friends) is a nearby galaxy with a weird history. It’s an elliptical galaxy—a giant cotton ball collection of stars—that was, until recently, two separate galaxies that collided and merged. It has a huge dust lane cutting right across the middle, a sure-fire sign that the galaxy was the result of a cosmic train wreck.

Amateur astronomer Rolf Olsen sent me a note the other day, telling me he had taken an image of Cen A. And it’s not just any image: It’s the result of a shocking 120 hours of total exposure! It’s a jaw-dropping view of this iconic galaxy:

Holy Haleakala!

The detail is amazing, and you really seriously want to embiggen it; I had to shrink it a lot to fit it on the blog. Going over the details at Olsen’s site just amazed me more and more.

First and foremost: He took these images with a 25 cm (10”) telescope that he made himself. That’s incredible. A ‘scope that small is not one you’d think you could get this kind of image with, but persistence pays off. It took a total of 43 nights across February to May of 2013 to pull this picture off.

The features you can see are astonishing. The galaxy has a massive central black hole, and is actively gobbling down matter (which is why it’s called an active galaxy). You can’t see the black hole itself, but blasting away from the black hole at a good fraction of the speed of light are a pair of jets, beams of matter and energy heading in opposite directions (I describe how these form in detail in a post on Herc A, another active galaxy). Olsen’s image easily captures the inner jet on the side of the galaxy facing us:

On the left is Olsen’s shot, and on the right one from a 2.2 meter telescope. Obviously, the bigger ‘scope has far higher resolution, and can see fainter stars and features in the jet, but Olsen’s shot is pretty impressive.

In the big picture you can also see the shells of gas surrounding the galaxy, which are probably remnants of the collision, which sent out vast waves of material like ripples from a rock dropped in a pond. He was also able to identify over 700 globular clusters in his image—those are tight, spherical clusters of stars that orbit most galaxies. The Milky Way has over 150, but Cen A may have ten times as many.

Cen A is pretty close, just 12 million light years away, making it the nearest active galaxy to us, and one of the brightest in the sky. It’s best visible from the southern hemisphere, making it a juicy target for Olsen’s New Zealand location. Still, using a ten-incher to take an image this deep and detailed is a daunting task, so I encourage you to read how he did it. I’ll add that a few years back he contacted me to say he had actually seen the debris disk—the leftover planet-forming material—around the star Beta Pictoris. No amateur had ever done that (it was only discovered in the 1980s!), so I was very skeptical. But his image and methods checked out; it was an incredible acomplishment. It’s clear he is very skilled and extremely dedicated. To say the least.

I can’t even imagine what he’ll try next. But whatever it is, I know it will be worth keeping an eye on his efforts.

I remember a time, many years ago, when I was a lad and at home with my sister. It was a warm early summer day, and I heard something odd outside. I opened my window, and my ears were met with a loud, persistent droning sound. I couldn’t figure out where it was coming from…until I realized it was coming from everywhere.

I ran to my sister’s room and said, “Listen!” and opened her window too. Her eyes got wide, and she said, “What is it?” I smiled and replied, “Cicadas. They’re back.”

She didn’t believe me at first, and I didn’t blame her. It was loud. But that’s what happens when billions upon billions of enormous insects are all simultaneously looking for love.

That was 34 years ago now, two cycles past. The time has come once again for those red-and-black giants to come out of the ground and repeat their ancient pattern. To celebrate this, filmmaker Samuel Orr has created a short time-lapse video filled with stunning photography of cicadas, briefly explaining their weirdly fascinating life cycle.

WARNING: If you find insects icky, some of this may—haha!—bug you.

Orr has a Kickstarter project to fund a full-length documentary on these critters. I for one welcome our new cicada overlords, and would love to see this film made.

Shortly after my sister and I awoke to the cicadas that long-ago day, my best friend Marc and I went out for a bike ride to the local lake. We always took a bike trail through the woods, but this time it was different: Lining the trail on both sides were countless millions of thin, translucent brown shells, like molds of the cicadas’ adult bodies cast aside once they molted. It was incredible. We tried to talk about them as we rode, but it was nearly impossible because the buzzing of the male cicadas was so loud it drowned out our conversation. So instead, we just laughed and soaked it in.

I don’t live on the East Coast anymore, so I’m missing this year’s awakening. And I know a lot of people will complain about the loud, irritating, and uncomfortably large insects. But it’s nature at its most amazing, and I wish I could experience it once again. My next chance will be a long time coming.

It’s no surprise to regular readers I am quite concerned about climate change. My concern on this issue is two-fold: one consists of the actual global consequences of the reality of global warming, and the other is the blatant manipulation of that reality by those who would deny it.

These two issues overlap mightily when it comes to Arctic sea ice. The ice around the North Pole is going away, and it’s doing so with alarming rapidity. I don’t mean the yearly cycle of melt in the summer and freeze in the winter, though that plays into this; I mean the long-term trend of declining amounts of ice. There are two ways to categorize the amount of ice: by measuring the extent (essentially the area of the ocean covered by ice, though in detail it’s a little more complicated) or using volume, which includes the thickness of the ice. Either way, though, the ice is dwindling away. That is a fact.

Of course, facts are malleable things when it comes to the deniosphere. One popular denier claim is that Arctic sea ice extent is higher in recent years than it was in 1989, therefore claims of it melting away are false.

This is so blatantly wrong that it’s hard to believe anyone could make that claim with a straight face. But make it they do, like Lawrence Soloman did in (surprise!) an OpEd in the Financial Post (which, like the Wall Street Journal, is a refuge for denialist claims). Soloman’s silliness is taken apart easily by Tamino on his blog. Harrison Schmitt has made this claim as well. It’s simple cherry picking your data, and a huge no-no when it comes to real science.

When you look at the average, the trend in the ice, it goes down, down, down. Over time, there’s less.

How much less? I was curious about this recently, because most of the graphs I see deal with what scientists call “anomalies”, that is, departures from average. If people average 180 centimeters tall, and you are 182 cm in height, your “height anomaly” is +2 cm. If you were 173 cm tall your height anomaly is -7 cm. Simple, and useful when dealing with some physical effects, but sometimes the emotional impact is lost. If you hear someone has a height anomaly of +15 cm you’d think that was interesting, but if you met them in person you’d see that means they’re really tall.

The same with sea ice. Graphs show us that sea ice is declining over time, but it’s shown as a percentage, or a deviation from some past period. That’s good to give you a grasp of the situation, but doesn’t tell you how much actual ice is left.

So what’s the real loss of ice we’re experience every year?

The answer is: a lot. A whole lot. Even after seeing the numbers, I was taken aback by this graph which shows sea ice extent plotted over time.

The solid black line is the amount of sea ice over the year averaged from 1979 – 2000. The dashed line is the amount in 2012, and the brownish solid line is this year, up to late May. As you can see, we’re right on track to match last year—which was way below average. This plot is from the National Snow and Ice Data Center, and they have an interactive version where you can add or subtract various years. You can see we are headed for serious trouble, and soon. The ten lowest maxima for extent in the satellite record all occurred in the last ten years.

Obviously, Arctic ice grows every winter and melts every summer. In March 2013, the Arctic ice reached its maximum extent, which was the sixth lowest on record (it naturally fluctuates a bit year to year, but the trend is definitely downward). It drops to its minimum extent in September, but on top of that, over time, the minimum amount itself is shrinking.

Look again at the graph, at the bottom of the y-axis. That line is 0, meaning zero ice, essentially nothing but liquid water at the Earth’s north polar regions; that means this graph gives you an absolute scale. Then note that the past year’s minimum was only half the amount of ice we had on average from 1979 – 2000. If you click on previous years to add them to the graph, you’ll see that the past ten years or so have had very low ice minima; these correspond to most of the warmest years on record.

And it gets yet worse. If you look at the volume of sea ice, that drops even faster than the extent. This terrifying video uses a clever graphic to demonstrate just how much sea ice we lose every year.

So the volume of ice is decreasing even faster every year as well; the ice is getting thinner and thinner. This is a very bad sign, as thinner ice melts more easily. No one knows when we’ll have the first ice-free Arctic summer—extrapolating into the future can be difficult—but one thing we can bet on is that it’ll be a lot sooner than the year 2100 as originally predicted just a few years ago. It could be in as little as 30 years. Although some deniers claim this Arctic loss is offset by growth in Antarctic ice, this claim as usual, is simply false.

Of course, oil companies are already planning on exploiting an ice-free Arctic to drill for more oil. The irony is obvious, but there’s also the added point that while oil money is behind a lot of the denial, they themselves are ready to jump on the positive—for them—effects of global warming.

And, no doubt, the deniers will make lots of noise about this, calling me an alarmist and pointing to ever more cherry-picked data and misleadingly plotted numbers. But the fact is the Earth is warming up. That’s melting the ice at both poles, increasing sea levels. We’re still dumping gigatons of carbon dioxide in the air every year, and the amount increases at a steady and measurable level. That CO2 is warming us up.

Stopping the deniers may be as hard as stopping the warming itself. Perhaps once we have satellite images of an ice-free north pole we’ll see a change in public sentiment. It’s a shame that may be what it’ll take. My concern is that by the time that happens, it’ll be too late.

Speaking of sunsets, over the past few days and for the next few as well, the planets Jupiter, Venus, and Mercury can be seen together in the west just after the Sun slips below the edge of the Earth. This is called a conjunction, and you don't need any fancy equipment to see it; just your eyes, and a clear view to the west.

If you pick your spot carefully, the foreground might enhance what you see, though. The brilliant astrophotographer Thierry Legault went to the northwest coast of France, and on May 26, 2013 took this ridiculously beautiful picture:

Mon dieu! That's Mont-Saint-Michel, a tiny island off the French coast. It's a tidal island; the causeway connecting it to the mainland is submerged at high tide and exposed during low tide. A monastery sits upon it, making it look like something out of a fantasy story. I've never been to that part of France, but it's on my list now!

In the sky above and around it you can see Venus (lower right), Mercury (upper right), and mighty Jupiter (to the left). All three are unresolved dots at this magnification, but they may look different sizes because of their varying brightnesses. If the size variation were real, Jupiter would look three times bigger than Venus, and five times bigger than Mercury in the picture! Currently, all three are on the other side of the Sun, making them appear smaller than they can be. Mercury is actually the closest right now, about 170 million kilometers (105 million miles) distant, compared to 250 million km (150 million miles) for Venus and 910 million km (565 million miles) for Jupiter.

Think on that: Jupiter is so flipping big that even though it's nearly four times farther away from us than Venus, it still looks much bigger through a telescope!

Photographer Ken Griggs also had a great view of the conjunction on May 26 in Lehigh Valley, Pennsylvania, and this photo appears to be celebrating it:

I'll note it's actually a composite of two different photos; both had the fireworks and planets in them but added together made the picture even more pleasing.

As the days go on, Jupiter will sink lower to the horizon after sunset as Venus and Mercury climb higher, so this configuration will constantly change. It's best this week, though, so go out and take a look. It's a rare opportunity to watch these three worlds dance together in the sky.

I have just returned home after a few days at the wonderfully fun SpaceFest V, where I met up with old friends and heard fantastic talks by astronomers, astronauts, and space artists. I have a pile of work to catch up on and get ahead of, so for now I'll just leave this here: As we were coming home from the airport, the Sun was setting behind the Rocky Mountains' Longs Peak, so my wife and I stopped to take a few pictures of the breath-taking sight:

Longs Peak is the tallest mountain I can see from home, topping out at about 4350 meters (14,260 feet). Dust and particulates in the air lit the sky up yellow and orange, and provided a backdrop against which the shadows of the mountains themselves could be cast. These are called crepuscular rays, and are one of my favorite sky phenomena. Despite what you see with your own eyes here, the rays are actually parallel. Perspective can be a tricky thing.

I'll note that in America, today is Memorial Day, where we honor those who have fallen fighting for this country. I prefer to expand that to anyone we have lost, especially those who have tried in some way to make the world a better place. Don't forget to thank the ones you still have with you, and remember the ones who are not.