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Watch Resupply Mission Chase Down the International Space Station This Weekend

2 hours 41 min ago

Watch a cargo mission approach the International Space Station this weekend.

H-IIB rocket

The H-IIB rocket poised to launch HTV-6.

Got a pass of the International Space Station (ISS) this weekend? Watch carefully, and you might just see an additional visitor: the Japanese H-II Transfer Vehicle HTV-6 cargo mission, launching today.

HTV-6 Kounotori ("white stork" in Japanese) launches today at 8:26 a.m. EST / 13:26 UT atop an H-2B rocket from Tanegashima Space Center on the southern tip of Kyushu Island in Japan. Headed toward an orbit matching the ISS at 256 miles (410 kilometers) above the Earth's surface, grapple and capture of the HTV-6 will be broadcast live on NASA TV on Tuesday, December 13th, starting at 4:30 a.m. EST / 9:30 UT. Capture for berthing of HTV-6 to the nadir node of the Harmony module is expected to occur at 6:00 a.m. EST /11:00 UT.

Watch the launch here (launch countdown begins around 59:30 into the video):

What Is HTV-6? HTV-5, as seen from the International Space Station

HTV-5 as seen from the International Space Station (ISS).

HTV-6 carries 5.9 metric tons of cargo, including food, water and experiments for the ISS. Also on the manifest are new lithium ion batteries set to replace the aging nickel-hydride batteries used for power while the ISS is in Earth's shadow. HTV-6 will undock for a destructive reentry in early 2017.

This cargo supply flight comes just over a week after the loss of the Russian Progress-65 mission just six minutes after liftoff from the Baikonur Cosmodrome on December 1st.

Prospects for Spotting HTV-6

HTV-6 launches five minutes behind the ISS on its 90-minute orbit around Earth. After achieving its initial orbit, HTV-6 will need to perform a series of engine burns over the next several days to boost its orbit further and reach the ISS.

If the ISS will be passing overhead this weekend (check for ISS passes for your location here), it's worth watching a few minutes before and after to find the HTV-6 spacecraft along the same course. We spied the last HTV-5 module chasing the ISS through the Florida dawn as a +1-magnitude star-like object back in 2015.

HTV orbit

The "orbital step ladder" HTV takes to reach the ISS.

The closer it gets to grapple and berthing on Tuesday, the closer the HTV-6 will be to the brilliant ISS. ISS passes starting Friday night favor latitudes 40° to 55° north (including the United Kingdom and the northern tier of the contiguous United States and southern Canada) for dusk passes, and 30° to 45° south latitude (including New Zealand and the southern tip of South America) for dawn passes.

Heavens-Above is a great place to find ISS passes for your locale, as is NASA's Spot the Station. All predictions stem from U.S. Joint Space Operations Command (JSpOC), which publishes public Two Line Elements (TLEs) for unclassified missions shortly after launch. Registered users can access TLEs on the Space-Track website. We like to manually check these prior to an ISS pass and plug them in to a nifty satellite tracking application named Orbitron.


An Orbitron screenshot.

Too much work? Follow us on Twitter (we're @Astroguyz) and we'll update sighting prospects for the HTV-6 versus the ISS worldwide post launch.

HTV-6 isn't the only mission that occasionally stalks the ISS. Russian Progress vehicles, the European Space Agency's ATV spacecraft, SpaceX's Dragon and Orbital ATK's Cygnus all make port of calls at the station. The Russian Soyuz spacecraft also make a few flights a year, and are currently the only way crew can reach and depart the ISS. SpaceX's Dragon also provides the only automated down-mass return capability from the ISS, splashing down in the Pacific.

The second stages of these missions also sometimes remain along the path of the ISS for a few days post-launch, although in the case of an H-2B rocket shot, the second stage usually reenters over the Pacific shortly after launch.

Some near-future flights to the ISS to watch out for include: SpaceX's Dragon on CRS-10 (January 22nd), Progress-66P (February 2nd), and Cygnus on OA-7 (March 16th). Dragon launches are particularly dramatic, as they generate four pieces of hardware (Dragon, the Falcon second stage, and the two solar panel covers) often spotted on the first orbital pass.

Don't miss the ISS and friends, crossing a sky near you!

The post Watch Resupply Mission Chase Down the International Space Station This Weekend appeared first on Sky & Telescope.

Categories: Astronomy Headlines

“Library Telescope” Program Takes Off

2 hours 54 min ago

From humble beginnings in 2008, a simple idea — equipping libraries with loaner telescopes — has caught on across the United States.

    game-changer (n):  a person or event that alters the status quo in a significant and permanent way Library telescope with kids

Thanks to an outreach program started in 2008, hundreds of specially modified Orion StarBlast 4.5 telescopes are now available to library patrons across the U.S.
Jennifer Stowbridge

The New Hampshire Astronomical Society is a typical local club, with a few score amateur skywatchers interested in telescopes and observing the night sky. And like pretty much every astronomy club, the NHAS has watched its membership gradually get older and grayer. Attracting a younger crowd has been a tough sell, despite an active outreach program with plenty of star parties and community involvement

Marc Stowbridge

Marc Stowbridge conceived the highly successful library telescope program in 2008.
Ted Blank

Then in late 2008, NHAS member Marc Stowbridge hit upon a novel idea. Why not take the concept of a "loaner telescope," which the NHAS already provided to its members, and extend it to his local library? That would allow its patrons — especially young ones — to check out a portable, user-friendly scope as if it were a book or DVD. So he took a small telescope, modified it a bit to perform well in unfamiliar hands, and donated it to his local library. It was an immediate hit.

So Stowbridge and other members of NHAS's Educational Outreach Committee found two libraries willing to lend telescopes in 2008 and donated another 10 the next year. Word soon spread (apparently librarians share good ideas a lot), and at last count more than 100 had been distributed statewide. Some participating libraries have months-long waiting lists of eager patrons; several have more than one on hand to meet the demand.

Orion's StarBlast 4.5: An Ideal Loaner Scope

Most people imagine a backyard telescope to be a long, skinny refractor sitting atop a spindly tripod. Of course, first-time buyers scoop up millions of these annually. However, Stowbridge and the NHAS team quickly settled on Orion's StarBlast 4.5 as their starting point. (Here's the S&T review of it from 2003.) It's economical, robust, and well built. It boasts quality optics that provide satisfying wide-field views. And it's very newbie-friendly.

Key changes to Orion StarBlast 4.5

Modifications to the beginner-friendly Orion StarBlast 4.5 tabletop reflector include: (1) adding “Can’t Lose Strings” to loose parts; (2) cutting a 2-inch hole in the end cap to reduce the Moon’s brightness; (3) installing an AA-battery pack for the red-dot finder; (4) adding setscrews in the focusing tube; (5) providing an 8-to-24-mm zoom eyepiece; and (6) adding a Sun warning and other stickers to the main tube.
S&T / J. Kelly Beatty

But a just-out-of-the-box StarBlast still needed critical tweaks to endure the bumps and bruises that a loaner scope would likely endure. So the NHAS assembled a "build team" of volunteers to make some modifications. First, they replaced Orion's two standard-issue eyepieces with Celestron's 8-to-24-mm zoom eyepiece, which provides magnifications of 19× to 56×, and they used small, recessed set screws to anchor it firmly into the focusing tube.

Then they replaced the primary mirror's collimation screws — shiny temptations for inexperienced hands — with hard-to-turn locknuts (some clubs cover simply enclose the tube's back end with a plastic cover). And the endurance of the scope's red-dot finder is greatly extended by replacing its button battery with an external battery pack. Attaching "can't lose strings" prevent dust caps from being lost, and cutting a small hole in the main dust cap allows an overly bright Moon to be viewed comfortably.

To enhance each borrower's observing experience, club members affix a Moon map and solar-viewing warning to the tube and include a small pack containing a laminated 4-by-6-inch instruction manual, National Audubon’s pocket guide to the constellations, and a strap-on headlamp equipped with red LEDs.

Click here for details of how to make the suggested modifications.

I attended one of the NHAS "construction parties" last year to see these transformations firsthand. With practice, and with enough volunteers to create optical, mechanical, and electrical "tiger teams," each scope takes less than 2 hours of effort to be ready for placement. An important side benefit is the camaraderie among club members that I witnessed.

An Explosion of Telescopes

The NHAS program might have remained just a quirky success story had it not come to the attention of the Astronomical League. Thanks in part to the League's promotion of the idea among its affiliated societies, and in part to an October 2014 S&T article by League president John Jardine Goss, scores of clubs across the U.S. have started library-telescope programs of their own. Some are modest, with just a few StarBlasts making their debut, while other efforts have proven wildly popular.

One group that's really embraced the library-telescope program is the St. Louis Astronomical Society. SLAS members kicked off their effort in October 2014 (here's the press release), and the requests just kept pouring in. At last count, this club had placed 131 modified StarBasts in libraries in east-central Missouri and west-central Illinois.

Library-telescope modification team

In August 2016, members of the St. Louis Astronomical Society and 11 neighboring clubs spent all day modifying 48 StarBlast telescopes for placement in the region's libraries.
Donald Ficken

Even more impressive is the planning and execution that goes into making the modifications. The club's last work session, back in August, involved 60 volunteers from 12 different organizations. They took over a branch of the St. Louis County library to upgrade 48 StarBlasts during a 7½-hour frenzy of drilling, wiring, adjusting, and packaging. To get a sense of this mass-production telescope modification, check out the club's photo gallery from last August and two sets of photos (here and here) from the previous "build" in March 2016.

Even with discounts from Orion and Celestron, the cost per telescope package totals about $325. Some clubs (or individual members) choose to donate some telescopes outright, especially when introducing the program, but in most cases the libraries themselves pay — often in concert with contributions from "Friends of the Library" groups or local businesses.

The League is also active in spreading the program into new cities and towns. For the past two years, it has given away 10 telescope-eyepiece "startup kits" at its annual meeting. "This program is due to the vision and generosity of the Horkheimer Charitable Fund, Orion Telescopes, and Celestron," notes League president John Goss. "Without their support, we couldn't offer this program."

Making a Difference Orion StarBlast 4.5 in a library

This user-friendly tabletop telescope might be ready and waiting at a library near you.
S&T / J. Kelly Beatty

Library telescopes are certainly increasing interest in amateur astronomy. According to Stowbridge, a typical borrower is an adult 30 to 40 years old with school-age children. He estimates that, on average six people use a telescope each time it's checked out.

But is the effort starting to draw more young people into astronomy? Solid stats are hard to come by, and in many regions the lending program is just getting started. Some librarians are intimidated or fear the scope will get damaged. Others worry about people looking at the Sun (no solar filter is provided). And some clubs have been reluctant to take on the commitment of time and resources.

However, the usual response ranges from positive to wildly enthusiastic. "What I've seen is that when one library has success with the scope, other branches soon want one too," Goss notes. So, for now, perhaps just getting more people to enjoy views of the Moon and planets through a decent telescope is reward enough.

Is your club participating in a library-telescope program, or have you used one of these specially-modified scopes? If so, add a comment below to let me know about your experiences.

The post “Library Telescope” Program Takes Off appeared first on Sky & Telescope.

Categories: Astronomy Headlines

The Passing of John Glenn

Thu, 12/08/2016 - 15:01
John Glenn, 1921–2016

John Glenn, 1921–2016

Do you remember? I do.

I was a starry-eyed 10-year-old watching on black-and-white TV as John Glenn became the first American to orbit Earth, in February 1962. Yes, the Soviet Union's Yuri Gagarin had done it first. Yes, Alan Shepherd and Gus Grissom had already made brief pop-up-and-fall-back flights from Cape Canaveral to become the first Americans in space. But for me, Glenn's three orbits made the Space Age seem like a real, permanent thing. The stars would be our destination. In my lifetime.

Well. . . .

In 1998, at age 77, Glenn again returned to low-Earth orbit, basically repeating his first flight. Yes, the space shuttle Discovery was a bigger and better vehicle, and he was no longer alone, and he stayed up much longer and lent himself to experiments in zero-g geriatric science. But the stars our destination? In the 1960s our society had seemed to be rocketing upward in so many great and confident ways.

This afternoon Glenn passed away at age 95. You can read full obituaries all over the news. But I can't help but feel that something else has passed.

And no human has been beyond low Earth orbit since 1972.

—Alan MacRobert

The post The Passing of John Glenn appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Bright Geminid Meteor

Thu, 12/08/2016 - 14:48

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Categories: Astronomy Headlines

Veil Nebula – Ha and OSC

Thu, 12/08/2016 - 13:36

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Categories: Astronomy Headlines

Horsehead Nebula – winter skies

Thu, 12/08/2016 - 13:34
Categories: Astronomy Headlines

Amazing Views of Saturn’s ‘Polar Hexagon’

Thu, 12/08/2016 - 08:11

NASA's Cassini spacecraft delivers stunning views from its new orbital perch.

Cassini final orbits

Ring Grazing Orbits (grey) versus Grand Finale Orbits (blue) and Cassini's final plunge (orange).

Welcome to the planet Saturn as you've never seen it before. NASA's Cassini spacecraft completed its first periapsis (closest approach) pass of this new phase of its mission phase. It crossed the plane of Saturn's rings this past Sunday at 8:09 a.m. EST / 13:09 UT. The passage was 57,000 miles (91,000 kilometers) from Saturn's cloud tops and just 6,800 miles (11,000 kilometers) from the center of Saturn's tenuous outer F ring.

“It's taken years of planning, but now that we're finally here, the whole Cassini team is excited to begin studying the data that come from these ring-grazing orbits,” says Cassini project scientist Linda Spilker (Jet Propulsion Laboratory) in a recent press release. “This is a remarkable time in what's already been a thrilling journey.”

The new orbit is part of Cassini's penultimate Ring Grazing Orbits mission. Cassini will perform 20 ring grazing orbits in all, with the next one coming right up on Sunday, December 11th. Cassini also burned its main engine one final time for six seconds during the ring plane crossing.

Moonlet Madness to Come Tethys

A gibbous Tethys, imaged by Cassini on December 4th.
NASA / JPL-Caltech / Space Science Institute

We've already seen some amazing new images, mostly from Cassini's pass over the north pole of Saturn about two days prior to its closest approach. Cassini also passed Tethys on December 4th, giving us more great views of the battered world.

This first ring-plane crossing was dedicated to the final main engine burn and radio occultation experiments, which aim to make accurate measurements of the overall density and mass of Saturn's ring system. Expect more views to come on successive ring-plane passes of the mysterious propeller systems embedded in the rings, as well as views of Saturn's inner moons.

Saturn's Polar Hexagon

The highlight of this first pass was new close-up views of Saturn's mysterious polar hexagon. First spied by Voyagers 1 and 2 in 1981 and 1982, this strange feature gracing Saturn's northern polar region is as beautiful for its symmetry as it is perplexing. The images below were taken using Cassini's wide-angle camera from a distance of 400,000 miles (640,000 kilometers) about 1.6 times the Earth-Moon distance, revealing features about 95 miles (153 kilometers) across per pixel. Image filters covering the violet (420 nanometers) through near-infrared (939 nanometers) spectrum penetrate and reveal the structure of the hexagon through successive cloud layers.

Saturn Hexagon

A collage of Saturn's north polar hexagon as seen by Cassini on December 2nd, in (clockwise, from top left) violet, red, near-infrared, and infrared.
NASA / JPL-Caltech / Space Science Institute

Located at latitude 78 degrees north, the polar hexagon features six sides, each extending about 8,600 miles (13,800 kilometers), longer than the Earth is wide. One leading theory proposed by researchers at Oxford University in 2010 is that the strange hexagonal shape results from a steep latitudinal wind gradient at high latitudes. Saturn rotates once every 10 hours and 33 minutes. Fluid dynamics studies carried out on gas-filled spheres have also managed to produce hexagonal, triangular and even octagonal features. Clearly, something unique is going on here. How long-lived is the polar hexagon? Why don't we see such an enigmatic feature on other gas and ice giants, or even on the southern pole of Saturn?

Saturn's "Hexagon"

This colorful view from NASA's Cassini mission is the highest-resolution view of the unique six-sided jet stream at Saturn's north pole. For more information on this image visit NASA's Photojournal webpage.
NASA / JPL-Caltech / SSI / Hampton University

Of course, there's a lot more to come. As we've mentioned on these pages, a final close pass by Saturn's giant shrouded moon Titan on April 22nd of next year will set Cassini up for its final 22 passes during its Grand Finale Orbits phase of the mission, plunging the spacecraft through the 1,500 mile-wide (2,400 kilometers) gap between the innermost rings and Saturn's cloud tops starting next year on April 26th.

This will also put Cassini on course for its final demise next year, with a fiery plunge into Saturn's atmosphere on September 15th, a protective measure to avoid potential future contamination of Saturn's moons.

Enjoy these final views over the next year of one of the most exotic and photogenic planets in the solar system.

The post Amazing Views of Saturn’s ‘Polar Hexagon’ appeared first on Sky & Telescope.

Categories: Astronomy Headlines

IAU Names Asteroid for Sky & Telescope Contributing Editor Fred Schaaf

Thu, 12/08/2016 - 05:48

The International Astronomical Union has named an asteroid for Fred Schaaf, longtime Sky & Telescope contributing editor.

Finder Chart asteroid Fredschaaf

You'll need 12 inches of aperture or more to track down the 17.3-magnitude asteroid 7065 Fredschaaf, but this is the perfect time of year to do it. Click on the image for a printable finder chart.

The International Astronomical Union has named asteroid 7065 Fredschaaf (1992 PU2) in honor of Sky & Telescope Contributing Editor Fred Schaaf. As the award announcement indicates, Schaaf has spent a lifetime interpreting the night (and daytime) sky for the public. His monthly columns for S&T have introduced countless readers to the simple joy of locating a planet, bright star, or constellation.

In addition to writing for S&T and teaching astronomy at Rowan University and Rowan College, Schaaf has authored more than a dozen books covering naked-eye and telescopic observing, comets, planetary science, and star lore. Since March 1976, he has written a regular astronomy column for the Atlantic City Press newspaper. His first formal contribution to S&T can be read in the Stars & Planets column in the January 1993 issue, but his interest and expertise in astronomy actually hit the pages of the magazine long before that: his daytime naked-eye sightings of Jupiter were described in the December 1976 Observers’ Notebook, and his first letter to the editor, reporting on naked-eye observations of Callisto and Ganymede, was published in the August 1977 issue.

Schaaf’s voice has rung true throughout the years, adjusting to changes in the magazine's format while consistently providing informative, imaginative takes on the sky. In addition to his regular Stars & Planet column, Schaaf has written about atmospheric sky phenomena and naked-eye observing  under the headings "The Near Sky," "Light Pollution," and "The Eye and I" in our Celestial Calendar. His columns addressing the increasingly important topic of light pollution and dark-sky activism are perhaps the most notable of these early S&T contributions. In the 1990s, Schaaf took this topic from the pages of our magazine to the state legislature, authoring the New Jersey state bill that established a temporary New Jersey Light Pollution Study Commission. Schaaf served on the commission, which produced a 12-point recommendation list for minimizing light pollution across the state.

Schaaf’s Stars & Planets column has sported a few different looks and titles over the years, and in May 2004 took on the format that you’ll find in the magazine today. He provides a monthly tour of the most important sky sights in Sun, Moon & Planets, a column popular with novice and expert observers alike. He also offers a more poetic look at the sky in his Under the Stars column (recently renamed from Northern Hemisphere’s Sky). Mythology, science, wonder — all of these regularly combine for a compelling read.

Orbital Map Fredschaaf, named for S&T contributing editor Fred Schaaf

This diagram shows the approximate orbit of asteroid 7065 Fredschaaf for the current epoch. The yellow-blue line indicates where the asteroid’s orbital plane is above (yellow) or below (blue) the ecliptic plane. The solid colors represent the orbits of the planets: Mercury (burnt orange); Venus (gray); Earth (light blue); Mars (red); Jupiter (orange); Saturn (taupe). The white dots indicate the approximate positions of the planets and asteroid (not to scale) for the current dates. An updated orbital plot is available from the IAU Minor Planet Center. Click for a larger version of the diagram.

Asteroid 7065 Fredschaaf, discovered at Palomar Observatory on August 2, 1992 by Henry E. Holt,  is in good company as it journeys through the solar system. It joins the list of several other Sky & Telescope-inspired space rocks such as 2157 Ashbrook, 3031 Houston, 3243 Skytel, 3706 Sinnott, 3841 Dicicco, 3819 Robinson, 4726 Federer, 7116 Mentall, 7228 MacGillivray, 9983 Rickfienberg, 10373 Macrobert, and 2925 Beatty.

It’s not hyperbole to say that S&T readers adore Schaaf’s columns, and we thought it was important to share not just the news that the IAU has recognized his service to astronomy, but to publicly express our gratitude for his work. Fred Schaaf represents the best of amateur astronomy — he shares his knowledge, inspires new observers, and reminds us of all the reasons we have to go outside and look up. Congratulations and clear skies!

The post IAU Names Asteroid for Sky & Telescope Contributing Editor Fred Schaaf appeared first on Sky & Telescope.

Categories: Astronomy Headlines

The horse in the belt

Wed, 12/07/2016 - 18:02

The post The horse in the belt appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Does This Neutron Star Confirm an 80-Year-Old Quantum Prediction?

Wed, 12/07/2016 - 14:15

Scientists have been looking for decades to confirm a weird quantum effect first predicted in 1936. Have they finally found hard evidence for it?

Measuring the quantum effect of vacuum birefringence

This artist’s view shows how the light coming from the surface of a neutron star with a powerful magnetic field (left) becomes linearly polarized as it travels through the vacuum of space close to the star on its way to the observer on Earth (right). The magnetic and electric field directions of the light rays are shown by the red and blue lines, respectively. Model simulations by Roberto Taverna (University of Padua, Italy) and Denis Gonzalez Caniulef (UCL / MSSL, UK) show how these fields align along a preferred direction as the light passes through the empty but magnetized region around the neutron star. As the fields become aligned the light becomes polarized, and this polarization can be detected by sensitive instruments on Earth.
ESO / L. Calçada

Observations of a neutron star 300 light-years away show evidence for the existence of virtual subatomic particles that pop into and out of existence, argues an international team of scientists. The find would validate a prediction made 80 years ago by a fundamental quantum theory that describes the weird world of very small particles. But not everybody is convinced that the scientists have found a smoking gun.

When Paul Dirac penned the equations of quantum electrodynamics (QED), he was formulating a fundamental theory of physics that underlies our understanding of subatomic particles. The theory mathematically — and very successfully — describes both how light interacts with matter and how charged particles interact with one another.

Two consequences of QED quickly became apparent. The first, in 1928, was the prediction that every particle has an antimatter partner — a particle with the same mass but opposite charge. Physicist Carl Anderson discovered the electron’s particle, called the positron, four years later, a Nobel-worthy accomplishment.

A second implication of QED is that the vacuum of space itself could be teeming with temporary particles. Due to the inherent uncertainty of the fluctuating quantum world, subatomic particles should occasionally pop into existence with their antimatter partners, then promptly annihilate each other.  In 1936, physicists reached the conclusion that these so-called virtual particles, each only in existence for a tiny fraction of a second, could have real, measurable effects on light, twisting its polarization in the same way that liquid crystals do in LCD displays. This quantum effect is known as vacuum birefringence.

Although the existence of vacuum birefringence has proven difficult to directly confirm, physicists generally accept that it’s real. “Let’s say [vacuum birefringence] isn’t there,” says Jeremy Heyl (University of British Columbia, Canada). “Essentially you’d have to remake everything, because it’s a very basic consequence of QED.”

Neutron Stars as Cosmic Laboratories Wide-field view of neutron star RX J1856.5-3754

This wide field image shows the sky around the very faint neutron star RX J1856.5-3754 in the southern constellation of Corona Australis.ESO / Digitized Sky Survey 2; Acknowledgement: Davide De Martin

Directly measuring vacuum birefringence requires an incredibly strong magnetic field and sensitivity that’s currently impossible in the lab. But Nature has provided its own cosmic laboratory in the form of neutron stars. These crushed stellar remnants carry powerful magnetic fields, enhancing the effect of vacuum birefringence to measurable levels.

So Roberto Mignani (National Institute of Astrophysics in Milan, Italy, and University of Zielona Góra, Poland) and colleagues used the Very Large Telescope in Chile to observe the bright, nearby neutron star RX J1856.5-3754.

This neutron star is essentially a naked ember, its hot surface glowing. The star’s strong magnetic field polarizes this light, but because the star is only a pinprick in our skies, by the time the combined radiation arrives at Earth, those polarizations cancel out. The neutron star’s light ought to be 0% polarized.

Close-up view of neutron star RX J1856.5-3754

Composite photo of the sky field around the lonely neutron star RX J1856.5-3754 and the related cone-shaped nebula. The neutron star is exactly in the center of the image. The trail of an asteroid is seen in the field with intermittent blue, green and red colors.

Instead, what Mignani and colleagues observed was light polarized somewhere between 11% and 21% — fairly high.

The amount of polarization is high enough, in fact, to suggest vacuum birefringence is responsible, the authors say in the February 11th Monthly Notices of the Royal Astronomical Society. Heyl agrees.

But, as George Pavlov (Penn State) points out, it’s not an open-and-shut case. We don’t know how the neutron star is oriented, relative to Earth — whether it’s rotating edge-on to our line of sight or pointing just one of its poles straight at us*. That orientation will determine if the radiation’s original (non-birefringence) polarization cancels perfectly. If we’re gazing directly at the neutron star’s spinning pole, we’d see light from only one hemisphere and polarization up to 20% would be possible, even without the additional effects of birefringence, he cautions.

“The degree of polarization measured by the authors . . . is rather high indeed,” Pavlov says, and he agrees that it’s consistent with the QED effect. “But it is not a proof that they’ve discovered vacuum birefringence observationally, because such a high degree of polarization could be reached without vacuum birefringence.”

To Higher Energies

The real smoking gun for vacuum birefringence will likely come from missions looking at the polarization of X-rays rather than visible light. A neutron star’s surface is so hot that, while it does emit some visible light, most of its light is emitted at X-ray energies. So while vacuum birefringence does affect the polarization of visible light, it’ll affect X-rays a whole lot more.

It’s quite possible that an X-ray polarimeter may launch in the next few years. There are three mission concepts currently under study: the European Space Agency’s X-ray Imaging Polarimetry Explorer (XIPE), NASA’s Imaging X-ray Polarimeter Explorer (IXPE, and yes it really is almost the same acronym), and another NASA concept called Polarimetry of Relativistic X-ray Sources (PRAXYS). If any of these missions is selected, it’ll launch early in the next decade.

“We’ll immediately verify this QED result that [Mignani and colleagues] see in the optical,” Heyl predicts, “but on top of that we can use the measured polarizations now to probe the structure of the magnetic field in detail.” The effect could be used not only to explore neutron star surfaces in detail, but also the environments around black holes.

* Fun fact: A neutron star’s strong magnetic field bends light radiating from its surface. So when you look at a neutron star, you see more than a full hemisphere at a time — you also see some light from surfaces pointed away from you.

The post Does This Neutron Star Confirm an 80-Year-Old Quantum Prediction? appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Not-So-Clumpy Dark Matter Poses Cosmological Challenge

Wed, 12/07/2016 - 12:21

Astronomers analyzing a new sky survey have found that the distribution of dark matter in the modern universe is smoother than predicted from observations of a far younger universe.

KIDS Dark Matter Map

Analysis of weak gravitational lensing produced this map of dark matter in a region surveyed by the Kilo-Degree Survey.
Kilo—Degree Survey Collaboration / H. Hildebrandt & B. Giblin / ESO

The large-scale distribution of dark matter in the universe is less clumpy than expected. That surprising conclusion is based on a thorough statistical analysis of the shapes of some 15 million remote galaxies.

Galaxy images are ever so slightly distorted by the gravity of intervening matter — a phenomenon known as weak gravitational lensing (see my article in Sky & Telescope’s September issue). But the international Kilo-Degree Survey (KIDS), which studies this so-called cosmic shear, finds an effect that’s about 10% smaller than predicted by the standard cosmological model.

“If the tension […] persists […], modification of the current concordance model will become necessary,” according to the KIDS team in an upcoming issue of Monthly Notices of the Royal Astronomical Society.

Mapping the (Dark) Cosmic Web

Current wisdom says that the newborn universe was pretty homogenous, as evidenced by the cosmic microwave background (CMB). The Big Bang’s afterglow shows only minute temperature variations across the sky, which means that density varied only minutely as well. But starting from these tiny fluctuations, dark matter clumped over time into a huge 3D cobweb of filaments and sheets. Gravity then drew in ordinary matter, which coalesced into superclusters, clusters, and individual galaxies.

Matter in the threads of this intergalactic cosmic web represents about 25% of all matter in the universe, according to Massimo Viola (Leiden Observatory, The Netherlands), who led the new study together with Hendrik Hildebrandt (Argelander Institute for Astronomy, Germany).

The only way to map this mostly dark cobweb is by studying the very subtle gravitational fingerprint it leaves on the shapes of background galaxies. KIDS, carried out with the European Southern Observatory’s 2.6-meter VLT Survey Telescope at Cerro Paranal in Chile, is one of three ongoing, large cosmic shear surveys. So far, it has mapped five areas totaling 450 square degrees (we’d need some 2,200 full moons to cover the same area on the sky).

The other two large cosmic shear surveys — the Dark Energy Survey (DES) at the 4-meter Blanco telescope at the Cerro Tololo Inter-American Observatory, also in Chile, and the Hyper Suprime-Cam (HSC) survey on the Japanese 8.2-meter Subaru telescope at Mauna Kea, Hawai‘i — haven’t published definitive results on this topic so far, though the DES did release analysis of preliminary "science verification" data that's roughly consistent with the KIDS result.

Based on observations by the European Space Agency’s Planck mission, cosmologists had expected dark matter to be fairly clumpy on the largest scales. Planck precisely mapped the CMB’s temperature fluctuations, then astronomers combined that information with what we know about the universe’s expansion history — along with some assumptions about the gravitational properties of dark matter — to yield a prediction of the current dark matter distribution. But the distribution KIDS found is smoother than predicted. The apparent discrepancy poses a challenge for astronomers to explain.

Kilo-Degree Survey, Dark Energy Survey, and Hyper Suprime Cam Survey

The Kilo-Degree Survey, Dark Energy Survey, and Hyper Suprime Cam are all tracing weak gravitational lensing to map the universe's dark matter. The KIDS result is only the first of what's to come. This graphic first appeared in the September 2016 issue of Sky & Telescope. (Click for larger image.)

Smooth Dark Matter Causes Tension

According to KIDS Principal Investigator Koen Kuijken (Leiden Observatory, The Netherlands), earlier cosmic shear observations by smaller and shallower survey programs already hinted at a smoother-than-expected dark matter distribution.

“Maybe the role of dark energy in the expansion history of the universe is different from what is generally assumed,” he says. “Or dark matter has different properties than popular cold dark matter models predict. It may even be the case that gravity behaves differently at the largest cosmic scales.”

Kuijken is confident that theorists will soon come up with alternative models to explain the latest observations.

The post Not-So-Clumpy Dark Matter Poses Cosmological Challenge appeared first on Sky & Telescope.

Categories: Astronomy Headlines

Supermoon and Geminids Duke it Out

Wed, 12/07/2016 - 07:02

In a spectacular case of bad timing, the full Moon coincides with the annual Geminid meteor shower. Don't feel put out. There's still something for everyone, including a consolation prize.

Geminid radiant

Although they can appear anywhere in the night sky, Geminid meteors appear to radiate from the constellation Gemini, which is well above the horizon by late evening.
Sky & Telescope

A supermoon is a good thing. So is a rich meteor shower. But the two together? Maybe not so good. But that's exactly what will happen on the night of December 13–14 when the Moon reaches full phase at 7:06 p.m. Eastern time just hours before the peak of the annual Geminid meteor shower.

The brilliant Cold Moon, the third of this year's three supermoons, will flood the sky with light all night long and slash the number of Geminids visible from around 120 per hour to more like a dozen per. Shower members, which can appear anywhere in the sky, all trace their paths back to a radiant point near the star Castor in Gemini, the constellation that lends its name to the famous downpour.

Is a dozen an hour worth it? You bet. The Geminids are one of the most consistent and richest showers of the year. Fireballs are common. It's also one of the few showers that's active during mid-evening because the radiant is already well up in the eastern sky by 10–10:30 p.m. local time. If you don't want to set the alarm for a chilly 2–4:00 a.m. session, when Gemini reaches its greatest altitude in the southern sky, you can get a passably good look at the shower before bedtime.

Geminid Fireball Flashpoint

A Geminid fireball blazes over Meyers Creek Beach along the south Oregon coast on December 14, 2015. We can only be patient — next year, the shower peaks with the Moon a waning crescent.

Invite a friend over or take your kids out for a look. Just make sure everyone's dressed warmly and preferably stretched out on lounge chairs under sleeping bags or warm blankets. Or fire up the hot tub, a favorite hangout for shower watching. Face east or north before midnight and try to avoid looking at the Moon to preserve whatever night vision you can muster.

Stacking up firepower

The Perseids (PER) and Geminids (GEM) are tops when it comes to producing fireballs, giving observers hope for a reasonably good shower despite moonlight this year. The data was gathered using NASA's network of all-sky cameras. Fireballs numbers are shown from 2008 through mid-2013. The average peak magnitude for a Perseid fireball was –2.7; for the Geminids, –2. 

After midnight and before dawn, face south or west. Geminids are one of the few showers that don't originate from dust strewn by a comet. Instead, the stream's parent body is the asteroid 3200 Phaethon (FAY-eh-thon). Sometimes referred to as a "rock comet," Phaethon is a rare asteroidal object that primarily ejects fragments of rock instead of water vapor, gases and dust when heated by the Sun the way comets do.

Trails of dust have occasionally been observed departing Phaethon, seeding its orbit with future Geminids. Each year in mid-December, the Earth passes through the debris, which smacks into the atmosphere at 80,000 miles per hour (129,000 km/hr). Each entering particle's great speed briefly sets the air aglow to create a titillating meteor flash. Because asteroidal material can penetrate the atmosphere more deeply than comet dust, Geminids produce longer streaks than some showers.

Super-est Moon of the Year

Last month's supermoon, the closest until 2034, captured moments after rising over Lake Superior on November 13, 2016. Refraction causes its flattened shape. December's supermoon will be about 1,950 miles farther from Earth than November's.
Bob King

Of course it will be hard to ignore the Moon that night. And you shouldn't. If we define a supermoon as a full Moon that occurs within 90% of its closest distance to Earth, December's Moon makes the cut, even if it's the most distant of the year's supermoon trio. Second place goes to the October Hunter's Moon and first to the Beaver Moon on November 14, the closest supermoon since 1948.

The December Moon will glare from eastern Taurus near the Gemini border and climb even higher in the sky than last month's, beaming down with enough intensity to render some aspects of the landscape in color, such as signage, trees, and even bright clothing.

Moon Hits a Bullseye!

Observers located within the broad swath defined in white will see the Moon occult Aldebaran on the night of December 12–13. Click the map for a complete list of disappearance and reappearance times for many cities. 
Occult 4.2

If you're still feeling a sense of disappointment at seeing the Geminids pared back, there's a consolation prize. The night before the great clash, the waxing Moon will hit the bullseye — literally — when it occults the star Aldebaran in Taurus. On the evening of December 12th across the Americas (early morning of the 13th for Western Europe), you can use binoculars or a telescope to watch the Moon cover and then uncover the bright star.

What To Expect

Left: A simulation of Aldebaran and the Moon 2 minutes before immersion as viewed from St. Louis on December 12th. Right: On December 23, 2015, a similar waxing gibbous Moon approached and occulted Aldebaran.
Stellarium (left) / Gianluca Masi

An example is shown above; click here for times for more than 1,100 U.S., Canadian, and European cities. Because the listed times are in UT, remember to subtract 4 hours to convert to Eastern Standard, 5 for Central, 6 for Mountain, and 7 for Pacific.

My location has been under clouds for so many nights, I can't wait to see any or all of these wonderful events. Moonlight, meteors, and a disappearing star — sounds positively festive!

The post Supermoon and Geminids Duke it Out appeared first on Sky & Telescope.

Categories: Astronomy Headlines

M78 in Orion

Tue, 12/06/2016 - 19:33

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Tue, 12/06/2016 - 17:12

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M42 – 8° sessão.

Tue, 12/06/2016 - 10:05

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Heart of Rosette nebula

Tue, 12/06/2016 - 08:10

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