Sky & Telescope news
On July 14th, New Horizons will at long last swing past Pluto, collecting better data on this mysterious dwarf planet than we've ever seen before. But, as Emily Lakdawall relates in our cover story, the spectacular data will take many months to trickle in. In the meantime, if you're up for a challenge, you can have your own look at Pluto, and Ceres too, with our detailed sky charts as your guide. You'll find far more to look at in the sky this summer with Rod Mollise's article on summer sensations: start with the Bug Nebula, move on to the Cat's Eye Cluster, and just keep on going. And when the balmy nights fill with clouds, take refuge in Nick Kanas's fascinating and finely illustrated take on the star atlas frontispieces of old.Feature Articles
Pluto At Last
After a 9½-year flight, NASA's New Horizons spacecraft is making a long-awaited visit to Pluto and its moons.
By Emily Lakdawalla
Planck Upholds Standard Cosmology
The latest analysis of the universe's oldest light provides an exquisite look at the cosmos.
By Camille Carlisle
Celestial Frontispieces of the Golden Age
Astronomy-themed art and allegory reached an early peak as illustrators sought to outdo one another.
By Nick Kanas
The Backyard Sky: Summer
Stretch your observing skills to spot these seasonal sensations.
By Rod Mollise
Done in One
Today's one-shot color cameras can take world-class astrophotos. Here's how to do it.
By Warren Keller
Prepping for Pluto
Thanks to NASA's New Horizons spacecraft, we're about to see Pluto up close for the first time. Here are a few snapshots of the scientists and engineers who'll make it possible.
Follow Nova Sagittarii No. 2
Stay up-to-date with this unpredictable nova's appearance.
Milky Way's Ripples
Find out more about (and see images of) the waves in our galaxy's disk.
Librations and other lunar data for July 2015.
Venus, Jupiter, and Saturn grace the evening, Mars and Mercury the dawn.
By Fred Schaaf
It's Dwarf-Planet Summer
As Dawn and New Horizons watch Ceres and Pluto, you can too.
By Alan MacRobert
Small Sagittarius Star Cloud
The Sagittarius Milky Way is host to dark nebulae and open clusters.
By Sue French
Table of Contents
See what else July's issue has to offer.
Watch as the two brightest planets — Venus and Jupiter — edge closer together and culminate on June 30th with a dramatically close pairing.
This month features a beautiful pairing of planets in the evening sky. Night by night, Venus and Jupiter inch closer together. Late in the month the pairing gets even more dramatic. They’ll look like a brilliant double star in the sky. The performance culminates on June 30th, when Venus and Jupiter are separated by only 0.3°.
Meanwhile, a third bright planet, Saturn, is taking the stage over in the east. Saturn was at opposition, opposite the Sun in the sky, on May 22nd. So throughout June, instead of rising when the Sun sets, it’ll be a little higher above the southeastern horizon at nightfall.
There's lots more to see by eye in the June evening sky. To get a personally guided tour — and to learn the meaning of the star names Zubeneschamali and Zubenelgenubi — download our 7-minute-long stargazing podcast below.
There's no better guide to what's going on in nighttime sky than the June issue of Sky & Telescope magazine.
Dennis di Cicco Welcome to Sky & Telescope’s product videos. Over the past few years, former S&T senior editor Dennis di Cicco has interviewed many manufacturers and vendors of astronomy equipment in an effort to bring their products to life in a way that you will find useful. We hope you enjoy them.
Apogee Imaging Systems — April 2014
Apogee Imaging Systems — October 2012
Apogee Imaging Systems — April 2011
Apogee Imaging Systems — April 2010
Apogee Imaging Systems — April 2009
Astro Haven Enterprises — November 2011
Astro-Physics — April 2013
Astro-Physics — October 2009
ASA Astrosysteme Austria — November 2011
ASA Astrosysteme Austria — October 2009
Celestron — October 2009
Celestron — April 2009
Ceravolo Optical Systems — October 2009
DC3 Dreams — November 2011
DC3 Dreams — October 2009
Explore Scientific — April 2011
Explore Scientific — April 2009
Finger Lakes Instrumentation — April 2014
Finger Lakes Instrumentation — April 2011
iOptron — April 2015
iOptron — April 2014
iOptron — April 2012
iOptron — April 2009
Meade Instruments — April 2012
Meade Instruments — November 2011
Meade Instruments — April 2010
Optec, Inc. — November 2011
PlaneWave Instruments — October 2013
PlaneWave Instruments — November 2011
PlaneWave Instruments — October 2009
PlaneWave Professional Services — October 2013
RSpec — April 2011
Santa Barbara Instrument Group (SBIG) — April 2014
Santa Barbara Instrument Group (SBIG) — April 2012
Santa Barbara Instrument Group (SBIG) — April 2011
Sky-Watcher USA — April 2015
Sky-Watcher USA — April 2014
Software Bisque — April 2015
Southern Stars — April 2013
Stellarvue — April 2014
Tele Vue Optics — April 2014
Researchers using NASA’s Wide-Field Infrared Survey Explorer (WISE) have discovered the most luminous galaxy to date. Dubbed WISE J224607.57-052635.0, this Extremely Luminous Infrared Galaxy (ELIRG) shines brighter in the infrared than 300 trillion suns and has an exceptionally supermassive black hole at its core. The sheer size of this black hole-gargantua is one of a few such entities that leave astronomers scratching their heads as to how in the world (or in this case, the universe) such giants can grow so big so quickly. We still don’t quite know the answer, but astronomers have a few ideas.
One idea involves the collapse of the universe’s earliest stars. Made only of hydrogen, helium, and some other Big Bang leftovers, these stars initially contained no heavier elements. With no way to cool down the heat of gravitational collapse, they were able to grow much bigger than the metal-rich stars of today’s universe. Thus, when these early stars ended their short lives, the black holes they created were easily hundreds of times the mass of the Sun, much bigger than today’s stellar mass black holes. And after collapsing, the black holes grew even bigger by gobbling up nearby matter.
All of this, however, still takes a long time — too long, some astronomers believe, to have built black holes as massive as some of those found within ELIRGs.
Another theory postulates that primordial gas might have seeded biggies like WISE J224607. In this model, instead of a star forming, growing, and collapsing, gas clouds in the early universe collapsed directly into black holes. These black holes would not only be at least 10 times more massive than star-seeded black holes, but they would also have had more time to gobble and grow.
The researchers who discovered WISE J224607 are exploring other properties that might have helped the black hole grow so big so fast, such as chaotic accretion that hid its own radiation. But we’ll have to study it, and other ELIRGs, much more before we can fully understand their founding histories.
See more information on WISE J224607.57-052635.0 in the JPL press release.
As amateur astronomers gathered several weeks ago at the 24th annual Northeast Astronomy Forum, they caught first glimpses of hot new products showcased at one of the world's largest astronomy trade shows.
Now you can too, whether you made it to NEAF or not. Former S&T editor Dennis di Cicco interviewed three vendors about their newest products at the show. Watch these in-depth conversations to find full details on new product lines and featured equipment.Product Videos
Sky-Watcher product specialist Kevin LeGore gives Dennis di Cicco an overview of the company’s latest offering of telescopes, including the new Quattro line of Newtonian astrographs. Also covered are two new large-aperture Maksutov systems, one a Mak Cassegrain and the other a Mak Newtonian, as well as the Sky Watcher line of Dobsonian reflectors.
Dennis di Cicco talks with Stephen Bisque, the founder, president, and CEO of Software Bisque, about the company’s history from its introduction of TheSky planetarium software in the 1980s through its evolution of state-of-the-art robotic telescope mounts. Special attention is given to the latest generation of mounts, including the flagship Paramount ME II, Paramount MX+, and the brand new Paramount MyT.
Observations of white dwarfs in a densely populated globular cluster confirm astronomers’ expectations that stars migrate to a cluster’s outskirts after losing weight.
Gravity has everything to do with the way stars interact with one another, and the stars in globular clusters are no exception. Globular clusters are groups of very old stars bound together in a sphere. They organize their stars by mass, with heavier, slower stars congregated near the middle, and lighter, faster ones at the cluster’s edge.
Dynamical relaxation is the process by which clusters organize themselves in this way, and it is also the process that reorganizes stars when any mass changes occur. Some stars do not have static mass, and when they lose weight, the gravity in the cluster will propel them outward.
White dwarfs are one type of low-mass star that is found in the outer reaches of a cluster. They began as the cores of stars like the Sun. When the stars hit the end of their fusion-powered lives, they shrug off their outer layers to reveal the collapsed, planet-size core at their hearts. The process by which a star reaches this white dwarf stage causes it to lose a large portion of its mass — about 40%—in the form of stellar winds.
Before losing this mass, the star is situated near the center of the cluster alongside other massive objects. But then, after becoming a smaller white dwarf, it migrates to a new position via gravitational interactions with other stars, that is relative to its new weight. This mass-loss process and movement makes white dwarfs a great subject for observing dynamical relaxation, yet until now we haven’t caught this migration in action.
Using Hubble’s Wide Field Camera 3 — which has the ability to catch ultraviolet light that is dispersed by Earth’s atmosphere and therefore invisible to ground-based telescopes — Dr. Jeremy Heyl (University of British Columbia, Canada) and colleagues studied white dwarf stars in the globular cluster 47 Tucanae.
This cluster is a rich agglomeration of stars in the Southern Hemisphere sky and a frequent research target, but it hasn’t been analyzed in this particular way before. Because white dwarfs cool as they age, and because hotter (younger) white dwarfs are brighter in ultraviolet wavelengths than cooler (older) ones, the researchers were able to estimate the ages of the cluster’s stars and identify two major populations of white dwarfs.
One population was a group of relatively new white dwarfs, only a few million years old, and the other a very old, 100 million-year-old group. Heyl and colleagues examined the location of the stars in each age category and found that the younger ones were gathered near the center of the cluster, while the older ones were dispersed at the outer edges.
This result is just what they expected to find.
Since stars expel the most mass in the stage immediately prior to becoming a white dwarf (the so-called asymptotic giant branch, or AGB, stage), it follows that those stars that recently became white dwarfs would still be hanging around the center of the cluster, not having had time to begin their migration outward. Similarly, older stars that had more time as smaller entities should have already arrived at their destinations. This observation confirmed not only the presence of dynamical relaxation, but also the theory that stars do indeed lose most of their mass in their AGB phase.
The team didn’t determine whether the white dwarfs also show signs of dynamical relaxation in their motions, but that will be a good focus for follow-up. For now, the analysis is a nice confirmation of what we thought we knew about the mechanics within globular clusters.
With Arcturus as our touchstone, we set off in a virtual time machine to visit the sky of the distant future.
Bright orange Arcturus twinkles high in the southeastern sky at dusk this week. Its slow climb from the northeastern horizon every March heralds the arrival of spring. Earth's revolution around the Sun ensures that Arcturus follows a familiar path year after year.
But hidden within in its apparent motion across the sky is Arcturus's own intrinsic or proper motion of 2.3″ to the southwest (PA 209°) each year. This very tiny amount amounts to just 1/800 the diameter of the Full Moon. Even over an 80-year lifetime you'd never notice the star's movement with the naked eye. That's why we have telescopes.
Over time, those arcseconds add up. If you were to make a careful drawing or take a photograph of the star when you were 20 years old and then redraw its position say 40 years later, Arcturus would have moved 92″ or about 1/20 the Moon's diameter, a distance obvious even at low magnification. Advice to young readers: get crackin'!
Arcturus stands out among its fellow stars because it's moving rapidly in relation to the Sun as well as perpendicular to the galactic plane in which the Sun revolves. I've included a map showing its gradual drift southward at the breathtaking velocity of 122 km/s (the Sun travels at 30 km/s).
I like to imagine taking an after-dinner stroll with the Greek astronomer Hipparchus, who lived in the 2nd century BC. Among his many accomplishments were the compilation of the first detailed star catalog and the invention of the magnitude system to quantify star brightness. Keen observer that he was, I've no doubt he'd notice something amiss with the outline of Boötes with Arcturus having moved 1.2° southwest since his time.
I've always loved time travel ever since seeing the movie The Time Machine as a kid. Astronomers using telescopes on the ground and in space (the Hipparcos satellite, of course!) have now measured the proper motions of many stars. Incorporated into commonly available software programs like Stellarium, The Sky, and others, they let us see the skies of the past, present, and future with a few clicks of the mouse.
Care to jump in my time machine for a look at what's ahead? I've chosen the year 27,800 AD because that's when precession of the Earth's axis will return Polaris to its seat near the North Celestial Pole. Precession, caused by torque produced by the Sun's and Moon's gravity on Earth's equatorial bulge, causes our spin axis to describe a circle in the sky with a period of about 26,000 years. In 3000 BC it pointed at Thuban in Draco;12,000 years from now Vega will reign as polestar.
Constellations shift shape only slowly but given a precessional kick in the pants, we'd notice striking changes in 26,000 years. More distant stars like Spica will have budged just a little, while Arcturus and others practically leap across the sky.
Overall, much of the sky would still look familiar, but with lots of Dali-esque twisting and stretching. Good examples of slightly mangled groups include Ursa Minor, Bootes, Virgo, and the Big Dipper asterism. Others like Cassiopeia might go unrecognized were it not for it location near figures less altered by time.
Star distances and hence magnitudes will likewise have changed. Arcturus is closest to Earth now but will be farther and fainter in the year 27,800.
I hope your enjoyed our brief foray into the future. Stop back next week, when I'll provide maps and details on finding and tracking two special stars that move so fast, you'll only need a year or two to catch them at their game.
Need to know what the sky looks like right now? The Sky & Telescope planisphere will show you what's up!
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