With the American Astronomical Society getting ready to convene its 217th meeting in Seattle on the 9th, it seems fitting to talk about one of the most splendid 'nearby' stellar objects, the Andromeda Galaxy, otherwise known as M31. Edwin Hubble was the first astronomer to resolve individual stars in the galaxy, but working with Milton Humason, he did something even more significant, studying Cepheid variable stars inside it whose brightness varies in a regular pattern that indicates their absolute magnitude. These 'standard candles' made it possible to find M31's distance, which Hubble showed was much greater than that of any stars in the Milky Way. We were learning in Hubble's day that the 'spiral nebulae' once thought to be part of our own galaxy were distant 'island universes' in their own right, a vast expansion of the size of the cosmos as humans understood it. M31 is the closest spiral galaxy to ours at roughly 2.5 million light years, offering up a spectacular view of as many...

A new image from WISE is always of interest, given our hopes that the Wide-field Infrared Survey Explorer will help us understand the distribution of nearby brown dwarfs. This image of the Triangulum Galaxy (M33) is at the other end of WISE's charter, which covers objects both near and inconceivably remote. But it's too gorgeous not to run, and it demonstrates how effective the four infrared detectors aboard the spacecraft are at pushing into this region of the electromagnetic spectrum with greater sensitivity than ever before. Here, the blue and cyan colors represent infrared at wavelengths of 3.4 and 4.6 microns -- this is largely starlight. The green and red show light at 12 and 22 microns, most of which is light emitted from warm dust. Image: One of our closest neighboring galaxies, Messier 33. Also named the Triangulum Galaxy (after the constellation it's found in), M33 is one of largest members in our small neighborhood of galaxies -- the Local Group. The Local Group consists...

Start with Buzz Aldrin's footprint. Neil Armstrong took the iconic photo that ran around the world -- it wasn't the first footprint on the Moon because neither man took a photo of that, but Aldrin's ridged bootprint will suffice. Blow the footprint up to full size and it fits neatly across two pages in Richard Gott and Robert Vanderbei's new book Sizing Up the Universe (National Geographic, 2010). It's emblematic of Apollo, of our aspirations and, perhaps, of hopes once again deferred. But Gott and Vanderbei aren't making points about Apollo. They're up to bigger things, much bigger things. Blow the scale up so that you have a view a thousand times larger than the photo of the bootprint and you can now see an entire asteroid (Itokawa) on the two-page spread, along with a Space Shuttle, the International Space Station and the Hubble Space Telescope. And now things really take off. Blow the scale up to 1:1 million and we can fit a good portion of the arc of Enceladus onto the pages,...

A gravitational wave is a ripple in spacetime, one that follows naturally from the theory of general relativity -- Einstein did, in fact, predict the existence of such waves back in 1916. Yet so far we have had nothing but an indirect detection in the form of the Hulse-Taylor binary (PSR B1913+16), a pulsar in a binary system that includes a second neutron star, the two orbiting around a common center of mass. The 1993 Nobel Prize in physics went to Richard Hulse and Joseph Hooton Taylor (Princeton University), who showed that the system's orbital decay corresponds with the loss of energy due to the kind of gravitational waves Einstein predicted. What we now need is a direct detection, but these waves have proven to be a tricky catch. Consider this: The distance between two spacecraft flying five million kilometers apart would be changed by about a picometer by the effects of gravitational waves. That's a distance 100 million times smaller than the width of a human hair, some...

The WISE mission has received a lot of press in terms of discovering nearby brown dwarfs, but it's clear that finding low-temperature objects is a major investigation at many Earth-bound sites as well. That includes the UKIRT (United Kingdom Infrared Telescope) Deep Sky Survey's project to find the coolest objects in our galaxy, an effort that has paid off in the form of a unique binary system. One of the stars here is a cool, methane-rich T-dwarf, while the other is a white dwarf, the two low-mass stars orbiting each other though separated by a quarter of a light year. Understanding Brown Dwarf Atmospheres We need to put this find in context. In the absence of hydrogen fusion at the core, brown dwarfs depend upon gravitational contraction as their internal energy source. Cooling slowly over time as they shed their energies, brown dwarfs emit most of their radiation in the infrared, with spectra showing absorption bands of water, methane, carbon monoxide and other molecules in the...

Did the Milky Way once have a jet powered by matter falling into the supermassive black hole at galactic center? There is little evidence for an active jet today, but we do see jets like these in so-called 'active galaxies,' those that show higher than normal luminosity over much of the electromagnetic spectrum. Some jets in active galaxies can be thousands of light years long, evidently emerging from each face of the accretion disk around a central black hole in the so-called active galactic nucleus (AGN). And on a smaller level, we've found similar jets emerging from the accretion disks around neutron stars and stellar-mass black holes. Image: Streaming out from the center of the galaxy M87 like a cosmic searchlight is one of nature's most amazing phenomena, a black-hole-powered jet of electrons and other sub-atomic particles traveling at nearly the speed of light. In this Hubble telescope image, the blue jet contrasts with the yellow glow from the combined light of billions of...

"To a man with a hammer, everything looks like a nail," said Mark Twain, one take on which is that the way we see problems shapes how we see solutions. That fact can be either confining or liberating depending on how open we are to examining our preconceptions, but in the case of Amy Mainzer (JPL), it leads to a natural way to describe a failed star. Mainzer, who is deputy project scientist on the Wide-field Infrared Survey Explorer mission (WISE), is an amateur jewelry-maker. For her, it's easy to look at the image below and see gems. "The brown dwarfs," says Mainzer, "jump out at you like big, fat, green emeralds." And that emerald below, dead center in the image, is hard to miss. Image: The green dot in the middle of this image might look like an emerald amidst glittering diamonds, but it is actually a dim star belonging to a class called brown dwarfs. This particular object, named "WISEPC J045853.90+643451.9" after its location in the sky, is the first ultra-cool brown dwarf...

Sometimes as I click through imagery from spacecraft and observatories, I think about what the world was like before we had an Internet to deliver this kind of information. Consider the early surveys of the heavens, exemplified by William Herschel sweeping the sky in the late 1700s. Herschel's survey would find a new planet, create a basic map of the Milky Way, and note the location of the 'cloudy things' called nebulae, many of which turned out to be galaxies in their own right. His lists and annotations would grow into the New General Catalogue, which identifies thousands of objects by the now familiar NGC numbers. The sky is all about statistics, as Herschel saw. When you're dealing with objects whose lifespan is far longer than a human's, you try to understand them by looking at enough examples to see the objects at every stage of their existence. Ann Finkbeiner offers this lovely Herschel quote in her new book A Grand and Bold Thing (Free Press, 2010): "[The heavens] are now...

What do you get if you combine the insights of nine expert panels, six study groups and a broad survey of the astronomy and astrophysics community? If you’re lucky and have the right committee, you wind up with useful analyses of the readiness and costs of science projects for the future, both major and minor. And as the National Research Council has done in its new report, you then create a decadal survey, in this case the sixth produced by the NRC, that identifies where the US should go next in answering ‘profound questions about the cosmos.’ A prepublication copy of New Worlds, New Horizons in Astronomy and Astrophysics is available online. To understand the needs of space science in the next ten years, though, be prepared for new acronyms. The most significant for Centauri Dreams readers will probably be WFIRST, the 1.5-meter Wide-Field Infrared Survey Telescope, which could launch as early as 2020 as part of our ongoing search for terrestrial exoplanets. In terms of the panel’s...

Anything we can do to advance the cause of adaptive optics is all to the good. It's obvious that a space-based observatory is preferable if we want to get the sharpest look at a distant object, but launch costs are still high and the kind of intricate interferometry missions that will one day let us take a close look at a distant exoplanet are still on the drawing boards. In the interim, learning how to get around the distortion caused by a planetary atmosphere allows us to do things with Earth-based telescopes that earlier astronomers wouldn't have thought possible. The kind of laser adaptive optics in use at the University of Arizona represents a useful advance in the state of the art. Make a telescope mirror pliable enough to respond to hundreds of actuators positioned on its back side and you can create a series of tiny adjustments as you look at the sky. The adjustments are necessary because atmospheric turbulence blurs the image, the result of rising heat disturbing the air a...

Was it really three years ago that New Horizons moved past Jupiter, returning images of its stunning systems of storms and cloud? The mission continues to go well, and the photo below, taken by the spacecraft's Long Range Reconnaissance Imager (LORRI) paints an unusual portrait of Jupiter and two of its largest moons from a distance of more than 16 AU, looking back toward the inner system. Note how faint the moons are, the consequence of the fast shutter speed used, with an exposure time of 0.009 seconds. I like what mission principal investigator Alan Stern says: "This haunting image of Jupiter - far in the distance back in the Sun's warmer clines from whence New Horizons came - reminds us of Voyager's family postcard of the planets taken from beyond Neptune's orbit about 20 years ago. Perhaps after we flyby Pluto in 2015, we'll try something similar from our perch aboard New Horizons." Image: The New Horizons team looked back at Jupiter during Annual Checkout (ACO) 4 to test the...

The space-based Spitzer telescope has performed a new study of brown dwarfs, concentrating on a region in the constellation Boötes. Fourteen of the objects, with temperatures ranging between 450 and 600 Kelvin, have been found. These are cold objects in stellar terms, and in fact are as cold as some of the planets we've found around other stars. 450 Kelvin works out to 177 degrees Celsius, or 350 degrees Fahrenheit, the temperature of a moderately hot oven. In fact, it gives me pause to reflect that the focaccia I baked the night before last needed higher temperatures (500 degrees Fahrenheit) than the coolest of these brown dwarfs can supply. Most of the new objects in the Spitzer study are T dwarfs, the coolest class of brown dwarfs known, defined as being less than 1500 Kelvin (1226 degrees Celsius). One of the dwarfs in this study is cold enough that it may represent the hypothetical class called Y dwarfs, part of a classification created by a co-author of the paper, Davy...

Here's something to put the cap on a scintillating week in space science. It's from Hal Levison (SwRI), who has led an international team in computer simulations focusing on our Sun's earliest days. It turns out that our older assumption that the Oort cloud of comets surrounding the Sun came from the Sun's protoplanetary disk may not be accurate. Yes, our system produced comets, but not enough to account for the Oort's entire population, which swarms in a vast sphere that extends half the distance to Alpha Centauri. Says Levison: "If we assume that the Sun's observed proto-planetary disk can be used to estimate the indigenous population of the Oort cloud, we can conclude that more than 90 percent of the observed Oort cloud comets have an extra-solar origin." Image: Comet McNaught, possibly an interloper from another star, according to recent work. Credit: Stéphane Guisard. The process works like this: We believe the Sun formed in a cluster containing hundreds of closely packed...

Students now getting their degrees in astronomy and even postdocs working in the field have come along at a time when datasets are widely shared. It was not always so, as Alexander Szalay can attest. A professor of physics and astronomy at Johns Hopkins, Szalay was an early player in the Sloan Digital Sky Survey, leading the design of the archive and becoming involved with the statistical tools needed to analyze its holdings. Back in the 1990s, Szalay recalls in the Chronicle of Higher Education (thanks to Regina Oliver for the tip), the astronomy community had no tradition of making data from projects like the SDSS public. In fact, astronomy at the time was a more tightly controlled enterprise. Telescope time, as always, was difficult to get, and no scientist wants critical findings to be claimed by someone else. Szalay remembers that era and the changes that quickly followed: One incident demonstrates the mood at the time. A young astronomer saw a dataset in a published journal and...

We sometimes forget the conditions under which great images get made. A few years back, in one of the earliest posts on his systemic site, Greg Laughlin (UC-Santa Cruz) showed the image you see below, a famous shot made by the Hubble telescope of the 'Sombrero Galaxy,' M104. It's obvious why this image is a classic. As Greg notes, "The glow of its halo makes the idea of 100 billion stars seem comprehensible." But look at the follow-up picture, which Greg made to demonstrate his point. While the Hubble image is a long CCD time-exposure to light gathered by a 240 cm mirror, your own eyes would deliver something considerably different. From 300,000 light years, M104 is noticeable only as a dim and lurking shape. You can see the same effect for yourself if you find the Andromeda Galaxy, subtening an angle larger than the full Moon in our skies but as evanescent as smoke when viewed by the naked eye. The dim, fuzzy object is out there if you know where to look, but it's not exactly...

What a glorious image WISE has given us. The Wide-field Infrared Survey Explorer has finished three-quarters of its infrared map of the entire sky, with the final images scheduled for July, after which time the spacecraft will spend three months on a second survey before its solid-hydrogen coolant (needed to keep its infrared detectors chilled) runs out. The public WISE catalog will be released a little over a year from now, but we can already marvel at spectacles like the Heart and Soul nebulae, seen below. Be sure to click on the image, presented at the American Astronomical Society meeting in Miami, to enlarge it and spend some time among the newly forming stars. Image: Located about 6,000 light-years from Earth, the Heart and Soul nebulae form a vast star-forming complex that makes up part of the Perseus spiral arm of our Milky Way galaxy. The nebula to the right is the Heart, designated IC 1805 and named after its resemblance to a human heart. To the left is the Soul nebula,...

We'd better get familiar with WHIM, the Warm-Hot Intergalactic Medium. According to some cosmologists, this sparse gas exists in the spaces between the galaxies, accounting for up to fifty percent of the normal matter found in today's universe. That would explain a conundrum. By 'normal matter,' I mean baryons, the protons and electrons of the matter we deal with every day. It turns out that we can study distant gas clouds and galaxies well enough to form an estimate of the normal matter found in the early universe, and the problem is that the nearby universe, much older, shows only about half the amount of normal matter that we would expect to find. Now researchers have used the Chandra X-ray Observatory and ESA's XMM-Newton to detect a huge reservoir of interstellar gas apparently embedded in a large-scale structure known as the Sculptor Wall, some 400 million light years from Earth, providing strong support for the WHIM theory. We're probably looking at material left over from the...

Our knowledge of brown dwarfs is expanding rapidly, and with the help of the WISE mission, we will be able to build a much more complete catalog of such stars in our neighborhood. But look what the Hubble Space Telescope, in conjunction with the Gemini Observatory, has produced: A companion to a brown dwarf that gets us right back into the debate about how to define a planet. When Pluto was in question, we were faced with a true imbroglio. Now the question involves not a small but a large object, and forces us to consider whether its origins can make an object of acknowledged planetary mass something else instead. But first, the imagery (this is, after all, a direct detection). The primary brown dwarf is 2M J044144, images of which were obtained as part of a survey of 32 young brown dwarfs in the Taurus star-forming region 450 light years away. Both objects are visible below: Image: Hubble Space Telescope (top) and Gemini North (bottom) images of the 2M J044144 system showing the...

Ordinary baryonic matter (think protons and neutrons) is thought to account for no more than one-sixth of the total mass in the universe, the rest being dark matter that does not reflect or emit light. Usefully, though, dark matter does interact with the rest of the universe through gravity, and it can be probed by studying gravitational lensing. Here the light of distant galaxies is deflected by the gravity of foreground concentrations of mass. All matter, whether baryonic or dark, is sensitive to this effect, making it possible to study dark matter on a large scale. Data from the Cosmic Evolution Survey (COSMOS) offer this possibility, revealing just how dark matter is distributed in the cosmos. And by supplementing COSMOS with redshift data, we're finding that the survey offers clues to dark energy as well. But first, some background on how COSMOS data have been used in dark matter work. 1000 hours of Hubble observations from its Advanced Camera for Surveys (the largest project...

Type Ia supernovae have become important 'standard candles' in judging cosmic distances, telling us how far away the host galaxy of a given supernova is. The idea here is that this kind of supernova produces a consistent luminosity because the white dwarfs that explode in the process are of uniform mass. The Type Ia supernova happens like this: A white dwarf gathers material from a companion star, growing in pressure and density so that the dwarf approaches the Chandrasekhar limit, beyond which it cannot support its own weight. The result is a violent explosion that, like Cepheid variable stars, offers astronomers a way to gauge distances, and thereby to probe the shape of the cosmos at various distances and eras. Just how fast is the universe expanding, and in what ways? It was in 1998, prompted by supernovae of this kind, that the High-z Supernova Search Team discovered that the universe was not only expanding, but that its expansion was accelerating. Suddenly we were talking about...