After 45 years at the Smithsonian Astrophysical Observatory (located on the grounds of Harvard College Observatory in Cambridge, Massachusetts), the organization that serves as the clearinghouse for astronomical discoveries is moving to a new home. As of February 1st, the Director of the International Astronomical Union's Central Bureau for Astronomical Telegrams (CBAT) will be headquartered at Harvard University's Department of Earth and Planetary Sciences, located less than a mile away from SAO.

Since 1882 the CBAT has played a vital function by confirming and announcing discoveries to the worldwide astronomical community. These discoveries include new planetary satellites, meteor showers, comets, novae, and supernovae, and have in the past included many other kinds of objects. Starting in 1883, the HCO issued such announcements for the Western Hemisphere, a function that only stopped when the CBAT moved from Copenhagen to Cambridge in 1965, and the HCO staff was moved over to operate the Bureau as an SAO function.

"Our relocation shouldn't be a big deal to the outside world," says CBAT director Dan Green. He added that the transition should involve little or no disruption of activities. The internet has profoundly changed the way astronomy information is disseminated, and the CBAT stopped sending telegrams in the early 1990s. Now its announcements are even issued via RSS/XML feeds, so that Blackberry owners can follow the latest discoveries. Green notes that there still is an important role for the Bureau in the 21st century.

Green will direct a new Cometary Science Center that is being developed to work alongside the CBAT. "It will be an international center for archiving historical information, images, light curves, and other data at all wavelengths with a big website presence," says Green. Green has lined up a core team of several prominent comet researchers and is soliciting funding to build up a support staff.

The Minor Planet Center, which will continue to work closely with the CBAT for such topics as comet and satellite discoveries, will remain at its current SAO location.

Fitting, isn't it, that the most dramatic views ever made of distant Pluto should be made public on the 104th birthday of its discoverer, the late Clyde Tombaugh?

Today Marc Buie, a devoted Plutophile at the Southwest Research Institute, unveiled maps of Pluto's surface that he derived from Hubble Space Telescope images taken over a 13-month stretch in 2002 and 2003. When compared to a comparable set of Hubble snapshots from 1994, it's clear that the icy surface of this distant world has gone through some big changes.

The new views reveal a surface with three distinct coatings: nearly white areas that are likely a mixture of methane and nitrogen frosts, and terrains that look dark orange and charcoal black, which probably contain complex organic compounds created by constant exposure to radiation.

Most remarkable, Buie says, is that these color changes have taken place rapidly, over just a few years. "That had me scared for a while," he admits. "It's so hard to believe." But because Pluto's moon Charon appears in the same Hubble frames and showed no color shift, Buie finally convinced himself that the alterations were real.

One curiosity is a a large, bright spot straddling the equator, at a longitude of roughly 180°, that has not changed much. Ground-based spectra show this side of Pluto to be capped with a frosting of carbon-monoxide ice. Buie note that evidence for the spot's existence goes back to the 1950s, and it'll be well placed for close-up scrutiny when the New Horizons spacecraft gets there in mid-2015.

In one sense, planetary scientists have been anticipating changes on Pluto. Pluto passed through perihelion in 1989, and it's been gradually chilling out ever sense. It's also in the midst of a gradual seasonal shift that is exposing parts of its northern hemisphere to sunlight for the first time in more than a century, a consequence of this little world's steep axial tilt and 248-year-long orbit.

As the thinking goes, the weak sunlight should cause nitrogen frost to sublimate into gaseous wisps where its warming up north, making that hemisphere darker, and freezing out in the fading sunlight down south, making it brighter (but hidden by shadow). "These changes have to be a consequence of nitrogen ice moving around," says Buie.

Yet few expected such dramatic changes on a place where the temperatures vary little, from –382°F (43 K) in the darkest recesses to about –360°F (55 K) in the dim glow of full sunlight. One who had a hunch is Caltech astronomer Michael Brown, who in 2002 predicted that Pluto might undergo brightness and color shifts much like those now revealed. Yet even he finds the rapidity of Pluto's frosty face-lift surprising. "You're looking at the surface in the solar system which has the biggest changes of anything we've ever seen."

So why are images taken so many years ago only now making their debut, you might ask? Buie explains that the reconstructions were incredibly challenging because even the optical prowess of Hubble's Advanced Camera for Surveys only barely resolved Pluto's disk. It then took four years of crunching by a bank of 20 computers to extract the subtle detail, and Buie admits getting sidetracked by the discovery of two more Plutonian moons, Nix and Hydra, in 2005.

The resulting maps are probably the best views we will have of distant Pluto until the arrival of New Horizons. That's because the ACS's high-resolution camera, used in the 2002-03 campaign, no longer works, and Hubble's new Wide-Field Camera 3 lacks the resolution to pick out any details.

The mystery of a comet-like object circling among the main-belt asteroids has deepened, now that astronomers have slewed the Hubble Space Telescope over for a close-up look.

Today's release of an HST image taken four days ago shows that P/2010 A2 is no normal comet. There's a strange X-shape feature at its brightest end (I hesitate to call it a "nucleus") that defies easy explanation. "This is quite different from the smooth dust envelopes of normal comets," explains David Jewitt (University of California at Los Angeles), who led the Hubble effort. The Hubble view also clearly shows a pointlike object hovering nearby, about 1,000 miles from the "X" and seemingly connected to it by a thread of material.

Comets within the asteroid belt aren't unprecedented. Jewitt's website comments that four others are known. Most notable among these is 133P/Elst-Pizarro, first spotted as an asteroid in 1979 and then found to have a cometary appearance in 1996.

But apart from its long tail of debris, P/2010 A2 doesn't look much like a comet, at least in the HST images taken on January 25th and 29th. Moreover, it lacks the emissions that are usually found in a comet's coma and tail. "No gas yet," Jewitt told me, "but we are still looking." Unfortunately, a request to observe this curiosity with the Spitzer Space Telescope was turned down.

The most likely explanation for this object's sudden appearance (it's a stretch to call it "dramatic" — it's only 20th magnitude) is that a pair of small, unseen asteroids collided, creating the trail of debris first spotted on January 6th by the LINEAR telescope in New Mexico.

So would a smashup involving two main-belt asteroids result in something like this? Perhaps. "Bill Bottke and I are thinking about what kind of modeling would be useful to do with this object," notes David Nesvorny (Southwest Research Institute), "but we have nothing definitive so far." Bottke notes that while a collision seems plausible, it's also possible we are witnessing an asteroid that's been spun up (by gradual interactions with sunlight) to the point that it started shedding mass.

Jewitt says that there's no handle yet on whether the "nucleus" is tumbling or spinning rapidly. But he says more Hubble sessions are planned in the months ahead.

NASA officials today unveiled a new budget for the upcoming fiscal year, a plan that would significantly alter the future of human spaceflight. The Obama administration plan, if enacted by Congress, would cancel the Constellation program for returning astronauts to the Moon, but would greatly increase funding to develop new technologies that could enable future human missions to the Moon, near-Earth asteroids, and Mars. The plan would place greater reliance on private industry for ferrying humans to low-Earth orbit, and it would extend U.S. participation in the International Space Station to 2020.



Despite canceling a program in which $9 billion has already been spent, the plan increases NASA's overall funding by $6 billion over the next five years to about $100 billion total. By developing new propulsion technologies, developing capabilities such as on-orbit fuel depots, and new robotic precursor missions to study the environments for future astronauts, the administration and NASA seem to be betting that they can lower costs for deep-space exploration over the long haul. The plan also calls for more international cooperation.

"We will pursue a more sustainable, affordable approach to manned exploration, and facilitate the growth of a new commercial industry," said NASA administrator Charles Bolden during a Monday press conference.

The budget follows closely on the heels of a report issued last year by an independent, nonpartisan committee chaired by former aerospace executive Norman Augustine. The committee, which included former astronauts, engineers, and experts from the aerospace industry, spelled out in clear language what many have been saying for years: the Constellation Moon program has been given woefully inadequate funding to achieve its lofty goals, and it was putting NASA on an unsustainable trajectory toward failure.

Sally Ride, a member of the Augustine committee and America’s first woman in space, strongly endorsed the proposal during the press briefing. Apollo 11 astronaut Buzz Aldrin issued the following statement::

"Today I wish to endorse strongly the President's new direction for NASA. As an Apollo astronaut, I know the importance of always pushing new frontiers as we explore space. The truth is, that we have already been to the Moon — some 40 years ago. A near-term focus on lowering the cost of access to space and on developing key, cutting-edge technologies to take us further, faster, is just what our Nation needs to maintain its position as the leader in space exploration for the rest of this century. We need to be in this for the long haul, and this program will allow us to again be pushing the boundaries to achieve new and challenging things beyond Earth. I hope NASA will embrace this new direction as much as I do, and help us all continue to use space exploration to drive prosperity and innovation right here on Earth."



In general, I liked much of what I heard, and I was encouraged by the fact that the new NASA plan closely follows many of the recommendations set forth by the Augustine committee. Augustine says in a written statement, "The plan released with the President’s FY 2011 budget does appear to respond to the primary concerns highlighted in our committee's report." But I also felt the new plan involves considerable risks, and doesn't yet outline specific mission objectives and timetables.

What I found particularly interesting about the press conference was the Q&A session. Several reporters called in from states such as Florida, Texas, and Alabama — which have major NASA facilities (Kennedy, Johnson, and Marshall) that develop human spaceflight. The questions all centered around what this new plan would entail for jobs in these local areas, and one reporter said that the Florida Congressional delegation has already come out in opposition to the new plan (even though NASA officials claimed the plan would end up modernizing Kennedy and boosting funding for the center).

I need to learn more about this new plan and its ramifications before I can pass judgment. For the future of NASA, the U.S., and human spaceflight, I just hope that the Congressional meat grinder can ultimately evaluate the new NASA plan on its long-term merits and not on its short-term economic impact on local constituencies.

Towering over the island of Maui is Haleakalā, a 10,023-foot-high dormant volcano whose dramatic summit caldera draws 1.3 million tourists per year. As these visitors take in the breathtaking vista, they can't help but notice the compound of large observatories nearby — testimony to the summit's superb conditions for astronomy.

In Hawaiian culture, Haleakalā is also revered as the sacred "House of the Sun." So it's seemingly fitting that later this year astronomers hope to being construction of the world's largest and most powerful observatory dedicated to the study of our star: the Advanced Technology Solar Telescope.

On January 22nd, the National Science Foundation announced its selection of the Association of Universities for Research in Astronomy to build the ATST. The 8-year agreement totals $298 million, enough to build the observatory and four "first-light" instruments. The construction schedule will surely be helped by an immediate infusion of $146 million from the American Recovery and Reinvestment Act. (What a difference some stimulus funding makes — two years ago AURA's Solar Observatory Council had urged the NSF to scrounge up funding any way it could so that the ATST's planning could go forward.)

Boasting a primary mirror 13 feet (4 m) across and state-of-the-art adaptive optics, ATST will view the Sun with a resolution of 0.1 arcsecond, while spanning the spectrum from 350 nm in the ultraviolet to 28 mm in the far infrared. Such amazing specs should allow astronomers to make never-before-possible measurements of turbulence and magnetic fields in the photosphere, chromosphere, and even incredibly faint corona. No comparable solar scope exists today or is on engineers' drawing boards.

ATST will join a growing armada of observatories atop Haleakalā: the U.S. Air Force's 3.7-m Advanced Electro-Optical System (AEOS) and one of its GEODSS satellite-tracking complexes, and the 2-m Faulkes Telescope North. Mees Solar Observatory, erected in 1964, was the first professional observatory built on the summit.

AURA is starting to line up its construction crews, but not everyone is happy with the prospect of adding ATST's dazzling-white 143-foot-high dome to the summit. Although astronomers picked Haleakalā in 2004 from more than 70 other prospective sites and the project has passed its environmental reviews, some cultural leaders on Maui continue to oppose the ATST.

Representatives for the National Science Foundation have sought to smooth over differences with promises of funding for Maui Community College and other educational activities involving native Hawaiians. Talks with island groups are ongoing. But the project has one final hurdle: it has yet to obtained a conservation district use permit from Hawaii's Board of Land and Natural Resources, which might take months to secure.

This month marks the sixth anniversary of the 2004 arrival on Mars of the NASA rovers Spirit (January 4th) and Opportunity (January 25th). As I noted in December, things have not gone well for Spirit since its wheels became mired in soft sand last May.

Unfortunately, the past month's all-out effort to free the craft has resulted in lots of frustration but little movement. It didn't help that a second wheel failed on the right side. And the situation is getting more dire because Martian winter is approaching, which means the Sun is providing less energy each sol (day) for electricity and it's getting colder.

Today, NASA managers held a press briefing to announce that they've called off the effort to get Spirit rolling again. Instead, operations in the coming weeks will focus on improving the craft's tilt so its solar-cell panels can receive more sunlight during the winter months ahead. The craft is designed to withstand temperatures down to –67°F (–55°C), and scientists expect it to survive the coming cold provided there's enough electricity to power critical internal heaters.

If Spirit really has reached its final destination, then let the record show that it traveled a remarkable 4.80 miles (7.73 km) since thumping onto the flat floor of Gusev crater. But immobility doesn't mean that the mission is over. Instead, the team wants to take advantage of being motionless to conduct an interesting new kind of science.

As explained today by Steve Squyres, the Cornell researcher who serves as the mission's principal investigator, Spirit will become a radio beacon for tracking the rover's exact location as Mars rotates. If Spirit can continue transmitting for several more months, engineers will be able to determine its position on the surface to within a few inches and track tiny wobbles in the rotation of Mars. These measurements, in turn, should reveal whether the Red Planet is solid throughout or has a liquid outer core.

This kind of "stationary science" was performed during the Mars Pathfinder mission during the late 1990s. Although the results were useful, Pathfinder didn't operate on Mars long enough to get the desired precision. Back in the late 1970s, two Viking landers stayed put during several years of operation, but they utilized older radio technology that couldn't make the needed measurements either.

"If the final scientific feather in Spirit's cap is determining whether the core of Mars is liquid or solid, that would be wonderful," Squyres commented today. "It's so different from the other knowledge we've gained."

Cosmologists are a small, elite fraternity whose work informs our knowledge of the cosmos at the highest, grandest levels.

But their close-knit universe was rocked this past weekend as word spread of the sudden death of Andrew Lange. Although not mentioned in the brief announcement posted by Caltech, where until recently he'd served as chairman of its Physics, Mathematics, and Astronomy Division, he had struggled with personal issues and apparently took his own life.

Although I never met Lange in person, I've been keenly aware of his importance to our understanding of the early universe. Most notably, he was co-leader of the Boomerang project that used a balloon-borne telescope, launched from Antarctica, to map the detailed structure of the cosmic microwave background. These whispers of microwave energy are the slowly dying echoes of the primordial fireball unleashed during the Big Bang.

Lange's observations with Boomerang measured the angular size of subtle variations within the CMB and led to the realization that the infant universe assumed a flat geometry after an initially rapid growth spurt due to inflation.

Boomerang's results followed closely on the heels of a breakthrough by two teams, led respectively by Adam Riess and Saul Perlmutter (both at University of California, Berkeley), who found that distant galaxies are moving away from us at ever-greater speeds and that the flat universe must be permeated with a type of negative gravitational pressure — often dubbed "dark energy."

After spending six years as an assistant professor at UC Berkeley, Lange arrived at Caltech to stay in 1993 and soon distinguished himself as one of its leading scientists (in a place where just about everyone is a leading scientist). In 2003 he and Perlmutter were jointly named "California Scientists of the Year" by the California ScienCenter. The following year Lange was elected to the U.S. National Academy of Sciences.

On Saturday, in an address emailed to the Caltech community, president Jean-Lou Chameau noted, "Among the most difficult things that people have to deal with in life are tragedies of this sort, especially when they affect people that we know and care for; and Andrew was such a well-known, well-respected, and well-liked member of our community that many of us will be deeply affected."

Click here to watch a lecture given by Lange, just last November, on how the universe began.

Given the odds of some giant space rock crashing into Earth and what it might do when it hits, scientists now estimate that on average 100 people will die each year from a cosmic impact. How much this number scares you depends on how far out you want to look into the crystal ball. Within the next couple of centuries a Tunguska-like blast might match the devastation of the earthquake that just devastated Haiti. Or fast forward 10 million years, and you can expect a titanic crash powerful enough to wipe out a billion people worldwide.

So should you be worried or not? Put another way, to what lengths — and at what cost — should we go to try to protect ourselves from some asteroid or comet "going rogue" in the foreseeable future?

In 1998 Congress felt worried enough about the sky falling that it tasked NASA with finding 90% of all the near-Earth asteroids at least 1 km across within 10 years. (Anything this size would likely trigger global devastation during and after its collision.) Then Congress raised the bar in 2005, mandating that NASA find 90% of all the threatening asteroids with diameters down to 140 meters (460 feet) by 2020.

It looks good on paper, but neither Congress nor NASA have ever anted up the dedicated funds to do those searches. Back in the mid-1990s, NASA scientist David Morrison famously observed that fewer people are watching for asteroids able to collide with Earth than work in a typical McDonald's franchise. And while more observers are warily sweeping the sky these days, including many capable amateur astronomers, they're doing so by coattailing on other space surveys not optimized for the task.

In short, there aren't enough bodies or telescopes in the impact game to meet the 2020 deadline set by Congress. Don't take my word for it — read the 149-page report released today by an A-list panel of experts assembled by the National Research Council. Titled Defending Planet Earth,, it explores both the best ways to track down all the hazardous near-Earth objects (NEOs) and what to do once it becomes clear that one of them is destined to have a run-in with Earth.

The NRC report both summarizes the state of the searches to date and lays out the steps that NASA or the National Science Foundation (which funds most professional astronomy in the U.S.) would need to take to get serious about cosmic threats. "This is a huge milestone," observes small-body specialist Richard Binzel (MIT), who had no role in the committee or its findings. "The asteroid problem is now a grownup, joining the table of other natural disasters for which mitigation strategies are developed."

Pointedly, the NRC panel states that the Congressional target simply can't be met by 2020. If NASA and NSF managers decide they want to complete the survey as soon afterward as possible, then they'll need to fortify observers not only with dedicated ground-based efforts like the proposed Large Synoptic Survey Telescope but also with a infrared-sensing space observatory. Or ground-based telescopes could go it alone, which would keep costs down but delay the completion date until about 2030.

Concerning mitigation strategies, the panel assessed four approaches and found them all viable and complementary. For the smallest and thus localized impact threats, the most cost-effective approach is simply to move people out of harm's way, either by sheltering or evacuating them.

Bigger NEOs, ranging up to 100 m across, would affect too large an area to make civil defense practicable. So a passive space-based defense — using a spacecraft to pull or push the body enough to alter its path — would work better. For still-larger impactors, up to 1 km in size, a salvo of spacecraft might need to strike it head-on to change its course. But both of these methods would make only slight trajectory redirections and thus require many orbits, over decades of lead time, to avert a disastrous collision.

For the biggest threats, or if one of the other methods fails or if the lead time is short, the panel concludes that the "only current, practical means" are nuclear explosions. These wouldn't be used disrupt the incoming body but rather to give it a Really Big Push all at once. (No need to cue Bruce Willis and his Armageddon team — these would be delivered robitically.)

There's more. As noted in its preliminary findings, released last year, the NRC panel emphasizes the crucial role being played by the unique radar capabilities of Arecibo Observatory Puerto Rico — a facility that an NSF review team felt ought to find its funding elsewhere or be shut down.

It's going to take me a few more days to digest all the content in Defending Planet Earth. Click here if you'd like to download it for your own perusal, or click here for a news summary posted by the NRC's news office.

January 7th's announcement that the LINEAR telescope had spotted a new periodic comet wasn't all that interesting: a 20th-magnitude blip out in the asteroid belt in a benign orbit that wouldn't come anywhere near Earth. Designated P/2010 A2 (LINEAR) by the IAU's Minor Planet Center, it was just another notch on the finderscope for this discovery machine near Socorro, New Mexico, which has chalked up 77 periodic comets (and a couple hundred one-timers) since coming online in 1998.

But as other observers chipped in positions over the next week, it became clear that this was an object worth watching. For one thing, the now-precise orbit was looking less like a comet's and more like an asteroid's. And images of the interloper showed a tail growing in length yet without a clearly defined head. The online chatter got more animated — just what was this, anyway?

On January 14th, Javier Licandro and others used the Nordic Optical Telescope in the Canary Islands to get a better view, and they discovered something completely unexpected: a small asteroid lay 2 arcseconds to P/2010 A2's east and was moving along with it. Moreover, the "comet" showed no central condensation and looked more like a narrow dust swarm about 110,000 miles (177,000 km) long.

Licandro quickly enlisted the biggest aperture in the island's observatory complex: the Gran Telescopio Canarias. Dozens of images taken three days ago using its immense 34-foot (10.4-m) aperture confirm that the "comet" is being shadowed. It's hard not to conclude that we are watching the aftermath of a collision in the asteroid belt. But it's still too early to know for sure. Licandro and his colleagues are analyzing the GTC images carefully — and they hope to make them public soon.

Meanwhile, comet specialists are hoping to observe the strange goings-on with both the Hubble and Spitzer space telescopes. Neither has been given the green light yet, but if/when that happens the observations would be made within the next few days. According to Caltech astronomer William Reach, Spitzer no longer has the ability to look deep in the infrared, but it can still record at 3.6 and 4.5 microns, where the cometary gases carbon monoxide and carbon dioxide have strong emissions.

Back in the mid- to late 1990s exoplanet discoveries trickled out slowly: perhaps one every few months. Each one was greeted with headlines and euphoria. Nowadays, with the count at 424 known planets outside our solar system, the bar is much higher. We certainly know that plenty of planets exist. The burning questions now center around the physical characteristics and environments of these distant worlds, and what we can learn from their overall statictics, and whether other planetary systems resembling our own solar system are common or rare.

With this backdrop, multiple teams announced new exoplanet results at the 215th American Astronomical Society meeting, held last week in Washington, DC. With more than 3,400 registrants, the meeting was the largest in AAS history and in fact was the largest gathering of professional astronomers in world history.

Project scientists for NASA's Kepler mission announced a first batch of exciting results at the meeting's start. Then at a press conference a couple days later, five other teams described new exoplanet results of their own:

Massive host stars. A group led by Xavier Koenig (Harvard University) used the MMT Telescope in Arizona to survey disks around big young stars having 1.5 to 15 times the mass of our Sun. These will settle down to be hot shiners of spectral types F, A, and B once they're finished with their birth processes. Koenig and his colleagues found that disks around such stars are plentiful, and that the disks' infrared signatures indicate that planets commonly form around massive stars.

Such hefty stars don’t live long enough to support planets that could develop advanced life (assuming the process takes as long as it did on Earth). But it's now clear that planet formation is a robust process that occurs around stars over essentially the whole range of stellar masses, from the bottom to the top of the main sequence: from dim red M dwarfs to hot, blue-white B dazzlers. More information.

Weird disk stuff. Carl Melis (University of San Diego) led a group that found a planetary-debris disk around HD 131488 in Centaurus, a young star about 10 million years old with three solar masses. The dusty debris forming the disk almost certainly came from a collision between more-or-less planet-sized bodies, as happened in our own young solar system. That's no big news these days; many other cases have been found. But observations taken with the Gemini South Telescope in Chile show that this particular disk differs considerably in composition from those seen around other stars.

Most debris disks (when infrared spectral signs of their composition can be seen) turn out to be rich in olivine, pyroxene, and/or silicate minerals, just like meteorites from our early solar system. But the stuff in the disk around HD 131488 bears no apparent resemblance to such material. Its composition remains unknown. In addition, this star is also the first to show both warm debris dust near the star and cold primordial dust much farther out. More information.

Super-volcanic planet from hell. Rory Barnes (University of Washington) announced more news about the only exoplanet known to be rocky in composition, Corot-7b: a super-Earth with Earth's density and about 5 times Earth's mass. This planet orbits so close to its star, a yellow-orange dwarf, that its surface should be roasted to be about as hot as molten lava (Sky & Telescope cover story, May 2009).

In addition, said Barnes, the planet probably has extremely active volcanism, due to strong internal heating as well. It orbits its star at only 1.6 million miles (1/60th the Earth-Sun distance) and completes an orbit every 20.5 hours. If the planet’s orbit is even very slightly elongated — which is quite likely given the presence of a second planet, whose mass should perturb the orbit — then Corot-7b will be tidally squeezed and flexed once per orbit. Internal friction will dissipate some of this tidal energy, heating the planet’s interior just as Io's slightly eccentric orbit around Jupiter gives rise to tidal flexing and vigorous volcanism. But in the case of Corot-7b, the effect should be many times greater.

Bare core of a gas giant? Speaking of Corot-7b, Brian Jackson (NASA/Goddard Space Flight Center) presented a study showing that this “planet from hell” is probably losing significant mass under the heat blast of its star. It could be shedding half an Earth mass every billion years. Extrapolating backward in time, Jackson concludes that the planet may have started as a gas-giant world more akin to Jupiter or Saturn, and that its light elements were driven off. In other words, this and perhaps other hot super-Earths could be the rocky remnant cores of former gas giants. More info.

Frequency of familiar solar systems. Scott Gaudi (The Ohio State University) presented results of his own team’s search for planets by looking for cases of gravitational microlensing of distant background stars, an effect predicted by Einstein’s general theory of relativity. The team’s recent collaboration has found signs of six planets by this method, including one system with two planets at least roughly analogous to Jupiter and Saturn.

Gaudi noted that if all stars hosted planetary systems similar to our own, the team should have found more planets out there, and in particular more multi-giant-planet systems. Based on these early statistics, Gaudi argues that roughly one-third of stars host at least one giant planet in a distant orbit, and roughly one-sixth of stars have multiple giant planets in distant orbits as the Sun does. Given the 200-billion-plus stars in our galaxy, that means the Milky Way is home to tens of billions of planetary systems that at least superficially resemble ours.

These statistics are still rough. But they also imply that in most planetary systems that exist at all, giant planets do not migrate inward through the star's habitable zone, as has happened in so many of the easily discoverable systems that have been found so far. This is good news for the survival of terrestrial planets capable of forming life.

One of the greatest surprises in the history of astronomy was the discovery that all the things we see in space amount to less than 1% of the universe’s total matter and energy.

Add the hard-to-detect thin gas between galaxies, and all other forms of ordinary matter, and the total still comes to only about 4.5% of everything that exists. A much larger 26% or so is "non-baryonic dark matter," consisting of some kind of exotic, invisible particles that don't form atoms. The dark matter's gravity dominates the universe, shaped its history, and provides the gravitational pools in which normal matter could accumulate to make galaxies, like scum patches on invisible ponds.

The remaining 70% or so is the so-called "dark energy" that's causing the expansion of the universe to speed up. The nature of this is an even bigger unknown.

But more bits of evidence keep being uncovered. At a press conference last Wednesday at the American Astronomical Society meeting, four teams announced new results that improve our understanding of these phenomena.

The Milky Way's lopsided halo. Astronomers have long known that large galaxies, such as our Milky Way, are centered in larger pools of dark matter known as halos. A group led by David Law of UCLA determined that the Milky Way's dark-matter halo is not spherical but has a squashed shape. Surprisingly, it is flattened along an axis that's tipped 90° sideways to the visible disk of stars defining the familiar Milky Way band in the night sky.

The team reached this conclusion by analyzing the motions of thousands of stars in the "Sagittarius stream," shown below. The stream is the remnant of a dwarf galaxy that was tidally ripped apart by the Milky Way’s gravity during a close pass, leaving a long filament that now wraps twice around our galaxy well outside it. The motions of stars in different parts of the stream reveal the gravitational fields working on them in different parts of the halo.



The halo actually turns out to be triaxial in shape, meaning that it has a different diameter in each of three directions. “If the halo is likened to a cosmic beach ball, it has been squashed on one side,” said Law; see his representation below.

Law added that astronomers expected the halo to be squashed along the same axis as the Milky Way's disk, since the normal and dark matter both presumably arrived by way of the same source: filaments of dark matter defining gravitational channels leading in.

The halo's size and shape have been influenced by the Milky Way's recent cannibalizations of other dwarf galaxies, so future detailed studies of the halo should give more information about the Milky Way’s evolution as it gathered in its small neighbors.

Local dark energy. More than 10 years ago astronomers discovered that the expansion of the universe is accelerating, the opposite of what they had expected. A key to this revelation was the ability to measure the distances of far galaxies by the apparent brightnesses of Type-Ia supernovae within them, independently of a galaxy's redshift. This distance can then be matched with the redshift — which tells how much the universe expanded while the light was in transit. In this way, astronomers were able to see how the expansion rate has changed over long stretches of cosmic time.

Since then, astronomers have found a wealth of other evidence that some force is causing the expansion to speed up — and how much of it there is, and the crucial fact that it seems to be neither weakening nor strengthening as space enlarges. It was named "dark energy" for lack of anything better.

Now an international team has teased out the effects of dark energy in our own Local Group of galaxies. The Local Group includes the Milky Way, the Andromeda Galaxy, M33, and about 50 dwarf galaxies identified so far.

The team analyzed recent Hubble Space Telescope observations of Local Group galaxy motions (radial velocities), made by a team led by Russian astronomer Igor Karachentsev. By studying how galaxies move with respect to the gravitational center of the Local Group, they could find the boundary where the Local Group’s gravity gives way to dark energy’s “antigravity” effect on larger scales. Dwarf galaxies beyond this boundary are moving outward and will be lost.

“We found a dark-energy outflow repulsion consistent with that found from studying galaxies that are billions of light-years away,” said team member Gene Byrd of the University of Alabama. He added that in the past, scientists usually discover an important effect locally and then apply it to more distant objects. “In this case, we’re going from a global effect to a local effect.”

The smaller the galaxy, the more dark matter. A third group, led by Stacy McGaugh of the University of Maryland, surveyed objects ranging from dwarf galaxies on the small end to the largest clusters of galaxies on the large end, to see whether their ratios of normal matter to dark matter vary with size. From smallest to largest, the objects differed in mass by a factor of a hundred million.

There was indeed a striking trend. McGaugh and his colleagues found that the larger the galaxy or cluster, the greater its proportion of normal, baryonic matter. In the cosmos as a whole and in the largest clusters, dark matter outweighs baryonic matter by about 5 to 1. But the ratio goes up in smaller structures, to the point that dwarf galaxies possess very little baryonic matter relative to dark matter. “For each and every [smaller] object in the universe, some of the normal matter is unaccounted for, and it's a large fraction of normal matter in smaller objects,” said McGaugh. “We don’t know where it is, and it’s a big problem.”

One theory is that the smaller the galaxy, the less able it is to hold onto gas blown by early supernovae; in galaxies without much gravity, the gas flies away to join the thin intergalactic medium. The dark matter, which doesn't interact with normal matter and doesn't feel supernova blast waves, is left behind.

Galaxy growth. A fourth group, led by Niv Drory of the Max Planck Institute for Extraterrestrial Physics in Germany, analyzed data on 300,000 galaxies from the Cosmic Evolution Survey (COSMOS) to determine how galaxies have evolved over the past 8 billion years. The team’s goal is to determine how many galaxies of different masses existed at different epochs in cosmic history. As Drory stated, “We want to understand how our local zoo of galaxies came to be.”

Galaxies began small and numerous, and these mini-structures merged over time to create big ones like the Milky Way. But apparently the process wasn't simple. The group found that the spread of galaxy masses is not as smooth as was thought: dwarf galaxies increase rapidly in numbers with lower mass. And large galaxies show a particular bump in the graph of their mass distribution. These results provide clues about how the mergers of dark-matter halos have unfolded over time, and how feedback mechanisms, such as supernova winds driving gas out of small galaxies, have shaped cosmic evolution. “With this survey, we can trace this evolution back to half the present age of the universe,” says Drory.

Less than a month after a December 14th launch, scientists have unveiled the first image from NASA’s newest astronomical satellite, the $300 million Wide-field Infrared Survey Explorer (WISE), the subject of Sky & Telescope's December cover story. The image, below, was publicly released at the ongoing American Astronomical Society meeting in Washington, DC.



“WISE is performing superbly,” said mission scientist David Leisawitz of NASA’s Goddard Space Flight Center. “WISE is poised to deliver on its promise to measure hundreds of millions of stars, hundreds of millions of galaxies, and hundreds of thousands of solar system objects such as asteroids.”

WISE is designed to perform by far the deepest and sharpest survey of the whole sky yet made in the mid-infrared region of the spectrum. Using instruments cooled by a block of frozen hydrogen, WISE observes at wavebands centered on 3.4, 4.7, 12, and 22 microns (from 7 to 45 times longer than the wavelength of yellow light). It will bring mid-infrared sky maps nearly up to the quality of those that now exist in near-infrared and visible light. The mid-infrared is crucial to many many kinds of modern astronomy — including cool and cold objects of all kinds, highly redshifted objects in the early universe,
and penetration of thick dust in nests of star formation.

The first-light image shows a patch of sky in Carina three times the area of the full Moon. The 3.4-micron band is shown as blue, 4.7 microns as green, and 12 as red. The image reveals about 3,000 stars, including the bright red giant V482 Carinae. It also shows a small dust nebula, glowing with its own very weak heat, at top and left. The field was chosen for engineering purposes rather than for science, but it demonstrates that the spacecraft and camera are performing to specifications. “We are definitely in focus,” said WISE project manager William Irace of the Jet Propulsion Laboratory.

Once the in-orbit checkout phase is completed in the next week, WISE will begin a 6-month all-sky survey at all four of its infrared wavelengths, taking images similar to the one above. After the 6-month survey is complete, WISE is scheduled perform a follow-up scan of half the sky for another 3 months before its solid-hydrogen coolant is expected to run out.

Even after that, said Irace, “We expect WISE to be functional in the short-wavelength bands, and we’re asking NASA to fund us for another 3 months.”

Besides locating the precise positions of millions of stars and galaxies, WISE will find huge numbers of new asteroids, no doubt including some whose orbits cross Earth’s. It will pinpoint hundreds of the dim "failed stars" known as brown dwarfs and could potentially reveal one or more brown dwarfs closer to us than the nearest star, Proxima Centauri. In essence, WISE is a trailblazer mission designed to identify huge numbers of interesting targets for more detailed follow-up studies with ground- and space-based telescopes, such as NASA's future infrared James Webb Space Telescope, billed as the succesor to Hubble.

“WISE is a pristine new observatory ready to deliver to the astronomical community and world inspiring new pictures and information,” added Leisawitz. “Whenever you survey the sky in some new wavelength band with new capabilities, we’re always surprised. So expect surprises.”

It was tricks and treats for several hundred attendees at the Advanced Imaging Conference held in San Jose, California, on Halloween weekend last October. Numerous tricks of the astrophotography trade were revealed by presenters at a day-long series of workshops covering topics ranging from data acquisition and calibration through final tweaking of processed images. Treats too were numerous and included a day of lectures by distinguished speakers, as well as a chance for conference attendees to make and renew acquaintances and talk shop. Another highlight was a ballroom-size vendor area where people could see (and purchase) the latest astrophotography gear. During the conference, Sky & Telescope’s senior editor Dennis di Cicco conducted video interviews with equipment manufacturers and software developers at the cutting edge of today’s astrophotography hobby.

Click on one of the names below to watch an in-depth interview with the corresponding vendor.


ASA Astrosysteme Austria


Astro-Physics


Celestron


Ceravolo Optical Systems


DC3 Dreams


PlaneWave Instruments

If you’re impressed by the speed of a kitchen blender, consider a millisecond pulsar. Not only do these strange micro-stars spin much faster than blenders — several hundred times per second — they squeeze more than a Sun’s worth of mass into a sphere about 20 kilometers wide, about the diameter of a large city.

Until recently, astronomers knew of 60 of these whirling dervishes floating loose in the Milky Way. But thanks to a fruitful collaboration between radio astronomers and the science team of NASA’s Fermi Gamma-ray Space Telescope, we suddenly know of 17 more millisecond pulsars. “This is a really big increase in the number of known millisecond pulsars in our galaxy. A lot of new science will come from these discoveries,” said Fermi team member Paul Ray (Naval Research Laboratory) during a Tuesday press conference at this week's American Astronomical Society meeting in Washington, DC.

Fermi’s primary instrument, the Large Area Telescope, picked up these sources during the orbiting observatory’s first-year sky survey. In total, Fermi recorded 1,451 discrete gamma-ray-emitting objects in the sky, a large increase in the number known. Using some of the world’s largest radio telescopes, in West Virginia, Puerto Rico, Australia, France, and Germany, radio astronomers have picked up pulsating signals from several dozen radio pulsars at these sites.

Pulsars are rapidly spinning neutron stars left behind when a massive star collapses in on itself and explodes as a supernova. Seventeen of the new objects spin so fast that their rotation periods can be measured in milliseconds (thousandths of a second). Normally even a newborn pulsar spins only several dozen times per second, and then slows down over time. Millisecond pulsars, in contrast, have been spun up by accreting mass from a close-orbiting binary companion, usually a relatively normal star. In fact, 15 of the 17 newfound millisecond pulsars have orbiting companions. The presence of a companion is betrayed by periodic speedups and slowdowns in the observed pulse rate, as the emitting object is pulled toward and away from us by the orbiting companion's gravity.

Scott Ransom of the National Radio Astronomy Observatory admitted that isolated millisecond pulsars, such as the remaining two of the new batch of 17, remain a mystery. “We don’t know where isolated millisecond pulsars come from. There might be another mechanism for making them.” One possibility is that the intense winds and beams of radiation from millisecond pulsars completely erode away their companions, leaving nothing. But Ransom said it’s unclear whether there has been enough time for this to happen.

The collaboration between Fermi scientists and radio astronomers is likely to bag many more millisecond pulsars in the coming years. Instead of slowly scanning the sky blindly for new pulsars, radio astronomers can go right to the likely spots on the gamma-ray astronomers’ “treasure map,” says Ransom.

Finding more of them matters. Millisecond pulsars are the most precise and predictable "clocks" in nature, matching or exceeding the best artificial atomic clocks. If astronomers find enough of these objects with strong radio signals, they could use them as a "galactic GPS system." An array of radio telescopes capable of precisely monitoring the timing of dozens of these objects could reveal subtle distortions in the fabric of space-time caused by gravitational waves passing through our region of space. These waves, predicted by Einstein’s general theory of relativity, result from violent events involving massive dense objects, such as the merger of supermassive black holes. To date, scientists have only detected gravitational indirectly. “A lot of the new millisecond pulsars are very bright, and very good for this project,” says Ransom.

Ransom also pointed out that the very first planets outside the solar system were found orbiting a millisecond pulsar, in 1992. So far only one more pulsar planet has shown up despite extensive searches in the timing data. In the coming years, radio astronomers will make precise timing measurements of these 17 new millisecond pulsars to see if any of them harbor planetary systems.

See images and animations on the Fermi site.

See press releases from ASTRON in the Netherlands and from the National Radio Astronomy Observatory.

Astronomers today announced a significant advance in solving the long mystery of Epsilon Aurigae, an enigmatic star that, every 27.1 years, loses half its light for almost two years. The star has mystified astronomers for nearly two centuries despite the fact that it’s easily visible to the naked eye and has been intensively observed by professional and amateur astronomers for decades.

At the American Astronomical Society meeting in Washington, DC, Donald Hoard of Caltech described recent infrared observations from NASA’s Spitzer Space Telescope and a new model that apparently, for the first time, fully ties together the mountains of available data. “What our result has provided is a big-picture solution,” said Hoard. But he was quick to add, “There are still a lot of details that need to be worked out.”

Prior to the most recent dimming, which began in August 2009, astronomers had built up a picture of the system in which the visible star, a type-F supergiant, is much more massive than the Sun. That's what its extreme luminosity (130,000 times the Sun's brightness) would suggest. Every 27.1 years, a huge dusty disk seen almost edge-on slides across the face of the star, producing the long-lasting partial eclipse. But big questions remained about the nature of the bright star, the eclipsing disk, and especially the unseen massive object or objects that must occupy the disk's center (Sky & Telescope, May 2009, page 58).

The Spitzer observations, combined with many observations at visible and ultraviolet wavelengths, provide a more complete picture of the system. The Spitzer work conclusively reveals the presence of a disk about 8 astronomical units in diameter, as expected, and also shows that it consists of relatively large particles mostly the size of sand grains, not the usual microscopically fine space dust. Far-ultraviolet observations also indicate the presence of a smaller, very hot star at the center of the disk, probably spectral type B (about three times hotter than the Sun).

The problem with this model has been that the disk's central object seems to have about the same mass as the F supergiant, and if it's a normal star with such a high mass, it should shine about equally bright. But we hardly see it at all — even though the center of the disk seems to be clear.

Hoard and his colleagues have proposed a model they say fits all the observations. The key part is that the bright F supergiant is much less massive than previously thought. It could still shine so powerfully if it is very far evolved and nearing the end of its life. In this scenario it started off with around 10 solar masses (as opposed to the 15 or 20 usually assumed for it) and has since blown off much of even that. The companion B star is then allowed to have only about 6 solar masses, and therefore shines much dimmer. In this scenario, the dark disk is not the sign of a newborn star still gathering material. The disk instead is made of material that the B star gravitationally captured from the dying primary star's wind.

The disk currently contains much less than an Earth mass, but it probably began with much more. Its original gas and microscopic dust grains have been blown out of the system, leaving only the larger grains behind. The system itself is probably about 10 million years old. Over the next thousands of years, the dying F star will puff off most of its remaining mass to form a planetary nebula.

“All of these intertwined parameters just sort of work out,” says Hoard, who adds that he previously favored another model. “I’m a convert to this model, but I am very comfortable with it.”

Arne Henden, director of the American Association of Variable Star Observers, emphasizes that the mystery of Epsilon Aurigae has not yet been solved. “We’re nearing the middle of the eclipse, and lots of interesting things will happen over the next year. There are still things about this system we don’t understand.”

Hoard and Henden both point out that the AAVSO has organized a global network of “citizen scientists” to monitor Espilon Aurigae’s changing brightness and spectrum. The massive amount of information from high-quality amateur observations (photometry and spectroscopy), as well as continued professional observations, should finally solve the mystery of Epsilon Aurigae. “If there is any time we will understand this system, it’s with this current round of observations,” says Henden.