AAS Session 328: Black Holes I, January 6th

The debate of whether or not a supermassive black hole (SMBH) was kicked out of the centre of a galaxy continues in the Black Holes I session at the AAS. According to Stefanie Komossa and her team at the Max Plank Institute for extraterrestrial Physics (MPE) back in May 2008, spectroscopic data of a galactic core appeared to show a collision event between two SMBHs. In this case, the smaller SMBH was propelled out of its host galaxy by an intense and focused "superkick" by gravitational waves.

However, the delegates attending Session 328 have other ideas…

Tamara Bogdanovic, University of Maryland, kicked off the Black Hole I Session with an investigation into the spectroscopic data derived by Komossa et al. Bogdanovic presented her research on the possibility that rather than showing a superkick, the data could be showing the motion of binary SMBHs around the galactic core after a galactic merger. She made the rather sobering statement that there were, "more publications than data," highlighting the fact that far from being conclusive evidence of a superkick, that more subtle mechanisms may be at work. Model data of orbiting binaries appear to fit the same spectroscopic analysis just as well as the superkick situation. As binary SMBHs would be long-lived objects, there's a good (statistical) chance of observing them. Further work is required, however, possibly using the Very Long Baseline Array (VLBA).

Dipanker Maitra, of the University of Amsterdam, then presented his results of time-dependent modelling of Sagittarius A* (the SBH at the centre of our galaxy). It turns out that there are more high energy flare events detected from Sag A* than expected from the predicted accretion rate. Maitra models the time lag observed in radio data between the first high-energy flares and the following low energy flares.

Jen Blum, from the University of Maryland, then took on the emissions from a stellar black hole in the X-ray binary GRS 1915+105. Key to Blum's research is to investigate the strange asymmetric iron emission line. It looks like this asymmetry can be explained by a combination of special relativity and general relativity effects near the space-time warping black hole.

David Garofalo, who works at JPL/Caltech, then followed quickly with his research of the "central engine" inside galactic nuclei, investigating how strong a SMBH's magnetic field can be. In his models, he finds the spin of the black hole is key to magnetic field strength. Counter-intuitively, Garofalo's work suggests that the fastest spinning black holes may have the weakest magnetic field. Also, slowly spinning SMBHs appear to have a larger gap region. He is quick to point out that his model only shows us what configurations are possible, but concludes with the suggestion that you don't need a fast-spinning SMBH for powerful jets to be generated. "[It's a] tug-o-war between gravity and the Lorentz forces," he said when referring to his model, "but other [unaccounted for] physics may significantly modify the model."

Avery Broderick, from the Canadian Institute for Theoretical Astrophysics, examines jets produced by the Milky Way's SMBH and M87. Both are fantastic objects to study as they are relatively close. However, the angular resolution of instrumentation needs to be boosted, or new techniques are needed to understand jet mechanisms.

Massimo Dotti, from the University of Michigan, re-explored Komossa's research, also supporting Tamara Bogdanovic's work that a superkick may not have caused the emissions studied by Komossa. He also shows that a galactic merger and then SMBH binary can generate similar red-shifted and blue-shifted components of emission profiles. Dotti then showed details of his model and proposed some observational constrains.

Bonus speaker and NASA scientist Teddy Cheung then discussed his search for "offset galactic nuclei" that may be evidence for SMBH collisions in the centre of galaxies. According to Cheung, the calculations to find the black hole masses can be "done on the back of an envelope… the flap of the envelope!" He then showed some results of the observation campaign, pointing to a few candidates that might reveal a SMBH binary partner may have achieved escape velocity (i.e. been kicked out of the galaxy), but he emphasised that this number was small. Radio data of pre-merger and post-merger lobes were also presented, helping future studies characterize collision and merger events.

All in all, Session 328 was a superb start to the conference for me, really opening my eyes to the cutting edge supermassive black hole research going on around the world. There's a lot more where that came from…

Written by Ian O'Neill

Universe Today

NASA's Swift Shows Active Galaxies Are Different Near and Far

Swift's Hard X-ray Survey offers the first unbiased census of active galactic nuclei in decades. Dense clouds of dust and gas, illustrated here, can obscure less energetic radiation from an active galaxy's central black hole. High-energy X-rays, however, easily pass through. Credit: ESA/NASA/AVO/Paolo Padovani

Merging systems account for about 30 percent of the active galaxies cataloged by Swift. This image from the 2m telescope at Kitt Peak National Observatory in Arizona shows NGC 1142, an active galaxy undergoing such a collision. Credit: NASA/Swift/NOAO/Michael Koss (Univ. of Maryland) and Richard Mushotzky


This image shows a typical "red and dead" galaxy as seen by the Kitt Peak 2m telescope. The galaxy shows no sign of active star formation. Its color reddens as existing stars age. Credit: NASA/Swift/NOAO/Michael Koss (Univ. of Maryland) and Richard Mushotzky

A beautiful "blue and booming" spiral galaxy sparkles with the light of rich clusters containing hot, young, massive stars. The blue color indicates the galaxy has a healthy "pulse" of star formation. The galaxy was imaged using the 2m telescope at Kitt Peak. Credit: NASA/Swift/NOAO/Michael Koss (Univ. of Maryland) and Richard Mushotzky

An ongoing X-ray survey undertaken by NASA's Swift spacecraft is revealing differences between nearby active galaxies and those located about halfway across the universe. Understanding these differences will help clarify the relationship between a galaxy and its central black hole.

"There's a lot we don't know about the workings of supermassive black holes," says Richard Mushotzky of NASA's Goddard Space Flight Center in Greenbelt, Md. Astronomers think the intense emission from the centers, or nuclei, of active galaxies arises near a central black hole containing more than a million times the sun's mass. "Some of these feeding black holes are the most luminous objects in the universe. Yet we don't know why the massive black hole in our own galaxy and similar objects are so dim."

NASA's Swift spacecraft is designed to hunt gamma-ray bursts. But in the time between these almost-daily cosmic explosions, Swift's Burst Alert Telescope (BAT) scans the sky. The survey is now the largest and most sensitive census of the high-energy X-ray sky.

Mushotzky today presented a progress report on the BAT Hard X-ray Survey at the American Astronomical Society meeting in Long Beach, Calif. "The BAT sees about half of the entire sky every day," he says. "Now we have cumulative exposures for most of the sky that exceed 10 weeks."

Galaxies that are actively forming stars have a distinctly bluish color ("blue and booming"), while those not doing so appear quite red. Nearly a decade ago, surveys with NASA's Chandra X-Ray Observatory and ESA's XMM-Newton showed that active galaxies some 7 billion light-years away were mostly massive "red and dead” galaxies in normal environments.

The BAT survey looks much closer to home, within about 600 million light-years. There, the colors of active galaxies fall midway between blue and red. Most are spiral and irregular galaxies of normal mass, and more than 30 percent are colliding. "This is roughly in line with theories that mergers shake up a galaxy and 'feed the beast' by allowing fresh gas to fall toward the black hole," Mushotzky says.

Until the BAT survey, astronomers could never be sure they were seeing most of the active galactic nuclei. An active galaxy's core is often obscured by thick clouds of dust and gas that block ultraviolet, optical and low-energy ("soft") X-ray light. Dust near the central black hole may be visible in the infrared, but so are the galaxy's star-formation regions. And seeing the black hole's radiation through dust it has heated gives us a view that is one step removed from the central engine. "We're often looking through a lot of junk," Mushotzky says.

But "hard" X-rays -- those with energies between 14,000 and 195,000 electron volts -- can penetrate the galactic gunk and allow a clear view. Dental X-rays work in this energy range.

Unlike most telescopes, the Swift's BAT contains no optics to focus incoming radiation. Instead, images are made by analyzing the shadows cast by 52,000 randomly placed lead tiles on 32,000 hard X-ray detectors.

Astronomers think that all big galaxies have a massive central black hole, but less than 10 percent of these are active today. Active galaxies are thought to be responsible for about 20 percent of all energy radiated over the life of the universe, and are thought to have had a strong influence on the way structure evolved in the cosmos.

Swift, launched in November 2004, is managed by NASA Goddard. It was built and is being operated in collaboration with Penn State, the Los Alamos National Laboratory, and General Dynamics in the U.S.; the University of Leicester and Mullard Space Sciences Laboratory in the United Kingdom; Brera Observatory and the Italian Space Agency in Italy; plus additional partners in Germany and Japan.

Francis Reddy
Goddard Space Flight Center

NASA'S Fermi Telescope Unveils a Dozen New Pulsars

NASA's Fermi Gamma-ray Space Telescope has discovered 12 new gamma-ray-only pulsars and has detected gamma-ray pulses from 18 others. The finds are transforming our understanding of how these stellar cinders work.

"We know of 1,800 pulsars, but until Fermi we saw only little wisps of energy from all but a handful of them," says Roger Romani of Stanford University, Calif. "Now, for dozens of pulsars, we're seeing the actual power of these machines."

Larger labeled image

Image above: NASA's Fermi Gamma-ray Space Telescope has found 12 previously unknown pulsars (orange). Fermi also detected gamma-ray emissions from known radio pulsars (magenta, cyan) and from known or suspected gamma-ray pulsars identified by NASA's now-defunct Compton Gamma-Ray Observatory (green). Credit: NASA/Fermi/LAT Collaboration

A new class of gamma-ray-only pulsars shows that the gamma rays must form in a broader region than the lighthouse-like radio beam. In this illustration, the pulsar's radio beams (green) never intersect Earth, but its pulsed gamma rays (magenta) do. Credit: NASA/Fermi/Cruz deWilde

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When it comes to gamma-rays, pulsars are no longer lighthouses. This image illustrates an earlier idea in which gamma-rays (magenta) arose from the neutron star's magnetic poles, where the radio beam (not shown) originates. The new pulsars Fermi discovered show this cannot be the case. Credit: NASA/Goddard Space Flight Center Conceptual Image Lab

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Isolated pulsars gradually slow their spins, but the opposite happens if the pulsar is joined by a companion star as part of a binary system. Gas accreted from the star can force the pulsar to spin faster, resulting in rotation periods of just a few milliseconds. Credit: NASA/Dana Berry

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A pulsar is a rapidly spinning and highly magnetized neutron star, the crushed core left behind when a massive sun explodes. Most were found through their pulses at radio wavelengths, which are thought to be caused by narrow, lighthouse-like beams emanating from the star's magnetic poles.

If the magnetic poles and the star's spin axis don't align exactly, the spinning pulsar sweeps the beams across the sky. Radio telescopes on Earth detect a signal if one of those beams happens to swing our way. Unfortunately, any census of pulsars is automatically biased because we only see those whose beams sweep past Earth.

"That has colored our understanding of neutron stars for 40 years," Romani says. The radio beams are easy to detect, but they represent only a few parts per million of a pulsar's total power. Its gamma rays, on the other hand, account for 10 percent or more. "For the first time, Fermi is giving us an independent look at what heavy stars do," he adds.

Pulsars are phenomenal cosmic dynamos. Through processes not fully understood, a pulsar's intense electric and magnetic fields and rapid spin accelerate particles to speeds near that of light. Gamma rays let astronomers glimpse the particle accelerator's heart.

"We used to think the gamma rays emerged near the neutron star's surface from the polar cap, where the radio beams form," says Alice Harding of NASA's Goddard Space Flight Center in Greenbelt, Md. "The new gamma-ray-only pulsars put that idea to rest." She and Romani spoke today at the American Astronomical Society meeting in Long Beach, Calif.

Astronomers now believe the pulsed gamma rays arise far above the neutron star. Particles produce gamma rays as they accelerate along arcs of open magnetic field. For the Vela pulsar, the brightest persistent gamma-ray source in the sky, the emission region is thought to lie about 300 miles from the star, which is only 20 miles across.

Existing models place the gamma-ray emission along the boundary between open and closed magnetic field lines. One version starts at high altitudes; the other implies emission from the star's surface all the way out. "So far, Fermi observations to date cannot distinguish which of these models is correct," Harding says.

Because rotation powers their emissions, isolated pulsars slow as they age. The 10,000-year-old CTA 1 pulsar, which the Fermi team announced in October, slows by about a second every 87,000 years.

Fermi also picked up pulsed gamma rays from seven millisecond pulsars, so called because they spin between 100 and 1,000 times a second. Far older than pulsars like Vela and CTA 1, these seemingly paradoxical objects get to break the rules by residing in binary systems containing a normal star. Stellar matter accreted from the companion can spin up the pulsar until its surface moves at an appreciable fraction of light speed.

NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

Francis Reddy
NASA's Goddard Space Flight Center

Gamma-Ray Burst Offers First Peek at a Young Galaxy's Star Factory

GRB 080607 exploded June 7, 2008, in the constellation Coma Berenices. The box indicates the sky area shown in the Swift image. Credit: DSS/STScI/AURA

This image merges Swift optical (blue, green) and X-ray views of GRB 080607. The white spot at center is the burst’s optical afterglow. Credit: NASA/Swift/Stefan Immler

The Peters Automated Infrared Imaging Telescope (PAIRITEL) in Arizona caught GRB 080607’s afterglow (circled) about three minutes after the explosion. The afterglow’s light has been greatly dimmed and reddened by interstellar dust in its host galaxy, 11.5 billion light years away. Credit: Adam Miller and Daniel Perley/UC Berkeley

Astronomers combining data from NASA's Swift satellite, the W. M. Keck Observatory in Hawaii, and other facilities have, for the first time, identified gas molecules in the host galaxy of a gamma-ray burst.

The explosion, designated GRB 080607, occurred in June. "This burst gave us the opportunity to 'taste' the star-forming gas in a young galaxy more than 11 billion light-years away," says University of California, Santa Cruz, professor Xavier Prochaska. The finding provides insight into star formation when the universe was about one-sixth its present age.

Gamma-ray bursts -- the universe's most luminous explosions -- create bright afterglows. Their light encodes information about the gas and dust it encounters on its way to Earth.

"We clearly see absorption from two molecular gases: hydrogen and carbon monoxide. Those are gases we associate with star-forming regions in our own galaxy," Prochaska says. The team believes that the burst exploded behind a thick molecular cloud similar to those that spawn stars in our galaxy today.

Gamma rays from GRB 080607 triggered Swift's Burst Alert Telescope shortly after 2:07 a.m. EDT on June 7, 2008. Swift calculated the burst's position, beamed the location to a network of observatories, and turned to study the afterglow.

That night, University of California, Berkeley, professor Joshua Bloom and graduate students Daniel Perley and Adam Miller were using the Low Resolution Imaging Spectrometer on the 10m Keck I Telescope in Hawaii. "Because afterglows fade rapidly, we really had to scramble when we received the alert," Perley says. "But in less than 15 minutes, we were on target and collecting data."

A pair of robotic observatories also responded quickly. The NASA-supported Peters Automated Infrared Imaging Telescope (PAIRITEL) on Mount Hopkins, Ariz., and the Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory on Mount Hamilton, Calif., observed the burst's afterglow within three minutes of Swift's alert.

The spectrum from Keck established that the explosion took place 11.5 billion light-years away. GRB 080607 blew up when the universe was just 2.2 billion years old.

The molecular cloud in the burst's host galaxy was so dense, less than 1 percent of the afterglow's light was able to penetrate it. "Intrinsically, this afterglow is the second brightest ever seen. That's the only reason we were able to observe it at all," Prochaska says.

Screening from thick molecular clouds provides a natural explanation for so-called "dark bursts," which lack associated afterglows. "We suspect that previous events like GRB 080607 were just too faint to be observed," says team member Yaron Sheffer of the University of Toledo, Ohio.

Nearly half of the absorption lines found in the Keck spectrum are unidentified. The team expects that understanding them will provide new data on the simplest space molecules.

Prochaska and Sheffer presented the findings today at the 213th meeting of the American Astronomical Society in Long Beach, Calif. A paper describing the results will appear in a future issue of Astrophysical Journal Letters.

Most gamma-ray bursts occur when massive stars run out of nuclear fuel. As the star’s core collapses into a black hole or neutron star, gas jets punch through the star and into space. Bright afterglows occur as the jets heat gas that was previously shed by the star. Because a massive star lives only a few tens of millions of years, it never drifts far from its natal cloud.

Swift, launched in November 2004, is managed by NASA's Goddard Space Flight Center in Greenbelt, Md. It was built and is being operated in collaboration with Penn State, the Los Alamos National Laboratory, and General Dynamics in the U.S.; the University of Leicester and Mullard Space Sciences Laboratory in the United Kingdom; Brera Observatory and the Italian Space Agency in Italy; plus additional partners in Germany and Japan.

Francis Reddy
Goddard Space Flight Center

Cassiopeia A Comes Alive Across Time and Space

Credit: NASA/CXC/SAO/D.Patnaude et al.(1)
Press Image and Caption

Credit: Visualization: NASA/CXC/D.Berry;

Model: NASA/CXC/MIT/T.Delaney et al.
Press Image and Caption

Two new efforts have taken a famous supernova remnant from the static to the dynamic. A new movie of data from NASA's Chandra X-ray Observatory shows changes in time never seen before in this type of object. And, an unprecedented and dramatic three-dimensional visualization of the same remnant by a separate team is being released.

Nearly ten years ago, Chandra's "First Light" image of Cassiopeia A (Cas A) revealed previously unseen structures and detail. Now, after eight years of observation, scientists have been able to construct a movie that tracks the remnant's expansion and changes over time.

"With Chandra, we have watched Cas A over a relatively small amount of its life, but so far the show has been amazing," said Daniel Patnaude of the Smithsonian Astrophysical Observatory in Cambridge, Mass. "And, we can use this to learn more about the aftermath of the star's explosion."

A separate, but equally fascinating visualization featuring Cas A was presented, along with the Patnaude team's results, at a press conference at the American Astronomical Society meeting in Long Beach, Calif. Based on data from Chandra, NASA's Spitzer Space Telescope, and ground-based optical telescopes, Tracey Delaney and her colleagues have created the first threedimensional fly-through of a supernova remnant.

Brief Time-lapse Movie of
Cassiopeia A

"We have always wanted to know how the pieces we see in two dimensions fit together with each other in real life," said Delaney of the Massachusetts Institute of Technology. "Now we can see for ourselves with this 'hologram' of supernova debris."

This ground-breaking visualization of Cas A was made possible through a collaboration with the Astronomical Medicine project based at Harvard. The goal of this project is to bring together the best techniques from two very different fields, astronomy and medical imaging.

"Right now, we are focusing on improving three-dimensional visualization in both astronomy and medicine,"said Harvard's Alyssa Goodman who heads the Astronomical Medicine project. "This project with Cas A is exactly what we have hoped would come out of it."

While these are stunning visuals, both the data movie from Patnaude and the 3-D model from Delaney are, more importantly, rich resources for science. The two teams are trying to get a much more complete understanding of how this famous supernova explosion and its remnant work.

Patnaude and his team have measured the expansion velocity of features in Cas A from motions in the movie, and find it is slower than expected based on current theoretical models. Patnaude thinks the explanation for this mysterious loss of energy is cosmic ray acceleration.

Using estimates of the properties of the supernova explosion, including its energy and dynamics, Patnaude's group show that about 30% of the energy in this supernova has gone into accelerating cosmic rays, energetic particles that are generated, in part, by supernova remnants and constantly bombard the Earth's atmosphere. The flickering in the movie provides valuable new information about where the acceleration of these particles occurs.

3-D Visualization of Cassiopeia A

Likewise, the new 3-D model of Cas A provides researchers with unique ability to study this remnant. With this new tool, Delaney and colleagues found two components to the explosion, a spherical component from the outer layers of the star and a flattened component from the inner layers of the star.

Notable features of the model are high-velocity plumes from this internal material that are shooting out from the explosion. Plumes, or jets, of silicon appear in the northeast and southwest, while plumes of iron are seen in the southeast and north. Astronomers had known about the plumes and jets before, but did not know that they all came out in a broad, disk-like structure.

The implication of this work is that astronomers who build models of supernova explosions must now consider that the outer layers of the star come off spherically, but the inner layers come out more disk like with high-velocity jets in multiple directions.

Cassiopeia A is the remains of a star thought to have exploded about 330 years ago, and is one of the youngest remnants in the Milky Way galaxy. The study of Cas A and remnants like it help astronomers better understand how the explosions that generate them seed interstellar gas with heavy elements, heat it with the energy of their radiation, and trigger blast waves from which new stars form.

Larry Rudnick, from the University of Minnesota, led the Spitzer part of the Delaney study. NASA's Marshall Space Flight Center, Huntsville, Ala., manages the Chandra program for the agency's Science Mission Directorate. The Smithsonian Astrophysical Observatory controls science and flight operations from the Chandra X-ray Center in Cambridge, Mass.

(1) Fast Facts for Cassiopeia A:
Scale	Image is 8.4 arcmin across
Category	Supernovas & Supernova Remnants
Coordinates (J2000)	RA 23h 23m 26.7s | Dec +58° 49' 03.00"
Constellation	Cassiopeia
Observation Dates	01/30/2000 - 12/08/2007 with 5 pointings
Observation Time	56 hours
Obs. IDs	114, 1952, 5196, 9117, 9773
Color Code	Energy (Red (0.5-1.5 keV); Green (1.5-3.0 keV); Blue (4.0-6.0 keV))
Instrument	ACIS
Also Known As	Cas A
Distance Estimate	About 10,000 light years

Media contacts:

Jennifer Morcone
Marshall Space Flight Center, Huntsville, Ala.
256-544-7199
jennifer.j.morcone@nasa.gov

Megan Watzke
Chandra X-ray Center, Cambridge, Mass.
617-496-7998
cxcpress@cfa.harvard.edu

Additional information and images are available at:
http://chandra.harvard.edu/
http://chandra.nasa.gov
and
http:// am.iic.harvard.edu

Star Light, Star Bright, Its Explanation is Out of Sightv

Credit: NASA, ESA, and K. Barbary
(University of California, Berkeley/Lawrence Berkeley National Lab,
Supernova Cosmology Project)

A mysterious flash of light from somewhere near or far in the universe is still keeping astronomers in the dark long after it was first detected by NASA's Hubble Space Telescope in 2006. It might represent an entirely new class of stellar phenomena that has previously gone undetected in the universe, say researchers.

Astronomers commonly observe intense flashes of light from a variety of stellar explosions and outbursts, such as novae and supernovae. Hubble discovered the cosmic flash on February 21, 2006. It steadily rose in brightness for 100 days, and then dimmed back to oblivion after another 100 days.

The rise and fall in brightness has a signature that simply has never been recorded for any other type of celestial event. Supernovae peak after no more than 70 days, and gravitational lensing events are much shorter. Therefore, this observation defies a simple explanation, reports Kyle Barbary of the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, Calif. He is describing the bizarre Hubble observation at the 213th meeting of the American Astronomical Society in Long Beach, Calif. "We have never seen anything like it," he concludes.

The spectral fingerprints of light coming from the object, cataloged as SCP 06F6, also have eluded identification as being due to any specific element. One guess is that the features are redshifted molecular carbon absorption lines in a star roughly one billion light-years away.

But searches through various astronomical survey catalogs for the source of the light have not uncovered any evidence for a star or galaxy at the location of the flash. The Supernova Cosmology Project at LBNL discovered it serendipitously in a search for supernovae.

Hubble was aimed at a cluster of galaxies 8 billion light-years away in the spring constellation Bootes. But the mystery object could be anywhere in between, even in the halo of our own Milky Way galaxy.

Papers published by other researchers since the event was reported in June 2006, have suggested a bizarre zoo of possibilities: the core collapse and explosion of a carbon rich star, a collision between a white dwarf and an asteroid, or the collision of a white dwarf with a black hole.

But Barbary does not believe that any model offered so far fully explains the observations. "I don't think we really know what the discovery means until we can observe similar objects in the future."

All-sky surveys for variable phenomena, such as those to be conducted with the planned Large Synoptic Survey Telescope, may ultimately find similar transient events in the universe.

CONTACT:
Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu

Kyle Barbary
University of California Berkeley/Lawrence Berkeley National Lab, Berkeley, Calif.
510-486-4652
kbarbary@berkeley.edu / kbarbary@lbl.gov

Brown Dwarfs Don't Hang Out With Stars

Credit: NASA, ESA, and M. Stumpf (Max-Planck-Institute for Astronomy)

Brown dwarfs, objects that are less massive than stars but larger than planets, just got more elusive, based on a study of 233 nearby multiple-star systems by NASA's Hubble Space Telescope. Hubble found only two brown dwarfs as companions to normal stars. This means the so-called "brown dwarf desert" (the absence of brown dwarfs around solar-type stars) extends to the smallest stars in the universe.

Sergio Dieterich of Georgia State University in Atlanta and team leader of the study is reporting the results today at the 213th meeting of the American Astronomical Society (AAS) in Long Beach, Calif.

"We still did not find brown dwarfs around small red stars whose mass is only slightly above the hydrogen burning limit. Especially when we consider the fact that brown dwarfs binaries do exist, the fact that there are very few binaries whose components lie on different sides of the hydrogen burning limit is significant," says Dieterich.

The 233 stars surveyed are part of the RECONS (Research Consortium on Nearby Stars) survey meant to understand the nature of the sun's nearest stellar neighbors, both individually and as a population. The current primary goals are to discover and characterize "missing" members of the sample of stars within 32.6 light-years (10 parsecs) of Earth.

RECONS searches for nearby stars through analyzing existing all-sky surveys, combined with observations by a variety of telescopes in both hemispheres. A total of 12 brown dwarfs are currently known within 32.6 light-years of Earth, as compared to 239 red dwarf stars (stars that are largely 20 percent the mass of our sun and are roughly half its diameter and temperature).

In fact, the number of known brown dwarfs is close to that of known extrasolar planets. However, the number of exoplanets known in this region so far is very likely only a lower limit as smaller-mass exoplanets are not within our capability of detection at present.

The Hubble survey, taken with Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS), provides strong statistics pointing to the fact that brown dwarfs do not exist around even the least massive stars. "If mass ratio was the driving factor we would expect to find more brown dwarfs around small red stars than around solar type stars," says Dieterich.

These results are complementary to another study also being reported at the AAS meeting by Micaela Stumpf of the Max-Planck-Institute for Astronomy in Heidelberg, Germany. The results imply that brown dwarfs tend to hang out with their own kind.

Nearly ten years' worth of NICMOS observations, combined with recent ground-based adaptive optics results, have provided a first estimate of the orbit of the double brown dwarf system Kelu-1 AB. The eccentric orbit is tilted nearly edge-on to Earth and the dwarfs complete an orbit every 38 years.

Based on the orbital dynamics, the total mass of the system is estimated to be 184 Jupiter masses. But, based on spectroscopic and photometric measurements, the two brown dwarfs are no larger than 61 and 50 Jupiter masses, respectively (a star is no smaller than 75 Jupiter masses). Stumpf is reporting that there may in fact be a third member of the system to account for the "missing mass." This would make it potentially the first-ever confirmed triple brown dwarf system.

All-sky surveys planned for the next decade, with advanced telescopes like the Large Synoptic Survey Telescope, promise to ultimately solve the puzzle of the "brown dwarf desert" by doing deep infrared searches for the underlying brown dwarf population.

Contact:

Ray Villard
Space Telescope Science Institute, Baltimore, Md.
410-338-4514
villard@stsci.edu

Sergio Dieterich
Georgia State University, Atlanta, Ga.
404-413-6024
dieterich@chara.gsu.edu

Todd Henry
Georgia State University, Atlanta, Ga.
404-413-6054
thenry@chara.gsu.edu

Micaela Stumpf
Max-Planck-Institute for Astronomy, Heidelberg, Germany
011-49-6221-528-221
stumpf@mpia-hd.mpg.de

Hubble Views Galactic Core in Unprecedented New Detail

Credit for Hubble image: NASA, ESA, and Q.D. Wang (University of Massachusetts, Amherst) Credit for Spitzer image: NASA, Jet Propulsion Laboratory, and S. Stolovy (Spitzer Science Center/Caltech)

This composite color infrared image of the center of our Milky Way galaxy reveals a new population of massive stars and new details in complex structures in the hot ionized gas swirling around the central 300 light-years. This sweeping panorama is the sharpest infrared picture ever made of the Galactic core. It offers a nearby laboratory for how massive stars form and influence their environment in the often violent nuclear regions of other galaxies.

This view combines the sharp imaging of the Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) with color imagery from a previous Spitzer Space Telescope survey done with its Infrared Astronomy Camera (IRAC). The Galactic core is obscured in visible light by intervening dust clouds, but infrared light penetrates the dust.

The spatial resolution of the NICMOS image corresponds to 0.025 light-years at the distance of the Galactic core of 26,000 light-years. Hubble reveals details in objects as small as 20 times the size of our own solar system.

The NICMOS mosaic image represents the largest piece of sky ever mapped for one NICMOS observing program. It was combined with a full-color Spitzer image to yield a color composite of the nuclear region. The picture measures 300 x 115 light-years. Outside the boundary of the NICMOS survey, the IRAC exposures (which are 1/10th as sharp) can be seen at wavelengths of 3.6 microns (shown as blue), 4.5 microns (shown as green), 5.8 microns (shown as orange), and 8.0 microns (shown as red).

The new NICMOS data show the glow from ionized hydrogen gas as well as a multitude of stars. Hubble reveals an important population of stars with strong stellar winds, signified by excess emission from ionized gas at one infrared wavelength (1.87 microns) compared to another slightly different wavelength (1.90 microns).

NICMOS shows a large number of these massive stars distributed throughout the region. A new finding is that astronomers now see that the massive stars are not confined to one of the three known clusters of massive stars in the Galactic Center, known as the Central cluster, the Arches cluster, and the Quintuplet cluster. These three clusters are easily seen as tight concentrations of bright, massive stars in the NICMOS image. The distributed stars may have formed in isolation, or they may have originated in clusters that have been disrupted by strong gravitational tidal forces.

The winds and radiation from these stars form the complex structures seen in the core, and in some cases, they may be triggering new generations of stars. At upper left, large arcs of ionized gas are resolved into arrays of intriguingly organized linear filaments indicating perhaps a critical role of the influence of locally strong magnetic fields.

The lower left region shows pillars of gas sculpted by winds from hot massive stars in the Quintuplet cluster. At the center of the image, ionized gas surrounding the supermassive black hole at the center of the galaxy is confined to a bright spiral embedded within a circum-nuclear dusty inner-tube-shaped torus.

The NICMOS mosaic required 144 Hubble orbits to make 2,304 science exposures. It was taken between February 22 and June 5, 2008.

Milky Way a Swifter Spinner, More Massive, New Measurements Show

This artist's conception of the Milky Way shows the four-arm spiral structure confirmed by recent VLBA distance measurements (shown by green and blue dots). The data show that the Milky Way is spinning faster than previously believed. Our galaxy therefore is more massive than astronomers thought, matching Andromeda's heft. Red dots mark the galactic center and the location of our solar system. Credit: Robert Hurt, IPAC; Mark Reid, CfA, NRAO/AUI/NSF

Fasten your seat belts -- we're faster, heavier, and more likely to collide than we thought. Astronomers making high-precision measurements of the Milky Way say our Galaxy is rotating about 100,000 miles per hour faster than previously understood.

That increase in speed, said Mark Reid of the Harvard-Smithsonian Center for Astrophysics, increases the Milky Way's mass by 50 percent, bringing it even with the Andromeda Galaxy. "No longer will we think of the Milky Way as the little sister of the Andromeda Galaxy in our Local Group family."

The larger mass, in turn, means a greater gravitational pull that increases the likelihood of collisions with the Andromeda galaxy or smaller nearby galaxies.

Our solar system is about 28,000 light-years from the Milky Way’s center. At that distance, the new observations indicate, we’re moving at about 600,000 miles per hour in our Galactic orbit, up from the previous estimate of 500,000 miles per hour.

The scientists are using the National Science Foundation’s Very Long Baseline Array (VLBA) radio telescope to remake the map of the Milky Way. Taking advantage of the VLBA’s unparalleled ability to make extremely detailed images, the team is conducting a long-term program to measure distances and motions in our Galaxy. They reported their results at the American Astronomical Society’s meeting in Long Beach, California.

The scientists observed regions of prolific star formation across the Galaxy. In areas within these regions, gas molecules are strengthening naturally-occurring radio emission in the same way that lasers strengthen light beams. These areas, called cosmic masers, serve as bright landmarks for the sharp radio vision of the VLBA. By observing these regions repeatedly at times when the Earth is at opposite sides of its orbit around the Sun, the astronomers can measure the slight apparent shift of the object’s position against the background of more distant objects.

“The new VLBA observations of the Milky Way are producing highly-accurate direct measurements of distances and motions,” said Karl Menten of the Max Planck Institute for Radio Astronomy in Germany, a member of the team. “These measurements use the traditional surveyor’s method of triangulation and do not depend on any assumptions based on other properties, such as brightness, unlike earlier studies.”

The astronomers found that their direct distance measurements differed from earlier, indirect measurements, sometimes by as much as a factor of two. The star-forming regions harboring the cosmic masers “define the spiral arms of the Galaxy,” Reid explained. Measuring the distances to these regions thus provides a yardstick for mapping the Galaxy’s spiral structure.

“These direct measurements are revising our understanding of the structure and motions of our Galaxy,” Menten said. "Because we’re inside it, it’s difficult for us to determine the Milky Way’s structure. For other galaxies, we can simply look at them and see their structure, but we can’t do this to get an overall image of the Milky Way. We have to deduce its structure by measuring and mapping,” he added.

The VLBA can fix positions in the sky so accurately that the actual motion of the objects can be detected as they orbit the Milky Way’s center. Adding in measurements of motion along the line of sight, determined from shifts in the frequency of the masers’ radio emission, the astronomers are able to determine the full 3-dimensional motions of the star-forming regions. Using this information, Reid reported that “most star-forming regions do not follow a circular path as they orbit the Galaxy; instead we find them moving more slowly than other regions and on elliptical, not circular, orbits.”

The researchers attribute this to what they call spiral density-wave shocks, which can take gas in a circular orbit, compress it to form stars, and cause it to go into a new, elliptical orbit. This, they explained, helps to reinforce the spiral structure.

Reid and his colleagues found other surprises, too. Measuring the distances to multiple regions in a single spiral arm allowed them to calculate the angle of the arm. “These measurements,” Reid said, “indicate that our Galaxy probably has four, not two, spiral arms of gas and dust that are forming stars.” Recent surveys by NASA’s Spitzer Space Telescope suggest that older stars reside mostly in two spiral arms, raising a question of why the older stars don't appear in all the arms. Answering that question, the astronomers say, will require more measurements and a deeper understanding of how the Galaxy works.

The VLBA, a system of 10 radio-telescope antennas stretching from Hawaii to New England and the Caribbean, provides the best ability to see the finest detail, called resolving power, of any astronomical tool in the world. The VLBA can routinely produce images hundreds of times more detailed than those produced by the Hubble Space Telescope. The VLBA’s tremendous resolving power, equal to being able to read a newspaper in Los Angeles from the distance of New York, is what permits the astronomers to make precise distance determinations.

This release was issued jointly with the National Radio Astronomy Observatory. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
daguilar@cfa.harvard.edu

Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu

Dave Finley
NRAO
575-835-7302
dfinley@nrao.edu

HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS

Baby Jupiters Must Gain Weight Fast

About this image: This photograph from NASA's Spitzer Space Telescope shows the young star cluster NGC 2362. By studying it, astronomers found that gas giant planet formation happens very rapidly and efficiently, within less than 5 million years, meaning that Jupiter-like worlds experience a growth spurt in their infancy. Credit: NASA/JPL-Caltech/T. Currie (CfA)

The planet Jupiter gained weight in a hurry during its infancy. It had to, since the material from which it formed probably disappeared in just a few million years, according to a new study of planet formation around young stars.

Smithsonian astronomers examined the 5 million-year-old star cluster NGC 2362 with NASA's Spitzer Space Telescope, which can detect the signatures of actively forming planets in infrared light. They found that all stars with the mass of the Sun or greater have lost their protoplanetary (planet-forming) disks. Only a few stars less massive than the Sun retain their protoplanetary disks. These disks provide the raw material for forming gas giants like Jupiter. Therefore, gas giants have to form in less than 5 million years or they probably won't form at all.

“Even though astronomers have detected hundreds of Jupiter-mass planets around other stars, our results suggest that such planets must form extremely fast. Whatever process is responsible for forming Jupiters has to be incredibly efficient,” said lead researcher Thayne Currie of the Harvard-Smithsonian Center for Astrophysics. Currie presented the team’s findings at a meeting of the American Astronomical Society in Long Beach, Calif.

Even though nearly all gas giant-forming disks in NGC 2362 have disappeared, several stars in the cluster have “debris disks,” which indicates that smaller rocky or icy bodies such as Earth, Mars, or Pluto may still be forming.

“The Earth got going sooner, but Jupiter finished first, thanks to a big growth spurt,” explained co-author Scott Kenyon.

Kenyon added that while Earth took about 20 to 30 million years to reach its final mass, Jupiter was fully grown in only 2 to 3 million years.

Previous studies indicated that protoplanetary disks disappear within 10 million years. The new findings put even tighter constraints on the time available to create gas giant planets around stars of various masses.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. Caltech manages JPL for NASA.

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

David A. Aguilar  
Director of Public Affairs Harvard-Smithsonian Center for Astrophysics  
617-495-7462
daguilar@cfa.harvard.edu

Christine Pulliam 
Public Affairs Specialist Harvard-Smithsonian Center for Astrophysics  
617-495-7463
cpulliam@cfa.harvard.eduv

HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS

Stars Forming Just Beyond Black Hole's Grasp at Galactic Center

About this image: This artist's concept shows young, blue stars encircling a supermassive black hole at the core of a spiral galaxy like the Milky Way. The background stars are the typical older, redder population of stars that inhabit the cores of most galaxies (including our own). CfA astronomers caught two stars in the act of forming within a few light-years of the Milky Way's center. Their find demonstrates that stars can form at our galaxy's core despite the powerful gravitational tides generated by the black hole. Credit: NASA, ESA, and A. Schaller (for STScI)

About this image: This 0.6 by 0.7-degree infrared photograph of the galactic center shows a large population of old, red stars. However, the discovery of two young protostars within a few light-years of the center of the Milky Way shows that stars can form there despite powerful gravitational tides due to the supermassive black hole. Credit: 2MASS/E. Kopan (IPAC/Caltech)

The center of the Milky Way presents astronomers with a paradox: it holds young stars, but no one is sure how those stars got there. The galactic center is wracked with powerful gravitational tides stirred by a 4 million solar-mass black hole. Those tides should rip apart molecular clouds that act as stellar nurseries, preventing stars from forming in place. Yet the alternative – stars falling inward after forming elsewhere – should be a rare occurrence.

Using the Very Large Array of radio telescopes, astronomers from the Harvard-Smithsonian Center for Astrophysics and the Max Planck Institute for Radio Astronomy have identified two protostars located only a few light-years from the galactic center. Their discovery shows that stars can, in fact, form very close to the Milky Way’s central black hole.

“We literally caught these stars in the act of forming,” said Smithsonian astronomer Elizabeth Humphreys. She presented the finding today at a meeting of the American Astronomical Society in Long Beach, Calif.

The center of the Milky Way is a mysterious region hidden behind intervening dust and gas, making it hard to study. Visible light doesn’t make it out, leaving astronomers no choice but to use other wavelengths like infrared and radio, which can penetrate dust more easily.

Humphreys and her colleagues searched for water masers—radio signals that serve as signposts for protostars still embedded in their birth cocoons. They found two protostars located seven and 10 light-years from the galactic center. Combined with one previously identified protostar, the three examples show that star formation is taking place near the Milky Way’s core.

Their finding suggests that molecular gas at the center of our galaxy must be denser than previously believed. A higher density would make it easier for a molecular cloud’s self-gravity to overcome tides from the black hole, allowing it to not only hold together but also collapse and form new stars.

The discovery of these protostars corroborates recent theoretical work, in which a supercomputer simulation produced star formation within a few light-years of the Milky Way’s central black hole.

“We don’t understand the environment at the galactic center very well yet,” Humphreys said. “By combining observational studies like ours with theoretical work, we hope to get a better handle on what’s happening at our galaxy’s core. Then, we can extrapolate to more distant galaxies.”

Humphreys’ co-authors are Mark Reid (Harvard-Smithsonian Center for Astrophysics) and Karl Menten (Max Planck Institute for Radio Astronomy).

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

For more information, contact:

David A. Aguilar
Director of Public Affairs
Harvard-Smithsonian Center for Astrophysics
617-495-7462
daguilar@cfa.harvard.edu

Christine Pulliam
Public Affairs Specialist
Harvard-Smithsonian Center for Astrophysics
617-495-7463
cpulliam@cfa.harvard.edu

HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS

Dead Stars Tell Story of Planet Birth

Asteroid 'Bites the Dust' Around Dead Star
Credit: NASA/JPL-Caltech

Silicates in Alien Asteroids
Credit: NASA/JPL-Caltech/UCLA

About this image: This plot of data from NASA's Spitzer Space Telescopes shows that asteroid dust around a dead "white dwarf" star contains silicates -- a common mineral on Earth. The data were taken primarily by Spitzer's infrared spectrograph, an instrument that breaks light apart into its basic constituents. The yellow dots show averaged data from the spectrograph, while the orange triangles show older data from Spitzer's infrared array camera. The white dwarf is called GD 40.

Astronomers have turned to an unexpected place to study the evolution of planets -- dead stars.

Observations made with NASA's Spitzer Space Telescope reveal six dead "white dwarf" stars littered with the remains of shredded asteroids. This might sound pretty bleak, but it turns out the chewed-up asteroids are teaching astronomers about the building materials of planets around other stars.

So far, the results suggest that the same materials that make up Earth and our solar system's other rocky bodies could be common in the universe. If the materials are common, then rocky planets could be, too.

"If you ground up our asteroids and rocky planets, you would get the same type of dust we are seeing in these star systems," said Michael Jura of the University of California, Los Angeles, who presented the results today at the American Astronomical Society meeting in Long Beach, Calif. "This tells us that the stars have asteroids like ours -- and therefore could also have rocky planets." Jura is the lead author of a paper on the findings accepted for publication in the Astronomical Journal.

Asteroids and planets form out of dusty material that swirls around young stars. The dust sticks together, forming clumps and eventually full-grown planets. Asteroids are the leftover debris. When a star like our sun nears the end of its life, it puffs up into a red giant that consumes its innermost planets, while jostling the orbits of remaining asteroids and outer planets. As the star continues to die, it blows off its outer layers and shrinks down into a skeleton of its former self -- a white dwarf.

Sometimes, a jostled asteroid wanders too close to a white dwarf and meets its demise -- the gravity of the white dwarf shreds the asteroid to pieces. A similar thing happened to Comet Shoemaker Levy 9 when Jupiter's gravity tore it up, before the comet ultimately smashed into the planet in 1994.

Spitzer observed shredded asteroid pieces around white dwarfs with its infrared spectrograph, an instrument that breaks light apart into a rainbow of wavelengths, revealing imprints of chemicals. Previously, Spitzer analyzed the asteroid dust around two so-called polluted white dwarfs; the new observations bring the total to eight.

"Now, we've got a bigger sample of these polluted white dwarfs, so we know these types of events are not extremely rare," said Jura.

In all eight systems observed, Spitzer found that the dust contains a glassy silicate mineral similar to olivine and commonly found on Earth. "This is one clue that the rocky material around these stars has evolved very much like our own," said Jura.

The Spitzer data also suggest there is no carbon in the rocky debris -- again like the asteroids and rocky planets in our solar system, which have relatively little carbon.

A single asteroid is thought to have broken apart within the last million years or so in each of the eight white-dwarf systems. The biggest of the bunch was once about 200 kilometers (124 miles) in diameter, a bit larger than Los Angeles County.

Jura says the real power of observing these white dwarf systems is still to come. When an asteroid "bites the dust" around a dead star, it breaks into very tiny pieces. Asteroid dust around living stars, by contrast, is made of larger particles. By continuing to use spectrographs to analyze the visible light from this fine dust, astronomers will be able to see exquisite details -- including information about what elements are present and in what abundance. This will reveal much more about how other star systems sort and process their planetary materials.

"It's as if the white dwarfs separate the dust apart for us," said Jura.

Other authors are Ben Zuckerman at the University of California, Los Angeles, and Jay Farihi at Leicester University, England.

Whitney Clavin 818-354-4673
Jet Propulsion Laboratory
whitney.clavin@jpl.nasa.gov

The Universe is yours to discover during the International Year of Astronomy 2009

With 2009 just over the horizon, stargazers around the world are busy preparing for the International Year of Astronomy. A staggering 135 nations are collaborating to bring the Universe closer to Earth. Events and activities will take place over the coming 365 days and beyond, in a spectacle of cosmic proportions.

The International Year of Astronomy 2009 (IYA2009) has been launched by the International Astronomical Union (IAU) and the United Nations Educational, Scientific and Cultural Organization (UNESCO) under the theme, "The Universe, yours to discover". Thousands of IYA2009 events are described on the national websites, as well as on astronomy2009.org, and a few of the global projects are listed here.

The official IYA2009 Opening Ceremony will take place in Paris on 15 and 16 January 2009, and the press is invited to attend. It will feature keynote speakers, including Nobel Laureates, and live video feeds to scientists working in remote locations. Many nations are holding their own Opening Ceremonies in January and February, showing their dedication to the Year. But events will begin before then. Don't be surprised to see telescopes on the streets on New Year's Day. The IYA2009 Solar Physics Group have been busy planning a grand worldwide campaign, with over 30 countries involved at more than 150 venues, which will see amateur stargazers set up their telescopes on pavements as well as in science centres, letting passers-by observe the Sun using special safety equipment.

The Cosmic Diary is an example of a global activity occurring during 2009, with the release of its official website on New Year's Day. The project concerns the daily lives of full-time astronomers. More than 50 bloggers, professionals from over 35 countries and employed by organisations such as ESO, NASA, ESA and JAXA have already begun producing content, writing about their lives, the work they conduct and the challenges they face. The public can see what being an astronomer is really like, and how ground-breaking research is conducted. Another project, 365 Days of Astronomy, will publish one podcast per day over the entire year. The episodes will be written, recorded and produced by people around the world.

100 Hours of Astronomy, another IYA2009 Cornerstone Project, is a worldwide event taking place from 2-5 April 2009, with a wide range of public outreach activities including live webcasts, observing events and more. One of the key goals of 100 Hours of Astronomy is to have as many people as possible look through a telescope, just as Galileo did for the first time 400 years ago.

The From Earth to the Universe (FETTU) Cornerstone Project is an exhibition arranged by IYA2009 that will bring large-scale astronomical images to a wide public audience in non-traditional venues such as public parks and gardens, art museums, shopping malls and metro stations. Over 30 countries around the world are currently in the development phase of FETTU projects, many with multiple locations. Some 15 countries plan to begin FETTU exhibitions within the first month of 2009, ranging in size from 25 to over 100 images on display. FETTU will be introduced to the global community at the Opening Ceremony at UNESCO headquarters in January 2009.

The World at Night is an IYA2009 Special Project that is producing and bringing to the public a collection of stunning photographs and time-lapse videos of the world's landmarks with the sky in the background. The World at Night is preparing more than 30 exhibitions and educational events around the world.

One of IYA2009's aims is to raise awareness of light pollution, and how the beauty of the night sky is progressively being drowned out, particularly over urban areas. The project Dark Skies Awareness is tackling these issues head-on in a practical, inclusive manner. One way in which it is doing this is by holding star-counting events, where the public are encouraged to see how many stars in a particular area of the sky are actually visible from their location. When compared with data from truly dark sites, the results are often very surprising! The "How Many Stars" event will run from January 2009.

A list of event highlights is available on the official IYA2009 website, www.astronomy2009.org/highlights. From there it is also possible to contact the National Nodes, responsible for organising local events in the many participating countries.

During 2009, the sky will provide some exciting events, including the longest total solar eclipse of the 21st century, occurring on 22 July 2009 and lasting 6 minutes 39 seconds over a narrow corridor through countries including India, Bangladesh and China. A strong shower of Leonid meteors is also expected in mid-November 2009, with forecasters predicting upwards of an incredible 500 shooting stars per hour. In mid-October in the northern hemisphere, Jupiter will be placed at dusk, a perfect time to show public the giant planet and its moons. These are an impressive sight through even a small amateur telescope.

IYA2009 seeks to involve the public at large in its activities, and to this end amateur astronomers have been called upon to help organise and run events. Known for their enthusiasm, this army of helpers is growing every day, preparing to promote astronomy in a stunning variety of ways. In fact, so many thousands of people across the globe are already involved, they have formed the world's largest ever astronomy network.

Catherine Cesarsky, IAU President, says: "135 countries have committed themselves to the Year, all pulling together toward the common aim of making astronomy accessible to the public. IYA2009 will reinforce the links between science education and science careers, stimulating a long-term increase in student enrolment in the fields of science and technology and an appreciation for lifelong learning."

With such a range of activities planned, now is the ideal time to learn more about the cosmos and our place within it. The International Year of Astronomy 2009 promises to make the Universe yours to discover, beginning on 1 January 2009.


Notes for editors

IYA2009 marks the 400th anniversary of Galileo Galilei's first astronomical observation through a telescope. It is nothing short of a worldwide celebration, promoting astronomy and its contribution to society and culture, with events at regional, national, and global levels.

The IAU is the international astronomical organisation that brings together almost 10 000 distinguished astronomers from all nations of the world. Its mission is to promote and safeguard the science of astronomy in all its aspects through international cooperation. The IAU also serves as the internationally recognised authority for assigning designations to celestial bodies and surface features on them. Founded in 1919, the IAU is the world's largest professional body for astronomers.

IYA2009 welcome video: A special welcome video for IYA2009 is available. Hosted by Catherine Cesarsky, President of the International Astronomical Union, it is approximately five minutes in length and available in English, French and Spanish. The video is available for download from www.astronomy2009.org.


Additional information:

IYA2009 website: www.astronomy2009.org

IYA2009 Opening Events: www.astronomy2009.org/events

Opening Ceremony Media accreditation: www.astronomy2009.org/opening

UNESCO IYA2009 website: www.unesco.org/iya2009

Opening Ceremony website: http://www.astronomy2009.org/opening

Dawn of IYA2009 (Solar Physics Group) website: www.solarastronomy2009.org

Cosmic Diary website (active 1 January 2009): www.cosmicdiary.org

365 Days of Astronomy: http://365daysofastronomy.org

100 Hours of Astronomy: www.100hoursofastronomy.org

From Earth To The Universe: www.fromearthtotheuniverse.org

Dark Skies Awareness: www.darkskiesawareness.org

The World at Night: www.twanight.org

International Astronomical Union website: www.iau.org

IYA2009 welcome video: www.astronomy2009.org/resources/multimedia/videos/

For more information:

IAU IYA2009 Coordinator

Pedro Russo

ESO ePOD

Karl-Schwarzschild-Strasse 2

D-85748 Garching bei München

Germany

Tel: +49 89 320 06 195

Cell: +351 96285 4775 / +49 17661100211

Fax: +49 89 320 23 62

E-mail: prusso@eso.org

Further contacts

Yolanda Berenguer

UNESCO Focal Point for the International Year of Astronomy 2009

UNESCO HQ, Paris

Tel: +33-1-45684171

E-mail: y.berenguer@unesco.org

Dr. Karel A. van der Hucht

General Secretary, International Astronomical Union

IAU Secretariat, Paris, France

Tel: +33-1-43-25-83-58

E-mail: K.A.van.der.Hucht@sron.nl

IAU Press Officer

Lars Lindberg Christensen

ESO ePOD, Garching, Germany

Tel: +49 89 3200 6761

Cellular: +49-173-3872-621

E-mail: lars@eso.org