Inception of the Virus-W spectrograph

Fig. 1: "First Light" for VIRUS-W: This image (from the Sloan Digital Sky Survey) shows the galaxy NGC2903 and the field of view of the spectrograph.
Credit: SDSS

By McDonald Observatory at University of Texas, Austin, Max Planck Institute, Garching, Germany

Published: January 28, 2011

The new observing instrument VIRUS-W, built by the Max Planck Institute for Extraterrestrial Physics and the University Observatory Munich, Germany, saw "first light" November 10, 2010, on McDonald Observatory's 2.7-meter Harlan J. Smith Telescope in West Texas. Its first images of a spiral galaxy about 30 million light-years away were an impressive confirmation of the capabilities of the instrument, which can determine the motion of stars in nearby galaxies to a precision of a few miles per second.

"When we attached VIRUS-W around midnight on November 10 to the 2.7-meter telescope, we were very happy to see that the data delivered by VIRUS-W was of science quality virtually from the first moment on," said Maximilian Fabricius from the Max Planck Institute for Extraterrestrial Physics.

"As the first galaxy to observe, we had selected the strongly barred galaxy NGC 2903 at a distance of about 30 million light-years — right in front of our doorstep. The data we collected reveal a centrally increasing velocity dispersion from about 50 miles per second (80 km/s) to 75 mps (120 km/s) within the field of view of the instrument. This was a very exciting moment and only possible because of the remarkable teamwork during the commissioning with a lot of support by the observatory staff."

As an integral field spectrograph, VIRUS-W can simultaneously produce 267 individual spectra — one for each of its glass fibers. By dispersing the light into its constituent colors, astronomers are able to study properties such as the velocity distribution of the stars in a galaxy. For this, they use the Doppler shift, which means that the light from stars moving toward or away from us is shifted to blue or red wavelengths, respectively. This effect can also be observed on Earth when a fast vehicle, such as a racing car, is driving past — the sound of the approaching car is higher, while for the departing car it is lower.

VIRUS-W´s unique feature is the combination of a large field of view (about 1 by 2 arcminutes) with a relatively high spectral resolution. With the large field of view, astronomers can study nearby galaxies in just one or a few pointings, while the high spectral resolution permits an accurate determination of the velocity dispersion in these objects. In this way, astronomers obtain the large-scale kinematic structure of nearby spiral galaxies, which will give important insight into their formation history.

Most galaxies are too distant, and the separation between their billions upon billions of stars too small, to resolve with even the best cutting-edge instruments. Astronomers, therefore, cannot study individual stars in these distant galaxies, but only the average motion along a specific line of sight.

The measured velocity distributions are characterized by two parameters: The mean velocity reveals the large-scale motion of the stars along the line of sight, and the velocity dispersion measures how much the velocities of the individual stars differ from this mean velocity. If the stars have more or less the same velocity, the dispersion is small, but if they have very different velocities, the dispersion is broad. For spiral galaxies where the stars travel in fairly regular circular orbits, the velocity dispersion is mostly small. In elliptical galaxies, however, the stars have rather disordered orbits and so the dispersion is broad.

With the high spectral resolution of VIRUS-W, astronomers can investigate relatively small velocity dispersions down to about 12 mps (20 km/s). This was confirmed by the first images taken by VIRUS-W of the nearby spiral galaxy NGC 2903.

The observing time at the telescope was made available by the VIRUS-P Exploration of Nearby Galaxies (VENGA) project, and VIRUS-W will be contributing from the beginning of 2011 onward.

The VIRUS-P instrument, on which VIRUS-W is based, has probed these 30 galaxies in a wide range of wavelengths, from ultraviolet light all the way into the red portion of the visible spectrum. This wide wavelength range allows astronomers to probe a large number of questions about these galaxies, from their star formation rate to their ages.

"VIRUS-W is an improved version of VIRUS-P," Guillermo Blanc from the University of Texas at Austin said. Astronomers will follow up the VIRUS-P studies by using VIRUS-W to look into the hearts of the brightest spiral galaxies in the sample to get what Blanc calls "exquisite measurements" of the motions of stars and gas clouds inside these galaxies. Understanding how stars and gas move will help astronomers better understand how stars form.

VIRUS-P is a prototype of the Visible Integral-field Replicable Unit Spectrograph (VIRUS) being developed for a large dark energy study called the Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) led by The University of Texas at Austin. For a study of the large-scale distribution of galaxies, HETDEX will combine about 100 spectrographs at the 9.2-meter Hobby-Eberly Telescope at McDonald Observatory to form one large instrument. VIRUS-W — the W stands for a later mission at the Wendelstein telescope of the Munich Observatory — is based on the same basic VIRUS design.

University of Texas astronomers "Weigh" Heaviest Known Black Hole in our Cosmic Neighborhood

Artist's concept of what a future telescope might see in looking at the black hole at the heart of the galaxy M87. Clumpy gas swirls around the black hole in an accretion disk, feeding the central beast. The black area at center is the black hole itself, defined by the event horizon, beyond which nothing can escape. The bright blue jet shooting from the region of the black hole is created by gas that never made it into the hole itself but was instead funneled into a very energetic jet.

Credit: Gemini Observatory/AURA illustration by Lynette Cook

By McDonald Observatory at University of Texas, Austin —
Published: January 13, 2011

Seattle — Astronomers led by Karl Gebhardt of The University of Texas at Austin have measured the most massive known black hole in our cosmic neighborhood by combining data from a giant telescope in Hawai'i and a smaller telescope in Texas.

The result is an ironclad mass of 6.6 billion suns for the black hole in the giant elliptical galaxy M87. This enormous mass is the largest ever measured for a black hole using a direct technique. Given its massive size, M87 is the best candidate for future studies to "see" a black hole for the first time, rather than relying on indirect evidence of their existence as astronomers have for decades.
The results will be presented in a news conference today at the 217th meeting of the American Astronomical Society in Seattle. Two papers detailing the results will be published soon in The Astrophysical Journal.

Gebhardt, the Herman and Joan Suit Professor of Astrophysics, led a team of researchers using the 8-meter Gemini North telescope in Hawai'i to probe the motions of stars around the black hole in the center of the massive galaxy M87.

University of Texas at Austin graduate student Jeremy Murphy has used the Harlan J. Smith Telescope at the university's McDonald Observatory in West Texas to probe the outer reaches of the galaxy — the so-called "dark halo." The dark halo is a region surrounding the galaxy filled with "dark matter," an unknown type of mass that gives off no light but is detectable by its gravitational effect on other objects.

In order to pin down the black hole's mass conclusively, Gebhardt says, one must account for all the components in the galaxy. Studies of the central and outermost regions of a galaxy are necessary to "see" the influence of the dark halo, the black hole and the stars. But when all of these components are considered together, Gebhardt says, the results on the black hole are definitive, meeting what he calls the "gold standard" for accurately sizing up a black hole.

Gebhardt used the Near-Infrared Field Spectrograph on Gemini to measure the speed of the stars as they orbit the black hole. The study was improved by Gemini's use of "adaptive optics," a system that compensates, in real time, for shifts in the atmosphere that can blur details seen by telescopes on the ground.

Together with the telescope's large collecting area, the adaptive optics system allowed Gebhardt and graduate student Joshua Adams to track the stars at M87's heart with 10 times greater resolution than previous studies.

"The result was only possible by combining the advantages of telescope size and spatial resolution at levels usually restricted to ground and space facilities, respectively," Adams says.

Astronomer Tod Lauer of the National Optical Astronomy Observatory, which was also involved in the Gemini observations, says "our ability to obtain such a robust black hole mass for M87 bodes well for our ongoing efforts to hunt for even larger black holes in galaxies more distant than M87."

Graduate student Jeremy Murphy used a different instrument to track the motions of stars at the outskirts of the galaxy. Studying the stars' movements in these distant regions gives astronomers insight into what the unseen dark matter in the halo is doing. Murphy employed an innovative instrument called VIRUS-P on McDonald Observatory's Harlan J. Smith Telescope.

Studying the distant edges of a galaxy, far from the bright center, is a tricky business, Gebhardt says.

"That has been an enormous struggle for a long time, trying to get what the dark halo is doing at the edge of the galaxy, simply because, when you look there, the stellar light is faint," he says. "This is where the VIRUS-P data comes in, because it can observe such a huge chunk of sky at once."

This means the instrument can add together the faint light from many dim stars and add them together to create one detailed observation. This kind of instrument is called an "integral field unit spectrograph," and VIRUS-P is the world's largest.

"The ability of VIRUS-P to dig deep into the outer halo of M87 and tell us how the stars are moving is impressive," Murphy says. "It has quickly become the leading instrument for this type of work."

The combined Gemini and McDonald data have allowed the team to pinpoint the mass of M87's black hole at 6.6 billion suns. But measuring such a massive black hole is only one step toward a greater goal.

"My ultimate goal is to understand how the stars assembled themselves in a galaxy over time," Gebhardt says.

"How do you make a galaxy? These two datasets probe such an enormous range, in terms of what the mass is in the galaxy. That's the first step to answering this question. It's very hard to understand how the mass accumulates unless you know exactly what's the distribution of mass: how much is in the black hole, how much is in the stars, how much is in the dark halo."

Today's conclusions also hint at another tantalizing possibility for the future: the chance to actually "see" a black hole.

"There's no direct evidence yet that black holes exist," Gebhardt says, "zero, absolutely zero observational evidence. To infer a black hole currently, we choose the 'none of above' option. This is basically because alternative explanations are increasingly being ruled out."

He says the black hole in M87 is so massive that astronomers someday may be able to detect its "event horizon" — the edge of a black hole, beyond which nothing can escape. The event horizon of M87's black hole is about three times larger than the orbit of Pluto — large enough to swallow our solar system whole.

Though the technology does not yet exist, M87's event horizon covers a patch of sky large enough to be imaged by future telescopes. Gebhardt says future astronomers could use a world-wide network of submillimeter telescopes to look for the shadow of the event horizon on a disc of gas that surrounds M87's black hole.

Red dwarfs can unleash powerful eruptions that may release the energy of more than 100 million atomic bombs

This is an artist's concept of a red dwarf star undergoing a powerful eruption, called a stellar flare. A hypothetical planet is in the foreground.Flares are sudden eruptions of heated plasma that occur when the field lines of powerful magnetic fields in a star's atmosphere "reconnect," snapping like a rubber band and releasing vast amounts of energy equivalent to the power of 100 million atomic bombs exploding simultaneously.Studying the light from 215,000 older red dwarfs collected in observations by NASA's Hubble Space Telescope, astronomers found 100 stellar flares popping off over the course of a week.

By STScl, Baltimore, Maryland
Published: January 11, 2011

A deep survey of more than 200,000 stars in our Milky Way Galaxy has unveiled the sometimes petulant behavior of tiny red dwarf stars. These stars, which are smaller than the Sun, can unleash powerful eruptions called flares that may release the energy of more than 100 million atomic bombs.

Red dwarfs are the most abundant stars in our universe and are presumably hosts to numerous planets. However, their erratic behavior could make life unpleasant, if not impossible, for many alien worlds. Flares are sudden eruptions of heated plasma that occur when powerful magnetic field lines in a star’s atmosphere “reconnect,” snapping like a rubber band and releasing vast amounts of energy. When they occur, flares would blast any planets orbiting the star with ultraviolet light, bursts of X-rays, and a gush of charged particles called a stellar wind.

Studying the light from 215,000 red dwarfs collected in observations by NASA’s Hubble Space Telescope, astronomers found 100 stellar flares. The observations, taken over a 7-day period, constitute the largest continuous monitoring of red dwarf stars ever undertaken.

“We know that hyperactive young stars produce flares, but this study shows that even in fairly old stars that are several billion years old, flares are a fact of life,” says astronomer Rachel Osten of the Space Telescope Science Institute in Baltimore, Maryland, leader of the research team. “Life could be rough for any planets orbiting close enough to these flaring stars. Their heated atmospheres could puff up and might get stripped away.”

Osten and her team, including Adam Kowalski of the University of Washington in Seattle, found that the red dwarf stars flared about 15 times less frequently than in previous surveys, which observed younger and less massive stars.

The stars in this study were originally part of a search for planets. Hubble monitored the stars continuously for a week in 2006, looking for the signature of planets passing in front of them. The stars were photographed by Hubble’s Advanced Camera for Surveys during the extrasolar-planet survey called the Sagittarius Window Eclipsing Extrasolar Planet Search (SWEEPS).

Osten and Kowalski realized that this powerful census contained important information on the stars themselves, and they took advantage of it. They searched the Hubble data, looking for a slight increase in the brightness of red dwarfs, a signature of flares. Some of the stars grew up to 10 percent brighter over a short period of time, which is actually much brighter than flares on our Sun. The average duration of the flares was 15 minutes. A few stars produced multiple flares.

The astronomers found that stars that periodically oscillate in brightness, called variable stars, were more prone to the short-term outbursts.

“We discovered that variable stars are about a thousand times more likely to flare than non-variable stars,” Kowalski says. “The variable stars are rotating fast, which may mean they are in rapidly orbiting binary systems. If the stars possess large starspots, dark regions on a star’s surface, that will cause the star’s light to vary when the spots rotate in and out of view. Starspots are produced when magnetic field lines poke through the surface. So, if there are big spots, there is a large area covered by strong magnetic fields, and we found that those stars had more flares.”

"Although red dwarfs are smaller than the Sun, they have a deeper convection zone, where cells of hot gas bubble to the surface, like boiling oatmeal,” Osten explains. This zone generates the magnetic field and enables red dwarfs to put out such energetic flares.

“The red dwarfs also have magnetic fields that are stronger than the Sun’s,” Osten continues. “They cover a much larger area than the Sun. Sunspots cover less than 1 percent of the Sun’s surface, while red dwarfs can have spots that cover half of their surfaces.”

Study confirms supermassive black holes formed before the buildup of galaxies

The dwarf galaxy Henize 2-10, seen in visible light by the Hubble Space Telescope. The central light-pink region shows an area of radio emission seen with the Very Large Array. This area indicates the presence of a supermassive black hole drawing in material from its surroundings. This also is indicated by strong X-ray emission from this region detected by the Chandra X-Ray Observatory. Reines, et al., David Nidever, NRAO/AUI/NSF/NASA

By NRAO, Socorro, New Mexico
Published: January 10, 2011

The surprising discovery of a supermassive black hole in a small nearby galaxy has given astronomers a tantalizing look at how black holes and galaxies may have grown in the early history of the universe. Finding a black hole a million times more massive than the Sun in a star-forming dwarf galaxy is a strong indication that supermassive black holes formed before the buildup of galaxies, the astronomers said.

The galaxy, called Henize 2-10 and located 30 million light-years from Earth, has been studied for years and is forming stars rapidly. Irregularly shaped and about 3,000 light-years across — compared to 100,000 for our own Milky Way — it resembles what scientists think were some of the first galaxies to form in the early universe.

"This galaxy gives us important clues about a very early phase of galaxy evolution that has not been observed before," said Amy Reines from the University of Virginia.

Supermassive black holes lie at the cores of all "full-sized" galaxies. In the nearby universe, there is a direct relationship – a constant ratio — between the masses of the black holes and that of the central "bulges" of the galaxies, leading them to conclude that the black holes and bulges affected each other’s growth.

Two years ago, an international team of astronomers found that black holes in young galaxies in the early universe were more massive than this ratio would indicate. This, they said, was strong evidence that black holes developed before their surrounding galaxies.

"Now, we have found a dwarf galaxy with no bulge at all, yet it has a supermassive black hole. This greatly strengthens the case for the black holes developing first, before the galaxy's bulge is formed," Reines said.

Reines, along with Gregory Sivakoff and Kelsey Johnson from the University of Virginia and the National Radio Astronomy Observatory (NRAO), and Crystal Brogan of the NRAO, observed Henize 2-10 with the National Science Foundation's Very Large Array radio telescope and with the Hubble Space Telescope. They found a region near the center of the galaxy that strongly emits radio waves with characteristics of those emitted by superfast jets of material spewed outward from areas close to a black hole.

They then searched images from the Chandra X-Ray Observatory that showed this same radio-bright region to be strongly emitting an energetic black-hole-powered galactic nucleus.

"Not many dwarf galaxies are known to have massive black holes," Sivakoff said.

While central black holes of roughly the same mass as the one in Henize 2-10 have been found in other galaxies, those galaxies all have much more regular shapes. Henize 2-10 differs not only in its irregular shape and small size, but also in its furious star formation, concentrated in numerous, very dense "super star clusters."

"This galaxy probably resembles those in the very young universe, when galaxies were just starting to form and were colliding frequently. All its properties, including the supermassive black hole, are giving us important new clues about how these black holes and galaxies formed at that time," Johnson said.

'Universe Sandbox' the gravity simulator

Fig: simulation of Saturn and Saturn’s Moons inside Universe Sandbox.

Universe Sandbox was designed and is developed by Dan Dixon, who worked on this educational project for over fifteen years before launching version 1.0 in May 2008.Universe Sandbox version 2.0 was released on May 2, 2010. It is an interactive space gravity simulator. Using Universe Sandbox, one can see the effects of gravity on objects in the universe and run scale simulations of our Solar System, various galaxies or other simulations, while at the same time, interacting and maintaining control over gravity, time, and other objects in the universe (moons, planets, asteroids, comets, black holes, etc.) Currently this software is only available for Windows based PCs.

Features:

This is a list of the key features of Universe Sandbox:

* Interactive n-body gravity simulator
* Simple tutorial introduction
* Several step-by-step activities included
* All units are measured in real units: kilograms, meters, seconds, etc.
* User control of the speed of time, gravity and other factors
* Simulation files are editable
* 3D Mode for use with red & cyan 3D glasses (anaglyph stereoscopic)
* Support for 3D DLP HD televisions
* Multiple color modes to help visualize and differentiate speeds and accelerations
* Two collision modes, Bounce and Combine
* Scaled ring systems of Saturn, Jupiter, Uranus, and Neptune, and generate rings around bodies
* Particle grids can be used to create 2D computer graphics or 3D computer graphics particle grids and then you warp/distort the grids and watch the gravitational effects by adding in moving planets or other objects (not in version 2)
* "Line-up/chart" mode option shows a visual size comparison of the stars and planets
* Includes the full sky panoramic view of the Milky Way from Axel Mellinger's photography of the Milky Way
* Can capture high resolution screen shots

Simulations:

Many simulations are included with Universe Sandbox, both realistic and fictional simulations.

* Our Solar System which includes the 8 planets, 5 minor planets, 160+ moons, and hundreds of asteroids
* The Andromeda & Milky Way galaxy collision which will occur in 4.5 billion years
* The 100 largest bodies in our Solar System
* The nearest 1000 stars to our Sun
* The nearest 70 Galaxies to the Milky Way
* A visual size comparison of the largest known stars and planets
* The Apophis asteroid passing near Earth in the year 2029
* The comet, Shoemaker Levy 9’s collision with Jupiter
* The 2008 KV42, a recently discovered comet with a retrograde motion orbit
* Moons converging into a single planet
* The Rho Cancri Solar System (55 Cancri) – which is a star with 5 known planets
* The Pioneer & Voyager encounters with Jupiter, Saturn, Uranus, & Neptune
* Visual Lagrange points of the Earth & Moon
* Gamma Ray Burst locations

Limitations:

This is a list of a few limitations of Universe Sandbox:

* Only runs on Windows based PCs
* The bounce collision mode is unrealistic
* When large bodies collide there is so much energy and heat that the bodies would meld together
* Ring positions relative to planets and moons are approximated
* Planet axis orientation relative to the solar plane is approximated and often inaccurate
* Galaxy simulations don't consider dark matter or account for the galaxy rotation problem

Kepler's newest discovery: A Rocky Exoplanet

Artist depiction of Kepler-10b
Photo by NASA

By NASA Headquarters, Washington, D.C. — Published: January 10, 2011

NASA’s Kepler mission has confirmed the discovery of its first rocky planet, named Kepler-10b. Measuring 1.4 times the size of Earth, it is the smallest planet ever discovered outside our solar system.

The discovery of this so-called exoplanet is based on more than 8 months of data collected by the spacecraft from May 2009 to early January 2010.

“All of Kepler’s best capabilities have converged to yield the first solid evidence of a rocky planet orbiting a star other than our Sun,” said Natalie Batalha, Kepler’s deputy science team lead at NASA’s Ames Research Center in Moffett Field, California, and primary author of a paper on the discovery accepted by The Astrophysical Journal. “The Kepler team made a commitment in 2010 about finding the telltale signatures of small planets in the data, and it’s beginning to pay off.”
Kepler’s ultra-precise photometer measures the tiny decrease in a star’s brightness that occurs when a planet crosses in front of it. The size of the planet can be derived from these periodic dips in brightness. The distance between the planet and the star is calculated by measuring the time between successive dips as the planet orbits the star.

Kepler is the first NASA mission capable of finding Earth-sized planets in or near the habitable zone, the region in a planetary system where liquid water can exist on the planet’s surface. However, since it orbits once every 0.84 days, Kepler-10b is more than 20 times closer to its star than Mercury is to our Sun and not in the habitable zone.

Kepler-10 was the first star identified that could potentially harbor a small transiting planet, placing it at the top of the list for ground-based observations with the W.M. Keck Observatory 10-meter telescope in Hawaii. Scientists waiting for a signal to confirm Kepler-10b as a planet were not disappointed. Keck was able to measure tiny changes in the star’s spectrum, called Doppler shifts, caused by the telltale tug exerted by the orbiting planet on the star.

“The discovery of Kepler 10-b is a significant milestone in the search for planets similar to our own,” said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington, D.C. “Although this planet is not in the habitable zone, the exciting find showcases the kinds of discoveries made possible by the mission and the promise of many more to come."

Knowledge of the planet is only as good as the knowledge of the star it orbits. Because Kepler-10 is one of the brighter stars being targeted by Kepler, scientists were able to detect high-frequency variations in the star’s brightness generated by stellar oscillations, or starquakes. This analysis allowed scientists to pin down Kepler-10b’s properties.

There is a clear signal in the data arising from light waves that travel within the interior of the star. Kepler Asteroseismic Science Consortium scientists use the information to better understand the star, just as earthquakes are used to learn about Earth’s interior structure. As a result of this analysis, Kepler-10 is one of the most well-characterized planet-hosting stars in the universe.The exoplanet’s star, Kepler-10, was the first one identified as capable of harboring a small transiting planet, placing the star at the top of the list for ground-based observations using the W.M. Keck Observatory 10-meter telescope in Hawaii. Kepler-10 is located 560 light-years from our solar system and is approximately the same size as our sun. The star is estimated to be 11.9 billion years old.

That’s good news for the team studying Kepler-10b. Accurate stellar properties yield accurate planet properties. In the case of Kepler-10b, the picture that emerges is of a rocky planet with a mass 4.6 times that of Earth and with an average density of 8.8 grams per cubic centimeter — similar to that of an iron dumbbell.

Research predicts distribution of gravitational-wave sources

The merger of two neutron stars, shown in this snapshot from a computer simulation, creates gravitational waves that could be detected by sensitive instruments. Credit: Stephan Rosswog and Enrico Ramirez-Ruiz.

By University of California - Santa Cruz — Published: December 6, 2010

A pair of neutron stars spiraling toward each other until they merge in a violent explosion should produce detectable gravitational waves. A new study led by an undergraduate at the University of California, Santa Cruz, predicts for the first time where such mergers are likely to occur in the local galactic neighborhood.

According to Enrico Ramirez-Ruiz, associate professor of astronomy and astrophysics at UC Santa Cruz, the results provide valuable information for researchers at gravitational-wave detectors, such as the Laser Interferometry Gravitational-Wave Observatory (LIGO) in Louisiana and Washington. "This is a very important result, as it is likely to significantly alter how gravitational-wave observatories currently operate," Ramirez-Ruiz said.Luke Zoltan Kelley, a UCSC undergraduate working with Ramirez-Ruiz, is first author of a paper describing the new findings, to be published in the December 10 issue of Astrophysical Journal Letters and currently available online.

A key prediction of Einstein's general theory of relativity, gravitational waves are ripples in the fabric of space-time caused by the motions of massive objects. Scientists have yet to detect gravitational waves directly because they are so weak and decay rapidly, but a planned upgrade for LIGO (called Advanced LIGO) is expected to greatly increase its sensitivity. Compact binaries--which can consist of two neutron stars, two black holes, or one of each--are among the best candidates for emitting gravitational waves that could be detected by LIGO or other current experiments.

Kelley investigated the implications of a key observation about compact binaries: The two objects are not only moving in orbit around each other, they are also typically speeding through space together, their center of mass moving with a velocity that can be well above 200 kilometers per second.

"By the time the two objects merge, they are likely to be located far away from the galaxy where they were born," Kelley said.

This has implications for efforts to observe mergers that emit gravitational waves. Scientists hope to match a detection at a gravitational-wave observatory with telescope observations of the corresponding merger event. The new study suggests that astronomers might not want to look in the nearest galaxies for these "optical counterparts" of gravitational waves.

"Our predictions show that the proposed use of galaxy catalogs for follow-up from possible gravity-wave detections will need to account for the possibility of mergers away from the observed galaxies," Ramirez-Ruiz said.The "kick" that sends compact binaries sailing out of their home galaxies comes from a slight asymmetry in the supernova explosions that give birth to neutron stars and black holes. When a massive star explodes, its core collapses to form either a neutron star (a rapidly rotating ball of densely packed neutrons) or a black hole. According to Kelley, a one-percent asymmetry in the supernova explosion would result in a recoil velocity of about 1,000 kilometers per second (about 2 million miles per hour).

"That is around the maximum velocity observed for lone neutron stars and pulsars," he said. "In binary systems, the net kick velocity to the center of mass is noticeably less, and still fairly uncertain, but is around 200 kilometers per second."

The researchers used a standard cosmological simulation of dark matter and the formation of structure in the universe to study how different kick velocities would affect the distribution of merging compact binaries. The simulation, run on a supercomputer at UCSC, showed the formation of halos of dark matter whose gravitational pull is thought to drive the formation of galaxies. The researchers populated the more massive halos with tracer particles representing compact binary systems. On separate runs, they gave the binaries different velocities.

After running the model for a simulated 13.8 billion years (the current age of the universe), Kelley found a region that looked like our local universe, with a galaxy the size of the Milky Way surrounded by a comparable set of neighboring galaxies. He then generated an image of the sky as it would appear to astronomers in the simulated universe, showing the locations of compact binaries and local galaxies.The results showed that variations in kick velocity lead to marked differences in the distribution of compact binaries. If the merger of a compact binary occurs away from the bright background of a galaxy, it could be detected by a survey telescope such as the planned Large Synoptic Survey Telescope (LSST). The operators of gravitational-wave observatories would then know when and where to look in their data for a gravitational-wave signal, Ramirez-Ruiz said.

He and colleagues at UCSC, including theoretical astrophysicist Stan Woosley and graduate student Luke Roberts, are currently trying to work out what the optical signal of a compact-binary merger should look like. "Detecting the optical counterparts of gravitational-wave detections will be a lot easier if they are not within galaxies," Ramirez-Ruiz said.

Kelley is currently finishing up his senior thesis at UCSC, helping Ramirez-Ruiz teach an astrophysics class, and deciding where he will go to graduate school.

In addition to Kelley and Ramirez-Ruiz, the coauthors of the paper include Marcel Zemp of the University of Michigan, Ann Arbor; Jürg Diemand of the Institute for Theoretical Physics at the University of Zurich; and Ilya Mandel of the Kavli Institute at the Massachusetts Institute of Technology. This research was supported by NASA, the David and Lucile Packard Foundation, the U.S. National Science Foundation, and the Swiss National Science Foundation.

NASA-Funded Research Discovers Life Built With Toxic Chemical

Image of GFAJ-1 grown on arsenic.
Image Credit: Jodi Switzer Blum

By NASA Headquarters, Washington, D.C. — Published: December 2, 2010

NASA-funded astrobiology research has changed the fundamental knowledge about what comprises all known life on Earth.

Researchers conducting tests in the harsh environment of Mono Lake in California have discovered the first known microorganism on Earth able to thrive and reproduce using the toxic chemical arsenic. The microorganism substitutes arsenic for phosphorus in its cell components.

"The definition of life has just expanded," said Ed Weiler, NASA's associate administrator for the Science Mission Directorate at the agency's headquarters in Washington, D.C. "As we pursue our efforts to seek signs of life in the solar system, we have to think more broadly, more diversely and consider life as we do not know it."

This finding of an alternative biochemistry makeup will alter biology textbooks and expand the scope of the search for life beyond Earth.

Carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur are the six basic building blocks of all known forms of life on Earth. Phosphorus is part of the chemical backbone of DNA and RNA, the structures that carry genetic instructions for life, and is considered an essential element for all living cells.

Phosphorus is a central component of the energy-carrying molecule in all cells (adenosine triphosphate) and also the phospholipids that form all cell membranes. Arsenic, which is chemically similar to phosphorus, is poisonous for most life on Earth. Arsenic disrupts metabolic pathways because chemically it behaves similarly to phosphate.

"We know that some microbes can breathe arsenic, but what we've found is a microbe doing something new — building parts of itself out of arsenic," said Felisa Wolfe-Simon, a NASA Astrobiology Research Fellow in residence at the U.S. Geological Survey in Menlo Park, California, and the research team's lead scientist. "If something here on Earth can do something so unexpected, what else can life do that we haven't seen yet?"

The newly discovered microbe, strain GFAJ-1, is a member of a common group of bacteria, the Gammaproteobacteria. In the laboratory, the researchers successfully grew microbes from the lake on a diet that was very lean on phosphorus, but included generous helpings of arsenic. When researchers removed the phosphorus and replaced it with arsenic, the microbes continued to grow. Subsequent analyses indicated that the arsenic was being used to produce the building blocks of new GFAJ-1 cells.

The key issue the researchers investigated was when the microbe was grown on arsenic, did the arsenic actually became incorporated into the organisms' vital biochemical machinery, such as DNA, proteins, and the cell membranes. The group used a variety of sophisticated laboratory techniques to determine where the arsenic was incorporated.

The team chose to explore Mono Lake because of its unusual chemistry, especially its high salinity, high alkalinity, and high levels of arsenic. This chemistry is in part a result of Mono Lake's isolation from its sources of fresh water for 50 years.

The results of this study will inform ongoing research in many areas, including the study of Earth's evolution, organic chemistry, biogeochemical cycles, disease mitigation and Earth system research. These findings also will open up new frontiers in microbiology and other areas of research.

"The idea of alternative biochemistries for life is common in science fiction," said Carl Pilcher, director of the NASA Astrobiology Institute at the agency's Ames Research Center in Moffett Field, California. "Until now, a life-form using arsenic as a building block was only theoretical, but now we know such life exists in Mono Lake."

SOHO spacecraft's 2000th comet

SOHO's 2000th comet, spotted by a Polish amateur astronomer on December 26, 2010.

Credit: SOHO/Karl Battams

By Goddard Space Flight Center, Greenbelt, Maryland Published: December 29, 2010

As people on Earth celebrate the holidays and prepare to ring in the New Year, an ESA/NASA spacecraft has quietly reached its own milestone: on December 26, the Solar and Heliospheric Observatory (SOHO) discovered its 2000th comet.

Drawing on help from citizen scientists around the world, SOHO has become the single greatest comet finder of all time. This is all the more impressive since SOHO was not specifically designed to find comets, but to monitor the sun.

"Since it launched on December 2, 1995 to observe the sun, SOHO has more than doubled the number of comets for which orbits have been determined over the last three hundred years," says Joe Gurman, the U.S. project scientist for SOHO at NASA's Goddard Space Flight Center in Greenbelt, Md.

Of course, it is not SOHO itself that discovers the comets -- that is the province of the dozens of amateur astronomer volunteers who daily pore over the fuzzy lights dancing across the pictures produced by SOHO's LASCO (or Large Angle and Spectrometric Coronagraph) cameras. Over 70 people representing 18 different countries have helped spot comets over the last 15 years by searching through the publicly available SOHO images online.The 1999th and 2000th comet were both discovered on December 26 by Michal Kusiak, an astronomy student at Jagiellonian University in Krakow, Poland. Kusiak found his first SOHO comet in November 2007 and has since found more than 100.

"There are a lot of people who do it," says Karl Battams who has been in charge of running the SOHO comet-sighting website since 2003 for the Naval Research Lab in Washington, where he also does computer processing for LASCO. "They do it for free, they're extremely thorough, and if it wasn't for these people, most of this stuff would never see the light of day."

Battams receives reports from people who think that one of the spots in SOHO's LASCO images looks to be the correct size and brightness and headed for the sun – characteristics typical of the comets SOHO finds. He confirms the finding, gives each comet an unofficial number, and then sends the information off to the Minor Planet Center in Cambridge, Mass, which categorizes small astronomical bodies and their orbits.

It took SOHO ten years to spot its first thousand comets, but only five more to find the next thousand. That's due partly to increased participation from comet hunters and work done to optimize the images for comet-sighting, but also due to an unexplained systematic increase in the number of comets around the sun. Indeed, December alone has seen an unprecedented 37 new comets spotted so far, a number high enough to qualify as a "comet storm."

LASCO was not designed primarily to spot comets. The LASCO camera blocks out the brightest part of the sun in order to better watch emissions in the sun's much fainter outer atmosphere, or corona. LASCO’s comet finding skills are a natural side effect -- with the sun blocked, it's also much easier to see dimmer objects such as comets.

"But there is definitely a lot of science that comes with these comets," says Battams. "First, now we know there are far more comets in the inner solar system than we were previously aware of, and that can tell us a lot about where such things come from and how they're formed originally and break up. We can tell that a lot of these comets all have a common origin." Indeed, says Battams, a full 85% of the comets discovered with LASCO are thought to come from a single group known as the Kreutz family, believed to be the remnants of a single large comet that broke up several hundred years ago.

The Kreutz family comets are “sungrazers” – bodies whose orbits approach so near the Sun that most are vaporized within hours of discovery – but many of the other LASCO comets boomerang around the sun and return periodically. One frequent visitor is comet 96P Machholz. Orbiting the sun approximately every six years, this comet has now been seen by SOHO three times.

SOHO is a cooperative project between the European Space Agency (ESA) and NASA. The spacecraft was built in Europe for ESA and equipped with instruments by teams of scientists in Europe and the USA.

NASA Research Team Unveils Moon Has Earth-Like Core

An artist's rendering of the lunar core as identified in new findings by a NASA-led research team. NASA/MSFC/Renee Weber

By NASA Headquarters, Washington, D.C., Marshall Space Flight Center, Huntsville, Alabama

Published: January 7, 2011

State-of-the-art seismological techniques applied to Apollo-era data suggest our moon has a core similar to Earth's.

Uncovering details about the lunar core is critical for developing accurate models of the moon's formation. The data sheds light on the evolution of a lunar dynamo -- a natural process by which our moon may have generated and maintained its own strong magnetic field.

The team's findings suggest the moon possesses a solid, iron-rich inner core with a radius of nearly 150 miles and a fluid, primarily liquid-iron outer core with a radius of roughly 205 miles. Where it differs from Earth is a partially molten boundary layer around the core estimated to have a radius of nearly 300 miles. The research indicates the core contains a small percentage of light elements such as sulfur, echoing new seismology research on Earth that suggests the presence of light elements -- such as sulfur and oxygen -- in a layer around our own core.

The researchers used extensive data gathered during the Apollo-era moon missions. The Apollo Passive Seismic Experiment consisted of four seismometers deployed between 1969 and 1972, which recorded continuous lunar seismic activity until late-1977.

"We applied tried and true methodologies from terrestrial seismology to this legacy data set to present the first-ever direct detection of the moon's core," said Renee Weber, lead researcher and space scientist at NASA's Marshall Space Flight Center in Huntsville, Ala.

In addition to Weber, the team consisted of scientists from Marshall; Arizona State University; the University of California at Santa Cruz; and the Institut de Physique du Globe de Paris in France. Their findings are published in the online edition of the journal Science.

The team also analyzed Apollo lunar seismograms using array processing, techniques that identify and distinguish signal sources of moonquakes and other seismic activity. The researchers identified how and where seismic waves passed through or were reflected by elements of the moon's interior, signifying the composition and state of layer interfaces at varying depths.

Although sophisticated satellite imaging missions to the moon made significant contributions to the study of its history and topography, the deep interior of Earth's sole natural satellite remained a subject of speculation and conjecture since the Apollo era. Researchers previously had inferred the existence of a core, based on indirect estimates of the moon's interior properties, but many disagreed about its radius, state and composition.

A primary limitation to past lunar seismic studies was the wash of "noise" caused by overlapping signals bouncing repeatedly off structures in the moon's fractionated crust. To mitigate this challenge, Weber and the team employed an approach called seismogram stacking, or the digital partitioning of signals. Stacking improved the signal-to-noise ratio and enabled the researchers to more clearly track the path and behavior of each unique signal as it passed through the lunar interior.

"We hope to continue working with the Apollo seismic data to further refine our estimates of core properties and characterize lunar signals as clearly as possible to aid in the interpretation of data returned from future missions," Weber said.

Future NASA missions will help gather more detailed data. The Gravity Recovery and Interior Laboratory, or GRAIL, is a NASA Discovery-class mission set to launch this year. The mission consists of twin spacecraft that will enter tandem orbits around the moon for several months to measure the gravity field in unprecedented detail. The mission also will answer longstanding questions about Earth's moon and provide scientists a better understanding of the satellite from crust to core, revealing subsurface structures and, indirectly, its thermal history.

NASA and other space agencies have been studying concepts to establish an International Lunar Network -- a robotic set of geophysical monitoring stations on the moon -- as part of efforts to coordinate international missions during the coming decade.