Astronomy and Astrophysics

SETI Institute Researcher Strikes Scientific Gold with Meteorite

MOFFETT FIELD, Calif. - Scientists found treasure when they studied an exceptional meteorite recovered April 22, 2012 at Sutter's Mill, the gold discovery site that led to the 1849 California Gold Rush.

An international team of 70 researchers reported in today's issue of “Science” that this meteorite provided the most pristine look yet at the surface of the type of primitive asteroid that NASA hopes to send astronauts to in the future.

"The small three meter-sized asteroid that impacted over California’s Sierra Nevada came in at twice the speed of typical meteorite falls," said lead author and meteor astronomer Peter Jenniskens of the SETI Institute and NASA Ames Research Center, Moffett Field, Calif. "Clocked at 64,000 miles per hour, it hit with the energy of a quarter of a Hiroshima bomb. It was the biggest impact over land since the impact of the four meter-sized asteroid 2008 TC3, four years ago over Sudan."

After the asteroid broke up in the atmosphere, weather radar briefly detected a hailstorm of falling meteorites over the townships of Coloma and Lotus in California. This enabled a rapid recovery that permitted the most pristine look yet of a type of meteorite classified as a Carbonaceous-Mighei or CM-type carbonaceous chondrite.

"This was the first time a rare carbonaceous chondrite meteorite was recovered based on such weather radar detection," said Marc Fries of the Planetary Science Institute in Tucson, Arizona, who pioneered the use of this technique. "Meteorites were found mostly under the radar footprint."

Of the estimated 100,000 pound asteroid, less than two pounds was recovered on the ground in the form of 77 meteorites. The biggest was 205 grams.

Some of the key meteorites discussed in this work were found by volunteer search teams led by Jenniskens. "The entire Ames community really came together in the search for these meteorites. People work at NASA because they love science and that was very evident when we saw the overwhelming response of volunteers from Ames wanting to be a part of this,” said Pete Worden, director of NASA Ames Research Center.

From photographs and video of the fireball, Jenniskens calculated that the asteroid approached on an unusual low-inclined almost comet-like orbit that reached the orbit of Mercury, passing closer to the sun than known from other recorded meteorite falls.

"Based on the unusually short time that the asteroid was exposed to cosmic rays, Sutter's Mill orbited the sun in just about as much time as when it was part of the asteroid belt," Jenniskens said. "It circled the sun three times during a single orbit of Jupiter, in resonance with that planet."

"There was not much time for the asteroid to go slower or faster around the sun," added Jenniskens. That puts the original source asteroid very close to this resonance, in a low inclined orbit.  A good candidate source region for CM chondrites is the Eulalia asteroid family, recently proposed as a source of primitive C-class asteroids in orbits that pass Earth."

NASA hopes to send astronauts to such C-class asteroids in the future and is already sending robotic spacecraft to a near-Earth primitive asteroid.

"NASA's robotic OSIRIS-REx mission is currently being prepared to bring back a pristine sample of an asteroid named 1999 RQ36," said co-author and mission co-investigator Scott Sandford of NASA Ames.  "In addition, Sutter's Mill has the same reflective properties as near-Earth asteroid, 1999 JU3, the mission target of the Hayabusa 2 sample return mission currently being prepared by the Japanese space agency (JAXA)."

The Sutter's Mill meteorite provides a rare glimpse of what these space missions may find.

"The meteorite was a jumbled mess of rocks, called a regolith breccia, that originated from near the surface of a primitive asteroid," said meteoriticist Derek Sears of NASA Ames.

The rapid recovery resulted in the detection of compounds that quickly disappear once a meteorite lands on Earth. Mike Zolensky, a mineralogist at NASA’s Johnson Space Flight Center, Houston, was surprised to detect the mineral oldhamite, a calcium sulfide, known in the past to disappear from contact with water by simply breathing on it.

"This mineral was known before mainly from rare enstatite chondrites," said Zolensky, "and its presence in the regolith breccia could mean that primitive and highly evolved asteroids collided with each other even at early times when the debris accumulated that now makes the meteorite matrix."

A wide array of carbon-containing compounds was detected that quickly reacted with water once in the Earth's environment. It is thought that the carbon atoms in our body may have been brought to Earth by such primitive asteroids in the early stages of our planet’s history.

"Amino acids were few in this meteorite because this particular meteorite appears to have been slightly heated in space before it arrived at Earth," said Danny Glavin of NASA’s Goddard Space Flight Center, Greenbelt, Md.

It appears that different parts of the meteorite had a different thermal alteration history. Heating also removed some of the water that used to move salts around in the asteroid.

"Samples collected before it rained on the meteorite fall area still contained such salts," said George Cooper of NASA Ames, "but Sutter's Mill was less altered by water in the asteroid itself than other CM type meteorites." 

"Only 150 parts per billion of Sutter's Mill was actual gold," said co-author and cosmochemist Qing-zhu Yin of U.C. Davis, Davis, Calif., "but all of it was scientific gold. With 78 other elements measured, Sutter's Mill provides one of the most complete records of elemental compositions documented for such primitive meteorites."

Recent Starbursts in the Milky Way Galaxy's Center

WASHINGTON -- Researchers using the Stratospheric Observatory for Infrared Astronomy (SOFIA) have captured new images of a seven light-year-diameter ring of gas and dust surrounding the supermassive black hole at the center of the galaxy, and of a neighboring cluster of extremely luminous young stars embedded in dust cocoons.

These images are the subjects of two posters presented this week during the American Astronomical Society’s meeting in Long Beach, Calif. Ryan Lau of Cornell University (Ithaca, NY) and his collaborators studied the Milky Way’s circumnuclear ring, or CNR (Figure 1a). Matt Hankins of the University of Central Arkansas (Conway, Ark.) is lead author of the other paper, regarding the Quintuplet Cluster, or QC (Figure 2a).

SOFIA is a highly modified Boeing 747SP aircraft carrying a telescope with an effective diameter of 100 inches (2.5 meters) to altitudes as high as 45,000 feet (14 km). The images were obtained during SOFIA flights in 2011 with the FORCAST (Faint Object infraRed Camera for the SOFIA Telescope) instrument built by a team with Principal Investigator Terry Herter of Cornell. Each image is a combination of multiple exposures at wavelengths of 20, 32, and 37 microns that are partially or completely blocked by water vapor in Earth’s atmosphere and thus inaccessible to ground-based observatories even on high mountain peaks. 

Our Galaxy’s nucleus lies behind interstellar dust clouds in the mid-plane of the Milky Way which are mostly or completely opaque to visible and near-infrared light but more transparent at longer infrared wavelengths. Figures 1b and 2b show comparison images of the CNR and QC regions made with a near-infrared camera on the Hubble Space Telescope. The CNR and other exotic features revealed by the FORCAST camera on SOFIA are invisible in the Hubble images. Figure 3 shows the two fields studied in these papers as square insets on a large-scale image of the galactic center made by the Spitzer Space Telescope at a wavelength of 8 microns.

The nucleus of the Milky Way is inhabited by a black hole with 4 million times the mass of the Sun that is orbited by a large disk of gas and dust. The ring seen in Figure 1a is the inner edge of that disk. The galactic center also hosts several exceptionally large star clusters containing some of the most luminous young stars in the Galaxy, one of which is the Quintuplet Cluster seen in Figure 2. The combination of SOFIA’s airborne telescope with the FORCAST camera produced the sharpest images of those regions ever obtained at mid-infrared wavelengths, allowing discernment of new clues about what is happening near the central black hole.

“The focus of our study has been to determine the structure of the circumnuclear ring with the unprecedented precision possible with SOFIA” said Mr. Lau. “Using these data we can learn about the processes that accelerate and heat the ring.” Mr. Hankins, lead author of the QC paper, noted that, “Something big happened in the Milky Way’s center within the past 4 to 6 million years which resulted in several bursts of star formation, creating the Quintuplet Cluster, the Central Cluster, and one other massive star cluster.” Hankins added, “Many other galaxies also have so-called ‘starbursts’ in their central regions, some associated with central black holes, some not. The Milky Way’s center is much nearer than other galaxies, making it easier for us to explore possible connections between the starbursts and the black hole.”

SOFIA Chief Scientific Advisor Eric Becklin, who is working with the CNR group, determined the location of the galaxy’s nucleus as a graduate student in the 1960s by laboriously scanning a single-pixel infrared detector to map the central region. Becklin said, “The resolution and spatial coverage of these images is astounding, showing what modern infrared detector arrays can do when flown on SOFIA. We hope to use these data to substantially advance our understanding of the environment near a supermassive black hole.”

SOFIA is a joint project of NASA and the German Aerospace Center (DLR) that is based and managed at NASA’s Dryden Aircraft Operations Facility in Palmdale, Calif. NASA’s Ames Research Center at Moffett Field, Calif., manages the SOFIA science and mission operations in cooperation with the Universities Space Research Association (USRA) headquartered in Columbia, Md., and the German SOFIA Institute (DSI) at the University of Stuttgart.

The SETI Institute and the Astronomical Society of the Pacific are partners in leading the SOFIA Education and Public Outreach programs. 

For more information about SOFIA, visit:

http://www.nasa.gov/sofia
http://www.dlr.de/en/sofia

For information about SOFIA's science mission, visit:

http://www.sofia.usra.edu
http://www.dsi.uni-stuttgart.de/index.en.html

 

Hubble Space Telescope Reveals Rogue Planetary Orbit for Fomalhaut b

Mountain View, CA -- Newly released NASA Hubble Space Telescope images of a vast debris disk encircling the nearby star Fomalhaut and a mysterious planet circling it may provide forensic evidence of a titanic planetary disruption in the system. 

Astronomers are surprised to find the debris belt is wider than previously known, spanning a section of space from 14 to nearly 20 billion miles from the star. Even more surprisingly, the latest Hubble images have allowed a team of astronomers to calculate the planet follows an unusual elliptical orbit that carries it on a potentially destructive path through the vast dust ring. 

The planet, called Fomalhaut b, swings as close to its star as 4.6 billion miles, and the outermost point of its orbit is 27 billion miles away from the star. The orbit was recalculated from the newest Hubble observation made last year. 

Paul Kalas
Paul Kalas is a research scientist at the SETI Institute

"We are shocked. This is not what we expected," said Paul Kalas of the University of California at Berkeley and the SETI Institute in Mountain View, Calif. 

The Fomalhaut team led by Kalas considers this circumstantial evidence there may be other planet-like bodies in the system that gravitationally disturbed Fomalhaut b to place it in such a highly eccentric orbit. The team presented its finding Tuesday at the 221st meeting of the American Astronomical Society in Long Beach, Calif.

Among several scenarios to explain Fomalhaut b's 2,000-year-long orbit is the hypothesis that an as yet undiscovered planet gravitationally ejected Fomalhaut b from a position closer to the star, and sent it flying in an orbit that extends beyond the dust belt. 

"Hot Jupiters get tossed through scattering events, where one planet goes in and one gets thrown out," said co-investigator Mark Clampin of NASA's Goddard Space Flight Center in Greenbelt, Md. "This could be the planet that gets thrown out."

Hubble also found the dust and ice belt encircling the star Fomalhaut has an apparent gap slicing across the belt. This might have been carved by another undetected planet. Hubble's exquisite view of the dust belt shows irregularities that strongly motivate a search for other planets in the system.

If its orbit lies in the same plane with the dust belt, then Fomalhaut b will intersect the belt around 2032 on the outbound leg of its orbit. During the crossing, icy and rocky debris in the belt could crash into the planet's atmosphere and create the type of cosmic fireworks seen when Comet Shoemaker-Levy 9 crashed into Jupiter. Most of the fireworks from collisions will be seen in infrared light. However, if Fomalhaut b is not co-planar with the belt, the only thing to be seen will be a gradual dimming of Fomalhaut b as it travels farther from the star.

Kalas hypothesized that Fomalhaut b's extreme orbit is a major clue in explaining why the planet is unusually bright in visible light, but very dim in infrared light. It is possible the planet's optical brightness originates from a ring or shroud of dust around the planet, which reflects starlight. The dust would be rapidly produced by satellites orbiting the planet, which would suffer extreme erosion by impacts and gravitational stirring when Fomalhaut b enters into the planetary system after a millennium of deep freeze beyond the main belt. An analogy can be found by looking at Saturn, which has a tenuous, but very large dust ring produced when meteoroids hit the outer moon Phoebe.

The team has also considered a different scenario where a hypothetical second dwarf planet suffered a catastrophic collision with Fomalhaut b. The collision scenario would explain why the star Fomalhaut has a narrow outer belt linked to an extreme planet. But in this case the belt is young, less than 10,000 years old, and it is difficult to produce energetic collisions far from the star in such young systems.

Fomalhaut is a special system because it looks like scientists may have a snapshot of what our solar system was doing 4 billion years ago. The planetary architecture is being redrawn, the comet belts are evolving, and planets may be gaining and losing their moons. Astronomers will continue monitoring Fomalhaut b for decades to come because they may have a chance to observe a planet entering an icy debris belt that is like the Kuiper Belt at the fringe of our own solar system.

For more information and for related images, please visit: 

www.nasa.gov/hubble

and 

http://hubblesite.org/news/2013/01

Herschel Finds Old Star Possibly Making Planets

WASHINGTON -- A star thought to have passed the age when it can form planets may in fact be creating new worlds. The disk of material surrounding the surprising star called TW Hydrae may be massive enough to make even more planets than we have in our own solar system.

Herschel is a European Space Agency (ESA) telescope, with science instruments provided by a consortium of European institutes, and with important participation from NASA. 

At roughly 10 million years old and 176 light-years away, TW Hydrae is relatively close to Earth by astronomical standards. Its planet-forming disk has been well studied. In theory, TW Hydrae is of the age at which giant planets already may have formed. 

Planets are born out of material swirling around young stars and the mass of this material is one factor that controls their formation. Before the new Herschel study, astronomers did not know whether the disk contained enough material to form planets similar to our own.

Astronomers were able to calculate the weight, or mass, of the star's planet-forming disk with the highest precision by using Herschel. The space telescope sees longer-wavelength, or "far," infrared light, allowing it to search for the spectral signature of a gas molecule called hydrogen deuteride. This molecule has one atom made of hydrogen, and one made of a heavier version of hydrogen, called deuterium. It is correlated with regular hydrogen molecules, which are the main gas component of planets. 

"Knowing the mass of a planet-forming disk is crucial to understanding how and when planets take shape around other stars," said Glenn Wahlgren, Herschel program scientist at NASA Headquarters in Washington.

Astronomers did not expect to see so much gas around TW Hydrae, according to Edwin Bergin of the University of Michigan in Ann Arbor. Bergin led the new study appearing in the journal Nature. "Typically stars of this age have cleared out their surrounding material, but this star still has enough mass to make the equivalent of 50 Jupiters," Bergin said.

The new method can directly probe the gas that typically goes into making planets, whereas previous techniques were indirect and uncertain.

"Before, we had to use a proxy to guess at what the gas quantity was in the planet-forming disks," said Paul Goldsmith, the project scientist for Herschel at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "This is another example of Herschel's versatility and sensitivity yielding important new results about star and planet formation."

Astronomers do not know whether TW Hydrae's large disk will lead to an exotic planetary system with larger and more numerous planets than ours, but the new information helps define the range of possible planet scenarios in the universe.

"The new results are another important step in understanding the diversity of planetary systems in our universe," said Bergin. "We are now observing systems with massive Jupiters, super-Earths, and many Neptune-like worlds. By weighing systems at their birth, we gain insight into how our own solar system formed with just one of many possible planetary configurations." 

NASA's Herschel Project Office is based at NASA's Jet Propulsion Laboratory. JPL contributed mission-enabling technology for two of Herschel's three science instruments. The NASA Herschel Science Center, part of the Infrared Processing and Analysis Center at Caltech, supports the United States astronomical community. Caltech manages JPL for NASA. 

For NASA'S Herschel website, visit: http://www.nasa.gov/herschel

For ESA'S Herschel website, visit: http://www.esa.int/SPECIALS/Herschel/index.html

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