Posted on by Nancy Atkinson

Blinding Gamma Ray Burst Was Directed at Earth

Artists depiction of GRB 080319B Credit: NASA/Swift/Mary Pat Hrybyk-Keith and John Jones

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On March 19, 2008 at 2:13 am EDT, NASA’s Swift satellite detected an explosion from the constellation Bootes, and sent an alert to ground-based telescopes. At the same moment, the Russian KONUS instrument on NASA’s Wind satellite and a robotic wide-field optical camera called “Pi of the Sky” in Chile captured the first visible light from this incredibly bright and powerful gamma ray burst. Within the next 15 seconds, the burst brightened enough to be visible in a dark sky to human eyes. For a few moments, the GRB had a million times the luminosity of the entire Milky Way Galaxy. It briefly crested at a magnitude of 5.3 on the astronomical brightness scale. Incredibly, the dying star was 7.5 billion light-years away. Astronomers say the reason this gamma ray burst was so bright was that it was aimed almost directly at Earth.

Observations of the event, formally named GRB 080319B, are giving astronomers the most detailed portrait of a GRB ever recorded. “You have to have the satellites in orbit and the rapid response telescopes on Earth in order take complete advantage this rare kind of event,” said David Burrows, head of the Swift X-ray telescope team, at today’s press conference detailing the GRB.

Judith Racusin of Penn State University and a team of 92 coauthors report on observations across the spectrum that began 30 minutes before the explosion and followed its afterglow for months. The team concludes the burst’s extraordinary brightness arose from an unusual two component jet that shot material directly toward Earth at 99.99995 percent the speed of light.

Telescopes around the world already were studying the afterglow of another burst when GRB 080319B exploded just 10 degrees away.

Immediately after the blast, Swift’s UltraViolet and Optical Telescope and X-Ray Telescope indicated they were effectively blinded. Racusin initially thought something was wrong. Within minutes, however, as reports from other observers arrived, it was clear this was a special event. A head-on burst directed towards Earth only occurs by chance only about once a decade, so GRB 080319B is a rare catch.

Gamma-ray bursts are the universe’s most luminous explosions. Most occur when massive stars run out of nuclear fuel. As a star’s core collapses, it creates a black hole or neutron star that, through processes not fully understood, drive powerful gas jets outward. These jets punch through the collapsing star. As the jets shoot into space, they strike gas previously shed by the star and heat it. That generates bright afterglows.


The team believes the jet directed toward Earth contained an ultra-fast component just 0.4 of a degree across. This core resided within a slightly less energetic jet about 20 times wider. “A normal signature is different from what we saw in this burst,” said Racusin . “In this object, we see two signatures of jets with two different properties.”

“Perhaps every gamma-ray burst has a narrow jet, but astronomers miss it most of the time,” says team member Stefano Covino. “We happened to view this monster down the barrel of the very narrow and energetic jet.”

These unique beacons of light were observed only 8 minutes after the trigger, and are the brightest bursts ever detected. Additional study of this event can also help provide more information on relativity and cosmology.

Burrows said if a similar event happened at our own galaxy, we would be in considerable trouble. “It’s been postulated that a nearby gamma ray burst directed at earth could affect our atmosphere, causing something like a nuclear winter. We are fortunate in that we don’t believe there are any stars in our galas that will produce a gamma ray burst.”

NASA, NASA News Audio

Posted on by Nancy Atkinson

Oops, TW Hydrae b Isn’t a Planet; Just a Sunspot

Artists depiction of what the TW Hydrae system might have looked like. Credit: Max Planck Institute

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You gotta love this about science; someone is always checking your work. Early this year a new exoplanet discovery was announced: TW Hydrae b, a huge planet about ten times as massive as Jupiter. Astronomers thought the planet was in a super-tight orbit around its host star (TW Hydrae), circling in only 3.56 days at a distance of about 6 million kilometers, which is about 4 percent of the distance from the Sun to the Earth. However, another group of astronomers decided to analyze some new optical and infrared data to confirm the radial velocity signal of the planet. Something didn’t seem right, so they ran a few more tests and computer models and determined what they were seeing wasn’t a planet. It was a big sunspot. “Our model shows that a cold spot covering 7% of the stellar surface and located at a latitude of 54 deg can reproduce the reported RV variations,” the astronomers reported in their paper. The rest of the astronomical world must agree with the new determination, as TW Hydrae b has now been dropped from the Planet Quest New Worlds Atlas (a fun site to peruse.) But nature doesn’t like a void, — and astronomers have been working hard in the planet-search department, — so, three new extra solar planets have been discovered and added to the atlas, for a current planet count of 309.

GJ 832 b is about half the size mass of Jupiter and orbits 3.4 AU from its tiny host star. The star is a yellow, sun-like G star, about 16 light years from Earth. It was found with the Anglo-Australian Telescope. Astronomers say it has the largest angular distance from its star among radial velocity detected exoplanets, which makes it a potentially interesting target for future direct detection.

HD 205739 b was also just announced:. This exoplanet is 1.37 times the size mass of Jupiter, and orbits about .9 AU from its star, a blue to white star, which is 1.22x the size of the sun, and 294 light years from Earth. It has an eccentric orbit, and astronomers believe there may be an additional planet in this system, because of how the planet orbits.

Another planet found by the same astronomical team is HD 154672 b. This is a biggie, at about five times the size mass of Jupiter, but only about .6 AU distant from its star, which is just about sun-size, and about 213 light years from Earth. The planet has an orbital period of 163.9 days.

These last two planets were found using the N2K Doppler planet search program with the Magellan telescopes.

Sources: arXiv (here, here and here) and Twitter, PlanetQuest

Posted on by Nancy Atkinson

China To Launch Manned Mission This Month

China's Long March rocket. Credit: Xinhua

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China will launch its third manned space mission in late September, sending three astronauts into Earth orbit. The mission will feature China’s first-ever space walk, according to the Xinhua News Agency, the official news agency of China. The Shenzhou 7 launch will take place sometime between Sept. 25 and 30, from the Jiuquan Satellite Launch Center in northwestern Gansu province. The space walk will be broadcast live using cameras mounted on the inside and outside of the spacecraft.

The Long March rocket was loaded with fuel on Sunday. “All the major systems involved in the launching are now in the final preparation. The main tests for the spacecraft, the Long-March II-F rocket, suits for the space walk and a satellite accompanying the fly have also been finished,” said the spokesman.

On April 12, China launched a new space tracking satellite to assist with the Shenzhou-7 spacewalk mission. The new space tracking ship is the sister ship of the Yuanwang-5, which was put into use a year ago. Xinhua said the two vessels will play a key role in the Shenzhou-7 mission.

In 2003, China became the third country in the world — along with the United States and Russia — to send a human into orbit. It followed with a two-man mission in 2005.

China also launched the Chang’e 1 moon orbiter in October of 2007.

Source: Xinhua

Posted on by Nancy Atkinson

Clumps Growing on Phoenix Lander Legs

Clumps of material have adhered to the legs of the Phoenix Mars Lander, and the clumps continue to change and grow. The science team has discussed various possible explanations for these clumps. One suggestion is that they may have started from a splash of mud if Phoenix’s descent engines melted icy soil during the landing. Another is that specks of salt may have landed on the strut and began attracting atmospheric moisture that freezes and accumulates. The clumps are concentrated on the north side of the strut, usually in the shade, so their accumulation could be a consequence of the fact that condensation favors colder surfaces. Below, compare images taken on September 1, 2008, or the 97th Martian Day or sol, since landing with another image taken about three months earlier, on Sol 8.

Sol 97 image under the lander. Credit: NASA/JPL/Caltech/U of AZ

Sol 8 image from under the lander. Credit: NASA/JPL/Caltech/U of AZ

Phoenix’s Robotic Arm Camera took both images. The top image from Sol 97 was taken at about 4 a.m. local solar time. The view in this Sol 97 image is southward. Illumination is from the early morning sun above the northeastern horizon. This is quite different from the illumination in the Sol 8 image, bottom which was taken in mid-afternoon.

The two images also show a contrast in the flat, smooth patch of exposed ice underneath the lander. Phoenix team members believe the ice was exposed from the spacecraft’s thrusters as it landed. In the latest image, the patches of ice exposed underneath the lander seem to be partly covered by darker material left behind as ice vaporizes away. The flat patch in the center of the image has the informal name “Holy Cow,” based on researchers’ reaction when they saw the initial image of it.

Source: Phoenix Gallery

Posted on by Nancy Atkinson

‘Laser Comb’ To Measure the Accelerating Universe

Back in April, UT published an article about using a device called a ‘laser comb’ to search for Earth-like planets. But astronomers also hope to use the device to search for dark energy in an ambitious project that would measure the velocities of distant galaxies and quasars over a 20-year period. This would let astronomers test Einstein’s theory of general relativity and the nature of the mysterious dark energy. The device uses femto-second (one millionth of one billionth of a second) pulses of laser light coupled with an atomic clock to provide a precise standard for measuring wavelengths of light. Also known as an “astro-comb,” these devices should give astronomers the ability to use the Doppler shift method with incredible precision to measure spectral lines of starlight up to 60 times greater than any current high-tech method. Astronomers have been testing the device, and hope to use one in conjunction with the new Extremely Large Telescope which is being designed by ESO, the European Southern Observatory.

Astronomers use instruments called spectrographs to spread the light from celestial objects into its component colors, or frequencies, in the same way water droplets create a rainbow from sunlight. They can then measure the velocities of stars, galaxies and quasars, search for planets around other stars, or study the expansion of the Universe. A spectrograph must be accurately calibrated so that the frequencies of light can be correctly measured. This is similar to how we need accurate rulers to measure lengths correctly. In the present case, a laser provides a sort of ruler, for measuring colors rather than distances, with an extremely accurate and fine grid.

New, extremely precise spectrographs will be needed in experiments planned for the future Extremely Large Telescope.

“We’ll need something beyond what current technology can offer, and that’s where the laser frequency comb comes in. It is worth recalling that the kind of precision required, 1 cm/s, corresponds, on the focal plane of a typical high-resolution spectrograph, to a shift of a few tenths of a nanometre, that is, the size of some molecules,” explains PhD student and team member Constanza Araujo-Hauck from ESO.

The new calibration technique comes from the combination of astronomy and quantum optics, in a collaboration between researchers at ESO and the Max Planck Institute for Quantum Optics. It uses ultra-short pulses of laser light to create a ‘frequency comb’ – light at many frequencies separated by a constant interval – to create just the kind of precise ‘ruler’ needed to calibrate a spectrograph.

The device has been tested on a solar telescope, a new version of the system is now being built for the HARPS planet-finder instrument on ESO’s 3.6-metre telescope at La Silla in Chile, before being considered for future generations of instruments.

More information on laser combs.

Source: ESO

Posted on by Nancy Atkinson

GOCE Launch Delayed

Artist rendition of the GOCE Satellite in orbit. Credit: ESA

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The launch of ESA’s GOCE satellite (the ‘sexy’ spacecraft) will be delayed. During launch preparations yesterday (Sunday, Sept. 7) a problem was discovered with a guidance and navigation subsystems on the launch vehicle’s upper stage. To fix the problem, guidance and navigation unit will have to be replace. The upper stage, which includes the GOCE satellite, will have to be de-mated from the rest of the Breeze KM rocket and brought in from the launch site to be repaired. The launch, which will take place at the Plesetsk cosmodrome in northern Russia, is now scheduled for October 5 at 16:21 CEST.

The satellite and upper stage will be brought to an integration room. Once in the clean room, the protective fairing that shelters the satellite will be opened and the spacecraft and its adaptor system will be dismounted in order to allow access to the Breeze KM equipment to be replaced.

GOCE, which stands for Gravity field and steady-state Ocean Circulation Explorer will investigate and map Earth’s gravitational field. ESA officials say the satellite and its mission will not be affected by this launch delay.


Source: ESA

Posted on by Nancy Atkinson

Water on Mars Was Prolonged, Study Shows

Valley Networks on Mars. Image: NASA

Previous studies of Mars indicated that while water was certainly present on the Red Planet in the ancient past, it may have only been on the surface for a short time, present in short catastrophic floods. However, a new study suggests that ancient features on Mars called valley networks were carved by recurrent floods during a long period when the Martian climate may have been much like that of some arid or semiarid regions on Earth. “Our results argue for liquid water being stable at the surface of Mars for prolonged periods in the past,” said Charles Barnhart, a graduate student in Earth and planetary sciences at the University of California, Santa Cruz. “Precipitation on Mars lasted a long time–it wasn’t a brief interval of massive deluges.”

Scientists estimate that the valley networks on Mars were carved out more than 3.5 billion years ago. Studies based on climate models have suggested that catastrophic events such as asteroid impacts could have created warm, wet conditions on Mars, causing massive deluges and flooding for periods of hundreds to thousands of years.

But using a sophisticated computer model to simulate the processes that formed the valley networks shows that those short period conditions would result in features not seen in the Martian landscape, because water would accumulate inside craters and overflow, carving exit breaches that cut through the crater walls, Barnhart said.

“Our research finds that these catastrophic anomalies would be so humid and wet there would be breaching of the craters, which we don’t see on Mars,” he said. “The precipitation needs to be seasonal or periodic, so that there are periods of evaporation and infiltration. Otherwise the craters overflow.”

Valley Networks on Mars. Credit: NASA
Valley Networks on Mars. Credit: NASA

The researchers used a landform evolution model to simulate how the surface of Mars would evolve under different climate conditions. They ran more than 70 simulations under varied conditions and performed statistical analyses to determine which yielded the best match to the observed topography of martian valleys.

The results suggest that valley networks formed on Mars during a semiarid to arid climate that persisted for tens of thousands to hundreds of thousands of years. Episodic flooding alternated with long dry periods when water could evaporate or soak into the ground. Rainfall may have been seasonal, or wet intervals may have occurred over longer cycles. But conditions that allowed for the presence of liquid water on the surface of Mars must have lasted for at least 10,000 years, Barnhart said.

A paper describing their findings has been accepted for publication in the Journal of Geophysical Research–Planets.

Source: UC Santa Cruz

Posted on by Nancy Atkinson

New Technique Expands View of Young Exo-Planetary Systems

Using a new technique with a near-infrared spectrograph attached to ESO’s Very Large Telescope, astronomers have been able to study planet-forming discs around young Sun-like stars in unsurpassed detail, clearly revealing the motion and distribution of the gas in the inner parts of the disc. Astronomers used a technique known as ‘spectro-astrometric imaging’ to give them a window into the inner regions of the discs where Earth-like planets may be forming. They were able not only to measure distances as small as one-tenth the Earth-Sun distance, but also measure the velocity of the gas at the same time. “This is like going 4.6 billion years back in time to watch how the planets of our own Solar System formed,” says Klaus Pontoppidan from Caltech, who led the research.

Pontoppidan and colleagues have analyzed three young analogues of our Sun that are each surrounded by a disc of gas and dust from which planets could form. These three discs are just a few million years old and were known to have gaps or holes in them, indicating regions where the dust has been cleared and the possible presence of young planets. However, each of the discs are very different from each other and likely will result in very different planetary systems. “Nature certainly does not like to repeat herself,” said Pontoppidan.

For one of the stars, SR 21, a massive giant planet orbiting at less than 3.5 times the distance between the Earth and the Sun has created a gap in the disc, while for the second star, HD 135344B, a possible planet could be orbiting at 10 to 20 times the Earth-Sun distance. Observations of the disc surrounding the third star, TW Hydrae, may indicate the presence of one or two planets.

The new results not only confirm that gas is present in the gaps in the dust, but also enable astronomers to measure how the gas is distributed in the disc and how the disc is oriented. In regions where the dust appears to have been cleared out, molecular gas is still highly abundant. This can either mean that the dust has clumped together to form planetary embryos, or that a planet has already formed and is in the process of clearing the gas in the disc.

CRIRES, the near-infrared spectrograph attached to ESO’s Very Large Telescope, is fed from the telescope through an adaptive optics module which corrects for the blurring effect of the atmosphere and so makes it possible to have a very narrow slit with a high spectral dispersion: the slit width is 0.2 arcsecond and the spectral resolution is 100 000. Using spectro-astrometry, an ultimate spatial resolution of better than 1 milli-arcsecond is achieved.

“The particular configuration of the instrument and the use of adaptive optics allow astronomers to carry out observations with this technique in a very user-friendly way: as a consequence, spectro-astrometric imaging with CRIRES can now be routinely performed,” says team member Alain Smette, from ESO.

Source: ESO Press Release

Posted on by Nancy Atkinson

Opportunity Twitters Self Portrait

Opportunity self shadow portrait. Credit: NASA/JPL/Cornell

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The Mars Exploration Rovers are now tweeting on Twitter, and Opportunity recently shared what she’s been doing since climbing out of Victoria crater via a shadow self portrait. After seeing a one-time electrical spike on Opportunity’s left front wheel, mission managers decided to have the rover climb out of the crater and get back on level ground. Opportunity is now examining some fist sized rocks, or cobbles, that might be ejecta from far away craters. Spirit, over on the other side of the Red Planet is weathering out the end of the southern hemisphere Martian winter. Another Twitter report from the rovers said that Spirit’s solar array energy is now up slightly from 235 to 245 watt hours. Power levels will have to rise a little more before Spirit can resume exploring actively.

Spirit's southern tilt. Credit: NASA/JPL/Cornell
Spirit's southern tilt. Credit: NASA/JPL/Cornell

Spirit has had to park on a north facing tilt in order to gather as much sunlight, and the image above shows the tilt. In the latest rover flight director video report, rover driver Scott Maxwell said the team is keeping an eye on the weather near Spirit’s, location watching for any rise in atmospheric dust. Dust has gathered on the rover’s solar panels, and any additional dust would hamper power levels as well. But so far everything is looking good, and Martian skies were actually clearer this past week.

Both rovers have been operating for more than 1,600 Martian sols, or days on Mars. A sol on Mars in about 40 minutes longer than an Earth day.

Posted on by Nancy Atkinson

Rosetta Flies By ‘Diamond in the Sky’ Steins

Mosaic of images from Rosetta's fly by. Credit: ESA

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ESA’s Rosetta spacecraft successfully flew by the asteroid 2867 Steins, coming within 800 km (500 miles) and gathering images and data on the irregularly shaped rock in space. “Steins looks like a diamond in the sky,” said Uwe Keller, Principal Investigator for the OSIRIS imaging system on board the spacecraft. Watch a movie of the flyby here. Visible in the images are several small craters on the asteroid, and two huge ones. While the wide-angle camera worked perfectly during the flyby, the narrower and higher resolution camera switched itself off and into safe mode a few minutes before closest approach, but switched back on after a few hours. “The software switched off automatically,” said Gerhard Schwehm, Rosetta mission manager. “The camera has some software limits and we’ll analyze why this happened later.”

Rita Schulz, Rosetta Project Scientist, said, “In the images is a chain of impact craters, which must have formed from recurring impact as the asteroid rotated. The impact may have been caused by a meteoroid stream, or fragments from a shattered small body.”

The chain is composed of about 7 craters. To determine the age of the asteroid, a count of the craters on the asteroid’s surface has been started (the more the number of craters, the older the asteroid). So far, 23 craters have been spotted.

Steins in 3 D. Credit: ESA
Steins in 3 D. Credit: ESA

From the images, scientists will try and understand why the asteroid is unusually bright, and how fine grains of the surface regolith are. This will tell them more about how the asteroid formed. Images from the narrow angle camera are yet to be retrieved, and will help add to the knowledge of the surface composition and mineralogy.

“It looks like a typical asteroid, but it is really fascinating how much we can learn from just the images,” said Schwehm. “This is our first science highlight; we certainly have a lot of promising science ahead of us. I’m already looking forward to encountering our next diamond in the sky, the much bigger Lutetia.” Rosetta will meet up with asteroid (21) Lutetia on June 10, 2010.

What’s next for Rosetta? It will reach the maximum distance from the Sun on its current orbit on the 17th of December (2.26 AU) to head back to Earth for the next and last swing-by on the Nov. 13, 2009. After it flies by Lutetia, its final destination is going into orbit around Comet 67P/Churyumov-Gerasimenko in 2014.

Source: ESA