A Hubble Heritage Release

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April 21, 2009: Over the past 19 years Hubble has taken dozens of exotic pictures of galaxies going "bump in the night" as they collide with each other and have a variety of close encounters of the galactic kind. Just when you thought these interactions couldn't look any stranger, this image of a trio of galaxies, called Arp 194, looks like one of the galaxies has sprung a leak. The bright blue streamer is really a stretched spiral arm full of newborn blue stars. This typically happens when two galaxies interact and gravitationally tug at each other.

Resembling a pair of owl eyes, the two nuclei of the colliding galaxies can be seen in the process of merging at the upper left. The blue bridge looks like it connects to a third galaxy. In reality the galaxy is in the background and not connected at all. Hubble's sharp view allows astronomers to try and visually sort out what are foreground and background objects when galaxies, superficially, appear to overlap. This picture was issued to celebrate the 19th anniversary of the launch of the Hubble Space Telescope aboard the space shuttle Discovery in 1990. During the past 19 years Hubble has made more than 880,000 observations and snapped over 570,000 images of 29,000 celestial objects.

New Gamma-Ray Burst Smashes Cosmic Distance Record

April 28, 2009: NASA's Swift satellite and an international team of astronomers have found a gamma-ray burst from a star that died when the universe was only 630 million years old--less than five percent of its present age. The event, dubbed GRB 090423, is the most distant cosmic explosion ever seen.

"The incredible distance to this burst exceeded our greatest expectations -- it was a true blast from the past," says Swift lead scientist Neil Gehrels at NASA's Goddard Space Flight Center.

Above: GRB 090423 as seen by NASA's Swift satellite. The image is a composite of data from Swift's UV/Optical and X-Ray telescopes. Credit: NASA/Swift/Stefan Immler [Larger image]

The burst occurred at 3:55 a.m. EDT on April 23rd. Swift quickly pinpointed the explosion, allowing telescopes on Earth to target the burst before its afterglow faded away. Astronomers working in Chile and the Canary Islands independently measured the explosion's redshift. It was 8.2, smashing the previous record of 6.7 set by an explosion in September 2008. A redshift of 8.2 corresponds to a distance of 13.035 billion light years.

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"We're seeing the demise of a star -- and probably the birth of a black hole -- in one of the universe's earliest stellar generations," says Derek Fox at Pennsylvania State University.

Gamma-ray bursts are the most luminous explosions in the Universe. Most occur when massive stars run out of nuclear fuel. As their cores collapse into a black hole or neutron star, jets of matter punch through the star and blast into space. There, they strike gas previously shed by the star and heat it, which generates short-lived afterglows in many wavelengths.

For years, astronomers have been hunting for gamma-ray bursts from the earliest generations of stars--and mysteriously failing to find them. The detection of GRB 090423 is an important milestone in the quest to locate bursts in the redshift range 10 to 20. More information: "The Case of the Missing Gamma-ray Bursts."

Within three hours of the April 23rd burst, Nial Tanvir at the University of Leicester, U.K., and his colleagues reported detection of an infrared source at the Swift position using the United Kingdom Infrared Telescope on Mauna Kea, Hawaii.

At the same time, Fox led an effort to obtain infrared images of the afterglow using the Gemini North Telescope on Mauna Kea. The source appeared in longer-wavelength images but was absent in an image taken at the shortest wavelength of 1 micron. This "drop out" corresponded to a distance of about 13 billion light-years.

Right: An artist's concept of a gamma-ray burst in action. Click on the image for animations. Credit: NASA/Swift/Cruz deWilde.

As Fox spread the word about the record distance, telescopes around the world turned to observe the afterglow before it faded away.

At the Galileo National Telescope on La Palma in the Canary Islands, a team including Guido Chincarini at the University of Milan-Bicocca, Italy, determined that the afterglow's redshift was 8.2. Tanvir's team, gathering nearly simultaneous observations using one of the European Southern Observatory's Very Large Telescopes on Cerro Paranal, Chile, arrived at the same number.

"It's an incredible find," Chincarini says. "What makes it even better is that a telescope named for Galileo made this measurement during the year in which we celebrate the 400th anniversary of Galileo's first astronomical use of the telescope."

Twilight Sky Show

April 24, 2009: If you're reading this at the end of the day on Sunday, April 26th—stop! You're supposed to be outside looking at the sunset.

On Sunday evening, the crescent Moon, Mercury and the Pleiades star cluster will gather for a three-way conjunction in the western sky. It's a must-see event.

The show begins before the sky fades to black. The Moon pops out of the twilight first, an exquisitely slender 5% crescent surrounded by cobalt blue. The horns of the crescent cradle a softly-glowing image of the full Moon. That is Earthshine—dark lunar terrain illuminated by sunlight reflected from Earth. If the show ended then and there, you'd be satisfied.

Right: A crescent Moon with Earthshine over Manassas, Virginia, on Dec. 30, 2008. Photo credit: Karen Schmeets. [Larger image]

But there's more.

Shortly after the Moon appears, Mercury materializes just below it. The innermost planet has emerged from the glare of the sun for its best apparition of the year in late April—perfect timing for a sunset encounter with the Moon. To the naked eye, Mercury looks like a pink 1st-magnitude star. The planet itself is not pink; it only looks that way because it has to shine through dusty lower layers of Earth’s atmosphere. A backyard telescope pointed at Mercury reveals a tiny fat crescent. The innermost planet has phases like the Moon!

Next, do nothing. Spend some quiet moments absorbing the view. As the twilight deepens, your eyes will dark-adapt and—voilà! There are the Pleiades.

Also known as the Seven Sisters, the Pleiades are a cluster of young stars about a hundred light years from Earth. They form a miniature Little Dipper located, on this particular evening, halfway between Mercury and the Moon. The brightest stars of the cluster are only 2nd magnitude, not terrifically bright. Nevertheless, the Pleiades are compelling in disproportion to their luminosity. Every ancient culture--Greek, Maya, Aztec, Aborigine, Māori and others—put the cluster in its myths and legends. On April 26th you may discover why, even if you cannot articulate your findings.

The Pleiades, Moon and Mercury are all visible to the naked eye even from light-polluted cities. Nevertheless, if you have binoculars, use them. A quick scan of the threesome reveals a rugged moonscape in startling detail, the rich pink hue of Mercury, and many more than seven sisters (there are hundreds of stars in the cluster).

Still reading? Stop! Twilight awaits.

NASA Puts the Right Stuff in the Right Hands

Oh, a storm is threatening
My very life today
If I don't get some shelter
Oh yeah, I'm gonna fade away … ("Gimme Shelter," The Rolling Stones)

April 22, 2009: Imagine a monster tornado is ripping through a neighboring county and bearing down on yours.

If you live in north Alabama, your forecasters are well prepared to tell you when to seek shelter.

The National Weather Service there shares a building – the National Space Science and Technology Center – with NASA's Short-term Prediction Research and Transition, or SPoRT, Center. SPoRT puts state-of-the-art NASA satellite data directly into forecasters hands, arming them to recognize weather that threatens your safety.

Right: The National Weather Service's Chris Darden (Science Operations Officer) and Mike Coyne (Meteorologist In Charge) handle communications during severe weather. [Larger image]

"It's not just a matter of them throwing random data sets over the fence to us and hoping we might be able to use them," says Chris Darden from the National Weather Service (NWS). "They work with us to figure out precisely what we need. Then they put that data into a format we can read, actually integrating it with our radar displays. And they train us to understand and interpret the information they give us."

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Dr. Gary Jedlovec, SPoRT principal investigator, notes, "We're all in this together in this building, and the public is the ultimate winner. Adding our data to NWS weather models helps forecasters give the community accurate advanced warnings."

That tornado plowing through an adjoining county is a prime example. SPoRT gives forecasters several tools to help predict a thunderstorm’s potential for spawning such a beast. One of the best such tools is the North Alabama Lightning Mapping Array -- an 11-sensor network that measures lightning around the area.

Think of how your radio crackles noisily when lightning flashes. That's because lightning produces a lot of radio frequency noise. By zeroing in on an unused frequency, the 11 sensors scattered around on water towers, radio towers, and roof tops, measure a storm's total amount of lightning.

Above: Click on the image to launch a 16 megabyte animation of data from the Lightning Mapping Array. It shows the progress of lightning activity in Franklin County, Alabama, during a severe storm in March 2002. [movie]

"The total lightning data can help forecasters predict whether a storm might generate a tornado," says Rich Blakeslee, NASA atmospheric scientist. "We've found that often intercloud lightning – not cloud-to-ground lightning -- suddenly spikes and then, just as suddenly, diminishes a very few minutes before a tornado forms."

Darden adds, "We add the total real-time lightning data to our radar and wind velocity information to help us make that critical decision whether to send out a warning."

SPoRT and other NSSTC programs also have access to another tool -- a Dual-Polarimetric Doppler Radar -- that actually reveals the shapes of raindrops. Traditional weather radar sends pulses of radiation that oscillate in one direction only--horizontally. Dual polarization radar sends pulses that oscillate in two directions--horizontally and vertically. By combining the reflections from both kinds of pulses, scientists can tell what shape and size a raindrop is.

"Flatter and wider means bigger raindrops, because the larger the raindrop is the flatter it gets as it falls," explains Walt Petersen, NASA physical scientist. "That information helps weather forecasters better estimate rainfall amounts – and therefore flash flooding – and storm intensity."

This radar can also tell the difference between rain and hail because hail is typically spherical while raindrops tend to flatten. Adding this information to the strength of the return, forecasters can tell the size of the hail.

Right: A slice through a 2.5 inch hail stone collected at the home of NASA scientist Walt Petersen in Madison, Alabama. "The layering in the stone illustrates the different growth regimes that the hail stone went through (sometimes coated with water, sometimes dry) as it ascended and descended through the storm. We can detect these types of changes on the hailstone surface with the dual-polarization radar." [Larger image]

"Large hail indicates powerful updraft and downdraft winds within a thunderstorm," says Petersen. "So it usually means a strong storm, and sometimes means that a storm may produce a tornado."

"This radar tells us a lot about a potentially violent storm," says Darden. "It's pretty new, so we still have a lot to learn."

No problem. The scientists at the NSSTC train current forecasters and future meteorologists alike to use these cutting-edge tools. University of Alabama Huntsville's Atmospheric Science Department is, like the NWS, collocated with NASA researchers at NSSTC.

"During severe weather, day or night, my students gather here to operate the radar," says Petersen. "You should see 'em. It's like weather central here sometimes!

"When there's a fierce storm brewing, or even crashing around us, the students, UAH and NASA researchers, and forecasters communicate in real time by instant messaging with the NWS's IEM online chat tool (NWSChat). They chat about operating the radar and interpreting the radar data. It's a great hands-on way to learn."

Right: Ph.D. student Christopher Schultz operates the dual polarization radar from his workstation at UAH. [Larger image]

WHNT-TV, a local TV station, also uses the data from this radar, and is in fact the first broadcast meteorology station in the world to have access to such a tool.

"So the benefit goes straight to the consumer--the viewing audience," says Petersen.

And the benefits are not just local.

"We've transferred many of these tools to other forecast offices across the country," says Darden. "For example, our office is one of only a few U.S. NWS offices with access to this kind of radar, but all the offices must convert their radars to dual pole by the end of next year. We'll be helping to train them in its use, passing along what we've learned from SPoRT."

Both the lightning mapping and dual pole radar are ground-based now, but in the future will be space-based.

"We're developing products to work with the Geostationary Lightning Mapper on GOES-R – NOAA's next-generation weather satellite," says Jedlovec. "With the launch of that satellite in about 2015, lightning could be mapped all across the U.S. from the vantage point of space."

Again, thanks to NASA, the NWS forecasters here will be a step ahead in using a new tool, and ready to help other forecasters learn the ropes to help their communities.

"This is an exciting place to work," says Jedlovec. "All the tornado warnings for Madison County come right out of this building. We don't just write research papers. With the help of the National Weather Service, we see our data used for the good of the public. That makes us feel good about what we do."

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Mt. Redoubt Gives Alaskans a Taste of the Moon

April 3, 2009: "It's very fine but angular – the sharp edges make it feel gritty and abrasive."

"It can cause short circuits and failure of electronic components ... and physical damage to equipment."

"It's much more abrasive than sand....scratches anything that comes in contact...."

"...a real nuisance....stuck to everything – equipment, instruments,...likely to penetrate seals,....plugs bolt holes, fouls tools, ....."

These quotes seem to all refer to the same annoying substances, but they don't. In fact, the substances they refer to aren't even from the same planet.

The first two quotes are from Alaska, where people are dealing with volcanic ash from the ongoing eruption of Mount Redoubt. The next two come from the Moon, where Apollo astronauts once dealt with a similar problem: moondust.

Right: Mt. Redoubt has erupted at least 19 times since March 22, 2009. Alaska photographer Thomas Kerns took this picture of the volcano in action on March 31st. [Larger image]

"Volcanic ash and moondust have a lot in common," says Carole McLemore* of the Marshall Space Flight Center. "Both coat things and stick to them, are grimy, abrasive, damaging to equipment and vehicles, susceptible to electric charging, and risky to inhale.

"Mount Redoubt is giving Alaskans a taste of life on the Moon!"

The stories Alaskans and astronauts tell reveal some of the parallels:

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Charles Sloan, a retired hydrogeologist living in Anchorage, has experienced ash first hand. He was around for one of Mount Redoubt's previous eruptions in 1989 and remembers a particularly harrowing incident.

"An international carrier flight -- a large jet -- flew into the hot ash plume from the volcano. The ash was sucked into the engines, causing them to shut down, and the plane plummeted!" All 245 terrified passengers on board KLM flight 867 held their breaths. "The plane dropped more than 2 miles before the crew could get the engines restarted! It limped in to an emergency landing in Anchorage."

"That was the third such incident over a five year period," adds Tom Miller, former director and now scientist emeritus of the Alaska Volcano Observatory** in Anchorage.

Way back in 1972, astronauts Gene Cernan and Jack Schmitt experienced their own transportation problems when their moonbuggy lost a fender. That doesn't sound like a disaster on the scale of a plummeting airplane—but when moondust is involved, even a lost fender can have serious consequences.

Above: Dust flies from the tires of a moonbuggy driven by Apollo 17 astronaut Gene Cernan. When a fender fell off, plumes of high-flying dust caused serious problems, which the astronauts solved using duct tape: full story.

A rolling moonbuggy without a fender kicks up a "rooster tail" of moondust, spraying the rover and its occupants with dark, abrasive grit. White spacesuits blackened by dust turn into absorbers of the fierce lunar sun with astronauts overheating dangerously inside. Sharp-edged dust wiped off visors scratch the glass, making helmets difficult to see out of. Watch out for that crater! And moondust has an uncanny way of working itself into hinges, latches and joints, rendering them useless.

The resourceful astronauts repaired the fender with duct tape, but even with all four fenders, Cernan had to dust off the rover at each stop. Getting rid of moondust remained a top priority.

Back in Alaska, Miller relates what happened when Mt. Redoubt erupted just last week: "We lost three seismic stations. The one nearest the volcano was fried – probably due to lightning. When you have a tremendous and powerful explosion of ash, the violent movement of all the ash particles generates static electricity and therefore lightning."

Right: Lightning flashes in a roiling cloud of ash over Mt. Redoubt on March 27th. Particles of ash rubbing together in the cloud (like socks rubbing against carpet) are partly responsible for the buildup of electrostatic charge. Photo credit and copyright: Bretwood Higman, Ground Truth Trekking. [more]

Dust particles on the Moon are also electrified, at least in part, by the buffeting of the solar wind. Earth is protected from the solar wind by our planet's magnetic field, but the Moon has no global magnetic field to ward off charged particles from the sun. Free electrons in the solar wind interact with grains of moondust and, in effect, "charge them up." The electrostatic charges cause moondust to cling tenaciously to everything.

Including your lungs…

Apollo 17 astronaut Gene Cernan suffered from the first recorded case of extraterrestrial hay fever. He was taking off his spacesuit after a moonwalk and the air was filling up with dust knocked off the surface of the suit. "It came on pretty fast," he radioed Houston with a stuffy-nose twang. "I had a significant reaction to the dust," he later recalled. "My turbinates (cartilage plates in the walls of the nasal chambers) became swollen."

Some researchers believe sustained breathing of moondust could be dangerous. The sharp-edged grains are able to make tiny cuts in flesh, and they could easily become stuck in lung tissue. Ash presents a similar hazard.

"With volcanic ash, people are advised to wear particle masks or stay indoors," notes Miller. "It's not poisonous, but people with asthma or emphysema can have problems if they inhale it. And people who wear contacts have to take their contacts out."

Above: An Alaskan moonscape. "Highlights of gray volcanic ash around the snow remind me of craters on the Moon," says photographer Michelle Cosper of Girdwood, Alaska. [Larger image]

Alaska resident Michelle Cosper is one of the people suffering. "My throat is sore and stingy, and it smells vaguely like sulfur outside," she reports from the town of Girdwood, which has received a coating of ash from Redoubt's recent eruptions. "We aren't supposed to walk our dogs or go outside for any other reason unnecessarily. Even local newscasters are wearing face masks."

Moondust and volcanic ash cause many of the same troubles—but that does not mean they are the same thing. Volcanic ash comes from active volcanoes, something the Moon does not have. Liquid rock decompresses and explodes from the volcano's mouth, producing a mixture of 'foamed' glass and micro- and mini-crystals. Moondust, on the other hand, is created by meteoroids. Space rocks hit the Moon's surface at hundreds of thousands of miles per hour, fusing topsoil into glass and shattering the same into tiny sharp-edged pieces.

NASA is returning to the Moon in ~2020. Thanks to Mt. Redoubt, Alaskans are already getting a taste of the new frontier.

Hubble Finds Hidden Exoplanet in Archival Data

April 1, 2009: In 19 years of observations, the Hubble Space Telescope has amassed a huge archive of data. That archive may contain the telltale glow of undiscovered extrasolar planets, says David Lafrenière of the University of Toronto, Ontario, Canada. His team found the outermost of three massive planets known to orbit the young star HR 8799, which is 130 light-years away. The planetary trio was originally discovered in images taken with the Keck and Gemini North telescopes in 2007 and 2008. But using a new image processing technique that suppresses the glare of the parent star, Lafrenière found the telltale glow of the outermost planet in the system while studying Hubble archival data taken in 1998. The giant planet is young and hot, but still only 1/100,000th the brightness of its parent star (by comparison, cooler Jupiter is one-billionth the brightness of the sun).

Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) has looked at over 200 other stars in coronagraphic mode, where the light of the star is largely blocked out, to search for the feeble glow of planets. Lafrenière plans to look for undiscovered planets in the NICMOS archive dataset and do follow-up observations with ground-based telescopes on any candidates that pop up. As an added bonus, NICMOS made a near-infrared measurement that suggests water vapor is in the atmosphere of the planet. This could not be easily achieved with ground-based telescopes, because water vapor in Earth's atmosphere absorbs some infrared wavelengths. Measuring the water absorption properties on this exoplanet will tell astronomers a great deal about the temperatures and pressures in the atmosphere, and about the prevalence of dust clouds. But don't go looking for beachfront property; the planet is 1,500 degrees Fahrenheit -- too hot even for water vapor clouds.

THE GAMMA RAY STAR

February 10, 2009: NASA's Swift and Fermi spacecraft are monitoring a neutron star 30,000 light years from Earth that is drawing attention to itself with a series of powerful gamma-ray flares.

"At times, this remarkable object has erupted with more than a hundred flares in as little as 20 minutes," said Loredana Vetere, who is coordinating the Swift observations at Pennsylvania State University. "The most intense flares emitted more total energy than the sun does in 20 years."

Right: An artist's concept of the flare star in action. Credit: NASA/Goddard Space Flight Center Conceptual Image Lab. [more]

The star, known as SGR J1550-5418, lies in the southern constellation Norma. It began a series of modest eruptions on Oct. 3, 2008, settled down for a while, then roared back to life on Jan. 22, 2009, with an intense episode.

Because of its rapid-fire outbursts and gamma-ray spectrum, astronomers classify the object as a "soft-gamma-ray repeater" -- only the sixth known. In 2004, a giant flare from another soft-gamma-ray repeater was so intense it ionized Earth's upper atmosphere from 50,000 light-years away: more.

Using data from an X-ray telescope onboard Swift, Jules Halpern at Columbia University captured the first "light echoes" ever seen from a soft-gamma-ray repeater. Images acquired when the latest flaring episode began show what appear to be expanding halos around the source. Multiple rings form as X-rays interact with dust clouds at different distances. Click on the image to play a 6-day movie:

Above: Swift's X-Ray Telescope (XRT) captured an apparent expanding halo around the flaring neutron star SGR J1550-5418. The halo formed as X-rays from the brightest flares scattered off of intervening dust clouds. Credit: NASA/Swift/Jules Halpern, Columbia Univ. [more]

Scientists think the source of the flares is a spinning neutron star--the superdense, city-sized remains of a supernova. Although only about 12 miles across, a neutron star contains more mass than the sun. This particular neutron star is believed to be a "magnetar," a neutron star with an incredibly intense magnetic field.

A popular theory of soft-gamma-ray repeaters holds that flares are caused by "starquakes" in the outer rigid crust of the magnetar. As a magnetar's colossal magnetic field shifts, it strains the crust with monstrous magnetic forces, often breaking it. When the crust snaps, it vibrates with seismic waves like in an earthquake and emits a flash of gamma-rays.

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No one is really certain of the details, however, and much work remains to be done to understand these powerfully hyperactive stars.

NASA's Fermi Gamma-ray Space Telescope, launched in June 2008, is ideal for this work. "The ability of Fermi's gamma-ray burst monitor to resolve the fine structure within these events will help us better understand how magnetars unleash their energy," said Chryssa Kouveliotou, an astrophysicist at NASA's Marshall Space Flight Center in Huntsville, Ala. The object has triggered Fermi's gamma-ray burst monitor more than 95 times since Jan. 22nd.

NASA's Wind satellite, the joint NASA-Japan Suzaku mission, and the European Space Agency's INTEGRAL satellite also have detected flares from SGR J1550-5418.