Posted on by Mike Simonsen

20 Million Observations by Amateur Astronomers!

Graph showing the rapidly growing number of observations in the AAVSO International Database. Courtesy AAVSO.

[/caption]Early into the celebration of its centennial year, observers of the American Association of Variable Star Observers (AAVSO) passed another milestone over the weekend, when an amateur astronomer from Belgium contributed the 20 millionth observation of a variable star on February 19, 2011.

Amateur astronomers have been recording changes in the brightness of stars for centuries. The world’s largest database is run by the AAVSO. Started in 1911, it is one of the oldest, continuously operating citizen science projects in the world.

“The long-term study of stellar brightness variation is critical to understanding how stars work and the impact they have on their surroundings. The noble efforts of the engaged AAVSO volunteers play an important role in astronomy and help expand human knowledge,” said Dr. Kevin Marvel, Executive Officer of the American Astronomical Society.

The AAVSO currently receives variable star brightness estimates from about 1,000 amateur astronomers per year. Some variable stars are bright enough to be seen with the unaided eye while others require high-tech equipment. The AAVSO also has a network of robotic telescopes available to members free of charge.

“Because some variable stars are unpredictable and/or change their brightness over long time scales, it is not practical for professional astronomers to watch them every night. Thus, amateurs were recruited to keep tabs on these stars on behalf of professionals,” Dr. Arne Henden, Director of the AAVSO, said.

The 20 millionth observation was made by Dr. Franz-Josef “Josch” Hambsch of Belgium. The observation was of GV Andromeda, member of a class of older, pulsating stars smaller than our Sun. “I like these stars because you can see their entire variation cycle in one night. There have not been many recent observations made of this particular star, so that is why I am monitoring it,” Hambsch said. Hambsch is also a member of the Belgian variable star organization, Vereniging Voor Sterrenkunde, Werkgroep Veranderlijke Sterren (VVS, WVS).

Actual light curve of GV And created from Josch Hambsh's data. One of these points is the 20 millionth observation! Courtesy AAVSO.

The process of estimating a star’s brightness can range from less than a minute to many hours per estimate, but typically takes about five minutes. At that rate, observers have invested the equivalent of about 1.67 million hours of time in collecting observations for the database. Assuming a current median salary of US$33,000, this would be the roughly equivalent to 27.5 million dollars worth of donated time if all the observations were reported today.

“The reality is these observations are invaluable. The database spans many generations and includes data that cannot be reproduced elsewhere. If an astronomer wants to know the history of a particular star, they come to the AAVSO,” Henden said.

The AAVSO’s mission is to coordinate, collect, and distribute variable star data to support scientific research and education. The AAVSO International Database is openly available to the public through their web site (www.aavso.org), where it is queried hundreds of times per day.

Posted on by Ken Kremer

Movies of Comet Tempel 1 Encounter by Stardust-NExT

NASA's Stardust-NExT mission took this image of comet Tempel 1 at 8:39 p.m. PST (11:39 p.m. EST) on Feb 14, 2011. The comet was first visited by NASA's Deep Impact mission in 2005. Credit: NASA/JPL-Caltech/Cornell. Image brightened and enhanced by Ken Kremer to show additional detail.

Want to know what it feels like at close range to ride on a spaceship past a zooming comet that’s spewing dust and debris that could destroy you at any moment ?

Check out the movies (above & below) which gives you a front row seat at NASA’s newest ‘Comet Experience’. Hitch a ride on the rear of Stardust-NExT as it flew past Compet Tempel 1 at 9.8 km/sec, or 24,000 MPH.

The movie comprises the highest resolution images of the fleeting 8 minutes of the closest approach period that occurred between 8:35:26 p.m. to 8:43:08 p.m. PST on Feb. 14, 2011 (4:35:26 a.m. to 4:43:08 a.m. UTC, Feb. 15, 2011, according to the clock kept aboard the spacecraft).

Stardust started taking these the excellent quality photos at a distance of 2,462 kilometers (1,530 miles) away from the center of the comet and get to within 185 kilometers (115 miles). By the end of the movie, the spacecraft is 2,594 kilometers (1,611 miles) away from the center of the comet.

Think about it and the navigational precision required to pull off this feat. After a journey of near 6 billion kilometers (3.5 Billion miles) and 12 years, the highest quality science and images are captured in what amounts to an instant in time.

“And they did it with Math !”, exclaimed NASA Asspciate Admisistrator Ed Weiler at the post encounter briefing. Weiler exhorted school kids worldwide to study math and science if that want to accomplish great deeds.

Comet Tempel 1 was approximately 335 million kilometers (208 million miles) away from Earth and on the other side of the sun during the encounter. Tempel 1 is oblong in shape and has an average diameter of about 6 kilometers (4 miles).

The individual images are all online. Check out these alternate movie versions prepared by Dimitri Demeeter at Youtube and nasatech.net at the links below.

Here’s 1/10 sec with text

Here’s 1/4 sec with text

Here’s 1/2 sec with text

Here’s 1/10 sec w/o text

Here’s 1/2 sec w/o text

[/caption]

Highlights from the Comet Tempel 1 Post Flyby briefing

more Stardust goodies coming up

Read more about the Stardust-NExT Flyby and mission in my earlier stories here, here, here, here and here

Posted on by Nancy Atkinson

Another Must-Have Tool for Astronomers: A Shovel

Astronomer Scott Kardel on top of the 200-inch Hale Telescope at the Palomar Observatory shoveling snow. Image courtesy Scott Kardel.

Ah, the glamorous life of an astronomer. Scott Kardel, public affairs coordinator for the Palomar Observatory, found himself on top of the dome of the 200-inch Hale Telescope — not observing, but shoveling. Snow. Palomar Mountain has been getting its share of the white stuff this winter, and this weekend close to a foot of snow fell in the area. All that snow can cause problems for using the telescope.

“The basic problem is this,” Kardel wrote on his blog, Palomar Skies. “If you open the dome with snow on the top, snow will fall in on the telescope and instrumentation. So a small crew, each secured with a safety harness, is sent up to remove the snow from the dome slit.”

Kardel posted a nice collection of scenic images from his foray on top of the snow-covered dome, adding that, “At Palomar Observatory every day is an adventure.”

[/caption]

Posted on by Anne Minard

Film Review: Nostalgia for the Light (in Atacama)

The ESO's La Silla telescope site in the southern Atacama Desert, Chile. Credit: Iztok Boncina/ESO

[/caption]

It’s difficult enough to imagine stark white telescope domes towering over a parched brown landscape made even more arid by the near-constant whistle of high-altitude winds. It’s stranger still to consider that in the desert below those domes, tough and grieving women have been searching in vain for decades for the sun-bleached remains of loved ones stolen from them, killed and dumped in the void by Pinochet’s army.

Acclaimed Chilean film director Patricio Guzmán has woven these stories together into a documentary called Nostalgia de la Luz, or Nostalgia for the Light, that is both touching and stunning, human and other-worldly, emotional — and hopeful.

The film played at the Toronto International Film Festival and at Cannes before lighting up a packed theater at 10 a.m. on a Sunday morning in Boulder, Colorado, a community with a special fondness for space science owing partly to the presence of the Laboratory for Atmospheric and Space Physics, Ball Aerospace, NOAA’s Space Weather Prediction Center and the Southwest Research Institute.

In fact Jason Glenn, an astronomer at the University of Colorado at Boulder, took the podium for a few moments before the start of the film to announce plans for the Cornell-Caltech-Atacama (CCAT) telescope proposed to go atop the Chilean mountain Cerro Chajnantor — and to request donations toward its construction. CCAT, a submillimeter telescope, will be used to probe primeval galaxies, star formation and extra-solar planetary systems.

The film opens with awe-inspiring images of galaxies, close-up views of the pockmarked lunar surface, and eerily beautiful shots of the vast Atacama. The desert lies west of the Andes Mountains in Chile, and is generally regarded as the driest place on Earth. That, plus its high altitude, make it a perfect place for astronomy. The Atacama supports the ESO’s Atacama Large Millimeter/submillimeter Array (ALMA), the Very Large Telescope (VLT) and numerous other instruments. Many Chileans, the film intimates, grow up loving astronomy.

Meanwhile the people of Chile continue to heal from Pinochet’s bloody rule beginning in the early 1970s, when thousands of his political opponents were taken from their families and disappeared. The film captures the perspectives of people on all sides of the tragedy — from the grieving mothers and wives, the archeologists working to decipher both the recent and distant human past, survivors of Pinochet’s concentration camps and even astronomers who, tucked in offices underneath the massive telescope domes, might not seem to have much in common with the grieving women. But they do.

Gaspar Galaz, an astronomer at the Pontifical Catholic University of Chile, says in the film that both he and the women pursue quests to learn history; they’re all chasing rare clues in dauntingly vast spaces. Galaz peers far across the cosmos to study diffuse galaxies, whose origins are unknown, and the women comb the 40,600 square mile (105,000 km2) desert for minute fragments of bone. The difference: At the end of his workday, Galaz says, he can get a good night’s sleep, “but these women must have trouble sleeping after they search for human remains.”

Nostalgia de la Luz is worth seeing for any of its parts — the glimpses through the powerful Atacama telescopes, the desert scenes, the cultural insights or the beautifully human and optimistic ending, which I won’t give away here. Taken together, the film’s elements are an experience not to be missed.

Several trailers for Nostalgia de la Luz are available on YouTube; upcoming showtimes include, according to Facebook, March 8 and 9 at the Wexner Center for the Arts in Columbus, Ohio, March 18 at the IFC Film Center in New York and April 22-28 at Landmark’s Nuart Theater in LA. Today’s showing was at the Boulder International Film Festival.

Posted on by Anne Minard

Continent-Wide Telescope Array Now Seeing 450 Million Light-Years Into Space

Artist's conception of Milky Way, showing locations of star-forming regions whose distances were recently measured. CREDIT: M. Reid, Harvard-Smithsonian CfA; R. Hurt, SSC/JPL/Caltech, NRAO/AUI/NSF

[/caption]

Kitt Peak. Los Alamos. St. Croix. Pie Town.

What do these places have in common? They each house one of 10 giant telescopes in the Very Large Baseline Array, a continent-spanning collection of telescopes that’s flexing its optical muscles, reaching farther into space — with more precision — than any other telescope in the world.

And today, at the 177th annual meeting of the American Association for the Advancement of Science in Washington, DC, VLBA researchers announced an amazing feat: They’ve used the VLBA to peer, with stunning accuracy, three times as far into the universe as they had just two years ago. New measurements with the VLBA have placed a galaxy called NGC 6264 (coordinates below) at a distance of 450 million light-years from Earth, with an uncertainty of no more than 9 percent. This is the farthest distance ever directly measured, surpassing a measurement of 160 million light-years to another galaxy in 2009.

VLBA telescope locations, courtesy of NRAO/AUI

Previously, distances beyond our own Galaxy have been estimated through indirect methods. But the direct seeing power of the VLBA scraps the need for assumptions, noted James Braatz, of the National Radio Astronomy Observatory.

The VLBA provides the greatest ability to see fine detail, called resolving power, of any telescope in the world. It can produce images hundreds of times more detailed than those from the Hubble Space Telescope, at a power equivalent to sitting in New York and reading a newspaper in Los Angeles. VLBA sites include Kitt Peak, Arizona; Los Alamos and Pie Town, New Mexico; St. Croix in the Virgin Islands, Mauna Kea, Hawaii; Brewster, Washington; Fort Davis, Texas; Hancock, New Hampshire; North Liberty, Iowa; and Owens Valley in California. Sure, I could include pictures of the scopes in Hawaii or the Virgin Islands. But Pie Town, besides hosting the Very Large Array, also has two fun restaurants (the Daily Pie and the Pie-O-Neer) with really amazing pie. And an annual pie-eating festival. So it wins:

The VLBA site at Pie Town, N.M., courtesy of NRAO/AUI.

Tripling the visible “yardstick” into space bears favorably on numerous areas of astrophysics, including determining the nature of dark energy, which constitutes 70 percent of the Universe. The VLBA is also redrawing the map of the Milky Way and is poised to yield tantalizing new information about extrasolar planets, the NRAO points out.

Fine-tuning the measurement of ever-greater distances is vital to determining the expansion rate of the Universe, which helps theorists narrow down possible explanations for the nature of dark energy. Different models of Dark Energy predict different values for the expansion rate, known as the Hubble Constant.

“Solving the Dark Energy problem requires advancing the precision of cosmic distance measurements, and we are working to refine our observations and extend our methods to more galaxies,” Braatz said. Measuring more-distant galaxies is vital, because the farther a galaxy is, the more of its motion is due to the expansion of the Universe rather than to random motions.

As for the map of our own galaxy, the direct VLBA measurements are improving on earlier estimates by as much as a factor of two. The clearer observations have already revealed the Milky Way has four spiral arms, not two as previously thought.

Mark Reid, of the Harvard-Smithsonian Center for Astrophysics led an earlier VLBA study revealing that the Milky Way is also rotating faster than previously believed — and that it’s as massive as Andromeda.

Reid’s team is now observing the Andromeda Galaxy in a long-term project to determine the direction and speed of its movement through space. “The standard prediction is that the Milky Way and Andromeda will collide in a few billion years. By measuring Andromeda’s actual motion, we can determine with much greater accuracy if and when that will happen,” Reid said.

The VLBA is also being used for a long-term, sensitive search of 30 stars to find the subtle gravitational tug that will reveal orbiting planets. That four-year program, started in 2007, is nearing its completion. The project uses the VLBA along with NRAO’s Green Bank Telescope in West Virginia, the largest fully-steerable dish antenna in the world. Early results have ruled out any companions the size of brown dwarfs for three of the stars, and the astronomers are analyzing their data as the observations continue.

Ongoing upgrades in electronics and computing have enhanced the VLBA’s capabilities. With improvements now nearing completion, the VLBA will be as much as 5,000 times more powerful as a scientific tool than the original VLBA of 1993.

NGC 6264 Coordinates, from DOCdb: 16<sup>h</sup> 57<sup>m</sup> 16.08<sup>s</sup>; +27° 50′ 58.9″

Source: A press release from the National Radio Astronomy Observatory, via the American Astronomical Society (AAS). Not to be confused with the American Association for the Advancement of Science (AAAS), which now conducting its annual meeting in Washington, DC — and where the VLBA results were presented.

Posted on by Ken Kremer

Sun Erupts with Enormous X2 Solar Flare

Active region 1158 let loose with an X2.2 flare late on February 15, taken by NASA's Solar Dynamics Observatory in the extreme ultraviolet wavelength of 193 Angstroms. Much of the vertical line in the image is caused by the bright flash overwhelming the SDO imager. Credit: NASA/SDO

Just in time for Valentine’s Day, [and the Stardust flyby of Comet Tempel 1] the Sun erupted with a massive X-Class flare, the most powerful of all solar events on February 14 at 8:56 p.m. EST . This was the first X-Class flare in Solar Cycle 24 and the most powerful X-ray flare in more than four years.

The video above shows the flare as imaged by the AIA instrument at 304 Angstroms on NASA’s Solar Dynamics Observatory. More graphic videos below show the flare in the extreme ultraviolet wavelength of 193 Angstroms and as a composite with SOHO’s coronagraph.

Spaceweather Update: A CME hit Earth’s magnetic field at approximately 0100 UT on Feb. 18th (8:00 pm EST on Feb. 17th). Send me or comment your aurora photos

The eruption registered X2 on the Richter scale of solar flares and originated from Active Region 1138 in the sun’s southern hemisphere. The flare directly follows several M-class and C-class flares over the past few days which were less powerful. The explosion also let loose a coronal mass ejection (CME) headed for Earth’s orbit. It was speeding at about 900 Km/second.
CME’s can disrupt communications systems and the electrical power grid and cause long lasting radiation storms.

According to a new SDO update, the particle cloud from this solar storm is weaker than first expected and may produce some beautiful aurora in the high northern and southern latitudes on Feb. 17 (tonight).

According to spaceweather.com, skywatchers in the high latitudes should be alert for auroras after nightfall Feb. 17 from this moderately strong geomagnetic storm.

Send me your aurora reports and photos to post here

Sources: SDO website, spaceweather.com

NASA SDO – Big, Bright Flare February 15, 2011

Video Caption: Active region 1158 let loose with an X2.2 flare at 0153 UT or 8:50 pm ET on February 15, 2011, the largest flare since Dec. 2006 and the biggest flare so far in Solar Cycle 24. Active Region 1158 is in the southern hemisphere, which has been lagging the north in activity but now leads in big flares! The movie shows a close-up of the flaring region taken by the Solar Dynamics Observatory in the extreme ultraviolet wavelength of 193 Angstroms. Much of the vertical line in the image and the staggered lines making an “X” are caused by the bright flash overwhelming our imager. A coronal mass ejection was also associated with the flare. The movie shows activity over about two days (Feb. 13-15, 2011). Since the active region was facing Earth, there is a good chance that Earth will receive some effects from these events, with some possibility of mid-latitude aurora Feb. 16 – 18. Credit: NASA SDO

X2 flare Video combo from SDO and SOHO

Video caption: The X2 flare of Feb. 15, 2011 seen by SDO (in extreme ultraviolet light) enlarged and superimposed on SOHO’s coronagraph that shows the faint edge of a “halo” coronal mass ejection as it races away from the Sun. The video covers about 11 hours

[/caption]

This image taken by SDO's AIA instrument at 171 Angstrom shows the current conditions of the quiet corona and upper transition region of the Sun. Credit: NASA/SDO/AIA
Posted on by Anne Minard

First-Time Views of Solar System Births

SUBARU Telescope image of the protoplanetary disk around the young star LkCa 15. Credit: MPIA (C. Thalmann) & NAOJ

[/caption]

Chalk up a sizzling success for the HiCIAO planet-hunter camera on the Subaru Telescope in Hawaii: it’s captured this unprecedented image of a stellar disk similar in size to our own solar system, featuring rings and gaps that are associated with the formation of giant planets.

The lead image shows a bright arc of scattered light, in white, from the protoplanetary disk around the young star LkCa 15.  LkCa 15 is in the center of the image, blacked out. The arc’s sharp inner edge traces the outline of a wide gap in the disk. The gap is decidedly lopsided – it is markedly wider on the left side – and has most likely been carved out of the disk by one or more newborn planets that orbit the star.

The disk gap is large enough to house the orbits of all the planets in our own Solar System. “We haven’t detected the planets themselves yet,” said Christian Thalmann, who led the LkCa 15 study while on staff at the Max Planck Institute for Astronomy.”But that may change soon.”

LkCa 15, aged a few million years, is in the Taurus constellation about 450 light years away.

The observations are part of a systematic survey called SEEDS, or the Strategic Explorations of Exoplanets and Disks with Subaru Project, with a goal to search for planets and disks around young stars using HiCIAO, a state-of-the-art high-contrast camera designed specifically for this purpose. The lead investigator on the project is Motohide Tamura at the National Astronomical Observatory of Japan, but it’s a collaborative effort with international participation. Their first significant discovery — an exoplanet candidate around a sun-like star — was announced in December.

Besides LkCa 15, the researchers have also captured a sharp images of the protoplanetary disk around the very young star AB Aur in the constellation Auriga, “the Charioteer.” Lead researcher Jun Hashimoto, of the National Observatory of Japan, and his team report nested rings of material that are tilted with respect to the disk’s equatorial plane, and whose material, intriguingly, is not distributed symmetrically around the star – irregular features that indicate the presence of at least one very massive planet.

Recent images of AB Aur taken by HiCIAO (top left), compared with an image taken in 2004 by its predecessor instrument CIAO (top right). The new images give a much more detailed view of the inner regions (bottom left; with explanations bottom right): Intricate bright and dark patterns indicate the presence of different rings of matter. The fact that their centers do not coincide with the position of the star and the other irregularities point to the existence of a massive giant planet which is sweeping up the material between the rings. Credit: NAOJ/J. Hashimoto

The researchers point out that no other telescopes, whether ground-based or in space, have ever penetrated so close to a central star, showing the details of its disk.

Planetary systems like our own share a humble origin as mere by-products of star formation. A newborn star’s gravity gathers leftover gas and dust in a dense, flattened disk of matter orbiting the star. Clumps in the disk sweep up more and more material, until their own gravity becomes sufficiently strong to compress them into the dense bodies we know as planets.

Sources: Max Planck Institute For Astronomy, National Observatory of Japan.

Links to the published results:

Thalmann, C. et al., Imaging of a Transitional Disk Gap in Reflected Light: Indications of Planet Formation Around the Young Solar Analog LkCa 15 in Astrophysical Journal Letters 718, p. L87-L91

Hashimoto, J. et al., accepted for publication in Astrophysical Journal Letters in January 2011.

Posted on by Anne Minard

Hubble Zeroes in on Hot, Young Stars

Flocculent Spiral NGC 2841, in the constellation Ursa Major. Credit: NASA, ESA and Hubble

[/caption]

The Flocculent Spiral NGC 2841, shown above, is known for its profusion of young, blue stars. And yet, until recently, astronomers haven’t been able to use those stars as windows into the still-mysterious phenomenon of star formation.

Hubble’s most recent wide-field camera upgrade is changing that.

The new Wide Field Camera 3 (WFC3) was installed on Hubble in May 2009 during Servicing Mission 4, and replaces the Wide Field and Planetary Camera 2. The new camera is optimized to observe in the infrared and ultraviolet wavelengths emitted by newborn stars, shown by the bright blue clumps in the lead image. Thus, it can peer behind the veil of dust that would otherwise hide those stars from view.

The image shows a lot of hot, young stars in the disc of NGC 2841, but in reality there are just a few sites of current star formation where hydrogen gas is collapsing into new stars. It is likely that these fiery youngsters destroyed the star-forming regions in which they were formed.

Image from NASA's Galaxy Evolution Explorer (GALEX), via the NASA/IPAC Extragalactic Database

NGC 2841 is about 46 million light years away in the constellation Ursa Major. It’s part of a common group of galaxies called flocculent spirals; flocculent means fluffy or wooly-looking. Rather than boasting well-defined spiral arms, these galaxies display patchy stellar distribution.

Star formation is one of the most important processes shaping the Universe; it plays a pivotal role in the evolution of galaxies and it is also in the earliest stages of star formation that planetary systems first appear. Yet there is still much that astronomers don’t understand, such as how the properties of stellar nurseries vary according to the composition and density of the gas present, and what triggers star formation in the first place. The driving force behind star formation is particularly unclear for flocculent spirals.

An international team of astronomers is using Hubble’s WFC3 to study a sample of nearby, but wildly differing, locations where stars are forming. The observational targets include both star clusters and galaxies, and star formation rates range from the baby-booming starburst galaxy Messier 82 to the much more sedate star producer NGC 2841.

Source: Eurekalert. See also this NASA description and image of flocculent spiral NGC 4414.

Detailed credit information for the lead image: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration Acknowledgment: M. Crockett and S. Kaviraj (Oxford University, UK), R. O’Connell (University of Virginia), B. Whitmore (STScI) and the WFC3 Scientific Oversight Committee.

Posted on by Ken Kremer

NASA’s Stardust Discovers Human made Deep Impact Crater on Comet Tempel 1

Tempel 1, as Seen by Two Spacecraft. These two images show the different views of comet Tempel 1 seen by NASA's Deep Impact spacecraft (left) and NASA's Stardust spacecraft (right). Two craters, about 300 meters (1,000 feet) in diameter, help scientists locate the area hit by the impactor released by Deep Impact in July 2005. The dashed lines correlate the features. Stardust approached the comet from a different angle on Feb. 14, 2011. Credit: NASA/JPL-Caltech/University of Maryland/Cornell

[/caption]
NASA’s aging and amazing Stardust space probe has at last discovered the human made crater created on Comet Tempel 1 in 2005 by the history making cosmic smash up with NASA’s Deep Impact penetrator. Stardust streaked past the comet on Feb. 14 at 10.9 km/sec, or 24,000 MPH, and succeeded in briefly photographing the crater as it approached within 178 km (111 mi) during the fleeting moments of the probes closest approach.

The intentional celestial collision in 2005 was designed to violently unleash the buried remnants of the early solar system into an enormous ejecta cloud of dusty debris that scientists could sift for clues to help unlock the secrets of how we all formed and evolved some 4.5 Billion Years ago.

Tempel 1 is the first comet to receive a second visit by probes from Earth.

Comets have continuously smashed into Earth over the eons and delivered vast quantities of key ingredients – such as water and organic molecules – that may have sparked the formation of life on the early Earth.

NASA approved the use of the already orbiting Stardust-NExT spacecraft to follow up on the science discoveries by Deep Impact as the best and most economical way to try and locate the crater blast site, image new terrain and look for changes on the comets surface since the 2005 mission as the comet also completed another orbit around our Sun and eroded due to solar heating.

The human made crater is about 150 meters wide and was formed by a 375 kilogram (800 pound) projectile propelled into the speeding path of Comet Tempel 1 by the Deep Impact mothership in 2005.

Tempel 1 Impact Site.
This pair of images shows the before-and-after comparison of the part of comet Tempel 1 that was hit by the impactor from NASA's Deep Impact spacecraft. The left-hand image is a composite made from images obtained by Deep Impact in July 2005. The right-hand image shows arrows identifying the rim of the crater caused by the impactor. The crater is estimated to be 150 meters (500 feet) in diameter. This image also shows a brighter mound in the center of the crater likely created when material from the impact fell back into the crater. Credit: NASA/JPL-Caltech/University of Maryland/Cornell

Stardust-NExT took 72 high resolution science images of the comet during the Valentine’s Day encounter flyby on Feb, 14 at 11:40 p.m. EST (8:40 p.m. PST). The probe absolutely had to be precisely navigated to exactly hit the aim point for sequencing the images to match the right moment in the erratic rotation of the volatile comet.

The results of the Stardust-NExT mission were announced at a post encounter new briefing after most of the images and science data had streamed back to Earth. The science team and NASA said that all the mission objectives were accomplished.

“If you ask me was this mission 100 percent successful in terms of the science, I’d have to say no. It was 1000 percent successful!” said Stardust-NExT principal investigator Joe Veverka of Cornell University, Ithaca, N.Y., at the news briefing.

“We found the Deep Impact crater. We see erosion in comparison to 2005. So we do see changes. Erosion on the scale of 20 to 30 meters of material has occurred in the five or six years since we took the first picture. We are seeing a change, but we have to spend time quantifying the changes and understanding what they mean.”

“We saw a lot of new territory. It’s amazing with lots of layers. There is lots of surface sublimation. We had to arrive at precisely the right time in order to see new and old territory.”

“We had monitored the comets rotation for several years. And we got the longitude almost perfect within 1 or 2 degrees,” Veverka said.

Tempel 1 Impact Site
Credit: NASA/JPL-Caltech/University of Maryland/Cornell

It took a few years of careful study to deduce the comets complex rotational patterns which change as the body orbits in a wide orbital path between Mars and Jupiter and is heated by the sun.

Peter Schultz, a science team co-investigator agreed and showed the comparison images.

“We saw the crater,” said Schultz, of University. “It’s subdued; it’s about 150 meters across and has a small central mound in the center. It looks as if from the impact, the stuff went up and came back down. So we did get it, there’s no doubt. I think one of the bottom-line messages is that this surface of the comet where we hit is very weak. It’s fragile. So the crater partly healed itself.”

“It was about the size we expected. But more subdued.”

The probes mission is almost complete since it has very little fuel left. The remaining science data from the flyby is being sent back and some outbound data is being collected.

“This spacecraft has logged over 3.5 billion miles since launch, and while its last close encounter is complete, its mission of discovery is not,” said Tim Larson, Stardust-NExT project manager at JPL. “We’ll continue imaging the comet as long as the science team can gain useful information, and then Stardust will get its well-deserved rest.”

Stardust-NExT is a repurposed spacecraft that has journeyed nearly 6 billion kilometers since it was launched in 1999.

Initially christened as Stardust, the spaceships original task was to fly by Comet Wild 2 in 2004. It also collected priceless cometary dust particles from the coma which was safely parachuted back to Earth inside a return canister in 2006. High powered science analysis of the precious comet dust will help researchers discern the origin and evolution of our solar system.

This was humanities first revisit to a comet and at a bargain basement price by using an old spacecraft already in space.

“The cost was just $29 Million dollars. A new Discovery class mission costs $300 to 500 Million. So that’s maybe 6% the cost of developing and launching a new mission,” said Ed Weiler, the associate administrator for NASA’s Science Mission Directorate at NASA HQ in Washington, DC.

Read more about the Stardust-NExT Flyby and mission in my earlier stories here, here, here and here

Changes to Smooth Terrain (Annotated)
This image layout depicts changes in the surface of comet Tempel 1, observed first by NASA's Deep Impact Mission in 2005 (top right) and again by NASA's Stardust-NExT mission on Feb. 14, 2011 (bottom right). Between the two visits, the comet made one trip around the sun. The image at top left is a wider shot from Deep Impact. The smooth terrain is at a higher elevation than the more textured surface around it. Scientists think that cliffs, illustrated with yellow lines to the right, are being eroded back to the left in this view. The cliffs appear to have eroded as much as 20 to 30 meters (66 to 100 feet) in some places, since Deep Impact took the initial image. The box shows depressions that have merged together over time, also from erosion. This erosion is caused by volatile substances evaporating away from the comet. Credit: NASA/JPL-Caltech/University of Maryland/Cornell
Posted on by Anne Minard

Galaxy Size Matters … And This is Not a Rorschach Test

False color image of the Lockman-hole area of the sky at infrared wavelengths as imaged by the Herschel Space Observatory. Credit: ESA/SPIRE Consortium/HerMES Consortium

[/caption]

When it comes to forming stars, the size of a galaxy does matter, according to research out today in the online version of Nature.

But it doesn’t have to be as massive as we once thought.

Alexandre Amblard, an astrophysicist at the University of California, Irvine, and his colleagues used new data from the Herschel Space Observatory to peer into Lockman Hole area of the sky, where extragalactic light comes from star-forming galaxies out of reach for even the world’s most powerful telescopes.

The Lockman Hole is a patch of the sky, 15 square degrees, lying roughly between the pointer stars of the Big Dipper.

Called submillimetre galaxies, the study subjects emit light at wavelengths between the radio and infrared parts of the spectrum, so studying them requires novel approaches borrowing from both radio and optical astronomy. The galaxies by themselves are too blurry to be resolved with individual far-infrared telescopes – but their average properties can be observed and analyzed, which is exactly what Amblard and his colleagues did.

The authors measured variations in the intensity of extragalactic light at far-infrared wavelengths, and derived statistics for the level of clustering of light halos. They assume that the clustering reflects the underlying distribution of dark matter, and fit the data to a halo model of galaxy formation, which connects the spatial distribution of galaxies in the Universe to that of dark matter.

Distribution of dark matter when the Universe was about 3 billion years old, obtained from a numerical simulation of galaxy formation. The left panel displays the continuous distribution of dark matter particles, showing the typical wispy structure of the cosmic web, with a network of sheets and filaments, while the right panel highlights the dark matter halos representing the most efficient cosmic sites for the formation of star-bursting galaxies with a minimum dark matter halo mass of 300 billion times that of the Sun. Credit: VIRGO Consortium/Alexandre Amblard/ESA

Amblard and his colleagues discovered an enormous fact: the ‘haloes’ of dark matter that surround the Universe’s most active star-forming galaxies are each more massive than about 300 billion solar masses.

What’s even more interesting is that the new threshold for star formation is actually smaller than some previous estimates.

“I think there was one prediction that put the number around 5000 billion times that of the sun, but that was just a prediction from a theory of galaxy formation.“ said Asantha Cooray, also an astrophysicist at UC Irvine and second author on the new paper. “The general consensus was that it may be between 100 to 1000 billion times the sun. We now have a more precise answer from this work.”

Cooray said he’s most excited “that we can look at a detailed image of the sky showing distant, star-forming galaxies and infer not only details about the stars and gas in those galaxies but also about the amount of dark matter needed to form such galaxies. Beyond inferring the presence, we still don’t know exactly what dark matter is.”

The results appear online ahead of print today on Nature’s website.