Posted on by Fraser Cain

Will We Find Super Earths?


An extrasolar planet with hypothetical (possible but unproven) water-bearing moons. Image credit: NASA/IPAC/R. Hurt. Click to enlarge
Over the past decade, astronomers using a planet-hunting technique that measures small changes in a star’s speed relative to Earth, have discovered more than 130 extrasolar planets. The first such planets were gas giants, the mass of Jupiter or larger. After several years, the scientists began to detect Saturn-mass planets. And last August, they announced the discovery of a handful of Neptune-mass planets. Could these be super-Earths?

In a recent talk at a symposium on extrasolar planets, Carnegie Institution of Washington astronomer Alan Boss explained the possibilities.

Radial-velocity planet-hunting techniques recently have pushed our discovery capability below the Saturn-mass limit down into what we would call the ice-giant limit.

So we are now able to find planets, close to their host stars, with masses comparable to that of Uranus and Neptune (14 to 17 times the mass of Earth).

In large part this is due to Michel Mayor and his colleagues having a new spectrometer in La Silla, which has unprecedented spectral resolution down to about 1 meter per second or so. And I think Geoff Marcy and Paul Butler’s group are quite close behind that as well.

The interesting question, though, is: What are these things? Are they ice giants that formed several AUs out and migrated in, or are they something else? Unfortunately, we don’t know exactly what their masses are. Even more importantly, we don’t really know what their density is. So they could be 15-Earth-mass rocks, or they could be 15-Earth-mass ice giants.

What we really need to do is to have folks go out and discover another 7 or so. We’ve got 3 so far. If we had 10 altogether, then we’ll have enough that 1 of them, at least, should transit its star and then we’ll be able to get some idea of what its density is.

I think, though, that there’s a good chance that these might actually be a new class of planet altogether: super-Earths. The reason I would argue that is that, at least in 2 of the systems where they’ve been found, these “hot Neptunes” are accompanied by a larger Jupiter-mass planet with a longer-period orbit.

If the lower-mass planets are ice giants that formed far from their stars, unless you have some highly contrived scenario, you wouldn’t imagine them to end up migrating inward, past the larger guys. These systems look more like our own solar system, where you have the low-mass fellows inside of the gas giants.

The planets in a system like our system presumably did not undergo very much migration. So I would claim that perhaps these guys are objects which formed inside the gas giants and only migrated in a little bit, ending up where we can detect them with the short-period spectroscopy surveys.

In support of this idea, there’s some theoretical work from Carnegie’s George Wetherill from almost 10 years ago, now, where he had done some calculations of the accumulation process of rocky planets. He often found there was quite a spread in the masses of what you got out, because accumulation’s a very stochastic process. For the typical parameters he used, at the end of 100 million years or so, he would not only get objects of 1 Earth mass, but also objects ranging up to 3 Earth masses.

Well, at the time, he assumed for his calculations a fairly low surface density at 1 AU, where these planets were forming. Given what we know now, if you want to be able to make a Jupiter at 5 AU using the core-accretion model of planetary formation, you have to crank up the density in the protoplanetary disk by a factor of 7 or so over what Wetherill assumed.

That scales directly with the mass of the planets you’d expect to find as a result. So if you did these calculations over again, assuming this higher initial density, the upper limit on the mass of the inner planets would go from 3 Earth masses, which is what Wetherill got, up to say 21 Earth masses. That is in the range of what we are estimating for these newly discovered hot Neptune-mass objects.

So perhaps what we really are seeing is a new class of objects, super-Earths, rather than ice giants.

Original Source: NASA Astrobiology

Posted on by Fraser Cain

Three Space Telescopes Find a Neutron Star

Artist’s impression of neutron star IGR J16283-4838. Image Credit:NASA/Dana Berry. Click to enlarge
An international team of scientists has uncovered a rare type of neutron star so elusive that it took three satellites to identify it.

The findings, made with ESA?s Integral satellite and two NASA satellites, reveals new insights about star birth and death in our Galaxy. We report this discovery, highlighting the complementary nature of European and US spacecraft, on the day in which ESA?s Integral celebrates 1000 days in orbit.
The neutron star, called IGR J16283-4838, is an ultra-dense ?ember? of an exploded star and was first seen by Integral on 7 April 2005. This neutron star is about 20,000 light years away, in a ?double hiding place?. This means it is deep inside the spiral arm Norma of our Milky Way galaxy, obscured by dust, and then buried in a two-star system enshrouded by dense gas.

?We are always hunting for new sources,? said Simona Soldi, the scientist at the Integral Science Data Centre in Geneva, Switzerland, who first saw the neutron star. ?It is exciting to find something so elusive. How many more sources like this are out there??

Neutron stars are the core remains of ?supernovae?, exploded stars once about ten times as massive as our Sun. They contain about a Sun’s worth of mass compacted into a sphere about 20 kilometres across.

?Our Galaxy?s spiral arms are loaded with neutron stars, black holes and other exotic objects, but the problem is that the spiral arms are too dusty to see through,? said Dr Volker Beckmann at NASA Goddard Spaceflight Centre, lead author of the combined results.

?The right combination of X-ray and gamma-ray telescopes could reveal what is hiding there, and provide new clues about the true star formation rate in our Galaxy,? he added.

Because gamma rays are hard to focus into sharp images, the science team then used the X-ray telescope on Swift to determine a precise location. In mid April 2005, Swift confirmed that the light was ?highly absorbed?, which means the binary system was filled with dense gas from the stellar wind of the companion star.

Later the scientists used the Rossi Explorer to observe the source as it faded away. This observation revealed a familiar light signature, clinching the case for a fading high-mass X-ray binary with a neutron star.

IGR J16283-4838 is the seventh so-called ?highly absorbed?, or hidden neutron star to be identified. Neutron stars, created from fast-burning massive stars, are intrinsically tied to star formation rates. They are also energetic ?beacons? in regions too dusty to study in detail otherwise. As more and more are discovered, new insights about what is happening in the Galaxy’s spiral arms begin to emerge.

IGR J16283-4838 revealed itself with an ?outburst? on or near its surface. Neutron stars such as IGR J16283-4838 are often part of binary systems, orbiting a normal star. Occasionally, gas from the normal star, lured by gravity, crashes onto the surface of the neutron star and releases a great amount of energy. These outbursts can last for weeks before the system returns to dormancy for months or years.

Integral, the Rossi Explorer and Swift all detect X-rays and gamma rays, which are far more energetic than the visible light that our eyes detect. Yet each satellite has different capabilities. Integral has a large field of view, enabling it to scan our Milky Way galaxy for neutron stars and black hole activity.

Swift contains a high-resolution X-ray telescope, which allowed scientists to zoom in on IGR J16283-4838. The Rossi Explorer has a timing spectrometer, a device used to uncover properties of the light source, such as speed and rapid variations in the order of milliseconds.

Original Source: ESA Portal

Posted on by Fraser Cain

Prometheus Shepherding the Rings

Saturn’s shepherd moon Prometheus hovers between the A and F rings. Image credit; NASA/JPL/SSI. Click to enlarge
Saturn’s shepherd moon Prometheus hovers between the A and F rings as if suspended on an invisible thread, while bright clouds drift in Saturn’s atmosphere approximately 130,000 kilometers (81,000 miles) beyond. It is noteworthy that such clouds are visible here in the shadows cast by the rings. Prometheus is 102 kilometers (63 miles) across.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on June 3, 2005, at a distance of approximately 2.1 million kilometers (1.3 million miles) from Saturn. The image scale is 13 kilometers (8 miles) per pixel. This view was processed to enhance fine details.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org.

Original Source: NASA/JPL/SSI News Release

Posted on by Fraser Cain

Supercomputer Will Study Galaxy Evolution

This view of nearly 10,000 galaxies is the deepest visible-light image of the cosmos. Image credit: Hubble. Click to enlarge
One of the fastest supercomputers in the world and the first ever designed specifically to study the evolution of star clusters and galaxies is now in operation at Rochester Institute of Technology.

The new computer, built by David Merritt, professor of physics in RIT?s College of Science, uses a novel architecture to reach speeds much higher than that of standard supercomputers of comparable size.

Known as gravitySimulator, the computer is designed to solve the ?gravitational N-body problem?. It simulates how a galaxy evolves as the stars move about each other in response to their own gravity. This problem is computationally demanding because there are so many interactions to calculate requiring a tremendous amount of computer time. As a result, standard supercomputers can only carry out such calculations with thousands of stars at a time.

The new computer achieves much greater performance by incorporating special accelerator boards, called GRAPEs or Gravity Pipelines, into a standard Beowulf-like cluster. The gravitySimulator, which is one of only two machines of its kind in the world, achieves a top speed of 4 Teraflops, or four trillion calculations per second, making it one of the 100 fastest computers in the world, and it can handle up to 4 million stars at once. The computer cost over $500,000 to construct and was funded by RIT, the National Science Foundation, and NASA.

Since gravitySimulator was installed in the spring, Merritt and his associates have been using it to study the binary black hole problem- what happens when two galaxies collide and their central, supermassive black holes form a bound pair.

?Eventually the two black holes are expected to merge into a single, larger black hole,? Merritt says. ?But before that happens, they interact with the stars around them, ejecting some and swallowing others. We think we see the imprints of this process in nearby galaxies, but so far no one has carried out simulations with high enough precision to test the theory.?

Merritt and his team will also use gravitySimulator to study the dynamics of the central Milky Way Galaxy in order to understand the origin of our own black hole.

Merritt sees the gravitySimulator as an important example of RIT?s development as a major scientific research institute. ?Our unique combination of in-class instruction, experiential learning and research will be a major asset in the continued development of astrophysics and other research disciplines here at RIT,? Merritt says. ?The gravitySimulator is the perfect example of the cutting edge work we are already doing and will be a major stepping stone for the development of future scientific research.?

Original Source: RIT News Release

Posted on by Fraser Cain

Sloan Digital Sky Survey, Part II

NGC 5919 is a member of a galaxy cluster Abel 2063. Image credit: SDSS. Click to enlarge.
Dr. Richard Kron, director of the Sloan Digital Sky Survey, announced a new undertaking that will complete the largest survey of the universe. This survey will add new partners and undertake new research missions, and will run through summer 2008.

Late last month the funding package for a new, three-year venture called the Sloan Digital Sky Survey II (SDSS-II) was completed, led by the Alfred P. Sloan Foundation of New York City, the National Science Foundation (NSF), the U.S. Department of Energy and the member institutions.

The SDSS has been carrying out a massive survey of the sky using a dedicated 2.5-m telescope at Apache Point Observatory near Sunspot, New Mexico. SDSS-II will complete observations of a huge contiguous region of the Northern skies and will study the structure and origins of the Milky Way Galaxy and the nature of dark energy.

The Sloan Digital Sky Survey is the most ambitious astronomical survey project ever undertaken, already having measured precise brightnesses and positions for hundreds of millions of galaxies, stars and quasars during the last five years. The consortium of more than 300 scientists and engineers at 23 institutions around the world — and hundreds of other scientists working in collaboration — are using these data to address fascinating and fundamental questions about the universe.

The exciting results from the SDSS data to date include the discovery of distant quasars seen when the universe was just 900 million years old; the definitive measurement of the large-scale distribution of galaxies, confirming the role of gravity in growing structures in the universe; and evidence that the Milky Way Galaxy grew by cannibalizing smaller companion galaxies.

“We are very excited with the funding agencies’ decision to support this important mission,” said Kron of the University of Chicago. “The dedicated scientists and engineers of the Sloan Digital Sky Survey have worked tirelessly to open new ways of seeing the Universe.

“We believe the SDSS II discoveries that lie ahead will further scientific discoveries and lay the groundwork for future astronomical exploration. We are sure that the data released to the public will yield discoveries for years to come.”

In the last five years, the SDSS has released data for almost 200 million objects to the public. These data have been used by hundreds of researchers around the world for scientific projects ranging from studies of nearby stars to explorations of the nature of galaxies.

“We are proud of the landmark contributions made by the Sloan Digital Sky Survey to our understanding of the evolution and structure of the universe and enthusiastically support this next phase of research,” said Doron Weber, program director of the Alfred P. Sloan Foundation. “The findings of the Sloan Digital Sky Survey have already produced the most accurate picture of the skies that has ever existed and we expect new discoveries that will continue to transform our knowledge of the universe.”

Eileen D. Friel, Executive Officer of the Division of Astronomical Sciences at the National Science Foundation, said the Sloan Digital Sky Survey “has enabled a remarkable array of scientific results, sometimes in unexpected areas. The completion of the original survey and its extension to address issues in galactic and stellar astronomy promises to strengthen the legacy of the survey and to make it an even more valuable resource for astronomers and educators.”

And Robin Staffin, Associate Director of Science for High Energy Physics in the Department of Energy’s Office of Science, said the agency was “delighted to see the Sloan Digital Sky Survey entering this new phase. SDSS has already contributed a great deal to our understanding of the fundamental structure of the universe, and has helped pioneer the connections between particle physics and cosmology. We expect that great science will come out of SDSS-II over the next few years.”

With the formation of SDSS-II, eight new institutions join the collaboration: American Museum of Natural History in New York City, the University of Basel (Switzerland), Cambridge University (UK), Case Western Reserve University in Cleveland, Ohio, the Joint Institute for Nuclear Astrophysics (University of Notre Dame, Michigan State University, and The University of Chicago), The Kavli Institute for Particle Astrophysics and Cosmology at Stanford, Ohio State University, and the Astrophysical Institute Potsdam (Germany). (A complete list of SDSS-I and SDSS-II partners can be found below).

SDSS-II has three components. The first, called LEGACY, will complete the SDSS survey of the extragalactic universe, obtaining images and distances of nearly a million galaxies and quasars over a continuous swath of sky in the Northern Hemisphere.

The new funding also inaugurates the second part of SDSS-II, the Sloan Extension for Galactic Understanding and Exploration (SEGUE), mapping the structure and stellar makeup of the Milky Way Galaxy, and gathering data on how the Milky Way formed and evolved.

“The SEGUE project will allow us for the first time to get a ‘big picture’ of the structure of our own Milky Way,” explained consortium member Heidi Newberg of Rensselaer Polytechnic Institute. “The mapping of the Milky Way is more than an exercise in cartography. Ages, chemical compositions, and space distribution of stars are major clues to understanding how our own Galaxy formed, and, by example, how galaxies, in general. formed.

“Identifying the oldest stars will help us understand how the elements of the periodic table were formed long ago inside of stars,” Newberg said.

The final piece of SDSS-II includes an intensive study of supernovae, sweeping the sky to find these remnants of gigantic explosions from dying stars. Astronomers can precisely measure the distances of distant supernovae, using them to map the rate of expansion of the universe.

“This study will help to verify and quantify one of the most important discoveries of modern science – the existence of the cosmological dark energy,” explained consortium member Andy Becker of the University of Washington.

Becker explained that the SDSS telescope is uniquely positioned to both discover, and follow up on, a wealth of supernovae at distances at which other surveys have found very few objects. This allows a direct measurement of the effects of dark energy on the geometry of the universe as a whole.

Original Source: SDSS News Release

Posted on by Fraser Cain

Strange Hyperion Looks Like a Sponge

Saturn’s unusual moon, Hyperion. Image credit: NASA/JPL/SSI. Click to enlarge.
Two new Cassini views of Saturn’s tumbling moon Hyperion offer the best looks yet at one of the icy, irregularly-shaped moons that orbit the giant, ringed planet.

The image products released today include a movie sequence and a 3D view, and are available at , and .

The views were acquired between June 9 and June 11, 2005, during Cassini’s first brush with Hyperion.

Hyperion is decidedly non-spherical and its unusual shape is easy to see in the movie, which was acquired over the course of two and a half days. Jagged outlines visible on the moon’s surface are indicators of large impacts that have chipped away at its shape like a sculptor.

Preliminary estimates of its density show that Hyperion is only about 60 percent as dense as solid water ice, indicating that much of its interior (40 percent or more) must be empty space. This makes the moon more like an icy rubble pile than a solid body.

In both the movie and the 3D image, craters are visible on the moon?s surface down to the limit of resolution, about 1 kilometer (0.6 mile) per pixel. The fresh appearance of most of these craters, combined with their high spatial density, makes Hyperion look something like a sponge.

The moon’s spongy-looking exterior is an interesting coincidence, as much of Hyperion?s interior appears to consist of voids. Hyperion is close to the size limit where, like a child compacting a snowball, internal pressure due to the moon?s own gravity will begin to crush weak materials like ice, closing pore spaces and eventually creating a more nearly spherical shape.

The images used to create these views were obtained with Cassini’s narrow-angle camera at distances ranging from approximately 815,000 to 168,000 kilometers (506,000 to 104,000 miles) from Hyperion. Cassini will fly within 510 kilometers (317 miles) of Hyperion on Sept. 26, 2005.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

Original Source: NASA News Release

Posted on by Fraser Cain

Astronomy Hacks Giveaway

The fine folks at O’Reilly Media have agreed to give away a free copy of their book, Astronomy Hacks, to one lucky Universe Today reader – click here to read our review. Just send me an email at [email protected] with the subject line Astronomy Hacks Giveaway by Friday, July 15 at 12:00 pm Pacific Daylight Time. I’ll choose one email from the list at random, and we’ll send you a copy of the book. (Don’t worry, I won’t save the addresses, I’ll delete all your emails right after I do the drawing.)

Good luck!

Fraser Cain
Publisher, Universe Today

Posted on by Fraser Cain

Old NASA Equipment Will Be Visible on the Moon

Apollo 17 rover on the Moon. Image credit: NASA. Click to enlarge.
Inside the lunar lander Challenger, a radio loudspeaker crackled.

Houston: “We’ve got you on television now. We have a good picture.”

Gene Cernan, Apollo 17 commander: “Glad to see old Rover’s still working.”

“Rover,” the moon buggy, sat outside with no one in the driver’s seat, its side-mounted TV camera fixed on Challenger. Back in Houston and around the world, millions watched. The date was Dec. 19, 1972, and history was about to be made.

Suddenly, soundlessly, Challenger split in two (movie). The base of the ship, the part with the landing pads, stayed put. The top, the lunar module with Cernan and Jack Schmitt inside, blasted off in a spray of gold foil. It rose, turned, and headed off to rendezvous with the orbiter America, the craft that would take them home again.

Those were the last men on the Moon. After they were gone, the camera panned back and forth. There was no one there, nothing, only the rover, the lander and some equipment scattered around the dusty floor of the Taurus-Littrow valley. Eventually, Rover’s battery died and the TV transmissions stopped.

That was our last good look at an Apollo landing site.

Many people find this surprising, even disconcerting. Conspiracy theorists have long insisted that NASA never went to the Moon. It was all a hoax, they say, a way to win the Space Race by trickery. The fact that Apollo landing sites have not been photographed in detail since the early 1970s encourages their claims.

And why haven’t we photographed them? There are six landing sites scattered across the Moon. They always face Earth, always in plain view. Surely the Hubble Space Telescope could photograph the rovers and other things astronauts left behind. Right?

Wrong. Not even Hubble can do it. The Moon is 384,400 km away. At that distance, the smallest things Hubble can distinguish are about 60 meters wide. The biggest piece of left-behind Apollo equipment is only 9 meters across and thus smaller than a single pixel in a Hubble image.

Better pictures are coming. In 2008 NASA’s Lunar Reconnaissance Orbiter will carry a powerful modern camera into low orbit over the Moon’s surface. Its primary mission is not to photograph old Apollo landing sites, but it will photograph them, many times, providing the first recognizable images of Apollo relics since 1972.

The spacecraft’s high-resolution camera, called “LROC,” short for Lunar Reconnaissance Orbiter Camera, has a resolution of about half a meter. That means that a half-meter square on the Moon’s surface would fill a single pixel in its digital images.

Apollo moon buggies are about 2 meters wide and 3 meters long. So in the LROC images, those abandoned vehicles will fill about 4 by 6 pixels.

What does a half-meter resolution picture look like? This image of an airport on Earth has the same resolution as an LROC image. Moon buggy-sized objects (automobiles and luggage carts) are clear:

“I would say the rovers will look angular and distinct,” says Mark Robinson, research associate professor at Northwestern University in Evanston, Illinois, and Principal Investigator for LROC. “We might see some shading differences on top from seats, depending on the sun angle. Even the rovers’ tracks might be detectable in some instances.”

Even more recognizable will be the discarded lander platforms. Their main bodies are 4 meters on a side, and so will fill an 8 by 8 pixel square in the LROC images. The four legs jutting out from the platforms’ four corners span a diameter of 9 meters. So, from landing pad to landing pad, the landers will occupy about 18 pixels in LROC images, more than enough to trace their distinctive shapes.

Shadows help, too. Long black shadows cast across gray lunar terrain will reveal the shape of what cast them: the rovers and landers. “During the course of its year-long mission, LROC will image each landing site several times with the sunlight at different angles each time,” says Robinson. Comparing the different shadows produced would allow for a more accurate analysis of the shape of the objects.

Enough nostalgia. LROC’s main mission is about the future. According to NASA’s Vision for Space Exploration, astronauts are returning to the Moon no later than 2020. Lunar Reconnaissance Orbiter is a scout. It will sample the Moon’s radiation environment, search for patches of frozen water, make laser maps of lunar terrain and, using LROC, photograph the Moon’s entire surface. By the time astronauts return, they’ll know the best places to land and much of what awaits them.

Two high-priority targets for LROC are the Moon’s poles.

“We’re particularly interested in the poles as a potential location for a moon base,” Robinson explains. “There are some cratered regions near the poles that are in shadow year-round. These places might be cold enough to harbor permanent deposits of water ice. And nearby are high regions that are sunlit all year. With constant sunlight for warmth and solar power, and a potential source of water nearby, these high regions would make an ideal location for a base.” Data from LROC will help pinpoint the best ridge or plateau for setting up a lunar home.

Once a moonbase is established, what’s the danger of it being hit by a big meteorite? LROC will help answer that question.

“We can compare LROC images of the Apollo landing sites with Apollo-era photos,” says Robinson. The presence or absence of fresh craters will tell researchers something about the frequency of meteor strikes.

LROC will also be hunting for ancient hardened lava tubes. These are cave-like places, hinted at in some Apollo images, where astronauts could take shelter in case of an unexpected solar storm. A global map of these natural storm shelters will help astronauts plan their explorations.

No one knows what else LROC might find. The Moon has never been surveyed in such detail before. Surely new things await; old abandoned spaceships are just the beginning.

Original Source: NASA News Release

Posted on by Fraser Cain

Deep Impact’s Plume Was Bigger Than Expected

The huge plume of material shooting out of Comet Tempel 1. Image credit: NASA/JPL. Click to enlarge.
Data from Deep Impact’s instruments indicate an immense cloud of fine powdery material was released when the probe slammed into the nucleus of comet Tempel 1 at about 10 kilometers per second (6.3 miles per second or 23,000 miles per hour). The cloud indicated the comet is covered in the powdery stuff. The Deep Impact science team continues to wade through gigabytes of data collected during the July 4 encounter with the comet measuring 5-kilometers-wide by 11-kilometers-long (about 3-miles-wide by 7-miles-long).

“The major surprise was the opacity of the plume the impactor created and the light it gave off,” said Deep Impact Principal Investigator Dr. Michael A’Hearn of the University of Maryland, College Park. “That suggests the dust excavated from the comet’s surface was extremely fine, more like talcum powder than beach sand. And the surface is definitely not what most people think of when they think of comets — an ice cube.”

How can a comet hurtling through our solar system be made of a substance with less strength than snow or even talcum powder?

“You have to think of it in the context of its environment,” said Dr. Pete Schultz, Deep Impact scientist from Brown University, Providence, R.I. “This city-sized object is floating around in a vacuum. The only time it gets bothered is when the Sun cooks it a little or someone slams an 820-pound wakeup call at it at 23,000 miles per hour.”

The data review process is not overlooking a single frame of approximately 4,500 images from the spacecraft’s three imaging cameras taken during the encounter.

“We are looking at everything from the last moments of the impactor to the final look-back images taken hours later, and everything in between,” added A’Hearn. “Watching the last moments of the impactor’s life is remarkable. We can pick up such fine surface detail that objects that are only four meters in diameter can be made out. That is nearly a factor of 10 better than any previous comet mission.”

The final moments of the impactor’s life were important, because they set the stage for all subsequent scientific findings. Knowing the location and angle the impactor slammed into the comet’s surface is the best place to start. Engineers have established the impactor took two not unexpected coma particle hits prior to impact. The impacts slewed the spacecraft’s camera for a few moments before the attitude control system could get it back on track. The penetrator hit at an approximately 25 degree oblique angle relative to the comet’s surface. That’s when the fireworks began.

The fireball of vaporized impactor and comet material shot skyward. It expanded rapidly above the impact site at approximately 5 kilometers per second (3.1 miles per second). The crater was just beginning to form. Scientists are still analyzing the data to determine the exact size of the crater. Scientists say the crater was at the large end of original expectations, which was from 50 to 250 meters (165 to 820 feet) wide.

Expectations for Deep Impact’s flyby spacecraft were exceeded during its close brush with the comet. The craft is more than 3.5 million kilometers (2.2 million miles) from Tempel 1 and opening the distance at approximately 37,000 kilometers per hour (23,000 miles per hour). The flyby spacecraft is undergoing a thorough checkout, and all systems appear to be in excellent operating condition.

The Deep Impact mission was implemented to provide a glimpse beneath the surface of a comet, where material from the solar system’s formation remains relatively unchanged. Mission scientists hoped the project would answer basic questions about the formation of the solar system by providing an in-depth picture of the nature and composition of comets.

The University of Maryland is responsible for overall Deep Impact mission science, and project management is handled by JPL. The spacecraft was built for NASA by Ball Aerospace & Technologies Corporation, Boulder, Colo. JPL is a division of the California Institute of Technology, Pasadena, Calif.

Original Source: NASA News Release

Posted on by Fraser Cain

What’s Up This Week – July 11 – July 17, 2005

Star cluster Epsilon Scorpii (M6). Image credit: N.A. Sharp and Mark Hanna, REU Program/NOAO/AURA/NSF. Click to enlarge.
Monday, July 11 – For viewers in west Europe and northwest Africa, you will have the opportunity to watch the Moon occult 4th magnitude Sigma Leonis on this universal date. Please check the IOTA webpage for precise times in your location.

Tonight on the lunar surface, aim your binoculars or telescope towards the south shore of Mare Nectaris where we will examine ruined crater Fracastorius. To lower power, this will be a delicate, almost bay-like feature softly outlined in white. This is all that remains of a once-great crater as the lava flow from the mare filled it in. To its southern edge, the old walls still rise, but much of the north border is completely obliterated. If you examine it telescopically, you will see that the north has been reduced to a low series of ridges and craterlets, yet in binoculars it still gives the illusion of a complete ring.

As the Moon sets and the constellation of Scorpius rises higher, tonight would be an ideal time to look at a brilliant open cluster about a fist width east of Epsilon Scorpii – M6. On a moonless night, the 50 or so members of this 2000 light year distant, 100 million year old cluster can usually be seen unaided as a small fuzzy patch just above the Scorpion’s tail. Tonight we visit because the brighter skies will aid you in seeing the primary stars distinctive asterism. Using binoculars or telescope at lowest power, the outline of stars does truly resemble its namesake – the “Butterfly Cluster”. The M6 is much more than “just a pretty face” and we’ll be back to study under darker skies.

Tuesday, July 12 – Watch the quick progress of Mercury as it cruises beneath Venus over the next two nights starting about 45 minutes after sunset. Venus will be quite low at about half a fist width above the west/northwest horizon, and you will probably need binoculars to spot Mercury another 3 degrees lower. Be sure to note the position of Regulus, a little more than a fist width above and to the left of Venus.

With the anniversary of the Apollo 11 moon landing only eight days away, tonight will be our opportunity to look at the landing site on the lunar surface. To the unaided eye, look almost central on the lunar disc for the grey oval of Mare Tranquillitatus. Near the terminator you will note a brightness where the shore curves around the south edge to join Mare Nectaris. By aiming binoculars at this area, you can distinguish the bright peninsula just north of the three rings of Theophilus, Cyrillus and Catherina. To the telescope at mid-to-high power, note shallow rings of craters Sabine and Ritter to the northwest of this bright area. If you have a steady night on your hands – step up the power to maximum. East of Sabine and Ritter are three tiny craters in the otherwise smooth surface. From west to east they are Aldrin, Collins and Armstrong – the only craters on the Moon named for the living. Just south of Collins is the actual landing site and we salute the crew of Apollo 11 by viewing tonight just shy of 36 years since their adventure.

Wednesday, July 13 – Tonight lucky viewers for almost all of South America will have the chance to witness a spectacular occultation of Jupiter by the Moon. You can find precise times for your location on this IOTA webpage. Even if you do not use a telescope, I strongly urge you to at least watch this event! For viewers in New Zealand, you will have the opportunity to watch the Moon occult Eta Virginis. The precise times for a city near you are listed on this IOTA webpage.

For most of us, Jupiter and the Moon will make a very pleasing pair tonight. but let’s venture to a deep impact crater on the Moon. You will find Manilius telescopically just north of center along the terminator on the eastern shore Mare Vaporum. While it doesn’t appear to be much more than a singular “hole” on the lunar surface, Manilius is incredibly deep. Spanning around 39 km (25 miles), this crater drops down 3010 meters (9500 feet) below the Moon’s topography. That’s about 2/3 the distance that Titanic lay beneath the ocean!

Thursday, July 14 – Forty years ago today, Mariner 4 performed the first flyby of Mars. If you’re up before dawn this morning, be sure to look for the “Red Planet” as it cruises through Pices and heads toward the Sun.

Tonight the star accompanying the Moon on the right is Spica, but let’s explore the lunar surface in hopes of catching an unusual event. On the southern edge of the Mare Nubium is the old walled plain Pitatus. Power up. On the western edge you will see smaller and equally old Hesiodus, sharing a common wall. Almost central along this wall there is a break to watch when the terminator is close. For a brief moment, sunrise on the Moon will pass through this break creating a beam of light across the crater floor known as the Hesiodus Sunrise Ray. If the terminator has moved beyond it at your observing time, look to the south for small Hesiodus A. This is an example of an extremely rare double concentric crater. This formation is caused by an impact being followed by another, slightly smaller impact on exactly the same location.

Friday, July 15 – For our friends in Australia comes one incredible event… Tonight the Moon will occult Comet 9/P Tempel 1. For more information on this event, please visit the IOTA webpages for times and locations. We wish you the very best of skies!

For the rest of us, we’re stuck with the Moon, but this is a great chance to explore under-rated crater Bullialdus. Once again, we’re in the southern quadrant of the Moon near the terminator. Even binoculars can make out this crater with ease near the center of Mare Nubium. If you’re scoping – power up – this one is fun! Very similar to Copernicus, note Bullialdus’ thick, terraced walls and central peak. If you examine the area around it carefully, you can note it is a much newer crater than shallow Lubiniezsky to its north and almost non-existant Kies to the south. On Bullialdus southern flank, it’s easy to make out both its A and B craters, as well as the interesting little Koenig to the southwest.

Saturday, July 16 – Today in 1850 at Harvard University, the first photograph of a star was made (other than the Sun). The honors went to Vega! In 1994, an impact event was about to happen as nearly two dozen fragments of Comet Shoemaker-Levy 9 were speeding their way to the surface of Jupiter. The result was spectacular and the visible features left behind on the planet’s atmosphere were the finest ever recorded. Why not take the time to look a Jupiter again tonight while it still holds good sky position? No matter where you observe from, this constantly changing planet offers a wealth of things to look at – be it the appearance of the “Great Red Spot”, or just the ever changing waltz of the galiean moons.

Tonight no feature on the Moon will be more prominent that the Sinus Iridium, but if you have steady skies, why not power up to look a some of the finer features such as Bianchinni and Sharp on its borders? It the night is exceptionally steady, you may see up to a half dozen very small craters within the “bay” itself. Just outside in Mare Ibrium, even modest power can make out Helicon and Le Verrier. If the Dorsum Heim captures your imagination, look for tiny C. Herschel in its center.

Sunday, July 17 – Today in 1963, the Nuclear Test Ban Treaty is signed. This treaty prohibits the detonation of nuclear devices in our atmosphere. To be sure all countries were in compliance, the United States afterward launched the first gamma ray detectors into orbit. In 1967 these detectors picked up a new discovery – the first of many cosmic gamma ray sources.

Observers located along a path that includes Mexico, Central America, northern South America, and the extreme southern and western U.S. have the opportunity to witness the occultation of Antares tonight, while most of the U.S. will see the Moon graze just south. For times of the event at selected cities, see this page or Dr. David Dunham’s personal webpages which includes graze information. For central South America viewers and lower California, you will also be treated to the occulation of Sigma Scorpii on the universal date. Check IOTA wepages for more details. Clear skies!

If you chose to view the lunar surface, be sure to look for crater Schiller near the terminator on the southern cusp. Its long oval form is a real treat.

Yes, the Moon is back, but I’ll do my best to find more great events to enjoy! May all your journeys be at Light Speed… ~Tammy Plotner