Astronomy Picture of the Day
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2004 January 17 
Posted on 01/16/2004 10:12:27 PM PST by petuniasevan
Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2004 January 17
Explanation: Born in 1564, Galileo used a telescope to explore the Solar System. In 1610, he became the first to be amazed by Saturn's rings, After nearly 400 years, Saturn's magnificent rings still offer one of the most stunning astronomical sights. Uniquely bright compared to the rings of the other gas giants, Saturn's ring system is around 250,000 kilometers wide but in places only a few tens of meters thick. Modern astronomers believe the rings are perhaps only a hundred million years young. Accumulating dust and dynamically interacting with Saturn's moons, the rings may eventually darken and sag toward the gas giant, losing their lustre over the next few hundred million years. Since Galileo, astronomers have subjected the entrancing rings to intense scrutiny to unlock their secrets. On December 31, 2003, Saturn made its closest approach to Earth for the next 29 years, a mere 1,200,000,000 kilometers. It will remain a tantalizing target for earthbound telescopes in the coming months.
| Saturn Statistics | |
|---|---|
| Mass (kg) | 5.688e+26 |
| Mass (Earth = 1) | 9.5181e+01 |
| Equatorial radius (km) | 60,268 |
| Equatorial radius (Earth = 1) | 9.4494e+00 |
| Mean density (gm/cm^3) | 0.69 |
| Mean distance from the Sun (km) | 1,429,400,000 |
| Mean distance from the Sun (Earth = 1) | 9.5388 |
| Rotational period (hours) | 10.233 |
| Orbital period (years) | 29.458 |
| Mean orbital velocity (km/sec) | 9.67 |
| Orbital eccentricity | 0.0560 |
| Tilt of axis (degrees) | 25.33 |
| Orbital inclination (degrees) | 2.488 |
| Equatorial surface gravity (m/sec^2) | 9.05 |
| Equatorial escape velocity (km/sec) | 35.49 |
| Visual geometric albedo | 0.47 |
| Magnitude (Vo) | 0.67 |
| Mean cloud temperature | -125°C |
| Atmospheric pressure (bars) | 1.4 |
Atmospheric composition
|
97% 3% |
It seems that there's even more going on with the star Betelgeuse than we imagined! Keep an eye on this mess of a supergiant star. It's easy to find; it's the bright orange-red star in the shoulder of Orion.
Hot and cold gas rage in Betelgeuse's atmosphere
HARVARD-SMITHSONIAN CENTER FOR ASTROPHYSICS NEWS RELEASE
Posted: January 15, 2004
A team of astronomers, led by Alex Lobel of the Harvard-Smithsonian Center for Astrophysics (CfA), announced at the 203rd meeting of the American Astronomical Society in Atlanta that Hubble Space Telescope observations of a nearby supergiant star directly show hot gas escaping its boiling atmosphere at a larger distance than from any other star. The expelled hot gas somehow survives the cold and harsh conditions in the star's bloated upper atmosphere.
 New observations of Betelgeuse with the Hubble Space Telescope show that warm gas from the Betelgeuse supergiant's upper chromosphere is present inside its cold and dusty outer gas envelope. In this artist's impression of the upper chromosphere, shock waves from the star's huge pulsating surface traverse the chromosphere (shown in violet and blue colors) and enter into the cooler dust envelope (in orange and black). The waves produce the warm gas which mixes with the cold gas. Credit: Alex Lobel, Harvard-Smithsonian Center for Astrophysics. |
STIS detected the spectral signatures of tenuous hot gas in cold, remote, and dusty places of Betelgeuse's mammoth atmosphere. The observations help to determine the mechanisms that form and sustain warm gaseous envelopes in many other red and yellow stars, including the Sun.
The team investigated the atmosphere of Betelgeuse, the brightest star in the constellation Orion, over the past five years with the STIS instrument aboard Hubble. They found that the bubbling action of the chromosphere tosses gas out one side of the star, while it falls inward at the other side, similar to the slow-motion churning of a lava lamp.
"Betelgeuse's upper chromosphere extends into the enormous cloud of cold dust around this supergiant star. Our basic knowledge of how chromospheres form should explain how it sends this warm gas so far into space. There is plenty of gas below 2000 degrees Fahrenheit because of dust, but this gas is apparently joined by much hotter ionized gas from the chromosphere near the star's surface" said Lobel.
Before the discovery, telescopes on Earth detected the warm gas in the star's weak chromosphere up to only about five times the star's radius, a size bigger than Saturn's orbit. (The photospheric surface of Betelgeuse is about as large as Jupiter's orbit.)
When a match flame warms the air above it, the heat quickly disperses into the cooler surrounding air. In Betelgeuse's upper atmosphere, hot and cold gas mix together, but the warm gas does not entirely dissipate away until far above the heights where much colder gas is observed.
The new STIS spectra in ultraviolet light show that very remote parts of the chromosphere contain hot gas above 4220 degrees Fahrenheit (2600 Kelvin). The cold neighboring gas, however, is not warmer than 2240 degrees F (1500 K). Higher temperatures would destroy the dust particles that glow in infrared light at a large distance from the supergiant.
Running shock waves
The astronomers considered several explanations for the joint presence of hot and cold gas in the upper chromosphere of this gargantuan star. One explanation calls for long trains of shock waves which run through the chromosphere. The front of a shock wave compresses the gas and heats it up. It chills in the expanding wake of the passing wave. The shocks are strong enough to warm up a large volume of gas far above the supergiant's surface. The temperature in their long wakes, however, decreases so rapidly that dust grains can form without being completely destroyed by following waves.
The new observations also show that the outflow of warm gas accelerates with larger distance in the upper chromosphere and dust shell. "This further supports the shock wave model," said Lobel. "If the atmosphere were static, the observed temperature differences would disappear with the natural exchange of heat."
Warm material moves far above the surface of Betelgeuse in a dynamic balance of heat with colder gas inside its dust cloud. When large volumes of warm and cold air collide in Earth's atmosphere, devastating tropical storms can form with wind powers that lift up cars. Similarly, the chromosphere of Betelgeuse is very turbulent. The STIS spectra show that the speed of the turbulence is faster than the local sound velocity. This supersonic turbulence could result from running shocks or from the flow of energy between the newly discovered warm and cold gas.
Pulsations of the chromosphere
Other models without shock waves consider oscillations of the chromosphere. Parts of the star's unstable surface sometimes vigorously bulge out in different directions, piercing long warm plumes into the cold dust envelope. At large distances from the surface, the density of the cold atmosphere strongly decreases, which prevents it from absorbing the heat carried by the intruding warmer plumes. These plumes cool off only far beyond the regions observed by STIS, where the density decreases to levels similar to the cold gas, like a plume of steam cools higher above the nozzle of a boiling kettle.
The team plans to request new high-precision observations to find out if the chromospheres of other nearby supergiants also extend so far into space. "We would like additional observations to confirm the presence of warm gas at distances as great as fifty stellar radii," said team member Jason Aufdenberg, a former research fellow at CfA, now at the National Optical Astronomy Observatory.
The search for the reasons why chromospheres are produced around stars started decades ago with pioneering observations of the faint chromosphere of the Sun, which extends only a few percent of the radius above the surface. One out of million stars in our Galaxy is a supergiant like Betelgeuse, which even at a distance of 425 light-years is the seventh brightest star visible in the northern hemisphere. The new observations of its puffed-up chromosphere with the Hubble Space Telescope bring scientists an important step closer to completing that search.
The team presented parts of the research in this release at a meeting of the International Astronomical Union of last July.
This research was supported by NASA and the Smithsonian Astrophysical Observatory. The science team mentioned in this press release consists of Drs. Alex Lobel, Andrea Dupree, Robert Kurucz, Robert Stefanik, Guillermo Torres (all at the Harvard-Smithsonian Center for Astrophysics, Mass.), and Jason Aufdenberg (National Optical Astronomy Observatory, Arizona).
Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.
Spirit's robot arm extended for detailed study of soil
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: January 16, 2004
The Spirit Mars rover unlimbered its robot arm today and took the first microscopic images of another planet's surface. The smooth operation of the arm during the rover's 13th day on Mars was another major milestone in a mission that, so far, has sailed through activation and checkout without any significant problems.
 Onboard camera view of the science arm after its deployment Friday. Credit: NASA/JPL |
As if that wasn't enough, Spirit made a series of observations in concert with a European satellite that arrived at Mars on Christmas day.
"We had the first coordinated international observations at Mars where the Spirit rover looked up and the European Space Agency's Mars Express orbiter looked down through the same atmosphere at the same time," Adler said. "We also had a checkout of our rock abrasion tool, and it checked out great."
Spirit rolled off its lander Thursday morning and parked about a foot away. Before the robot begins moving across the martian surface, scientists want to check out its instrument deployment device, or IDD - the rover's robot arm - and test the operation of its instruments. A rotating turret on the end of the arm carries two spectrometers, a microscopic imager and a rotating rock abrasion took, or RAT, that will be used later to burr into selected rocks, exposing pristine materials not affected by weathering.
 Spirit's arm moves into action for soil studies. Credit: NASA/JPL |
"But best of all, this robotic arm sits on a rover. And as we've said, a rover is made to rove. And so the rover will take this arm and this tremendous science package along with it and every time we stop, we'll take a look at a rock or a piece of soil as we traverse across Gusev Crater. We have the ability to collect in situ science, science from the surface of Mars up close and personal and reach out an investigate that surface."
Baumgartner said he was happy to report that "the instrument deployment activities that went on today were very successful."
Ken Herkenhoff, science lead for the microscopic imager, said things went so smoothly "I'm a little tongue tied. It's hard for me to describe all the emotions I'm feeling right now. I'm elated and relieved at how well things are going. As I'll show you, we've got some nice images from our first day on Mars with the microscopic imager."
The microscope is capable of resolving features as small as a human hair or a grain of table salt. Test images taken earlier today were at "the highest resolution by far we've ever seen at Mars," he said.
 This close-up look at a patch of martian soil by Spirit's microscopic imager is the sharpest image ever taken of another planet. Credit: NASA/JPL/US Geological Survey See a larger version here |
Saturday night, the arm will be stowed for a 15-minute calibration of the APXS. Other IDD observations will be scheduled based on realtime planning while the rover's cameras continue the ongoing characterization of the landing site.
"We're going to have a big science weekend coming up, putting more instruments down on the soil," said project scientist Joy Crisp.
The Opportunity rover, meanwhile, continues to close in on Mars for a planned landing next Saturday night. On Friday, a trajectory correction maneuver was successfully carried out to precisely aim the spacecraft at a landing zone on the other side of Mars.
"Looks like we got a nice burn out of Opportunity," Jim Erickson, the mission manager said in a statement. "We're on target for our date on the plains of Meridiani next Saturday with a healthy spacecraft."
One thing they don't mention in this next article is that MOST of HST's technology has been surpassed by Earth-based telescopes using such innovations as flexible, computer-controlled image correcting mirrors. Choices have to be made, and though I don't like the cancellation, I understand it. Why not cancel the shuttle missions to ISS too, though? It's a white elephant.
NASA cancels final Hubble telescope servicing mission
BY WILLIAM HARWOOD
STORY WRITTEN FOR CBS NEWS "SPACE PLACE" & USED WITH PERMISSION
Posted: January 16, 2004 at 5:15 p.m. EST; Updated at 7 p.m. with news conference details
A final planned shuttle mission to service and upgrade the Hubble Space Telescope, one of the most scientifically productive spacecraft ever launched, has been cancelled, primarily because of post-Columbia safety concerns and a new directive to retire the shuttle by 2010, NASA officials said today.
 Credit: NASA |
The decision means an advanced camera and light-splitting spectrograph - both already built - will not be installed. It also leaves Hubble's continued operation at the mercy of its aging gyroscopes, batteries and other equipment.
Based on the past performance of the gyros and other gear, engineers believe the observatory has a 50-50 chance of remaining in operation until mid 2007, three years shy of when NASA had earlier planned to retire the observatory.
Hubble's replacement, the James Webb Space Telescope, will not be launched until around 2011 at the earliest. Foregoing the final servicing mission means the gap between Hubble and Webb will stretch years longer than scientists had hoped.
"We're going to try to get as much life as we can out of the Hubble Space Telecope," Grunsfeld said. "We have a commitment from the office of space science that we will continue to support the research and analysis work even beyond (Hubble's demise)."
NASA Administrator O'Keefe told engineers and scientists at NASA's Goddard Spaceflight Center that his decision was based on a variety of factors, including a recommendation by the Columbia Accident Investigation Board that would require an autonomous tile repair capability for flights not bound for the international space station.
Hubble Servicing Mission 4, or SM-4, was the final flight on NASA's launch manifest that wasn't bound for the space station, where the crew of a crippled shuttle could attempt repairs or await rescue. The CAIB recommendation would have required NASA to develop stand-alone repair techniques for a single flight.
Grunsfeld said the cost of that effort, coupled with the Bush administration's recent directive to complete space station assembly and retire the shuttle fleet by 2010, left little choice.
"The president laid out for us a plan for space exploration," Grunsfeld said. "As part of that, he directed us to use this precious resource, the space shuttle, with a priority of completing the international space station and then retiring the shuttle.
"And so as part of that, when you look at what it would take to support this one single-use unique mission ... in light of retiring the shuttle, kind of pushed the decision over the edge and allowed the administrator to make that decision. As a result, this decision is reflected in the president's budget, which will come out on Feb. 2."
Hubble supporters were devastated.
"People here are brushing off their resumes," said one official at the Space Telescope Science Institute at Johns Hopkins University in Baltimore. "Hubble has been such a crown jewel for NASA, I would have hoped it would have tilted the balance the other way. ... It's been a sad day. It was like walking around a funeral home."
Before the Columbia disaster, NASA had planned to launch a final servicing mission to install the Cosmic Origins Spectrograph and a new, third-generation Wide Field Camera. Spacewalking astronauts also planned to replace stabilizing gyroscopes, aging batteries and other equipment in a bid to keep Hubble healthy until 2010 or so.
Only four of the telescope's six gyroscopes are operational and at least three are needed to continue scientific operations. Engineers hope to develop software that will allow the observatory to function with two gyros, but that work is not yet complete.
How long Hubble might continue to operate without another servicing mission is anybody's guess.
"The answer to how long it can last is completely probabilistic," said a project scientist who asked not to be named. "Who knows what will fail first? The two things we have always been most concerned with are the gyros and the batteries, both of which SM-4 would have addressed."
Based on the past performance of the gyroscopes, "it's our guess we have two years to go with 50 percent probability before we're down to two gyros," he said. "But it could be tomorrow and it could be eight years (from now).
"We need three gyros to do business as usual. We believe we can develop software to operate with two gyros and do 70 percent of the science the community would like to do. And indeed, headquarters had committed itself to asking Goddard and the institute to develop two-gyro mode several months ago. So clearly, we will do that."
That effort probably would keep Hubble operational into the mid 2007 time frame, but there are no guarantees. Batteries are another potential issue.
"The batteries are the original batteries, they are way past their experience baseline now," the astronomer said. "They are showing teeny little idiosyncratic signs of aging that no one really knows how to interpret. That's another wild card. And then, of course, you can name other things that could interrupt operations."
Up in the air is the fate of the Space Telescope Science Institute and the costly instruments already built for SM-4.
"The Cosmic Origins Spectrograph and the Wide Field 3 are almost complete and they are both fantastic instruments. We're really going to scratch our heads and find a good way to get the science out of those," Grunsfeld said.
"The various options that we are looking at, nothing definitive, but one possibility is that we find a way to incorporate the opportunity for those instruments to fly in ... our medium-class Explorer missions," he said.
"For instance the Origins Spectrograph could be combined with a relatively small mirror -- a one- or a one-and-a-half-meter mirror -- and still do the high-priority science."
michael miserable failure moore hillary evil bitch clinton al sore loser gore bill lying rapist clinton
It's a damn shame about the Hubble. What a waste.
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