Skip to comments.Astronomy Picture of the Day 01-19-04
Posted on 01/18/2004 9:41:08 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 19
Explanation: Flying past a comet nucleus is dangerous. On January 2, the robot spacecraft STARDUST became one of the first to plow through the surrounding cloud of dust and grit to photograph the very heart of a comet. Pictured above is a short movie of the encounter showing unprecedented surface details of the icy center of Comet Wild 2. The STARDUST camera pivoted to remain pointed at the nucleus as the spacecraft passed. Heavily shielded from the onslaught of cometary debris, STARDUST survived the beating in excellent condition. Surprisingly, although the nucleus appeared to be solid, the the surrounding coma appeared to be highly fragmented into several distinct streams of particles. Souvenirs captured by the spacecraft will be ejected as the spacecraft passes the Earth in January 2006.
Building a new West Coast era for Atlas rockets
BY JUSTIN RAY
Posted: January 18, 2004
Work has begun at California's Vandenberg Air Force Base to construct a launch pad for Lockheed Martin's Atlas 5 rocket, allowing the booster to compete with rival Boeing's Delta 4 on the West Coast and providing the U.S. government a second pathway to space for critical national security satellites.
Officials hold a ground-breaking ceremony at Space Launch Complex 3-East on January 14. Credit: Lockheed Martin
Boeing had the Pentagon's West Coast launch business all sown up after Lockheed Martin opted against a Vandenberg pad several years ago, citing a relatively low number of payloads. But that changed last July when military officials penalized Boeing for possessing Lockheed Martin propriety documents, stripping several launches from the Delta 4 manifest and giving them to Atlas 5.
Before the EELV program revolution last summer, Lockheed Martin's satellite-launching future at Vandenberg appeared bleak with the Titan rockets being phased out and just one older-model Atlas 2AS booster left to fly.
The fiery ignition at the Space Launch Complex 3-East pad of the Atlas 2AS rocket on December 2. Credit: Lockheed Martin
"Originally, the launch we had from Vandenberg on the 2nd of December was going to be the last Atlas launch from Vandenberg. We have history here of Atlas launches dating back to 1959. It just didn't seem right that was going to be the end of the era. And fortunately it's not the end of the era. It's just closing one chapter and starting a very important new one," Jim Sponnick, Lockheed Martin's Atlas program vice president, told reporters at a news conference last week.
The Atlas program has launched 284 rockets from 15 different locations at Vandenberg over the past 44 years, Sponnick said.
Engineers are taking the existing Atlas 2AS pad, called Space Launch Complex 3-East, and giving it a major overhaul to support the larger, more powerful Atlas 5 family of rockets. The $200 million project will retrofit the existing mobile service and umbilical towers at the pad while adding a fixed launch platform and enlarging the flame trench.
This illustration shows the changes being made to SLC-3E to support Atlas 5. Credit: Lockheed Martin
GRAPHICS DETAILING THE MODIFICATIONS:
OVERVIEW OF THE CHANGES BEING MADE
MORE DETAIL ON LAUNCH TOWER AND PLATFORM
CHANGES TO THE MOBILE SERVICE TOWER
OVERHAUL TO THE FLAME TRENCH
THE GROUND COMPUTER SYSTEM
ATLAS 5 PROCESSING FLOW AT VAFB
PERFORMANCE FOR VAFB ATLAS 5 VERSIONS
Lockheed Martin hopes to move swiftly through the project -- removal of obsolete parts and construction of the new hardware should be completed by year's end. The first rocket will arrive on the pad in December to begin five months of testing before the site is declared "ready" in May 2005. The inaugural flight carrying another NRO spy satellite payload is scheduled for October 2005.
"This is clearly an aggressive modification schedule," Sponnick acknowledged. "But we think we have a plan that fully supports."
"The Atlas 5 program has evolved over the last several years. For many years we never thought we were going to fly off this coast. Today, we have the opportunity to demonstrate not only that we can but we have a plan that we are ready to do that," added Lt. Col. Bob Hodgkiss, the Atlas 5 program manager in the Air Force's EELV Systems Program Office.
"We look forward to the challenge. We believe that we will provide increased capability for the nation, improving our assured access to space."
The overhauled pad aims to serve an annual launch rate of four missions with approximately three months needed to assemble and ready each rocket, Sponnick said. Unlike the Atlas 5 launch site at Cape Canaveral that prepares the rockets in the Vertical Integration Facility and then rolls the boosters to the pad just hours before liftoff, Vandenberg will use the traditional on-pad processing scheme.
Of the five West Coast launches awarded to Atlas 5, four of them will deploy classified reconnaissance spacecraft for the NRO -- the government agency responsible for designing and operating the country's fleet of spy satellites. The fifth launch carries an Air Force weather satellite.
Lt. Col. Jim Norman, the NRO's Office of Space Launch deputy director, called last week's ceremonial ground-breaking for the Space Launch Complex 3-East renovations as a "key day."
"The NRO's mission is freedom's sentinel in space. We try to provide information and data to our nation's analysts, our leaders and our troops in the field. We see this as part of that link, frankly, on being able to support that mission directly."
The Atlas 5 400, 500 and Heavy vehicle configurations are shown in this illustration. Credit: Lockheed Martin
There are no current plans to fly the giant Atlas 5-Heavy rocket from the West Coast. That vehicle is under development for launches from the Cape beginning in late 2006.
"We have carefully scrutinized the potential mission manifest here from Vandenberg for at least the next 10 years and we do not foresee any needs for the heavy-lift version of the Atlas 5 vehicle from Vandenberg," Sponnick said. "The Atlas 5 with up to five solid rocket boosters provides a very substantial performance capability here from Vandenberg."
Hodgkiss says one of the five scheduled Vandenberg launches will be a 500-series vehicle that is distinguished with the much larger five-meter diameter nose cone; the rest are 400-series rockets with four-meter fairings.
Boeing currently has three West Coast Delta 4 missions -- two for the NRO and one weather satellite deployment mission.
With both EELV rockets available to place satellites into orbits around Earth's poles from California, something not practical from Cape Canaveral, the U.S. military will avoid relying upon just one rocket.
"It's great to see the heritage of the Atlas program continuing its legacy here at Vandenberg," Col. John Insprucker, director of the Air Force EELV Systems Program Office, said in a written statement. "It's another arrow in our quiver as a means of preserving our nation's asymmetric advantage in space."
A failed star is born
UNIVERSITY OF MICHIGAN NEWS RELEASE
Posted: January 15, 2004
In cosmic circles, brown dwarfs are something of a flop. Too big to be considered true planets, yet not massive enough to be stars, these free-floating celestial bodies are, in fact, sometimes referred to as failed stars. But do they really form as stars do -- from collapsing clouds of gas -- or are their origins completely different?
A series of publications by University of Michigan astronomer Ray Jayawardhana and collaborators, including a paper in the Jan. 16 issue of Science, offers evidence that brown dwarfs and Sun-like stars are born in much the same way. "They at least have very similar infancies, which may mean that they also have very similar origins," said Jayawardhana, assistant professor of astronomy.
Brown dwarfs in a star-forming region in the constellation Chamaeleon.
But other scientists have proposed that brown dwarfs are runts kicked out of stellar litters. In this scenario, brown dwarfs are born in multiple star systems and compete with their siblings for matter from the natal cloud. In such systems, the slowest-growing object may be ejected before it gathers enough material to become a star, computer simulations suggest. One way to distinguish between the two possibilities is by studying disks of dust and gas around young brown dwarfs. If brown dwarfs form as stars do, they should have large, long-lived accretion disks like those found around young stars. But if they have been ejected from multiple star systems, their disks should be shaved down by the gravitational interactions that lead to ejection.
Jayawardhana and colleagues searched for dusty disks around young brown dwarfs by observing their infrared emission with the 8-meter Very Large Telescope (VLT) of the European Southern Observatory in Chile and the 10-meter Keck I telescope in Hawaii. Because dust particles in a disk absorb light and re-radiate the energy at infrared wavelengths, a brown dwarf with a disk will emit more infrared light than one without a disk.
"We found that the majority of brown dwarfs are surrounded by dusty disks at an age of a million years or so," said Jayawardhana. "That's similar to young stars at the same age." Although it's not possible to directly determine the disks' sizes, their presence around some brown dwarfs as old as 10 million years suggests that they aren't pared away in early life.
Other spectroscopic observations, using the twin 6.5-meter Magellan telescopes in Chile (in which the University of Michigan is a partner institution) and the Keck I telescope, showed that brown dwarfs also accrete material from surrounding disks the same way as stars do -- although at a slower pace.
"We detect telltale signs of gas flowing from the inner edge of the disk onto the brown dwarf at velocities of over a hundred kilometers per second," said Jayawardhana. In one intriguing case, astronomers have also found evidence of material spewing out from the poles of a brown dwarf. Such jets have been seen in young stars of the same age, but not until now in brown dwarfs. "If confirmed, the presence of jets would further strengthen the case for remarkably similar infancies for brown dwarfs and Sun-like stars," said Jayawardhana, whose collaborators include Subhanjoy Mohanty (Harvard-Smithsonian Center for Astrophysics), Gibor Basri (University of California, Berkeley), David Barrado y Navascues (Laboratory of Space Astrophysics and Fundamental Physics in Madrid, Spain), David Ardila (Johns Hopkins University), Beate Stelzer (Astronomical Observatory of Palermo in Italy), and Karl Haisch, Jr. and Diane Paulson (both at the University of Michigan).
"I wouldn't say that the story is signed, sealed and delivered," Jayawardhana said, "but the preponderance of evidence is very much leaning in the direction of these things forming the same way as stars." And the evidence uncovered so far leads to even more tantalizing prospects. "Now that we know many young brown dwarfs are surrounded by disks," he said, "I can't help but wonder if comets and asteroids -- if not small planets -- could form in these disks."
This research was supported primarily by a grant from the National Science Foundation.
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