God Bless America

Mar. 28 2000

* From NASA: 
  +Compton Gamma-Ray Observatory 
  +Space Weather News Molecular Buckyballs
* From Space Weather:
  + Solar Flare Erupted Near the Center of the Sun's Disk
* From Space & Flight 
  + Hunt For Earth-Like Planets Begins 
* From Spaceviews
  + Astronomers Discover "Free-Floating" Planets

** The Compton Gamma-ray Observatory is destined for a watery grave in the remote Pacific on June 3, 2000. At a press conference March 24, NASA officials cited human safety concerns in explaining their decision to de-orbit the satellite, which has revolutionized our understanding of the cosmos during a highly successful 9 year mission. 

FULL STORY at:
http://spacescience.com/headlines/y2000/ast25mar_1m.htm 

** Scientists have discovered molecular buckyballs containing extraterrestrial helium from the era of the dinosaurs. The find comes from the global Cretaceous/Tertiary boundary layer. FULL STORY at

http://spacescience.com/headlines/y2000/ast21mar_1.htm 

** On March 25, 2000, a solar flare erupted near the center of the Sun's disk. It appears that a coronal mass ejection was launched toward Earth. An interplanetary shock wave could pass our planet during the next 24 to 48 hours, triggering moderate geomagnetic activity and aurorae. 

For more information and daily updates please visit:
 http://www.spaceweather.com 

** Hunt For Earth-Like Planets Begins (Space.com)

NASA's Jet Propulsion Laboratory (JPL) announced Tuesday it has awarded its first contracts to begin design work on a highflying quartet of telescope-equipped satellites that will seek out other Earth-like worlds. The innovative Terrestrial Planet Finder mission, still more than a decade away from launch, will hunt for worlds like ours orbiting stars within a range of about 50 light-years, studying their numbers, size, location, diversity and suitability for life. The mission's initial design calls for four free-flying satellites, each carrying its own 137-inch (3.5-meter) infrared telescope in an Earth-trailing solar orbit. The light gathered by each telescope would be combined in a fifth satellite, which would also hold the mission's instrumentation. (NASA intends to test the concept in 2003 with the launch of Space Technology 3, made up of just two free-flying space telescopes that will fly and work in unison.) The awards announced Tuesday went to Ball Aerospace, Lockheed Martin Space Systems, TRW and SVS Inc. The individual teams represent 75 scientists drawn from nearly 50 universities, industrial firms, research institutions and NASA centers. "We've succeeded in our goal of engaging some of the best minds in the world," said Firouz Naderi, the mission's project manager at JPL, of the teams that will further refine various concepts for Planet Finder. By December, NASA will narrow the field to two teams, which will then be subjected to further study ending in November 2001. The actual mission will not launch before 2012. At the onset, the mission will examine some 250 stars already spotted by an earlier effort -- the Space Interferometry Mission set for launch in 2006 -- which will hopefully characterize any planets in orbit around them. Once its cataloging work is complete, Planet Finder will then zero in on those stars that are most likely to hold habitable planets in an orbital embrace, searching for the telltale traces of life. Through the technique of spectroscopy - analyzing the spectrum of light reflected by the planets to see which elements are present -- the mission will tell scientists the relative proportions of gases such as carbon dioxide, water, ozone and methane at each of those planets. These elements can strongly suggest the presence of life. "We'll be looking for warm, water-bearing planets like Earth, and even for signs of primitive life," said Charles Beichman, the mission's project scientist at JPL. Scientists boast that the mission could, with as little as two weeks of observations, tell whether any particular planet harbors primitive life. The mission itself could last as long as five years. To accomplish its task, the Planet Finder will wed the incredible sensitivity of spaceborne telescopes -- like the Hubble Space Telescope, but perhaps 100 times sharper -- with the high spatial resolution of an interferometer. In interferometry, light gathered by separate telescopes is combined to form one image. However, the image's resolution equals that produced by a telescope equipped with a single mirror as wide as the distance between the individual mirrors. In the case of the Terrestrial Planet Finder, the satellites will fly as far 0.6 miles (1 kilometer) apart. The Planet Finder will take the "Goldilocks" approach in its search for habitable planets, using its four telescopes to focus on those bodies that are "just right" for life. That means the candidate planets must lie in a zone where temperatures allow for presence of liquid water, presumed to be necessary even for life beyond our planet. To spot such small, relatively cool bodies, the Planet Finder will rely on a technique called "nulling" to block the bright glare of a planet's parent star, allowing the dim planets to appear. Since 1995, astronomers have discovered more than 30 planets orbiting stars other than our own. However, those planets have all been Jupiter-sized or larger, and far too close to their respective stars to be able to support life.

** Astronomers Discover "Free-Floating" Planets

British astronomers reported last week that they have discovered more than a dozen "free-floating" planets not orbiting any stars in a nebula.

The 13 planets, weighing between eight and 13 times the mass of Jupiter, plus over 100 brown dwarfs, were discovered in the Orion Nebula by British astronomers Philip Lucas and Patrick Roche using a new camera mounted on the United Kingdom Infrared Telescope (UKIRT) atop Mauna Kea, Hawaii.

The discovery of these planets is expected to provide new insights into the formation of stars in nebulae like Orion, although, ironically, their existence may have little to do with the formation of solar systems.

The upper limit on the mass of the planets is based on the definition of the minimum mass of a brown dwarf, a class of "failed" stars not massive enough to sustain nuclear fusion for an extended period. At 13 Jupiter masses an object can sustain nuclear fusion for only a short period, and is thus considered the minimum mass for a brown dwarf.

The lower limit on the mass of the discovered planets is more interesting. The eight-Jupiter mass limit may indicate a minimum size for such free-floating planets, or just the limits of the sensitivity of the UKIRT camera. Additional, more sensitive, surveys would have to be conducted to verify this.

The free-floating planets likely formed from isolated clumps of material within the nebula, Roche told SpaceViews, and not from the debris left over from the formation of a star, as were the planets in our solar system and others. Thus the discovery of these "planets" provides little new information about the creation of solar systems.

Although the planets formed differently than those in our solar system, they are likely physically similar to larger versions of the gas giant planets in our solar system. Spectroscopic studies of some of the planets have turned up the existence of water vapor at temperatures of around 2,700 degrees Celsius (4,900 degrees Fahrenheit). The planets will eventually cool down to Earth-like temperatures, but are unlikely to ever be able to support life.

The discovery of the planets and brown dwarfs do indicate that such bodies may be commonplace in nebulae, although they are neither numerous nor massive enough to account for the "dark matter" believed to compose 90 percent of the mass of the universe.

The results of Lucas and Roche's work will be published in a future issue of the Monthly Notices of the Royal Astronomical Society.

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Submitted by
CMDR Constance Sanders
USS Yorktown
Chief, Space Activities Committee, SFC
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