And
Posted on 09/27/2003 7:19:20 AM PDT by KevinDavis
The question of whether we're alone in the universe just got a lot bigger.
Two astronomers from the University of New South Wales, Australia - Dr Charles Lineweaver and Daniel Grether - have found that at least 25 per cent of Sun-like stars have planets.
"This means there are at least 100 billion stars with planets in our Galaxy," says Dr Lineweaver, a Senior Research Fellow at the University's School of Physics.
Until now, astronomers believed that only five to 15 per cent of Sun-like stars had orbiting planets, but Lineweaver and Grether's work shows that previous estimates under-reported the proportion of so-called extrasolar planets.
The Astrophysical Journal, the world's leading journal of astrophysics, has accepted their research for publication.
Astronomers have been carefully monitoring 2,000 nearby stars for the presence of orbiting extrasolar planets.
"To date, they've detected a hundred or so, meaning the fraction of stars with extrasolar planets was around five per cent," says Dr Lineweaver.
"But most planets are too small or take too long to orbit their host stars to be detected. For example, if the Sun were one of the stars being monitored, we still wouldn't have detected any planets around it.
"Using a new method to correct for this incompleteness, we found that at least 25 per cent of Sun-like stars have planets."
Dr Lineweaver believes that the figure of at least 100 billion stars with orbiting planets could be on the low side when it comes to cosmic counting. It could be that close to 100 per cent of stars have planets.
"Given that there are about 400 billion stars in our Galaxy alone, it means there could be up to 400 billion stars with planets," he says.
"With about 100 billion galaxies in the observable universe, our result suggests that there are at least 10 trillion planetary systems in the Universe."
'What Fraction of Sun-like Stars have Planets?' by Charles H Lineweaver and Daniel Grether will be published later this year. It is available online.
Dr Lineweaver is an ARC Senior Research Fellow and Senior Lecturer, School of Physics, UNSW. Daniel Grether is working on a PhD.
And how could they even tell when they're simply tracking transits? Can a transit tell you anything more than possibly the size of the planet? Heck, it can barely tell you that as you don't know how far the planet is from the star in the first place. Nor how fast its orbit is. Conjecture, suppositions, etc.
And
Billlllions and billllions
As for a Sol-like solar system: consider that Jupiter "eats" a lot of comets, asteroids, and assorted space debris. Without a Jupiter, that Earthlike planet is likely to resemble Mercury.
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Darwin mission The European Space Agency has targeted the InfraRed Space Interferometer-Darwin for a launch in 2015 or later. Decisions about whether to go forward with the mission are expected around 2003.
The telescope, using infrared rather than optical wavelengths, would hunt for Earth-like planets around some 300 Sun-like stars within 50 light-years of Earth. Darwin would actually be an array of six small eyes, forming an effective giant that would mimic a 100-yard (91-meter) telescope.
Scientists are still studying how such a system might be designed.
Unlike current space-based telescopes, Darwin would operate somewhere between Mars and Jupiter, rather than in Earth orbit. This would allow the instruments to avoid the dust between Earth and Mars that obscures the view.
The six individual telescopes would be joined either by long arms or would each be mounted on individual spacecraft. In the former case, the rigid structure would rotate to build up the image. In the latter case, the individual spacecraft would have their own rocket motors and dance around each other to build up the image.
Eddington mission
The Eddington mission was proposed to the European Space Agency (ESA) in early 2000. It would search for and study potentially habitable planets around other stars using a 1.2-meter (47-inch) optical telescope.
Eddington would carry an optical photometer mounted on a three-axis stabilized platform, sitting far from Earth.
The mission would also study the makeup and evolution of stars.
In October, the ESA's Science Program Committee approved Eddington as part of a larger set of initiatives to be implemented between 2008 and 2013. A workshop to discuss the mission will be held June 11-15, 2001, in Spain.
Terrestrial Planet Finder (TPF)
The Terrestrial Planet Finder (TPF) would use an array of telescopes orbiting the Earth in formation to generate planetary pictures 100 times more detailed than those the Hubble Space Telescope could take.
TPF would use a developing technology called nulling to improve vision. Light waves from a star have crests and troughs, just like water waves. If the starlight from two separated telescopes comes together just right, the crests from one and the troughs from the other can cancel each other out, reducing or eliminating starlight. This would allow a view of planets around the star [see animation].
The goal would be to create a census of relatively nearby Earth-sized planets. TPF would study all aspects of planets: from their formation and development to their suitability as an abode for life.
The telescope would study planetary systems as far away as 50 light-years. In addition to measuring the size and temperature, instruments would reveal the relative amounts of gases like carbon dioxide, water vapor, ozone and methane, all of which would help determine whether a planet could support life, or could have supported it in the past.
TPF is targeted for launch in 2011, though it has not been funded. Before the mission can be designed, engineers still need to figure out how to control separate spacecraft flying in formation while also orbiting Earth.
Try this site: http://www.longbets.org/
It's specifically for placing wagers on long-term events.
The Space Interferometry Mission (SIM) would hunt for Earth-sized planets around other stars and provide new insights into the origin and evolution of our galaxy.
A science team for the mission was chosen by NASA November 28, 2000, and the mission is scheduled for launch in 2009. 
SIM would be placed into orbit around the Sun on a path that follows Earth's orbit. Light gathered by its multiple telescopes will be combined and processed to yield information that could normally be obtained only with a much larger telescope.
The mission would also measure the locations and distances of stars throughout our Milky Way Galaxy, and study other celestial objects.
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As if that were possible ;0)
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