Skip to comments.Earth: no longer the lonely planet
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.
Just ask Colonel Hammond.
|I think we will find a Earth like planet in 20 - 30 years. Any takers?
Kepler, a NASA Discovery mission, is a spaceborne telescope designed to look for Earth-like planets around stars beyond our solar system.
"The Kepler Mission will, for the first time, enable humans to search our galaxy for Earth-size or even smaller planets," said principal investigator William Borucki of NASA's Ames research Center, Moffett Field,
California. "With this cutting-edge capability, Kepler may help us answer one of the most enduring questions humans have asked throughout history: Are there others like us in the universe?"
Kepler will detect planets indirectly, using the "transit" method. A transit occurs each time a planet crosses the line-of-sight between the planet's parent star that it is orbiting and the observer. When this happens, the planet blocks some of the light from its star, resulting in a periodic dimming. This periodic signature is used to detect the planet and to determine its size and its orbit.
Three transits of a star, all with a consistent period, brightness change and duration, provide a robust method of detection and planet confirmation. The measured orbit of the planet and the known properties of the parent star are used to determine if each planet discovered is in the habitable zone; that is, at the distance from its star where liquid water could exist on the surface of the planet.
The industrial partner for development of the hardware is Ball Aerospace & Technologies Corp., based in Boulder, Colorado. The mission is managed by NASA's Jet Propulsion Laboratory.
Scheduled to launch in 2007, Kepler will hunt for planets using a specialized one-meter diameter telescope called a photometer to measure the small changes in brightness caused by the transits.
The key technology at the heart of the photometer is a set of charged coupled devices (CCDs) that measures the brightness of hundreds of thousands of stars at the same time. CCDs are the silicon light-sensitive chips that are used in today's TV cameras, camcorders and digital cameras. Kepler must monitor many thousands of stars simultaneously, since the chance of any one planet being aligned along the line-of-sight is only about 1/2 of a percent.
Over a four-year period, Kepler will continuously view an amount of sky about equal to the size of a human hand held at arm's length or about equal in area to two "scoops" of the sky made with the Big Dipper constellation. In comparison, the Hubble Space Telescope can view only the amount of sky equal to a grain of sand held at arms length, and then only for about a half-hour at a time.
NASA selected Kepler as one of two Discovery missions from 26 proposals made in early 2001. The missions must stay within the Discovery Program's development cost cap of about $299 million. The Discovery Program emphasizes lower-cost, highly focused scientific missions.
Would it matter? Whatever we find will be too far away to have anything to do with it.
Second, the methods used to determine that a planet is "earth like" will likely disappoint you and make you question whether we've found what someone says we've found. If you think we're using powerful telescopes and actually looking at the alleged planets, guess again.
Which makes me question this whole "25% of stars have planets" thing. In order to detect an alleged planet, the planet has to pass between us and the remote star - that is, transit across the face of the star from our point of view. Now, think about that. What if we're not aligned with the ecliptic of that system. We'd never even see a single planet yet the system may have many.
And searching for rhythmic flickers in remote stars is far less glamorous than some of these articles try to make it sound in our "search for habitable planets".
Man, I must be in a bad mood or something. I love science and astronomy - I guess I just hate the hype sometimes.
It'll take a while to get to that exciting exotic Proxima II.
4.3 light-years in only 50,000,000 years if you floor it!
Good point, but of billions and billions of planets, the prospects for ertra terrestrial life are fascinating.
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.
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.
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.
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.
As if that were possible ;0)
IOW, even if there is a great deal of life in the galaxy it doesn't mean that The Earth won't remain, effectively, "lonely".
I'm a skeptic, frankly. I don't think we will detect extraterrestrial life anytime soon (say within the next hundred years). In fact, and of course I'm just guessing, I don't think the probability is particularly good that we will discover it in the next thousand years, even though I also tend to think that extraterrestrial life does exist.
Question... and would we know intelligence if we saw it..?
Uh, that's GENERAL Hammond. The Colonel is O'Neal.
Hey! The galaxy grew again!
Qball phone home!
Kidding, right? You can't even find a great apartment in 20-30 years.
Here's what will happen: we will find a planet close enough so that we can transform it to a base condition we like. This transformation will take a really long time, a million years just to pick a number. But we will find a close enough planet in 20-30 years, it just won't be what Joe Sixpack would call earthlike.