Posted on 07/03/2003 9:20:02 AM PDT by John W
An international team of planet hunters have found the closest thing yet to a solar system similar to our own out in space; a Jupiter-like planet orbiting its parent star in a Jupiter-like orbit.
Researchers with the Anglo-Australian Telescope (AAT) in New South Wales, Australia detected a large planet orbiting HD 70642, a Sun-like star situated 90 light-years from Earth out toward the Puppis constellation. The planetary find was announced Thursday in Paris at the "Extrasolar Planets: Today and Tomorrow" conference.
"It's absolutely wonderful," Alan Penny, of Britain's Rutherford Appleton Laboratory, told SPACE.com . "Up to now we've seen a whole menagerie of planet orbiting their stars. But when it comes to finding another Jupiter at a Jupiter-like distance from its star, this is the first one."
Penny is a member of the United Kingdom portion of the UK-Australian team at the AAT seeking extrasolar systems that resemble our own planetary neighborhood. Hugh Jones, of Liverpool John Moores University and leader of the UK contigent, presented the discovery at the Paris conference.
The planet circling HD 70642 is about twice as massive as Jupiter and orbits its star from a distance of 3.3 astronomical units (AU), which would place it somewhere between Mars and Jupiter in our Solar System. One AU is the distance between the Earth and the Sun, about 93 million miles (149 million kilometers), and Jupiter typically circles the Sun from an orbit of 5.2 AU. The new planet is faster than Jupiter too, completing one orbit in only six years, about half the time it takes Jupiter to round the Sun.
But what sets HD 70642's giant planet apart from other extrasolar worlds -- more than 100 of which have been found -- is its orbit. The newly found planet travels around its star on a path that, like Jupiter, is roughly circular, meaning there's room for smaller, Earth-like planets to orbit HD 70642 without the danger of being flung out of the planetary system.
Planet hunter Paul Butler, who established the extrasolar world-seeking team at AAT, told SPACE.com that to date, most of the giant planets found have extremely eccentric orbits around their stars, more egg-shaped then circular. If you were to put the Earth in one of these planetary systems, he explained, its orbit would be dynamically unstable and the big planets would just fling it out in to space.
Before HD 70642, the only other extrasolar planet with a circular orbit of more than three AU was the outer world circling the star 47 Ursa Majoris. That planetary system, however, also has an inner gas giant orbiting at about two AU, a planetary addition our Solar System lacks.
"But if you put an Earth-like planet in this new system [around HD 70642] it would stay," Butler said.
The difference is critical for researchers bent on the search for planetary systems that mirror our own Solar System, and in doing so learn more about how the Earth formed and life began on our planet. It is even more critical for scientists hoping to find another Earth-like planet with the potential to sustain life, extraterrestrial or otherwise.
Seven years ago Butler, of the Carnegie Institute of Washington, and Geoff Marcy, of the University of California, Berkeley, began developing the technique used today to find large extrasolar planets. The "wobble" technique, seeks out a potential planet's gravitational effects on its parent star.
Just as the star's gravity pulls on its planet to keep it in orbit, the planet's gravity pulls on its parent star causing it to move back and forth. This "wobbling" can be observed by ground-based telescopes and alert researchers to the existence of extrasolar planets. The "wobble" of HD 70642 is a mere seven miles an hour (or 7 meters each second), researchers said.
"But we can only see the equivalents of Jupiter or Saturn," Butler said. Future space-based efforts by NASA and the European Space Agency (ESA) could help astronomers detect smaller planets orbiting close to their stars, and verify the planets that have already been discovered like the one around HD 70642, he added.
Efforts to use space telescopes like NASA's planned Space Interferometry Mission (SIM), slated for a 2009 launch, its Terrestrial Planet Finder (TPF) project and ESA's six-instrument Darwin flotilla could give astronomers the ability to not only see small Earth-like planets, but examine them for signs of water or life. The TPF and Darwin missions are expected to begin somewhere around 2015.
Once those missions are up and working, scientists will be able to point them at HD 60742 and a half dozen other stars extrasolar planet hunters have earmarked for the possibility of small, inner planets. "You wouldn't see any mountains or oceans or espresso bars, but a single dot or pixel, that you could then pass through a spectrometer and search for signs of oxygen, water vapor or methane," Butler said. "It won't be proof of life, but the suggestion of life."
The possibility of finding a life-bearing planet, coupled with the chance of discovering whether our Solar System is your average star system or just a fluke, makes the hunt for other worlds all the more exciting.
"I think the hunt for these planets is the greatest adventure in astronomy right now," Penny said.
Your ruminations are pretty close to standard theories of planetary formation.
One additional tidbit: the most favored theory of planetary formation theorizes that all planets start out Jupiter like, until the star at the center of the system starts the nuclear fusion process; the solar radiation then "boils off" the outer, light gas layers of the inner planets (Mercury, Venus, Earth, Mars,) leaving behing only the rocky core. The outer planets are too far away for the solar radiation to do this, so the remain essentially as they formed, gas giants, with a rocky core.
At Warp 8 that's only 32 days travel time.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.