Striking Gold 90 Light Years Away

With the recent discovery of a Jupiter-like 
planet much has come to light, writes Biplab Das 

Of over 100 star-planet systems found so far, the Jupiter-like planet orbiting a sun-like star 90 light years away from earth recently discovered by a team of researchers comprising astronomers from Britain, Australia and America is almost similar to our solar system. 

"This planet is going round in a nearly circular orbit three-fifths the size of our own Jupiter," said Hugh Jones of Liverpool John Moores University who led the research team of British astronomers. "This is the closest we have yet got to a real solar system-like planet, and advances our search for systems that are even more like our own," he told a conference on "Extrasolar Planets: Today and Tomorrow" in Paris on 3 July. 

The planet was discovered using the 3.9-metre Anglo-Australian Telescope in New South Wales, Australia. "It is the exquisite precision of our measurements that lets us search for such Jupiter-like planets," said Dr. Alan Penny from the Rutherford Appleton Laboratory. "The newly detected planet is harder to locate compared to more exotic planets found so far." 

The new planet has a mass about twice that of Jupiter and circles a star called HD 70642 about every six years. The star resides in the constellation known as Pupis and the distance between it and the planet is 3.3 times the distance between the earth and the sun. In other words, the planet could have been about halfway between Mars and Jupiter if it were in our solar system. 

For years, astronomers have been searching for systems with giant planets in long circular orbits and small rocky planets on shorter circular orbits. The discovery of this Jupiter-like planet is a giant leap toward that goal. 

Theoretically speaking, astronomers have long predicted the possibility of finding planetary systems similar to our solar system. They even speculate that those planetary systems could harbour giant planets orbiting in a circular path four times the distance between the earth and the sun and moderate planets in the inner orbits. 

With the discovery of the new planet and other extra-solar planets, many unknown facts of extra-solar planetary systems have come to light. "The planetary systems are much more diverse than ever imagined," said Penny. The new planet, along with others, has been found to revolve around one-tenth of the stars in the region, which the astronomers scanned with their telescope. This means that every solar system-planet circles most stars, but largely elude the scope of earth-bound telescope. 

Finding solar system-planets also raises the question: are these habitable like earth? The answer is a firm 'no' as many of these lie in elliptical orbits and so are extremely inimical to supporting any forms of life. Before finding this Jupiter-like planet, the only gas giant was detected in the constellation of stars called 47 Ursa Majoris. It harbours a giant planet that orbits a star at a distance three times that between the earth and the sun. 

The Ursa Majoris also includes another gas giant circling at a distance twice the distance between the earth and the sun. "But the newly discovered Jupiter-like planet orbiting a sun-like star bears the closest likeness to our solar system found to date," said Jones. "It demonstrates that our searches are precise enough to find Jupiter-like planet in Jupiter-like orbit." 

For this precision in technique, the credit goes to Paul Butler of the Carnegie Institute in Washington, and Geoff Marcy of the University of California, Berkeley. They have devised a technique that measures how much a star wobbles in space due to the gravitational pull of a nearby planet. As a planet orbiting a distant star remains unseen, its gravitational tug causes the star to move back and forth in space, causing it to wobble. 

This wobble can be detected in the star's light, providing a clue to the presence of an orbiting planet. The discovery of other such planets and planetary satellites will help astronomers fathom the universe more accurately and assess whether planetary systems like our own are common or rare.