By Wilson da Silva
AUSTRALIAN astronomers have discovered a planet so small and far away that it cannot be seen.
The presence of HD 76700b, named after the catalogue identification of its parent star, was inferred by the slight wobble it produces in its parent as the planet spins around it every 3.97 days.
The 101st planet claimed outside our solar system, HD 76700b is the second smallest so far discovered: about one-fifth the mass of the gas giant Jupiter, which is the largest of the nine planets orbiting our sun.
Dr Chris Tinney of the Anglo-Australian Observatory told delegates at the Bioastronomy 2002 conference on Hamilton Island that the new planet was about 200 light-years away, making it one of the most distant so far detected.
The planet was in a tight, circular orbit even closer than Mercury, the planet closest to the sun in our solar system.
“The exciting thing about it is that this is such a small planet, and if we can detect this, it makes us more confident of finding more solar systems more like ours,” Dr Tinney said yesterday.
His team first spotted the planet six months ago using the Anglo-Australian Telescope near Coonabarabran in western NSW.
Since the tiny wobble was first spotted, Dr Tinney’s team has been making repeated observations, collecting more data to ensure what they were seeing was real.
Until a few days ago, the team had been worried that the wobble might have been caused by solar eruptions on its surface, which can sometimes knock a star about, but this has now been discounted.