9 exoplanets 'may be orbiting Solar System's twin'

Washington, Apr 8 (ANI): A star 127 light-years away, which stunned the world in 2010 by becoming the largest star system beyond our own, playing host to five, possibly seven alien worlds, is back in the headlines as it may actually have nine exoplanets orbiting it.

HD 10180 is a yellow dwarf star very much like the sun, so this discovery has drawn many parallels with our own Solar System.

It is a multi-planetary system surrounding a sun-like star. But it is also a very alien place with an assortment of worlds spread over wildly different orbits.

It is believed that one of HD 10180's exoplanets is small, although astronomers only know the planets' masses, not their physical size or composition. The smallest world weighs-in at 1.4 times the mass of Earth, making it a "super-Earth".

When it was first revealed that HD 10180 was a multi-planetary system, astronomers of the European Southern Observatory (ESO) detected six exoplanets gravitationally "tugging" on their host star.

Using the "radial velocity" exoplanet detection method, the astronomers watched the star's wobble to decipher up to seven worlds measuring between 1.4 to 65 times the mass of Earth.

Five exoplanets were found to be 12-to-25 times the mass of Earth, "Neptune-like" masses, while another was detected orbiting in the outermost reaches of the system with a mass of 65 Earth masses, a "Saturn-like" world, taking around 2,200 days to complete one orbit.

But now, in addition to verifying the signal of the small 1.4 Earth-mass world, there appears to be another two small alien worlds.

"In addition to these seven signals, we report two additional periodic signals that are, according to our model probabilities ... statistically significant and unlikely to be caused by noise or data sampling or poor phasecoverage of the observations," Discovery News quoted Mikko Tuomi from the University of Hertfordshire as saying.

This basically means that Tuomi has reanalysed the data from previous observations made by the HARPS spectrograph (attached to the ESO's 3.6-meter telescope at La Silla, Chile), confirmed signals relating to the seven exoplanets discovered in 2010 and uncovered two new worlds in the process.

What's more, these two new signals represent another two super-Earths, says Tuomi. One is 1.9 times more massive than Earth and the other is 5.1 Earth-masses.

Although these may be "super-Earths", the only similarity to Earth is their mass, so don't go getting excited that we may have spotted the much sought-after Earth analogs.

The 1.4 Earth-mass exoplanet has an orbital period of only 1.2 days. The two new super-Earths also have very tight orbits, where their "years" last only 10 and 68 days.

Therefore, any question of life existing on these worlds is moot, they will likely be hellishly hot, with no chance of liquid water existing on their surfaces. It's debatable whether these worlds could hold onto any kind of atmosphere as they would be constantly sandblasted by intense stellar winds.

The study has been published in the journal Astronomy and Astrophysics. (ANI)