A Handful of Planets Found Around HD 10180

"Alien Solar System Looks Strikingly Like Ours "
Space.com (August 24, 2010)

"Astronomers have discovered a group of at least five planets – with hints of two more – circling around a star in an arrangement similar to our own solar system. Confirmation of the extra planets would make this the highest tally of alien worlds ever spotted around a single star.

"The planets and their own sun-like star are about 127 light-years from Earth, astronomers with the European Southern Observatory said. It is one of just 15 planetary systems known to have more than three worlds.

"The five planets circle their parent star, HD 10180, in a regular pattern like the planets of our solar system, only in a more compact arrangement, the researchers said.

"Of the two potential additional planets that may be present, one may have a mass that is the closest to the Earth's yet seen, if it is confirmed, they added. [The Strangest Alien Planets]..."

Five planets (at least) in about as much space as the first three of our star's planets orbit are a trifle crowded: by Solar system standards. But HD 10180 sounds like a remarkably close match to the planetary system that our Earth is in: right down to the nearly-circular orbits.

It doesn't sound like any of the five (or seven, if educated guesses about extra wobbles are correct) could support life-as-we-know-it. Still, HD 10180 should give astronomers and cosmologists a chance to fine-tune their theories on planet formation.

The Space.com article gives a little detail about the orbits of these new-to-us planets:

"...The closest planet is not quite 5.6 million miles (9 million km) from HD 10180, compared to the 93 million miles (150 million km) separating Earth from the sun, a distance also known as an astronomical unit. The distance of the farthest one from its star is about 1.4 AU.

"When compared to our solar system, all of these planets would fit inside the orbit of Mars and appear to have nearly circular orbits...."

Whatever the planets of HD 10180 are, they don't seem to be gas giants.

The Lemming is looking forward to learning more about those worlds.

Exciting times, these.