Tales from the Geek, Part Six

Pictures of Mars? Big deal. We got pictures of planets around other stars! I'm sure you've heard about this and probably seen the pictures, but it is just too cool to let pass without mention here.

The first pictures of planets outside our solar system have been taken, two groups report in the journal Science.

Visible and infrared images have been snapped of a planet orbiting a star 25 light-years away.

The planet is believed to be the coolest, lowest-mass object ever seen outside our own solar neighbourhood.

In a separate study, an exoplanetary system comprising three planets, has been directly imaged, circling a star in the constellation Pegasus.

The single planet is orbiting the visually-bright star Fomalhaut ("mouth of the whale" or "mouth of the fish") in the constellation Pisces. It's a blue star, hotter and younger than our Sun, with about double its mass. In the picture to the left, the light from Fomalhaut is blocked out in order to make out the planet which otherwise would be lost in the glare.

The presence of the planet in the disc of dust and gas around the star, which is leftovers from its formation, plus the fact that the disc is so sharply defined add strength to the leading hypothesis of planetary formation, that of accretion, where bits of dust in the disc cling together by gravitational or electrostatic attraction. Over time, these bits collide with other bits which become bigger bits, and so on.

The team estimates that the planet, dubbed Fomalhaut b, is 11bn miles away from its star, about as massive as Jupiter and completes an orbit in about 870 years. It may also have a ring around it.

The three-planet system is around a star 130 light years away. It's designated HR 8799, and is perhaps just visible to the naked eye in the constellation Pegasus. They planets were imaged using infrared light coming from them.

According to a theoretical model that accounts for the light coming from the planets, they range in size from five to 13 times the mass of Jupiter and are probably only about 60 million years old.

Which accounts for the infrared light: They are still pretty hot, having only recently (in astronomical terms) formed.

The really exciting thing about this is that being able to see the planets directly rather than inferring their presence either from their dimming effect on their star's observed light as they transit it or by their gravitational effect on its rotation, it will be possible to study them - including any atmosphere - in far greater detail.

There are now 228 known exoplanets around nearby stars. Just a few years ago people were seriously wondering if there were any.