Hot, Pink and with a Tail: Mercury to be Visible in February

12 February 2013

There is a fascinating, small planet out there you can see with your own eyes this week. It resembles a comet with its long tail; its days are longer than its years; it's red-hot and ice-cold and it looks pink. It's Mercury, the small planet closest to the sun, known by astronomers for thousands of years yet being discovered all over again since NASA's MESSENGER probe went into orbit around it in 2011.

In the course of two weeks in February, this strange and beautiful planet will be visible, starting about half an hour after sunset. It's not actually pink but appears so because of the rosy hues of the setting sun. As February unfolds, Mercury will ascend and will brighten as it rises higher. You can watch it for an hour after sunset from 11 February through 21 February.

This "pink planet" circles the sun about three times closer than Earth does and rotates just three times on its axis every two Mercury years. This slow spin so close to the sun makes its surface completely dry, with daytime temperatures reaching 425 degrees Celsius, which is hot enough to melt lead. Yet as the MESSENGER probe recently confirmed, this hot planet has huge deposits of ice at its poles, enough to encase Washington DC with a layer of ice two miles thick. This is possible because the tilt of Mercury's spin axis is almost zero, so there are hidden places at its poles than are never exposed to sunlight. Some parts of the ice are coated with a strange dark substance that researchers suspect to be a mix of organic compounds resulting from the impact of comets and asteroids.

Mercury's long tail, spotted in 2008 by NASA's twin STEREO probes, is just like a comet's tail pushed in the anti-sunward direction. As the sun approaches the peak of its 11-year activity cycle, this strange planet will be hit by the stormiest space weather in years, with researchers able to watch the processes that turn it into a comet planet. This is really a strange and fascinating planet and sky watchers can step outside and see for themselves when the sun sets tonight.