January 9 – Dark Sky, Bright Worlds

Today’s factismal: The Gemini South Telescope has imaged four planets circling a star 130 light years away!

It is no secret that these are exciting times for astronomers and planetologists. For the first time, we have telescopes capable of detecting planets around other stars; since the first extra-solar planet was detected by the (now defunct) Infrared Astronomy Satellite back in 1984, the number of exoplanets has grown to more than 1,500 confirmed and more than 5,000 possibles. Most of those new neighbors have been identified in just the past few years thanks to new tools such as the Kepler Space Telescope. But you don’t have to go into space to see the new planets; thanks to a large pair of telescopes here on Earth, you can see four of them on your computer!

HR 8799's four planets are ready for their close-up! (Image courtesy Christian Marois (NRC Canada), Patrick Ingraham (Stanford University) and the GPI Team)

HR 8799’s four planets are ready for their close-up!
(Image courtesy Christian Marois {NRC Canada}, Patrick Ingraham {Stanford University} and the GPI Team)

Known as HR 8799 B, C, D, and E (the star is HR 8799, the planets are B, C, D, and E), this planetary system is some 130 light years away. Put another way, if there are people living on one of those planets and they have a telescope that can make out the surface of the Earth, they could watch Chester A. Arthur dedicating the brand new Washington Monument in 1885! Our telescopes aren’t that good yet; the Gemini South Telescope’s Planet Imager can just barely make out the fact that HR 8799 has four big planets and we still can’t see any Earth-size planets. But seeing planets the size of Jupiter is pretty darn exciting.

Why? Because, in the words of one wag, “The Solar System is the Sun, Jupiter, and assorted junk”. Those big planets have most of the mass and, like big bullies everywhere, shove everything else around. In our Solar System, it is the interaction of Jupiter and Saturn that is responsible for most of the craters on the Moon and for many of our long-period comets. In other solar systems, big Jupiter-like planets have forced smaller, Earth-size planets as close to their suns as Mercury is to ours. Needless to say, those Earth-like planets aren’t all that Earth-like; they are more like a burned out charcoal briquette.

But briquette, super-Earth, or Jupiter-wannabe, if you discover a planet, you get to name it! And that’s what citizen scientists like you are doing right now – searching Kepler images for tell-tale signatures of planets around other stars. To join these planet hunters, go to Planet Hunters at:

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