It doesn't look like much, but the above photograph records a fairly rare event: the direct imaging of an exoplanet, the term for planets that do not reside in the Solar System. The picture was captured using infrared photography by a team of astrophysicists at the European Southern Observatory in Garching bei München, Germany, and published in the most recent issue of Astrophysical Journal Letters. The planet, christened HD 95086 b, is thought to be between 10 and 17 million years old and, based on its perceived brightness, to possess approximately 5 times the mass of Jupiter, making it the lightest such object ever to be directly filmed by human beings. It's a little bigger than the sun, and its system is more than 300 million light years away.
Officials at the European Southern Observatory explained that most exoplanets are discovered indirectly, without ever being confirmed by eyesight:
Astronomers have already confirmed the existence of nearly a thousand planets orbiting stars other than the Sun. Almost all were found using indirect methods that could detect the effects of the planets on their parent stars — the dips of brightness produced when planets crossed in front of them (the transit method), or the wobbling caused by the gravitational pull of planets in their orbits (the radial velocity method).
So what makes exoplanets so difficult to see from space? The stars they happen to orbit. Stars emit far more light than any of the terrestrial or gaseous planets caught in their orbit, washing out (with their persistent glare) most hope of seeing the shape of a planet. In addition to the methods mentioned above, astrophysicists substitute a bevy of indirect techniques to make up for their frequent inability to photograph far-away planets. One technique, for example, depends on an effect called gravitational microlensing, whereby a star (and, in relevant cases, a planet orbiting the star) magnifies the light of another star.
While rare, this type of photograph is becoming more common, thanks to developments in satellite technology, for which scientists keep asking for more money — and, well, a lot of luck. Four years passed between astrophysicists first photographing an exoplanet in 2004 and capturing six more in 2008, none in 2009, one in 2010, then four more in 2011. (Last year just one planet, Kappa Andromedae b, found itself photographed.) Five months into 2013, stargazers will need a bit more luck to strike a new record.
- European Southern Observatory