It’s just a few small pixels, but the image above marks a giant leap for our capacity to explore worlds beyond the influence of the sun. Taken with the Gemini Planet Imager, recently fitted to the Gemini South telescope in Chile, the bright dot represents Beta Pictoris b, one of the most famous planets beyond the solar system.
The larger circle, looking like the freeze frame of a drop of water after it has landed on a pond, is centred on the star Beta Pictoris itself, after its light was subtracted so that it would not overwhelm the planet itself. The Planet Imager was specifically designed for such work, with “Advanced adaptive optics, diffraction control, a near-infrared spectrograph, and an imaging polarimeter” according to the team that took this image.
The twenty one institutions that came together to make the image possible hailed the photo as “an order of magnitude better than conventional adaptive optics imagers” . They also claim that the measurements taken in the process allow “a factor of three improvement of most parameters” in regard to understanding Beta Pictoris b’s orbit.
Beta Pictoris lies 63.4 light years away, close to Canopus in our skies (and thus not visible from northern latitudes). It is very young by the standards of stars, an estimated 12 million years old, and consequently one of our best opportunities to witness the formation of planets. It still has large clouds of gas and dust surrounding it that are expected to eventually condense.
However, planetary formation is well underway, with an object 4-11 times the mass of Jupiter thought to be herding comets together. Naturally such a system attracts plenty of interest from astronomers, and recently discoveries have been coming thick and fast. Just two weeks ago the length of a day on Beta Pictoris b was measured at eight hours, the first time this has been done outside our solar system.
Back in 2008 Beta Pictoris B was one of the first planets beyond the solar system to be directly observed, rather than being detected through its effect on light from its parent star.
While this image lacks the dramatic wings of gas seen in the previous previous one (see below) we can see the planet Beta Pictoris B with much greater clarity. Although it looks as though it is almost touching its parents star this is a product of the angle at which was are seeing them. In fact the star and planet are separated by the same distance as Saturn and the sun. This makes it a relatively easy target for the Gemini Planet Imager, which will now be turned towards other objects.
Future targets will be harder, however. Very young planets such as Beta Pictoris b are bright in the infrared part of the spectrum as they are still hot from the release of gravitational potential energy as they accumulate.
The finding was announced in Proceedings of the National Academy of Sciences, where the tantalizing prospect of a possible planetary transit in 2017 is revealed. Unfortunately, the chance of this event is put at just 4%, but should it occur would provide great prospects for learning more about this system.