The video below provides the best images ever taken of a planet orbiting another star. The resolution may still be tiny, but it represents the start of another big step forward in our process of learning about worlds beyond the Solar System.
Image: 18 months of Beta Pictoris b's 22-year orbit. Credit: M. Millar-Blanchaer, University of Toronto; F. Marchis (SETI Institute)
The last few years have seen a blizzard of exoplanet discoveries. Most have been made using the Kepler space telescope to observe tiny drops in light emitted by stars as the planet passes in front. A smaller number are the result of the more traditional Doppler wobble method, where the planet's gravity affects its parent star's motion relative to us.
Both methods can only provide limited information, motivating the push for direct imaging of planets, which offers us a chance to learn about their chemistry and temperatures.
Beta Pictoris b has been a favorite target for direct planet spotting. Last year, astronomers used the Gemini South telescope to produce the best single image yet taken of an exoplanet, subtracting the light of the star Beta Pictoris to allow the giant planet to shine through.
The video accompanies a paper in the Astrophysical Journal that reports a series of findings about the Beta Pictoris system, which were gathered in the course of the observations collected to make the video.
"It's fortunate that we caught β Pic b just as it was heading back – as seen from our vantage point – toward β Pictoris," said author Dr. Laurent Pueyo of the Space Telescope Science Institute in a statement. "This means we can make more observations before it gets too close to its parent star and that will allow us to measure its orbit even more precisely."
A number of factors make Beta Pictoris so popular. At 63 light-years away, it is relatively close by astronomical standards. Moreover, as an exceptionally young star, its planet has yet to cool below 1600K, making it bright in the infrared. Ten to 12 times the mass of Jupiter and orbiting at a distance similar to Saturn, Beta Pictoris b is also far enough from its parent star to not be lost in the glare. Finally, the system contains a debris disk that is expected to eventually coalesce into additional planets.
Such proto-planetary disks are easier to see than the planets they will become, and are valued for the information they provide about the planet formation process, and one being sculpted by a formed planet is particularly interesting.
The paper reports, “the modeled inner radius of the disk is farther out than expected if caused by β Pic b” and “the mutual inclination of the inner disk and β Pic b is ∼ 4◦, when it is expected to be closer to zero.” Neither of these observations have been explained, but the questions may lead to further insights into the Beta Pictoris system, and possibly planet formation in general.