November 19, 2012
Two College of Charleston undergraduate research students, part of a team led by Professor Joe Carson, analyzed images from one of the world’s largest telescopes and identified a new extrasolar planet. Through careful processing of the images, they achieved a direct image of the faint object. To put the discovery in perspective, of the nearly 850 extrasolar planets – planets orbiting stars other than the Sun –currently known, only a minute fraction have been captured in actual astronomical images. The vast majority of detections rely on indirect methods.
“Just discovering a new extrasolar planet is exciting,” says Carson, an astronomy professor who also works with the Max Planck Institute for Astronomy (MPIA). “But, under these circumstances, with the direct involvement of undergraduate researchers, it is particularly exciting. Thea Kozakis and Laura Stevens analyzed the raw data from the telescope and identified the candidate exoplanet in their final, processed image. They nicknamed the planet ‘Derek’, which is still what we call it in our group meetings at the College of Charleston.”
Following Kozakis’ and Stevens’ initial results, Carson’s team carried out follow-up observations to confirm its identification. Kozakis and Stevens analyzed the follow-up data and confirmed that the faint object was an orbiting companion of the star, and not an unrelated background star. Based on their positive results, Carson worked with his collaborators from around the world, including MPIA, NASA Goddard Space Flight Center, National Astronomical Observatory of Japan (NAOJ), and Princeton University, to characterize the planet with additional follow-up observations, and to carry out optimized re-analyses of the original data.
The discovery of κ And (kappa Andromedae) b, as the planet is called, was made using the Subaru 8-meter telescope on the summit of Mauna Kea in Hawai’i, operated by the National Astronomical Observatory of Japan. The observations were carried out as part of the Strategic Explorations of Exoplanets and Disks with Subaru, led by Principal Investigator Motohide Tamura (NAOJ).
Carson explains the significance of being able to get a direct image of the exoplanet. “With a direct image, the planet is immediately accessible for myriad follow-up examinations such as spectroscopic analysis. Such studies can reveal detailed information on the planet’s atmospheric chemistry and dynamics. Among other benefits, this allows us to compare the planet’s atmospheric features with those of our own solar system planets.”
Carson also notes that the kappa Andromedae system is also unique because the Super-Jupiter has an orbital separation similar to that of our own solar system’s outer planets. That suggests that the kappa Andromedae planet formed in a manner similar to that of lower mass planets. It is by far the most massive star to show strong evidence of this type of planet formation. There are some other stars that are equally massive and have known planets, but these other planets are either in extremely wide orbits, well beyond those of the Solar System planets, or exist around stars that have already reached the end of their normal nuclear-burning lifetime.
The discovery of the Super-Jupiter κ And b suggests that stars as massive as 2.5 solar masses are still fully capable of producing planets within their primordial circumstellar disks – key information for researchers working on models of planet formation.
Carson’s research is funded by the National Science Foundation (NSF) through a $286,568 grant.
A video of Carson talking about previous discoveries.:
An article in the College of Charleston Magazine about Carson:
Forget the suntan lotion, sandals and shades. When Joe Carson takes a trip to Hawaii, he packs a winter coat. Carson is an astronomer, so that could explain his apparent confusion. His mind is more often out of this world than in it, and outer space can indeed be very, very cold.
Yet there’s a method to this physics and astronomy professor’s madness, and Carson knows that – while his fellow airplane passengers are most likely bound for Oahu’s picturesque Waikiki Beach and Diamond Head State Monument – he’s hopping over to the Big Island for a visit up Mauna Kea. Standing 13,796 feet above sea level, the volcano is Hawaii’s highest point, and its summit is often blanketed with snow, hence the need for that thick jacket. The top of Mauna Kea is also covered in high-powered telescopes, including the 8.2-meter Subaru optical-infrared telescope that Carson uses to take pictures of the stars and surrounding planets.
Like any photographer, Carson says he appreciates the aesthetics of the mesmerizing thermal photos he and his colleagues take. But one would be foolish to dismiss his snapshots as mere pretty pictures. Indeed, when one considers the cosmic consequences of Carson’s work, the effect is mind blowing.
In 2009, Carson was a leader of a team of researchers from Germany’s Max Planck Institute for Astronomy that took an image of what they’re calling a “planet-like object” more than 50 light years from Earth. Though scientists have been discovering planets beyond our solar system for more than a decade (about 400 exoplanets have been found), it’s incredibly rare to obtain a direct image. Usually, these exoplanets are detected indirectly, such as by seeing how a nearby star dims when the exoplanet passes before it.
Yet, by focusing on young planets located a healthy distance from the stars they orbit, it is possible to snap a direct image. Young planets retain more heat left over from their creation, making them more visible when looking through infrared filters. And the farther a planet is from its star, the better the chance it will not be obscured by the immense amount of light being produced by the star.
And so it was that Carson and his colleagues were able to photograph a planet-like object orbiting the star GJ 758 – an achievement Time magazine named as one of the top 10 scientific discoveries of 2009. Carson and fellow researchers are still unable to say definitively whether the object is a planet or a brown dwarf (otherwise known as a failed star), but their achievement was nonetheless impressive because of the very complicated game of hide-and-seek that astronomers and exoplanets play.
The single image of the star and its planet, explains Carson, is actually a manipulation of more than 500 images. In order to filter the images and reveal this potential hidden planet, Carson and a colleague created a complex software program, which he calls a pipeline, to process many images of the same star.
Though half of the stars in the sky are thought to have planets orbiting them, finding proof of other planets beyond our solar system can be a frustrating task, akin to finding a needle in a cosmic haystack. Carson himself has looked at 150 stars and so far found only this one possible planet.
This year, Carson was part of a research team that photographed the birth of a planet system. Such accomplishments, he says, help scientists determine just how rare or common life is on other planets and which planets have the best chances of exhibiting signs of life. Above all, it helps us learn about our own solar system’s history and how we happen to be walking around this earth. For Carson, snapshots of other planets can help answer some of the most fundamental questions.
“We want to understand better where we come from,” says Carson. “How exactly, did our own planet system come to be?”
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For more information, contact Joe Carson at carsonj@cofc.edu or 843.953.3643.
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