Joanna Carver, reporter
A false-colour near-infrared image shows the ? And system after most of the light from the host star has been digitally removed, revealing the new exoplanet (top left) (Image: NAOJ)
Jupiter has a new reason to be jealous. The latest picture of an exoplanet features a super-Jupiter that's nearly 13 times as massive as our largest world. The heavyweight orbits a star that is about 2.5 times the mass of the sun, making it the most massive star to host a directly imaged exoplanet.
Of the roughly 850 known planets, fewer than a dozen have had their picture taken. That's because today's telescopes have a hard time picking out the light of a planet from the glare of its host star.
"It's kind of like seeing a firefly next to a lighthouse," says Joseph Carson, an assistant professor of astronomy at the College of Charleston in South Carolina.
Carson and colleagues want to find out how massive a star can get and still form planets. It's thought that planets are born in discs of debris left over from a star's formation. Some theories hint that more massive stars should have a greater amount of this planetary starter material and so should develop more giant planets. But massive stars would also shine brighter, so their intense radiation might blast away the debris discs before planets have time to form.
During a recent survey of massive stars using the Subaru telescope in Hawaii, the team focused on the young star Kappa Andromedae (? And), which sits about 170 light years away. Aided by custom software written by Carson's students, the researchers digitally removed light from the star, revealing a bright object nearby. Based on its motion, the team could tell that the object is orbiting ? And.
A signal-to-noise ratio map of the ? And system after most of the starlight has been removed. Coloured spots are leftover light from the host star, while the bright white dot shows the high confidence level for the new exoplanet (Image: NAOJ)
Technically the newfound world is near the boundary between giant planets and brown dwarfs, "failed" stars that are not massive enough to ignite hydrogen fusion in their cores. Carson admits that this object may be a brown dwarf, but he thinks that is unlikely. Brown dwarfs are massive enough to burn deuterium, and it seems this object is just below the threshold.
"Our best guess for the mass of this, which depends on a number of theoretical models, is that we wouldn't expect this to have any nuclear burning in its core at all. But there's a lot of uncertainty," says Carson. "If it was a brown dwarf, it would be on the lowest-mass end of a brown dwarf."
Journal reference: arxiv.org/abs/1211.3744
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