Rare Image of Super-Jupiter Sheds Light On Planet Formation
Of the nearly 850 exoplanets –- 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. The reason for this discrepancy: stars are much brighter than their planets (typically by a factor of a billion or more); using traditional observational techniques, the planet will be hidden in the glare of its host star.
Now, a research team led by Joseph Carson (College of Charleston and Max Planck Institute for Astronomy) has managed to obtain an image of a large "Super-Jupiter" around the massive Kappa Andromedae. Their discovery makes use of the Subaru 8-meter telescope on the summit of Mauna Kea in Hawai'i, operated by the National Astronomical Observatory of Japan.
Kappa Andromedae is a very young star, with an estimated age of 30 million years (our Sun, for comparison, is around 5 billion years old). Obtaining an image of its companion Kappa Andromedae b required advanced techniques both for observation and for image analysis. A particular challenge was that the orbit of the newly detected object is only somewhat larger than that of Neptune – most planetary images have been obtained for planets in significantly larger orbits.
With a mass of about 13 times that of Jupiter, the object, called Kappa Andromedae b, could be either a planet or a very lightweight "brown dwarf", an object that is intermediate between planets and stars. Circumstantial evidence indicates that it is likely to be a planet.
The discovery of the Super-Jupiter Kappa Andromedae 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.
A key advantage of direct exoplanet detection is the target's immediate accessibility for follow-up examination by traditional astronomical techniques, such as an in-depth analysis of its light by spectroscopy. This is the aim of ongoing observations of the light emitted by κ And b across a broad range of wavelengths. The ongoing observations will lead to a better understanding of the gas giant's atmospheric chemistry, and yield more precise information about the object's orbit and the possible presence of additional planets. In the end, the astronomers should have a better picture of the Super-Jupiter's genesis, and about planet formation around massive stars in general.