Seen here is the birth of a juvenile exoplanet. Using data from the Keck telescope in Mauna Kea, Hawaii, astronomers have directly imaged a newly formed planet growing from the gas and dust of a sun-like star.
The star, LkCa 15, is just slightly smaller than our sun but much younger, only around two million years old. This means that the planet (the blue dot in the right image) is at least five times younger than any other extrasolar planet discovered. The findings, which were presented at a conference on Oct. 19, indicate that the planet is around six times the mass of Jupiter and orbits its parent star at approximately the distance that Uranus is from our sun.
The young planet is strange because it has a higher temperature than would be expected from simulations of planet formation. The protoplanet has likely been caught during the early stages of its life and therefore its mass might fluctuate in the future.
The finding can give astronomers a clearer idea of planetary formation. In this case, because the planet is so far from its parent star, gas and dust in the region are likely to be scarce. A giant planet such as this one probably could not have formed through the process known as core accretion, where a planet gradually accumulates material like a snowball rolling down a hill.
Instead, the planet could have come about when a gravitational instability quickly caused a large mass of gas and dust to suddenly form big clumps that merged into a large planet. The extra heat of the planet may also favor the quicker model of planet formation, since a rapid collapse would have given it a “hot start.”
Image: Kraus & Ireland 2011