Planet formation caught in the act
NASA/JPL-Caltech

Planet formation caught in the act

Astronomers have captured the best observations yet of planets as they’re forming. Although many potential “protoplanets” have been spotted in young star systems, one of the new orbs—in a system that lies a little more than 450 light-years away from Earth in the constellation of Taurus—shines strongly at a particular wavelength that betrays the presence of glowing hydrogen. At that planet’s distance from its sunlike host star (about 2.2 billion kilometers, or about three times the distance of Jupiter from our sun), hydrogen would likely only be heated that strongly when accreting onto a growing planet, the researchers report online today in Nature. The other purported planet orbits the star at a distance of about 2.8 billion kilometers. The distant star and the disk of dust and gas that surround it, dubbed LkCa 15, are only about 2 million years old, the team estimates, and each of the protoplanets is less than 10 times the mass of Jupiter. According to data gathered since 2009, the planets have each made less than one-eighth of an orbit of their star: The closest-orbiting planet makes one circuit every 55 years or so, and the other takes about 80 years to whip around its sun. Observations of LkCa 15 will help astronomers further refine their models of how nascent solar systems and their accreting planets (artist’s concept shown) grow and evolve, the researchers say.