The extra-solar planet menagerie of worlds just got a bit stranger this week.
Several announcements came out of the 224th meeting of the American Astronomical Society held in Boston earlier this week highlighting the diversity of worlds that push the envelope for classification. As J.B.S. Haldane once said, “the universe isn’t stranger than we imagine… its stranger than we can imagine.” Here’s a rapid fire run down of the latest additions to the Exoplanet Catalog of known worlds, which currently stands at 1,794 and counting.
A Mega Earth: First up is Kepler-10 c, a rocky world 17 times the mass of the Earth 560 light years distant. Astronomers were surprised to find something so hefty that wasn’t a gas giant world. “We were very surprised when we realized that what we had found,” said astronomer Xavier Dumusque of the Harvard-Smithsonian Center for Astrophysics.
Kepler-10 c was nabbed by transits of its host star observed by the Kepler space telescope and its mass was pinned down by follow-up observations using the HARPS-North instrument on the Telescopio Nazionale Galileo based in the Canary Island. The system has two worlds orbiting a star with 90% the mass of our Sun, at 20 hours and 45 days respectively.
Doomed Worlds: Next up, researchers revealed two worlds destined for destruction. Kepler-56b and Kepler-56c orbit a red giant star 1.3 times the mass of our Sun. With orbits of 10.5 days and 21.4 days respectively, these worlds have about 130 to 155 million years – a short time by astronomical standards – before they’ll be engulfed by their host star.
Only Kepler-56d might just escape such a fate. “As far as we know, this is the first time two known exoplanets in a single system have been predicted at ‘time of death’,” said lead author on the study Gongjie Li of the Harvard-Smithsonian Center for Astrophysics.
Flavors of exoplanets: Also highlighted at the 224th AAS meeting were the difficulties that planets may face orbiting tempestuous red dwarf stars.
Researcher Ofer Cohen noted three candidate worlds in the Kepler catalog – KOI 1422.02, KOI 2626.01 and KOI 584.01 – and noted that even a robust magnetic field like the Earth’s wouldn’t protect these worlds from having their atmospheres stripped by the fierce solar winds.
And it was also announced in a survey by CfA’s Lars Buchhave sampling 400 stars and 600 exoplanets that rocky planets mainly maxed out at 1.7 the size (diameter) of the Earth, while gas giants started out at a minimum size of 3.9 Earths. Those in between worlds have been dubbed “gas dwarfs.”
Ancient worlds: And finally, a unique system of worlds was announced on Tuesday courtesy of the Carnegie Institution orbiting Kapteyn’s Star just 13 light years distant. One, Kapteyn-B, weighs in at 4.5 Earth masses and orbits the red dwarf star once every 48.6 days.
This places it in the star’s habitable zone were liquid water might just be able to exist. Kapteyn’s Star is an ancient halo star over 11 billion years old and is the closest example of such a star to our own solar system. This would also make Kapteyn B and C the oldest known super-Earths yet discovered, as Earth is still at the tender young age of about 4 billion years old. What might such bizarre worlds look like up close? What are their prospects for harboring life?
A new generation of exoplanet hunters, to include the TESS and the James Webb space telescope are set to take to space over the next few decades to characterize these and many more strange new worlds.