Young Super-Neptune Offers Clues to the Origin of Close-In Exoplanets

(21 June 2016)

K2-33 b, shown in this illustration, is one of the youngest exoplanets detected to date. It makes a complete orbit around its star in about five days. These two characteristics combined provide exciting new directions for planet-formation theories. K2-33b could have formed on a farther out orbit and quickly migrated inward. Alternatively, it could have formed in situ, or in place. Image credit: NASA/JPL-Caltech

A team of astronomers has confirmed the existence of a young planet, only 11 million years old, that orbits very close to its star (at 0.05 AU), with an orbital period of 5.4 days. Approximately 5 times the size of the Earth, the new planet is a “super-Neptune” and the youngest such planet known. The discovery lends unique insights into the origin of planetary system architectures.
An enduring puzzle about exoplanets is their prevalence at orbital distances much closer to their central stars than the planets in our own Solar System. How did they get there? One scenario holds that they were born and bred in the hot inner disk close to the star. Other scenarios propose that the close-in planet population originated in cooler climes, at distances beyond the orbit of the Earth, and migrated inward to where they now reside. Their migration may have been driven by interactions with either the natal disk, with other planets in the same planetary system, or with more distant stars.

Observations with ARCoIRIS, the new infrared spectrograph on the 4-m Blanco telescope at the Cerro Tololo Inter-American Observatory (CTIO), played a critical role in measuring the size of the planet. “Because the flux decrement measured during a transit constrains the ratio of the planet and stellar radii, a good measurement of the stellar radius is needed to infer the planet’s radius. The ARCoIRIS spectrum measures the stellar luminosity and, thereby, the stellar radius,” explained NOAO astronomer David James, a coauthor on the study.

Read more in NOAO Press Release 16-02


The Cerro Tololo Inter-American Observatory (CTIO) is a complex of astronomical telescopes and instruments located at 30.169 S, 70.804 W, approximately 80 km to the East of La Serena, Chile, at an altitude of 2200 meters.  CTIO headquarters are located in La Serena, Chile, about 300 miles north of Santiago.

The CTIO complex is part of the U.S. National Optical Astronomy Observatory (NOAO), along with the Kitt Peak National Observatory (KPNO) in Tucson, Arizona.  NOAO is operated by the Association of Universities for Research in Astronomy (AURA) under cooperative agreement with the National Science Foundation (NSF).  CTIO, as part of the AURA Observatory in Chile, operates in Chile under Chilean law, through an Agreement with the University of Chile and with the auspices of the Ministry of Foreign Affairs of Chile.

The principal telescopes on site are the 4-m Victor M. Blanco Telescope and the 4.1-m Southern Astrophysical Research (SOAR) telescope.  One of the two 8-m telescopes comprising the Gemini Observatory is co-located with CTIO on AURA property in Chile, together with more than 10 other telescopes and astronomical projects.