Press release: Life on the edge of the Milky Way?
Nr. 127/2014 - 05.06.2014
Göttingen scientists involved in the discovery of two planets – star is 13 light years away
(pug) An international team of astronomers with the involvement of scientists of the University of Göttingen reports two new planets orbiting a very old and nearby star to the Sun. One of the newly-discovered planets could be ripe for life as it orbits at the right distance to the star to allow liquid water on its surface. The results were published online in the journal Monthly Notices of the Royal Astronomical Society.
Discovered at the end of the 19th century and named after the Dutch astronomer who discovered it (Jacobus Kapteyn), Kapteyn’s star is the second fastest moving star in the sky and belongs to the galactic halo, an extended cloud of stars orbiting our galaxy. With a third of the mass of the sun, this red-dwarf can be seen in the southern constellation of Pictor with an amateur telescope. The astronomers used new data from the HARPS spectrometer at the ESO’s La Silla observatory in Chile. Using the Doppler Effect, which shifts the star’s light spectrum depending on its velocity, the scientists can work out some properties of these planets, such as their masses and orbital periods. The study also combined data from two more high-precision spectrometers to secure the detection: HIRES at Keck Observatory and PFS at Magellan/Las Campanas Observatory. “We were surprised to find planets orbiting Kapteyn's star,” explains Anglada-Escudé, from QMUL’s School of Physics and Astronomy. “Previous data showed some moderate excess of variability, so we were looking for very short period planets when the new signals showed up loud and clear.”
Based on the data collected, the planet Kapteyn b might support liquid water as its mass is at least five times that of Earth’s and orbits the star every 48 days. The second planet, Kapteyn c is a massive super-Earth in comparison: its year lasts for 121 days and astronomers think it’s too cold to support liquid water. At the moment, only a few properties of the planets are known: approximate masses, orbital periods, and distances to the star. By measuring the atmosphere of these planets with next-generation instruments, scientists will try to find out whether they can bear water.
Typical planetary systems detected by NASA’s Kepler mission are hundreds of light-years away. In contrast, Kapteyn’s star is the 25th nearest star to the sun and it is only 13 light years away from Earth. What makes this discovery different however, is the peculiar story of the star. Kapteyn’s star was born in a dwarf galaxy absorbed and disrupted by the early Milky Way. Such galactic disruption event put the star in its fast halo orbit. The likely remnant core of the original dwarf galaxy is omega Centauri, an enigmatic globular cluster 16,000 light years from earth which contains hundreds of thousands of similarly old suns. This sets the most likely age of the planets at 11.5 billion years; which is 2.5 times older than Earth and ‘only’ 2 billion years younger than the universe itself (around 13.7 billion years). Dr Anglada-Escude adds: “It does make you wonder what kind of life could have evolved on those planets over such a long time.”
Original publication: Guillem Anglada-Escudé et al.: Two planets around Kapteyn’s star : a cold and a temperate super-Earth orbiting the nearest halo red-dwarf. Monthly Notices of the Royal Astronomical Society, http://mnrasl.oxfordjournals.org/, Doi: 10.1093/mnrasl/slu076.
Contacts:
Prof. Dr. Ansgar Reiners
Georg-August University Göttingen
Faculty of Physics – Institute of Astrophysics
Friedrich-Hund-Platz 1, 37077 Göttingen
Phone +49 551 39-13825
Email: areiners@astro.physik.uni-goettingen.de
Web: www.astro.physik.uni-goettingen.de
Prof. Dr. Stefan Dreizler
Phone +49 551 39-5041
Email: dreizler@astro.physik.uni-goettingen.de
Dr. Mathias Zechmeister
Phone +49 551 39-9988
Email: zechmeister@astro.physik.uni-goettingen.de