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Kapteyn's Star
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Title: Two planets around Kapteyn's star : a cold and a temperate super-Earth orbiting the nearest halo red-dwarf
Author: Guillem Anglada-Escudé, Pamela Arriagada, Mikko Tuomi, Mathias Zechmeister, James S. Jenkins, Aviv Ofir, Stefan Dreizler, Enrico Gerlach, Chris J. Marvin, Ansgar Reiners, Sandra V. Jeffers, R. Paul Butler, Steven S. Vogt, Pedro J. Amado, Cristina Rodríguez-López, Zaira M. Berdiñas, Julian Morin, Jeff D. Crane, Stephen A. Shectman, Ian B. Thompson, Mateo Díaz, Eugenio Rivera, Luis F. Sarmiento, Hugh R.A. Jones

Exoplanets of a few Earth masses can be now detected around nearby low-mass stars using Doppler spectroscopy. In this paper, we investigate the radial velocity variations of Kapteyn's star, which is both a sub-dwarf M-star and the nearest halo object to the Sun. The observations comprise archival and new HARPS, HIRES and PFS Doppler measurements. Two Doppler signals are detected at periods of 48 and 120 days using likelihood periodograms and a Bayesian analysis of the data. Using the same techniques, the activity indicies and archival ASAS-3 photometry show evidence for low-level activity periodicities of the order of several hundred days. However, there are no significant correlations with the radial velocity variations on the same time-scales. The inclusion of planetary Keplerian signals in the model results in levels of correlated and excess white noise that are remarkably low compared to younger G, K and M dwarfs. We conclude that Kapteyn's star is most probably orbited by two super-Earth mass planets, one of which is orbiting in its circumstellar habitable zone, becoming the oldest potentially habitable planet known to date. The presence and long-term survival of a planetary system seems a remarkable feat given the peculiar origin and kinematic history of Kapteyn's star. The detection of super-Earth mass planets around halo stars provides important insights into planet-formation processes in the early days of the Milky Way.

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HD 33793
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Oldest Known Potentially Habitable Exoplanet Found

An international team of astronomers, led by Guillem Anglada-Escude from Queen Mary University, reports two new planets orbiting a very old and nearby star to the Sun named Kapteyn's star. One of the newly-discovered planets, Kapteyn b, is potentially habitable as it has the right-size and orbit to support liquid water on its surface. What makes this discovery highly interesting is the peculiar story and age of the star. Kapteyn b is likely over twice the age of Earth and the oldest known potentially habitable planet listed in the Habitable Exoplanets Catalogue.
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Posts: 131433
Date:
Kapteyn's star
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Kapteyn's Star is a class M1 red dwarf about 13 light years from Earth in the southern constellation of Pictor. With a magnitude of nearly 9 it is visible through binoculars or a telescope
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VZ Pictoris
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A dim star just 13 light years from Earth was born in a cluster 17,000 light years away.
Discovered in 1897, Kapteyn's Star is the 25th nearest star system to our sun, but it is no local, says Elizabeth Wylie-de Boer of Mount Stromlo Observatory in Canberra.
The cool star's composition is tricky to study, but astronomers can look at 16 other stars in the same "moving group", all of which orbit the galaxy backwards and are very old. The odd motion marks them as members of the Milky Way's ancient population of halo stars.

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Position (2000): RA 05 11 40.5789, Dec -45 01 06.266

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