An artist's conception of the HIP 11952 system.
Epoch J2000 Equinox J2000
|Right ascension||02h 34m 11.04689s|
|Declination||−12° 23′ 3.4570″|
|Apparent magnitude (V)||9.85|
|Spectral type||F2V-IV[note 1]|
|Apparent magnitude (B)||10.18|
|Apparent magnitude (V)||9.85|
|Apparent magnitude (J)||8.790|
|Apparent magnitude (H)||8.516|
|Apparent magnitude (K)||8.457|
|Radial velocity (Rv)||23.62 km/s|
|Proper motion (μ)||RA: 57.27 mas/yr
Dec.: -187.74 mas/yr
|Parallax (π)||8.93 mas|
|Mass||0.83 ± 0.05 M☉|
|Radius||1.6 ± 0.1 R☉|
|Temperature||6040 ± 210 K|
|Metallicity [Fe/H]||–1.95 ± 0.09[note 2] dex|
|Age||12.8 ± 2.6 Gyr|
HIP 11952 is a star in the Milky Way galaxy, located 375 light-years away from the Sun. While the spectral lines strongly indicate that the star is of spectral type F2V-IV, previous analyses have stated that the star is a G8III giant star and an F0V main-sequence star. Located in the constellation Cetus, the star has a metallicity only 1% that of the Sun, and is the oldest star which has a confirmed planetary system.
The star HIP 11952 has two planets; the more massive outer planet, HIP 11952 b, in a somewhat eccentric orbit of 290 days, and a less massive hot Jupiter, HIP 11952 c, in an eccentric seven-day orbit around its host star. This system contains two defining characteristics: the star is the oldest one confirmed to possess a planetary system, and due to the age of the system, the star has the lowest metallicity of any found with planets orbiting it.[note 3] The chances of a planet forming so early in the Universe's history, with such a small amount of heavy elements with which to form planets, are believed to be remote. In spite of this, the star has an exceptionally high metallicity among those that formed at the same time in the Universe's history.
While the discoverers leave open the possibility of the planets forming billions of years after their host stars, once the Universe had a far greater concentration of heavier elements, they state that the chance of this happening is, according to the authors of the discovery paper, extremely small. In the future, as the host star eventually transforms into a red giant, then dies as a white dwarf, the planets may become stripped of all but their cores, like the planets of the KOI-55 system.
The planets may not, owing to the lack of elements heavier than hydrogen and helium, be an ideal location to extend the search for extraterrestrial life, but would probably be more scientifically valuable as a captured moment of the Universe's earliest history.
(in order from star)
|c||0.78 ± 0.16 MJ||0.07 ± 0.01||6.95 ± 0.01||0.35 ± 0.24||—||—|
|b||2.93 ± 0.42 MJ||0.81 ± 0.02||290 ± 16.2||0.27 ± 0.1||—||—|
Astronomers have recently performed radial velocity monitoring of HIP 11952 on 35 nights over about 150 days, from August 7th 2012 to January 6th 2013, using the newly installed high resolution spectrograph HARPS-N at the 3.58m Telescopio Nazionale Galileo telescope on La Palma Island (Canary Islands) and HARPS at the European Southern Observatory's 3.6m telescope on La Silla (Chile). Following their analysis, they were able to confidently exclude, through non-detection, the presence of the two giant planets with periods of 6.95 ± 0.01 days and 290.0 ± 16. 2 days. They also reasoned that the previously mistaken detections were probably due to instrument measurement errors.
- Staff, Space.com (28 March 2012). "Ancient Alien Planets Shake Up View of Early Universe". Space.com. Space.com. Retrieved March 29, 2012.
- "Basic data : LP 710-89 -- High proper-motion Star". SIMBAD. University of Stratsbourg. 2011. Retrieved March 29, 2012.
- "Planetary companions around the metal-poor star HIP 11952". Astronomy and Astrophysics. March 2012.
- Schneider, Jean (23 March 2012). "Notes for Star HIP 11952". Extrasolar Planets Encyclopedia. Retrieved March 29, 2012.
- Than, Ker (26 March 2012). "Oldest Alien Planets Found—Born at Dawn of Universe". National Geographic Daily News. National Geographic. Retrieved March 29, 2012.
- O'Neill, Ian (27 March 2012). "Most ancient, 'Impossible' Alien Worlds Discovered". Discovery News. Discovery News. Retrieved March 29, 2012.
- Desidera, S; et al. (June 2013). "The GAPS programme with HARPS-N at TNG. II. No giant planets around the metal-poor star HIP 11952". Astronomy and Astrophysics 554: 29–33. arXiv:1302.3093. Bibcode:2013A&A...554A..29D. doi:10.1051/0004-6361/201321155.
- The stellar classification for this star is uncertain; please read the cited paper for more information.
- This measurement indicates the log10 of the relative abundance of iron in the measured star to that of the Sun.
- This star shares this distinction with HIP 13044, which within its margin of error for metallicity has a metallicity range overlapping with that of HIP 11952. See the list of extrasolar planet extremes for more information.