Misplaced Pages

HIP 13044 is a red horizontal-branch star about 2,300 light years (700 pc) from Earth in the constellation Fornax. The star is part of the Helmi stream, a former dwarf galaxy that merged with the Milky Way between six and nine billion years ago. As a result, HIP 13044 circles the Galactic Center at a highly irregular orbit with respect to the galactic plane. HIP 13044 is slightly less massive than the Sun, but is approximately seven times its size. The star, which is estimated to be at least nine billion years old, has passed the red-giant phase. The relatively fast rotation of the star may be due to having engulfed one or more planets during the red-giant phase.

Observational history

A science team from the Max Planck Institute for Astronomy first observed HIP 13044 using Fiber-fed Extended Range Optical Spectrograph (FEROS) at the European Southern Observatory's La Silla Observatory in Chile. The first follow-up led to the collection of 36 radial velocity measurements taken between September 2009 and July 2010.

The team also used photometric data that had been passively collected by and publicly released into the archive of the SuperWASP collaboration, which had been observing the region where the star was located. In this data, HIP 13044 was found to oscillate; the signal was blocked roughly every sixteen days. Analysis of the SuperWASP and FEROS data led to the supposed discovery of the planet HIP 13044 b, although this claim was later refuted.

Characteristics

HIP 13044 is an F-type star located approximately 701 parsecs (2,286 light years) from Earth in the Helmi stream—a group of low-metallicity stars moving with large velocities relative to the Sun. The star follows an eccentric galactic orbit, with a distance from the galactic center ranging from 7 to 16 kiloparsecs. The orbit does not lie in the galactic plane, and can reach distances as high as 13 kpc above it. This indicates that it once was part of a satellite galaxy of the Milky Way that was disrupted 6–9 billion years ago. The star itself is estimated to be at least nine billion years old.

HIP 13044 is fairly evolved star fusing helium in its core, and has therefore already passed the red-giant phase of its evolution. It lies near the blue end of the red horizontal branch bordering the instability strip. Its surface temperature is about 6025 K and its radius is approximately 6.7 solar radii. HIP 13044's mass is estimated to be 0.8 solar masses. Having a rotation period of 5–6 days, HIP 13044 is a fast-rotating star for its type. It is possible that this is because it has swallowed planets during its red-giant phase.

HIP 13044 has an apparent magnitude of 9.94 and cannot be seen with the unaided eye.

Claims of a planetary system

In 2010, it was announced that a giant planet in a 16.2-day orbit had been discovered by the radial velocity measurements. This would have had implications for planet formation in metal-poor systems and survival of planets being engulfed by expanded giant stars. Subsequent analysis of the data revealed problems with the detection: for example an erroneous barycentric correction had been applied (the same error had also led to claims of planets around HIP 11952 that were subsequently refuted). After applying the corrections, there is no evidence for a planet orbiting the star.

References

1. ^ Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
2. ^ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
3. ^ Setiawan, Johny; et al. (2010). "A Giant Planet Around a Metal-poor Star of Extragalactic Origin". Science. 330 (6011): 1642–1644. arXiv:1011.6376. Bibcode:2010Sci...330.1642S. doi:10.1126/science.1193342. PMID 21097905. S2CID 657925.
4. "HIP 13044". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2010-11-19.
5. ^ Than, Ker (2010-11-18). "New Planet Discovered: First Spotted Outside Our Galaxy". NationalGeographic.com. National Geographic Society. Archived from the original on November 20, 2010. Retrieved 2010-11-19.
6. ^ Klement, R.; Setiawan, J.; Thomas Henning; Hans-Walter Rix; Boyke Rochau; Jens Rodmann; Tim Schulze-Hartung; MPIA Heidelberg; ESTEC (2011). "The visitor from an ancient galaxy: A planetary companion around an old, metal-poor red horizontal branch star". The Astrophysics of Planetary Systems: Formation, Structure, and Dynamical Evolution. IAU Symposium. Vol. 276. Proceedings of the International Astronomical Union. pp. 121–125. arXiv:1011.4938. Bibcode:2011IAUS..276..121K. doi:10.1017/S1743921311020059.
7. ^ "Notes for Planet HIP 13044 b". Extrasolar Planets Encyclopaedia. Retrieved 2010-11-22.
8. Jones, M. I.; Jenkins, J. S. (2014). "No evidence of the planet orbiting the extremely metal-poor extragalactic star HIP 13044". Astronomy & Astrophysics. 562: id.A129. arXiv:1401.0517. Bibcode:2014A&A...562A.129J. doi:10.1051/0004-6361/201322132. S2CID 55365608.

v t e Constellation of Fornax
List of stars in Fornax Fornax in Chinese astronomy Chandra Deep Field South Hubble Legacy Field
Stars	Bayer α (Dalim) β γ γ δ ε ζ η η η ι ι κ λ λ μ ν π ρ σ τ υ φ χ χ χ ψ ω Variable R TZ UZ HR 683 858 HD 15337 20781 20782 20868 (Intan) Other 2MASS J02431371−2453298 HIP 13044 LP 944-20 UDF 2457 WASP-72 (Diya)
Exoplanets HD 16417 b HD 20781 b c d e HD 20782 b HD 20868 b (Baiduri) TOI-849 b
Star clusters NGC 1049
Nebulae NGC 1360
Galaxies	NGC 823 824 922 986 1097 1210 1255 1288 1310 1316 1317 1318 1326 1350 1365 1374 1375 1379 1380 1381 1387 1398 1399 1406 1425 1427 Other Fornax Dwarf HUDF-JD2 GS-NDG-9422 IC 335 IC 1993 JADES-GS-z14-0 JADES-GS-z7-01-QU MRC 0316-257 PGC 13809 UDF 423 UDFj-39546284 UDFy-38135539
Galaxy clusters Fornax Cluster
Astronomical events SN 1992bd SN 1999eu SN 2003B
Category

• F-type giants
• Horizontal-branch stars
• Disproven exoplanets
• Fornax
• Durchmusterung objects
• Hipparcos objects