Astronomy:8 Ursae Minoris
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| Constellation | Ursa Minor |
| Right ascension | 14h 56m 48.35230s[1] |
| Declination | +74° 54′ 03.3212″[1] |
| Apparent magnitude (V) | 6.835[2] |
| Characteristics | |
| Evolutionary stage | Red clump[3] |
| Spectral type | G8III[4] |
| Astrometry | |
| Radial velocity (Rv) | −9.55[1] km/s |
| Proper motion (μ) | RA: +13.139[1] mas/yr Dec.: +3.578[1] mas/yr |
| Parallax (π) | 6.1278 ± 0.0142[1] mas |
| Distance | 532 ± 1 ly (163.2 ± 0.4 pc) |
| Absolute magnitude (MV) | +0.82[5] |
| Details | |
| Mass | 1.51±0.06[3] M☉ |
| Radius | 10.73±0.14[3] R☉ |
| Luminosity | 52.9±5.9[3] L☉ |
| Surface gravity (log g) | 2.53[1] cgs |
| Temperature | 4,847±100[3] K |
| Metallicity [Fe/H] | −0.03±0.02[6] dex |
| Rotation | 100–200 d[3] |
| Age | 377[1] Myr |
| Other designations | |
| Database references | |
| SIMBAD | data |
8 Ursae Minoris is a 7th-magnitude red clump star in Ursa Minor. The star is unusually rich in lithium, with an abundance of A = 2.0±0.2 dex.[8][9][3]
In the 2019 NameExoWorlds competition, the star was assigned to contestants in South Korea . It was named Baekdu after Paektu Mountain, the tallest mountain in North Korea.[10][11]
Planetary system
One exoplanet was discovered in 2015 by the Bohyunsan Optical Astronomy Observatory.[12] It has a tight 93-day orbit at a distance of about 0.5 AU, which is unusually close for a giant host star — it should have been consumed during a previous expansion to 0.7 AU.[13][14] It is officially named Halla after Hallasan, the tallest mountain in South Korea.[10][14] There is also a stellar activity cycle of 65 days, and possibly a second companion orbiting at a distance of at least 5 AU.[3]
| Companion (in order from star) |
Mass | Semimajor axis (AU) |
Orbital period (days) |
Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b / Halla | ≥ 1.65±0.06 MJ | 0.462±0.006 | 93.31±0.06 | 0.062±0.18 | — | — |
A 2023 study suggests that 8 Ursae Minoris was initially a binary star with star masses of 1.23 and 0.86 M☉. When the heavier star reached the end of the main sequence about 4.2–5.6 Gyr, it expanded until it dumped all of its mass onto the secondary and became a helium white dwarf. The other star eventually engulfed this white dwarf at around 8.6 Gyr, causing helium burning to start prematurely and forming the star that we know today. The planet may have survived the episode as a former circumbinary planet, or it may have formed from material ejected during the stellar merger. 8 Ursae Minoris is now in the red clump stage, and the planet will eventually be engulfed once it reaches the asymptotic giant branch.[3]
References
- ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940 Gaia DR3 record for this source at VizieR.
- ↑ Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P. et al. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: L27–L30. ISSN 0004-6361. Bibcode: 2000A&A...355L..27H.
- ↑ 3.0 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 Hon, Marc; Huber, Daniel; Rui, Nicholas Z.; Fuller, Jim; Veras, Dimitri; Kuszlewicz, James S.; Kochukhov, Oleg; Stokholm, Amalie et al. (2023). "A close-in giant planet escapes engulfment by its star". Nature 618 (7967): 917–920. doi:10.1038/s41586-023-06029-0. PMID 37380688. Bibcode: 2023Natur.618..917H.
- ↑ Abt, Helmut A. (2004). "Spectral Classification of Stars in A Supplement to the Bright Star Catalogue". The Astrophysical Journal Supplement Series 155 (1): 175–177. doi:10.1086/423803. Bibcode: 2004ApJS..155..175A.
- ↑ Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A.
- ↑ Goda, Shohei; Matsuo, Taro (2019). "Multiple Populations of Extrasolar Gas Giants". The Astrophysical Journal 876 (1): 23. doi:10.3847/1538-4357/ab0f9c. Bibcode: 2019ApJ...876...23G.
- ↑ "* 8 UMi". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=%2A+8+UMi.
- ↑ Kumar, Yerra Bharat; Reddy, Bacham E.; Lambert, David L. (20 March 2011). "Origin of Lithium Enrichment in K Giants". The Astrophysical Journal 730 (1): L12. doi:10.1088/2041-8205/730/1/L12. Bibcode: 2011ApJ...730L..12K.
- ↑ Gao, Jun; Zhu, Chunhua; Yu, Jinlong; Liu, Helei; Lu, Xizhen; Shi, Jianrong; Lü, Guoliang (December 2022). "Li-rich and super Li-rich giants produced by element diffusion". Astronomy & Astrophysics 668: A126. doi:10.1051/0004-6361/202243871. Bibcode: 2022A&A...668A.126G.
- ↑ 10.0 10.1 "Approved names" (in en). http://www.nameexoworlds.iau.org/final-results.
- ↑ "International Astronomical Union | IAU". https://www.iau.org/news/pressreleases/detail/iau1912/.
- ↑ Lee, B.-C.; Park, M.-G.; Lee, S.-M.; Jeong, G.; Oh, H.-I.; Han, I.; Lee, J. W.; Lee, C.-U. et al. (December 2015). "Search for exoplanet around northern circumpolar stars: Four planets around HD 11755, HD 12648, HD 24064, and 8 Ursae Minoris⋆". Astronomy & Astrophysics 584: A79. doi:10.1051/0004-6361/201527076. Bibcode: 2015A&A...584A..79L.
- ↑ Timmer, John (28 June 2023). "Planet that shouldn't exist found" (in en-us). Ars Technica. https://arstechnica.com/science/2023/06/planet-that-should-have-been-swallowed-by-its-star-somehow-still-orbits/.
- ↑ 14.0 14.1 Strickland, Ashley (2023-06-28). "Scientists spot a planet that shouldn't exist" (in en). https://www.cnn.com/2023/06/28/world/exoplanet-halla-survives-star-outburst-scn/index.html.
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