Speedy Mic
 Map of starspots on the surface of Speedy Mic at different rotation phases. The blue circle is the location of a flare observed in October 2006. | |
| Observation data Epoch J2000 Equinox ICRS | |
|---|---|
| Constellation | Microscopium[1] |
| Right ascension | 20h 47m 45.00562s[2] |
| Declination | −36° 35′ 40.7698″[2] |
| Apparent magnitude (V) | 9.39[3] |
| Characteristics | |
| Spectral type | K3Ve[3] |
| Variable type | BY Dra[4] |
| Astrometry | |
| Radial velocity (Rv) | −5.64±2.03[2] km/s |
| Proper motion (μ) | RA: 18.735 mas/yr[2] Dec.: −81.712 mas/yr[2] |
| Parallax (π) | 19.5983±0.5745 mas[2] |
| Distance | 166 ± 5 ly (51 ± 1 pc) |
| Absolute magnitude (MV) | +6.22[1] |
| Details | |
| Mass | 0.82±0.08[5] M☉ |
| Radius | 1.06±0.04[5] R☉ |
| Luminosity | 0.60[6] L☉ |
| Surface gravity (log g) | 4.28[6] cgs |
| Temperature | 4750±50[7] K |
| Metallicity [Fe/H] | −1.49[8] dex |
| Rotation | 0.380±0.004 days[9] |
| Rotational velocity (v sin i) | 135[10] km/s |
| Age | 33±5[7] Myr |
| Other designations | |
| Speedy Mic, BO Mic, CD−37 13926, CPD−37 8883, HD 197890, HIP 102626, SAO 212437, PPM 300614, TIC 389423271, TYC 7469-997-1, GSC 07469-00997 | |
| Database references | |
| SIMBAD | data |
Speedy Mic is a star in the constellation Microscopium located about 170 light-years (52 parsecs; 11 million astronomical units) from the Sun. Its name refers to its very rapid rotation; it also has the variable star designation BO Microscopii (BO Mic). The projected rotational velocity at the equator of this star is about 135 km/s (84 mi/s), which, with an estimated inclination of 70° to the line of sight from the Earth, means it completes a rotation every 0.380 ± 0.004 days (9.120 ± 0.096 hours).[10]
The star was discovered to be active and a rapid rotator in a 1990 all-sky extreme ultraviolet survey by the ROSAT space telescope, and was given the name Speedy Mic; Mic is the abbreviation for Microscopium.[11] The name has been commonly used since and was officially approved by the IAU Working Group on Star Names on 9 May 2026.[12]
The photosphere of this star shows a high level of magnetic activity, with multiple star spots and prominences observed at the same time. As many as 25 prominences have been observed simultaneously, extending outward as far as 3.6 times the radius of the star. BO Mic is a flare star that undergoes sudden increases in X-ray and ultraviolet emissions. These events can emit a hundred times more energy than large solar flares.[10] Speedy Mic is one of the most active stars in the vicinity of the Sun.[5]
References
[edit]- 1 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. XHIP record for this object at VizieR.
- 1 2 3 4 5 6 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
- 1 2 Torres, C. A. O.; et al. (December 2006), "Search for associations containing young stars (SACY). I. Sample and searching method", Astronomy and Astrophysics, 460 (3): 695–708, arXiv:astro-ph/0609258, Bibcode:2006A&A...460..695T, doi:10.1051/0004-6361:20065602, S2CID 16080025
- ↑ Samus', N. N.; Kazarovets, E. V.; Durlevich, O. V.; Kireeva, N. N.; Pastukhova, E. N. (2017). "General catalogue of variable stars: Version GCVS 5.1". Astronomy Reports. 61 (1): 80. Bibcode:2017ARep...61...80S. doi:10.1134/S1063772917010085.
- 1 2 3 Dunstone, N. J.; et al. (January 2006), "The coronal structure of Speedy Mic - I. A densely packed prominence system beyond corotation", Monthly Notices of the Royal Astronomical Society, 365 (2): 530–538, arXiv:astro-ph/0510739, Bibcode:2006MNRAS.365..530D, doi:10.1111/j.1365-2966.2005.09729.x, S2CID 11048210
- 1 2 Ayres, Thomas (2023). "In the Trenches of the Solar-Stellar Connection. VII. Wilson-Bappu 2022". The Astrophysical Journal Supplement Series. 266 (1): 6. Bibcode:2023ApJS..266....6A. doi:10.3847/1538-4365/acb535.
- 1 2 Wolter, U.; et al. (May 2005), "Doppler imaging of Speedy Mic using the VLT. Fast spot evolution on a young K-dwarf star", Astronomy and Astrophysics, 435 (1): 261–273, arXiv:astro-ph/0504104, Bibcode:2005A&A...435..261W, doi:10.1051/0004-6361:20042239
- ↑ Holmberg, J.; Nordström, B.; Andersen, J. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID 118577511
- 1 2 Cutispoto, G.; Kurster, M.; Pagano, I.; Rodono, M. (January 1997). "UBV(RI)c Photometry of the Rapidly Rotating K-Type Star HD197890 = "Speedy Mic"". Information Bulletin on Variable Stars. 4419: 1. Bibcode:1997IBVS.4419....1C.
- 1 2 3 Wolter, U.; et al. (January 2008), "Doppler imaging an X-ray flare on the ultrafast rotator BO Mic. A contemporaneous multiwavelength study using XMM-Newton and VLT", Astronomy and Astrophysics, 478 (1): L11–L14, arXiv:0712.0899, Bibcode:2008A&A...478L..11W, doi:10.1051/0004-6361:20078838, S2CID 62827486
- ↑ Bromage, G. E.; Kellett, B. J.; et al. (1992). Speedy Mic: A Young; Nearby; Extremely Fast Rotating K Star Discovered by the ROSAT/WFC EUV Survey. Cool stars, stellar systems, and the sun. Proceedings of the 7th Cambridge Workshop, ASP Conference Series. Vol. 26. p. 80. Bibcode:1992ASPC...26...80B.
- ↑ "IAU Catalog of Star Names". Retrieved 18 May 2026.
