Iota Ursae Majoris
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 Location of ι Ursae Majoris (circled) |
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| Observation data Epoch J2000 Equinox J2000 |
|
|---|---|
| Constellation | Ursa Major |
| Right ascension | 08h 59m 12.45362s[1] |
| Declination | +48° 02′ 30.5741″[1] |
| Apparent magnitude (V) | 3.14[2]/10.1/10.3 |
| Characteristics | |
| Spectral type | A7 IV[3] + dM1 J |
| U−B color index | +0.08[2] |
| B−V color index | +0.19[2] |
| Variable type | Suspected |
| Astrometry | |
| Radial velocity (Rv) | +9.0[4] km/s |
| Proper motion (μ) | RA: -441.29[1] mas/yr Dec.: -215.32[1] mas/yr |
| Parallax (π) | 68.92 ± 0.16[1] mas |
| Distance | 47.3 ± 0.1 ly (14.51 ± 0.03 pc) |
| Details | |
| ι UMa A | |
| Rotational velocity (v sin i) | 154[5] km/s |
| Age | 620[6] Myr |
| Other designations | |
Iota Ursae Majoris (ι UMa, ι Ursae Majoris) is a star system in the northern circumpolar constellation of Ursa Major. It has an apparent visual magnitude of 3.14,[2] making it visible to the naked eye and placing it among the brighter members of this constellation. Based upon parallax measurements, it is located at a distance of 47.3 light-years (14.5 parsecs) from Earth. It has the traditional names Talitha, Talitha Borealis and Alphikra Borealis, and was also dubbed Dnoces ("Second," backwards) after Edward H. White II, an Apollo 1 astronaut. The name was invented by his fellow astronaut Gus Grissom as a practical joke.[8]
The Iota Ursae Majoris system is composed of two binary stars. The brightest component is a white A-type subgiant. It is a spectroscopic binary whose components have an orbital period of 4028 days. The companion binary is composed of the 9th magnitude and 10th magnitude stars. These two stars orbit around each other with a period of 39.7 years, and are separated by roughly 0.7 arcseconds, or at least 10 AU. This pair may be the source of the X-ray emission detected from this system.[9]
The two binary systems orbit around each other once every 818 years. The apparent separation between the two binaries is rapidly decreasing as they follow their orbits. In 1841 when the B component was first discovered, they had a separation of 10.7 arcseconds, or at least 156 AU. By 1971 their separation had decreased to 4.5 arcseconds, or at least 66 AU. This system appears to be dynamically unstable with a high likelihood and may become disrupted on a time scale on the order of 105 years.[10]
[edit] See also
[edit] References
- ^ a b c d e van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics 474 (2): 653–664. Bibcode 2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
- ^ a b c d Johnson, H. L. et al (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory 4 (99). Bibcode 1966CoLPL...4...99J.
- ^ Morgan, W. W.; Abt, H. A. (February 1972), "The spectral classification of the F stars of intermediate luminosity", Astronomical Journal 77: 35–37, Bibcode 1972AJ.....77...35M, doi:10.1086/111242
- ^ Evans, D. S. (June 20–24, 1966), Batten, Alan Henry; Heard, John Frederick, eds., The Revision of the General Catalogue of Radial Velocities, University of Toronto: International Astronomical Union, Bibcode 1967IAUS...30...57E
- ^ Royer, F.; Zorec, J.; Gómez, A. E. (February 2007), "Rotational velocities of A-type stars. III. Velocity distributions", Astronomy and Astrophysics 463 (2): 671–682, Bibcode 2007A&A...463..671R, doi:10.1051/0004-6361:20065224
- ^ Su, K. Y. L. et al. (December 2006), "Debris Disk Evolution around A Stars", The Astrophysical Journal 653 (1): 675-689, Bibcode 2006ApJ...653..675S, doi:10.1086/508649
- ^ "iot UMa -- Spectroscopic binary". SIMBAD Astronomical Object Database. Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=Iota+Ursae+Majoris. Retrieved 2012-02-25.
- ^ "Post-landing Activities", Apollo 15 Lunar Surface Journal, NASA, http://history.nasa.gov/alsj/a15/a15.postland.html. Commentary at 105:11:33.
- ^ De Rosa, R. J. et al. (July 2011), "The Volume-limited A-Star (VAST) survey - I. Companions and the unexpected X-ray detection of B6-A7 stars", Monthly Notices of the Royal Astronomical Society 415 (1): 854–866, Bibcode 2011MNRAS.415..854D, doi:10.1111/j.1365-2966.2011.18765.x
- ^ Zhuchkov, R. Ya.; Orlov, V. V.; Rubinov, A. V. (January 2006), "Dynamical stability of the quadruple systems HD 68255/6/7 and HD 76644", Astronomy Reports 50 (1): 62–67, Bibcode 2006ARep...50...62Z, doi:10.1134/S1063772906010070
[edit] External links
- NightSky Friday: Rotanev, Derf, Navi, and other Backward Star Names – Space.com article
- ARICNS
- Talitha by Professor Jim Kaler.
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