Lalande 21185

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Lalande 21185
Ursa Major constellation map.svg
Locator Dot.gif

The red dot shows the location of Lalande 21185 in Ursa Major.
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Ursa Major
Right ascension 11h 03m 20.194s[1]
Declination +35° 58′ 11.55″[1]
Apparent magnitude (V) 7.47[1]
Characteristics
Spectral type M2V[1]
Apparent magnitude (B) ~9.00[1]
Apparent magnitude (V) ~7.49[1]
Apparent magnitude (R) ~6.6[1]
Apparent magnitude (I) ~5.8[1]
Apparent magnitude (J) 4.203 ±0.242[1]
Apparent magnitude (H) 3.640 ±0.202[1]
Apparent magnitude (K) 3.254 ±0.306[1]
U−B color index 1.13
B−V color index 1.51
Variable type BY[2]
Astrometry
Radial velocity (Rv) -85.0 ±0.9[1] km/s
Proper motion (μ) RA: -580.46 ±0.95[1] mas/yr
Dec.: -4769.95 ±0.53[1] mas/yr
Parallax (π) 392.52[1] ± 0.91[1] mas
Distance 8.32 ly
(2.55 pc)
Absolute magnitude (MV) 10.48[3]
Details
Mass 0.46[4] M☉
Radius 0.46[3] R☉
Surface gravity (log g) 4.8[5]
Luminosity 0.025 L☉
Temperature 3,383[3] K
Metallicity -0.20 Fe/H[5]
Age 5-10 × 109 years
Other designations
BD+36 2147, G 119-052, Gliese 411, HD 95735, HIP 54035, LFT 756, LHS 37, LTT 12960, MCC 594, PLX 2576, SAO 62377, NLTT 26105, NSV 18593, IRAS 11005+3615.[1]
Database references
SIMBAD data

Lalande 21185 is a red dwarf star in the constellation of Ursa Major. Although relatively close by, it is only magnitude 7 in visible light and thus is too dim to see with the unaided eye. The star is visible through a small telescope.

At approximately 8.3 light-years away this star is the fourth closest stellar system to the Sun; only the Alpha Centauri system, Barnard's Star and Wolf 359 are known to be closer. Because of its proximity it is a frequent subject for astronomical surveys and other research and thus is known by numerous other designations. Research papers most commonly use the designations BD+36 2147, Gliese 411, and HD 95735 to refer to this star.[1]

In approximately 19,900 years Lalande 21185 will be at its closest distance of about 4.65 ly (1.43 pc) from the Sun.[6][7] Easy kinematic calculations show that, among currently known stars, only Proxima and Alpha Centauri AB will be closer to the Sun at that moment.[citation needed]

Contents

[edit] History

The celestial coordinates of Lalande 21185 were first published in 1801 by French astronomer Jérôme Lalande of the Paris Observatory in the star catalog, Histoire Céleste Française. The catalog sequence numbers for all of the observed stars, including this one, were added to the original catalog by a later editor in an 1847 republication.[8] Today this star, along with a few others, is still commonly referred to by its Lalande catalog number.[9]

Winneke is reported to have made the first measurement of the star's parallax of .511 arc seconds in 1856 and thus first identifying Lalande 21185 as the second-closest known star to the Sun, after the Alpha Centauri system. Since that time better measurements have placed the star further away but it was the still the second-closest known star system until the discovery of two dim red dwarf stars, Wolf 359 and Barnard's Star, in the early twentieth century using astrophotography.[10]

[edit] Physical properties

Lalande 21185 is a typical type-M red dwarf main sequence star with about 46% of the radius of the Sun and much cooler than the Sun at 3,383 K. It is intrinsically dim with an absolute magnitude of 10.48, emitting most of its energy as infrared radiation.[3] Lalande 21185 is a high proper motion star moving at about 5 arc seconds a year in an orbit perpendicular to the plane of the galaxy. Its mass is estimated to be about 46% of the Sun.[4] The proportion of elements other than hydrogen and helium is estimated based on the ratio of iron to hydrogen in the star when compared to the Sun. The logarithm of this ratio is –0.20, indicating that the proportion of iron is about 10–0.20, or 63% of the Sun. The logarithm of the surface gravity is 4.8.[5]

Lalande 21185 is listed as a BY Draconis type variable star in the General Catalogue of Variable Stars. It is identified by the variable star designation NSV 18593.[2] Several star catalogs, including SIMBAD, also classify it as a flare star. This conclusion is not supported by the primary reference these catalogs all use. The observations made in this reference show that it is rather quiet in comparison to other stars of its variable type.[11]

Lalande 21185 emits X-rays.[12]

[edit] Claims of a planetary system

In 1951 Peter van de Kamp and his student, Sarah Lippincott, claimed the astrometric detection of a planetary system using photographic plates taken with the 24-in refractor telescope at Swarthmore College's Sproul Observatory.[13] In 1960, Sarah Lippincott repeated the 1951 claim of a planetary system, only this time having different parameters. She used the original photographic plates and new plates taken with the same telescope.[14] Photographic plates from this observatory, taken at the same time, were used by Van de Kamp for his erroneous claim of a planetary system for Barnard's Star. The photographic plates made with the Sproul 24-in refractor, and used for these and other studies, were later shown to be flawed.[15] The claims of planetary companions for both stars were refuted in 1974 with astrometric measurements made by George Gatewood of the Allegheny Observatory.[16]

In 1996 the same George Gatewood prominently announced at an AAS meeting[17] and to the popular press[18] the discovery of multiple planets in this system, detected by astrometry. The initial report of a planet was based on a very delicate analysis of the star's position over the years which suggested reflex orbital motion due to one or more companions. Gatewood claimed that such companions would usually appear more than 0.8 arc second from the M dwarf itself. However a paper by Gatewood published only a few years earlier[19] and subsequent searches by others, using coronagraphs and multifilter techniques to reduce the scattered-light problems from the star, have yet to positively identify any such companions[20] and so his claim remains unconfirmed and is now in doubt.

[edit] Refining planetary boundaries

This star's measured radial velocity is so constant that astronomer and planet hunter Geoff Marcy uses it as a perfect example of "normal" M dwarf stability levels.[21] The negative results of this and other surveys do not preclude the presence of a planetary system entirely but they do set an upper boundary on the mass of any planets that might be present. The detection limit by current technology for this star system is a little less than the mass of the planet Jupiter. New Earth- and space-based instruments will certainly lower this limit further and possibly detect any small planets that may be present.

[edit] See also

[edit] References

  1. ^ a b c d e f g h i j k l m n o p q r "SIMBAD query result: HD 95735 -- Flare Star". Centre de Données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-id?Ident=HD+95735. Retrieved 2009-05-29. 
  2. ^ a b "NSV 18593". General Catalogue of Variable Stars, Sternberg Astronomical Institute, Moscow, Russia. http://www.sai.msu.su/groups/cluster/gcvs/cgi-bin/search.cgi?search=NSV+18593. Retrieved 2009-09-09. 
  3. ^ a b c d Johnson, H. M. & Wright, C. D. (November 1983). "Predicted infrared brightness of stars within 25 parsecs of the Sun". Astrophysical Journal Supplement Series (ISSN 0067-0049) (Lockheed Independent Research Program and Lockheed Independent Development Program.) 53: 643–711. Bibcode 1983ApJS...53..643J. doi:10.1086/190905. 
  4. ^ a b "The 100 nearest star systems". Research Consortium on Nearby Stars. January 1, 2009. http://joy.chara.gsu.edu/RECONS/TOP100.posted.htm. Retrieved 2009-09-09. 
  5. ^ a b c Cayrel de Strobel, G., Hauck, B., François, P., Thevenin, F., Friel, E., Mermilliod, M.. "A catalogue of Fe/H determinations - 1991 edition". Astronomy and Astrophysics Supplement Series (ISSN 0365-0138) 95 (2): 273–336. Bibcode 1992A&AS...95..273C. 
  6. ^ García-Sánchez, J.; Weissman, P. R.; Preston, R. A.; Jones, D. L.; Lestrade, J.-F.; Latham, D. W.; Stefanik, R. P.; Paredes, J. M. (2001). "Stellar encounters with the solar system". Astronomy and Astrophysics 379 (2): 634–659. Bibcode 2001A&A...379..634G. doi:10.1051/0004-6361:20011330. 
  7. ^ "Annotations on HD 95735 object". Centre de Données astronomiques de Strasbourg. http://cdsannotations.u-strasbg.fr/annotations/simbadObject/1764001. Retrieved 2010-04-14. 
  8. ^ Baily, F. (1847). A catalogue of those stars in the "Histoire Celeste Française" of J. De Lalande for which tables of reduction to the session define format EPOCH1 = 1800 have been published by Professor Schumacher.. British Association for the Advancement of Scicience, London. Bibcode 1950Lalan1847....0B. http://adsabs.harvard.edu//abs/1950Lalan1847....0B. 
  9. ^ Joseph-Jérôme de Lalande
  10. ^ Russell, H. N. (June 1905). "The parallax of Lalande 21185 and γ Virginis from photographs taken at the Cambridge Observatory". Monthly Notices of the Royal Astronomical Society 65: 787–800. Bibcode 1905MNRAS..65..787R. 
  11. ^ Bopp, B. W.; Noah, P. V.; Klimke, A.; Africano, J. (October 1, 1981). "Discovery and observation of BY Draconis variables". Astrophysical Journal 249 (1): 210–217. Bibcode 1981ApJ...249..210B. doi:10.1086/159277. 
  12. ^ Schmitt JHMM, Fleming TA, Giampapa MS (September 1995). "The X-Ray View of the Low-Mass Stars in the Solar Neighborhood". Ap J. 450 (9): 392–400. Bibcode 1995ApJ...450..392S. doi:10.1086/176149. 
  13. ^ van de Kamp, P. & Lippincott, S. L (April, 1951). "Astrometric study of Lalande 21185.". The Astronomical Journal 56: 49–50. Bibcode 1951AJ.....56...49V. doi:10.1086/106503. 
  14. ^ Lippincott, Sarah Lee (August, 1960). "The Unseen Companion of the Fourth Nearest Star, Lalande 21185". The Astronomical Journal 65: 350. Bibcode 1960AJ.....65..349L. doi:10.1086/108260. 
  15. ^ John L. Hershey (June 1973). "Astrometric analysis of the field of AC +65 6955 from plates taken with the Sproul 24-inch refractor". Astronomical Journal 78 (5): 421–425. Bibcode 1973AJ.....78..421H. doi:10.1086/111436. 
  16. ^ Gatewood, G. (January 1974). "An astrometric study of Lalande 21185". The Astronomical Journal 79 (1): 52. Bibcode 1974AJ.....79...52G. doi:10.1086/111530. 
  17. ^ Gatewood, G. (May, 1996). "Lalande 21185". Bulletin of the American Astronomical Society (American Astronomical Society, 188th AAS Meeting, #40.11;) 28: 885. Bibcode 1996AAS...188.4011G. 
  18. ^ John Wilford (1996-06-12). "Data Seem to Show a Solar System Nearly in the Neighborhood". The New York Times. p. 1. http://www.nytimes.com/1996/06/12/us/data-seem-to-show-a-solar-system-nearly-in-the-neighborhood.html. Retrieved 2009-05-29. 
  19. ^ Gatewood et al.; Stein, John; De Jonge, Joost K.; Persinger, Timothy; Reiland, Thomas; Stephenson, Bruce (September, 1992). "Multichannel astrometric photometer and photographic astrometric studies in the regions of Lalande 21185, BD 56°2966, and HR 4784". The Astronomical Journal 104 (3): 1237–1247. Bibcode 1992AJ....104.1237G. doi:10.1086/116313. 
  20. ^ Henry et al.; Baliunas, Sallie L.; Donahue, Robert A.; Fekel, Francis C.; Soon, Willie (March 1, 2000). "Photometric and Ca II H and K Spectroscopic Variations in Nearby Sun-like Stars with Planets. III". The Astrophysical Journal 531 (1): 415–437. Bibcode 2000ApJ...531..415H. doi:10.1086/308466. http://www.iop.org/EJ/article/0004-637X/531/1/415/50376.web.pdf?request-id=b98eea9d-4dc7-462a-9797-bd06712fd0ad. 
  21. ^ Marcy et al.; Lindsay, Victoria; Wilson, Karen (June, 1987). "Radial velocities of M dwarf stars". Astronomical Society of the Pacific, Publications (ISSN 0004-6280) 99: 490–496. Bibcode 1987PASP...99..490M. doi:10.1086/132010. 

[edit] External links

Coordinates: Sky map 11h 03m 20s, +35° 59′ 12″

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