Zeta Leporis

Zeta Leporis, Latinized from ζ Leporis, is a star approximately 70.5 light-years (21.6 parsecs) away in the southern constellation of Lepus. It has an apparent visual magnitude of 3.5,[2] which is bright enough to be seen with the naked eye. In 2001, an asteroid belt was confirmed to orbit the star.

Zeta Leporis
Location of ζ Leporis (circled) near the center
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Lepus
Right ascension  05h 46m 57.34096s[1]
Declination −14° 49′ 19.0199″[1]
Apparent magnitude (V) 3.524[2]
Characteristics
Spectral type A2 IV-V(n)[3]
U−B color index +0.113[2]
B−V color index +0.114[2]
Astrometry
Radial velocity (Rv)20.0[4]–24.7[5] km/s
Proper motion (μ) RA: -14.54[1] mas/yr
Dec.: -1.07[1] mas/yr
Parallax (π)46.28 ± 0.16[1] mas
Distance70.5 ± 0.2 ly
(21.61 ± 0.07 pc)
Absolute magnitude (MV)+1.88[6]
Details
Mass1.46[7] M☉
Radius1.5[8] R☉
Luminosity14[9] L☉
Surface gravity (log g)4.41[9] cgs
Temperature9,772[10] K
Metallicity [Fe/H]–0.76[3] dex
Rotational velocity (v sin i)245[8] km/s
Age231+126
−181[10] Myr
Other designations
ζ Lep, 14 Leporis, BD–14° 1232, FK5 219, GCTP 1326, Gl 217.1, HD 38678, HIP 27288, HR 1998, SAO 150801, Wolf 9190.[11]
Database references
SIMBADdata
ARICNSdata

Stellar components

Zeta Leporis has a stellar classification of A2 IV-V(n),[3] suggesting that it is in a transitional stage between an A-type main-sequence star and a subgiant. The (n) suffix indicates that the absorption lines in the star's spectrum appear nebulous because it is spinning rapidly, causing the lines to broaden because of the Doppler effect. The projected rotational velocity is 245 km/s,[8] giving a lower limit on the star's actual equatorial azimuthal velocity.

The star has about 1.46 times the mass of the Sun,[7] along with 1.5 times the radius,[8] and 14 times the luminosity.[9] The abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is only 17% of the abundance in the Sun.[3] The star appears to be a very young, probably around 231 million years in age, but the margin of error spans 50–347 million years old.[10]

Asteroid belt
A size comparison of the asteroid belt of the Solar System (top) and the Zeta Leporis asteroid belt (bottom).

In 1983, based on radiation in the infrared portion of the electromagnetic spectrum, the InfraRed Astronomical Satellite was used to identify dust orbiting this star. This debris disk is constrained to a diameter of 12.2 AU.[12]

By 2001, the Long Wavelength Spectrometer at the Keck Observatory on Mauna Kea, Hawaii, was used more accurately to constrain the radius of the dust. It was found to lie within a 5.4 AU radius.[12] The temperature of the dust was estimated as about 340 K. Based on heating from the star, this could place the grains as close as 2.5 AU from Zeta Leporis.[12]

It is now believed that the dust is coming from a massive asteroid belt in orbit around Zeta Leporis, making it the first extra-solar asteroid belt to be discovered. The estimated mass of the belt is about 200 times the total mass in the Solar System's asteroid belt, or 4×1023 kg. For comparison, this is more than half the total mass of the Moon. Astronomers Christine Chen and professor Michael Jura found that the dust contained within this belt should have fallen into the star within 20000 years, a time period much shorter than Zeta Leporis's estimated age, suggesting that some mechanism must be replenishing the belt.[12] The belt's age is estimated to be 3×108 years.

The Zeta Leporis planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
Asteroid belt 2.5–6.1 AU — —

Solar encounter

Bobylev's calculations from 2010 suggest that this star passed as close as 1.28 parsecs (4.17 light-years) from the Sun about 861,000 years ago.[5] García-Sánchez 2001 suggested that the star passed 1.64 parsecs (5.34 light-years) from the Sun about 1 million years ago.[4]

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See also

References
  1. van Leeuwen, F. (November 2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.
  2. Gutierrez-Moreno, Adelina; et al. (1966), "A System of photometric standards", Publications of the Department of Astronomy University of Chile, Publicaciones Universidad de Chile, Department de Astronomy, 1: 1–17, Bibcode:1966PDAUC...1....1G
  3. Gray, R. O.; et al. (July 2006), "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample", The Astronomical Journal, 132 (1): 161–170, arXiv:astro-ph/0603770, Bibcode:2006AJ....132..161G, doi:10.1086/504637
  4. 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.
  5. Bobylev, Vadim V. (March 2010). "Searching for Stars Closely Encountering with the Solar System". Astronomy Letters. 36 (3): 220–226. arXiv:1003.2160. Bibcode:2010AstL...36..220B. doi:10.1134/S1063773710030060.
  6. 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.
  7. Shaya, Ed J.; Olling, Rob P. (January 2011), "Very Wide Binaries and Other Comoving Stellar Companions: A Bayesian Analysis of the Hipparcos Catalogue", The Astrophysical Journal Supplement, 192 (1): 2, arXiv:1007.0425, Bibcode:2011ApJS..192....2S, doi:10.1088/0067-0049/192/1/2
  8. Akeson, R. L.; et al. (February 2009), "Dust in the inner regions of debris disks around a stars", The Astrophysical Journal, 691 (2): 1896–1908, arXiv:0810.3701, Bibcode:2009ApJ...691.1896A, doi:10.1088/0004-637X/691/2/1896
  9. Malagnini, M. L.; Morossi, C. (November 1990), "Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars", Astronomy and Astrophysics Supplement Series, 85 (3): 1015–1019, Bibcode:1990A&AS...85.1015M
  10. Song, Inseok; et al. (February 2001), "Ages of A-Type Vega-like Stars from uvbyβ Photometry", The Astrophysical Journal, 546 (1): 352–357, arXiv:astro-ph/0010102, Bibcode:2001ApJ...546..352S, doi:10.1086/318269
  11. "Gliese 217.1". SIMBAD Astronomical Object Database. Centre de Données astronomiques de Strasbourg. Retrieved 2010-03-19.
  12. Morledge, Paul (November 2001). "Tightening a Star's Belt". Astronomy. Kalmbach Publishing. 29 (11): 26. ISSN 0091-6358.

Further reading
  • Cote J (1987). "B and A type stars with unexpectedly large colour excesses at IRAS wavelengths". Astronomy and Astrophysics. 181 (1): 77–84. Bibcode:1987A&A...181...77C.
  • Aumann H. H.; Probst R. G. (1991). "Search for Vega-like nearby stars with 12 micron excess". Astrophysical Journal. 368: 264–271. Bibcode:1991ApJ...368..264A. doi:10.1086/169690.
  • Chen C. H.; Jura M. (2001). "A Possible Massive Asteroid Belt around zeta Leporis". Astrophysical Journal. 560 (2): L171. arXiv:astro-ph/0109216. Bibcode:2001ApJ...560L.171C. doi:10.1086/324057.
  • M. M. Moerchen; C. M. Telesco; C. Packham; T. J. J. Kehoe (2006). "Mid-infrared resolution of a 3 AU-radius debris disk around Zeta Leporis". Astrophysical Journal Letters. 655 (2): L109. arXiv:astro-ph/0612550. Bibcode:2007ApJ...655L.109M. doi:10.1086/511955.
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