25 Orionis

From Wikipedia, the free encyclopedia
Jump to: navigation, search
25 Orionis, Ψ1 Ori
25 Orionis location.png
25 Orionis is located roughly between δ Ori and γ Ori.
Observation data
Epoch J2000      Equinox J2000
Constellation Orion
Right ascension 05h 24m 44.8265s[1]
Declination 01° 50′ 47.201″[1]
Apparent magnitude (V) 4.873
Spectral type B1Vpe[1]
U−B color index -0.92[2]
B−V color index -0.20[2]
Radial velocity (Rv) 19.3[1] km/s
Proper motion (μ) RA: 0.12[1] mas/yr
Dec.: -0.60[1] mas/yr
Parallax (π) 2.94 ± 0.87[3] mas
Distance approx. 1,100 ly
(approx. 300 pc)
Mass 10.5[4] M
Radius 6.4[5] R
Luminosity 10,500[4] L
Surface gravity (log g) 4.0[5] cgs
Temperature 24,661 ± 339[5] K
Rotational velocity (v sin i) 316[6] km/s
Age ~100[4] Myr
Other designations
Ψ1 Ori, 25 Ori, HR 1789, BD +01° 1005, HD 35439, FK5 2406, HIP 25302, SAO 112734, GC 6660, CCDM J05247+0150A, AAVSO 0519+01
Database references

25 Orionis, less commonly known by its Bayer designation Psi1 Orionis (Ψ1 Orionis, Ψ1 Ori) is a fifth-magnitude star in the constellation Orion. Its kinematics place it among a dense cluster of almost 200 low-mass pre-main-sequence stars in the Orion OB1a subassociation known as the 25 Orionis group.[7]


Like the star Pleione in the Pleiades open cluster, 25 Ori is a Be star with a gaseous circumstellar disk. The SIMBAD astronomical database lists its spectral class as B1Vpe.[1] The suffix "pe" refers to "Emission lines with peculiarity", a classification typical of many Be stars whose peculiar emissions come from the gaseous equatorial disks formed of material ejected from the star.

25 Orionis is a fast rotator, clocking a rotational velocity of 316 km/s, significantly faster than Achernar's speed of 251 km/s in the constellation Eridanus.[6][8] Having a radius of 6 R, the star rotates on its axis roughly once every 23 hours. With a mass in excess of 10 M, the star is expected to explode as a supernova.[4]

See also[edit]


  1. ^ a b c d e f g "SIMBAD query result:* 25 Ori -- Be Star". Centre de Données astronomiques de Strasbourg. Retrieved 2010-11-07. 
  2. ^ a b Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars" (PDF). Communications of the Lunar and Planetary Laboratory. 4 (Part 1): 99–110. Bibcode:1966CoLPL...4...99J. 
  3. ^ Perryman, M. A. C.; et al. (1997), "The Hipparcos Catalogue", Astronomy & Astrophysics, 323: L49–L52, Bibcode:1997A&A...323L..49P 
  4. ^ a b c d Kaler, James B., "25 ORI (25 Orionis)", Stars, University of Illinois, retrieved 2010-11-07 
  5. ^ a b c Underhill, A. B.; et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society, 189: 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601 
  6. ^ a b "Bright Star Catalogue (Hoffleit+, 1991)", VizieR (5th Revised ed.), Centre de Données astronomiques de Strasbourg, retrieved 2010-11-07 
  7. ^ Briceño, César; et al. (June 2007). "25 Orionis: A Kinematically Distinct 10 Myr Old Group in Orion OB1a" (PDF). The Astronomical Journal. 661 (2): 1119–1128. arXiv:astro-ph/0701710free to read. Bibcode:2007ApJ...661.1119B. doi:10.1086/513087. Retrieved 2010-11-07. 
  8. ^ "Bright Star Catalogue (Hoffleit+, 1991)". VizieR (5th Revised ed.). Centre de Données astronomiques de Strasbourg. Retrieved 2010-11-08. 

External links[edit]

Coordinates: Sky map 05h 24m 44.80s, +01° 50′ 47.0″