U Orionis

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U Orionis
Gemini constellation map.svg
Red circle.svg
Location of U Orionis (circled)
Observation data
Epoch J2000.0        Equinox J2000.0
Constellation Orion
Right ascension 05h 55m 49.17076s [1]
Declination +20° 10′ 30.6779″ [1]
Apparent magnitude  (V)4.8 - 13.0 [2]
Characteristics
Spectral type M6e-M9.5e [2]
B−V color index +2.07 [3]
Variable type Mira [2]
Astrometry
Parallax (π)3.4924 ± 0.1820  mas [1]
Distance 930 ± 50  ly
(290 ± 10  pc)
Details
Mass 0.88 [4]   M☉
Radius 370±96 [5]   R☉
Luminosity 7,000 [6]   L☉
Surface gravity (log g)−0.44 [4]   cgs
Temperature 2,641 [4]   K
Metallicity [Fe/H]0.54 [4]   dex
Other designations
U Ori, BD+20°1171a, HD  39816, HIP  28041, HR  2063, SAO  77730 [7]
Database references
SIMBAD data

U Orionis (abbreviated U Ori) is a Mira-type variable star in the constellation Orion. It is a classical long period variable star that has been well observed for over 120 years.

Contents

Discovery

U Orionis in the center of the image at approx visual mag. 12 on February 5th 2017 Variable star U Orionis in the constellation Orion.jpg
U Orionis in the center of the image at approx visual mag. 12 on February 5th 2017

It was discovered on 1885 December 13 by J.E. Gore and initially it was thought to be a nova in the early stages of decline (Gore's Nova and NOVA Ori 1885 as still listed in SIMBAD), but a spectrum taken at Harvard showed features similar to that of Mira. Thus U Orionis became the first long period variable to be identified by a photograph of its spectrum. [8]

Location

U Orionis lies less than half a degree east of the small-amplitude variable star χ1 Orionis and less than an arc-minute from the much fainter eclipsing variable UW Orionis. χ1 Orionis is slightly brighter than U Orionis at its brightest maximum, while UW Orionis is more than a thousand times fainter, similar to U Orionis at minimum.

Stellar parameters

The visual band light curve of U Orionis, from AAVSO data UOriLightCurve.png
The visual band light curve of U Orionis, from AAVSO data

The star has a low effective temperature (variable with the pulsations, but roughly 2,700 K), a large and bloated radius of 370  R☉, [5] and a high luminosity, 7,000 times higher than the Sun. [6] If the Sun were replaced with U Orionis, its radius would extend beyond Mars's orbital zone (about 1.7 astronomical units).

Possible planetary system

According to Rudnitskij, [10] a 12- to 15-year "super-periodicity" has been observed. The author infers such periodicity could coincide with the revolution period of an invisible companion, probably planetary. So far no clear hint of planetary objects has been detected.

Related Research Articles

Chi<sup>1</sup> Orionis Star in the constellation Orion

Chi1 Orionis is a star about 28 light years away. It is in the constellation Orion, where it can be seen in the tip of the hunter's upraised club.

<span class="mw-page-title-main">Gamma Eridani</span> Variable star in the constellation Eridanus

Gamma Eridani, formally named Zaurak, is a variable star in the constellation of Eridanus. It is visible to the naked eye with an apparent visual magnitude that varies around 2.9, and lies at a distance of about 203 light years from the Sun, as determined by the Hipparcos astrometry satellite.

<span class="mw-page-title-main">Chi Serpentis</span> Star in the constellation Serpens

Chi Serpentis is a solitary star in the Serpens Caput section of the equatorial constellation Serpens. Based upon an annual parallax shift of 14.84 mas as seen from Earth, it is located around 222 light years from the Sun. The star is bright enough to be faintly visible to the naked eye, having an apparent visual magnitude of +5.30.

<span class="mw-page-title-main">Sigma Orionis</span> Five-star system in the constellation Orion

Sigma Orionis or Sigma Ori is a multiple star system in the constellation Orion, consisting of the brightest members of a young open cluster. It is found at the eastern end of the belt, south west of Alnitak and west of the Horsehead Nebula which it partially illuminates. The combined brightness of the component stars is magnitude 3.80.

<span class="mw-page-title-main">R Boötis</span> Star in the constellation Boötes

R Boötis is a variable star in the northern constellation of Boötes. Typically the star is too faint to be readily visible to the naked eye, with a brightness that fluctuates between apparent visual magnitudes of 9.98. The distance to this star is approximately 2,150 light years based on parallax measurements. It is drifting closer with a radial velocity of about −58 km/s.

4 Camelopardalis is a probable multiple star in the northern constellation of Camelopardalis, located 177 light years away from the Sun, based upon parallax. With a combined apparent visual magnitude of 5.29, it is visible to the naked eye as a faint, white-hued star. The pair have a relatively high proper motion, traversing the celestial sphere at an angular rate of 0.158″ per year. The system's proper motion makes it a candidate for membership in the IC 2391 supercluster. They are moving away from the Earth with a heliocentric radial velocity of 22.5 km/s.

HD 30442 is a solitary star in the northern circumpolar constellation Camelopardalis. It is faintly visible to the naked eye with an apparent magnitude of 5.47 and is estimated to be 403 light years away from the Solar System. The object has a heliocentric radial velocity of −37 km/s, indicating that it is drifting closer.

<span class="mw-page-title-main">FU Orionis</span> Variable star in the constellation Orion

FU Orionis is a variable and binary star system in the constellation of Orion, that in 1937 rose in apparent visual magnitude from 16.5 to 9.6, and has since been around magnitude 9. The name FU Orionis is a variable star designation in the Argelander system, which are assigned sequentially as new variables are discovered. FU Orionis is about 1,360 light years distant and is associated with the molecular cloud Barnard 35.

<span class="mw-page-title-main">W Andromedae</span> Variable star in the constellation Andromeda

W Andromedae is a variable star in the constellation of Andromeda. It is classified as a Mira variable and S-type star, and varies from an apparent visual magnitude of 14.6 at minimum brightness to a magnitude of 6.7 at maximum brightness, with a period of approximately 397.3 days. The star is losing mass due to stellar winds at a rate of 2.79×10−7M☉/yr.

<span class="mw-page-title-main">RV Andromedae</span> Star in the constellation Andromeda


RV Andromedae is a variable star in the constellation of Andromeda. It is classified as a semiregular variable pulsating giant star, and varies from an apparent visual magnitude of 11.5 at minimum brightness to a magnitude of 9.0 at maximum brightness, with a period of approximately 168.9 days.

Chi<sup>2</sup> Orionis Star in the constellation Orion

Chi2 Orionis is a B-type supergiant star in the constellation of Orion. It has an apparent visual magnitude of 4.63 but being quite distant, and heavily extinguished it burns with the greatest absolute visual light magnitude among stars in Orion within the near reaches of the galaxy, 0.9 of a magnitude brighter than Rigel. Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified. It is considered to be a member of the Gemini OB1 association.

<span class="mw-page-title-main">31 Orionis</span> Binary star in the constellation Orion

31 Orionis is a binary star system in the equatorial constellation of Orion, located near the bright star Mintaka. It is visible to the naked eye as a faint, orange-hued point of light with a baseline apparent visual magnitude of 4.71. The distance to this system is approximately 490 light years away based on parallax, and it is drifting further away with a mean radial velocity of +6 km/s.

Psi<sup>2</sup> Orionis Spectroscopic binary system in the constellation of Orion

Psi2 Orionis a binary star system in the equatorial constellation of Orion. It has an apparent visual magnitude of 4.6, indicating that it is visible to the naked eye. Based upon an annual parallax shift of 2.87 mass, it is roughly 1,100 light years distant from the Sun.

<span class="mw-page-title-main">S Cassiopeiae</span> Star in the constellation Cassiopeia

S Cassiopeiae is a Mira variable and S-type star in the constellation Cassiopeia. It is an unusually cool star, rapidly losing mass and surrounded by dense gas and dust producing masers.

<span class="mw-page-title-main">GW Orionis</span> Star in the constellation Orion

GW Orionis is a T Tauri type pre-main sequence hierarchical triple star system. It is associated with the Lambda Orionis star-forming region and has an extended circumtrinary protoplanetary disk.

<span class="mw-page-title-main">TU Andromedae</span> Star in the constellation Andromeda

TU Andromedae is a variable star of the Mira type in the constellation Andromeda. It has a spectral type of M5e and a visual magnitude which varies between extremes of 7.6 and 13.5.

<span class="mw-page-title-main">R Fornacis</span> Variable star in the constellation Fornax

R Fornacis is a Mira variable and carbon star located in the constellation Fornax. It is around 1,800 light years away based on parallax measurements.

<span class="mw-page-title-main">BF Orionis</span> Young protostar system

BF Orionis is a young Herbig Ae/Be star in the constellation of Orion about 1250 light years away, within the Orion Nebula. It is the most massive star of the small birth cluster of four stars.

HD 46815 is a solitary star in the southern constellation Columba. It is faintly visible to the naked eye with an apparent magnitude of 5.4 and is estimated to be 408 light years away. However, it is receding with a heliocentric radial velocity of 32.2 km/s.

<span class="mw-page-title-main">UX Orionis</span> Variable star in the constellation Orion

UX Orionis is a variable star in the constellation of Orion. It is a Herbig Ae star, located about 1000 light years from the Earth. At its brightest it is a magnitude 9.5 object, so it is too faint to be seen with the naked eye. UX Orionis is the prototype of the UX Orionis class of variable stars, which are young stellar objects that exhibit large, irregular changes in visual band brightness. UX Orionis was discovered by Henrietta Swan Leavitt.

References

  1. 1 2 3 Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics . 649: A1. arXiv: 2012.01533 . Bibcode:2021A&A...649A...1G. doi: 10.1051/0004-6361/202039657 . S2CID   227254300. (Erratum:  doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  2. 1 2 3 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. S2CID   125853869.
  3. ↑ Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV Data. Bibcode:1986EgUBV........0M.
  4. 1 2 3 4 Anders, F.; Khalatyan, A.; Chiappini, C.; Queiroz, A. B.; Santiago, B. X.; Jordi, C.; Girardi, L.; Brown, A. G. A.; Matijevic, G.; Monari, G.; Cantat-Gaudin, T.; Weiler, M.; Khan, S.; Miglio, A.; Carrillo, I.; Romero-Gómez, M.; Minchev, I.; de Jong, R. S.; Antoja, T.; Ramos, P.; Steinmetz, M.; Enke, H. (1 August 2019). "Photo-astrometric distances, extinctions, and astrophysical parameters for Gaia DR2 stars brighter than G = 18". Astronomy and Astrophysics. 628: A94. arXiv: 1904.11302 . Bibcode:2019A&A...628A..94A. doi:10.1051/0004-6361/201935765. ISSN   0004-6361. S2CID   131780028.
  5. 1 2 Van Belle; et al. (1996). "Angular Size Measurements of 18 Mira Variable Stars at 2.2 microns". Astronomical Journal . 112: 2147. Bibcode:1996AJ....112.2147V. doi: 10.1086/118170 .
  6. 1 2 Mondal & Chandrasekhar (2004). "Evidence of asymmetry in Mira variable U Ori". Monthly Notices of the Royal Astronomical Society . 348 (4): 1332–1336. Bibcode:2004MNRAS.348.1332M. doi: 10.1111/j.1365-2966.2004.07454.x .
  7. ↑ "V* U Ori". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 25 January 2018.
  8. ↑ Monck (1887). "Mr Gore's Nova Orionis". The Observatory . 10: 69–71. Bibcode:1887Obs....10...69M.
  9. ↑ "Download Data". aavso.org. AAVSO. Retrieved 1 October 2021.
  10. ↑ Rudnitskij (2002). "Molecular Masers in Variable Stars". Publications of the Astronomical Society of Australia . 19 (4): 499–504. Bibcode:2002PASA...19..499R. doi: 10.1071/AS02018 .
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