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 49.16994s [1]
Declination +20° 10 30.6872 [1]
Apparent magnitude  (V)4.8 - 13.0
Characteristics
Spectral type M8 III
B−V color index +2.07 [2]
Variable type Mira
Astrometry
Parallax (π)2.29 ± 1.21 [1]   mas
Distance 997.56  ly
(306 ± 61 [3]   pc)
Details
Radius 370 ± 96 [4]   R
Luminosity 7,000 [5]   L
Temperature ≈2,750 [5]   K
Other designations
U Ori, BD+20° 1171a, HD  39816, HIP  28041, HR  2063, SAO  77730 [6]
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. [7]

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 star has a low effective temperature (roughly 2700 K) but a large and bloated radius of 370 solar radii [4] and a high luminosity, 7,000 times higher than the Sun. [5] If the Sun were replaced with U Orionis, its radius would extend beyond Mars's orbital zone (about 1.7 astronomical units), and, to be habitable with water at liquid state and a comfortable temperature, a planet would have to be located within 85 AU, within the Kuiper belt's orbital zone.[ citation needed ]

Possible planetary system

According to Rudnitskij, [8] 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 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 220 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.

Psi Virginis variable star

Psi Virginis is a suspected binary star system in the zodiac constellation of Virgo. It can be seen with the naked eye and has an apparent visual magnitude of +4.80. Based upon the annual parallax shift of 5.99 milliarcseconds, the distance to this star is roughly 540 light years. The angular size of Psi Virginis was measured on December 26, 1975 during an occultation by the Moon, yielding the estimate 6.5±0.3 milliarcsec.

Upsilon Virginis Star in the constellation Virgo

Upsilon Virginis is a single star in the zodiac constellation of Virgo. It has an apparent visual magnitude of 5.25, making it faintly visible to the naked eye. According to the Bortle scale, it is visible from backlit suburban skies at night. Based upon a measured annual parallax shift of 0.012.47 arcseconds, it is located roughly 262 light-years from the Sun. If the star were at a distance of 33 light-years, it would have a magnitude of +0.4 and be the third-brightest star in the night sky.

Eta Orionis star in the constellation Orion

Eta Orionis is a multiple star in the constellation Orion. It lies a little to the west of Orion's belt between Delta Orionis and Rigel, being closer to Delta Orionis than to Rigel. It lies at a distance of around 1,000 light years from Earth and is part of the Orion OB1 association.

Kappa Lyrae Star in the constellation Lyra

κ Lyrae, Latinized as Kappa Lyrae, is a solitary star in the northern constellation of Lyra, near the constellation border with Hercules. It is visible to the naked eye as a faint, orange-hued point of light with an apparent visual magnitude of 4.33. This object is located approximately 238 light years from the Sun based on parallax, but is moving closer with a radial velocity of −24 km/s.

HD 88218 is a binary star in the southern constellation of Antlia. With an apparent magnitude of 6.16, the system is faintly visible to the naked eye from dark skies. The pair orbit each other with a period of about 86 years.

HD 151967 is suspected variable star in the southern constellation of Ara. It is a sixth magnitude star, which means it is just visible to the naked eye in dark skies. Parallax measurements place it at a distance of approximately 710 light years from the Earth.

HD 118508 is a variable star in the northern constellation of Boötes. It varies marginally in luminosity with an amplitude of 0.04 in magnitude.

HD 126271 is a suspected variable star in the northern constellation of Boötes.

HD 126141 is a suspected variable star in the northern constellation of Boötes.

HD 27245 is a variable red giant star in the northern constellation of Camelopardalis.

Chi Ceti , is the Bayer designation for a double star in the equatorial constellation of Cetus. They appear to be common proper motion companions, sharing a similar motion through space. The brighter component, HD 11171, is visible to the naked eye with an apparent visual magnitude of 4.66, while the fainter companion, HD 11131, is magnitude 6.75. Both lie at roughly the same distance, with the brighter component lying at an estimated distance of 75.6 light years from the Sun based upon an annual parallax shift of 43.13 mass.

χ Eridani is a binary star system in the constellation Eridanus. It is visible to the naked eye with an apparent visual magnitude of 3.70. The distance to this system, as determined using the parallax method, is around 58 light years. The pair had an angular separation of 5.0 arcseconds as of 1994. This corresponds to a projected separation of around 128 AU.

Pi<sup>1</sup> Orionis star

Pi1 Orionis1 Ori, π1 Orionis) is a star in the equatorial constellation of Orion. It is faintly visible to the naked eye with an apparent visual magnitude of 4.74. Based upon an annual parallax shift of 28.04 mas, it is located about 116 light years from the Sun.

Pi<sup>5</sup> Orionis star

Pi5 Orionis5 Ori, π5 Orionis) is a binary star system in the constellation Orion. It has an apparent visual magnitude of 3.69, which is bright enough to be visible to the naked eye on a clear night. Based upon an annual parallax shift of 2.43 mas, it is around 1,300 light years distant from the Sun.

Omicron2 Orionis is a solitary star in the constellation Orion. It has an apparent visual magnitude of 4.06, which is bright enough to be seen with the naked eye. Based upon an annual parallax shift of 17.54 mas, it is around 186 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an interstellar absorption factor of 0.09 due to intervening dust.

Omega Orionis variable star in Orion

Omega Orionis is a star in the constellation Orion. Its apparent magnitude is 4.57 and is located approximately 1,400 light years from our solar system. It is surrounded by a cloud of dust, forming a modest reflection nebula over a light-year wide.

Omicron<sup>1</sup> Orionis star in the constellation Orion

Omicron1 Orionis is a binary star in the northeastern corner of the constellation Orion. It is visible to the naked eye with an apparent visual magnitude of 4.7. Based upon an annual parallax shift of 5.01±0.71 mas, it is located approximately 650 light years from the Sun. At that distance, the visual magnitude of the star is diminished by an interstellar absorption factor of 0.27 due to intervening dust.

59 Serpentis, also known as d Serpentis, is a multiple star in the constellation Serpens. It is a triple star system. The primary system is a spectroscopic binary consisting of an A-type star and an orange giant, while the secondary is another orange giant. The system shows irregular variations in brightness between magnitudes 5.17 and 5.2.

1 Lyncis is a single star in the northern constellation of Lynx. It is also known by its variable star designation of UW Lyncis; 1 Lyncis is the Flamsteed designation. This object is visible to the naked eye as a faint, reddish-hued star with an apparent visual magnitude of 4.95. It is moving further from the Earth with a heliocentric radial velocity of 12 km/s.

References

  1. 1 2 3 van Leeuwen, F.; et al. (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. S2CID   18759600.
  2. Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's Ubv Data. Bibcode:1986EgUBV........0M.
  3. Mondal (2005). "Evidence of asymmetry in Mira variable U Ori". Bulletin of the Astronomical Society of India . 33 (2): 97–102. Bibcode:2005BASI...33...97M.
  4. 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.
  5. 1 2 3 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 .
  6. "V* U Ori". SIMBAD . Centre de données astronomiques de Strasbourg . Retrieved 25 January 2018.
  7. Monck (1887). "Mr Gore's Nova Orionis". The Observatory . 10: 69–71. Bibcode:1887Obs....10...69M.
  8. 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 .