U Orionis

U Orionis

Location of U Orionis (circled)
Observation data 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]
Distance		930 ± 50 ly (290 ± 10 pc)
Details
dex
HR 2063, SAO 77730[7]
Database references
SIMBAD	data

U Orionis (abbreviated U Ori) is a

star that has been well observed for over 120 years.

Discovery

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

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 (variable with the pulsations, but roughly 2,700 K), a large and bloated radius of 370 

).

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.

References