U Camelopardalis

U Camelopardalis is a semiregular variable star in the constellation Camelopardalis. Based on parallax measurements made by the Hipparcos spacecraft, it is located about 3,000 light-years (1,000 parsecs) away from the Earth.^[1] Its apparent visual magnitude is about 8, which is dim enough that it cannot be seen with the unaided eye.

U Camelopardalis

U Camelopardalis is a bright star surrounded by a tenuous shell of gas. Its atmosphere contains more carbon than oxygen.
Observation data Epoch J2000      Equinox J2000
Constellation	Camelopardalis
Right ascension	03h 41m 48.17393s[1]
Declination	+62° 38′ 54.3906″[1]
Apparent magnitude (V)	7.55[2]
Characteristics
Spectral type	C-N55.5 (MS4)[3]
U−B color index	+3.50[2]
B−V color index	+1.95[2]
Variable type	SRb[4]
Astrometry
Radial velocity (Rv)	-3.00[5] km/s
Proper motion (μ)	RA: 3.50[1] mas/yr Dec.: -3.62[1] mas/yr
Parallax (π)	1.03±0.59 mas[1]
Distance	530[6] pc
Absolute magnitude (MV)	−2.4 (max)[7]
Details
Luminosity	8,472[8] L☉
Temperature	3,000[9] K
Other designations
U Cam, BD+62° 596, HD 22611, HIP 17257, SAO 12870, GC 4371
Database references
SIMBAD	data

The spectral type of U Camelopardalis in the revised MK system is C-N5, which indicates a classical carbon star spectrum approximately corresponding to late K or early M.^[10] The C₂ index is 5.5 which is typical of a C-N star.^[11] It is also given an alternative spectral type of MS4, indicating a star similar to an M4 class but with somewhat enhanced ZrO bands.^[3] The spectral type may vary between C3,9 and C6,4e.^[4]

A visual band light curve for U Camelopardalis, plotted from AAVSO data^[12]

In 1891, Williamina Fleming announced that the star (then known as DM +62°.596) is a variable star, based on 13 photographs taken in 1890 and 1891.^[13] It was listed with its variable star designation, U Camelopardalis, in Annie Jump Cannon's 1907 work Second Catalog of Variable Stars.^[14] U Camelopardalis is a carbon star. These types of stars have greater levels of carbon in their atmospheres than oxygen, which means they form carbon compounds that make the star appear strikingly red. U Camelopardalis is nearly 4 magnitudes fainter at blue wavelengths than in the centre of the visual range. In the infrared K band it has an apparent magnitude of 0.37.^[15] Its brightness varies without a dominant period and it is classified as semi-regular, although a period of 400 days has been published.^[15] In the V photometric band the brightness varies by around half a magnitude,^[16] but the amplitude is nearly two magnitudes at blue wavelengths.^[4] The maximum visual magnitude has been given as 7.2.^[7]

The shell of gas surrounding U Camelopardalis was imaged by the Hubble Space Telescope in 2012, showing a nearly perfect sphere of gas surrounding the star.^[17]

U Cameloparadlis has a 10th magnitude companion 308" away. It is a B8 main sequence star, hotter but less luminous than U Cam itself. They are not thought to be physically associated.^[7]