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HR 2275

BSC 2275, HD 44131

Proper NameNone
Bayer DesignationNone
Flamsteed NumberNone
HR (BSC)2275
Right Ascension6h 20m 0s
Declination-2° 56' 40"
Distance465 light years
142 parsecs
MagnitudeApparent: +4.92
Absolute: -0.85
Spectral ClassM1III red giant
Optimum VisibilityJanuary
NotesHR 2275 is a periodic variable, though the details and mechanism of its variability have not been described in detail. As an evolved red giant, it is some sixty-five times the diameter of the Sun, and more than six hundred times as luminous. That luminosity level varies by 0.01 magnitudes over a period of nearly nine days.

A red star in Orion on the verge of naked-eye visibility, HR 2275 lies eastward of Orion's prominent Belt of three stars, falling close to Orion's border with neighbouring Monoceros. A little over two degrees to the southeast from this star, across the border within Monoceros, lies the open cluster Collinder 93 or NGC 2232.

With an apparent magnitude of +4.92, the star will be faintly visible to the naked eye in a clear sky, but its relative faintness is a product of its great distance from the Sun (a distance of some 465 light years). This is in fact a luminous red giant star shining with a light some sixty or seventy times brighter than that of the Sun. If it lay at a distance of ten parsecs (the standard for calculating absolute magnitude), HR 2275 would shine as brightly as Jupiter in the skies of Earth.

Imagery provided by Aladin sky atlas

HR 2275 is a variable star, showing a gradual and periodic change in magnitude over time. The star's brightness varies only slightly, rising and falling by a hundredth of a magnitude across a period of 8.9 days, but the mechanism behind this variability is not currently understood in detail. There are some indications that the primary red giant may have a much fainter binary companion, though the existence of this companion star has yet to be definitively confirmed.