12 Camelopardalis
Binary star with variable brightness and X-ray emission.
Gzen92 · CC BY-SA 4.0
12 Camelopardalis is a binary star system in the northern circumpolar constellation Camelopardalis, located approximately 700 light years from the Sun. It is notable as a variable star designated BM Camelopardalis, an RS Canum Venaticorum variable whose brightness changes due to starspots, and as an X-ray source detected by multiple observatories.
- Designation
- 12 Camelopardalis / BM Camelopardalis
- Constellation
- Camelopardalis
- Distance
- 700 light years
- Apparent magnitude
- 6.08
- Spectral type
- K0 IIIe
- Variable type
- RS Canum Venaticorum
- Orbital period
- 80.9 days (disputed: 80.17 days with eccentricity 0.35)
Lore & Background
12 Camelopardalis appears close to 11 Camelopardalis in the sky, separated by only 3 arcminutes, but they are not a physical binary system; 11 Camelopardalis is an unrelated background star at a different distance. The system is moving away from Earth with a heliocentric radial velocity of +2 km/s. Abt et al. (1969) identified it as a single-lined spectroscopic binary and computed an orbital solution with a period of 80.17 days and an eccentricity of 0.35, but an ellipticity effect with a period of 79.93±0.05 days was inconsistent with that orbit, and the lack of amplitude modulation did not fit the large eccentricity. Hall et al. (1995) later found an orbital period of 80.9 days and an eccentricity statistically indistinguishable from zero.
Reader's Guide
The visible component is an evolved giant star of class K0 IIIe, showing strong emission lines. Joel A. Eaton et al. discovered its brightness variation in 1980, and it received its variable star designation in 1981. As an RS Canum Venaticorum variable, its brightness varies by 0.14 magnitudes with a period of 82.9 days due to starspots, and the star likely rotates synchronously with its orbital period. Its magnetic activity has two overlapping cycles of 14.8 and 8.5 years, occurring at two latitudes. BM Cam emits X-rays and has been detected by HEAO 1, the Einstein Observatory, and ROSAT, designated as the X-ray source 1H 0501+592.
Did You Know?
- 12 Camelopardalis is just visible to the naked eye as a dim, orange-hued star.
- It appears close to 11 Camelopardalis in the sky, only 3 arcminutes away, but the two are not physically related.
- The system's orbital eccentricity is disputed, with one study finding 0.35 and another finding it statistically indistinguishable from zero.
Gallery
Frequently Asked Questions
What is 12 Camelopardalis?
It is a close binary star system in the northern circumpolar constellation Camelopardalis, sitting roughly 700 light-years from Earth. The pair is catalogued both as a variable star (BM Camelopardalis) and as a detected X-ray emitter.
Why does 12 Camelopardalis change in brightness?
It is classified as an RS Canum Venaticorum variable, so its dimming and brightening cycles are driven by large starspots rotating in and out of view on the surfaces of its two component stars.
What spectral type does 12 Camelopardalis have?
The system is designated K0 IIIe, meaning it is a late-type K star in a giant evolutionary stage that also shows emission lines, consistent with the active, spotted nature of RS Canum Venaticorum pairs.
How bright does 12 Camelopardalis appear from Earth?
Its apparent magnitude is about 6.08, placing it right at the threshold of naked-eye visibility under very dark, moonless skies, though it is far easier to spot with binoculars or a small telescope.
Why do X-ray astronomers care about 12 Camelopardalis?
It has been picked up by multiple X-ray observatories, providing a relatively nearby example of coronal X-ray emission from a cool, magnetically active binary and making it a useful benchmark for studying how starspots and flares power high-energy output in K-type giants.
More in Astronomical X-ray sources 1-24
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