Tau Canis Majoris
 NGC 2362. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Canis Major |
| Right ascension | 07h 18m 42.4s |
| Declination | −24° 57′ 15″ |
| Apparent magnitude (V) | 4.37 |
| Characteristics | |
| Spectral type | O9Ib |
| Astrometry | |
| Distance | 3200 ± 2200 ly (980 ± 680 pc) |
| Details | |
| Radius | 19.8[1] R☉ |
| Surface gravity (log g) | 3.5[1] cgs |
| Temperature | 33,145 ± 145[1] K |
| Other designations | |
Tau Canis Majoris (τ CMa, τ Canis Majoris) is an eclipsing spectroscopic binary in the constellation Canis Major and the brightest star of an open cluster designated NGC 2362. Approximately 3200 light years from Earth, the star is actually a multiple star system with some massive components.[2]
This star is sometimes known as the 'Mexican Jumping Star' by amateur astronomers, because it can appear to 'jump around' with respect to the other stars in the cluster because of its marked contrast in brightness.[3]
τ Canis Majoris is classified as an O-type blue supergiant with a mean apparent magnitude of +4.37. It is a Beta Lyrae type variable star with a period of 1.28 days, over which time its brightness varies from magnitude +4.32 to +4.37.[4] It might be that one or more components are intrinsically variable.
The main star can be split into components of apparent magnitude 4.9 and 5.3 0.15 arcseconds apart, with a magnitude 10 component 8 arcseconds distant. The brighter of these is composed of three stars- two egg-shaped stars that are 0.1 astronomical unit (AU) apart and orbit each other every 1.28 days and a third that orbits this pair every 155 days at a distance similar to that of Jupiter from our Sun. The 5.3 magnitude star lies 223 AU distant from the group and takes more than a year to orbit the others, and the 10th magnitude star is 13,000 AU distant. Combined, the four close stars have a combined mass 80 times that of the Sun and shine with 500,000 times its luminosity, but little is known of their individual properties.[2]
References
- ↑ 1.0 1.1 1.2 Underhill, A. B. et al. (November 1979), "Effective temperatures, angular diameters, distances and linear radii for 160 O and B stars", Monthly Notices of the Royal Astronomical Society 189: 601–605, Bibcode:1979MNRAS.189..601U, doi:10.1093/mnras/189.3.601
- ↑ 2.0 2.1 Kaler, James B. "Tau Canis Majoris". Stars. University of Illinois. Retrieved 22 March 2014.
- ↑ The Mexican Jumping Star
- ↑ Watson, Christopher (4 January 2010). "Tau Canis Majoris". AAVSO Website. American Association of Variable Star Observers. Retrieved 21 March 2014.
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