In Delta Ori A, two closely separated stars orbit around each other every 5.7 days, while a third star orbits this pair with a period of over 400 years. The more massive, or primary, star in the closely-separated stellar pair weighs about 25 times the mass of the Sun, whereas the less massive, or secondary star, weighs about ten times the mass of the Sun.
The chance alignment of this pair of stars allows one star to pass in front of the other during every orbit from the vantage point of Earth. This special class of star system is known as an "eclipsing binary," and it gives astronomers a direct way to measure the mass and size of the stars.
Fast Facts for Delta Orionis:
Scale: Main image is 21 x 25 degrees (462 x 540 light years); X-ray inset image is 44 arcsec across (0.25 light years)
Category: Normal Stars & Star Clusters
Coordinates (J2000): RA 05h 32m 00.40s | Dec -00° 17' 56.70"
Observation Date: 4 pointings between 19 and 27 Dec 2012
Observation Time: 138 hours 63 min. (5 days 18 hours 63 min)
Obs. ID: 14567-14570
Color Code X-ray: Pink; Optical: Red, Green, Blue
Distance Estimate: About 1,240 light years
- Corcoran, M et al, 2015, ApJ, 809, 132; arXiv:1507.05101
- Nichols, J et al, 2015, ApJ, 809, 133, arXiv:1507.04972
- Pablo, H et al, 2015, ApJ, 809, 134, arXiv:1504.08002
- Shenar, T et al, 2015, ApJ, 809, 135, arXiv:1503.03476