This is every star brighter than magnitude 3.55. . We present the discovery by optical and near-infrared imaging of an extremely red, low-luminosity population of isolated objects in the young, nearby stellar cluster around the multiple, massive star σ Orionis.

The star's variation in brightness was first noted by Sir John Herschel in his Outlines of Astronomy in 1836. We have performed a deep IJ-band search, covering an area of 790 arcmin^2 close to the cluster centre. Magnitude: Unknown Distance: 1600 light years (Horsehead Nebula, aka B33); 826 light years (Alnitak- Zeta Orionis); 1165 light years (Sigma Orionis) RA: 5h 40m 56s Dec: -1 degrees 56' 21" Description: This is one of the most interesting regions of the night sky, containing 3 different types of nebulae: emission, reflection, and dark. By considering stars at a fixed distance, astronomers can compare the real (intrinsic) brightnesses of different stars. The absolute magnitude of a star, M is the magnitude the star would have if it was placed at a distance of 10 parsecs from Earth. The stellar distances are only fairly accurate for stars well within 1000 light years. Alnitak . The Brightest Stars. Alnilam, the Brightest Gem in the Orion’s Belt . We investigate the mass function in the substellar domain down to a few Jupiter masses in the young sigma Orionis open cluster (3+/-2 Ma, d = 360^+70_-60 pc). Alnitak or Zeta Orionis (Zet Ori) is the 5th brightest naked eye star in the constellation Orion.With an apparent magnitude of 1.74c, Alnitak is the 31st brightest star in the entire sky (see: 50 Brightest Stars ).Its absolute magnitude is -5.26 and its distance is 818 light years.The Equinox J2000 equatorial coordinates are RA = 05h 40m 45.5s, Dec = -01° 56' 34". This is a list of the 300 brightest stars made using data from the Hipparcos catalogue. Request PDF | The σ Orionis Cluster | The σ Orionis cluster is the group of stars surrounding the high mass σ Ori stellar system. Alpha Orionis is classified as a semi-regular variable star, which means that Betelgeuse occasionally outshines its bright neighbour Rigel.

Life and times of the blue supergiant that occupies the central position in one of the most famous and recognizable asterisms of the sky. Recent findings suggest that the star emits more light than 100,000 Suns. absolute magnitude of -6.05. This survey was complemented with an infrared follow-up in the HKs- and Spitzer 3.6-8.0 mum-bands.