Alniyat (Sigma Scorpii)
Alniyat (Sigma Scorpii) is a star in the constellation Scorpius, magnitude 2.9.
One of the two ‘arteries’ beside the Scorpion’s heart — a young family of four stars, led by a pulsing giant.
Arab astronomers saw two arteries beside the Scorpion’s heart: Sigma and Tau Scorpii, flanking red Antares. Alniyat, from al-niyāṭ, ‘the arteries’, is the northern one. To the Boorong people of north-western Victoria the two flanking stars were the wives of Djuit, the red star between them, and in Hawaii Alniyat was Au-haele, one of a line of three with Antares.
Up close it is a family of four. A blue-white giant of about 18 solar masses and a smaller partner whirl round each other every 33 days, too close to split in any telescope. A third star circles them over more than a century, and a fourth lies far beyond.
The giant also pulses as a Beta Cephei variable star, its surface temperature swinging by thousands of degrees with each beat of about six hours. The whole family belongs to the Scorpius–Centaurus association, a vast group of young stars.
Alniyat (Sigma Scorpii) is 700 light-years away: the light we see from it set off around 1325, 130 years before Gutenberg printed his Bible.
Did you know?
- Younger than the dinosaurs’ end. Alniyat is only 8 to 10 million years old. When it formed, the dinosaurs had already been gone for more than 55 million years.
- First Star of the Heart. Chinese astronomers grouped Alniyat with Antares and Tau Scorpii as Xīn, the Heart. Alniyat is the Heart’s first star.
The blue-white star just north-west of red Antares, one of the pair that flank the Scorpion’s heart. The globular cluster M 4 lies about a degree to its south-east, between Alniyat and Antares — an easy hop.
When and where to see it
It is best placed in the evening sky around June, when it crosses the meridian at about 10 pm local time (around midnight in May). It can be seen from everywhere south of 64°N and never sets south of 64°S.
At its highest it stands 14° up from 50°N, 29° up from 35°N, 64° up from the equator, 81° up from 35°S.
Facts
- Type
- Star
- Constellation
- Scorpius
- Designations
- Sigma Scorpii, σ Sco, 20 Sco, HR 6084, HD 147165, HIP 80112
- Magnitude
- 2.9
- Position
- RA 16h 21.2m, Dec −25° 36′ (J2000)
- Spectral type
- B1III+B1:V
- Colour
- white (B−V 0.13)
- Distance
- 700 light-years
- Discovered
- Known since antiquity
Open AstroPilot to see when Alniyat (Sigma Scorpii) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.