When is the best time to observe Biham?

Biham is best observed from July through September, with peak visibility during August when it transits around midnight in the Northern Hemisphere.

Where is Biham located in the sky?

Biham lies in the constellation Pegasus at right ascension 22h 10m and declination +06° 12′.

What telescope do I need to split Biham?

Splitting Biham requires an aperture of roughly 200 mm or larger — the components are separated by about 0.2″ at magnitudes near 3.5. The companion is about 7.0 magnitudes fainter, so glare from the primary — not separation — sets the minimum aperture. Larger apertures and steady seeing help resolve the pair cleanly.

Biham — Double Star in Pegasus

HIP 109427; Theta Pegasi; 26 Pegasi

Magnitude 3.5^m DoubleStar Pegasus (Peg) Visible

Star Map + List + Plan

About Biham

Description

Biham, Theta Pegasi, is an A1 main-sequence star about 92 light-years away in the southern region of Pegasus. It shines at magnitude 3.53 and has a mass of about 2.1 Suns. Biham rotates rapidly (projected equatorial velocity around 150 km/s) — typical of young A-type dwarfs. It has no known companions from radial-velocity surveys.

Observing Tips

Biham sits between the Great Square of Pegasus and the head of the horse, marking the throat in the traditional figure. In small telescopes it appears as a sharp blue-white point. Best observed August through December.

History

The name Biham comes from the Arabic "al-biham," meaning "the cattle" or "the lucky stars of the cattle" — another of the pre-Islamic weather-fortune stars of this region. The IAU adopted the name in 2016.

Fun Facts

Biham is one of the many bright A-type stars used as photometric standards by professional observatories: its stable, line-clean spectrum makes it easy to calibrate instrument responses. The nearby horse-head Pegasus starfield offers several other A-type standards as well.