When is the best time to observe Cebalrai?

Cebalrai is best observed from May through July, with peak visibility during June when it transits around midnight in the Northern Hemisphere.

Where is Cebalrai located in the sky?

Cebalrai lies in the constellation Ophiuchus at right ascension 17h 43m and declination +04° 34′.

What telescope do I need to see Cebalrai?

At magnitude 2.8, Cebalrai is visible to the naked eye from dark skies, easy in any binoculars.

Cebalrai — Star in Ophiuchus

HIP 86742; Beta Ophiuchi; 60 Ophiuchi

Magnitude 2.8^m Star Ophiuchus (Oph) Visible

Star Map + List + Plan

About Cebalrai

Description

Cebalrai is an orange giant of spectral type K2III at magnitude 2.77 in Ophiuchus. Located about 82 light-years from Earth, it has a luminosity of roughly 63 times solar and a surface temperature of about 4,600 K. In 2018, a giant exoplanet was confirmed orbiting Cebalrai, with a minimum mass of about 0.9 Jupiter masses.

Observing Tips

Cebalrai is located in the eastern part of Ophiuchus, forming a pair with Rasalhague (Alpha Oph) at the head of the Serpent Bearer. Its warm orange color is noticeable in binoculars. Best observed from June through September. Ophiuchus is a large but somewhat shapeless constellation, and Cebalrai helps define its eastern boundary.

History

The name Cebalrai (sometimes spelled Cheleb or Kelb Alrai) comes from the Arabic 'kalb al-ra'i,' meaning 'the shepherd's dog.' In Chinese astronomy, it was part of the 'Right Wall' asterism. Ophiuchus has been associated with Asclepius, the Greek god of medicine, since ancient times.

Fun Facts

Cebalrai's confirmed exoplanet orbits at about 1.4 AU — a distance similar to Mars in our solar system. The planet was discovered through precise radial velocity measurements that detected the gravitational tug of the planet on the star.