Rasalhague
Where is Rasalhague?
Look southwest, about 39° up at 20:20 in Ophiuchus. It sinks lower through the evening and sets at 00:46.
- Rises
- 10:27
- Highest
- 17:39
- Sets
- 00:46
- Best after dark
- 20:20 · 39°
Can I see Rasalhague tonight?
From London tonight, Rasalhague is above the horizon after dark. It’s highest soon after dark, around 20:20, in the southwest at 39°.
At magnitude 2.1 it is visible by eye, even from many towns, when the sky is clear.
This is position and timing only: clouds, haze and light pollution aren’t included.
What does Rasalhague look like?
Rasalhague looks white to the eye (color is easier to see in binoculars). Its spectral type is A5IVnn: white subgiant (hotter than the Sun).
Eyes
A white star in a large, dim area between Vega and Antares.
Binoculars
A white point near the fainter Rasalgethi, which is orange-red.
Telescope
A point of light. Ophiuchus contains many globular clusters to explore.
About Rasalhague
Rasalhague is the brightest star in Ophiuchus, the Serpent Bearer, and marks his head. Its name comes from the Arabic for “head of the serpent collector”.
It is a white star about 49 light-years away that spins quickly and has a smaller companion star.
Rasalhague is about two and a half times the mass of the Sun and roughly 25 times as luminous. Its fast spin flattens it noticeably.
Its companion orbits it about every eight and a half years. Following that orbit has let astronomers measure the masses of both stars.
Ophiuchus represents a healer, often linked to Asclepius in Greek mythology. The Sun passes through Ophiuchus each year between Scorpius and Sagittarius, although it isn’t one of the traditional zodiac constellations.
The constellation is rich in globular clusters, including M10 and M12, and it was the site of the last supernova seen in our galaxy, in 1604.
Rasalhague in Ophiuchus
Questions
What is Ophiuchus?
Sources: SkyMate; Wikidata (CC0). Positions computed for your place and time with astronomy-engine. Data & Licences