Hassaleh (Iota Aurigae)
Hassaleh (Iota Aurigae) is a star in the constellation Auriga, magnitude 2.7.
An orange giant Chaucer knew — now carrying a name no one can explain.
Geoffrey Chaucer knew this star. In his Treatise on the Astrolabe of 1391 it appears as Alkab, one of the star markers on the instrument. Alkab was short for an Arabic phrase meaning “the ankle of the rein holder” — the Charioteer, Auriga.
Its modern name is a puzzle. Hassaleh first turned up in Antonín Bečvář’s 1951 star atlas, and despite extensive searching no one has found its origin or linked it to any language.
The star itself is an orange giant, cooler than the Sun at about 4,160 K. Loops of plasma at around 3 million K in its outer atmosphere give off faint X-rays. In 2007 astronomers announced two possible brown dwarfs circling it, but they have never been confirmed; the signal may instead come from slow pulsations of the star itself.
Hassaleh (Iota Aurigae) is 490 light-years away: the light we see from it set off around 1535, around the time Copernicus put the Sun at the centre of the Solar System.
Did you know?
- First of the Five Chariots. In Chinese astronomy Hassaleh is the first star of the Five Chariots, a pattern in Auriga that also includes Mahasim.
- Dimmed by dust. Dust between us and Hassaleh dims it by about 0.6 magnitudes. Without it, the star would look about 1.7 times as bright.
- A yardstick star. Since 1943 its spectrum has served as one of the stable reference points that astronomers use to classify other stars.
An orange star of magnitude 2.7 at the south-western corner of Auriga’s pentagon. Compare its orange with blue-white Elnath, the pentagon’s southern tip; binoculars make the contrast easy to see.
When and where to see it
It is best placed in the evening sky around January, when it crosses the meridian at about 10 pm local time (around midnight in December). It can be seen from everywhere north of 57°S and never sets north of 57°N.
At its highest it stands 73° up from 50°N, 88° up from 35°N, 57° up from the equator, 22° up from 35°S.
Facts
- Type
- Star
- Constellation
- Auriga
- Designations
- Iota Aurigae, ι Aur, 3 Aur, HR 1577, HD 31398, HIP 23015
- Magnitude
- 2.7
- Position
- RA 4h 57.0m, Dec +33° 10′ (J2000)
- Spectral type
- K3II-III
- Colour
- orange-red (B−V 1.53)
- Distance
- 490 light-years
- Discovered
- Known since antiquity
Open AstroPilot to see when Hassaleh (Iota Aurigae) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.