Star Stars · In Tucana
Lang-Exster
Lang-Exster, α Tucanae, is an orange giant in Tucana: the 153rd brightest star in the night sky.
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- Constellation
- Tucana
- Designation
- α Tucanae
- Apparent magnitude
- 2.87 · 153rd brightest star in the night sky
- Spectral class
- K3III
- Distance
- 200 light-years
- Highest at midnight
- late August
- Position (J2000)
- RA 22h 19m · Dec −60° 16′
An orange giant, around 4,800 K, like Arcturus and Aldebaran. About 28× brighter than the faintest star the eye can see. Gives off about 220 times the Sun's visible light. The light you are seeing left around 1826.
When to see it
On the night of Mon 23 Aug 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | Never rises | ||
| New York EDT | Never rises | ||
| Singapore GMT+8 | 19:28 | 01:18 · 29° | 07:07 |
| Sydney GMT+10 | Never sets | 00:08 · 64° | — |
Common questions
- Can I see it from 50° north?
- No. From there it never rises: you would have to travel south of 29° north before it cleared the horizon at all.
- Can I see it from 35° south?
- Yes, on any clear night of the year. From there it never sets: it is circumpolar, circling the pole and still 5° up at its lowest.
- When is the best time of year to see it?
- Around late August, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by late November it is highest in the early evening, and in late May not until the hours before dawn.
- How far away is it, and how bright?
- It is 200 light-years away, and shines at magnitude 2.87 in our sky. From that far, the Sun would be a star of magnitude 8.7: too faint for the eye, a target for binoculars.
- Naked eye, binoculars or telescope?
- The naked eye, even from a city: at magnitude 2.87 it is brighter than the faintest stars a city sky still shows, about magnitude 4.5.
Look for
Start from Alnair: Lang-Exster is 13° south of it, a fist and a half at arm’s length.
Look for
From 50° north and 35° north it never rises; from the equator it climbs to 30°; from 35° south it is circumpolar and never sets.
Science
Lang-Exster’s surface is about 4,800 K, some 1,000 K cooler than the Sun’s 5,772 K, so its light is strongest at about 600 nm, where the Sun’s is strongest at 500 nm. Moved to 33 light-years, the distance astronomers compare stars at, it would shine at magnitude −1.1.
Did you know
Against Alnair, the brighter star the hop starts from: Alnair looks 2.9 times as bright as Lang-Exster in our sky, but Alnair is 101 light-years away and Lang-Exster 200 light-years, so side by side Lang-Exster would give off 1.4 times as much light as Alnair.
Science
Lang-Exster is the 85th nearest to us of the 156 stars on these pages with a measured distance. Its nearest neighbour among them in space is Tiaki, about 51 light-years from it; on our sky the two are 14° apart.
Look for
The Sun passes 45° north of Lang-Exster around late February, when it is highest at noon, in daylight: the weeks either side are its worst time of year. It is 48° from the plane of the Milky Way, well away from the band.