Star Stars · In Scorpius
Paikauhale
Paikauhale, τ Scorpii, is a blue-white main-sequence star in Scorpius: the 137th brightest star in the night sky.
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- Constellation
- Scorpius
- Designation
- τ Scorpii
- Apparent magnitude
- 2.82 · 137th brightest star in the night sky
- Spectral class
- B0V
- Distance
- 474 light-years
- Highest at midnight
- late May
- Position (J2000)
- RA 16h 36m · Dec −28° 13′
A blue-white main-sequence star, around 30,000 K, like Rigel and Spica. About 30× brighter than the faintest star the eye can see. Gives off about 1,300 times the Sun's visible light. The light you are seeing left around 1552.
When to see it
On the night of Fri 28 May 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | 22:03 | 01:12 · 10° | 04:22 |
| New York EDT | 20:58 | 01:07 · 21° | 05:16 |
| Singapore GMT+8 | 19:22 | 01:18 · 60° | 07:14 |
| Sydney GMT+10 | 16:45 | 00:09 · 84° | 07:32 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 12° up in the south.
- Can I see it from 35° south?
- Yes, and well placed: at its highest it passes almost overhead, 83° up, above most of the air’s haze.
- When is the best time of year to see it?
- Around late May, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by late August it is highest in the early evening, and in late February not until the hours before dawn.
- How far away is it, and how bright?
- It is 474 light-years away, and shines at magnitude 2.82 in our sky. From that far, the Sun would be a star of magnitude 10.6: too faint for the eye, a target for binoculars.
- Naked eye, binoculars or telescope?
- The naked eye, even from a city: at magnitude 2.82 it is brighter than the faintest stars a city sky still shows, about magnitude 4.5.
Look for
Start from Antares: Paikauhale is 2.3° south-east of it, two fingers at arm’s length.
Look for
From 50° north it climbs to 12°; from 35° north it climbs to 27°; from the equator it climbs to 62°; from 35° south it climbs to 83°.
Science
Paikauhale’s surface is about 30,000 K, some 24,200 K hotter than the Sun’s 5,772 K, so its light is strongest at about 100 nm, in the ultraviolet, past the violet end of what the eye can see, 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 −3.0, brighter than Sirius, the brightest star in our sky.
Did you know
Against Antares, the brighter star the hop starts from: Antares looks 5.1 times as bright as Paikauhale in our sky; Antares is 554 light-years away and Paikauhale 474 light-years, so side by side Antares would give off 6.9 times as much light as Paikauhale.
Science
Paikauhale is the 123rd nearest to us of the 156 stars on these pages with a measured distance. Its nearest neighbour among them in space is Antares, about 82 light-years from it; on our sky the two are 2.3° apart.
Look for
Paikauhale lies 6.1° south of the ecliptic, close enough to the Sun’s path that the Moon can pass in front of it and the planets pass near it. The Sun goes by around late November, and for weeks either side it is lost in the glare. From 50° north it is above the horizon for about 7 hours a day, from 35° north about 9 and from 35° south about 15. It is 13° from the plane of the Milky Way.