Star Stars · In Crux
Gacrux
Gacrux, γ Crucis, is a red giant in Crux: the 26th brightest star in the night sky.
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- Constellation
- Crux
- Designation
- γ Crucis
- Apparent magnitude
- 1.59 · 26th brightest star in the night sky
- Spectral class
- M4III
- Distance
- 88.6 light-years
- Highest at midnight
- late March
- Position (J2000)
- RA 12h 31m · Dec −57° 07′
A red giant, around 3,200 K, like Betelgeuse and Antares. About 92× brighter than the faintest star the eye can see. Gives off about 140 times the Sun's visible light. The light you are seeing left around 1937.
When to see it
On the night of Sat 27 Mar 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT | Never rises | ||
| New York EDT | Never rises | ||
| Singapore GMT+8 | 19:27 | 01:17 · 31° | 07:08 |
| Sydney GMT+11 | Never sets | 01:08 · 67° | — |
Common questions
- Can I see it from 50° north?
- No. From there it never rises: you would have to travel south of 32° north before it cleared the horizon at all.
- Can I see it from 35° south?
- Yes, on any clear night of the year — it is circumpolar from there and never quite sets, though at its lowest it skims the horizon, where trees and haze will hide it.
- When is the best time of year to see it?
- Around late March, when it stands opposite the Sun and is highest at midnight. It comes round about two hours earlier each month, so by late June it is highest in the early evening, and in late December not until the hours before dawn.
- How far away is it, and how bright?
- It is 88.6 light-years away, and shines at magnitude 1.59 in our sky. From that far, the Sun would be a star of magnitude 7.0: one you would need a dark country sky to see at all.
- Naked eye, binoculars or telescope?
- The naked eye, even from a city: at magnitude 1.59 it is brighter than the faintest stars a city sky still shows, about magnitude 4.5.
Look for
Start from Mimosa: Gacrux is 3.4° north-west of it, two fingers at arm’s length.
Look for
From 50° north and 35° north it never rises; from the equator it climbs to 33°; from 35° south it is circumpolar and never sets.
Science
Gacrux’s surface is about 3,200 K, some 2,600 K cooler than the Sun’s 5,772 K, so its light is strongest at about 910 nm, in the infrared, past the red 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 −0.6, about as bright as Canopus looks to us.
Did you know
Against Mimosa, the brighter star the hop starts from: Mimosa looks 1.4 times as bright as Gacrux in our sky; Mimosa is 279 light-years away and Gacrux 89 light-years, so side by side Mimosa would give off 14 times as much light as Gacrux.
Science
Gacrux is the 47th nearest to us of the 156 stars on these pages with a measured distance. Its nearest neighbour among them in space is Kulou, about 41 light-years from it; on our sky the two are 22° apart.
Look for
The Sun passes 48° north of Gacrux around late September, when it is highest at noon, in daylight: the weeks either side are its worst time of year. It is 6° from the plane of the Milky Way, inside the band a dark sky shows.