Star Stars · In Hercules
Rutilicus
Rutilicus, ζ Herculis, is a yellow-white subgiant in Hercules: the 135th brightest star in the night sky.
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- Constellation
- Hercules
- Designation
- ζ Herculis
- Apparent magnitude
- 2.81 · 135th brightest star in the night sky
- Spectral class
- F9IV
- Distance
- 35.0 light-years
- Highest at midnight
- late May
- Position (J2000)
- RA 16h 41m · Dec +31° 36′
A yellow-white subgiant, around 6,200 K, like Procyon. About 30× brighter than the faintest star the eye can see. Gives off about 7 times the Sun's visible light. The light you are seeing left in 1991.
When to see it
On the night of Sun 30 May 2027, when it is highest around midnight, on each city’s own clock:
| From | Rises | Highest | Sets |
|---|---|---|---|
| London GMT+1 | 15:49 | 01:09 · 70° | 10:30 |
| New York EDT | 16:58 | 01:04 · 81° | 09:10 |
| Singapore GMT+8 | 19:12 | 01:15 · 60° | 07:17 |
| Sydney GMT+10 | 19:44 | 00:06 · 25° | 04:27 |
Common questions
- Can I see it from 50° north?
- Yes. It rises and sets, and at its highest it stands 72° up in the south.
- Can I see it from 35° south?
- Yes. It rises and sets, and at its highest it stands 23° up in the north.
- 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 35.0 light-years away, and shines at magnitude 2.81 in our sky. From that far, the Sun would be a star of magnitude 5.0: 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 2.81 it is brighter than the faintest stars a city sky still shows, about magnitude 4.5.
Look for
Start from Kornephoros: Rutilicus is 10° north of it, a fist at arm’s length.
Look for
From 50° north it climbs to 72°; from 35° north it climbs to 87°; from the equator it climbs to 58°; from 35° south it climbs to 23°.
Science
Rutilicus’s surface is about 6,200 K, some 400 K hotter than the Sun’s 5,772 K, so its light is strongest at about 470 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 2.7, about as bright as Ruchbah looks to us.
Did you know
Against Kornephoros, the brighter star the hop starts from: the two look about as bright as each other in our sky; Kornephoros is 139 light-years away and Rutilicus 35 light-years, so side by side Kornephoros would give off 16 times as much light as Rutilicus.
Science
Rutilicus is the 9th nearest to us of the 156 stars on these pages with a measured distance. Its nearest neighbour among them in space is Vega, about 16 light-years from it; on our sky the two are 25° apart.
Look for
The Sun passes 53° south of Rutilicus around late November, when it is highest at noon, in daylight: the weeks either side are its worst time of year. From 50° north it is above the horizon for about 18 hours a day, from 35° north about 15 and from 35° south about 9. It is 40° from the plane of the Milky Way.