Dschubba (Delta Scorpii)
Dschubba (Delta Scorpii) is a star in the constellation Scorpius, magnitude 2.3.
The Scorpion’s forehead — a steady star that flared up in 2000 and changed the shape of Scorpius.
For generations Dschubba was a steady star in the arc of the Scorpion’s head; its name comes from the Arabic for “the forehead of the scorpion”. Then in June 2000 Sebastian Otero noticed it was a tenth of a magnitude brighter than normal. Since then it has climbed to at least magnitude 1.6, altering the familiar look of Scorpius.
The cause is spin. Dschubba is a hot blue-white subgiant turning so fast that it throws off glowing gas from its equator into a disc. That makes it a Gamma Cassiopeiae variable star, like the star at the centre of Cassiopeia’s W. A companion swings around it every 10.5 years on a very elongated orbit, and at its close pass in July 2011 Dschubba peaked again, near magnitude 1.65.
Astronomers once used its spectrum as the standard for its class, but it is now considered too unusual and changeable for the job.
Dschubba (Delta Scorpii) 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?
- Seen through Saturn’s rings. In 1981 Voyager 2 watched Dschubba through Saturn’s rings. Its light was dimmed even in the apparently empty gaps, showing that there is very little empty space anywhere in the main rings.
- A young family. Dschubba belongs to the Upper Scorpius group: thousands of young stars with an average age of about 11 million years.
- The Room. In Chinese astronomy it is Fáng Xiù sān, the Third Star of the Room, an asterism shared with Acrab and its neighbours.
The brightest of the short north–south arc of stars west of Antares that marks the Scorpion’s head. Since 2000 it has brightened unpredictably, so compare it with Acrab just to its north and with Antares.
When and where to see it
It is best placed in the evening sky around June, when it crosses the meridian at about 10 pm local time (around midnight in May). It can be seen from everywhere south of 67°N and never sets south of 67°S.
At its highest it stands 17° up from 50°N, 32° up from 35°N, 67° up from the equator, 78° up from 35°S.
Facts
- Type
- Star
- Constellation
- Scorpius
- Designations
- Delta Scorpii, δ Sco, 7 Sco, HR 5953, HD 143275, HIP 78401
- Magnitude
- 2.3
- Position
- RA 16h 0.3m, Dec −22° 37′ (J2000)
- Spectral type
- B0.3IV
- Colour
- blue-white (B−V -0.12)
- Distance
- 490 light-years
- Discovered
- Sebastian Otero, 2000, Known since antiquity; Otero spotted its outburst in June 2000
Open AstroPilot to see when Dschubba (Delta Scorpii) is highest tonight from your location, how easy it is with your telescope or binoculars, and an eyepiece view.