Discovering Dschubba

Dschubba is a star system located 400 light years away from Earth, visible in the constellation of Scorpio.

Although Dschubba has been intensively studied, it is not yet clear how many stars are part of the system. Observations have confirmed the presence of two stars, but there is evidence for a third and a fourth component. The study of the system is complicated by the high brightness of the two main components, which tend to obscure everything that surrounds them: the primary is in fact 14 thousand times brighter than the Sun, while the secondary almost 3000 times.

The main one is a blue giant 15 times more massive than the Sun and with a radius 5 times that of the Sun, while the secondary one is also a blue star but with 8 solar masses.

The two stars move on orbits that periodically every 10 years bring them very close, to less than 1 AU.

In the early 2000s, the magnitude of Dschubba was +2.3, but by 2003 it had dropped to +1.5, and then slowly returned to its original magnitude in the following years. This sudden increase in brightness was explained precisely on the basis of the orbit of the two stars. It has in fact been supposed that during a close passage the secondary has torn a large amount of material from the photosphere of the primary. The gas would then enter the star’s orbit forming a circumstellar disk, thus increasing the brightness of the system.

Credit: Palomar Observatory.