Crown of the Scorpion

An approximate line of three stars in the northwestern parts of Scorpius, representing the head and outstretched pincers of the Scorpion. The Crown lies between the star Antares to the southeast and the constellation Libra in the northwest. The stars that today comprise Libra were traditionally seen as part of Scorpius, describing the outstretched claws of the Scorpion extending out northward and westward beyond its Crown.

The line of stars that forms the Crown runs north to south over a distance of six and a half degrees (or about seven times the apparent diameter of the Moon). The three stars are entirely unrelated to one another, except that they happen to form a linear pattern as seen from Earth. All three belong to the B-type blue spectral classification, but they represent three quite different types of systems.

The brightest of the three is the central star, Dschubba or Delta Scorpii. A rapidly-rotating eruptive variable, Dschubba has recently passed through one of its periodic phases of expelling matter from its equatorial regions, causing it to shine even more brightly than usual.

Under normal circumstances, Acrab to the north is only marginally less bright than the central star Dschubba. The closest of the three stars to the Sun at an estimated distance of 404 light years, Acrab is a complex multiple system composed of two blue stars, each of which has at least one companion star of its own.

Finally, at the southern end of the Crown formation, the line is completed by Fang or Pi Scorpii, which is the most distant of the three Crown stars at some 586 light years. Structurally, it is thought to be a contact binary, a pair of stars orbiting so closely that they physically exchange matter with one another.