The head of Scorpius

The brightest star near Antares is Delta Scorpii, now in its 19th month of an unexpected flareup. Photographs don't show the brightness differences between stars well, but to the naked eye Delta is obviously the brightest star in the nearly vertical row of three forming the head of Scorpius.

Photo by Jimmy Westlake.

Most skywatchers think of Scorpius as a summer constellation (in the Northern Hemisphere), but early risers get a preview of the Scorpion climbing the southeastern sky before dawn during winter. It's there right now — and it doesn't look normal. The star Delta Scorpii remains unusually bright, more than a year and a half after beginning an unexpected flareup.

One of the many independent "discoverers" of Delta Scorpii's outburst is Michael D. Hardy of Mesa, Arizona. On the morning of December 26th, he writes, "I happened to look over toward the southeast toward Antares and the three stars that form Scorpius's head — Beta, Delta, and Pi Scorpii. And that is when the problem started. It seemed to me that Delta was unusually bright compared to the rest. It was not as bright as Antares but not that inferior to it."

Delta usually shines at magnitude 2.3 but has slowly fluctuated to as bright as 1.8 since July 2000. In just the last few days naked-eye estimates put it around magnitude 1.7 or 1.6, its brightest yet.

Delta Scorpii is a hot giant star of spectral type B0. It is apparently following in the venerable footsteps of Gamma Cassiopeiae, the prototype of the Gamma Cas category of variable stars. Gamma Cas, also a B0 star, brightened from about magnitude 2.25 to 1.6 in 1937 and remained near this peak for many months. It then dwindled to magnitude 3.0 during the next three years, then took more than 15 years to brighten back to normal. Both Delta Sco and Gamma Cas are rapidly rotating stars that are evolving off the main sequence and occasionally flinging mass from their equators.

Northern Hemisphere observers can go out and take a look at Scorpius in the south-southeast around the time when your morning twilight begins, about an hour and a half before sunrise. Observers south of the equator can see Scorpius rising after midnight. Compare Delta's brightness to Beta Scorpii, magnitude 2.6, and Antares, magnitude 1.1.

Use our interactive sky chart to point the way to Scorpius in the morning sky. Choose whichever link is most appropriate to your location:

You can find your local start-of-twilight and sunrise times right here using our almanac page. You can also customize the sky chart for your location.


You must be logged in to post a comment.