On the next clear, dark night, locate the Scorpion in the southwest sky. Notice anything different? What about the middle star in the row of three forming the head, Dschubba, Arabic for the “Scorpion’s Forehead”? Does it seem somehow odd?

This star is undergoing an outburst. Although it won’t knock your socks off, it has brightened enough to change the look of the constellation. Also known as Delta Scorpii, it is normally at magnitude 2.3 and fourth brightest in the constellation. The star is hot and highly luminous of type B0 and some 500 light-years away. An Argentinean variable-star observer Sebastian Otero was the first to report its slight brightening. Tipped off, astronomers examined the star’s spectrum and found characteristics of a Be star: bright emission lines (hence the suffix “e”) of hydrogen superimposed on a normal absorption spectrum. By the end of July, this star had brightened to magnitude 1.9, close to Sargas, the next brightest star in the Scorpion. Through mid-August, it seems to be holding its own at around magnitude 2.0.

Also known as shell stars, Be stars are rapidly rotating and losing mass to an expanding shell drawn into an equatorial disk. Their brightness fluctuates irregularly with mass transfer to the disk. The prototype of this variable star class, Gamma Cassiopeiae, brightened from magnitude 2.2 to 1.6 in 1937 for several months, fell to magnitude 3.0 by 1940, and took fifteen years to regain its normal brightness. No doubt, something interesting was going on there.

Despite the ease with which you can enjoy Dschubba's show, this event seems to be getting essentially no press. Fair enough. I suppose we expect more entertainment and spectacle. But things changing before our eyes in the starry sky are not often so easily seen and deserve a bit more recognition.

Before Television and the World Wide Web, things were different. Stellar outbursts (supernovae, as we now know) such as Tycho’s and Kepler’s Stars (in 1572 and 1604, respectively) had a tremendous impact on astronomy and science. They demonstrated that the Heavens were not immutable and unchanging. Perhaps the laws that govern motion, light and heat here on Earth apply Up There as well. Maybe we can figure out the Universe afterall. Nothing that big, not a single supernova in this galaxy, has been seen since the invention of the telescope--almost four hundred years.

So a nearby supernova--that would be big news. In 1987, there was good coverage of the supernova in the Large Magellanic Cloud, a satellite galaxy of the Milky Way. Some astronomers today earn their living finding supernovae in other far-off galaxies, or rather constructing telescopic robots that can. Nowadays, they are so thorough and reach so deep that amateur visual search programs can hardly compete.

But the nearness of a Big One in our galaxy would level the playing field, I suspect. As long as you were looking up, you would stand as good a chance as anyone finding one. After all, the 1987 LMC supernova was a visual discovery. Start with Delta Scorpii: How bright and how long will its outburst last? (Magnitudes for nearby comparison stars are noted on the chart above.) Does it outshine Shaula, the tip of the Scoporion’s tail? Has it fallen below Zubeneschamali and Zubenelgunubi, the brightest stars in Libra, the Scales? Looking around, who knows what else you’ll find? Maybe you should start looking for a good press agent.

Moondark is written by Doug Miller and published on the web, in the Delmarva Star Gazers'Star Gazer News and in the Delaware Astronomical Society's FOCUS. Please address comments and suggestions to dmiller@udel.edu. This document was last revised on 19 August '00. All text and images copyright © 2000 Douglas C. Miller, All Rights Reserved. This material may not be reproduced in any form without prior permission.