As a follow-up to my last post on Antares, Mars, and Saturn, I decided to see whether I could still find them in the early evening twilight last night (Tuesday, September 16). Sure enough, all three were easy to find in the southwest sky at about 7:40 pm CDT, even though the sky was not yet totally dark.
Right next to Mars was a little blue star that I did not expect to see. What was that star? The color difference between Mars and that star was striking. I had to check a star chart to find out.
The little blue star is Dschubba (such a great name), otherwise known as Delta Scorpii. The name Dschubba is from the Arabic word for forehead (in this case, of the scorpion). Dschubba is the fourth brightest star in the constellation of Scorpio. The brightest star in Scorpio is Antares. Look for little blue Dschubba tonight or tomorrow night just below and to the right of Mars.
Note the color difference between Dschubba and Mars, and also note the color difference between Dschubba and Antares (to its left). Blue stars such as Dschubba are much hotter than red stars such as Antares; the color tells us something about the temperature of the star.