Mars Doubles Up With Virgo’s Loveliest Double Tomorrow Morning

Tomorrow morning Dec. 29, 2013, Mars will be in conjunction less than a degree south of the double star Gamma in Virgo. You can enjoy the naked eye view or use your telescope to split the star into two equally bright components. The map shows the sky around 6 a.m. CST or 1.5 – 2 hours before sunrise. Stellarium

Mars will slide only 3/4 of a degree south of the striking double star Gamma Virginis tomorrow morning. Also known as Porrima, the close proximity of star and planet will certainly get your attention if you’re willing to risk the winter chill. They’re ideally placed too – high in the southern sky before the start of dawn.

If you have any trouble finding this temporary “double”, just follow the celestial steppingstones of crescent moon, Saturn and Spica to lead you there.

Porrima is a true double star where each component revolves around the pair’s common center of gravity. They complete an orbit in 169 years.   Credit: Damian Peach

Right now, Porrima’s two equally bright stars (both are magnitude 3.6) are separated by 2 arc seconds. To split them apart you’ll need a 3-inch (80mm) or larger scope magnifying around 150x. They’re a beautiful sight – two tiny, close set pearls glimmering in black velvet.

While you’re at it, don’t miss looking at nearby Mars as well as Saturn and the lunar crescent. Heck, they’re all laid out for us like a four-course meal.

Diagram showing the orbit of the secondary companion around the primary star in the Gamma Virginis double. The two were too close together to split in any but the largest telescopes in 2005. Since then they’ve been opening up. Look for the pair to be approximately north-south of one another in your telescope. Credit:

Porrima’s stellar twins are similar to the sun but hotter and nearly identical in size. They go around each other every 169 years in an elliptical orbit that cyclically brings them closer together and farther apart as seen from Earth. Closest approach happened in 2005 when the duo was separated by the same distance Jupiter is from the sun or about 500 million miles. When farthest apart, around the year 2080, they’ll be twice Pluto’s distance from each other.

Right now the duo is “opening up” and easier to see in small scopes, but you’ll need to use higher magnifications. Let us know how you fare.

15 Responses

  1. Yuksel Kenaroglu

    Hi, Bob ! I like your site/blog…
    After reading this article, I would start learning more about “double stars…

  2. Betty Christensen

    I thought I felt a mild earthquake about 5am this morning. Having lived in San Diego,CA for 20 years, I know what it feels like. There was also a boat going out at the same time. Was I dreaming or am I going nuts? Any info? Thanks.

  3. Betty Christensen

    Thanks, Bob. No quakes reported. I’ll blame it on the eggnog. However, the James R Barker departed Duluth entry at 4:40 so that computes. It would have passed here at about 5:00am. . .the time of the (((quake))). Wish I’d checked out the sky!!!

  4. Teamonger

    Hello again Bob. For me, Porrima was Castor in reverse. As a kid in 1971, I had split it fairly easily with my 60mm refractor when the separation was around 5″. Last night I planned to show it to my nieces using my 8 inch Dob, not realizing how the separation had changed over the years. I found it very tough to split, and at first thought my scope had taken a turn for the worst! I gave up on showing it, and my scope seemed back to normal as we went on to other things. Anyway it was quite early in the evening and scope was pointing over rooftops, so poor seeing no doubt played a part.

    1. astrobob

      Yes, it’s still fairly tight but will get easier and easier as the years go by. Looks like about 3″ right now. Since you used an 8″ I think you’re right that seeing played a part in making it so difficult.

  5. Teamonger

    Well measuring with the scale on your chart above, look like it’s just over 2″ right now, will be 3″ by 2020. We fought over Castor’s numbers too, as I recall 🙂

  6. Teamonger

    Well I held a business card up to my monitor to measure your scale. Can’t get more accurate than that!
    Clear skies…

      1. Teamonger

        Well I went out tonight to look again at Porrima again. Seeing still not great, but I was just able to split it at 266x.

        1. astrobob

          I just came in from observing variable stars and planets. I’ve got to remember to give Gamma Vir a look in my 10-inch next time. Thanks for sharing your observation.

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