Astro Bob blog: Fireball update plus a circus act I'd love to seeMore on the fireball plus a surprise from the celestial unicorn.
By: Bob King, Duluth News Tribune
Fireball update plus a circus act I'd love to see
Thanks to the excellent posts from our readers we've learned that Wednesday night's fireball was sighted from Hibbing in northern Minnesota all the way south to Eden Prairie, a suburb of Minneapolis, and near Akeley 100 miles west of Duluth. We received reports from near Carlton, up County Highway 4, Cook County and from the Spooner, Wisconsin area. That meteor really covered some ground!
The fireball was nearly as bright as the moon and widely visible across a path hundreds of miles long traveling from east to southwest. I was just about ready to drive up and down the Blatnik and Bong bridges today looking for suspicious holes in the ice until the Akeley report came in. It's still unclear if fragments fell. Perhaps someone from North Central Minnesota will discover a hole in the roof of their cabin and black rocks on the floor and we can tie the two together. Judging from the enthusiasm of our fireball reporters this was a spectacular sight. I only wish I hadn't been indoors eating my spaghetti dinner at the time.
This map shows the southern sky around 7:30-8 p.m. when Monoceros is well placed for viewing within the Winter Triangle (outlined in blue). Can you see the unicorn? The three stars to the left of Betelgeuse form its head with one star sticking above to represent the single horn. The blue haze is the Milky Way. The star V838 is described below. Created with Stellarium
I did make it out last night for a couple hours under dark, rural skies. The night was spectacular if meteorless. Orion was straight up south during twilight but by nightfall already leaning to the west. Not far east of Orion is a little-known and mostly ignored constellation called Monoceros the Unicorn. That's only because its brightest stars are fourth magnitude which is on the faint side for those of us living in cities and suburbs. Then there's the figure of the unicorn which was clearly designed to tax our imaginations. The best way to see Monoceros (mon-AH-sir-us) is to find the Winter Triangle and imagine a unicorn cantering about within its borders. In the map above, I've connected the faint stars into a "stick" animal. If you live under dark skies consider giving it a try and you'll be counted among the few who've seen this elusive animal. Come to think of it, maybe that's why the stars are so faint in the first place: has anyone ever seen a real unicorn?
Watch the dog-unicorn act the next clear, dark night when Canis Minor the Lesser Dog and its bright star Procyon accompany Monoceros for a romp across the late winter sky. Credit: William Jamieson, Urania's Mirror
What Monoceros lacks in bright stars it more than makes up for in its rich array of star clusters and nebulas. The Milky Way passes this way and like a performer in a parade drops sweet treats for eager sky watchers. I love to swing the telescope into Monoceros and hop from one cluster to the next to pass a pleasant evening.
One of the most remarkable objects ever to appear in the constellation goes by the obscure name of V838 Monocerotis, abbreviated V838 Mon. It was the 838th variable star discovered in Monoceros and unlike many of its kin, a full explanation of exactly what happened there in early 2002 still eludes astronomers. On January 6 that year it appeared as a "new" star or nova. While that's a cool event in itself, it's not extraordinary. Novas happen in close double star systems where one star -- a hungry white dwarf -- pulls material off its companion star and funnels it down to its surface. When enough material accumulates it explodes like a cherry bomb causing the star system to temporarily brighten thousands of times. Nova hunting is a favorite pursuit of a small group of dedicated amateur astronomers and about a half dozen are discovered each year.
V838 Mon (red star at center) and its spectacular light echo taken by the Hubble Space Telescope. To visualize it correctly, imagine you're looking deep within a tunnel toward the star. Credit: NASA/ESA
Everthing changed in February when V838 jumped to within naked eye brightness in just a day! I'd been following the star all along. One night in March when I pointed the scope its way, I was greeted instead by a small cottonwad of fuzz. Was this a new comet? My heart jumped at the thought until I realized that the odds of a comet appearing the exact spot as this peculiar star were frankly astronomical. What I saw was a rare phenomenon called a "light echo". The tremendously fast and brilliant outburst of the star in February sent a huge flash of light into the surrounding interstellar gases -- some of which might have been spewed into space by V838 Mon itself -- lighting them up light a flashlight in the dark as it traveled at the speed of light in our direction. The echo expanded throughout the spring and was still growing (if fading) a couple years later.
The ever-expanding echo of light around the star V838 Mon constantly changed appearance over a matter of months. Credit: NASA/ESA
What ever became of V838 Mon the star? The best explanation seems to be that we witnessed a rare moment in a star's life when it transitions from being a normal star similar to the sun to a red supergiant a thousand times larger. This process normally takes hundreds of thousands of years but we may have been privileged to see it all in a matter of months.
These nights V838 Mon is faint and quiet, and the echo has mostly faded back to darkness. Who knows what magic the unicorn will work next.
Animation of V838 Mon's light echo. Credit: USNO NOFS 1.0m telescope taken January-November, 2002. Animation by Al Kelly and photographs by Arne Henden.