Astro Bob blog: Step into the triangle of delightsBefore it slips away, explore the gems of the Winter Triangle and see across the galaxy.
By: Bob King, Duluth News Tribune
Step into the triangle of delights
The Winter Triangle lies to the east of Orion's three belt stars and high in the south-southwestern sky around 8 o'clock. You'll find the Rosette Nebula not quite one outstretched fist to the left (east) of Betelgeuse. M50 is about the same distance above brilliant Sirius. Photo: Bob King
Several days ago we looked at the peculiar exploding star V838 Mon in Monoceros the Unicorn. You'll recall that this dim constellation is mostly within the confines of the bright Winter Triangle. The Milky Way slices through the region and offers up many fine star clusters and nebulas for binocular and telescope users. Let's take a look at two of the brightest clusters: M50 and NGC 2244 which is at the heart of the beautiful Rosette Nebula.
The amazing Rosette Nebula (NGC 2237) with NGC 2244 at its center recall the petals of a flower surrounding a cluster of stamens. The stars in our featured cluster were recently formed from the nebula's material. When their light switched on it set the hydrogen gas within the cluster's birth cloud to glow. Credit: Frank Barrett
NGC 2244 is a bit less than one outstretched fist to the left of Betelgeuse. Try pointing your binoculars at Betelgeuse and then sweeping due east. You'll soon run into a compact rectangular group of 7th and 8th magnitude stars. Although below naked eye brightness, these are bright enough to be seen individually in typical binoculars. If you think you glimpse a round puff of haze light surrounding the tiny stellar group you're seeing the Rosette itself. This nebula is excited to glow by ultraviolet light from the young stars in NGC 2244. A telescope shows lots of the Rosette's "petals" but its true gorgeousness is revealed only in long exposure photographs that shows curls and folds of hydrogen gas glowing vivid pink in the dazzling light of the central cluster. The cluster is only about 3 million years old -- hardly out of the barn as stars go. Consider that the sun is 4.5 billion years of age and only now reaching middle age.
The Rosette, which contains enough material to make 10,000 suns, and its hatch of newborns (NGC 2244) are about 4,500 light years away. With a diameter of 130 light years, this star-making machine is truly enormous. In comparison the Orion Nebula is only 24 light years wide. Future generations of sky watchers can expect to see new stars appear within this vast nebula that for us are still cocooned in obscurity.
M50 is a bright cluster easily visible in binoculars. It's 3,200 light years away and about 20 light years across. Credit: Ole Nielsen
Our next cluster comes from the catalog of the famous 18th century French astronomer Charles Messier. He discovered M50 in on April 5, 1772 from Paris with a small telescope back when Paris had dark skies. You can see it, too. In my 8x40 binoculars this weekend the cluster was a softly glowing patch of light with a bright little star on its southern edge. I could tease out several additional stars from the haze with close study. M50 is easy to find not quite one fist above Sirius almost in line with Procyon.
This is the galaxy M83 in Hydra and it resembles our spiral galaxy the Milky Way. We can look right into the disk of M83 and see many star-forming regions of pink hydrogen gas studded with clumpy star clusters (blue circles) They're extragalactic versions of the Rosette and Orion Nebulas. In addition I've marked a couple of clusters that have used up the gas in their nebular birth clouds. Credit: ESO
Standing and watching the stars and finding the constellations is an enjoyable activity. Getting to know a few additional characters in the sky like M50 and NGC 2244 adds an extra dimension to our viewing. Star clusters and nebulas are concentrated along the Milky Way because their homes are in our galaxy's spiral arms. The core of the galaxy formed first and used up much of its gas content long ago to create stars. Its home now to some of the galaxy's oldest stars. Later, material in the flat disk condensed to form the star clusters like the Pleiades, Hyades and our featured clusters. When we look into Monoceros our gaze takes us into the Milky Way's spiral arms into regions rich in new star formation.
Tomorrow we'll take a closer look at the Milky Way and another group of star clusters that look radically different from M50 and its ilk.