“When you look at the stars and the galaxy, you feel that you are not just from any particular piece of land, but from the solar system.” –Kalpana Chawla
Welcome to this week’s Messier Monday, where I pick a new object out of the original catalogue of 110 “faint fuzzies” designed to help comet-hunters avoid confusion with these fixed, extended night sky objects.
In previous weeks, we’ve focused on a variety of objects, including a globular cluster, an open star cluster, a supernova remnant and an active star-forming nebula. Yet the largest, grandest and most spectacular of Messier objects has not yet been represented in our series so far: the galaxies.
This week, I’d like to introduce you to a very special galaxy, Bode’s Galaxy (or Messier 81), which has the distinction of being the very first galaxy outside of the Milky Way I ever found for myself. Here’s how to do it.
Although the December Solstice is fast approaching, meaning that the Big Dipper is at its worst for visibility in the early parts of the night, the Northern Hemisphere still gets good views of at least the “cup” of the dipper during nearly all parts of the night.
And if you can find the “cup” of the Big Dipper, you can find where Bode’s Galaxy (or Bode’s Nebula) is. Draw an imaginary diagonal line from the inside bottom star (Phecda) towards the outermost tip of the cup (Dubhe), and then move again the same distance in almost exactly the same direction.
Under ideal conditions (ideal human eyes, ideal darkness), it’s the farthest object visible to the naked human eye. Through even a small telescope or decent binoculars, you won’t be able to miss what appears to be a bright, stationary cloud in the night sky. (The smaller, cigar-shaped one is a Messier object for a different Monday!)
But through even a reasonably large amateur telescope with rather simplistic software, the detail inherent in the galaxy is exquisite. As far as galaxies go, this is one of the most interesting, close-by ones in the entire sky! (Rob Knop and I have a history with it, too.)
Yes, it’s big and bright: at just 12 million light years away, it dominates its own galaxy group: the M81 group, and has a brilliant core, some large extended spiral arms, with that pink evidence of star formation written all over it.
But there’s so much more. First off, the reason its arms are so wispy, extended and pink is because Messier 81 is an interacting galaxy: gravitationally disrupted by its neighbors and characterized by cosmic violence. This Hubble Space Telescope image captures this exquisitely.
Because of how powerful Hubble is, the full-size image (>300 MB; watch out!) contains remarkable detail in each tiny component of the image above. A tiny sample is available below.
But this galaxy hasn’t just been imaged in the visible portion of the electromagnetic spectrum. At shorter, more energetic wavelengths, the Ultraviolet light (shown in blue) characterizes regions of current star formation, while the X-rays (shown in purple) reveal that the core of this galaxy is in fact active, as its central, supermassive black hole feasts on the surrounding material!
Its central black hole is maybe 20 times as massive as the one the Milky Way has, weighing it at 70 million times the mass of our Sun. It’s also the most distant large galaxy to actually be blueshifted, or moving towards us. This will not continue, mind you, as the entire M81 group is still receding from our local group. As the takeover of Dark Energy continues, the entire M81 group will eventually disappear from our sky, although it may be the final galaxy group to do so in our Universe.
We can also find some amazing things if we look at longer wavelengths, or at this galaxy in infrared light.
The red colors, above, indicate heated dust in the interstellar medium, where stars may form in the future, and the green hues are evidence of polycyclic aromatic hydrocarbons, which may be the original organic building blocks for the life we know on Earth.
No matter how you look at Messier 81, it’s guaranteed to give you an impressive window into just one galaxy out of the hundreds of billions in our Universe.
Stars are forming, the central black hole is active, a merger is forthcoming and somewhere, 12 million light years away, the primordial ingredients for life are coming together. Someone from that galaxy looking at Earth would be able to find the first apes, but nothing that had even begun to resemble a human being.
When we look out at these Messier objects, we are always looking backwards in time. But the galaxies — the most distant of the Messier objects — provide the greatest window back into the Universe of all. If you’ve never seen one, grab a pair of binoculars and look for them some night: you’ll never forget seeing a galaxy with your own eyes for the first time!
So, including today’s entry, we’ve covered five of the 110 Messier objects so far:
- M1, The Crab Nebula: October 22, 2012
- M8, The Lagoon Nebula: November 5, 2012
- M15, An Ancient Globular Cluster: November 12, 2012
- M45, The Pleiades: October 29, 2012
- M81, Bode’s Galaxy: November 19, 2012
Which one will be next? Join me each Monday for a new one, and suggest your ideas below! (I have been known to listen, sometimes.) We’ll have a new Messier object — and a new window into the night sky — waiting for you to discover!