Messier Monday: The Wild Duck Cluster, M11

esiegel — Mon, 09 Sep 2013 16:34:50 +0000

"Being born in a duck yard does not matter, if only you are hatched from a swan's egg." -Hans Christian Anderson

Welcome back for another Messier Monday! There are 110 deep-sky objects in the Messier catalogue, some of the most prominent night-sky fixtures, as seen from Earth, running the gamut of astronomical phenomena from within our galaxy and beyond. Each week, we pick a new one to place under the spotlight, examining what it is, what we know about it, and how to find it, among other spectacular facts.

Image credit: Rolando Ligustri, taken over many years, retrieved from http://www.itelescope.net/.

This week, we're taking a look at one of the most prominent star clusters in all of the night sky: the Wild Duck Cluster, Messier 11. If you look towards the southern part of the sky after sunset, you'll be able to find this gem, located right in the plane of our galaxy.

Image credit: me, using the free software Stellarium, via http://stellarium.org/.

Looking low above the southern horizon shortly after sunset, you might recognize the teapot asterism in Sagittarius. Looking high above the horizon, you'll see the familiar Summer Triangle, with Altair coming closest to the southern horizon. And if you've got dark enough skies after the Moon goes down, you'll even see the disk of the Milky Way form a line connecting the triangle with the spout of the teapot.

If you want to find Messier 11, look halfway between Altair and the teapot, and there will be some stars to help guide you.

Image credit: me, using the free software Stellarium, via http://stellarium.org/.

The blue star, λ Aquilae, is an unspectacular star as seen from Earth, but it outshines all the others in its vicinity. Just slightly to the southwest of it, you can see another prominent star, 12 Aquilae, and then yet another, η Scuti. Head just a little farther in the same general direction, and you won't be able to miss a bright, fuzzy collection of stars: that's Messier 11, the Wild Duck Cluster.

Image credit: me, using the free software Stellarium, via http://stellarium.org/.

What would this look like with an actual, wide-field astrophotography setup? Thanks to Stephen Rahn, you can see for yourself!

Image credit: Stephen Rahn, via Google+.

That fuzzy guy in the middle of the photo above is Messier 11, and it's actually -- though just barely -- visible to the naked eye. Of the open star clusters visible from Earth, this is one of the most compact, densest, and richest of them all!

Image credit: Dean Jacobsen of http://www.astrophoto.net/.

Open star clusters form from the collapse of a molecular cloud of gas, typically form a few hundred to a couple thousand stars, then gravitationally dissociate over a time period of a few hundred million years to a billion years or so.

Well, Messier 11 is definitely on the heavy side of this!

Image credit: Bernhard Hubl of http://astrophoton.com/.

With at least 2,900 stars inside and at a somewhat advanced age of 220-250 million years, this is known as the Wild Duck Cluster because the brightest stars, as viewed through a low-power telescope, appear to take on the V-shaped silhouette of a flock of flying ducks!

In reality, a close-up shows a much more complicated structure to the stars inside.

A rich mix of blue, yellow and red stars lie inside, with the blue and yellow ones shining most brightly. This is another particular difficult cluster to count the exact number of stars in, as it's difficult to tell what's a background star from the galactic plane and what's a dimmer, redder star that's natural to the cluster.

But the bright yellow-and-red ones are giant stars: stars that have run out of hydrogen fuel in their core and have expanded to become giants, much like our Sun will.

Only, the Sun will take 10-to-12 billion years to do this, while this cluster has only had enough time for most of the B-class stars to run out of fuel in their core. The brightest main sequence star in there -- or star still burning hydrogen -- is class B8, which is the second-faintest B-class star that there is. (The brightest star overall is a rare white giant star, a temporary stage in the life of a dying red giant star!)

There are also some 82 variable stars in this cluster, which helps us learn about its properties like its distance, age and evolution.

Image credit: Adam Block / NOAO / AURA / NSF.

It's about 6,000 light-years away from us, which is a pretty large distance for an open cluster; in fact, it's the most distant open cluster in the entire Messier catalogue that's still visible to the naked eye!

Image credit: Jean-Charles Cuillandre (CFHT), Hawaiian Starlight, CFHT.

The first Hubble images of this object were only taken last month, and as such, they're not yet available. (Unfortunately!)

But if we can get some good resolution images, you can see beyond the brightest stars that all seem to blur together, and the rich, dimmer stars that will continue to shine long after the brighter ones burn out.

Image credit: WikiSky, via http://tinyurl.com/messier11-Wiki.

In the infrared, the cooler, redder stars shine far more brightly, and many more become prominently visible, as this 2MASS image shows.

Image credit: Two-micron All-Sky Survey (2MASS), mosaic credit S. Van Dyk (IPAC).

The best-resolution look inside this cluster I've seen comes from Jim Misti, where you can really see the detail of what lies behind the brightest stars in this cluster. As you can note for yourself, it seems like the only limit to the number of stars we see is how long of an exposure we're willing to take!

Image credit: Jim Misti of Misti Mountain Observatory, via http://www.mistisoftware.com/.

Over the next few hundred million years, these stars will fly apart due to gravitational interactions, the bluest ones will run out of fuel, become giants, and die in planetary nebulae/white dwarfs, while the lower-mass ones will eventually become strewn about our galaxy, becoming nothing more than ordinary, nondescript stars that live in the Milky Way's disk: the fate of all open star clusters!

And that will wrap up another Messier Monday! Including today’s entry, we’ve taken a look at the following Messier objects:

M1, The Crab Nebula: October 22, 2012
M2, Messier’s First Globular Cluster: June 17, 2013
M5, A Hyper-Smooth Globular Cluster: May 20, 2013
M7, The Most Southerly Messier Object: July 8, 2013
M8, The Lagoon Nebula: November 5, 2012
M11, The Wild Duck Cluster: September 9, 2013
M12, The Top-Heavy Gumball Globular: August 26, 2013
M13, The Great Globular Cluster in Hercules: December 31, 2012
M15, An Ancient Globular Cluster: November 12, 2012
M18, A Well-Hidden, Young Star Cluster: August 5, 2013
M20, The Youngest Star-Forming Region, The Trifid Nebula: May 6, 2013
M21, A Baby Open Cluster in the Galactic Plane: June 24, 2013
M25, A Dusty Open Cluster for Everyone: April 8, 2013
M29, A Young Open Cluster in the Summer Triangle: June 3, 2013
M30, A Straggling Globular Cluster: November 26, 2012
M31, Andromeda, the Object that Opened Up the Universe: September 2, 2013
M33, The Triangulum Galaxy: February 25, 2013
M37, A Rich Open Star Cluster: December 3, 2012
M38, A Real-Life Pi-in-the-Sky Cluster: April 29, 2013
M40, Messier’s Greatest Mistake: April 1, 2013
M41, The Dog Star’s Secret Neighbor: January 7, 2013
M44, The Beehive Cluster / Praesepe: December 24, 2012
M45, The Pleiades: October 29, 2012
M48, A Lost-and-Found Star Cluster: February 11, 2013
M51, The Whirlpool Galaxy: April 15th, 2013
M52, A Star Cluster on the Bubble: March 4, 2013
M53, The Most Northern Galactic Globular: February 18, 2013
M56, The Methuselah of Messier Objects: August 12, 2013
M57, The Ring Nebula: July 1, 2013
M60, The Gateway Galaxy to Virgo: February 4, 2013
M65, The First Messier Supernova of 2013: March 25, 2013
M67, Messier’s Oldest Open Cluster: January 14, 2013
M71, A Very Unusual Globular Cluster: July 15, 2013
M72, A Diffuse, Distant Globular at the End-of-the-Marathon: March 18, 2013
M74, The Phantom Galaxy at the Beginning-of-the-Marathon: March 11, 2013
M78, A Reflection Nebula: December 10, 2012
M81, Bode’s Galaxy: November 19, 2012
M82, The Cigar Galaxy: May 13, 2013
M83, The Southern Pinwheel Galaxy, January 21, 2013
M86, The Most Blueshifted Messier Object, June 10, 2013
M92, The Second Greatest Globular in Hercules, April 22, 2013
M94, A double-ringed mystery galaxy, August 19, 2013
M97, The Owl Nebula, January 28, 2013
M99, The Great Pinwheel of Virgo, July 29, 2013
M102, A Great Galactic Controversy: December 17, 2012
M104, The Sombrero Galaxy: May 27, 2013
M108, A Galactic Sliver in the Big Dipper: July 22, 2013

Come back next week, where we'll have another object for you to find and enjoy in the night sky, and another great cosmic story to tell. Happy Messier Monday!

esiegel Mon, 09/09/2013 - 12:34

messier 11

Messier Monday: The Wild Duck Cluster, M11