Messier Monday: A Bright, Close Delight of the Winter Skies, M34

"The deeper reason we fear our own glory is that once we let others see it, they will have seen the truest us, and that is nakedness indeed. [...] It is an awkward thing to shimmer when everyone else around you is not, to walk in your glory with an unveiled face when everyone else is veiling his." -John Eldredge

Welcome back to another Messier Monday, where the glittering wonders of the night sky -- visible to anyone at the right latitudes with even simple equipment -- are on display for everyone. The bright collection of 110 deep-sky wonders include star clusters, globular clusters, galaxies, as well as star-forming regions and nebulae, and represent some of the most easily spotted natural wonders of the Universe. As the seasons transition, a whole new set of objects becomes visible in the early night sky.

Image credit: Johnson Space Center Astronomical Society (JSCAS) members.

For today, let's focus on one of the closest, brightest open clusters in the night sky, flying high over the eastern horizon (or just north of it) after the skies darken tonight. Although the bright Moon may make it difficult to look in on many extended objects tonight, the open cluster Messier 34 still makes for a fantastic target under otherwise dark skies, even with the naked eye! Here's how to find it.

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

Some of the most prominent stars in the entire Northern Hemisphere can be found over the eastern horizon or just to the north of it, including the (currently low-flying) very bright stars Capella and Aldebaran, the familiar and high-flying "W" of Cassiopeia, and the line of four prominent, bright stars (Mirphak, Almaak, Mirach and Alpheratz) straddling the constellations of Perseus and Andromeda.

Just below the imaginary line connecting Mirphak to Almaak, that's the region we need to peer into to find Messier 34.

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

Below the imaginary line connecting Mirphak to Almaak is the bright, prominent star Algol. If you look in the vicinity of Mirphak towards bright, blue Algol, you'll see a rough "line" of stars that appears to have a kink towards the end. The last star labeled above in that kink, 16 Persei, is clearly visible to the naked eye even in light-polluted skies. But instead of continuing on from that imaginary line of five stars, if you hook around back towards Mirphak instead, you'll see two dimmer (but still naked-eye) stars, 12 Persei and 14 Persei; Messier 34 lies between them.

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

Although none of the individual stars in M34 are bright enough to be visible to the naked eye, the entire cluster -- visible as a faint, fuzzy object -- can be seen in a clear, dark sky. At more than half-a-degree wide, or just over the size of a full Moon, this is one of the more prominent open star clusters visible from Earth. And through a telescope or pair of binoculars, there's quite a lot to be seen.

Image credit: Dick Miller, via http://www.dickmillerimages.com/.

Yes, you can easily resolve the individual stars, as Messier himself did, noting that M34 was a

Cluster of small stars, between the head of Medusa (Algol) & the left foot of Andromeda, a little below the parallel of Gamma [Andromedae]...

but there's so much more to be seen than just individual stars.

Image credit: © 2006 - 2012 by Siegfried Kohlert, via http://www.astroimages.de/.

Colors, for one! The bright blue glow of the brightest members tells us that this is a relatively young star cluster, while the lack of dusty nebulosity tells us that it isn't too young. In reality, all star clusters have star color-and-magnitude combinations that trace out a specific pattern if you plot them; this pattern is known as their Hertzsprung-Russell diagram. The main line -- from lower right to upper left -- that the stars follow is known as the main sequence, and where the stars appear to turn off of it (by heading towards the upper right) allows us to date the age of each cluster.

Image credit: Mike Guidry, University of Tennessee, via ATNF / CSIRO.

In the particular case of Messier 34, it turns out to be right around 200 million years since its formation, although estimates range from 180 million all the way up to 250 million. Why? It's not just the bright blue stars that are there; it's a combination of the ones that aren't there and the red giants that are, or heavier, brighter, bluer stars that have burned up the hydrogen in their core and evolved off that main sequence.

Image credit: Digitized Sky Survey (DSS) image, via Courtney Seligman of http://cseligman.com/.

One of the more interesting things about Messier 34 is that it's so close; of all the objects (not counting mistakes) in the Messier Catalogue, there are only five objects that are closer! At a distance of only 1,500 light-years, it's been relatively easy for our most advanced equipment to reveal the intrinsically dimmer, fainter stars inside, something that's helped us to learn a tremendous amount about not only this object, but about star clusters in general.

Image credit: REU program / NOAO / AURA / NSF; zoom by me.

There are plenty of low-mass stars in this cluster; it's expected that the total number of objects that qualify as "stars" is somewhere around 500, all told, but there's something very interesting about the lower-mass stars in this cluster.

In fact, there's something very interesting about the lower-mass stars in all recently formed star clusters: they are not yet on the main sequence!

Image credit: Pearson Education / Addison Wesley.

You see, while it's true that higher-mass stars "turn off" the main sequence when they're done burning their core hydrogen, the lower mass stars actually take a very long time to drop in their initial luminosity enough in order to find the main sequence in the first place; they need to drop down to it! Even a cluster 200 million years old (give or take) like M34 hasn't lived for long enough for stars less than about half our Sun's mass to reach the main sequence yet, and it will be hundreds of millions of years more before they do!

So while there are 19 known white dwarfs, or stars that have already burned all their core hydrogen, become red giants, blown off their outer layers and contracted down to a degenerate object, a full half (if not more) of the stars in M34 haven't even reached their equilibrium hydrogen-burning state yet! And at the same time, these stars -- having formed some 4.3 billion years after our own Sun formed -- offer something our Solar System doesn't.

Image credit: Sloan Digital Sky Survey (SDSS). Bonus points if you see the elliptical galaxy.

Having formed later in the Universe, these stars have more heavy elements than we do; some 17% more iron, carbon, oxygen, and most of the other measurable elements (except nickel, for some reason) than our Sun does. So any worlds forming around these stars might have some particular interesting and unique chemistry happening on them, and may be even more likely to have the seeds of life on them than worlds that formed at the same time as Earth!

And that will bring us to the close of another Messier Monday. Including today's entry, we've looked at the following objects so far, a full 52, which means we've been doing it every Monday for a year now:

• 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
• M34, A Bright, Close Delight of the Winter Skies: October 14, 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
• M75, The Most Concentrated Messier Globular: September 23, 2013
• M77, A Secretly Active Spiral Galaxy: October 7, 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
• M103, The Last ‘Original’ Object: September 16, 2013
• M104, The Sombrero Galaxy: May 27, 2013
• M108, A Galactic Sliver in the Big Dipper: July 22, 2013
• M109, The Farthest Messier Spiral: September 30, 2013

Come back next week, where another deep-sky wonder awaits you, only here on Messier Monday!