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Starts With A Bang —

Messier Monday: The Biggest One of them All, M87

Of all the galaxies in our local supercluster, one outweighs them all.

“I recognize my limits, but when I look around I realise I am not living, exactly, in a world of giants.” -Giulio Andreotti

Each Monday, we’ve chosen one of the night sky wonders that makes up the Messier catalogue, the first accurate catalogue of deep-sky objects easily visible with a small, amateur telescope from Earth. But of all these objects — from star clusters to planetary nebulae, from globular clusters to supernova remnants, and from star-forming regions to entire galaxies — only one can be the largest. Today, that’s exactly what we’re going to shoot for.

Image credit: Tenho Tuomi of Tuomi Observatory, via http://www.lex.sk.ca/astro/messier/index.html.

The vast majority of the deep-sky objects visible from Earth are contained either within the disk or the halo of our own galaxy, and with good reason: closer things appear brighter to us. We’re located on the outer edge of a tendril of our local supercluster, with only a few dozen modest galaxies within tens of millions of light years. But some 50-to-60 million light years distant lies the Virgo Cluster, the most massive and dense cluster of galaxies in our local Universe. And at the very heart of it lies the biggest, most massive galaxy within hundreds of millions of light years of our home: Messier 87.

As dedicated skywatchers try and catch all 110 Messier objects (and you can participate remotely), make sure you don’t miss the biggest one. Here’s how to find it.

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

Following the arc of the Big Dipper’s handle, you’ll arrive at the orange giant star Arcturus, the brightest star in the Northern Hemisphere, and then can continue on to bright blue Spica, which is situated right next to Mars at the present time. But below the “bowl” of the Big Dipper lies the prominent constellation of Leo the Lion, heralded by its brightest members Regulus and Denebola. If you draw an imaginary line from Regulus through Denebola and head towards the space between Arcturus and Spica, you’ll come to the slightly less bright (but still prominent) star Vindemiatrix, and it’s between Vindemiatrix and Denebola you’ll need to look for Messier 87.

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

Most of the stars along that path are invisible to the naked eye, but under relatively clear-and-dark skies, 6 Comae Berenices and ρ Virginis — labelled above — can clearly be spotted. If you draw an imaginary line connecting Denebola to Vindemiatrix and another one connecting 6 Comae Berenices to ρ Virginis, there will be one point where they intersect. And that’s where you should point your telescope.

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

Although there aren’t any bright stars of note in this region, there are a slew of dimmer stars, but also a plethora of faint, fuzzy, extended nebulous regions: the galaxies of the Virgo Cluster. Through long-exposure astrophotography, this region simply sparkles with wonder.

Image credit: Rogelio Bernal Andreo of Deep Sky Colors, via http://www.deepskycolors.com/archive/2009/01/31/virgo-Galaxy-Cluster.html.

And at the heart of the cluster lies its single, most massive galaxy of all: the giant elliptical galaxy Messier 87. Although it didn’t appear so spectacular to Messier himself — when he discovered it in 1781 — we sure do know an awful lot more about it now. That, and we have some images and data that really show us how impressive this behemoth truly is!

Image credit: Rogelio Bernal Andreo of Deep Sky Colors again, via APOD at http://apod.nasa.gov/apod/ap110422.html.

For starters, I want you to think of our Milky Way: a spiral galaxy that’s around 100,000 light-years across, with hundreds of billions of stars, maybe a trillion Suns’ worth of mass, and a couple of hundred globular clusters in its halo. Oh, and a supermassive black hole at the center that, on its own, contains the mass of four million Suns. In the future, our entire local group will merge together, maybe tripling the Milky Way’s current mass, adding hundreds more globular clusters, hundreds of billions more stars and growing our black hole into the tens of millions of solar masses. That’s our far future, when everything that’s gravitationally bound to us merges.

Image credit: NASA, ESA, Z. Levay and R. van der Marel (STScI), T. Hallas and A. Mellinger.

Now, let’s compare that to Messier 87 as it is right now.

Image credit: © 1999-2009 — RC Optical Systems, Robert Gendler, via http://gallery.rcopticalsystems.com/gallery/m87.html.

Messier 87 is a giant elliptical galaxy, the type most commonly found after a series of major mergers of large, Milky Way-like spirals. In the center of the Virgo Cluster, elliptical galaxies dominate, and can reach proportions far larger than their spiral predecessors ever did. How big is “giant,” you ask?

Image credit: © 2006 — 2012 by Siegfried Kohlert, via http://www.astroimages.de/en/gallery/M87.html.

Try half-a-million light-years in diameter, or about five times the extent, in all directions, the longest direction of the Milky Way. Its mass? A whopping two hundred times that of our galaxy today, and about 70 times as great as our entire local group. And as far as globular clusters go? Take a look at this image, below.

Image credit: NASA / Hubble, Wikisky snapshot tool, via Wikimedia Commons user Friendlystar.

Do you see those little “points” distributed through the halo of this behemoth, that look like they could be bright stars? Those aren’t stars at all, but dense collections of hundreds of thousands of stars each, i.e., globular clusters, and there are around 12,000 of them in Messier 87 alone. And finally, did you notice something unique about the center of this galaxy?

Image credit: Brad Bates of Brook Mar Observatory, via http://www.brookmarobservatory.com/M87J_2010.html.

There’s a jet of ionized plasma streaming from the center, spanning 5,000 light-years on its own! What could cause this? Why, a supermassive black hole that dwarfs our own, of course! This is something that becomes apparent if we look in many different wavelengths, as both the X-ray and radio show the telltale signs of an active black hole.

Image credit: NASA / JPL-Caltech / CoolCosmos, via http://coolcosmos.ipac.caltech.edu/cosmic_classroom/multiwavelength_astronomy/multiwavelength_museum/m87.html.

It’s the largest one in our nearby Universe, with an estimated mass of four billion Solar masses, or about a thousand times as massive as our own galaxy’s! The radiation across many different wavelengths coming from its center has been one of the most educational things for astronomy as far as teaching us that these jets, active galaxies and quasars are likely to be different manifestations, magnitude and orientations of the exact same phenomenon: matter being accelerated by a supermassive black hole.

Image credit: NASA and The Hubble Heritage Team (STScI/AURA).

But there’s one way that the Milky Way has this galaxy beat: the amount of dust.

Interstellar dust is made up of neutral molecules capable of blocking light, and our Milky Way has hundreds of millions of Solar masses worth in it. But the intense X-rays emitted by the core of Messier 87 destroys any new dust on timescales of just tens of millions of years; at most, there are only 70,000 Solar masses worth of dusty material in this galaxy at present.

Image credit: Blackwater Skies, via http://www.blackwaterskies.co.uk/2013/09/widefield-in-virgo-cluster-of-galaxies.html.

In the future, as the various galaxies in this cluster merge together, adding on to Messier 87, it will most likely grow to more than ten times its current mass, topping the quadrillion-solar-mass mark in time. It’s the largest galaxy for hundreds of millions of light years, for sure. But it’s got a long way to go before it challenges the record-holder for biggest galaxy in the known Universe!

Image credit: X-ray: NASA/CXC/UCI/A.Lewis et al. Optical: Pal.Obs. DSS; via http://chandra.harvard.edu/photo/2003/abell2029/.

That honor goes to IC 1101, which is nearly three times the extent of Messier 87 in its longest direction, and contains about four times as many stars. But IC 1101 is some twenty times farther away than Messier 87, at over a billion light-years distant.

So when you start to feel like the world is a small place, remember that there are bigger things out there than even our galaxy, and even than the biggest galaxies in our neighborhood. The Universe is full of surprises, wonders, and magnificent stories that it tells us about itself, if only we remember to ask the right questions and listen to its answers.

Image credit: John C. Smith of Hidden Loft, via http://www.hiddenloft.com/M/M87.htm.

And that’s the cosmic story of our supercluster’s greatest galaxy! Have a look back at all our previous Messier Mondays:

And come back next time for yet another; we’re going to get all 110 by the end of the year!

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