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Messier Monday: Virgo’s brightest galaxy, M49

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A galaxy very different from our own may hold the key to seeing what our far future looks like.

“We find that we live on an insignificant planet of a humdrum star lost in a galaxy tucked away in some forgotten corner of a universe in which there are far more galaxies than people.” –Carl Sagan

Every Monday on Starts With A Bang is Messier Monday, where we profile one of the 110 deep-sky wonders that makes up the Messier Catalogue. In the 18th Century, there were no accurate, high-quality catalogues of fixed objects in the night sky. Originally designed to assist comet hunters in their quests (to avoid confusion), this is now useful for skywatchers seeking out the brightest and most spectacular views of the Universe visible through pretty much any telescopic equipment here on Earth!

Image credit: Johnson Space Center Astronomical Society, via http://www.kellysky.net/jscas_messiers_draft_10x11.jpg.

On a moonless night (like tonight mostly is), some of the fainter, extended objects whose light is diffusely spread over a larger area of sky are more clearly visible. With the coming onset of spring — if you can brave the cold temperatures — the richest cluster of galaxies rises to prominence in the early part of the night: the Virgo Cluster.

Today, I’m proud to showcase the brightest galaxy in that direction: the giant elliptical galaxy Messier 49. Here’s how to find it.

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

After sunset in the northeastern skies, you should be able to find not only the Big Dipper, but also the bright orange giant Arcturus, which you can locate by following the “arc” of the dipper’s handle. The constellation Leo hovers nearby, and if you move from Arcturus towards Leo, you’ll run into two prominent stars on your way: Muphrid first, very close to Arcturus, and then Vindemiatrix, which is in the constellation of Virgo.

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

If you would continue that imaginary line, from Arcturus to Vindemiatrix, for about another four degrees, you’ll wind up right at Messier 49. But for a little help, there’s another (fainter, but still naked-eye) star that helps point the way: ρ Virginis. If you follow that same path and look (moving a tiny bit south) for the star pattern, below, through either binoculars or a low-power telescope, you should find Messier 49 right in the center.

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

This faint, nebulous and unremarkable fuzzball is not only the brightest member of the Virgo cluster of galaxies, it was the very first galaxy in that cluster discovered, by Messier himself in 1771. He recorded it as a:

Nebula discovered near the star Rho Virginis. One cannot see it without difficulty with an ordinary telescope of 3.5-feet [Foot-Length]. The Comet of 1779 was compared by M. Messier with this nebula on April 22 and 23: The comet and the nebula had the same light. M. Messier has reported this nebula on the chart of the route of the comet, which appeared in the volume of the Academy of the same year 1779.

It’s easy to see why a galaxy like this would, perhaps, be confused with a comet through a small telescope.

Image credit: Gustavo Sánchez/Observatorio Guajataca.

It looks like it has a bright central nucleus that fades away as you move farther outwards, similar to what a comet would look like if it was headed straight towards you.

The difference, of course, is that comets change their positions over time, and brighten or dim as they move towards (or away from) the Sun, while this object has remained stationary and at constant brightness for nearly 250 years since its discovery. You might also be a little surprised at the above image, because when I say “cluster of galaxies,” you probably think of this.

Image credit: © 2014 Scott Rosen’s Astrophotography, via http://www.astronomersdoitinthedark.com/index.php?c=113&p=512.

And this is what the Virgo cluster of galaxies looks like. At least, what a portion of the cluster looks like. You see, the Virgo cluster is the nearest giant cluster to us, with well over 1,000 confirmed galaxies (and probably closer to 2,000). But at a distance of roughly 50-55 million light-years on average, these galaxies span many degrees across the sky.

The main clump of the Virgo cluster is shown above, and indeed, it contains the majority of the cluster’s mass. But about 5 degrees away lies the clump centered on Messier 49, which contains about 10% the mass of the larger, main clump.

Image credit: Ole Nielsen of
http://www.ngc7000.org/ccd/gal-virgocluster.html#m49.

But there are a number of reasons to be excited by this galactic behemoth that dominates its part of the night sky! First, at its distance, it’s the brightest galaxy visible from Earth; no galaxy equally or more distant is as bright to our eyes, even scanning the entire Universe!

Image credit: NASA, ESA, and E. Peng (Peking University, Beijing).

Second, it’s very big: 160,000 light-years across in the direction we can see, although it’s possible that the line-of-sight direction is even larger. In fact, if you trace out the full extent of the galactic edges, it extends for around 800,000 light-years, or about eight times the extent of our Milky Way.

And third, it’s very yellow!

Image credit: David W. Hogg, Michael R. Blanton, and the Sloan Digital Sky Survey Collaboration.

The average color of stars in this galaxy is much redder than even our Sun is, implying that it’s been about 6 billion years or so since the last major episode of star formation graced this galaxy. And finally, as you can perhaps see from the image above, there are a huge number of smaller, satellite objects, including many dwarf elliptical galaxies. Perhaps most impressive is the fact that unlike our own galaxy, which has maybe 150-to-200 globular clusters, Messier 49 has about 6,000!

Image credit: © 2006 — 2012 by Siegfried Kohlert, via http://www.astroimages.de/en/gallery/M49.html.

But you may, looking at images like this, notice a faint trail of debris coming from this galaxy. Indeed, that’s real, and due to the fact that it’s gravitationally interacting — which, for pretty much anything in its clump, means “its future victim of galactic cannibalism” — with a much smaller galaxy!

And things get more and more exciting when we think about the core of this monster.

Image credit: Nicole Peterson, via http://www.calvin.edu/academic/phys/observatory/images/Astr110.Spring2005/Peterson.html.

The nucleus emits X-rays, which are a telltale sign of a central, supermassive black hole. But unlike galaxies like the Milky Way, which tend to have black holes a few million times the mass of our Sun, the one at the center of M49 is over half a billion Suns, at 565 million solar masses!

And finally, long ago — back in 1969 — the lone supernova ever seen in this galaxy went off; it’s been quiet ever since.

Image credit: NASA / Hubble, via Wikisky.

And, as always, the greatest view of Messier 49 comes from the Hubble Space Telescope. It’s difficult to remember, looking at the “fuzz” and haze associated with this galaxy, that it’s made up of stars, and that every faint gradation in brightness is actually due to a greater number of stars.

Have a look through just a slice of this picture at the original, full resolution, and notice the background (and foreground) galaxies poking through the background, and ponder just how many stars must be inside that central nucleus of this behemoth!

Image credit: NASA / Hubble, via Wikisky.

This may very well be what the far future of our own galaxy — after the merger with Andromeda completes — will look like. And with that, we’ll bring today’s Messier Monday to a close! Including today’s object, we’ve profiled the following deep-sky wonders:

Have a favorite you’d like to see? Let us know, either here or over at the Starts With A Bang forum at Scienceblogs!

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