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Starts With A Bang —

Messier Monday: A Spiral Sliver Headed Our Way: M98

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One of the only members of the Virgo Cluster… that isn’t located in Virgo!

“[L]ife is a luminous halo, a semi-transparent envelope surrounding us from the beginning of consciousness to the end.” –Virginia Woolf

Here on Messier Monday, I don’t normally highlight galaxies — the deep space “island Universes” with billions of stars all unto themselves — when the Moon is out, as it’s often difficult to see them. But with the premiere of the new Cosmos yesterday, I can’t help but follow my imagination deep into the Universe, all the way to one of the most unique galaxies out there.

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

Almost all of the galaxies in the Universe are moving away from us, expanding away from one another and from ourselves as space itself expands. The biggest clumps and clusters of galaxies are bound together, however, and swarm in a myriad of directions, like bees in an agitated hive. And the biggest cluster nearest to us is the Virgo Cluster, located some 55 million light years away, and consisting of over 1,000 galaxies. Even at that distance, it’s so big in the skies that parts of it spill over into other constellations, like today’s object: Messier 98.

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

Beneath the Big Dipper, the most identifiable set of seven stars in the northern hemisphere, you can find the prominent star Cor Caroli by following the tip of the handle (Alkaid) and navigating perpendicular to it. Continue on, and you’ll come to Denebola, the second brightest star in the constellation of Leo.

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

If you start at Denebola and navigate in the direction of Arcturus, the orange giant that’s the brightest northern hemisphere star, you’ll arrive at a rather unremarkable naked-eye star, 6 Comae Berenices. But while this faint blue star might be unremarkable to your unaided eye, try training a telescope (or an excellent pair of binoculars) on it, and a whole new world will open up.

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

And by a “whole new world”, I mean that there are three Messier objects located within just a couple of degrees of this star, and many fainter galaxies. If you can find these stars, you can find one of the richer areas of the Virgo Cluster, and just a fraction of a degree back towards Denebola you can find today’s object, Messier 98! Discovered by Messier’s assistant, Pierre Méchain, this nearly edge-on spiral makes an interesting portrait if captured along with the blue star found alongside it.

Image credit: © 2006 — 2012 by Siegfried Kohlert, via http://www.astroimages.de/en/gallery/M98.html.

Remember that the blue star at left is barely visible to the unaided eye, and will disappear from view altogether under typical urban light pollution. I hope that puts into perspective how faint this galaxy is. But while the star in the picture is right around 200 light years away, Messier 98 is 44 million light-years distant. Even with around 70-100 billion stars inside, no wonder it’s so faint at that great distance!

But this is a highly unusual galaxy in a number of ways.

Image credit: NOAO/AURA/NSF, via https://www.noao.edu/image_gallery/html/im0660.html.

For one, even though it’s nearly edge-on — inclined at 74° relative to our line-of-sight — you can clearly see that its spiral arms are highly disrupted, like someone had pulled the outer arms out of the disk’s plane and bent them.

Well, that’s probably right! Its neighbor — the great Pinwheel of Virgo, Messier 99 — located about 1.3 million light years away from it, probably had a close encounter with it just under a billion years ago.

Image credit: Gerard van den Braak of http://www.sterrenwacht.eu/M98-messier.htm.

At some point in the distant future, these two somewhat comparably-size galaxies will merge, likely creating an elliptical galaxy in the process! At least, that will probably happen someday, but not anytime soon. You see, Messier 99 is moving away from us at some 2,400 km/s, but Messier 98 is moving towards us at 142 km/s, one of the most distant large galaxies to be blueshifted.

The gravitational potential well of the Virgo cluster is tremendous, and both of these galaxies are bound to it and each other, but are still moving rapidly. In fact, Messier 98 is one “end” of the central portion of the Virgo Cluster, with Messier 60 as the gateway at the other end!

Image credit: George’s Astrophotography, via http://www.geoandpat.com/.

As for this galaxy itself, it contains an odd mix of barred and non-barred features. With a bright central bulge full of ionized hydrogen, prominent dust lanes that seem to pop out of the galactic plane, tightly wound arms and a fast rotation speed of 236 km/s, it’s still open for debate whether this galaxy is just undergoing star formation at its center, or whether the central ionization is powered by a supermassive black hole.

Image credit: © 2014 Teri Smoot of Star Shadows Remote Observatory, via http://www.starshadows.com/gallery/display.cfm?imgID=421.

An excellent image, like the one above, will highlight that there are actually many faint, small galaxies in this galaxy’s vicinity. That’s what you get in or near the central region an ultra-rich cluster of galaxies like Virgo, and the great galactic pile-up will only get more and more concentrated over time!

Billions of years from now, these galaxies will further merge together and their velocities will level out, and many of the spirals you see here will merge into bigger and bigger giant ellipticals.

But we are not there yet.

Image credit: Bruce Waddington, via http://asterisk.apod.com/viewtopic.php?f=8&t=27624.

In the meantime, enjoy all the beautiful features this wonder of the night sky has to offer, and marvel at not only the young stars lining its disrupted spiral arms, but the incredible, wild future this galaxy has in store! That will bring us to the end of today’s Messier Monday, and if we look back, we’ve already touched on all the following deep-sky wonders:

If you enjoyed it or you have an object you’d like to see next, weigh in at the Starts With A Bang forum over on Scienceblogs. Either way, come back tomorrow for more wonders and joys of the Universe!

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