Tuesday, 2 May 2017

Virgo A

The Virgo supercluster is a gigantic accumulation of galaxies that not only contains the large, central Virgo-Coma Berenices cluster but also about a hundred other galaxy groups. Also the group to which our own Milky Way belongs, together with e.g. Andromeda and Triangulum, is gravitationally bound to the Virgo supercluster. Its centre lies approximately 65 million lightyears away from us and exactly there we find this enormous galaxy, called M87. It belongs to the older group of elliptical galaxies and as such doesn't display any spiral arms anymore. Actually, it's not even a disk but nearly a perfect sphere, the outer halo of which extends up to a diameter of half a billion lightyears! In comparison, our Milky Way's only 100 million lightyears across. Where our galaxy's accompanied by about 200 globular clusters, there are at least 12.000 orbiting M87! Its mass is estimated at 2 to 3 trillion solar masses! 

Okay... are you still with me? Good. At first sight this magnificent galaxy's not the most interesting for us amateur astronomers because it just looks like a fuzzy patch. No spectacular spiral arms or structures... nothing at all. But as so often, it's the tiny detail that makes all the difference. It doesn't come as a surprise that such a colossal galaxy houses a supermassive black hole in its core. Virgo A is indeed one of the biggest black holes in our part of the known universe - scientists believe it's as big as our solar system, imagine that! - and also one of the most powerful radio and x-ray sources in the sky. Now it so happens that this black hole's responsible for another, strange phenomenon: a huge jet of matter, 5.000 lightyears long, that's being ejected from the galaxy's core. There's actually a second jet on the opposite side, but that one's much more difficult to see and remains invisible to amateur instruments. What I wanted to see, however, was that main jet, so I pushed my binoscope to 507x and concentrated as well as I could. And there it was... I have to say that it was extremely difficult to see using averted vision; the halo around the galaxy's nucleus is so bright that it tends to hide the jet. And yet, there was definitely some sort of streak popping out towards the bottom-left of the core. 

Also interesting to note on the sketch are two very faint and much more distant galaxies near the top-left corner of the field of view: PGC139919 (300 million lightyears away) and PGC41342 (1,3 billion lightyears away) by the edge. Obviously they have nothing to do with giant M87 or with each other and are merely a line-of-sight coincidence.

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