Archive for Galactic Centre

Our own Galactic Black Hole

Posted in The Universe and Stuff with tags , , , , on May 12, 2022 by telescoper

As I mentioned a while ago the Event Horizon Telescope team held a press conference this afternoon and to nobody’s surprise they used it announce an image of the (shadow of the event horizon around the) black hole at the centre of the Milky Way.

Here it is:

You can read the full press release here.

You may recall a great deal of excitement about three years ago concerning the imaging of the “shadow” of the event horizon of the black hole in the centre of the galaxy M87. The question I was asked most frequently back then is that there’s a much closer black hole in the centre of our own Galaxy, the Milky Way, so why wasn’t that imaged first?

It it true is that the black hole in the centre of M87 is ~103 times further away from us than the black hole in the centre of the Milky Way – known to its friends as Sagittarius A* or SgrA* for short – but is also ~103 times more massive, so its Schwarzschild radius is ~103 times larger. In terms of angular resolution, therefore, the observational challenge of imaging the event horizon is similar in the two cases. However, in the the case of the Milky Way’s black hole the timescales involved are much shorter than in M87 and there is a greater level of obscuration along the line of sight. That’s why it took longer to produce the image.

It’s a very difficult observation of course and I’m not sure of the significance of the “lumps” you can see, but the dark region in the centre is what the image is really about and that seems to be exactly the predicted size. The resolution is about 20 microarcseconds. Congratulations to the Event Horizon Telescope team!

If you’re interested in learning more about how this image was made I recommend this short video:

The Complex Heart of the Milky Way

Posted in Art, The Universe and Stuff with tags , , , on January 26, 2022 by telescoper

I couldn’t resist sharing this amazing radio image of the Galactic Centre made using the South African MeerKAT radio telescope:

Radio frequency electromagnetic radiation is able to penetrate the dust that permeates this region so can reveal what optical light can not. In particular you can see the very active region around the black hole at the centre of the Milky Way, bubbles caused by exploding stars and – most interesting of all – a number of magnetized filamentary structures.

It’s an extraordinarily beautiful picture made from a mosaic of 20 separate observations. In fact I like it so much I’ve cross-filed it in my “Art” folder. Those of us who work in astronomy or astrophysics are wont to say that there’s much more to it than pretty pictures, but when one like this comes along we’re all sure to geek out over it!

For more information about this image at the science behind it, see here.