The Event Horizon Telescope has shown us the first picture of the light shadow of the supeemassive black hole in the center of the Milky Way, Sagittarius A*!

It's maybe a bit surprising that they could publish the black hole in another galaxy, M87*, three years before that in our own Milky Way, but that is because even though M87 is much further away, its central black hole is absolutely massive - more than 1000 times heavier than the one in the Milky Way.

The event horizon (also called Schwarzild radius) of M87* ("M-eighty-seven-star"), which is a good deal smaller than the light shadow which we can see in the EHT images, is 2.5 times the orbit of Pluto. Which gives it an average mass density of 2-3% of the air we breathe on Earth!

Such gargantuan black holes fly in the face of all we learned about black holes as kids. Remember "spaghettification" - that you'd be torn apart to atoms by the tidal forces as you approached a Black Hole? Well, at the event horizon of M87*, the tidal forces are weaker than those of the Sun in Earth's orbit!

...Which is to say that if you could survive the radiation (you could not!) at its event horizon, you could drift gently through it in almost-zero gravity and be none the wiser! Pretty darn far from the way it works in black holes with masses of "only" a few massive stars!


In comparison to this, the Milky Way black hole presented today by weighs 1000 times less, "only" the same as 4.5 million suns. That makes a huge difference to its properties!

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