Spark and Perl go looking
Where is it? I want to see the black hole.
Right there, in the middle of all those stars.
And you cannot see it.
Because it is black?
Partly.
And there is thick dust between us. From the Earth, no light our eyes can see gets out of the middle of our galaxy to us.
Then how does anybody know it is there?
By watching the stars next to it.
They race round an empty spot. One of them, S2, goes all the way round about every 16 years.
Round and round nothing?
Round something as heavy as 4.3 million Suns,
squeezed into a space smaller than Mercury’s path round the Sun.
Will it pull us in?
No. We go round the middle of the galaxy, and it sits right at the middle.
Our Sun takes about 230 million years for one lap.
So we are going round a black hole right now.
Round the whole middle of the galaxy, far away and safe —
as safe as the Earth going round the Sun.
Has anybody ever made a picture of it?
There is one: the ring of glowing gas around it.
Telescopes all over the Earth listened to its radio waves at the same time, and a computer put the picture together.
Not with our eyes, and not with any telescope we could carry.
But you can point at exactly where it is.
Find the Teapot in Sagittarius, the Archer: the middle of our galaxy lies just beyond its spout. It rises for most of the world, and the further south you live, the higher it climbs.
Where the map is clear, this climbs high in the sky. The darker the shading, the lower it stays. Where the map is black, it never comes up. No shading at all: where you live makes no difference.
Space
Which one does not belong?
Read on
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