Much of our discussion
around the feeding of black holes has revolved around stars,
the snack of choice for Stellar-mass black holes, gurume.
Since Stellar-mass black holes make up the majority of
binary pairs we associate with Stellar companions,
what do you think a supermassive black hole likes to snack on?
Well, if you were thinking surely they also eat stars,
you'd be correct, but they are also
voracious consumers of the gas and dust that happened to fall into close.
Some of the most spectacular phenomenon theorized to occur in the environment
around a supermassive black hole are called tidal disruption events.
These feeding frenzies are so violent that
the stars being consumed are completely torn apart.
During a tidal disruption event,
stars passing close to a supermassive black hole are
disrupted by the strong tidal forces of the black hole's gravitational field.
The tidal forces deform the star into a long string of hot glowing gas,
just like this artist's impression of what a disrupted star might look like.
Astronomers can detect these tidal disruption events as
a sudden increase in the brightness of light around the black hole.
However, direct imaging of these disruptions is not yet possible,
which is why we only show an artist drawing here.
The gas from a destroyed star then accretes onto the disk of
the supermassive black hole feeding its insatiable appetite.
This effect was used in the Doctor Who episode, The Impossible Planet,
when the Scarlet system which was home to the Baluchi
was drawn out into a red cloud before being accreted onto a black hole.
Supermassive black holes can feed on stars,
but the gas that the black holes devour doesn't have to come from a disrupted star.
Are there other options?
What about clouds of dust and gas?
The centers of galaxies can be pretty messy after all.
Astronomers are puzzled by the sheer size of supermassive black holes.
The mass of their interiors came from somewhere, and until recently,
scientists thought that supermassive black holes feed on a steady diet
of hot ionized gas from the halo of the galaxy.
Similarly, supermassive black holes can feed on cold molecular gas clouds,
sometimes the remnants of ancient supernova explosions.
In this case, the food is more like a soup with lumpy noodles and vegetables in it.
In this image, the supermassive black hole is hidden away in
the center of the galaxy in the cluster ABEL 2597,
which is shown as blue light in this image.
The red blobs show the location of cold clouds of molecular carbon monoxide gas.
When a lumpy carbon monoxide chunk is consumed by a black hole,
it temporarily blocks the light emitted from the accretion disk and
jets like the black blob in the inset of this image.
All of this food talk is giving me indigestion,
I hope I don't, excuse me.
Supermassive black holes are not the most eloquent of dinner guests either.
Not only do they demand more,
they don't care whether you serve them
a delicious apple pie made from scratch or a pile of rocks.
While they do clean up after themselves,
we can all agree that they need to work on their manners.
No one is going to sit at a table with a supermassive black hole.
We've also learned that the jets of a black hole are
hot gases being accelerated into interstellar space,
this is like a black hole burping.
While gas flows inwards towards the black hole,
the material and energy can be thrown out in the form of powerful relativistic jets.
On closer inspection, astronomers have also found that supermassive black holes can also
eject gas from the region even closer to the event horizon.
Here, we see the Whirlpool Galaxy,
a beautiful example of two colliding galaxies.
The smaller galaxy visible in the inset has a bright X-ray source visible in blue,
which indicates the presence of a supermassive black hole.
The blue arcs and bands are
hot glowing gas being ejected from the region around the black hole,
this is evidence of black holes burping.
Excuse me, again.
How rude?
We have a supermassive black hole at the center of our own galaxy, Sagittarius A*.
I wonder what its favorite foods are.
Sharon MorsinkAssociate Professor
