Welcome! My name is Janine and I'm the creator of Learn the Sky. In this video we're going to
explore the Perseus Cluster which is a group of thousands of galaxies that are located in
the constellation of Perseus. What's really interesting about this cluster of galaxies is
that a singing black hole has been detected here. We're going to explore what exactly that means.
Perseus is a constellation that's fairly easy to point out if you know what to look for. You can see here
this is where the Pleiades is and Perseus is located nearby the pleiades. If you want
to learn more about how to find this constellation, go see that video as well. I also explore a lot of
the different celestial objects that are found in this constellation such as the Double Cluster, the
Alpha Persei Cluster, and the California Nebula. So be sure to check out that video as well.
Our focus is going to be the Perseus Cluster. This is a collection of thousands of galaxies
that's estimated to be 250 million light years away. That means when we're looking at this
particular region, it took light 250 million years for that light to reach us. When you're looking
at Perseus, if we go back here, and point out the pattern, this concentration of galaxies is
located here. It's not something that you would be able to see with the unaided eye all.
The images that we have of this group of galaxies is taken with telescopes that have magnification,
but we can still learn about it and explore it even though we aren't necessarily able to see it.
Here we have another image of what the Perseus Cluster looks like. I love this image because
it combines data from radio telescope; from the Chandra X-Ray Observatory; it takes data from the
Hubble Telescope, in terms of visible light; and then also has infrared data that's all stitched
together in this image. You can see there are lots of galaxies here. This really is
a massive, massive area of galaxies. Of course, in the center, there is a black hole here. So
when we talk about a singing black hole it seems very odd and mysterious. This is something
very recently that I discovered could even exist. It just goes to show you that even though
I've been in studying astronomy for for many, many years there's always new things to learn.
This singing black hole has been detected. Massive black holes can resonate and
the X-ray observations we have of it indicate sound waves. In 2003, the deepest sound of the
universe was detected. The Chandra X-Ray observations of the Perseus Cluster
really showed us these areas of ripples of gas that really indicate sound waves. Now this is not
something we can actually hear because the period of the waves happen over 10 million years. So the
time scale is just much too long for humans to really observe and of course the sound is way too
low for us to hear as well. The sound is 57 octaves below middle c which is way below human range.
It makes it interesting because you would think when I was learning about this I was
thinking, 'Well, why would there be sound if space is a vacuum?' But truly space is not a pure vacuum.
There are stray bits of of matter that are around within the universe. There's gas atoms and there's
dust. That can vary depending on where you are in space. But, with the Perseus Cluster
there is a medium in which the sound waves can travel through. It comes from the material
that is surrounding this black hole. So the time period between oscillations is 9.6 million years
and that is just a large time to even really comprehend. No human will ever truly hear the
sound of this black hole, but we certainly can detect it. The way we've mostly detected it is
through the Chandra X-Ray Observatory observations. This is the most sensitive x-ray telescope
ever built. It's still in action orbiting the Earth taking data for us. In fact,
the Perseus Black Hole is not the only type that we've seen like this. There's a similar case that
we have seen of this in the Virgo Cluster which is another area that has a super massive black hole.
That's what we're seeing right here. Here is the x-ray data from the Perseus Cluster
and you can see these bands right here. This is what's indicating the sound waves that are
coming through it, but of course we're not going to hear it and we're not really
going to observe it because the time scale is just too large for us. Here
this is Messier 87. This is also the first one of the black holes in which we were able to get an
actual picture of. That's a topic for another video. But here you can see there's also these
shapes that are indicative of sound waves as well. So it's really interesting to learn
about singing black holes- that they can actually create the sound wave and be able to have waves
travel through them because of the material that's surrounding the black hole. I found this quote that
was spoken by Stephen Allen who is a physics professor at Stanford University he says. "We
can't see the waves moving.... the relevant time scales are just too long, since the period
of the wave is about 10 million years." So again, this is another picture that we have of the
Perseus Cluster. It's just really amazing that we are able to detect these things.
Wouldn't it be incredible if our lifespans were long enough that we can actually
observe this in action? That's not the case and that's okay. What's really interesting is
that every time I'm looking at Perseus, I kind of imagine this massive black hole
sending out huge amounts of energy that is able to create sound waves. That's pretty amazing.
Each time you look at Perseus just think about the singing black hole radiating energy across
space. So before we wrap up this video, let's take a quick moment and review how to find Perseus in the
sky. Remember we have a detailed video about how to find it, so be sure to check that one out.
When you're looking at this picture, this is the area that my eyes are drawn to as well as this
area right here. This is the Pleiades and this is a very obvious star cluster in the night sky. In
fact many people often confuse it for the Little Dipper because it kind of does look like a little
miniaturized version of the Little Dipper. However, you can use the Pleiades to help you find Perseus
which is in this region. This star cluster, right here, is the Alpha Persei Star Cluster.
So if we're going to point out Perseus- this is where he's located in the sky.
Then here are some of the constellations that surround perseus that you can use
to help you find it. We have Auriga down in green, right here. It has the bright star Capella
and you can use Capella to help kind of orient you towards Perseus. There's also the simple Triangulum
constellation that looks like a triangle. There's Aries, or at least a portion of Aries.
And of course the Pleiades Star Cluster. Next week we're going to focus on Aries and explore
that constellation a little bit more. Aries is a constellation I have always been fascinated
with. I struggled to find, but now I can find it really easily. Because I know how to find it
I'm going to pass that knowledge on to you. I hope you've enjoyed learning about Perseus
in the sky and some of the more mysterious objects, like the singing black hole
that's inside of this constellation. I encourage you to seek out dark skies when
trying to look at the constellations and give yourself some time, patience, and practice.
It's not always easy to find the stars but hopefully some of these videos will help you
with your journey as you explore the sky. Good luck finding Perseus and keep looking up!