Sirius, also known as the dog star, is one of the most brilliant stars in the night sky. It
is also one of the closest to our own solar system being only 8.6 light years away. It is located in
the constellation known as Canis Major, which represents the great dog, and is one of Orion's
hunting dogs. This bright star is actually a binary system. It has a companion white dwarf
star and they orbit each other every 50 years. It has been used for navigation, agricultural timing,
and has a deep cultural significance in many cultures. So in this video we're going to
explore this nearby system and strategies you can use to help you find it. Welcome to Learn the sky
my name is Janine and I'll be your guide as we explore the night sky one constellation at a time.
First we are going to look at the general characteristics of this binary star system.
So Sirius A is the larger and brighter of the two stars in this system, while Sirius B is classified
as a white dwarf star. Sirius a is a white main sequence star so both of these stars are in
different phases of their evolution. They revolve around each other every 50 years and they're
fairly close together at 20 astronomical units apart. Again, it is located 8.6 light years away
that's why it's so bright in our night sky. If you look at this photo right here this is Sirius A,
and then this little dot right here is Sirius B. This photo was taken by the Hubble Space
Telescope, and the name Sirius comes from the Greek word 'seirious' which means 'scorching'
or 'glowing' and if we want to take a look at the size comparison this is what Sirius A would look
like, and here is Sirius B. So it's much smaller, but they are both white stars. This one is cooler,
while this one is much much hotter and we'll explore why that is in a little bit. So let's
dive in and look at Sirius A. This is a white main sequence star and it's about two times the mass of
our own sun, and almost two times the radius. It clocks in at about 1.7 times the radius of
the Sun, and it's 25 times more luminous than our own sun, and it is hotter. It's just about
10,000 Kelvin. It's classified as a Class A star, which means it is white in color,
and one cool fact I found about Sirius A and B, because they're both a sar system is that the
Voyager 2 spacecraft will pass really closely to this star system within four light years of it,
and this won't happen for about 300,000 years but I just thought that was something cool about
this star, and then let's look at Sirius B. This is a white dwarf star which means
it's evolved past the main sequence phase of its life, as well as the red giant phase. So
it's no longer fusing any hydrogen or helium it's just really really hot leftover core of a
star. It is about the same size or I'm sorry Mass it's about the same mass of the Sun,
but it is much smaller. Look how much tinier it is here. .0084 radii of the Sun so it's really tiny,
and then it's also very dim so this is not a star you can see with the naked eye. You're only really
able to see Sirius A. This star is also nicknamed the pup star because it's the smaller of the two.
When we look at the size of the Sirius system with our own solar system we can see that Sirius A is
much larger than our own Sun, but when you compare Sirius B with earth the earth is just a bit bigger
than Sirius B, and I learned that Sirius B is pretty large for a white dwarf star. When you
compare them to the rest of the ones that we have been studying, and then if we were to look at the
Hertz sprung Russell diagram ,and I have a whole video on the HR diagram. It's how we
classify Stars by brightness, temperature, color, okay. So we would have the classification here,
Stellar classification, which equates to color as well as temperature and then here you have the
brightness on the side. So let's get acquainted with where we are. Here is where the sun is. We
are classified as a G star and Sirius A is located right here, and this star right here, that's Vega.
So Vega and Sirius are very close in size, but their shape is different. Vega has a little bit
more flattened at the poles because it's rapidly rotating, and then Sirius B is down here. So
that means it's dimmer than the sun, but it's much hotter as well. If you look at this here,
this is where the sun is, Sirius is brighter and it is hotter than our own sun, and when we look
at the 25 brightest stars in the night sky Sirius is the brightest star that we can see in the night
sky. The only other things that are brighter than Sirius would be the moon, our sun, as well as some
of the planets like Mars, and Jupiter, and Venus. So as you can see if we zoom in Sirius is here,
and it's also very close to us. So when we look at the sun's closest neighbors, here's the Sun and if
we go out a few light years this is where Sirius A and B would be, just 8.6 light years away. So it's
kind of like the the fifth closest SAR system to us, and remember you're not able to see Sirius B
with the naked eye, but when you look at it, it's like this beautiful photo right here, when you
are looking at Sirius, which is very easy to find know that you're seeing this binary star system.
Now let's explore how to find Sirius in the night sky. It is one of the easiest stars to find,
not just because it's the brightest star in the night sky, but it also sits right next to Orion
in the sky, and you can use Orion to help guide you to many other constellations in this area
of the night sky. So remember that Sirius is a part of the constellation known as Canis Major,
which is Orion's hunting dog. Remember the key to finding Sirius in the night sky is using Orion.
You want to find Orion and use the belt stars to point you towards Sirius. Orion is so important
finding many constellations in this part of the sky. Another way to find Sirius is to use
an asterism known as the winter triangle.As you look at this photo you should be able
to hopefully see the three brightest stars, and they connect to make a triangle just like this,
and the brightest star in that triangle is Sirius. The other stars we have are Betelgeuse,
which is a part of Orion and Procyon, which is a part of Canis minor, which is Orion's small
hunting dog. I've got another photo here for you of the winter triangle. Hopefully you're
able to see the three brightest stars make that connection and then the brightest one is Sirius.
If we point out the other constellations here we have Orion, we have Canis Major, and Canis Minor.
Thank you so much for watching this video about Sirius. Now when you go outside and find the
brightest star in the night sky you're actually looking at a binary two star system, and I know
I didn't even touch on all the different type of mythologies and stories that are connected to this
very culturally significant star, but there is a lot to unpack there so I want to take the time
and do it justice. So I hope you can go outside, find Sirius, and if you have any questions please
leave them in the comments below. Thank you so much for watching, and as always keep looking up!
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