Orion the hunter constellation is one of the easiest star patterns to find in the night sky,
and one of its most defining features are the three stars that make up Orion's belt.
This linear pattern is important because it can be used to point out other constellations in the sky,
such as Canis Major, right here, or if we aim upwards it can point to Taurus ,which is not
pictured in this photograph. These three stars have a variety of names throughout the world,
and in this video we're going to explore these three stars
in greater detail because there is definitely more here than meets the eye.
Welcome to Learn The Sky! My name is Janine and i'll be your guide as we explore the night sky
together, one constellation at a time. Let's begin by taking a look at the celestial map of Orion
besides this very bright star of Sirius, right here, the belt stars definitely stand out to me because
they're close together in the sky and they also have that straight linear shape to them, and you
can use the belt stars to aim you towards Sirius, which is the brightest star in the night sky,
and you can also use them to aim you towards Aldebaran, Aldebaran is a reddish orange star
and it represents the eye of the bull in Taurus constellation. So if we zoom in here you can also
use this middle star to aim you down towards the Great Orion Nebula, and you can also see
the names here we have Alnitak, Alnilam, and Mintaka, and even though we see three stars
here, two of these stars are in fact multi-star systems, which is really exciting and we'll get
into that a little bit later in the video. I've got multiple videos about Orion, and its bright
stars, and celestial objects, and practice with how to find it, so be sure to go check those out.
Every time I look at Orion I am always amazed and somehow comforted by its beauty,
and as a scientist I love knowing that at some point each of these seven brightest stars will
eventually become a supernova, including the belt stars, and I think it's important to point out
that the belt stars have a variety of names and mythologies that go along with this three star
pattern, including the Three Mary's, the Three Kings, the Weighing Beam from Chinese culture,
Tautoru from the Maori culture of New Zealand, and I'm certain there are many many more names
that exist out here besides the ones I listed here. So let's get a little bit practice making sure you
can see the belt stars, and here you notice that it points towards Sirius,and this whole constellation
right here is Canis Major and these belt stars are also classified as an asterism since it's not a
true constellation on its own but rather a smaller shape within a larger constellation pattern
that can be used to find other patterns. Let's take a look at another picture. Here you can see
the belt stars again, you can use that middle star aim you towards the Great Orion Nebula, and then
here you can aim it towards Aldebaran, right here, um it doesn't really show up as reddish orange in
this photo, and this right here is a planet, and we have the Pleiades here, but it just gives you
another opportunity to use the belt stars to help you find Taurus, and I've got one more picture I
want to share with you. I've been looking for one like this for a while, but this is what Orion looks
like from the southern hemisphere, and I wanted to include this for all our southern hemisphere
friends who watch this channel, because they often comment that "hey, Orion looks upside down", beside
it looks different than the way I see it. So every time I see it oriented this way in a photo it kind
of throws me off, but you can still use it to help you find Taurus, which is right here, and then you
can use it to find Sirius. So in the next portion of this video we're going to take a closer look
at the belt stars. As you take a look at this photo what you're looking at is a close-up view of the
three belt stars and if we were to put names to them we have Alnitak right here, Alnilam, which
is famous for being the brightest one, and largest out of the three and Mintaka. Mintaka
is the westernmost star while all Alnitak is the easternmost star, and notice the amazing celestial
objects that sit right next to Alnitak. We have the Flame Nebula and the Horsehead Nebula right here,
and the belt star names are derived from arabic words Alnitak meaning "the girdle", Alnilam meaning
"string of pearls", and Mintaka for "belt". I've got one other close-up picture I want to share with
you of the belt stars. This is such a gorgeous photo and I'm really excited to share it with you.
We have Alnitak right here, Alnilam the brightest right here,
and Mintaka. Remember you can use Alnilam to aim you towards the Great Orion Nebula.
We have the Horsehead Nebula right here, and the Flame Nebula there. Remember I've got a
video about the celestial objects of Orion, so if you want to learn more be sure to go
check that video out. Now we're going to dive into more specific details about these stars.
So as you're looking at this diagram notice we have the size of the sun, right here, which is
equal to one solar mass and one solar radius, and then we have the main stars of the belt stars, but
keep in mind that Alnitak is a triple star system, and Mintaka is a multi-star system as well.
So the main star, when we're looking at this diagram we're talking about the main stars of
those multi-star systems, the ones we can visually see from our perspective. So Alnitak, the main
star there, has 20 is estimated to be 20 solar masses, and have the radius of 19 suns. Alnilam is
like twice the size of that. It is estimated to be 40 to 42 masses, while having 30 solar radii, and
then Mintaka is also a bit smaller than Alnitak. It's the smallest of the three, at 20 solar masses
and 16 solar radii. So I want to talk a little bit more about each of these star systems. So
Alnitak, remember the easternmost star right here, is a triple star system and it's estimated to be
1260 light years away, and if we're looking at it here, this is where Alnitak is, and the triple star
system, not all of them are the same, the biggest one is a blues supergiant, and that's designated as
Alnitak Aa, and then the next one is Ab, the blue sub giant, and then we have Alnitak B, which
is a blue giant. So let's get a visual on what this looks like. The blue supergiant is the one
that we are primarily seeing, however it could be combined light from all of them to be honest. Ab
and Aa they are both very young stars and then actually these three stars are it's estimated that
they formed at different time periods, and the main two stars right here, Aa and Ab, they have that
designation because they are the main binary pair, and it's estimated that they complete one orbit
around each other once every about two and a half days. This third companion right here um is a blue
giant star, this one is um Ab is a blue sub giant, while Aa is a blue supergiant. So what does that
even mean? Well mostly size and temperature and I'm going to refer to the HR diagram, here on this.
So most stars spend their life in the main sequence band, right here, which means that
it is a stable star. It's it's pressure from fusion and is balanced with the force of gravity,
and a star spends 90 percent of its life here, but as a star starts to change its size temperature
and color can change as well. So a sub giant is right here, it's not quite a giant star,
but rather um it's starting to evolve off the main sequence, which tells us that it's starting to run
out of fuel. So supergiants are up here, this is when you had some main sequence stars in this band
in the OB band, or the spectral class. They are starting to evolve and change. They're running out
of fuel so they grow in size. So I've got one other close picture here of Alnitak for you, Just again
showing you the beautiful Horsehead Nebula and the Flame Nebula. So let's get into our next star.
Now let's take a look at Alnilam, which is the middle star of the belt stars, and
it's by far the largest and brightest of the three. It's classified as a blue super giant star,
and it's estimated to be 2,000 light years away. I found a range in terms of its size and diameter,
and when we zoom in here ,this right here is Alnilam. You can notice that it's brighter than
the other two and it's estimated to be 40 to 44 times more massive than the sun,
and between 30 to 32 times the diameter of our sun, which is hard to even comprehend. It's also
a variable star and it's the youngest of the bunch and it is expected to evolve into a red supergiant
and eventually explode as a supernova. Another interesting fact I found is that it is losing mass
20 million times more rapidly than our own sun, and the reason for that is because it is so
huge. Bigger stars burn through their fuel much more quickly than stars like our own
son. In the last portion of this video we are going to go over the characteristics of Mintaka, which
is classified as a blue giant star, or at least the main star of this entire system is, and it
is classified as the smallest one of the three, and it's estimated to be 1,200 light years away,
but even though it's the smallest of the three, to me it's one of the most interesting because
it has this multi-star system thing going on, but at the filming of this video it's confirmed that
there are five stars, but there could be a possible sixth one. I found multiple sources about this, but
nothing that's really solid about that six star and if we were to zoom in
this is where Mintaka is, and if we were to take a look at this system the primary feature here
is this main one right here. So Mintaka Aa1 and Mintaka Aa2, 1 is an O-type Giant Star, so it's
bigger than the B-type Main Sequence star, and these two stars orbit each other every 5.73 days,
and they do see some small eclipses when the star dims, this star will dim when um it passes
behind. When these two are together they're brighter, but when one passes behind the other
it it dims a little bit, and then you have this B-Type sub-giant star. So remember a
sub-giant is no longer a main sequence star but starting to evolve away from it,
it's starting to run out of its fuel and starting to grow in size. The secondary pair here is HD 36485,
and this star has Mintaka B, an A-type Main Sequence star. So it's it's smaller and its
color is more white as opposed to blue, like the other four systems, um so this is really
just an interesting thing to me because as I was learning about this I'm like I had no idea that
orion some of the stars in orion's belt were multi-star systems. So thank you so much for
watching this video! I hope it was helpful and next time you look at Orion's belt, now you know there
are more than just three stars there even though we can't necessarily see them, and let me know in
the comments do the belt stars go by another name in your part of the world. Remember as you learn
the constellations it really takes time patience and practice. Take a friend outside with you and
marvel at the beauty of the stars. So thank you for watching again and as always keep looking up.