When I look at this photograph my eye is drawn to two things. The first is this very
bright star which is the brightest point in this night sky, but I also noticed the
Big Dipper, right here, which is also called the plow in some other places of the world,
and honestly it has a lot of names, but this star pattern is very helpful because it can
help direct you to other parts of the sky, and you can use the Big Dipper to Arc to the star
known as Arcturus, and in this video we will explore this bright star called Arcturus in
the constellation Boötes and we will look at the characteristics of the star, how to find
it, and explore some of the reasons why this star is important to both past and present stargazers.
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. Now let's review over general information about Arcturus.
It's the fourth brightest star in the night sky, and it can be seen from everywhere in the
Northern Hemisphere and up to 50 degrees South latitude for the Southern Hemisphere. The reason
it's so bright in the sky is because it's fairly close to us and it's much larger. It's estimated
to be 36.7 light years away and it's a red giant star that's classified as a K 1.53 star, and we'll
talk a little bit more about what that means later on in the video. The name Arcturus is a
latinized greeked name that means 'arktouros' meaning 'the guard' or 'guardian of the bear' and it's fairly
easy to spot in the sky because it's bright and it's orange in color, and if we were to point out
the constellation pattern, let's back up here, this is Arcturus, right there, the bright star, and then
here is part of the constellation and this constellation as known as Boötes, and I have a
whole video on this constellation, and it's seated right next to Corona Borealis, which I have another
video for, so if you want to learn more about these two constellations go ahead and see that video, and
it's represented as a herdsman, so here is kind of what its representation is and how it's placed up
in the sky. So now we'll dive into some of the star characteristics of this system. It's classified as
a K2 star and it's estimated to be 36.7 light years away, so fairly close to us and here's a
picture of Arcturus, and it's about the same mass as the Sun but it's much bigger, and that's because
it's in a different stage in its life. It's kind of like what our sun will be become in the future
towards the end of its life. So its mass is 1.08 times the mass of the Sun, so, so very close but
its size is 25.4 solar radii, so that makes it 170 times more luminous than our own sun, and it's so
it's the same mass but bigger in size and it's a cooler Star than our own at the temperature range
of about 4,200 Kelvin, and its age is estimated to be 7 billion years old. Our own sun is estimated
to be 5 billion years old, so this this star is slightly older and that makes sense because it
is in a different stage in its life, and if we were to look at the 25 brightest stars in the
night sky here is where Arcturus is, I think I have it pointed out, there it is, so um I recently did a
couple other videos on some of the bright stars such as Arcturus or uh that's what this video is
but I've done one on Vega, and where else Antares, and Deneb, so be sure to go check out, oh there it
is, check out those videos and it is when you look at Arcturus one great thing about it is its color
is distinctive. It's an orangish red, it's very bright, and it's has since evolved off the main
sequence band, and if we were to compare sizes here this if this little pixel right here was
the sun, this is what Arcturus would be, so it's it is much larger, but there are other stars out
there that are much larger like Antares, this is showing you the the comparison between Arcturus
and Antares, I did recently do a video on that so go see that video, and if we were to plot exactly
where Arcturus is on the HR diagram, which is a color magnitude scale. This is where the sun is, and
this is where Arcturus is. You can see this is the main sequence band, and what does that even mean?
It means the star is stable, in terms of its gravity and fusion. These forces are
balanced, and a star spends 90 percent of its life in the main sequence stage, and the color magnitude
scale gives you temperature, which relates to color, it talks about Luminosity, so here's one Luminosity
which is measured in suns, so you can see our sun lines up with that axis, but here's where Arcturus
is, okay, so it's, and this is a logarithmic scale so it jumps from one to a hundred and so on
and so forth and over here this is talking about absolute magnitude, so cooler stars are over here
and then hotter stars are over here, and we measure that surface temperature with Kelvin, okay, and you
can see this is where Arcturus is. So it's cooler than our sun, but it's also bigger which
means that's why it is brighter, and if we were to look at very specific coordinates of Arcturus,
I listed the right Ascension right here, and declination as well, and I'm showing
you the the star map here, this comes from the International Astronomical Union, which
standardized the constellation boundaries in order to make sure astronomers were all
on the same page as we started to catalog more stars, and this was done in 1929. So it's in the
constellation Boötes I learned saying it Boötes but there are official pronunciations, there is
like a whole website on that which I will link in the information below, but just
as a reminder if we were to zoom in here, that's where Arcturus is and you can see its size is
on the star map is larger, and that's because it's a brighter star. So the size of stars on Star Maps
matter, it's it relates to its apparent magnitude which means how bright it is to us when we are
looking at the night sky, and right Ascension is a type of celestial coordinate. It measures the east
to west coordinates and it's similar to longitude with Earth coordinates and we measure it in hours,
minutes, and seconds, and then declination measures the north south coordinates and it's synonymous
with latitude if you were to compare it to Earth coordinates, and we measure declination in degrees,
arc minutesm and Arc seconds. So in the last portion of this video I'll talk a little bit more about
why this star is important and how to find it, and I found this this artwork from 1888 and it shows
you perfectly how you you can Arc to Arcturus, so here is the Big Dipper, you have the handle of the
Big Dipper and you Arc to Arcturus. That's what makes this star so easy to find, and I love how
you can see Corona Borealis here as well. You can see that kite shape of the constellation,
and if we were, here's another picture of Boötes, I feel funny saying that word every time,
I'm just not used to that pronunciation, but so if you're looking at this picture your eye is probably
instantly drawn to this bright star and that is Arcturus, you can see in this photo you see
a slightly yellow orangish color and you can see a part of the handle of the Big Dipper, right there.
So you Arc two Arcturus, and then the other half of that little saying is you speed to Spica. So
um eventually I will get a video on Spica made, but here you can also see Corona Borealis. So
let's point these out, that's where Boötes is or Boötes and here is where Corona Borealis is, and
remember you Arc to Arcturus and speed to Spica. So Arc to Arcturus and speed to Spica, and Spica
is in the constellation Virgo, so I do have a video on that it's constellation go see it if
you're interested in learning about that. So as you look at this picture are you able
to Arc to Arcturus? Find the brightest star in this picture and then can you see that kite shape right
there, and its arm goes up and it's represented as a herdsman that is guarding the bear, this is
um, the Big Dipper is an asterism it's part of a larger constellation known as Ursa Major. So
Ursa Major is the Great Bear and the herdsmen is protecting it, and here I pointed out some other
constellations for you. Here is Corona Borealis the northern Crown, here's Coma Berenices represented
by Berenice's hair, and this is Canis Venatici, and this one is represented as two dogs, it's
really easy to find because it's kind of parallel with the last two stars and the handle of the Big
Dipper, at least it kind of looks like it here in this Photograph, I know we're trying to take
a 3D sky and put it onto a 2d photo so Translate doesn't always happen very well. So I've
got a couple more pictures here for you, just to get some more practice. The brightest thing you
see is Arcturus, it's the very very bright star in the night sky, so can you can kind of reverse
back to the handle, right here, but I often just look I look for the Big Dipper and then I Arc to
Arcturus and here it shows you speeding to Spica, and this is kind a little bit of a grainy photo
but I like it because it shows you if and if you look closely there are a lot of constellations
here. So let's go over what these are, we have Ursa Major, you Arc to Arcturus and speed to Spica, here
is one version of what Virgo looks like, this right here is Coma Berenices, kind of looks like a like
very cluster of stars here and then here's Canis Venatici, this is Leo minor, and here is Leo the
Lion, and you remember you can use Ursa Major and the Big Dipper to the pointer Stars will point
you toward Polaris. We've got a few more shots here. So this one is a really beautiful shot, it's
a long exposure shot that's why we see more stars coming out, you may not necessarily have this type
of sky available to you but you can still use this picture to help you figure out the star patterns.
So the brightest Point here is Arcturus, remember it's much bigger than the Sun even though it has
about the same mass, and then here you can see the constellation, kind of looks like a kite, and then
I see like this this little smile from the sky, that's Corona Borealis, and if we were to point
that out that's where this constellation is, and one more final picture, this one is not as obvious
as the other one, but this one might be a little bit more realistic sky of what you would be seeing.
Here you can see I believe this is some sort of light pollution that's going on, but right
here is where Boötes is, Arcturus is right there, it's very big in the sky, okay, and here he's
protecting the bear and this is Corona Borealis, this over here um this is a part of serpens, this
is like the head of serpens, I didn't outline it here, but over here we're getting into Ophiuchus
and Hercules would be up in this region, you're you're not really seeing that here, but in the
next portion of this video we'll talk about some of the cultural importance of Arcturus and why
it is such an important star in the sky. In the last portion of this video we'll look at some of
the mythologies tied to Boötes. It is often the stories of the stars that we can connect to in
some way which help us remember the constellation, and just remember there are as many mythologies
about constellations as there are stars, so there really is no one correct mythology but I do love
looking at these ancient maps, here you can see Arcturus is right down here, he's holding the
two dogs which represented by Canis Venatici, and here according to one mythology I found that the
Boötes is represented by Arcus, the son of Zeus, and he was a demi-god, um, here is another depiction
you can see that shows you Boötes. Here is Arcturus kind of represented right near right near
his kneecap, and then you have Coma Berenesis and Canis Venatici, but I'm often reminded of
Hōkūleʻa from the time that I lived in Hawaii, and in prehistoric Polynesia there were Navigators
that knew Arcturus as Hōkūleʻa, as also called the star of joy and Arcturus is the Zenith star of the
Hawaiian Islands. So Polynesian Navigators use this star to launch their double-hulled canoes, right
here, from Tahiti and the Marquesas island, and they traveled north east, north and east and crossed the
equator and were able to learn where Hawaii was. So this is um very important story, and a very
important star to the Polynesians and I know I'm really only scratching the surface with some of
the cultural connections of Arcturus, but it's just really important to remember that the mythologies
of the stars really vary according to time, place, and culture. There is no one true mythology for
any of the stars or constellations, there's just a variety of them. So I hope this video was helpful
for you to learn a little bit more about Arcturus. To me it's one of the easiest constellations
to find in the sky because it is bright, it has an orangish color, and then you can use the Big
Dipper to help you Arc to Arcturus and speed to Spica. So thank you so much for watching, if
you have any comments or questions please be sure to put them in the comments below, and let me know
are you able to find this star. It really to me is one of the easiest ones to find and it can help
you find a lot of other constellations in the sky. So I wish you luck and as always keep looking up.