When you look at this picture there are three stars that stand out:
Vega, Altair, and Deneb. Vega is the brightest of the three, while Deneb is the dimmest of the
bunch, but either way you look at it these three stars are bright enough to see and identify in
most skies, in fact during my recent trip to Los Angeles, a place with lots of light pollution,
I was able to easily see this trio of stars, and this is probably a little more realistic picture
of what you may see when you go outside. I know we all don't have these brilliant skies to look
at, and this is a long exposure photograph that allows the gas of the Milky Way to come through.
Anyway I can easily point out this trio of stars and in this video we're gonna focus
on the dimmest of the three stars in the Summer Triangle, but it is by far the largest
star of the bunch, and it's one of the most distant stars we can see with the eye alone.
So in this video we're going to explore Deneb, a blue white super giant first magna 2 star whose
distance is a little elusive to us in our age of measuring stars. So, join me as we learn a little
more about this bright star in the constellation of Cygnus. 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 getting a broad overview of Deneb, the 19th brightest star in the sky. It is visible
in both the northern and southern hemispheres. In the northern hemisphere you can pretty much see it
in all areas, where if you're in the southern hemisphere you really can only see it to about
40 degrees latitude, or I've also seen reports of 45 degrees latitude in the southern hemisphere, and
its distance is between 1,500 to 2,600 light years away, and this is a wide range in terms
of its distance, and a little later in this video I'll talk about why this is and why we don't have
an accurate measurement of its distance, but what we do know is is a it's a bluish white supergiant
star and in about 8,000 years it'll become the new pole star due to the procession of
the Earth's pole over time. It is the dimmest point of the Summer Triangle, but that's not to say
it's a dim star by any means. If we look at this star map you can see just the size of the star
determines how bright it is to us, and it is a first magnitude star, and the name Deneb,
or Deneb as it's officially pronounced is derived from the Arabic term meaning tale, and
I fall into the pronunciation of saying Deneb. I think it's because of the star Denebola, and its
pronunciation that way. Denebola is the the tail star of Leo the Lion. So I find myself, I kind of
tend to say Deneb, when I think the official pronunciation is Deneb, and pronunciation of
stars can be very confusing, not only because of my regional accent and where I'm from,
but also there's multiple variations and this is not my specialty, different languages and
pronunciations of different words and different languages is not a strength of mine. I'm
primarily a scientist and an educator, but what is interesting about this star is that it's part of
two different asterisms. One is the Northern Cross, which I am outlining here on the screen, but the
other would be the Summer Triangle, which is the connection between these three bright stars, and we
see these in the summer months in the northern hemisphere, but it would be the winter months
for the southern hemisphere, and it's kind of cool that it's part of two different types of asterisms.
Deneb is one of the brightest stars that we can see, yet it's also one of the most
distant ones we can see in the night sky, and as I said earlier it's classified as a blueish white
supergiant and its distance has a range, and the reason it has a range is because
some of the measurements we've taken of it have had high margins of error, so that's why which
we'll we'll get into it a little bit, but in terms of star characteristics it's estimated to be 19
times the mass of the sun giver plus you know plus or minus 4 solar masses. It has 200 solar radii,
and it's estimated to be 200,000 times more luminous than the sun. Its temperature range is
much hotter than our own sun and it is much bigger, that's one of the reasons why it's more luminous,
and it is classified as a variable star. In fact it's the standard for a type of star
called an alpha cygni or cygni, i'm not even sure how to pronounce that hence my uh
weak latin skills here, but um it has a particular type of variation in its brightness.
It's due to non-radial pulsation, which i'm still trying to learn what that even means,
but in terms, I think with many of these star characteristics these are they're not as precise
as they could be, and part of that is because we don't know its specific distance, and the reason
for that is in when one of the recent missions , well not too recent, GAIA is the most recent,
but in the Hipparcos mission, which was done by the European Space Agency, and the the objective
of this mission was to pinpoint stars, their motion, and their distance, and we used this data to map
the night sky and its follow-up mission was the GAIA mission, and it continued to do the same thing
Hipparcos did, but just with more precision and with this mission, right here, the first mission we
found that there was a high margin of error when it came time to measuring the distance of Deneb,
and with the GAIA mission what we're finding is that it's simply too bright, it would just saturate
the the telescope and we wouldn't be able to get accurate distances from it, and we've been
able to learn a lot about over a billion stars um have been measured in the GAIA mission, and
this is information about GAIA EDR3, which stands for early data release 3.
So, you can see we have learned a lot about the stars but GAIA cannot measure the distance to
very bright stars, it just saturates the sensor and measurements become impossible. The brightest
magnitude that GAIA can measure is 1.71, and Deneb is brighter than that with a magnitude of 1.25,
but that's not to say we won't be able to do it in the future, this mission is still
going and perhaps we will be able to find a way to measure the distance, and from there we'll be able
to determine just exactly how far it is, but when you look at the 25 brightest stars and let's see
where is there is Deneb, danette um to see I've fallen to pronounce the different pronunciation
it's probably going to drive everybody crazy on this video, um, I just want to say Deneb, but Deneb
is the 19th brightest star but it's definitely out of all of these the furthest one away ,
yet it is still so bright, and that's because it's so large, it has a lot of surface area and it's
burning through its hydrogen fuel and and growing larger. So when we look at this diagram, this is the
HR diagram or which stands for Hertzsprung Russell Diagram, and eventually I'll have a whole video on
this diagram and it's a color magnitude scale. So it it determines, it shows us the temperature
hence the color of the star along with absolute magnitude, but also luminosity in terms of suns,
and notice this this here is a logarithmic scale, so if we were to find the sun on this
diagram that's where it is. It's a g2 star. It has one solar luminosity, and it has this kind of
you know orangish color but really the sun is white for us, and when we look at where Deneb is,
it is right there, so it's much larger it's much brighter, and it's much hotter than our own sun,
and Deneb is a part of the constellation known as Cygnus, which represents the swan and is a seasonal
constellation and I put here on the screen the exact right ascension and declination of this
particular star, so if you wanted to plug that into your telescope you can do that, and we're going
to zoom in here a little bit more on Cygnus. I really like this star diagram because it shows you
all the different types of celestial objects that can be seen within the boundaries of Cygnus,
but as a reminder right ascension, it's a type of celestial coordinate, same with declination and
it's synonymous to longitude and latitude using Earth coordinates. Right ascension measures the
east/west coordinates, which I highlighted here on this star diagram, and declination measures
the north/south coordinates, and we measure them differently. In right ascension it's measured in
hours, minutes, and seconds, where declination is degrees, arc minutes, and arc seconds, and we do this
because astronomers need to know exact positions of where to look at in the sky, and I just want
to draw your attention to this spot right here on the map. It's very close to Deneb,
and it is a nebulae or a nebula that's called the North America nebula. So if we were, if we were to
zoom in here that's you know it's very close here, and I actually have a whole video about all the
different types of celestial objects in Cygnus so I'll put a link in the information below for you
to check out that video, but you can see sometimes a nebula is named after its shape, so this one
resembles the continent of North America, and here is another picture showing you the same object but
looking at it with different filters, and when we do that we can see different structures. This
is what it looks like in visible light, but this is a combination of both in uh visible light and
infrared light, so or radiation. I shouldn't say infrared light, that's not quite the correct term.
In the last portion of this video iIwant to get some practice with you on how to identify Deneb
in the sky. This here is a gorgeous picture, it's a long exposure photograph so a lot of features are
coming through, but are you able first to identify the Summer Triangle. From there identify the the
brightest of the three, and then the dimmest of the three. So here it is, here is the Summer Triangle
right there, here's the brightest, and this one is the dimmest, and from there you can start to
point out where Cygnus is, the northern and also the Northern Cross is a little bit easier to see
in this photograph. Here is a kind of a zoomed up version, so if we were going to go back to this
picture this is where we're zooming into, right here, and I just had to share this photograph
with you. It's so beautiful, there's lots of gas and dust that's coming through in this long
exposure photograph. So if we were to look here at this next picture, I love this picture, I use it all
the time because it shows the entire summer sky in the northern hemisphere, and here on the one side
hopefully you can find the Summer Triangle, right there, and if you were to you know try to see which
one's the brightest, which one's the dimmest, Vega is the brightest, and here is the dimmest
that is Deneb, but again it's a first magnitude star, so even if you live in an area with lots
of light pollution you still should be able to find this star, and just know when you're looking
at these three even though this one is dimmer it's much bigger, it's just much much farther
away when you compare it to these two stars, and if we were to point out everything in this photo, here
is where Cygnus is, you have Lyra, Aquila, you can definitely see the Milky Way all throughout here,
and then some other constellations as well. So we've got one more photo; hopefully at this point
you're able to find Deneb not only in the photos, but hopefully when you go outside and look for it.
So here again find the three brightest stars. The brightest will be Vega, the dimmest will be
Deneb, and that is where Cygnus is, and Cygnus is just great to look at. Astrophotographers love
this love this constellation because it sits right in the Milky Way and there's lots to see,
and the two main stars are Deneb, it's the brightest of Cygnus, and the next brightest
would be Albireo, and for those of you that have watched my channel for a while Albireo is
one of my favorite stars, here I pointed out the Northern Cross again, but and here are all the
other main stars here, but I love Albireo because it's this awesome double star and then um I named
ended up naming my cat after this particular star and I'm talk, why am I talking about it now? Because
it's not often I get to talk about Cygnus, um so if you know where Deneb is you definitely
have to know where Albireo is, and if you ever get a chance you need to see this through a telescope
because or even a pair of binoculars because it's fascinating to see, and I have a whole video about
this so go go watch that video about Alberio, and as a bonus I'll add some recent footage of my
my kitty at the end of this video if you tend to stick around just as a bonus. So moving forward I
hope this video was helpful for you not only to find Cygnus, but also to find the Summer Triangle,
the Northern Cross and also Deneb, the brightest or the brightest star in the constellation of Cygnus,
and I find that the Summer Triangle is a really helpful asterism
to just help you navigate around the sky. If we look at this star map you can see that
the Summer Triangle is right here, and if you can identify where that is you can start to find the
other constellations that surround it. So use it as a guide to help you navigate through the sky.
Thank you so much for watching let me know, have you been able to find this star? Have you
been able to find these Three stars? I definitely challenge you to go outside and try to do that and
let me know in the comments below. Thanks again for watching and as always keep looking up.