Welcome to Learn the Sky! My name is Janine and every Tuesday I release new videos
exploring the sky one constellation at a time. If you're new be sure to subscribe and if you'd like
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each season. Welcome, my name is Janine and today's video will focus on the astronomical event known
as the Autumn Equinox in 2020, which happens to be this day that the video is being released,
September 22nd. So what does the Autumn Equinox mean? Basically it's this time of year in September
when you have equal days and nights. So they're not exactly equal, but it's fairly approximate. So
12 hours of day and 12 hours of night. For us in the northern hemisphere Autumn Equinox signals
the changing of the seasons, and the changing of the seasons is caused by this celestial event.
The Sun is starting to rise later nightfall comes sooner and because of that the days
are becoming cooler, and this has to do with the heating of the Earth which we'll talk
about a little bit later in this video, but for those that are south of the equator down here
they are moving into spring. So they're finishing off their winter, we're finishing off our summer,
we're moving into autumn, they're moving into spring. So let's examine the word equinox. It comes
from the latin word 'aqueous' which means equal and '-nox' which means night. So generally we'll have 12
hours of night and 12 hours of day, equinox, and when we look at the Earth going through its orbit
okay, this is one full pathway around the sun and if we come to September, where we're talking about,
that's when we'll have equal day and night. The opposite end of that is the March Equinox, the
Spring Equinox that's when there will also be equal day of night, but when we're looking at
it in terms of summer and winter, and your summer and winter depends upon which hemisphere you're in,
during this area right here, so I'm at the northern hemisphere in this part the Sun is spread out
over a larger area, and that's why it's winter here, but down in the southern hemisphere this is
when some the Sun is more intensely spread over one particular area, so it means warmer days, and
longer days as well. So this is known as the winter solstice, and then over here is the summer solstice.
So longest night, longest day in the year, and then in between are when they're equal. So that's how
that works, and if we were on Earth and observing the sky what does this even mean? So when
we're talking about like earlier humans, they used to spend way more time outside observing the sky
and they used it not only as a clock, but as a calendar. So during the times of winter
solstice, which happens in December or between the 21st and 22nd, that's when the Sun is at its
lowest point in the sky throughout the entire year. When we go to the equinoxes there's two of
them there's the autumn one, which happens in September no matter where you are in the globe,
and then the spring one which happens in March no matter where you are around that particular date
so this is the position of the sun in the sky in March as well as in September on these particular
dates, but when we're looking at the summer solstice, which happens between June 20 to 21st,
that's when the sun has its highest point in the sky and we have the longest days because of that.
So again this is, the autumn equinox is just one point along the path of the Earth going along
its orbit around the Sun. One of the misconceptions that many of my students have about the seasons
is that the reason there are seasons is because the Earth is farther away from the Sun, but that's
not the case. The reason we have seasons is because the Earth is tilted on an axis, and the Sun's light
either hits it more directly or is spread out over a larger area, which therefore influences the
Earth's seasons. So here, the sunlight is directly on the northern hemisphere, and that's when we have
the summer days, or what we call the polar day if you're living at the top of the Earth's globe, but
down here the sunlight is spread out over a larger area, and that's when they experience winter, or
down here it would be called the polar night. Where can you look for the equinox in nature? It really
comes from the fact that summer is gone, and now winter is starting to arrive with the shorter days.
So all around us we've got plants and trees that are ending their cycle of growth, and it's almost
like nature's last blast of energy and color before the winter comes, but once the winter comes
we also notice that animals are migrating such as butterfly and birds, but as we move into winter
we'll have shorter cooler days, the sun rises later and, then the night also comes earlier, so that's
what we experience in northern hemisphere as we're moving into the autumn equinox or past it, and then
however the spring is happening for those that are down in the southern hemisphere.
So for me when I think about the autumn equinox I start to think about the stars that I'm going to
see. So for us, up in the northern hemisphere, we're going to start to see some of what I call the
autumn constellations, because this is what I would see when I'm going out during this time
of year, and Pegasus is one of those. Pegasus is the winged horse, and its Great Square really dominates
the autumn sky in the northern hemisphere. Here's part of that shape here, and if we
were to look at another picture can you point out the Great Square of Pegasus? So around the
autumn equinox I know it's time to look for this guy in the sky and if you were to point it out,
that's what Pegasus looks like look for that Great Square of Pegasus asterism moving into
autumn. You can also use Pegasus to point you to other constellations. I use the head of Pegasus
to point me well towards Delphinus, and then this star in the Great Square is connected to Andromeda.
Delphinus is a fairly easy constellation to point out. Its stars are of equal brightness or magnitude
and it has this little diamond shape in the sky. So look for Delphinus it's represented as a dolphin,
another dominating constellation during this time in autumn is Andromeda, and this is represented as
a chained woman and what's really spectacular about Andromeda is the galaxy that
sits within its boundaries. So if we were to look at a picture of Andromeda, you can see the main
bright stars, but you can also see the Andromeda galaxy, and this is the most distant object that
you would be able to see with the naked eye. I've seen the Andromeda galaxy both with a telescope, a
pair of binoculars, but also with the naked eye you definitely need some dark skies in order to see it,
but this little patch of fuzzy light in the sky is 2 million light years away, and it's kind of like a
sister galaxy to our own Milky Way galaxy, but it's a lot bigger, it's twice the size of our own Milky
Way galaxy, and if we were to point out Andromeda here is the star pattern, and here is the galaxy,
and if we were to zoom in and take a look at this galaxy here is what she looks like. Thank you Mr.
David Cocklin for allowing me to use this photo for this video! So the Andromeda galaxy is kind
of like the jewel of the autumn sky, and you want to try to point it out by finding Pegasus and then
finding Andromeda. Triangulum is another really easy constellation to point out because it makes
a cute little triangle shape in the sky, it's close to Andromeda and it has another galaxy of its own.
So if we were to take a look at this picture there's a few constellations we have,
first we'll point out Cassiopeia right there, and then the one side of Cassiopeia can point you
towards the Andromeda galaxy. Here's one version of what Andromeda looks like in the sky, at least
those are the main stars that I see, and if we were to point everything else out here we have
Triangulum, which I just taught you is a little triangle shape constellation, here we have
Perseus, and down here we have Aries. Perseus is another great constellation to try to find
in the autumn sky. It's located near Cassiopeia, and Cassiopeia is often very easy to find. If you need
help with trying to find that constellation go see that video. Here we have a picture and Cassiopeia
is right here on the side, here is where Perseus is, it's kind of sandwiched in between Cassiopeia and
Taurus. This is the Pleiades that little star cluster that's starting to come out now that
autumn has arrived. If we were to point everything out this is the star patterns that are in this
picture. We have Cassiopeia, Perseus, Taurus, and then Aries is nearby as well as Triangulum. Capricornus
is another constellation that's worth trying to find. It kind of has this boomerang type shape
in the sky and it is a zodiacal constellation because the Sun passes through its boundaries
at some point in the year. If we were to look at this picture, here's where Capricornus would be.
It makes this type of shape in the sky, and it's located right next to Aquarius, and Aquarius is
located to a lot of is located nearby to a lot of things in the sky that have to deal with water or
the sea. In fact Aquarius is located in that region of the sky that we named the sea or the water,
and Pisces is nearby, Cetus the sea monster, we have Capricornus, and then Aquarius as well.
Aquarius is one of those constellations that it took me a really really long time to find
because its stars are not extremely bright. I do have a video about Aquarius so be sure to
go check that video out as well, but if we were to try to find it in this star picture here is
where Aquarius would be, these would represent his legs, his head, and then this is kind of his
his urn of water or jug of water. I often look for this kind of pattern, it looks like a y shape to me,
and that is what helps me find Aquarius, but it's one that has taken me a really long time to find
in the sky, and if you live in any area that has lots of light pollution you may struggle to find
Aquarius, and if we were to try to get a little bit of practice trying to identify some constellations
here this is a maybe not the brightest picture but there are some interesting things here.
Right here we have, and I'm going to point these out, we have Aquila, this is Capricornus, and then
this is where Aquarius would be, and then you have the head of Pisces peeking through here. So
you want to look for this shape in the sky to find Capricornus and then know that Aquarius is nearby.
Pisces is another constellation that could be seen in the autumn sky and this is another one that
I've been challenged to find because many of its stars are really faint. If you look for the Great
Square of Pegasus in the sky, Pisces is right next to it, so try to look for this little circle it
pattern right here, that circle it is known as an asterism, if you want to learn more about asterisms
go see that video, but Pisces is also in the sky and if we were to take a look at Pisces
you can see there's not a ton of bright stars that are here, and the ones that are are not a
part of Pisces. Right here we have the Great Square of Pegasus, and if we were to point
out where Pisces would be in relation to that, that is where it would be in the sky.
We also have aries right over here ,and Andromeda is up here and Pegasus. So try to find Pisces in
the sky but again I recommend you seek out dark skies, because its stars are fairly faint. If we
move on to Aries this represents a ram, and the ecliptic or the path of the sun passes through
it, so it's classified as a zodiacal constellation. So for me always try to find Aries by using
this star cluster known as the Pleiades, and Aries in a way kind of point to that, let's go back there
it kind of points towards the Pleiades. So this is the thing that my eye is drawn to right away
in the sky when the Pleiades are out, and from there I look for this constellation of Aries.
Cetus is another constellation that's out in the autumn sky, but it's one that I'm not extremely
familiar with because it does not stand out in the sky whatsoever. I struggle to find Pisces, and Cetus
is just as difficult. It's represented as either a whale, it's been represented as a shark or a
sea monster, and it's classified as a seasonal constellation, and if you're trying to point out
where Cetus would be it's towards the bottom portion of this photo. Up here you can see Aries,
so if we were to point that out, this is where Cetus would be that's its pattern and then Aries
is nearby but Cetus is really more known for some of the amazing celestial objects that sit
within its boundaries rather than its bright stars. This concludes our video about the autumn equinox,
and I hope you have a better understanding as to why we have equal day and equal night
two points throughout the year. When we are observing here on Earth it's all about where the
Sun makes the highest point in the sky. So in the winter solstice that's when the sun has the lowest
point, the summer solstice is the highest point where the sun is in the sky in the longest days,
but the equinox is when there's equal day and night and the sun is not low it's not high but
right in the middle, and that happens twice a year in March and in September. So I hope this gave you
a better understanding as what the equinox is, why we have it twice a year, and just appreciate the
change that the Earth goes through throughout the year. So I wish you luck and trying to find
the autumn constellations that are out in the sky now. In the next few weeks on this channel we're
going to be focusing in on some of those autumn constellations. Take care and keep looking up!