When is summer in the southern hemisphere
Why does the Southern Hemisphere get the best view of the Milky Way?! | The Galactic Seasons
as an astronomer that lives in the
northern hemisphere it bugs me to no end
that I cannot see the center of the
Milky Way from where I live all those
amazing images you see of the Milky Way
with that really dense region of stars
and dust I ever taken from the southern
hemisphere where it rises to be directly
above your head or in the summer months
from very low down near the equator in
the northern hemisphere and it just
rises above the horizon where I am in
the UK the center of the Milky Way that
most spectacular region in the
constellation of Sagittarius it never
rises high enough above the horizon you
know like more than 10 degrees for me to
actually be able to get a good look at
it it's too low down and in the summer
months when it's visible like the Sun is
not that far below that horizon so it
gets so washed out you really can't
appreciate it at all and even further
Northup like on the pole itself it never
Rises there and you can't see it at all
any time of the year so why is that the
case the Milky Way is kind of like a
fried egg shape right it's a flat disc
with a big bulge yoke in the middle
where there's lots and lots of stars a
supermassive black hole at the center
and if the Sun is just one star in the
Milky Way that orbits around the edge
and we the earth go around the Sun then
how come is it from the southern
hemisphere they're the only ones able to
see the center of the Milky Way well
there's lots going on and in the
northern hemisphere we look out towards
the edge of the Milky Way you know when
you picture the earth bare on the Sun
and the Sun going around the Milky Way
you picture them sort of all going
around in a line but that's not true you
know if it were then the path of the
planet on the moon everything that's in
the plane of our solar system in the sky
would trace the same path as the Milky
Way does across the sky but that's not
the case if we think about like how we
navigate around this day we picture the
earth and the sky is sort of a an
extension of the surface of the earth
there's another sphere that surrounds us
obviously it's in three dimensions but
really how our eyes perceive it is if
it's on the edge of this celestial
sphere it was
the North Pole of the earth in the South
Pole of the earth as well and so we can
imagine there's a North Pole of the
celestial sphere and there's a South
Pole of the celestial sphere and
similarly the equator of the earth can
be expanded outwards to give you the
celestial equator and it just so
happened that the north west your pole
points directly at the star Polaris the
North Star whereas the South celestial
pole isn't actually near to any star
that the human eye can actually see and
the Earth spins on its axis that joins
the North Pole and the South Pole now
the thing is that we know that that axis
is tilted with respect to how we orbit
around the Sun it's what causes our
seasons in the southern hemispheres
summer the South Pole is pointing
towards the Sun and the North Pole is
pointing away making it winter in the
northern hemisphere six months later the
North Pole is pointing towards the Sun
the South Pole is pointing away from the
Sun and it's Northern Hemisphere summer
and southern hemisphere winter between
the two you have the equinoxes equal day
at equal night for both northern and
southern hemispheres and so you have
sort of autumn and spring switched
around between the two hemispheres what
that means is that you've got another
way of navigating around the sky instead
of taking the equator of the earth and
expanding that outwards to your
celestial sphere you can take the orbit
of the earth around the Sun expand that
outwards and then you'll have a new
circle around your celestial sphere
which we call the ecliptic which is at
the same angle as the Earth's tilted
axis with respect to the celestial
equator and that is the path that the
Sun and all the planets in the solar
system take through the sky because they
all all bit on that same plane around
the Sun and so along with the Earth's
orbit around the Sun in one plane you've
also got the sun's orbit around the
galaxy now it's going around what we
call the Galactic plane that plane of
the Milky Way disk but just like how the
Earth's axis is tilted with respect to
the plane it goes around the Sun the
sun's axis is tilted with respect to how
it goes around the galaxy and it means
that the entire plane of the solar
system is a
angle of about 60 degrees with respect
to the galaxy now you might think that's
really weird that the plane of the solar
system doesn't line up with the plane of
the galaxy but the two were formed
independently the galaxy is much older
than the solar system itself and so it
all just depends on what random
direction the gas that made them was
swirling out to the gas that made your
galaxy form and the gas that your son
and your planets formed from happen to
have some rotational energy that we call
angular momentum that happened to be
going in some direction and so that's
why it ends up forming around whatever
direction that gas was going in so for
the Sun it was tilted at slightly about
60 degrees from the rest of the galaxy
and interestingly although those planets
are going around the Sun in one
direction altogether because they all
form from that same cloud of gas that
had the angular momentum the Sun orbits
the Milky Way in the opposite direction
that the Earth orbits the Sun and again
it's all down to the angular momentum of
the thing that it was formed from so
because the player of a solar system is
tilted with respect to the galaxy all
hope is not lost for me the northern
hemisphere astronomer because just like
how the earth axis is tilted and it
means that it causes our seasons so that
once a year the southern hemisphere
points towards the Sun and once a year
the northern hemisphere points towards
the Sun so as the Sun orbits around the
Milky Way
currently the South Pole of the Soudan
points towards the galactic center but
as it moves around as it's on the
opposite side it means the north pole of
the Sun will point towards the galactic
center and because the tilt of the earth
means the north pole of the earth is
only about 23 degrees out from that the
northern hemisphere will point towards
the galactic center so I guess how you
can think of it is that we're currently
in the sun's Southern Hemisphere
galactic summer and then eventually
we'll be in the sun's northern
hemisphere galactic summer the key word
though there is eventually because it
takes the Sun 200 to 250 million years
to make one lap around the
keyway ie it's the lactic year is about
250 million earth years so we're gonna
have to wait at least a hundred to
125,000 years to make it into the Suns
northern hemisphere galactic summer so I
went on to stellarium which is this
amazing app that you can get pew
computer to see you know what the sky
looks like at any time of the year at
any time of day from anywhere in the
world and I wondered how far in the
future couldn't actually show me
unfortunately Stellarium only goes up to
a hundred thousand years in the future
no matter how many times I clicked it to
try to make it go above that hundred
thousand years in the future though
Sagittarius is still not visible from
the North Pole and lasts because the Sun
is only like point zero four percent of
the way around its galactic orbit that
takes 250 million years or so it will
only be when the Sun is 25% around its
galactic orbit that Sagittarius will
start to rise above the horizon at the
North Pole in 60 million years time but
all the time the Sun keeps orbiting
around the center of the Milky Way
Sagittarius will rise higher and higher
latitudes similar to where I am in the
UK so that'll eventually by the year a
hundred thousand it will rise above like
20 degrees in the sky in springtime of
each year so that I am actually able to
appreciate it in all its glory
so all I need to do is live another
ninety seven thousand nine hundred and
eighty-one years and I will get my wish
of being able to see the center of the
Milky Way from where I live in the
northern hemisphere brown skin your skin
just like me oh I need a holiday you
know when you think about the earth
around the Sun the Sun going around the
central Milky Way you often think about
them as being blind so all I've got to
do is live another 918 319 - 100
thousand hundred thousand is between 99
9
9 no 9 8 9 7 what should we do with it
I'm concerned what should we do with
drunkenness drama what should we do with
the drunken about morning
