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Video tags
Subtitles
Russian
00:00:01
in the beginning there was darkness00:00:03
and then bang giving birth to an endless00:00:07
expanding existence00:00:09
of time space and matter now00:00:12
see further than we've ever imagined00:00:14
beyond the limits of our existence00:00:16
in a place we call the universe00:00:21
it's a crucible of creation and00:00:24
destruction00:00:25
the name milky way sounds like something00:00:27
kind of comforting sweet00:00:29
but the milky way galaxy is a monster00:00:31
it's just one galaxy among billions00:00:34
and we're living on the edge just00:00:37
recently we've discovered that there are00:00:38
two small galaxies colliding with the00:00:40
milky way right now00:00:42
it's a tapestry of brilliant suns and00:00:44
blinding dust00:00:46
it's surprising how little of the light00:00:48
from our rather luminous milky way00:00:50
galaxy reaches us00:00:52
it's a place of extremes where stars can00:00:55
drift lazily00:00:56
or be flung out at more than a million00:00:58
miles per hour00:01:01
now scientists have pierced the galaxy's00:01:03
heart of darkness00:01:04
to find our way through the milky way00:01:21
it's a hundred thousand light years in00:01:24
diameter has a trillion times more mass00:01:28
than our sun00:01:31
it began about 13 billion years ago00:01:36
and is still under construction00:01:42
it's our galaxy the milky way00:01:47
the milky way galaxy is an extremely00:01:49
active place00:01:50
it's like a construction project there's00:01:52
things going on all00:01:54
the time and you have old stars die and00:01:57
torn down00:01:59
and then that material it's used to00:02:01
build brand new stars00:02:06
in the midst of this work zone lies our00:02:08
little solar system00:02:10
and a whole lot more i suppose the best00:02:13
way to think of the milky way galaxy is00:02:15
our family of stars00:02:16
these are the stars that we travel00:02:18
through the universe with00:02:19
in a clump all orbiting at common center00:02:22
[Music]00:02:24
within its far-reaching spiral arms lie00:02:27
clues00:02:28
to where we started and how00:02:31
it will all end00:02:37
on a clear summer night the stars of the00:02:39
milky way00:02:40
unfurl like a shimmering banner across00:02:43
the sky00:02:45
ancient egyptians saw this river of00:02:47
stars as a pathway to the afterlife00:02:50
but the greeks were the first to name it00:02:53
the milky way comes from the word00:02:55
galacos00:02:56
which is greek for milk00:03:00
and though we once believed we lived at00:03:02
the center of the universe00:03:04
we now know that we don't even live in00:03:06
the center00:03:07
of our own galaxy00:03:10
when we look up into the night sky and00:03:12
we see this milky swath of stars that we00:03:14
call the milky way00:03:15
what we're actually seeing is a spiral00:03:18
arm of the galaxy00:03:19
that's closer to the center of the00:03:20
galaxy than we are we can't really see00:03:22
the center of the galaxy from here00:03:24
but what we can see is one of the spiral00:03:27
arms that's00:03:28
a few thousand light years closer to the00:03:30
center than we are00:03:34
as we gaze at the milky way from our00:03:36
earthbound position00:03:37
it's like looking at the edge of a coin00:03:40
we get no sense of the galaxy's real00:03:44
shape00:03:46
if however you look at a galaxy from the00:03:48
top down00:03:49
it's a disk remember and it looks it's00:03:51
like looking at a frisbee from the top00:03:52
down00:03:53
you can see its full glory00:03:56
even though it's thin you don't see how00:03:58
thin it is but you see00:03:59
its full structure00:04:01
[Music]00:04:02
you can make the analogy of the milky00:04:04
way as being very much like a city00:04:08
there's a central region there's big00:04:11
buildings00:04:13
there's a lot of action in the middle00:04:16
and that's certainly true of our galaxy00:04:20
then you move out to the suburbs where00:04:23
life is a little bit more comfortable a00:04:25
little more relaxing it's a better place00:04:26
to raise a family00:04:30
this is where we reside our solar system00:04:34
is among the milky way's spiral arms00:04:37
26 000 light years from the bustling00:04:40
center00:04:41
our galaxy is so large that it takes00:04:43
earth more than 200 million years to00:04:46
make one lap the sun is located in what would00:04:49
be just an00:04:50
average neighborhood around the city00:04:52
center but again00:04:54
if you're standing in the middle of this00:04:55
neighborhood you don't really know what00:04:56
the neighborhood on the opposite side of00:04:58
the city looks like00:04:59
because you can't see it directly00:05:04
as we move outward beyond the suburbs00:05:07
the population becomes more sparse00:05:11
and yeah you've even got sort of the00:05:12
boondocks in our galaxy00:05:14
you've got the halo where you have very00:05:16
old stars in00:05:17
sort of wide orbits around the galaxy00:05:20
the galactic sprawl doesn't stop at the00:05:22
milky way's loose and undefined halo00:05:26
it reaches far beyond our neighborhood00:05:29
and out to a group of galaxies called00:05:31
the local group if you think of the00:05:35
milky way galaxy as a city like los00:05:37
angeles then you can think of these as00:05:40
counties all within00:05:41
the state of california and together00:05:44
this local group00:05:45
makes up the entire state00:05:51
besides our huge milky way and the even00:05:54
larger andromeda galaxy00:05:58
the local group consists of close to 5000:06:00
smaller galaxies00:06:01
the closest of which are roughly 40 00000:06:04
light years away00:06:07
there are two relatively nearby dwarf00:06:08
galaxies the large00:06:10
and small clouds of magellan that orbit00:06:13
our00:06:14
milky way galaxy and are easily seen in00:06:16
the southern hemisphere00:06:18
they're small little galaxies but our00:06:20
local group00:06:21
has several dozen such galaxies sort of00:06:23
wandering around inside it00:06:25
the big galaxies are the minority00:06:29
one advantage of actually being in the00:06:31
outer edges of our galaxy00:06:33
we have a clear view of outside of our00:06:35
milky way we're able to see00:06:37
the rest of the universe our neighboring00:06:39
galaxies and galaxy00:06:40
clusters beyond our own local group of00:06:42
galaxies00:06:47
inside the milky way's halo lie massive00:06:49
globular clusters00:06:52
globular clusters are densely packed00:06:54
regions of stars00:06:55
that are all of similar composition00:07:01
these are like the ethnic neighborhoods00:07:03
of the milky way galaxy00:07:06
indeed these globular clusters formed00:07:08
when the galaxy was very young00:07:10
they are among the first stars to have00:07:12
formed some globular clusters are 12 or00:07:14
13 billion years old00:07:16
they contain a hundred thousand or even00:07:18
a million stars00:07:21
globular clusters almost as old as the00:07:24
universe itself00:07:25
gave us the first clue to our place in00:07:27
the galaxy00:07:30
we saw these globular clusters in the00:07:32
sky but their center00:07:34
was somewhere far away from us and that00:07:36
was one of our first measurements of00:07:38
where the middle of the galaxy should be00:07:40
it weren't orbiting around us but around00:07:42
an area somewhere about twenty seven00:07:45
thousand light years away00:07:48
we can never get far enough away from00:07:51
our own galaxy to actually00:07:52
see it but by looking at other galaxies00:07:56
and comparing what we know about00:07:58
our own galaxy we've got a pretty good00:08:00
picture of the milky way00:08:04
the very first time we saw galaxies00:08:06
through telescopes we didn't even know00:08:07
they were galaxies00:08:09
i thought they were just nebulae in our00:08:11
own galaxy and we were just amazed by00:08:14
the beautiful spiral shape00:08:16
so it was sort of natural for00:08:18
astronomers to classify galaxies00:08:19
according to their shape what we see00:08:23
astronomers recognize four basic00:08:25
galactic shapes00:08:27
elliptical built of old stars and which00:08:30
doesn't spin00:08:31
lenticular consisting of a bulge and a00:08:34
disc and little or no new star formation00:08:38
irregular which has no real shape at all00:08:40
like the magellanic clouds in our own00:08:42
local group00:08:44
and spiral which includes our milky way00:08:48
it's a pinwheel of young and old stars00:08:51
spinning gracefully through space00:08:54
a long time ago people thought that00:08:55
maybe an elliptical galaxy eventually00:08:57
collapses down into a spiral00:09:00
or maybe eventually spirals all come00:09:03
together and form an elliptical00:09:06
and it was sort of hard to figure out00:09:07
exactly what the sequence is00:09:09
one thing we know is that elliptical00:09:11
galaxies tend to be very large00:09:15
[Music]00:09:16
centaurus a a misshapen elliptical00:09:19
galaxy about 13 million light years away00:09:22
suggests why elliptical galaxies get so00:09:25
big00:09:27
there's a lot of evidence that there's a00:09:29
spiral galaxy in there somewhere00:09:31
that got absorbed by a larger galaxy so00:09:34
right now it's possible that these00:09:35
really big elliptical galaxies we see00:09:39
may be the mergers of several spirals00:09:41
and other types of galaxies00:09:47
our milky way isn't in danger of being00:09:49
absorbed anytime soon00:09:52
but the heart of our spiral galaxy has00:09:54
revealed a secret of its own00:09:58
only recently we discovered that the00:09:59
milky way is not a classic spiral but a00:10:01
barred spiral there's a bar of stars00:10:05
going through the center00:10:06
and the spiral arms sort of attach off00:10:07
from that bar00:10:10
spanning 27 000 light years00:10:13
it's the most popular bar in the galaxy00:10:16
30 million stars gravitate to it00:10:20
the bar of our galaxy is natural result00:10:23
of gravity00:10:24
the mutual gravitational interactions of00:10:26
the individual stars that form00:10:28
the disc of our galaxy and the bulge of00:10:30
our galaxy00:10:32
causes sometimes the stars to sort of00:10:35
bunch up into this bar00:10:37
configuration surrounding the middle of00:10:40
the milky way00:10:41
is a huge central bulge it's mostly00:10:44
composed of stars between 10 and 1100:10:47
billion years old00:10:50
the size of the bulge is linked to the00:10:52
milky way's most gripping feature of all00:10:55
a super massive black hole00:10:58
though it would easily fit in the space00:11:00
between the earth and our sun00:11:02
it's four million times more massive00:11:05
than our sun00:11:07
now that sounds like a lot but other00:11:08
galaxies have central black holes which00:11:10
extend up to a billion times the mass of00:11:13
our sun00:11:14
so whereas it's a we call our00:11:17
black hole at the center of our milky00:11:19
way a supermassive black hole00:11:21
among supermassive black holes it's kind00:11:24
of a runt00:11:28
black holes can't be seen directly00:11:30
because light00:11:31
can't escape them astronomers have00:11:34
located galactic ground zero through a00:11:36
radio source in the constellation00:11:38
sagittarius00:11:39
known as sagittarius a star00:11:42
it's creating quite a stir00:11:45
the black hole in the middle of our00:11:47
galaxy is spinning and it appears to be00:11:49
spinning00:11:50
at a rate of about one spin per 1100:11:54
minutes00:11:56
as it spins central region stars caught00:11:59
in its gravity00:12:00
gets swept along for the ride orbiting00:12:02
it00:12:03
at about 3 million miles per hour00:12:08
the black hole affects the central00:12:10
region the most00:12:12
but we can't feel its tug on earth since00:12:15
we orbit the galaxy00:12:16
far away from the center the colossal00:12:20
forces at the galaxy's heart00:12:22
are negated by the milky way's00:12:24
unimaginable size00:12:26
to me the name milky way sounds like00:12:28
something kind of comforting00:12:29
sweet you know a candy bar that sort of00:12:31
thing but the milky way galaxy is a00:12:33
monster00:12:35
it is incredibly huge so when you think00:12:38
about how vast our solar system is the00:12:40
fact that it takes00:12:41
years for the fastest spacecraft to get00:12:43
out to saturn or jupiter00:12:45
if the entire solar system were the size00:12:47
of a cd the earth would be comparable to00:12:49
the milky way00:12:50
that's huge that's absolutely00:12:52
mind-blowing and it never ceases to00:12:54
amaze me00:12:56
and the amazement goes on and on00:13:00
the galaxy's bustle and commotion may be00:13:02
concentrated in the center00:13:04
but the spectacular spiral arms have00:13:06
action of their own00:13:08
it's here that stellar neighborhoods are00:13:11
being built and stars are being born00:13:17
this is our galaxy it's a lot to take in00:13:21
and we're just beginning to probe its00:13:23
depths00:13:25
our suburban location makes it difficult00:13:28
to get the big picture00:13:30
and the hazy clouds of cosmic dust only00:13:32
block our view00:13:35
even the most powerful optical telescope00:13:38
can't pierce the darkness00:13:40
so if we want to learn more about the00:13:42
milky way we need to look beyond what00:13:44
our eyes can see00:13:49
for all its vastness and empty space the00:13:52
milky way00:13:53
is tremendously active and populated00:13:56
with some astonishing phenomena00:13:59
star clusters nebulas00:14:02
blazing invaders from other galaxies00:14:06
technology is making us rethink old00:14:09
beliefs00:14:10
and is showing us things we've never00:14:12
even considered before00:14:21
plus 15 seconds sending the new horizon00:14:24
spacecraft00:14:25
on its way to the very edge of our solar00:14:28
system00:14:31
we live on a dusty planet in a dusty00:14:34
galaxy in a dusty universe empty space00:14:38
isn't so empty optical telescopes can00:14:42
see only as far as the nearest00:14:44
dust cloud which isn't far at all00:14:49
most of our galaxy is invisible to us00:14:51
however and that's because00:14:52
the galaxy is full of dust dust clouds00:14:54
if you will00:14:55
and these dust clouds block the light00:14:57
from most of the stars in our galaxy00:15:00
it's surprising how little of the light00:15:02
from our00:15:03
rather luminous milky way galaxy reaches00:15:05
us00:15:06
the reason for that is simply because00:15:08
the dust blocks it00:15:10
but visible light is just a small sliver00:15:13
of the energy spectrum00:15:15
and radio waves rush in where visible00:15:17
light beams00:15:18
fear to tread on a foggy day00:15:22
you might not be able to see very far at00:15:24
visible wavelengths which your eye can00:15:26
see but you can still listen to your radio00:15:29
or watch your tv00:15:32
the ability of radio waves to penetrate00:15:34
space dust00:15:35
is crucial to the study of the stars00:15:38
but that use was discovered by accident00:15:43
in 1933 karl jansky an engineer at bell00:15:47
labs in new jersey00:15:48
built an antenna to track down the00:15:51
source of static00:15:52
on transatlantic telephone lines he was00:15:55
surprised to discover00:15:56
the interference was raining down from00:15:58
the center of our galaxy00:16:00
the constellation sagittarius it took00:16:03
several decades for scientists to00:16:05
realize that jansky was onto something00:16:08
celestial bodies emit electromagnetic00:16:10
radiation00:16:11
and thus radio astronomy was born00:16:15
but radio waves were just the beginning00:16:19
because the human eye can't see all the00:16:20
light that's available we have to resort00:16:22
to technology00:16:23
and one of the best ways of seeing the00:16:24
universe in a very different way00:16:26
is with an infrared camera an infrared00:16:29
camera sees only the wavelengths00:16:31
generated by heat00:16:32
then converts it to something the human00:16:35
eye can see00:16:37
there actually is no visible light at00:16:38
all that passes through this lens this00:16:40
lens only lets heat light through00:16:42
and then you can see what everything00:16:43
looks like in infrared light00:16:46
three two main engines start in 200300:16:50
the spitzer space telescope equipped00:16:52
with a battery of infrared cameras00:16:55
was launched into space00:16:58
its mission is to explore some of the00:17:01
youngest stars and farthest galaxies00:17:03
in the universe the instruments that00:17:06
spitzer has on it are actually00:17:08
many times millions of times more00:17:09
sensitive than these cameras00:17:11
but they're basically the same thing00:17:14
this camera doesn't peer into the00:17:16
heavens00:17:19
but is used by firefighters to save00:17:21
lives right here on earth00:17:27
the camera can see through a00:17:28
smoke-filled room to read the body heat00:17:31
from an unconscious or immobilized00:17:33
victim00:17:37
the same technology has enabled00:17:39
astronomer susan stolovy00:17:41
to see 26 000 light years away00:17:44
visualizing the center of the galaxy as00:17:47
never before00:17:49
this high resolution mosaic was00:17:51
assembled from00:17:53
roughly 12 000 individual images taken00:17:55
from the spitzer space telescope00:17:58
even though that sounds like a lot of00:17:59
data and it is it only took about 1600:18:02
hours of telescope time00:18:04
this particular region of the galactic00:18:06
center spans an area of the sky00:18:08
that's equivalent to four full moons in00:18:10
one direction and three full wounds in00:18:12
the other00:18:14
that's the equivalent of 900 light years00:18:16
across00:18:17
by 700 light years high00:18:20
a small fraction of what's out there to00:18:22
see but a phenomenal achievement00:18:24
nonetheless00:18:27
just a few decades ago the galactic00:18:29
center was not a subject of study00:18:31
because00:18:32
you couldn't see it visually nothing00:18:34
gets through only one light wave and a00:18:36
trillion can penetrate the dust but if you00:18:40
go into the infrared or use radio00:18:42
astronomy or x-ray astronomy00:18:44
you can see what's going on there00:18:47
different wavelengths of the00:18:48
electromagnetic spectrum can reveal00:18:50
different00:18:51
aspects of the galaxy because they00:18:54
penetrate celestial objects differently00:18:57
[Music]00:18:59
radio waves have the lowest energy or00:19:02
longest wavelength00:19:03
but most celestial objects emit them00:19:07
then comes infrared visible light00:19:10
ultraviolet high energy x-rays00:19:14
with wavelengths about the size of an00:19:16
atom are emitted00:19:17
by black holes and supernovas the00:19:20
highest energy gamma rays come from the00:19:22
collision or decay of subatomic00:19:24
particles00:19:25
like when stars explode at billions of00:19:28
degrees00:19:30
together these waves give astronomers a00:19:32
more complete picture of the activity00:19:35
and shape of our galaxy00:19:39
many if not all of the wavelengths are00:19:41
needed to study the cosmos00:19:43
the various wavelengths of the00:19:45
electromagnetic spectrum00:19:46
are similar to the strings on a violin00:19:54
in music many wavelengths of sound are00:19:56
used to communicate a musical idea00:19:59
this piece has a very large range from a00:20:01
low note to a high note00:20:10
if we were to restrict ourselves to the00:20:11
visible light spectrum00:20:13
it's almost as if we were only to hear00:20:15
two notes in the middle of that piece00:20:21
using alternate wavelengths the more we00:20:24
look the more we're discovering00:20:29
just recently we've discovered that00:20:30
there are two small galaxies colliding00:20:32
with the milky way right now00:20:34
and the only reason we didn't know they00:20:35
were there is because there was so much00:20:38
dust in the disk of our galaxy we00:20:40
couldn't see them00:20:41
we're living inside this cloud and it's00:20:43
something we're not aware of but with00:20:45
infrared light00:20:46
you can cut through that dust and the00:20:49
minute we turned infrared telescopes to00:20:51
the sky we saw these little galaxies up there00:20:54
coming right at us00:20:57
[Music]00:20:58
from our cockeyed position in the milky00:21:00
way it's difficult to gauge what our00:21:03
galaxy really looks like00:21:06
radio and optical astronomy give us a00:21:08
glimpse of its features00:21:10
but to get the big picture we need to00:21:12
look outward00:21:15
so the way we gain some understanding of00:21:17
our own galaxy is first of all by00:21:18
looking at other galaxies and seeing00:21:20
what they look like00:21:22
and seeing things in other galaxies that00:21:24
correspond00:21:25
to things that we see in our own galaxy00:21:27
like clouds of gas that are kind of00:21:29
lined up along what looks like a spiral00:21:31
arm you know we can see parts of spiral arms00:21:33
in our own galaxy and we figure that00:21:35
they're all connected00:21:36
kind of like the spiral arms of other00:21:38
galaxies that we can see from the00:21:40
outside00:21:42
we know that the milky way's four main00:21:44
spiral arms00:21:45
swing out from the downtown center like00:21:48
wide streets00:21:50
from the inside out they're named norma00:21:55
scudum crux sagittarius00:21:59
and perseus00:22:03
if the arms are the galaxy's suburbs00:22:06
then our solar system lives on a quiet00:22:08
dead-end street00:22:10
between sagittarius and perseus on00:22:12
what's called00:22:13
the orion spur00:22:16
all the stars in the milky way add up to00:22:19
a community of about00:22:20
200 to 400 billion and they're on the00:22:23
move00:22:24
we are orbiting around the galaxy we00:22:26
change our position00:22:28
so far we think the sun has always been00:22:29
about the same distance away from the00:22:31
center but we've been in and out of pretty much00:22:33
every spiral arm that there is00:22:37
the spirals are called density waves00:22:40
areas where the stars and gas get pushed00:22:42
together00:22:44
as the density waves spiral around the00:22:47
billions of stars00:22:48
ride over and through them00:22:52
when you think about watching the tour00:22:53
de france and you see all of these00:22:55
bicycles they're all moving forward00:22:57
sometimes they kind of clump up around00:22:58
one bicyclist and sometimes00:23:00
they're stretched out that's sort of00:23:02
what the spiral arms are like00:23:03
that the stars are going around like the00:23:05
bicyclist sometimes in clumpy areas and00:23:07
sometimes in more00:23:08
spread out areas but they keep going00:23:10
around the center00:23:14
stars don't usually travel alone00:23:17
while giant globular clusters populate00:23:19
the galaxy's halo00:23:21
the galactic disk has open or galactic00:23:24
clusters00:23:26
these bundles of young stars are barely00:23:28
held together00:23:29
by their mutual gravity now open cluster00:23:33
implies that the stars are actually free00:23:35
to go it is open00:23:37
so this is a cluster usually of many00:23:39
stars that have formed together00:23:40
all from one of these giant clouds of00:23:42
dust and gas00:23:43
over time they're going to move away00:23:45
from each other distribute themselves00:23:47
around the galaxy00:23:50
astronomers have counted about 20 00000:23:53
open clusters in the galaxy00:23:55
the pleiades is the one found nearest to00:23:58
the earth00:23:59
it formed a hundred million years ago00:24:01
and will be around at least00:24:03
twice that long before the galaxy's00:24:05
spiral arms00:24:06
tear it apart00:24:09
closer to home our own sun orbiting in00:24:12
solitude00:24:13
may have once been part of an open00:24:15
cluster star00:24:16
that struck out on its own the sun00:24:20
the star clusters our own planet in fact00:24:23
the entire galaxy00:24:25
and the universe beyond are built of00:24:28
dust and gases these particles00:24:31
that now block our view are what got us00:24:34
here in the first place00:24:36
and the star-making machinery is still00:24:44
cranking00:24:46
nothing beats the spectacle of a00:24:48
glorious00:24:49
sunset but we owe it all00:24:53
to dust and gas00:24:56
the setting sun appears yellow orange or00:24:59
even red00:25:00
for two reasons first of all the00:25:02
molecules of air in the atmosphere are00:25:04
scattering the violet blue and green00:25:06
light00:25:07
out of our line of sight leaving the00:25:09
yellows oranges and reds00:25:11
to reach our eyes and second of all00:25:13
particles like dust or smoke or smog00:25:16
in the atmosphere absorb blue light more00:25:19
than they do red light00:25:23
even the grandeur of a blue sky is00:25:25
really00:25:26
an optical illusion why is the sky blue00:25:30
there's nothing blue about the gases of00:25:32
our atmosphere00:25:33
but as sunlight comes through our00:25:34
atmosphere the shorter wavelengths the00:25:37
blue light gets scattered00:25:39
more than the longer wavelengths do so00:25:41
if you look at any particular part of00:25:42
the sky you're more likely to see blue00:25:44
light being scattered towards your eye00:25:52
space is dark because there aren't00:25:54
enough gas or dust particles to reflect00:25:56
the light00:25:57
of a billion stars00:26:00
and though space may be a vacuum it's00:26:03
not perfect00:26:05
the galactic disk the largest portion of00:26:08
the milky way00:26:09
owes about 15 of its mass to dust and00:26:13
gas00:26:15
gas clouds can span hundreds or even00:26:18
thousands of light years00:26:19
providing the raw material that fires00:26:22
the galaxy00:26:23
these regions of cosmic dust and gas are00:26:26
called nebulae00:26:28
and they produce effects rivaling00:26:30
anything seen00:26:31
on earth00:26:34
a good example is the orion nebula in00:26:37
the constellation orion00:26:39
this region is active with stellar00:26:41
formation which makes the gas around the00:26:44
stars glow it's literally fluorescing00:26:48
in response to the light coming out of00:26:50
the massive stars that are near the00:26:52
nebula00:26:53
and this nebula literally glows and can00:26:56
be seen you can see it with your naked00:26:58
eye00:27:00
when you see the orion nebula in a real00:27:02
way those are baby pictures for us00:27:04
five billion years ago we were in a00:27:06
glowing hot nebula00:27:08
and the sun and the planets were forming00:27:10
together under the influence of gravity00:27:14
orion which contains hot stars ionizing00:27:17
its gases with ultraviolet light00:27:19
is called a diffuse or emission nebula00:27:24
astronomers classify two other00:27:26
categories of nebulae00:27:29
some nebulae are what are called00:27:30
reflection nebulae they're simply00:27:33
the dust in these nebulas simply00:27:34
reflecting the starlight from the bright00:27:36
star nearby00:27:40
the witch head nebula is an example of a00:27:42
reflection nebula00:27:44
borrowing light from the star rigel00:27:48
reflection nebulae appear blue for the00:27:50
same reason00:27:51
our sky does blue light is more easily00:27:54
reflected than red00:27:57
and last there are dark nebulae like the00:28:00
horse head00:28:04
when low-mass stars like our sun die00:28:07
they form00:28:08
another kind of nebula called a00:28:10
planetary nebula00:28:14
these dim short-lived nebulae like the00:28:17
cat's eye nebula00:28:18
spew elements back into the galaxy00:28:21
these may become raw materials for new00:28:24
suns00:28:25
and new planets00:28:32
just as dying stars spew out clouds of00:28:34
dust and gas00:28:36
dust and gas can come together to form00:28:39
stars00:28:43
at a construction site you have old00:28:45
buildings being torn down00:28:47
and new buildings going up and it's very00:28:49
much the same in the milky way galaxy00:28:52
you have old stars explode and they cast00:28:56
out new material00:28:57
raw material gas and dust that can be00:28:59
used to form00:29:00
new stars00:29:01
[Music]00:29:05
nebulae are the galaxy's recycling00:29:07
centers00:29:08
where old becomes new again00:29:12
recycling is not just a good idea here00:29:14
on earth00:29:15
it's a natural cosmic law00:29:18
in fact our own bodies are made out of00:29:20
recycled material00:29:22
from earlier generations of stars that00:29:24
had dispersed material into the00:29:26
interstellar medium before our own solar00:29:28
system formed00:29:30
each generation of stars creates heavier00:29:33
elements00:29:34
which become the ingredients for00:29:36
everything in the universe00:29:38
most of the galaxy's hot young stars get00:29:41
built in the milky way's spiral arms00:29:45
as gas clouds orbit the center of the00:29:47
galaxy like the stars do00:29:50
they get squeezed as they go through a00:29:52
spiral arm00:29:54
remember a spiral arm is simply a wave00:29:57
in the pattern of stars and because00:30:00
stars are denser00:30:01
there the gas clouds that orbit through00:30:04
it tend to get compressed00:30:05
that compression allows gravity to get a00:30:08
hold00:30:09
of that gas and cause it to collapse to00:30:11
form stars more readily there than00:30:13
anywhere else00:30:17
stars often die in the spiral arms00:30:19
because they are formed here more00:30:21
frequently00:30:22
victims of their own enormous mass00:30:26
the more massive stars are extremely00:30:28
powerful extremely luminous00:30:30
and to be that luminous they have to use00:30:32
up their00:30:33
their energy source very quickly so00:30:36
massive stars00:30:37
live only short lives and they are thus00:30:41
found in or near their birthplaces00:30:44
the spiral arms because they simply00:30:47
don't have enough time00:30:48
to wander away from the places where00:30:50
they were born00:30:54
although we can anticipate the future of00:30:56
some stars00:30:57
it's often difficult to learn their00:30:59
history00:31:00
but new techniques are revealing new00:31:02
secrets about a well-studied star in the00:31:05
milky way00:31:06
called myra a myra has actually been a00:31:09
favorite star of astronomers for 40000:31:11
years it's a very easily visible star in00:31:13
the night sky00:31:15
recently the galax spacecraft the galaxy00:31:18
evolution explorer00:31:20
photographed myra in invisible00:31:22
ultraviolet light00:31:24
and revealed that it's leaving a trail00:31:26
13 light years long00:31:28
behind it we think that's actually00:31:31
caused by the fact that as the star00:31:32
plows through00:31:33
the gas the gas heats up in a bow shot00:31:36
very much like waves breaking up against00:31:38
a boat and then that streams out into a00:31:41
wake of hot material00:31:43
you're actually looking at myra acting00:31:45
very much like a boat plowing through00:31:46
the water00:31:47
when you look at how fast myra is going00:31:49
right now about 291 000 miles an hour00:31:52
and you do the calculations that long00:31:54
tail is its path00:31:55
the last 30 000 years we can't predict00:31:58
exactly where the sun will go00:32:00
in its orbit around the milky way00:32:01
there's all kinds of things that could00:32:02
interact with00:32:03
but here we have the history of one star00:32:05
we know this is the path it took00:32:08
and that'll help us model how the galaxy00:32:10
works and how all the stars move around00:32:12
the middle of the galaxy00:32:15
within the milky way's suburban spiral00:32:18
arms00:32:19
young stars enjoy plenty of space to00:32:21
move around00:32:23
as we move into the galactic bulge00:32:25
conditions get much more crowded00:32:27
and urban closest star to the sun is a00:32:31
little more than four light years away00:32:33
and when we look up into the night sky00:32:35
even on a perfectly clear night00:32:37
with no lights around you can't see more00:32:39
than about two or three thousand stars00:32:44
but if our planet was down in the middle00:32:47
of the galaxy00:32:48
there would be a million stars in the00:32:51
night sky00:32:52
as bright as the brightest star that00:32:53
we've ever seen in our sky00:32:55
and it would be so bright that in fact00:32:57
it wouldn't be nighttime it would be00:32:58
daytime all the time00:33:02
life as we know it would be completely00:33:04
different00:33:05
so what do we owe our position to00:33:08
scientists believe that gravity has a00:33:11
lot to do with it00:33:16
gravity is the power that drives the00:33:19
galaxy00:33:21
and at the galaxy's center churns the00:33:23
engine00:33:24
it feeds galaxies are00:33:27
like a city in that they are ever00:33:30
changing and you're constantly being rebuilt and00:33:33
reinvigorated00:33:36
there's no question that the milky way a00:33:38
few billion years ago looked a lot00:33:40
different than it does today00:33:42
it probably was smaller it probably00:33:45
didn't have the beautiful spiral shape00:33:47
that we see today as things collapse under gravity00:33:51
you tend to naturally form a disc you'll00:33:53
notice there are discs everywhere00:33:55
our solar system is a disc our galaxy is00:33:57
a disc00:33:58
so the stars all start rotating in the00:34:00
same direction00:34:04
just as in a city not all the stars in00:34:07
the galaxy are natives00:34:09
some stars born beyond the milky way00:34:12
settle here and begin to make their mark00:34:16
but then if another galaxy comes by the00:34:18
gravity affects the way the stars move00:34:21
and this may initiate the spiral arms00:34:24
so in fact our spiral shape may be some00:34:27
evidence00:34:28
that the milky way is composed of more00:34:30
than one small galaxies that came00:34:32
together a long time ago00:34:35
historically the center of the galaxy00:34:38
has been an impenetrable mystery until we developed00:34:43
x-ray vision one of the first ways we00:34:46
really identified where the exact00:34:48
center of the galaxy was was with an00:34:49
x-ray telescope00:34:51
well the x-rays were able to pass00:34:52
through all of the dust and gas00:34:54
in the disk of our galaxy and so even00:34:57
though we can't really see00:34:58
this bright center to the galaxy in00:35:00
x-rays there's this giant glowing hot00:35:03
source right in the middle00:35:05
the x-ray emitter sagittarius a star00:35:08
is associated with the super massive00:35:10
black hole00:35:11
in the milky way's center00:35:14
by definition a black hole doesn't allow00:35:16
light or even00:35:17
x-rays to escape the radiation comes00:35:21
from gas00:35:22
caught in its gravity spun and heated00:35:25
to millions of degrees00:35:28
they're moving at extremely high00:35:30
velocities00:35:32
for example the more extreme cases that00:35:34
we've been able to observe00:35:36
the stars are moving as they pass by the00:35:39
black hole00:35:40
at a speed of 10 000 kilometers per00:35:43
second00:35:44
that's like going around the world in00:35:46
four seconds00:35:49
and we're talking about a whole star00:35:51
moving at that speed00:35:54
when we watch stars orbiting the very00:35:56
center of our galaxy it's obvious that00:35:58
there's some sort of invisible monster00:35:59
there00:36:02
they're orbiting around a giant mass and00:36:04
the orbits of the stars imply that00:36:06
there's about three to four million00:36:08
times the mass of the sun00:36:09
in the very center of our galaxy we're00:36:12
not sure which came first the galaxy or00:36:14
the black hole00:36:15
but we know that it's there and it's00:36:17
tremendous00:36:20
for all its power and weirdness the00:36:22
supermassive black hole is pretty00:36:24
typical00:36:25
for a galaxy the size of the milky way00:36:29
other spiral galaxies and big elliptical00:36:32
galaxies00:36:33
also seem to have supermassive black00:36:35
holes in their middle00:36:37
ranging from a million times the mass of00:36:39
our sun00:36:40
up to several billion times the mass of00:36:42
our sun00:36:45
the stars surrounding the black hole are00:36:47
ancient00:36:49
many are red giants hundreds of times00:36:51
bigger than our sun00:36:54
the galactic center is crowded with them00:36:57
like an urban downtown crowded with people00:37:01
and stars like people can be pushy00:37:05
most stars in the gladiator center00:37:06
simply just keep orbiting the central00:37:08
black hole00:37:09
but in the galactic center there's so00:37:11
many stars packed so close together00:37:13
that stars are constantly nudging each00:37:15
other a little bit gravitationally00:37:17
and their orbits are being perturbed00:37:19
changed a little bit00:37:22
a bump star can get stripped of its00:37:24
atmosphere00:37:25
leaving just its orbiting core or rarely00:37:29
it can tumble into the black hole and00:37:32
vanish00:37:34
but something else is happening around00:37:36
the black hole00:37:38
this turbulent dangerous neighborhood is00:37:41
also a stellar nursery the stars that we're00:37:46
observing moving fastest around the00:37:47
black hole are the young stars that00:37:50
uh have very recently formed and00:37:53
it's something we call the paradox of00:37:54
youth because it's00:37:56
it's hard to imagine how to form these00:37:58
massive young stars00:38:00
in the presence of a black hole and yet00:38:01
there they are00:38:04
recently astronomers discovered that not00:38:07
all stars caught in the black hole's00:38:09
grip are doomed to stay there a few00:38:13
managed to break away and see the00:38:16
universe00:38:20
barreling through the universe at one00:38:22
and a half million miles per hour00:38:25
hyper velocity stars are the escapees of00:38:28
the galaxy00:38:30
and what's interesting about high00:38:32
velocity stars is the only way to00:38:33
explain their extreme velocities00:38:35
is that they're rejected by a00:38:36
supermassive black hole00:38:39
for a star to go ballistic takes a very00:38:42
specific set of circumstances00:38:45
and in fact it requires two stars00:38:49
most of the stars you see in the sky are00:38:51
not single stars00:38:53
but pairs or binary stars00:38:58
they orbit around each other linked by00:39:01
gravity's embrace00:39:03
but a star pair in the galactic center00:39:06
might get jostled by surrounding stars00:39:08
and stray too close to the black hole00:39:12
when that happens the moment that the00:39:14
gravitational pull of the00:39:16
black hole exceeds the gravity that's00:39:19
binding the two stars together00:39:21
the pair of stars is broken apart one of00:39:24
the stars will be captured by the black00:39:25
hole00:39:26
usually into a very tight orbit around00:39:28
the black hole and the other star will00:39:30
then gain all the energy of that system00:39:31
and be ejected with this incredible00:39:33
velocity00:39:35
if the galaxy were a city where most of00:39:37
the stars would be cars or pedestrians00:39:40
a high velocity star would be more like00:39:42
an airplane00:39:44
or a high-speed train rushing out of the00:39:46
country00:39:48
if you're on high flossie star the ride00:39:51
would be00:39:52
quite amazing the sky would be covered00:39:54
with stars as bright as the full moon in00:39:56
every direction00:39:57
but that view would quickly change00:39:59
because the hypoplasty star moved so00:40:00
quickly out of the galaxy00:40:01
the stars appear fewer and fewer in the00:40:03
night sky00:40:06
the galaxy is constantly in motion like00:40:09
a giant wheel00:40:10
or a sprawling metropolis00:40:14
in the heart of town the supermassive00:40:16
black hole's gravity00:40:17
whips stars around in an orbit of around00:40:20
11 minutes00:40:23
where the earth sits two-thirds of the00:40:25
way out on a spiral arm00:40:27
we traverse the milky way once every 25000:40:31
million years00:40:34
our solar system has been around the00:40:36
block only 18 times00:40:38
since it formed the milky way's00:40:41
incomprehensible size makes it easy to00:40:44
forget00:40:45
it's just one small part of an expanding00:40:48
universe00:40:50
when people hear about the expanding00:40:51
universe a common misconception is that00:40:53
everything is expanding00:40:54
and in fact i'm not expanding right now00:40:57
my atoms are the same size my cells are00:40:59
the same size00:41:01
the earth is not getting farther away00:41:03
from the sun00:41:04
the expansion of the universe only00:41:06
applies to celestial objects that aren't00:41:08
bound together by gravity00:41:11
since the planets within the milky way00:41:13
have stronger gravitational pulls than00:41:15
the expanding forces outside00:41:17
our galaxy the expansion of the universe00:41:20
doesn't affect our solar system00:41:24
our own milky way a spiral galaxy is on00:41:27
a collision course with another spiral00:41:29
galaxy00:41:30
the largest spiral near us and that is00:41:32
the andromeda galaxy00:41:34
we think that in maybe three or four00:41:36
billion years00:41:38
our two galaxies may merge together00:41:40
it'll be very interesting to see what00:41:41
happens00:41:44
what probably won't happen is a00:41:46
collision of stars00:41:48
even though both galaxies contain00:41:50
billions of stars00:41:51
the space between them is enormous00:41:55
they will gravitationally interact00:41:58
changing their direction00:41:59
and motion eventually the merged spirals00:42:03
will settle down00:42:04
to become an elliptical galaxy00:42:08
essentially all of the several dozen00:42:10
galaxies in our local group00:42:12
will be part of one super galaxy00:42:16
and then gradually that super galaxy00:42:18
will start losing stars because of00:42:20
gravitational interactions00:42:21
among the stars within that galaxy some00:42:24
will get00:42:25
flung away into intergalactic space00:42:30
when it first formed the milky way built00:42:33
stars at a rapid pace00:42:35
using raw materials that were ejected in00:42:37
space from the big bang00:42:39
as the galaxy aged the star production00:42:42
slowed down00:42:43
from a few hundred a year to about four00:42:46
to six new stars each year00:42:47
today over time the milky way galaxy has00:42:51
changed dramatically and we don't know00:42:52
exactly what it looked like00:42:54
long ago but probably early on there was00:42:56
a lot more gas and dust and probably00:42:58
fewer stars00:42:59
and you had a lot of very large very00:43:01
massive stars that would have formed00:43:03
early on00:43:04
and then these early stars exploded00:43:07
fantastically00:43:08
and spat out new material heavier metals00:43:11
that could be used to form00:43:13
smaller second generation and then third00:43:15
generation stars00:43:17
[Music]00:43:19
some younger galaxies are still enjoying00:43:22
that kind of building boom00:43:25
we can see some galaxies where the rate00:43:27
of star formation is very high00:43:29
compared to our galaxy those are called00:43:31
starburst galaxies00:43:33
the rate of star formation there can be00:43:35
anywhere from 10 to 100 times what it is00:43:37
now in our galaxy00:43:39
with every generation star production00:43:42
slows down00:43:43
and the milky way has been in business00:43:45
for 13 billion years00:43:49
one of the reasons that the rate of star00:43:50
formation in our galaxy has changed over00:43:52
time00:43:53
going from a very high rate to the00:43:55
current modest rate of star formation is00:43:57
because the00:43:58
gas is being used up gas is used up to00:44:01
form stars00:44:03
and we're running out of gas literally00:44:06
eventually over trillions of years star00:44:09
formation will stop00:44:11
completely the great galactic00:44:14
construction project will shut down00:44:18
and one by one the twinkling stars00:44:22
will fade away00:44:39
youDescription:
We used to think that Earth was at the center of the universe, but now we know we're not even at the center of our own galaxy. Countless wonders exist between where earth is situated, in Season 2, Episode 4, "The Milky Way." #TheUniverse Subscribe for more from The Universe and other great HISTORY shows: https://www.youtube.com/user/HistoryChannel/?sub_confirmation=1 Find out more about the series on our site: https://www.historytv.fi/fi Check out exclusive HISTORY content: History Newsletter - https://www.historytv.fi/fi Website - https://www.historytv.fi/fi Facebook - https://www.facebook.com/unsupportedbrowser Twitter - https://histv.co/Twitter HISTORY® is the leading destination for award-winning original series and specials that connect viewers with history in an informative, immersive, and entertaining manner across all platforms. The network’s all-original programming slate features a roster of hit series, premium documentaries, and scripted event programming.
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Which format of "The Universe: Countless Wonders of the Milky Way (S2, E4) | Full Episode | History" video should I choose?
The best quality formats are FullHD (1080p), 2K (1440p), 4K (2160p) and 8K (4320p). The higher the resolution of your screen, the higher the video quality should be. However, there are other factors to consider: download speed, amount of free space, and device performance during playback.
Why does my computer freeze when loading a "The Universe: Countless Wonders of the Milky Way (S2, E4) | Full Episode | History" video?
The browser/computer should not freeze completely! If this happens, please report it with a link to the video. Sometimes videos cannot be downloaded directly in a suitable format, so we have added the ability to convert the file to the desired format. In some cases, this process may actively use computer resources.
How can I download "The Universe: Countless Wonders of the Milky Way (S2, E4) | Full Episode | History" video to my phone?
You can download a video to your smartphone using the website or the PWA application UDL Lite. It is also possible to send a download link via QR code using the UDL Helper extension.
How can I download an audio track (music) to MP3 "The Universe: Countless Wonders of the Milky Way (S2, E4) | Full Episode | History"?
The most convenient way is to use the UDL Client program, which supports converting video to MP3 format. In some cases, MP3 can also be downloaded through the UDL Helper extension.
How can I save a frame from a video "The Universe: Countless Wonders of the Milky Way (S2, E4) | Full Episode | History"?
This feature is available in the UDL Helper extension. Make sure that "Show the video snapshot button" is checked in the settings. A camera icon should appear in the lower right corner of the player to the left of the "Settings" icon. When you click on it, the current frame from the video will be saved to your computer in JPEG format.
What's the price of all this stuff?
It costs nothing. Our services are absolutely free for all users. There are no PRO subscriptions, no restrictions on the number or maximum length of downloaded videos.