1
00:00:07,215 --> 00:00:07,841
This is a group

2
00:00:07,841 --> 00:00:11,386
of galaxies known as Stephan's Quintet.

3
00:00:11,720 --> 00:00:13,430
Quintet meaning five, of course.

4
00:00:13,430 --> 00:00:14,681
And you can see them here.

5
00:00:14,681 --> 00:00:17,892
One, two, three, four, five.

6
00:00:18,101 --> 00:00:21,980
Although, it's really just a visual
quintet because it turns out that

7
00:00:21,980 --> 00:00:26,359
the galaxy here on the left
is a lot closer than the other four.

8
00:00:26,359 --> 00:00:31,406
The other four are at a distance
of about 290 million light years away.

9
00:00:31,656 --> 00:00:35,410
And the nearby one
is only about 40 million light years away.

10
00:00:35,660 --> 00:00:38,830
You can also see its difference
in color and details.

11
00:00:39,372 --> 00:00:41,750
They're still all in our deep universe.

12
00:00:41,750 --> 00:00:44,544
And they make
for a very interesting picture.

13
00:00:47,630 --> 00:00:48,465
The ones on the right

14
00:00:48,465 --> 00:00:52,302
are actually gravitationally interacting
with each other.

15
00:00:52,427 --> 00:00:54,596
They are feeling each other's pull,

16
00:00:54,596 --> 00:00:58,475
and that's creating structural changes
in these galaxies.

17
00:00:58,475 --> 00:01:03,313
You can even see evidence that the spiral
structure in these galaxies is becoming

18
00:01:03,313 --> 00:01:07,108
distorted as they feel each other's
gravitational tug.

19
00:01:07,108 --> 00:01:12,530
It's creating long tails of stars
and star formation between the galaxies.

20
00:01:12,572 --> 00:01:16,284
Because as you have more regions
where gas is stirred up and compacted,

21
00:01:16,284 --> 00:01:19,412
that's the recipe
for more clumps of gas in

22
00:01:19,412 --> 00:01:22,457
each of these galaxies
to collapse and form more stars.

23
00:01:23,166 --> 00:01:27,170
You can see these two are closer
in this dance of merging.

24
00:01:27,170 --> 00:01:31,549
And all of this is evidence
of the merging process of galaxies

25
00:01:31,549 --> 00:01:35,095
that we now know is very common
in the history of our universe.

26
00:01:35,136 --> 00:01:38,765
Galaxies that are close enough
to each other will feel each other's

27
00:01:38,765 --> 00:01:40,183
gravitational pull.

28
00:01:40,183 --> 00:01:41,851
They'll come toward each other.

29
00:01:41,851 --> 00:01:45,647
that creates a little dance
as they orbit around each other, sometimes

30
00:01:45,688 --> 00:01:49,067
go through each other
and they distort each other structure.

31
00:01:49,109 --> 00:01:52,403
So you can see this cosmic dance
going on right now

32
00:01:52,403 --> 00:01:56,074
in Stephan's Quintet, and you can see
some of the impacts of that.

33
00:01:59,786 --> 00:02:00,161
So we

34
00:02:00,161 --> 00:02:03,164
can see that
the galaxies are connected to each other.

35
00:02:03,164 --> 00:02:07,210
Now and they're showing us
that merging is an important part

36
00:02:07,210 --> 00:02:10,505
of forming structure
in stars and galaxies.

37
00:02:10,588 --> 00:02:11,548
We actually believe

38
00:02:11,548 --> 00:02:16,469
that most galaxies have gone through
at least one merger in cosmic history.

39
00:02:16,553 --> 00:02:19,472
We believe our Milky Way
has and will again.

40
00:02:20,140 --> 00:02:24,978
So we want to watch this dramatic dance
so that we understand how galaxies

41
00:02:24,978 --> 00:02:29,691
have formed and grown over cosmic history,
including our own Milky Way.