1
00:00:00,000 --> 00:00:00,870
[MUSIC PLAYING]

2
00:00:00,870 --> 00:00:02,280
Are all galaxies the same?

3
00:00:02,280 --> 00:00:07,450


4
00:00:07,450 --> 00:00:10,120
We live on a planet in
a single solar system,

5
00:00:10,120 --> 00:00:14,290
inside a large galaxy made up
of a hundred billion stars.

6
00:00:14,290 --> 00:00:18,010
A supermassive black hole equal
to the weight of a few million

7
00:00:18,010 --> 00:00:21,040
suns anchors the
center of our galaxy.

8
00:00:21,040 --> 00:00:23,380
Our universe has
hundreds of billions

9
00:00:23,380 --> 00:00:26,920
of galaxies, each containing
stars like our sun.

10
00:00:26,920 --> 00:00:30,130
Galaxies range in size
from ones with 1,000 stars

11
00:00:30,130 --> 00:00:32,950
to ones with a
trillion or more stars.

12
00:00:32,950 --> 00:00:37,750
That means we have a lot
of places to explore.

13
00:00:37,750 --> 00:00:39,970
Edwin Hubble was one of
the first astronomers

14
00:00:39,970 --> 00:00:42,740
to discover that our universe
isn't just sitting still,

15
00:00:42,740 --> 00:00:44,740
but it's expanding.

16
00:00:44,740 --> 00:00:46,660
Hubble also grouped
galaxies by how

17
00:00:46,660 --> 00:00:49,810
they looked because not
all galaxies are the same.

18
00:00:49,810 --> 00:00:52,930
He described a few
distinct types.

19
00:00:52,930 --> 00:00:55,750
Elliptical galaxies, which
have no easily defined

20
00:00:55,750 --> 00:00:58,420
shape with stars that
move chaotically.

21
00:00:58,420 --> 00:01:00,910
And spirals or disk
galaxies, which

22
00:01:00,910 --> 00:01:03,580
are flat with pinwheel
spiral arms that

23
00:01:03,580 --> 00:01:05,379
spread out from the center.

24
00:01:05,379 --> 00:01:07,660
As Hubble began to
classify galaxies,

25
00:01:07,660 --> 00:01:10,720
he quickly discovered many
galaxies didn't fit neatly

26
00:01:10,720 --> 00:01:12,370
into his categories.

27
00:01:12,370 --> 00:01:15,010
Was it possible that
galaxies change from one type

28
00:01:15,010 --> 00:01:17,470
to another over eons?

29
00:01:17,470 --> 00:01:20,860
Even our own Milky Way
galaxy has been changing.

30
00:01:20,860 --> 00:01:23,140
There are a handful
of smaller galaxies,

31
00:01:23,140 --> 00:01:27,220
such as the Magellanic
clouds, Fornax, Sculptor, Leo

32
00:01:27,220 --> 00:01:29,290
and others that orbit around us.

33
00:01:29,290 --> 00:01:31,510
The powerful gravity
of the Milky Way

34
00:01:31,510 --> 00:01:34,360
affects these nearby
galaxies, either causing

35
00:01:34,360 --> 00:01:36,370
them to be ripped
apart, or pulling them

36
00:01:36,370 --> 00:01:37,360
into merge with ours.

37
00:01:37,360 --> 00:01:49,410
[MUSIC PLAYING]

38
00:01:49,410 --> 00:01:53,067