WEBVTT FILE

1
00:00:00.010 --> 00:00:03.040
Bell Tone

2
00:00:03.060 --> 00:00:07.090
Hi, this is Alex Young. I'm a heliophysicist

3
00:00:07.110 --> 00:00:11.140
at NASA's Goddard Space Flight Center. And many of you may have seen the

4
00:00:11.160 --> 00:00:15.190
video recently that showed the sun for the past three years

5
00:00:15.210 --> 00:00:19.240
observed by the Solar Dynamics Observatory. I also saw this recently,

6
00:00:19.260 --> 00:00:23.340
thought it was a really cool video and I want to share with you some of the interesting

7
00:00:23.360 --> 00:00:27.400
features I noticed in the video.  -MUSIC-

8
00:00:27.420 --> 00:00:31.460
If you see that big black disk that moves over the sun, that's

9
00:00:31.480 --> 00:00:35.540
the moon--what we call a lunar transit. That's when the moon is moving

10
00:00:35.560 --> 00:00:39.600
between the sun and the SDO spacecraft.

11
00:00:39.620 --> 00:00:43.660
It almost looks like a perfect circle, but if you look really

12
00:00:43.680 --> 00:00:47.740
really close on the edge, you see these little tiny humps. Those

13
00:00:47.760 --> 00:00:51.820
are the mountains on the moon. Just an amazing thing you can see with

14
00:00:51.840 --> 00:00:55.940
these incredibly high-resolution cameras. We're looking

15
00:00:55.960 --> 00:01:00.020
at the 171 angstrom wavelength. This is extreme

16
00:01:00.040 --> 00:01:04.160
ultraviolet. And it's showing us the solar atmosphere at about

17
00:01:04.180 --> 00:01:08.180
a million degrees Fahrenheit. And if you look at this image, you can

18
00:01:08.200 --> 00:01:12.210
see all of these bright patches, these are active

19
00:01:12.230 --> 00:01:16.240
regions associated with sunspots. And then you even see

20
00:01:16.260 --> 00:01:20.270
loops. These are huge structures many times the size of

21
00:01:20.290 --> 00:01:24.300
Earth that are magnetic fields holding in

22
00:01:24.320 --> 00:01:28.310
this hot solar plasma. One of the

23
00:01:28.330 --> 00:01:32.340
things that's amazing about this is there's so much stuff going on in this

24
00:01:32.360 --> 00:01:36.360
image as we're looking over time. There's a really big

25
00:01:36.380 --> 00:01:40.390
flash on one side of the sun--that's a solar flare. And in this

26
00:01:40.410 --> 00:01:44.430
case it's the largest solar flare that happened during this particular

27
00:01:44.450 --> 00:01:48.470
solar activity cycle. One of the coolest things that we

28
00:01:48.490 --> 00:01:52.500
can see from this video is the simple fact that the sun

29
00:01:52.520 --> 00:01:56.540
rotates around its axis. The center near the equator

30
00:01:56.560 --> 00:02:00.570
takes about 25 days for it to rotate all the way

31
00:02:00.590 --> 00:02:04.600
around and come back to the same place. Now, I'm pointing this out because

32
00:02:04.620 --> 00:02:08.630
the sun has a special feature, something called differential rotation.

33
00:02:08.650 --> 00:02:12.650
A point on the equator actually moves faster

34
00:02:12.670 --> 00:02:16.670
than a point closer to the north or south pole.

35
00:02:16.690 --> 00:02:20.700
One thing that happens is sometimes the images move, the sun

36
00:02:20.720 --> 00:02:24.740
moves around or even rolls. But that's actually the

37
00:02:24.760 --> 00:02:28.770
spacecraft moving, not the sun. SDO has to

38
00:02:28.790 --> 00:02:32.810
occasionally roll the entire spacecraft in order to

39
00:02:32.830 --> 00:02:36.850
calibrate the cameras and instrumentation on board.

40
00:02:36.870 --> 00:02:40.880
If you notice, those bright patches, those active

41
00:02:40.900 --> 00:02:44.930
regions, start off towards the poles

42
00:02:44.950 --> 00:02:48.950
of the sun and as we move in time, they start to

43
00:02:48.970 --> 00:02:52.990
slowly creep towards the equator. This is part of what we call

44
00:02:53.010 --> 00:02:57.040
the solar activity cycle or solar cycle. As we

45
00:02:57.060 --> 00:03:01.080
move from very low activity, with very few sunspots,

46
00:03:01.100 --> 00:03:05.150
to high activity, with a lot of sunspots.

47
00:03:05.170 --> 00:03:09.190
This is something that happens again and again, and it's happened

48
00:03:09.210 --> 00:03:13.230
for millions of years. -MUSIC-

49
00:03:13.250 --> 00:03:17.310
-MUSIC-

50
00:03:17.330 --> 00:03:21.370
And now we can see the sun

51
00:03:21.390 --> 00:03:25.420
in multiple wavelengths of light simultaneously. We see

52
00:03:25.440 --> 00:03:29.470
the visible sun, where you can see the dark sunspots.

53
00:03:29.490 --> 00:03:33.540
And then if you look at the 171 extreme ultraviolet

54
00:03:33.560 --> 00:03:37.600
you see the corresponding bright areas and the magnetic

55
00:03:37.620 --> 00:03:41.710
loops coming from them. If we go to the 193

56
00:03:41.730 --> 00:03:45.790
you see even more structure and you see these dark patches.

57
00:03:45.810 --> 00:03:49.850
And this is where magnetic fields are open out into space

58
00:03:49.870 --> 00:03:53.920
letting out something called the solar wind in these very

59
00:03:53.940 --> 00:03:58.040
fast streams of particles. And then the last one, the red

60
00:03:58.060 --> 00:04:02.130
one, is 304 angstrom, and this is showing us what we

61
00:04:02.150 --> 00:04:06.230
call the chromosphere. And these red areas are often visible

62
00:04:06.250 --> 00:04:10.330
when you see the sun from total solar eclipse.

63
00:04:10.350 --> 00:04:14.480
-MUSIC-

64
00:04:14.500 --> 00:04:18.500
-MUSIC-

65
00:04:18.520 --> 00:04:22.530
Did you see that little tiny black

66
00:04:22.550 --> 00:04:26.560
dot that's close to the north pole on the sun? That's Venus.

67
00:04:26.580 --> 00:04:30.590
Every hundred years or so, it moves in front of the sun

68
00:04:30.610 --> 00:04:34.630
giving us this rare and amazing astronomical

69
00:04:34.650 --> 00:04:38.660
event. -MUSIC-

70
00:04:38.680 --> 00:04:42.670
-MUSIC-

71
00:04:42.690 --> 00:04:46.700
-MUSIC-

72
00:04:46.720 --> 00:04:50.730
-MUSIC-

73
00:04:50.750 --> 00:04:54.760
Beeping

74
00:04:54.780 --> 00:05:03.784
Beeping