1
00:00:00,060 --> 00:00:04,110
[Music throughout] Announcer: Liftoff of the Delta rocket carrying a gamma-ray

2
00:00:04,130 --> 00:00:08,290
telescope searching for unseen...[Fades out] Narrator: I'm Julie Mcenery, Fermi

3
00:00:08,310 --> 00:00:12,400
Project Scientist. Since its launch in 2008, 

4
00:00:12,420 --> 00:00:16,540
the Fermi Gamma-ray Space Telescope has revolutionized our understanding of

5
00:00:16,560 --> 00:00:20,730
powerful events and objects in the cosmos. Fermi observes the universe using

6
00:00:20,750 --> 00:00:24,890
gamma rays, the highest-energy form of light, more energetic than even X-rays.

7
00:00:24,910 --> 00:00:28,980
Gamma rays are emitted by objects with extreme gravity and magnetic fields.

8
00:00:29,000 --> 00:00:33,150
Many of the gamma rays Fermi sees are produced by black holes,

9
00:00:33,170 --> 00:00:37,350
and incredibly dense, rapidly spinning stars called pulsars.

10
00:00:37,370 --> 00:00:41,400
Fermi's predecessor, the Compton Gamma Ray Observatory, collected data

11
00:00:41,420 --> 00:00:45,510
from 1991 to 2000, which was used to create this all-sky map.

12
00:00:45,530 --> 00:00:49,650
Over the past decade, Fermi has

13
00:00:49,670 --> 00:00:53,850
refined our view and fundamentally changed our understanding of the cosmos.

14
00:00:53,870 --> 00:00:57,980
In celebration of its 10th anniversary, here are just a few

15
00:00:58,000 --> 00:01:02,160
of its transformative discoveries. In its very first

16
00:01:02,180 --> 00:01:06,370
year of observations, Fermi spotted a short, powerful gamma-ray burst

17
00:01:06,390 --> 00:01:10,430
called GRB 090510. This burst

18
00:01:10,450 --> 00:01:14,580
provided proof that space-time works the way Einstein predicted.

19
00:01:14,600 --> 00:01:18,690
Gamma-ray bursts are the most luminous events Fermi sees.

20
00:01:18,710 --> 00:01:22,830
Scientists think they are caused when stars collapse, or when neutron stars or black holes

21
00:01:22,850 --> 00:01:26,980
merge. These events drive jets of particles at nearly the speed of light.

22
00:01:27,000 --> 00:01:31,160
The material in the jets collides, generating shock waves that produce the 

23
00:01:31,180 --> 00:01:35,290
gamma rays that we see. In the last decade, Fermi has detected over

24
00:01:35,310 --> 00:01:39,360
2,300 bursts. Fermi detected two gamma rays

25
00:01:39,380 --> 00:01:43,440
with different energies from GRB 090510. Although

26
00:01:43,460 --> 00:01:47,550
they traveled over 7 billion light-years, both reached Fermi at nearly the same

27
00:01:47,570 --> 00:01:51,650
instant. This supports Einstein's theory that all light

28
00:01:51,670 --> 00:01:55,750
no matter its energy, moves at the same speed because space-time is smooth.

29
00:01:55,770 --> 00:01:59,890
In 2017, Fermi spotted a gamma-ray burst

30
00:01:59,910 --> 00:02:04,080
coming from the constellation Hydra, which coincided with the detection 

31
00:02:04,100 --> 00:02:08,190
of ripples in space-time. The burst came from the merger of

32
00:02:08,210 --> 00:02:12,330
two superdense neutron stars. Ground-based observatories

33
00:02:12,350 --> 00:02:16,530
detected gravitational waves at nearly the same instant Fermi detected gamma rays.

34
00:02:16,550 --> 00:02:20,590
This was the first time light and gravitational waves were detected 

35
00:02:20,610 --> 00:02:24,660
from the same source. Early in Fermi's mission,

36
00:02:24,680 --> 00:02:28,800
scientists noticed odd structures emerging from above and below the 

37
00:02:28,820 --> 00:02:32,980
Milky Way. These Fermi "bubbles" have become more prominent with each passing year

38
00:02:33,000 --> 00:02:37,060
of data. The bubbles extend 25,000 light-years

39
00:02:37,080 --> 00:02:41,150
above and below the galactic plane. They were probably produced only

40
00:02:41,170 --> 00:02:45,260
a few million years ago by the supermassive black hole at the center of the Milky Way.

41
00:02:45,280 --> 00:02:49,440
This means our galaxy was extremely active a very

42
00:02:49,460 --> 00:02:53,510
short time ago, in astronomical terms.

43
00:02:53,530 --> 00:02:57,650
Over the last 10 years, Fermi has also placed new limits on

44
00:02:57,670 --> 00:03:01,840
theories about dark matter by looking at tiny, faint galaxies called dwarf spheroidals.

45
00:03:01,860 --> 00:03:06,040
Almost 85 percent of the universe's matter is dark matter,

46
00:03:06,060 --> 00:03:10,100
but scientists don't know exactly what dark matter is.

47
00:03:10,120 --> 00:03:14,140
One theory is that it's made of Weakly Interacting Massive Particles,

48
00:03:14,160 --> 00:03:18,180
or WIMPs. WIMPs don't produce light, or interact with

49
00:03:18,200 --> 00:03:22,300
other particles. When two WIMPs meet, though, scientists think

50
00:03:22,320 --> 00:03:26,390
they annihilate and produce gamma rays with unique signatures.

51
00:03:26,410 --> 00:03:30,490
Dwarf spheroidals have high concentrations of dark matter.

52
00:03:30,510 --> 00:03:34,580
Fermi has observed several of these galaxies, but seen no sign of

53
00:03:34,600 --> 00:03:38,630
WIMP-produced gamma rays. This sets strong limits on the properties

54
00:03:38,650 --> 00:03:42,800
of dark matter. The universe is a sea of

55
00:03:42,820 --> 00:03:46,810
charged particles called cosmic rays, moving at nearly the speed of light.

56
00:03:46,830 --> 00:03:50,880
Fermi observations of two supernova remnants shed new light on their origins.

57
00:03:50,900 --> 00:03:54,950
Thousands of cosmic rays hit every square meter of Earth's atmosphere

58
00:03:54,970 --> 00:03:59,090
every second. And Fermi's Large Area Telescope

59
00:03:59,110 --> 00:04:03,220
detects only one gamma ray for every thousand cosmic rays. Despite their

60
00:04:03,240 --> 00:04:07,310
abundance, the origins of cosmic rays were a longstanding mystery.

61
00:04:07,330 --> 00:04:11,460
In 1949, Enrico Fermi, the satellite's

62
00:04:11,480 --> 00:04:15,510
namesake, proposed that they might be generated in the shock waves of supernovas.

63
00:04:15,530 --> 00:04:19,620
But cosmic ray paths are hard to trace. They veer off course each time

64
00:04:19,640 --> 00:04:23,730
they encounter a magnetic field. In 2013,

65
00:04:23,750 --> 00:04:27,840
Fermi observed gamma rays coming from two supernova remnants.

66
00:04:27,860 --> 00:04:32,000
The gamma rays' properties told scientists they were created by cosmic rays propelled by

67
00:04:32,020 --> 00:04:36,080
supernova shock waves, just as Enrico Fermi predicted.

68
00:04:36,100 --> 00:04:40,260
While the atmosphere is pelted by cosmic rays from above, thunderstorms

69
00:04:40,280 --> 00:04:44,310
generate gamma rays from below. Fermi observes these

70
00:04:44,330 --> 00:04:48,370
terrestrial gamma-ray flashes, or TGFs, using its Gamma-ray Burst Monitor.

71
00:04:48,390 --> 00:04:52,520
Under the right conditions, a lightning flash triggers a flood

72
00:04:52,540 --> 00:04:56,550
of electrons that rush to the top of the cloud at nearly the speed of light.

73
00:04:56,570 --> 00:05:00,660
These electrons produce gamma rays when they run into air molecules.

74
00:05:00,680 --> 00:05:04,810
Fermi has spotted 5,000 TGFs over

75
00:05:04,830 --> 00:05:08,940
10 years, but scientists estimate more than a thousand of them occur every day.

76
00:05:08,960 --> 00:05:13,040
From Earth's atmosphere, to the farthest reaches

77
00:05:13,060 --> 00:05:17,150
of the cosmos, Fermi's first ten years have fundamentally altered how

78
00:05:17,170 --> 00:05:21,230
we look at the universe. The gamma-ray sky changes every day,

79
00:05:21,250 --> 00:05:25,430
who knows what new, exciting await us

80
00:05:25,450 --> 00:05:29,490
in the future?

81
00:05:29,510 --> 00:05:33,670
[Music]

82
00:05:33,690 --> 00:05:37,840
[Beeping]

83
00:05:37,860 --> 00:05:45,525
[Beeping]