WEBVTT - What Makes Stars Twinkle?

0:00:02.040 --> 0:00:06.760
<v Speaker 1>Welcome to brain stuff from how stuff works, Hey, brain

0:00:06.800 --> 0:00:10.640
<v Speaker 1>stuff luring vocal bomb here. All things considered, our atmosphere

0:00:10.720 --> 0:00:14.480
<v Speaker 1>is pretty great. This blanket of nitrogen, oxygen, and other

0:00:14.520 --> 0:00:18.320
<v Speaker 1>gases keeps the world's temperature nice and habitable while protecting

0:00:18.400 --> 0:00:21.239
<v Speaker 1>us from harmful UV radiation. To say nothing of this

0:00:21.320 --> 0:00:24.720
<v Speaker 1>space debris vaporizes for us. Oh yeah, and without all

0:00:24.760 --> 0:00:27.960
<v Speaker 1>that oxygen in our atmosphere, animal life couldn't survive on

0:00:28.040 --> 0:00:32.080
<v Speaker 1>planet Earth. Not a bad resume. But despite its many

0:00:32.080 --> 0:00:36.000
<v Speaker 1>good qualities, the atmosphere can be a nuisance to astronomy buffs.

0:00:36.360 --> 0:00:40.440
<v Speaker 1>That's because it distorts light. At night, the atmosphere makes

0:00:40.479 --> 0:00:44.000
<v Speaker 1>some heavenly bodies appeared to flicker and shimmer. The technical

0:00:44.080 --> 0:00:48.320
<v Speaker 1>term for this phenomenon is astronomical scintillation. You probably know

0:00:48.400 --> 0:00:51.680
<v Speaker 1>it by a different name, twinkling like an onion. The

0:00:51.760 --> 0:00:54.640
<v Speaker 1>atmosphere is made up of layers. At the bottom is

0:00:54.680 --> 0:00:57.720
<v Speaker 1>the troposphere, which starts right here at ground level on

0:00:57.760 --> 0:01:01.160
<v Speaker 1>the planet's surface. Standing about five to nine miles that's

0:01:01.200 --> 0:01:04.640
<v Speaker 1>eight to four point five kilometers tall, It's where most

0:01:04.680 --> 0:01:08.080
<v Speaker 1>of Earth's weather events take place. The other layers are

0:01:08.120 --> 0:01:13.920
<v Speaker 1>in ascending order, The stratosphere mesosphere, thermosphere, and exosphere. There's

0:01:13.959 --> 0:01:16.960
<v Speaker 1>also a region called the ionosphere, which encompasses parts of

0:01:17.000 --> 0:01:22.400
<v Speaker 1>both the mesosphere and the thermosphere. These layers have different temperatures.

0:01:22.720 --> 0:01:26.080
<v Speaker 1>In addition, the air's density varies from level to level.

0:01:26.520 --> 0:01:29.840
<v Speaker 1>When starlight enters our atmosphere, it runs into pockets of

0:01:29.959 --> 0:01:33.600
<v Speaker 1>cool and warm air. The pockets act as big lenses,

0:01:33.760 --> 0:01:36.920
<v Speaker 1>causing the light to change direction or refract as it

0:01:36.959 --> 0:01:40.440
<v Speaker 1>passes through them. Yet the lenses are not fixed in place.

0:01:40.520 --> 0:01:44.319
<v Speaker 1>They move around and change shape as they shift. So

0:01:44.400 --> 0:01:48.160
<v Speaker 1>does starlight refraction. That's why the stars appear to twinkle.

0:01:49.040 --> 0:01:53.400
<v Speaker 1>Scintillation affects planets to Mercury, Venus, Mars, and the other

0:01:53.480 --> 0:01:56.440
<v Speaker 1>planets in our Solar system do twinkle when viewed from

0:01:56.440 --> 0:01:59.720
<v Speaker 1>Earth on a clear night. So does our moon. However,

0:01:59.800 --> 0:02:04.040
<v Speaker 1>the planets twinkled to a barely noticeable degree distance is

0:02:04.080 --> 0:02:07.840
<v Speaker 1>the main reason stars twinkle more conspicuously than the planets

0:02:07.840 --> 0:02:11.320
<v Speaker 1>in our Solar system, because the former are so far away,

0:02:11.639 --> 0:02:14.720
<v Speaker 1>each star looks like a single pinpoint of light, a

0:02:14.800 --> 0:02:17.800
<v Speaker 1>single pixel. You might say. It's a different story for

0:02:17.840 --> 0:02:21.560
<v Speaker 1>Earth's moon and our neighboring planets, being a lot closer

0:02:21.600 --> 0:02:25.360
<v Speaker 1>they're less affected by the atmosphere. Planets and moons appear

0:02:25.400 --> 0:02:27.880
<v Speaker 1>as tiny disks up in the sky. The light they

0:02:27.919 --> 0:02:30.320
<v Speaker 1>emanate comes not from a single point, but from many

0:02:30.360 --> 0:02:35.240
<v Speaker 1>individual points, all clustered together. These rarely scintillate in unison,

0:02:35.320 --> 0:02:38.320
<v Speaker 1>which is why planets and moons don't twinkle as dramatically

0:02:38.360 --> 0:02:42.080
<v Speaker 1>as the stars, So twinkling can only happen when an

0:02:42.120 --> 0:02:45.360
<v Speaker 1>atmosphere is present. It's for this reason that photos taken

0:02:45.360 --> 0:02:48.119
<v Speaker 1>by the Hubble telescope looks so clear. There aren't any

0:02:48.160 --> 0:02:52.239
<v Speaker 1>atmospheric air pockets to refract the starlight. Earth Bound astronomers

0:02:52.320 --> 0:02:55.919
<v Speaker 1>use telescopes with adaptive optics systems to compensate for twinkling,

0:02:56.160 --> 0:03:04.280
<v Speaker 1>making the stars look more stable. Today's episode was written

0:03:04.280 --> 0:03:07.440
<v Speaker 1>by Mark Mancini and produced by Tyler Clang. Brain Stuff

0:03:07.440 --> 0:03:09.840
<v Speaker 1>has merch now. You can get phone cases, tote bags,

0:03:09.960 --> 0:03:12.679
<v Speaker 1>and of course T shirts. Every purchase helps keep the

0:03:12.680 --> 0:03:15.280
<v Speaker 1>show going and supports us directly. You can find all

0:03:15.280 --> 0:03:18.600
<v Speaker 1>that stuff at t public dot com slash brain Stuff.

0:03:18.680 --> 0:03:20.800
<v Speaker 1>For more on this and lots of other bright topics,

0:03:20.919 --> 0:03:34.640
<v Speaker 1>visit our home planet how Stuff works dot com.