WEBVTT 00:02.035 --> 00:03.837 position:10% line:85% size:80% Joan Cartan-Hansen, Host: We live on Earth. 00:03.837 --> 00:05.672 position:10% line:85% size:80% It's one of the planets in our solar system. 00:05.672 --> 00:06.806 position:10% line:85% size:80% But it's not the only planet. 00:06.806 --> 00:09.275 position:10% line:85% size:80% Take a tour of our solar neighborhood. 00:09.776 --> 00:14.848 position:10% line:85% size:80% (MUSIC) 00:14.848 --> 00:17.250 position:10% line:85% size:80% Solar means connected to the sun. 00:17.250 --> 00:19.886 position:10% line:85% size:80% And the sun is the center of our neighborhood, our solar 00:19.886 --> 00:20.887 position:10% line:85% size:80% system. 00:20.887 --> 00:22.222 position:10% line:85% size:80% The sun is a star. 00:22.222 --> 00:25.658 position:10% line:85% size:80% And stars are basically big balls of super-hot plasma. 00:25.658 --> 00:29.062 position:10% line:85% size:80% The center of the sun or its core is like an enormous atom 00:29.062 --> 00:31.798 position:10% line:85% size:80% smasher, which constantly releases energy by crushing 00:31.798 --> 00:33.466 position:10% line:85% size:80% atoms together. 00:33.466 --> 00:36.102 position:10% line:85% size:80% Heat and light spread out from the sun, warming the rest of 00:36.102 --> 00:38.104 position:10% line:85% size:80% the solar system. 00:38.104 --> 00:40.273 position:10% line:85% size:80% There are eight planets in our solar system. 00:40.273 --> 00:42.675 position:10% line:85% size:80% They each revolve around the sun in what's called an orbit. 00:42.675 --> 00:46.312 position:10% line:85% size:80% An orbit is the path a planet takes around the sun. 00:46.312 --> 00:48.782 position:10% line:85% size:80% And everything is held in place by a force called 00:48.782 --> 00:50.283 position:10% line:85% size:80% gravity. 00:50.283 --> 00:52.952 position:10% line:85% size:80% The planet nearest to the sun is Mercury. 00:52.952 --> 00:54.788 position:10% line:85% size:80% Now nearest doesn't mean close. 00:54.788 --> 00:58.425 position:10% line:85% size:80% Mercury is still about 36 million miles from the sun. 00:58.425 --> 01:01.394 position:10% line:85% size:80% Mercury is not much bigger than our moon and its surface 01:01.394 --> 01:04.731 position:10% line:85% size:80% is really hot, seven times hotter than the hottest desert 01:04.731 --> 01:05.932 position:10% line:85% size:80% on earth. 01:05.932 --> 01:08.201 position:10% line:85% size:80% But during the night, temperatures there are twice 01:08.201 --> 01:10.703 position:10% line:85% size:80% as cold as in Antarctica. 01:10.703 --> 01:12.439 position:10% line:85% size:80% The next planet is Venus. 01:12.439 --> 01:15.275 position:10% line:85% size:80% It's about 67 million miles from the sun. 01:15.275 --> 01:17.710 position:10% line:85% size:80% Venus is about the same size as the Earth. 01:17.710 --> 01:20.613 position:10% line:85% size:80% But its atmosphere, or the blanket of gases that surround 01:20.613 --> 01:23.116 position:10% line:85% size:80% it is made up of poisonous gases. 01:23.116 --> 01:25.819 position:10% line:85% size:80% It's covered with clouds and reflects a lot of light. 01:25.819 --> 01:28.588 position:10% line:85% size:80% That's why Venus is the easiest planet to see in the 01:28.588 --> 01:30.190 position:10% line:85% size:80% night sky. 01:30.190 --> 01:33.126 position:10% line:85% size:80% The Earth is the third planet from the Sun. 01:33.126 --> 01:36.463 position:10% line:85% size:80% It's just the right distance from the Sun, about 93 million 01:36.463 --> 01:40.433 position:10% line:85% size:80% miles, to be warm enough and cool enough for life. 01:40.433 --> 01:44.337 position:10% line:85% size:80% And it has enough gravity to hold onto its atmosphere. 01:44.337 --> 01:45.638 position:10% line:85% size:80% The Earth has one moon. 01:45.638 --> 01:48.374 position:10% line:85% size:80% Moons are smaller objects that orbit a planet the way a 01:48.374 --> 01:49.909 position:10% line:85% size:80% planet orbits the Sun. 01:49.909 --> 01:52.278 position:10% line:85% size:80% They're called natural satellites and many planets 01:52.278 --> 01:53.746 position:10% line:85% size:80% have moons of their own. 01:53.746 --> 01:57.116 position:10% line:85% size:80% Heading out, the next planet in the solar system is Mars. 01:57.116 --> 02:00.186 position:10% line:85% size:80% Mars is about half the size of the earth and is about 141 02:00.186 --> 02:02.021 position:10% line:85% size:80% million miles from the sun. 02:02.021 --> 02:04.891 position:10% line:85% size:80% It has a thin atmosphere and is known as the red planet 02:04.891 --> 02:07.160 position:10% line:85% size:80% because of its red soil. 02:07.160 --> 02:10.263 position:10% line:85% size:80% Mars once had water flowing across its surface. 02:10.263 --> 02:12.999 position:10% line:85% size:80% Several rovers and space probes are studying Mars to 02:12.999 --> 02:15.134 position:10% line:85% size:80% see if humans could travel there. 02:15.134 --> 02:18.438 position:10% line:85% size:80% These four planets, Mercury, Venus, Earth and Mars are 02:18.438 --> 02:20.039 position:10% line:85% size:80% known as the inner planets. 02:20.039 --> 02:23.576 position:10% line:85% size:80% Next comes a big gap called the asteroid belt. 02:23.576 --> 02:26.579 position:10% line:85% size:80% Here, asteroids or chunks of rock, some as small as 02:26.579 --> 02:30.016 position:10% line:85% size:80% pebbles, and some as big as mountains orbit the Sun. 02:30.016 --> 02:33.353 position:10% line:85% size:80% There is one dwarf planet in the asteroid belt, Ceres. 02:33.353 --> 02:36.556 position:10% line:85% size:80% After this gap come the four outer planets. 02:36.556 --> 02:40.093 position:10% line:85% size:80% Jupiter is about 483 million miles from the Sun. 02:40.093 --> 02:43.363 position:10% line:85% size:80% Its huge, the largest planet in the solar system. 02:43.363 --> 02:47.000 position:10% line:85% size:80% 1300 Earths could fit inside this planet. 02:47.000 --> 02:50.270 position:10% line:85% size:80% And it's mostly a big ball of gas surrounding a rocky core. 02:50.270 --> 02:53.239 position:10% line:85% size:80% It has more than 50 moons and scientists are still finding 02:53.239 --> 02:54.874 position:10% line:85% size:80% more. 02:54.874 --> 02:56.376 position:10% line:85% size:80% Next comes Saturn. 02:56.376 --> 02:59.746 position:10% line:85% size:80% It's 887 million miles from the Sun and it's known for its 02:59.746 --> 03:00.780 position:10% line:85% size:80% rings. 03:00.780 --> 03:03.883 position:10% line:85% size:80% The rings are made up of dust, rocks and chunks of ice. 03:03.883 --> 03:05.752 position:10% line:85% size:80% It has more than 80 moons. 03:05.752 --> 03:09.122 position:10% line:85% size:80% Saturn is mostly gas and has no surface to walk on. 03:09.122 --> 03:13.159 position:10% line:85% size:80% The seventh planet is Uranus about one point eight billion 03:13.159 --> 03:14.394 position:10% line:85% size:80% miles from the Sun. 03:14.394 --> 03:17.297 position:10% line:85% size:80% Unlike the other planets, it rotates on its side. 03:17.297 --> 03:19.766 position:10% line:85% size:80% Scientists think that's because a huge collision with 03:19.766 --> 03:23.069 position:10% line:85% size:80% another planet long ago tipped it over. 03:23.069 --> 03:25.471 position:10% line:85% size:80% It has a core of rock and ice about the size of Earth but 03:25.471 --> 03:27.974 position:10% line:85% size:80% the rest of the planet is made of gas. 03:27.974 --> 03:31.945 position:10% line:85% size:80% And it too has narrow rings and more than 20 moons. 03:31.945 --> 03:34.247 position:10% line:85% size:80% Neptune is the eighth planet from the Sun. 03:34.247 --> 03:37.383 position:10% line:85% size:80% Neptune is more than 2.8 billion miles from the Sun. 03:37.383 --> 03:41.387 position:10% line:85% size:80% It's so far away that sunlight is 900 times dimmer than the 03:41.387 --> 03:43.289 position:10% line:85% size:80% light that reaches the Earth. 03:43.289 --> 03:46.259 position:10% line:85% size:80% It's also the windiest planet in the solar system with wind 03:46.259 --> 03:49.562 position:10% line:85% size:80% speeds four times greater than the Earth's. 03:49.562 --> 03:51.497 position:10% line:85% size:80% Next comes the Kuiper Belt. 03:51.497 --> 03:54.434 position:10% line:85% size:80% The Kuiper Belt is a donut shaped region filled with 03:54.434 --> 03:57.370 position:10% line:85% size:80% objects made up of rock, metals and frozen ices of 03:57.370 --> 03:59.138 position:10% line:85% size:80% methane, ammonia and water. 03:59.138 --> 04:02.408 position:10% line:85% size:80% It's 20 times larger than the asteroid belt. 04:02.408 --> 04:05.178 position:10% line:85% size:80% Here you'll find four of the five known dwarf planets, 04:05.178 --> 04:07.614 position:10% line:85% size:80% including the most famous, Pluto. 04:07.614 --> 04:10.283 position:10% line:85% size:80% Pluto was once classified as a planet, but astronomers 04:10.283 --> 04:12.385 position:10% line:85% size:80% changed that in 2006. 04:12.385 --> 04:15.388 position:10% line:85% size:80% Pluto is about 3 point 6 billion miles from the Sun. 04:15.388 --> 04:16.522 position:10% line:85% size:80% It's small. 04:16.522 --> 04:19.292 position:10% line:85% size:80% Pluto's width is about half that of the United States. 04:19.292 --> 04:21.494 position:10% line:85% size:80% But it does have a heart-shaped glacier bigger 04:21.494 --> 04:22.795 position:10% line:85% size:80% than Texas. 04:22.795 --> 04:25.264 position:10% line:85% size:80% After the Kuiper Belt, is the Oort Cloud. 04:25.264 --> 04:27.900 position:10% line:85% size:80% The Oort Cloud is the most distant region of our solar 04:27.900 --> 04:28.935 position:10% line:85% size:80% system. 04:28.935 --> 04:31.404 position:10% line:85% size:80% It's shaped like a huge bubble and it's filled with icy 04:31.404 --> 04:33.206 position:10% line:85% size:80% pieces of space debris. 04:33.206 --> 04:35.608 position:10% line:85% size:80% Scientists think the Oort Cloud may contain billions, 04:35.608 --> 04:37.210 position:10% line:85% size:80% even trillions, of objects. 04:37.210 --> 04:39.946 position:10% line:85% size:80% It's where they think comets come from. 04:39.946 --> 04:42.181 position:10% line:85% size:80% So, what's beyond our solar system? 04:42.181 --> 04:44.384 position:10% line:85% size:80% More stars and more planets. 04:44.384 --> 04:47.353 position:10% line:85% size:80% Our solar system is part of a galaxy which contains billions 04:47.353 --> 04:48.588 position:10% line:85% size:80% of stars. 04:48.588 --> 04:51.491 position:10% line:85% size:80% Our galaxy is called the Milky Way. 04:51.491 --> 04:53.993 position:10% line:85% size:80% Astronomers have identified more than 3000 other solar 04:53.993 --> 04:56.963 position:10% line:85% size:80% systems in our galaxy and think there could be as many 04:56.963 --> 04:58.464 position:10% line:85% size:80% as 100 billion more. 04:58.464 --> 05:01.267 position:10% line:85% size:80% Many of these solar systems look like ours, but many 05:01.267 --> 05:02.669 position:10% line:85% size:80% others look very different. 05:02.669 --> 05:05.204 position:10% line:85% size:80% As scientist learn more about the universe, they're finding 05:05.204 --> 05:08.408 position:10% line:85% size:80% out just how special our solar system is. 05:09.075 --> 05:11.511 position:10% line:85% size:80% If you want to learn more about the planets, check out 05:11.511 --> 05:12.412 position:10% line:85% size:80% the science trek website. 05:12.412 --> 05:14.580 position:10% line:85% size:80% You'll find it at science trek dot org. 05:15.848 --> 05:34.567 position:10% line:85% size:80% (MUSIC) 05:34.567 --> 05:37.336 position:10% line:85% size:80% Announcer: Presentation of Science Trek on Idaho Public 05:37.336 --> 05:40.640 position:10% line:85% size:80% Television is made possible through the generous support 05:40.640 --> 05:43.476 position:10% line:85% size:80% of the Laura Moore Cunningham Foundation, committed to 05:43.476 --> 05:46.379 position:10% line:85% size:80% fulfilling the Moore and Bettis family legacy of 05:46.379 --> 05:48.948 position:10% line:85% size:80% building the great state of Idaho. 05:48.948 --> 05:52.351 position:10% line:85% size:80% By the Idaho National Laboratory, mentoring talent 05:52.351 --> 05:55.488 position:10% line:85% size:80% and finding solutions for energy and security 05:55.488 --> 05:59.225 position:10% line:85% size:80% challenges, by the Friends of Idaho Public Television and 05:59.225 --> 06:01.961 position:10% line:85% size:80% the Corporation for Public Broadcasting.