Today is a really big day here at the for because we finally finished building our brand-new observatory. Now we can learn even more cool stuff about space. Let's fire up the new telescope, Squeaks.

*Squeaks squeaks*

Ah, you're right, Squeaks. It does look a little bit blurry. While Squeaks and I fix the focus on our telescope, check out this episode for a refresher on what stars are and why they shine. 

If you're like us here at the fort, you probably enjoy stargazing. The night sky is full of cool things to look at and I bet a lot of you have been looking up there and wondering about the same things that we do. We've gotten some really interesting questions from kids like you about what you see up there.

Eight-year-old Alice from New Zealand has been doing some sky-watching and she recently emailed to ask us, "What are stars and how do they work?" Let me just say that's a stellar question. If you look up at the night sky all the stars that you see might look pretty similar, but don't let your eyes fool you. All of those stars have some important things in common, but they're also all different. They can be different colors like white, yellow, red, and blue. They can also be different sizes from about the size of a planet to something many, many times bigger than the Sun.

But before we meet some of the extreme stars, let's figure something out first: what exactly is a star? Stars are just really huge balls of hot gas in space, and deep in their centers, all stars are constantly generating an enormous amount of energy. This energy eventually travels out from the center of the star where it's given off as heat and light. That's what gives stars their glow. So keeping in mind that all stars are balls of gas that come in all kinds of sizes and colors, wanna meet some for yourself? 

Let's start with the most important star, at least for us here on Earth, the Sun. That's right the Sun is a star, and it's a specific kind of star called a yellow dwarf. While we think of our Sun as being super huge and incredibly hot, which it definitely is, compared 

to Earth, it's actually pretty average compared to other stars, meaning it's right in the middle between the biggest and the smallest and the hottest and the coolest stars. So, there are some stars that are much bigger than the sun, and way hotter. If you want to find one, just look for the constellation known as Orion. It's one of the easiest constellations to spot. If you look down to the right, to the star where Orion's knee is supposed to be, you'll find Rigel. Rigel is a good example of a kind of star called a blue super giant. As you can guess from its name, it's blue instead of yellow, and it's enormous. Rigel is more than twice as hot as the sun and is also more than 70 times bigger.

If you could put the sun next to Rigel, our big old sun would look like a tiny speck. And, in addition to all of the huge, hot stars in the sky, there are plenty of smaller, cooler ones, too. The smallest and coolest stars in space tend to glow with a dim, red color. And the sun is more than twice as hot as most of them. A good example of this kind of star is right next door, at least in terms of space.

Promixa Centauri is the nearest star to our sun and is a kind called a red dwarf. It'd in the constellation Centaurus in the southern sky, but even thought it's closer to the sun than any other star, it's so small that you can't even see it from earth without a telescope. How small is it? Well, you could fit 7 Promixma Centauris inside the sun, from end to end. So while you're stargazing on th next clear night, keep in mind that the stars might look pretty much the same, but now you know they come in different colors and sizes, a lot like we do. 

Okay, we're ready to go now. What should we look at first, Squeaks?

*squeak, squeak*

Mars, huh? You got it!

Whoa, check it out! There are 8 planets in the solar system. Some of them, like mars, are what we call rocky planets. Check out this episode to learn more. 

Hi guys! Welcome back to the fort. Today, Squeaks and I thought we'd do a little sight seeing using our telescope. We're gonna tour our solar system. the solar system is made up of the sun, the earth, and 7 other planets.

Plus lots of dust, big rocks, gas and other stuff. All of that stuff over and over it's so huge that only 1 spacecraft so far has ever flown from the earth all the way to the edge of the solar system is called what about the size of a small car the plane that went into over 35 years it's so big that they were just going to cover half of it I'm keeping my little boys all that time even the sun is there right at the centre of the action the sun is a star like a monster is it a huge Ball Super orgasm gives off light and heat without the sun or earth would be a dark frozen world with no life but isn't the closest planet to the sun Mercury the smallest of the size of the Earth Mercury biggest changes in temperature of any of the Planets you can go from a superchillin 7 degrees below zero 25 degrees Celsius during the day even more extreme and Venus brightest planet in our solar system Manchester sunset at night or just before when it Rises in the morning we sent probes to Venus take pictures to they show us that the planet is Rocky and covered with thick cloud but doesn't have any is extremely hot even though it's not the closest to the sun temperatures reading is high for 160 degrees Celsius the next planet 93 million

miles from the Sun and it takes 365 days, our year, for the Earth to orbit the Sun and Earth is unlike any other planet in our solar system for at least two reasons.  Number one, it's the only planet that we know for sure has liquid water on its surface and number two, it's the only planet that we know has life.  No other planets in the solar system have plants or animals or any living things on them.  Earth, you rock.

Now let's move on to our last stop for today.  It's time for a mission to Mars.  Mars' nickname is the Red Planet.  That's because Mars has a lot of minerals on its surface that give it a unique reddish color.  Mars is sorta similar to the planet that we live on.  The length of a day on Mars is almost the same as a day on Earth.  It's just about 40 minutes longer and Mars even has some ice on it, frozen at its north pole, but as far as we know, there's no liquid water anywhere on Mars because it's so cold.  Mars also has mountains and canyons like Earth.  In fact, it's home to the solar system's biggest volcano.  Scientists have named it Olympus Mons and it's nearly three times larger than Mt. Everest, the tallest mountain on Earth. 

Clearly the solar system is an amazing place full of different worlds with all kinds of extreme environments, and we've only covered four planets so far, and those four planets all have one thing in common: they're all solid worlds with hard rocky surfaces that, if you ever went there, you could stand on.  Mercury, Venus, Earth, and Mars are what we call rocky planets.  Okay, Squeaks, it's my turn.  I wanna check out Jupiter. 

Jupiter is the largest planet in the solar system.  It's what we call a gas giant.  While rocky planets are made up of, well, rock, gas giants are mostly made of lots of gas swirling around.  

Welcome back.   If you were with us last time, then you got to join Squeaks and me on the first half of our tour of our amazing solar system.  The solar system is the Sun and all the things that orbit around it.  The biggest of these are our eight planets.  Last time, we started with the star at the middle of our solar system, the Sun, and we stopped by for visits to Mercury, the smallest planet, followed by Venus, which is the hottest planet, then our home, Earth, the only planet that we know that has living things on it, and finally, Mars.  

Those four planets are the only rocky planets in our solar system.  That means that they have hard rocky surfaces and if you could fly there, you could actually stand on them, but way out beyond Mars, you'll find a totally different kind of planet, ones that are made almost completely out of gas.  Scientists call these the 'gas giants' and the first one we'll bump into is also by far the biggest planet in our solar system: Jupiter.  This planet is made up entirely of thick layers of gas, and it's so big that Earth could fit into it more than 1,300 times over.   It even has more than 60 moons of its own.  Jupiter is also a very stormy planet with wild winds whipping all over, all the time.  One storm, called the great red spot, has been raging on Jupiter for hundreds of years.  The storm sometimes gets smaller or bigger but it has been there for as long as people have been studying Jupiter with telescopes.  See you later, storm.

Our next planet, Saturn, is also really, really big and made of gas, but you can tell it apart from Jupiter and other gas giants because of its big beautiful rings.  Actually, all four of the gas giants have rings around them, but most of them are so small and faint that it's hard to see them, but Saturn has the biggest and the brightest rings and they might look fancy, but they're really just made of dust, rocks, and ice, and even though Saturn is really big, it's also very light.  Some scientists think that because the gases that make it up are so lightweight, the whole planet would actually be able to float in water.  If only we could find a bathtub big enough.

Saturn is the furthest planet from the Earth that you can actually see with your own eyes.  You'll need a telescope to spot our next gas giant: Uranus.  Unlike all the other planets in our solar system, Uranus spins on its side.  Nobody's exactly sure why, but it could be that a large object smashed into the planet a long time ago and knocked it sideways.  Besides moving differently, Uranus is also a lot colder than the other planets and is sometimes called an ice giant. It has reached the coldest temperature ever measured in our solar system, dipping almost as low as 223 degrees below zero.  

Oh, brr! But it's not getting much warmer where we're headed. Come on squeaks, let's find our last gas giant: Neptune. Neptune is the furthest planet from the sun. It could take up to 12 years to fly to Neptune from Earth. And neptune takes a really long time to orbit the sun. Over 160 earth years to go around a singe time. But it has at least one thing in common with its big brother, Juptiter: it aso has giant storms swirling on it. Scientists caed one of these storms the Great Dark Spot, because it looks like a big blotch of dark bue. And this storm was fierce. Scientists think that the winds inside the storm were the strongest, fastest winds anywhere in our solar system. But this storm didn't ast as long as the one on Jupiter.  The last time astronomers pointed their telescopes at the great dark spot to take a picture of it, it had dissapeared. But a new storm has formed on another part of the planet. Whoo! That was an awesome trip. Now we've seen all of the panets in our solar system. But what else is out there? Plenty! 

Those rocky planets and gas giants are just a few of the things in our massive solar system.  It also has asteroids and comets and other small worlds made of dust and ice and almost certainly tons of other things scientists haven't even discovered yet.  So far, we've been looking at things in the solar system but there's way more stuff out there to see.  Our sun is just one of billions of stars all clustered together in what we call the Milky Way galaxy and there are even more galaxies beyond that and even more beyond that.  

You and I have talked a lot about space, haven't we?  We've learned about stars, we found out all about comets and asteroids, and we can even name all eight of the planets in our solar system, but have you ever thought about what's beyond our solar system?  The sun is just a star after all, and it, along with us and all the other planets, aren't just floating around in space all by ourselves.  Oh no.  Our solar system is part of something much, much bigger: a galaxy.  

A galaxy is a huge bunch of stars that are clustered together in space, and the galaxy that our solar system is part of is called the Milky Way.  

The Milky Way is full of stars.  How many?  Well, do you know how much a thousand is?  A thousand looks like this, and if you take a thousand and multiply it by a thousand and multiply it by a thousand again, that number is a billion, and there are billions of stars just in the Milky Way alone.  In fact, there are so many stars in the Milky Way that we still don't know exactly how many there are, but scientists think that many of the other stars in our galaxy probably have planets of their own, and the Milky Way isn't the only galaxy.

Astronomers who study deep distant space have found other galaxies, too.  More than you could count!  To organize and study all of these galaxies, astronomers usually group them into three main types, depending on thier shape.  There are spiral galaxies, elliptical galaxies, and irregular galaxies.  Spiral galaxies are in the shape of a pinwheel.  They have that shape because stars in a spiral galaxy are clumped into lines that curl outward.  These lines are called spiral arms, and the galaxy that you and I are in right now, the Milky Way galaxy, is a spiral galaxy.

Now, some spiral galaxies are just flat like a pancake, but other spirals, including our own Milky Way, have a large bulge in the midlde that's made up of a big bunch of stars.  The stars in the bulge are usually older stars, while younger stars are often found on the outer spiral arms of the galaxy.  Astronomers even know where our star, the sun, is in the Milky Way.  If you were way, way out in space, floating above our galaxy and looked down at it, you'd find the Sun right about here, near the middle of one of the spiral arms. 

Now, another common kind of galaxy is called an elliptical galaxy.  Elliptical galaxies are shaped like an ellipse, or an egg shape and instead of being flat with a bulge in the middle, these galaxies are all bulge.  They tend to have mostly older stars in them and stars in an elliptical galaxy are really close together, which makes the middle of the galaxy look like one giant bright star.  

The last common type of galaxy is an irregular galaxy.  Irreguar means not regular, and these kinds of galaxies don't have a definite regular shape.  Instead, these clusters of stars can take all kinds of different shapes, like this or this or even this.  There are tons of other galaxies out there to learn about and scientists are discovering new ones all the time.  So the next time you're out at night, gazing at the sky, remember that you and the Earth and the whole solar system are part of something bigger: a galaxy.

Whoa.  The universe is a big place, and people are just getting started exploring it.  That's right, Squeaks, there are astronauts orbiting the Earth right now, doing experiments and studying what happens when you live in Space.

My jobs is pretty great.  I get to learn about amazing animals and places and do fun experiments with all of you and you know another job that seems really great?  You might even say it's out of this world?  Being an astronaut!  Astronauts are people who travel and work in space.  Going to space seems like a big adventure and it is, but that's not why astronauts go to space, at least, it's not the main reason.

Astronauts go to space so they can learn more about what's beyond our planet.  They spend weeks, months, or even a whole year away from their friends and family to study space in person.  Then, they come back home and share their new knowledge with all of us.  Do you want to go to space?  If you do, maybe you wanna know exactly what it takes to be an astronaut, and what they do up there all day before you sign up.  Let's find out what it takes to be an astronaut.  

The fact is, practically anybody can become an astronaut.  You don't even have to be a certain age.  You just have to have a few main things under your belt.  For one thing, you have to have studied science in college, which means you pretty much have to be a grown up or a young adult.  

You also have to have spent some time, specifically three years, actually doing the science that you've studied.  That's because most astronauts are actually scientists, and there are all kinds of scientists who work in space, some of which we've talked about before, like biologists or astronomers or chemists.  Finally, to be an astronaut, you have to go through a special physical check-up because living in space, where you're always floating around in low gravity and in a crowded spacecraft, can be really hard on your body, so everyone wants to make sure you're healthy enough to do it.  But that's it!  Thousands of people sign up to become astronauts, but only a very few are actually chosen to go on a mission.  After years of training, those lucky few finally get sent to space where they have some really important jobs to do.  

What kinds of jobs are there?  Well, some astronauts are pilots.  Their job is to get the spacecraft where it needs to go safely.  They're also in charge of getting the craft back to Earth.  Astronauts that aren't pilots are called mission specialists and they perform a lot of different jobs.  One of those jobs is to work with the pilots to keep the spacecraft and equipment working.  This means they inspect the spacecraft and its different parts every day to make sure everything is doing just what it's supposed to do. 

Another job for mission specialists is doing experiments where scientists try different things to see what happens.  Many of those experiments are done in the International Space Station or ISS.  The ISS is in orbit around the Earth and was built for astronauts to work and live in for long periods of time.  Some of the experiments that have been done on the space station have been things like growing zucchinis to see how vegetables grow in space.  Other scientists have looked at how different animals like flies or even squids get used to life in space. 

Another important job astronauts do is to help launch satellites.  These are machines that fly in orbit around the Earth and they can do all sorts of things like take pictures of the Earth or help us know what the weather's going to be like or send signals for television and radio.  Now, most of the time astronauts do their jobs inside the space station or their spacecraft, but for some jobs, astronauts have to suit up and go for a spacewalk.

A spacewalk is when an astronaut leaves the spacecraft to do their job outside, in space, and is one of the toughest jobs that astronauts do.  Astronauts do spacewalks when they need to fix or build something on the outside of the spacecraft and to do that, they have to wear special spacesuits.  There's no air in space and it's really, really cold, so these special suits protect the astronauts from the cold and give them air to breathe.  They're also protected by being tethered or tied to the spacecraft by a long cable that keeps them from floating away.

Being an astronaut sounds like hard work, but you get to see a planet from space and conduct awesome experiments and work on cool technology every day, and even go for spacewalks.  So what do you think?  Do you want to be an astronaut?  Keep learning as much as you can about space and science and who knows?  One day, it might be you up there!

Thanks for joining us today and a big thank you to our Patrons on Patreon for helping us build our observatory.  Squeaks and I are going to get to work learning lots of new stuff about space to share with you.  If you have any questions about space, planets, astronauts, or anything else in our great big galaxy, grab a grown-up to help you leave a comment down below, or send us an email to kids@scishow.com.  Thanks, and we'll see you next time here at the fort.