More planets -- Mars, Jupiter, and Pluto -- and Earth's moons

This week we started by talking about how people have decided what is a full planet, versus a dwarf planet, moon, or asteroid.

The definition of a full planet is

• a body that circles the sun without being some other object's satellite (that would be a moon)
• is large enough to be rounded by its own gravity
• is not so big that it becomes a star, and
• has cleared up all the other nearby space junk

  

  Pluto's weird orbit

Scientists recently agreed on these conditions because they had to decide if Pluto could still be called a planet.  It's much smaller than the others, more the size of our moon, and it turns out there are several other objects slightly larger than Pluto also way out far from the sun in the Kuiper belt (which is a giant collection of space junk/asteroids out beyond Neptune).  Pluto also has a weird orbit, but that is not part of why Pluto got demoted.  It was because it has not cleared up all the other nearby space junk.  

So, we only have 8 planets for now.  The first one we discussed in class was Mars, the red planet.  

Mars volcanoes

• Mars has the largest volcanoes in the solar system, including Olympus Mons, which is huge.
• There are many large valleys, including one gigantic valley, and they were formed by the stretching of the planet's crust early in the formation of the planet.
• There may have been liquid water on the planet, but now there is only ice.
• Frost made of dry ice forms in the winter time.  Dry ice is frozen carbon dioxide.
• Mars has seasons but no magnetic field.  I think that would make it harder for life on earth to try living on Mars because our life forms have developed within a magnetic field, but I'm not sure.
• Mars has two moons, and the guy who discovered them was an American.  In 1877 he searched for them and almost gave up the search.  His wife urged him on and he finally saw them.  Both are smaller than our moon and are not round.

  

  Mars' two moons - Phobos and Deimos

• In the next 50 million years, Phobos, one of the moons, will smash into Mars or break up.
• Many missions have looked at Mars, and two orbiters are staying there.
• Mars might have had life or might still have life, but we aren't sure.

Next, we talked about Jupiter, the gas giant.

• Jupiter is the most massive planet, more than twice the size of all the others combined.
• It would have been a star if it had been 80 times bigger.  It is 1300 times the size of the earth.
• Its atmosphere is like the sun, which is helium and hydrogen.
• It has four large moons and many smaller ones -- a total of 63 moons.
• The Great Red Spot is an enormous hurricane, three times the size of earth, that has been going on for over 300 years.

  

  Jupiter's Great Red Spot -- a huge hurricane

• Jupiter's magnetic field is 20,000 times stronger than the earth.
• It spins the fastest of all the planets, rotating once every 10 hours, and that makes the planet bulge.
• It broadcasts radio waves that we can detect, and has faint rings around it.
• Jupiter might have flung objects at the inner planets long ago, but in recent times probably protects us from incoming objects.
• There is no evidence of life on Jupiter.

Lastly, we looked at how the phases of the moon work.

• The moon goes around the earth, while the earth is orbiting the sun.  
• It takes a month for the moon to have one complete cycle.
• The moon always faces the earth -- it never shows the earth its butt!!!
• The sun always lights up half of the moon, but from earth we only see the whole lit up side once a month.  The rest of the time we see part of the lit up side.
• The phases of the moon are:
• New moon -- you can't really see the lit part of the moon at all

  

  Moon phases -- sun is left, earth is in the center

• Crescent moon -- you see a sliver of the moon
• Half moon -- you see half the lit part of the moon
• Gibbous -- you see about 3/4 of the lit part of the moon
• Full moon -- you see the whole lit part of the moon, and it looks like a circle

Our Solar System -- Supernovas, collisions, toxic atmospheres!

This week, we focused on our own solar system.  Based on observations through telescopes, mathematical calculations, and other information, astronomers think the solar system formed about 4.5 billion years ago.  Our galaxy, the Milky Way, formed about 9 billion years ago, and the Big Bang at the beginning of time was about 14 billion years ago.

Our solar system was formed when a big cloud (called a nebula) of space debris started to collapse together and spin.  The most important thing that happened before that was that other stars had formed and become supernovas.  This means they got really hot and exploded, and that

• created the cloud of debris that then became our solar system
• made all the heavier elements in our solar system (the first stars were made up of mostly hydrogen and helium, and a little lithium, and only from supernova explosions were heavier elements created)
• sent shockwaves out that caused the cloud of debris to start collapsing and forming our solar system

This is a real supernova explosion

Stars become supernovas and explode all the time.  People looking through telescopes at home sometimes find them, when they notices a star suddenly become brighter.  The whole thing takes about 3 weeks for us to observe.

The sun will not become a supernova, because it doesn't have enough mass, but it is expanding and will make Earth uninhabitable in about a million years.

When our solar system formed, the planets began to orbit around the sun and also rotate.  The time it takes to go once around the sun (orbit time) is what we call a year.  The time it takes to rotate one full time is what we call a day.  On Earth, it takes 365 days (a year) to orbit the sun, and 24 hours to rotate (a day).  There are seven other full planets in our solar system.

The sun and the 8 planets of our solar system.  You can see the order and sizes of the planets.

The four planets closest to the sun are the terrestrial planets.  They have a rocky surface, and the four farther planets are mostly gas.

Mercury is closest to the sun, and it is about the size of our moon (small).  It is very hot especially on the day side of the planet, facing the sun.  It gets to about 840 degrees F!  But it also gets cold on the night side, facing away from the sun, way below freezing!  That's because it doesn't have an atmosphere, which helps keep heat in and protects the planet.  There are lots of craters all over it, and nothing can live there.  It takes 88 days for Mercury to orbit the sun, and a day lasts 59 Earth days!

This is a picture by one of the probes that looked at Venus

Venus is the second planet, and it is actually hotter than Mercury because of the runaway greenhouse effect.  It has an atmosphere of carbon dioxide and sulfuric acid, and very high pressure.  Two probes were sent to look at Venus and they both lasted only an hour before they were destroyed by the conditions.  It takes Venus 225 days to orbit the sun, and 243 days to rotate one time.  Venus rotates in the opposite direction of the other planets and very slowly, because a very long time ago a giant chunk of space debris called a planetesimal hit it very hard.

Earth, the third planet, has a surface that is 2/3 liquid water, which is why it looks blue.  It has an atmosphere of mostly nitrogen and oxygen.  These two things are very important for allowing life to exist.  Earth has one moon that orbits it, and we'll talk about how scientists think the moon was formed!

This shows Olympus Mons compared to Earth's tallest mtns.

Mars is called the red planet because it looks reddish; the red color comes from the iron, like rust.  Mars has a really high mountain on it, called Olympus Mons, which is about 3 times larger than Mount Everest (Earth's tallest mountain).  There's no such thing as Martians, but people are still looking at whether maybe life existed on Mars in the past.

How it all started

We started our astronomy class by talking about how everything began.  The word cosmology means the study of the origins of the universe, and people have wondered throughout history and pre-history where we and everything else came from.

The theory that most scientists believe is called the Big Bang, and basically it's that there was a giant explosion nearly 14 billion years ago that everything in the universe came out of.  In a fraction of a second, matter was created.  It took about a billion years for the first stars to form, and our galaxy, the Milky Way, has some stars that old.

The Milky Way is a spinning galaxy, with spiral arms that come out from a giant black hole in the center.  Our sun is only one star in the galaxy and there are about 200 to 400 billion other stars in the Milky Way.  Here's a map of where our sun and solar system are in the Milky Way.

Our galaxy is right now eating up another galaxy called the Canis Major Dwarf Galaxy, and we have eaten up other galaxies before.  We're cannibals!!!  Also, the nearest other galaxy, Andromeda, is headed for a collision with us, which will happen in about 4 billion years.  Here's a video simulation of what scientists think it was like when our galaxy formed.  Basically, the gases started to blob up and fall together and spin, and some blobs squished themselves up so much they became hot and formed stars.  

Our solar system formed about 4.6 billion years ago when a cloud of dust and gas collapsed.  Then the sun formed when dust and matter squished together so much that it became a hot ball.  The rest of the stuff started spinning and formed the planets and their moons.  There are still chunks of debris floating around in the asteroid belt and the Oort cloud.

Next week we'll learn more about the history of our solar system -- it was pretty violent!

Class is starting up!

We're about to have our first class meeting.  The syllabus is ready, and boy will we be learning about cool stuff!!!

In this class, we’ll explore theories and evidence about how the universe began, how galaxies and our solar system formed, the chances of intelligent life elsewhere in the universe, the history of funky events in our solar system, cool stuff that happened to earth in the past 4 billion years, all the different directions our planet is moving in, what our planet is made up of, how weather and clouds work, why we have deserts, tropical forests, and icecaps, global temperature concerns, wind patterns on earth, tornadoes, hurricanes, tsunamis, earthquakes, volcanic eruptions, plate tectonics, latitude and longitude, the moon cycles, eclipses, the atmosphere, glaciers, and the ozone layer.  With each topic, I’ll go over what our current knowledge is, and what questions are being explored scientifically in the present.  There will be a lot of hands on activities and games, as well as some multimedia movies.   

Date      Topic (these are flexible and will be adapted to student interest or new discoveries

9/11       How the universe began and how our solar system formed

9/18       History of our solar system and the planets

9/25       All the directions we are moving in and the chances of intelligent life elsewhere

No Class on 10/2

10/9       Earth’s history and what it’s made of

10/16     Moon cycles and eclipses – Optional Evening Observation Session at Washburn 9 pm

10/23     Weather and clouds

10/30     Tornadoes, hurricanes, and tsunamis

11/6       Glaciers and the ice ages

11/13     Plate tectonics, earthquakes, and volcanoes

11/20     Latitude and longitude

No class on 11/27

12/4       Our atmosphere, the ozone layer, and global warming – Optional afternoon field trip to ALNC

12/11     Party!  (Final Quizshow on everything we’ve learned)