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Catalyst. 1. Explain what would happen if your twin traveled to a nearby star at close to the speed of light. What would happen when he or she came back to earth? 2. Why is the Hubble an important telescope?. Today’s Agenda. Shape of the Galaxy. Spiral Galaxy

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1. Explain what would happen if your twin traveled to a nearby star at close to the speed of light. What would happen when he or she came back to earth?

2. Why is the Hubble an important telescope?

Today s agenda

Today’s Agenda

Shape of the galaxy

Shape of the Galaxy

  • Spiral Galaxy

    • Rectangular block of stars at the center, called a bar

    • Bar is 27,000 light-years from end to end

  • Was this picture taken by a telescope?

In the center

In the Center

  • At the very center of the galaxy is a supermassive black hole

  • This black hole sucks stars towards it at fantastic speeds

  • Why don’t we get sucked in?

    • It’s 250,000,000,000,000,000 kilometers away

  • New theory– black holes form in the center of all galaxies

    • More on that next week

Our galaxy is a cannibal

Our Galaxy is a Cannibal

  • It rips apart other galaxies that pass too close!

  • Their stars become part of our galaxy, so the whole galaxy becomes bigger, which makes it more likely that it will ingest other nearby galaxies

Here s what we can see from earth

Here’s what we can see from Earth

What we can t see

What we can’t see…

  • On a clear, dark night, you can see thousands of stars

  • The Milky Way has two hundred billion stars in it

  • The sun’s light is too dim to see too far away

  • Most stars are too dim to be seen from very far away anyway

  • Using some fancy physics, we can calculate the mass of our galaxy and the mass of all the stars

  • But the numbers don’t match up– the stars only take up 10% of the mass of the galaxy. What’s the rest?

Dark matter

Dark Matter

  • Something that has mass but we can’t classify it right now

    • Not black holes, not dead stars, not gas, not rogue planets…

What else can we see

What else can we see?

  • Andromeda Galaxy

    • Closest neighbor

    • We can see it on a dark, moonless night

    • Appears to be 8 times the size of the moon from our viewpoint

  • But in two billion years, it will appear MUCH bigger

    • Our galaxies are coming toward each other at 200 km per second

  • What will happen when they collide?

    • Individual stars will not collide, but there will be giant, sweeping arms of stars and gas that will settle in a few billion years in a new, merged galaxy

Today s agenda1

Today’s Agenda

Words to know

Words to Know

  • Crescent: moon is less than half full

  • Gibbous: moon is more than half full

  • Waxing: moon is becoming more full

  • Waning: moon is becoming less full

    • Example: Waxing gibbous would mean that the moon is more than half full, and it is on its way to becoming full

    • Example: Waning crescent would mean that the moon is less than half full, and on its way to becoming a new moon

Did you know

Did you know?

  • The same side of the moon always faces the Earth

  • The moon’s cycle is 29.5 days, so sometimes there will be two full moons in one month

  • When the moon blocks the sun (or part of it), this is called a solar eclipse

    • Can only happen during the “new moon” phase

  • When the Earth casts a shadow on the moon, it is called a lunar eclipse

Solar eclipse 1999

Solar Eclipse (1999)

Lunar eclipse right now

Lunar Eclipse (right now!)

Today s agenda2

Today’s Agenda

Exit slip

Exit Slip

  • Free write about what you learned today. (At least 5 sentences.)

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