Lecture 3 - Nature of Light Flashcards
Earth is the ____ planet from the sun
Earth is the 3rd planet from the sun
describe the galaxy of Earth
Earth is in the spiral arm of the Milky Way, which is in the Local Group, which is in the Local Supercluster
what is the shape of the Milky Way
disk
approx how many stars are in the milky way?
> 100 billion
where is our solar system in the milky way disk?
a bit over halfway from the center
describe the composition of the galaxy
5% stars and planets
the rest is gas and 90% dark matter
- what is dark matter
- what does dark matter look like, why?
- particles that don’t produce light and don’t interact with anything else
- looks like a spherical ball –> not disk shaped bc it doesn’t interact with anything and is collapsed with gravity
where is most of the mass of a galaxy located?
outside the visible disk in a galactic halo
what is a star? what is a binary star?
star = large, glowing ball of gas that generates heat and light thru nuclear fusion
binary star = 2 stars that orbit each other
what is a black hole? where is it located?
black hole = star that has collapsed on itself and gotten so small that a huge gravitational force pulls into it, so any light that enters is turned around –> irreversible
**its curvature changed with gravity
located at the center of every large galaxy
- what is a planet?
- how do planets shine? how do planets glow?
- what types of material can planets be made of?
- large object orbiting a star
- shines by reflected light, glows in radio waves
- can be rocky, icy, or gaseous
what makes mars red?
depends on whether you are looking at reflective light from inside or outside the atmosphere
what is a moon/satellite?
object that orbits a planet
what is a moonmoon? are there any known moonmoons?
moon that orbits another moon
no known moonmoons
what is an asteroid?
small, ROCKY object that orbits a star
what is a comet?
small, ICY object that orbits a star
what is a nebula? when do they light up?
interstellar cloud of gas and/or dust btwn stars
light up when ionized
what is a galaxy?
island of stars in space held together by gravity and orbiting a common center
when we look at space, what are we also looking at?
looking at space = looking back in time
further away we look in distance = further away we look back in time
what does it mean when we see the Andromeda Galaxy 2.5 million ly away?
we are looking at the galaxy as it looked 2.5 million years ago and in 2.5 million years we can see what it looks like right now
can never see the galaxy go thru its evolution, just see what it was before
