Stars & Galaxies Introduction

Asteroid

Large rocky object in space

Meteoroids

Small rocky objects in space

Meteors

Small rocky objects entering earth’s atmosphere

Meteorite

Rocky object found on Earth

Comets

Small dirty, snowballs in space.

These are in space, NOT in Earth’s atmosphere.

Mixture of ice and rock.

It was created at the formation of the solar system.

Sun

Largest object in our solar system.

4.5 billion years old.

Planets, in general, orbit the sun.

Nearly ALL the mass in the solar system is within the sun.

The sun’s radius is 100 times larger than Earth’s.

24,000 LY away from the center of the Milky Way

Stars

Have enough mass to ignite nuclear fusion in its core.

They’re self-luminous.

Nearly ALL elements in the universe were created by a star.

Other stars, beside our star, host exoplanets.

A star’s mass can range from 0.1-100 times as massive as the sun.

Born from giant clouds of dense, cold molecular hydrogen.

They from together in clusters.

Smaller clusters have shorter lifespans (vice versa)

Low mass stars are much more common than giant stars.

Self-luminous

Generate and omit their own light

Planet

Orbits around the sun in ellipses.

Has enough mass that gravity can create a nearly round shape.

Cleared the neighborhood around its orbits.

They’re far apart.

Milky-Way Galaxy

A disk galaxy (frisbee or pancake shaped).

Has about 100-400 billion stars.

100,000 LY across.

Andromeda Galaxy

Nearest galaxy to us,

Disk galaxy.

2.5 light years away.

Part of the Local Group

Local Group

Encompasses a diameter of 10 million light years (includes Andromeda, Milky Way, and M33)

It’s in the Local Supercluster.

M33 Triangulum Galaxy

Part of the Local Group.

Andromeda, Jupiter, Mars, and Sirius (bright to lightest and largest to smallest)

Brightest: Jupiter, sirius, mars, andromeda

Largest: Andromeda, sirius, jupiter, mars

Light Year

Light always travels the same speed (3.0 × 10^8 m/s).

Defines distances based on how far light would travel.

Speed= distance/time

Takes 8 minutes for light from the Sun to reach Earth.

Proxima Centauri

4.24 LY. It would take that many years to get there.

The light you’re seeing is from 4.24 years ago.

Mass

The amount of matter or ‘stuff"‘ within an object.

Different than weight.

Objects are weightless (so just mass) in space because there is no gravity.

Weight

Mass and gravity combined.

Larger Stars

They’re hotter.

They burn fuel more efficiently, making them not live as long.

Hotter stars are bluer.

Key Properties of Stars

Temperature (kelvin), size, mass, age, intrinsic brightness.

Thes affect the habitability of orbiting planets.

Luminosity (intrinsic brightness)

How much light is coming off an objects surface.

Measured in Watts.

Apparent Brightness

How bright something looks from our vantage point on Earth.

Watts/area.

Distant objects appear fainter.

As the distance increases, the light spreads out over the area.

B=L/4piD² approximated to L/12.56D²