Components of the Universe

Note Section

The Solar System- One star and everything that orbits it.

Planets: the larger bodies orbiting the Sun (or any other star)

The planets of our Solar System [& Pluto]

The biggest planet is….-- but the biggest object in the Solar System, by far, is …..

Surface of Sun – Gas bubbles

Solar Flare – an explosive event on the Sun’s surface

Galaxy- Billions of stars bunched together.

The Sun is a star in the Milky Way Galaxy.

A spiral Galaxy seen Edge-on-the actual 3D-shaped is like a pancake with a lump in the center

How big is a galaxy?

# of stars: about a billion or so (smallest)- up to 100’s of billions for

large galaxies

Diameter: Very large: what units of distance should be used?

-- using miles gives awkwardly numbers.

-- a larger unit is needed.

-- for example…..

Light-Travel-Time from the Earth

TO TIME DISTANCE

a. the moon 1.25 sec 1.25 light-seconds

b. the sun 8.5 minutes 8.5 light-minutes

c. Pluto ~6 hours

d. Alpha Cen 4.3 yrs 4.3 LY

e. North Star 650 years 650 LY

f. M31 2.5 million yrs 2.5 M. LY

..so just keep in mind that all of those units of length

are based on the speed of light;

- for example: 1 light-minute = the distance that light travels in one minute

The “Milky Way” galaxy is a

spiral galaxy.

The Sun is in a spiral arm half-way out

from the center.

Map of Milky WayOur Sun(yellow dot) is in a spiral arm, ½-way out

Galaxies contain more than just stars. The irregular-looking blobs are either hot (pink) or cold (dark) interstellar clouds

Galaxies occur in galaxy clusters.This is M31 (the Andromeda Galaxy)…

…. and friends (2 smaller neighboring galaxies)- sort of a “triple galaxy”

LMC

SMC

comet

The Universe is Everything- All the Galaxies

Distance = 500 million LY

What can you see with the naked eye? [outside of the Solar System]

- Milky Way stars! (meaning only stars in our own galaxy)i.e., you cannot see any individual stars in any other

galaxy;-- they’re just too far and too faint

Note: Every star visible to your eye is part of the Milky Way!