Download Characteristics of Stars

Characteristics of Stars
What is a galaxy?
It is a cluster of stars (hundreds of billions
of stars)
 Our solar system is located in the Milky
Way Galaxy

* Our galaxy is named the Milky Way
because of it’s white milky color. Not
because of the candy bar!!!!
What is the Universe?

All of space and everything in it!!!!


Consists of billions of galaxies.
Most of the Universe is empty space, due
to everything being soooooo far apart!
Distances to Stars

Instead of using kilometers, astronomers use a
unit called light-year.

A light year is the distance light travels in one
year or 9.5 million million kilometers.
* If we wanted to travel to the center of the Milky
Way it would take 25,000 years traveling at the
speed of light. That is a distance of 250 million
billion kilometers.
Measuring Distances to Stars

Parallax- apparent change in position of an
object when you look at it from different places.
(Thumb example)

Astronomers use the parallax shift to measure
distance to stars:



First they observe a star & then observe it again 6
months later.
The less the star moved the further away it is
The more the star moved the closer it is
Classifying Stars

Three main characteristics:
Size
 Temperature
 Brightness

Size
Color & Temperature

A star’s color reveals its temperature:

Stars that are red are the coolest (3,200
degrees Celsius)
 Betelgeuse

Stars that glow blue-white are the hottest
(15,000 degrees Celsius)
 Rigel
Brightness

Brightness of a star depends on its temperature
and size.

How bright a star is also depends on its distance
from Earth.

Brightness is described in two different ways:


Apparent magnitude
Absolute magnitude
Brightness

Apparent Magnitude

Brightness as seen from
Earth.
Ex. Sun looks very bright
but this does not mean
the sun gives off more
light than other stars. It
just means it is closer to
Earth.
Absolute Magnitude


Brightness a star would
have if it were at a
standard distance from
Earth
Astronomers determine
the apparent magnitude
and distance from Earth
in order to calculate the
absolute magnitude
Hertzsprung-Russell Diagram