Test 2 - Galaxies and Stars Flashcards
what is a galaxy
a huge group of stars, gas, and dust held together by gravity
- there may be several billion galaxies in the universe, and they all could contain billions of stars
what is the closest galaxy to us?
Andromeda Galaxy - 2.5 million light years away
what is the closest galaxy to us?
Andromeda Galaxy - 2.5 million light years away
what is a nebula
a cloud of gas, dust and stars (similar to galaxies but much smaller- nebulae 10 to 100 light years, galaxies 100 - 1000 light years)
4 types of galaxies
spiral, elliptical, barred spiral, irregular
characteristics of a spiral galaxy
large amounts of gas, dust and many young bright stars
looks like a pinwheel
flat w a central bulge
2-4 rotating arms
majority of galaxies we have observed
characteristics of a barred spiral galaxy
similar to spiral but with a central bar – the arms extend from the bar
characteristics of a elliptical galaxy
contains very little gas or dust, older reddish stars
looks like flat circles
could be perfectly circular or more elliptical
account for 20% of the galaxies we have seen
characteristics of a irregular galaxy
contains mostly gas and dust with few stars
no definite shape
10% of galaxies we have observed
describe the milky way
barred spiral
100 000 light years across
4 spiral arms
constantly rotating – our solar system travels with the galaxy at 800 000 km/hr
over 200 billion stars, massive gas halo surrounding it
our solar system is in one of the 4 spirals
what is a black hole
an area of space that has no volume but a tremendous amount of mass – where the force of gravity is so strong that even light cannot escape
the boundary of it is called an event horizon, but it cannot be seen
how is a black hole formed
when a supernova from a star collapses and the force of the gravity forms a hole.
the first image of a black hole was taken on April 10, 2019
what is a light year
measure of distance
1 ly = 1.5 trillion km
helps us keep track of distances outside our solar system
how to stars form
3 main stages:
1. Nebulae - stars form in a nebula
2. Protostar
3. Fusion - core temp increases and pressure until ignited and it creates a burning ball of gas
what is a star
giant burning sphere of gases
composed mostly of hydrogen
nuclear fusion releases large amounts of heat radiation and light energy
nuclear fusion is allegedly how the elements of matter were created
what causes a star to become a supernova
as the star runs out of fuel, (iron is the last element that can be fused) eventually, the core is so heavy and dense that it’s own gravity can’t hold it up anymore, so it collapses in on itself
that is how all elements heavier than iron were formed
what are the two types of fate for a star
low mass & high mass stars
describe a low mas stars lifecycle
stable and long lived (billions of years)
1. when they run out of fuel they cool down and expand becoming a red giant
2. over time, they burn out and release the outer layers of matter and gas into space
3. remaining core becomes a white dwarf star to a black dwarf star once cooled completely
describe a high mass star
unstable, short lived (thousands of years)
1. they run out of fuel and cool down and expand becoming red supergiants
2. a supernova occurs because the core collapses on itself (or it fizzles out)
3. the core of the star becomes compacted during the explosion forming a neutron star (super small and dense and rapidly spinning)
3. if there is enough mass, the high pressure of the supernova can create a black hole
how are stars classified?
- Size
- Luminosity - amount of light emitted
- Colour - based on temp
how is a stars size measured
compared to our sun size doesn’t always mean more mass
(see onenote for image explanation)
describe luminosity and how it is measured
luminosity = the measure of total light energy it gives off per second.
Our sun gives off 3.8 x 10^26 watts = 1Lsun
Other luminosities are compared to our sun. – the greater the surface area, the greater the luminosity
how is colour used to characterize stars?
the colour of a star relates to it’s temperature
more cool = red appearance
more hot = blue appearance
what are the main classes that stars are grouped in?
Left to right:
O B A F G K M
