Unit 3- Astronomy

I don't want to fail

star

a large ball of gas held together by gravity with a core so hot that nuclear fusion occurs.

H-R Diagram

a graph that plots luminosity v. temperature of stars.

main sequence star

A star that fuses Hydrogen to Helium in its core

Giant Star

a star with a much larger radius and luminosity than a main sequence star of the same surface temperature.

White Dwarf

forms as the core of a giant star no longer supports fusion and the star’s outer layers escape into space, leaving a hot and dense core.

nebula

A cloud of gas and dust

protostar

a cloud of gas and dust in space that develops into a star.

planetary nebula

formed after helium in a star’s core is gone, it casts off its gases.

supernova

an explosion that destroys a star

black hole

an area in space that is so dense that nothing, including light, can escape its gravitational pull.

nuclear fusion

The fuel source of a star.

The more massive a star is,

the greater the force of gravity pressing inward

Heat

Maintains the balance between gravity pushing inwards and pressure expanding outward. It also controls rate of fusion.

Luminosity is and depends on

Luminosity is how bright it is and depends on temperature, mass, apparent magnitude, and distance are related.

Spectral Class and their colors

O is Blue, B is Blue-White, A is White, F is Yellow-White, G is Yellow, K is Orange, and M is Red (Oh be a fine girl kiss me)

Percentage of stars smaller than the Sun

75%

Mass depends on

temperature and its luminosity and color

HIgher mass stars last longer than lower mass stars and why?

Lower, because higher mass stars go through there fuel at a faster rate than lower mass star.

H-R diagram axies

y-axis is increasing luminosity and x-axis is DECREASING temperature

Giants appear when:

the star runs out of hydrogen and has to fuse heavier elements

What Element does nuclear fusion ends at?

Iron

Dwarfs are:

the corpse of a star after a giant stars runs out of fusion. Usually have average or low radius, luminosity, and mass

What causes the densest parts to collapse and form what?

Gravity and form protostars

What happens when they are a protostar?

They pull in surrounding gas, until their cores are hot enough to star nuclear fusion.

What might happen to the surrounding gas and dust blown away from the formation of the star?

They could turn into planets or other objects that would orbit the star

The star spends most of its life in?

Main sequence star

It would continue to be a main sequence star as long as

hydrogen is fusing into helium

What happens when the fusion of hydrogen and helium stops?

there is no outward pressure to counteract the force of gravity.

If the star doesn’t get hot enough it turns into a:

white dwarf after it casts off its gases, forming a planetary nebula

Stars that are 8 times bigger than the mass of Sun become:

supernovae

Why do supernovas happen?

The reason is because they are able to create iron. When they try to use for nuclear fusion, the core collapses under the force of gravity.

How neutron stars happen?

For stars one billion times brighter than the sun can form elements heavier than iron. A neutron stars forms as a result.

What happens to very massive stars?

The core collapses past the neutron star stage and forms a black hole.

Supernova remnants are:

An expanding cloud of dust and gas from a supernova that collects on the gas and dust that it encounters

Kelvin

The way they show temperature in space

Galaxy

a huge collection of stars, gas, and dust.

Light-year

the distance light travels in a year

Dark matter

An invisible form of matter that does not emit any electromagnetic energy of its own

Elliptical Galaxies

Are shaped like ovals. They have the highest percentage of old, red stars that other galaxies. The reason is because they contain little or no gas.

Irregular Galaxies

Form from the gravitational pull of neighboring galaxies. Gas and dust abundant in these galaxies which is the reason of them having many young stars. Range from 3000-30,000 Light-years in diameter

Spiral Galaxies

A Galaxies that extend curved arms of higher luminosity. They have an area called the nuclear bulge where the they are thicker near the center of the Galaxy. They range from 20,000-20,0000 lightyears.

The closest galaxy is

Andromeda Galaxy

The three main parts of Spiral Galaxies are

A disk, A central nuclear bulge, and a spherical halo

Big Bang Theory

The theory that the universe began at a point, where it had a rapid expansion from that point. At first, it moved very quickly, then suddenly slowed down. It is now picking up speed from the more matter being created means more dark matter being created.

Universe

All of space and everything in it including stars, planets, and galaxies.

Doppler shift

A shift to a different wavelength depending on your relative location.

Red shift

Stars that move farther away.

Blue shift

The stars are moving closer

Dark energy

The invisible form of energy that creates a force causing the universe to expand.

How much of dark energy is there?

68%

The main characteristics of stars

color, temperature, size, and brightness

Apparent Brightness

How bright the sun is from Earth; It’s very easy to measure and not accurate.

Absolute Brightness

A star’s brightness if placed at a standard distance; very accuracy, but need to distance