y10 universe

components of the universe, light-years, nuclear fusion, life cycle of a star, big bang theory

universe

all of space and time and the matter and energy they contain

astronomy

the study of the universe

galaxies

clusters of billions of stars held together by gravity

star

a hot, bright ball of gas held together by gravity

planet

a natural satellite that orbits a star

moon

a natural satellite that orbits a planet

asteroids

irregular, rocky objects that orbit a star, often in large belts

comets

masses of ice and dust that orbit a star along very oval paths

light-year

the distance light travels in one year

what is the distance of a light year?

9.5 × 10^12km (9.5 trillion)

magnitude

how astronomers measure the brightness of a star

apparent magnitude

the brightness of an object as it appears in the in the night sky

absolute magnitude

measures the brightness of a celestial object if it was placed at a certain distance from Earht

what is the standard distance from Earth that absolute magnitude is measured at?

10 parsecs or 32.6 light years

nuclear fusion

a nuclear reaction in which two atomic nuclei join together

at what temperature does nuclear fusion occur?

13 million degrees

what happens as a result of nuclear fusion?

hydrogen is converted into helium

massive amounts of heat and light are released

main sequence stars

a star that is fusing hydrogen and in a stable state

how are stars formed?

they begin as vast clouds of dust and gas called nebulas

gravity pulls the gas into a dense ball called protostars

as the gas condenses, the temperature begins to increase

a star is formed once hydrogen fuses into helium and nuclear fusion begins

nebulas

vast clouds of dust and gas

protostars

dense balls of gas that haven’t yet developed into a star

small star

a star with less than 8 times the mass of the sun

what is the life cycle of a small star?

once hydrogen begins to run out, it begins to fuse helium, causing the outer layers to expand into a red giant

it further expands into a planetary nebula as the outer layers escape the core’s gravity

once the outer layers have drifted away, what is left is the hot, dense core known as a white dwarf

the core eventually cools off into a black dwarf

red giant

a small star that fuses helium, causing its outer layers to expand

planetary nebula

a nebula formed from a red giant

white dwarf

the remains of the core of a small star

large star

a star at least 8 times the mass of the sun

what is the life cycle of a large star?

the large mass allows the star to keep fusing past carbon and oxygen, forming red supergiants

it ejects most of their mass in catastrophic explosions known as supernovas

after a supernova explosion, a star leaves behind either a neutron star or a black hole

red supergiant

a large star that fuses helium, causing its outer layers to expand

supernova

an explosion of a red supergiant

neutron star

the tiny remains of the core of a large star made up of densely packed neutrons

black hole

an object that has gravity so strong that not even light can escape it

the big bang theory

the universe was created when a tiny, super-dense, super-hot mass exploded and began expanding very rapidly, eventually cooling and forming into the stars and galaxies we observe today.

redshift

when a star moving away from you appears red

blueshift

when a star moving towards you appears blue

what is hubble’s law?

all galaxies are moving away from us

the further they are, the faster they are moving away

what is einstein’s theory?

galaxies aren’t moving away from us through space, but through the expansion of the space between the galaxies itself