Nebula

what is the orion nebula?

the nursery of newborn stars which has many contracting cloud fragments → protostars

what does the interstellar medium consist of?

gas and dust, the gas is atoms and small molecules like hydrogen and helium while dust is more like soot or smoke, there’s larger clumps of particles

what is a molecular cloud?

it contains hydrogen molecules in addition to other molecules

when does star formation happen?

when part of a dust cloud begins to contract under its own gravitational force and forms protostars, leading to the development of new stars.

what are the stages of star-formation?

The stages of star formation include the initial molecular cloud phase, gravitational collapse leading to protostar formation, the ignition of nuclear fusion in the core, and finally the maturation into a main-sequence star.

why and when does a protostar’s luminosity decrease?

it decreases as its temperature rises because its becoming more compact

what is a main sequence?

A main sequence star is a stable phase of stellar evolution where hydrogen is converted to helium in the core through nuclear fusion, producing energy that balances gravitational collapse.

what is the minimum mass to have a star?

mass is the main determinant of where a star will be on the main sequence → less mass means less pressure on the core, less temperature in the core to trigger fusion, if there’s no fusion there’s no star, and the minimum mass is about 0.08 solar masses.

what is a brown dwarf?

a failed star where it’s mass is less than 0.08 solar masses, it doesn’t have enough mass to heat its core and sustain a fusion reaction

why are brown dwarfs hard to observe?

they’re very dim

what is a star cluster?

a group of stars which were formed from the same parent cloud → because a single interstellar cloud can produce many stars of the same age & composition, star clusters are a way to study the effect of mass on stellar evolution

what are globular clusters?

roughly spherical found in the milky way plane and contain thousands of stars spread of 50 pc and usually contain older stars

what is pc?

A parsec, a unit of distance equivalent to about 3.26 light-years, used in astronomy to measure large distances between astronomical objects.

what is the Pleiades cluster?

it lies about 120 pc from the sun and has around 1,000 stars, including hot blue and luminous stars. It's also known as the Seven Sisters.