a fixed luminous point in the night sky which is a large, remote incandescent body like

Chapter 8:

• Some stars look as if they are grouped in a distinct cluster

• Constellations1 are recognisable even from earth

• There have been a total of 88 constellations as of now

• Stars within the same constellation can vary in terms of distance from the Earth

• All stars form inside a collapsing nebula

Inside the collapsing nebula, the place with the greatest amount of mass will begin to draw material towards it through gravity. The material that is pulled in has excess energy which causes the material to spin, thus pressure and an increase in temperature. Through this process, the temperature will be able to read around 1000°C, and is hot enough for nuclear reactions. Lastly, over thousands of years, the energy flows to the outside of the star and begins to shine.

• Iron fuses does not release energy

• Stars also have a predictable life cycle

• How they evolve depends on the mass they have when they were originally formed (therefore a star with a low mass goes through different stages than stars with a high mass)

• There are three different categories of mass (low, medium and high)

Different mass star attributes:

• Low mass stars use less fuel than higher mass stars, leading to them being able to last for 100 billion years

• Nuclear reactions in a low mass star also happen at a slower rate

• Medium mass stars uses their fuel faster than low mass stars, thus only being able to last around 10 billion years

• When their fuel runs out, they collapse under their own gravity, and the fusion of helium occurs. The star expands rapidly into a red giant2 and as the helium fuel burns out, so does the star

• High mass stars are reasonably the biggest, hottest and bluest stars

• Always comes to a violent end at around 7 billion years

• Like the other categories of mass stars, when their fuel runs out, they likewise cause helium fuel to fuse. Causing the high temperatures to make the star expand into a supergiant3

• When the helium runs out, the core will continue to collapse with itself and the star continues to go through various levels of collapse and expansion (causing new elements to form)

• If too much of their core is made up of iron, they will turn off in minutes

• With no more fuel, they end for the last time

• The star’s remaining core after a supernova explosion faces one of two outcomes, depending on the mass of the original (neutron stars and black holes)

In the Hertzsprung-Russell diagram, they organize starby their physical properties:

• Colour

• Luminosity

• Surface temperature

• Larger particles in space grow faster than smaller ones due to more collisions

• The moon was the result of a collision

• We have found out methods to determine an asteroid’s age

• Astronomers believe that ice acted as a kind of glue to cause gas and dust particles to stick together

• There are also minor planets (e.g. Pluto)

Keywords:

1Constellation — the configurations of stars

Asterisms — smaller recognizable star patterns within a larger constellation

Astronomical phenomenon — any observable occurrence relating to astronomy

Prostar — a star in its first stage of formation

2Red giant — a very large star of high luminosity and low surface temperature. Red giants are thought to be in a late stage of evolution when no hydrogen remains in the core to fuel nuclear fusion

3Supergiant — very large star that is even brighter than a giant, often despite being relatively cool

Neutron stars — if the star us between 10 and 40x the Sun’s mass

• Made from the densest material known

• When the star’s core becomes little more than a ball of neutrons only about 15 km across, it is called a neutron star

Black holes — if the star is 40x+ the Sun’s mass

• Doesn’t stop collapsing

• Nothing can escape

Comet — celestial object made by ice and dust

Meteor — a meteoroid that upon entering Earth’s atmosphere, begins to burn up as a result of friction