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Dominique Christianson

on 18 May 2015

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Transcript of Stars

Most people are familiar with stars but don't know much about them. Stars are usually seen at night when lights are dim and they twinkle in the sky. A star is a luminous ball of gas made up of mostly Hydrogen and Helium held together by its own gravity. Through nuclear fusion stars produce their own energy and light. The sun is the closest star to Earth.
How are stars classified?
Stars are classified by their spectra and temperature. Their are 7 main types of stars, from decreasing temperature; O, B, A, F, G, K, and M.
The most famous stars
Some of the most famous stars are ones that are in well known constellations or are very bright in the sky.
Polaris- North Star
Sirius- the "Dog Star", easy to spot
Alpha Centauri B- close system to Earth, Earth like planet found in 2012 around the star
Betelgeuse- easy to spot, soon to be a supernova
Rigel- bright blue star, only 10 million years old
Compare these stars to the size of the Sun.
How do stars form?
How far away is the closest star to our solar system?
Life cycle of Stars
Are they part of a constellation?
How far away are these stars?
Is our Sun a binary star system?
Works Cited
The closest star to our Solar System is the Polaris
star. It is about 323 light years away from the Earth and Sun. Polaris is more commonly known as the North Star. It is the brightest star in the Ursa Minor constellation.




Stars form within a cloud of dust. The cloud then begins to collapse due to turbulence under its own gravitational attraction. As the cloud collapses it breaks into smaller clumps, called knots. At the center of these knots, the material becomes hotter, and more dense. When the outward pressure balances against the force of gravity pulling it in, a protostar is formed. Depending on the size of the material, determines the type of star will be formed.
At least half of all stars are in a group of 2 or more stars.
A double star is 2 stars that are in the same line of sight that look close to each other but do not revolve around one another.
A binary star is a system of 2 stars that rotate around a common center of mass.
Sun- 1.989e30 kg

Polaris is 40 times bigger than the Sun!
Life Cycle of a Star
Life Cycle of a Star
Stars are born in a nebula. Then the cloud starts to shrink and starts to collapse onto a number of points within the cloud, all due to the pull of gravity. In the middle of these cores, it gets very hot and dense. When this happens, nuclear fusion can start and the star is born. This is called stellar ignition.
The next stage in the life cycle of a star is an average star or a massive star. The energy in a star is produced in its core, by nuclear fusion. This energy emerges from the star as heat and light so that the star appears to glow.
Life Cycle of a Star
In 1905, two astronomers, Einar Hertzsprung and Henry Russel, noticed that the luminosity of stars decreased with the temperature of the stars from O to M. The Hertzsprung-Russel diagram (H-R diagram) is a scattered plot graph that astronomers use to classify stars according to their temperature, spectral type, color, luminosity and evolutionary stage.
Then comes the Red Giant or Red Supergiant stage.Hydrogen fuel at the center of a star becomes exhausted, and a shell of nuclear reactions will start to move outwards into its atmosphere. The outside of the star will begin to expand and cool, and turn much redder in color. Over time, the star will become a red giant and grow to be more than 400 times its original size. The stars outer layers return to normal and then starts to shrink, heat up and turn blue. This stage lasts for about a million years, while the helium runs out quickly. When all the helium runs out, the star starts to grow, cool and turn red again as it begins the next stage called second red giant phase.

What happens next to the star depends on the mass of the star. Small sun-like stars move into a planetary nebula phase, while stars greater than about 8 times the mass of the Sun will most likely end as a supernova.
Life Cycle of a Star
Distance from Earth:
A low-mass star turns into a planetary nebula at the end of its red giant phase. The star becomes highly unstable and starts to pulsate. The outer layers are ejected by the resulting stellar winds. Planetary nebula live a relatively short life just for a few tens of thousands of years.

A supernova is form when an explosion occurs.The high-mass star will eventually out of nuclear fuel. With there being any outward pressure to balance the inward force of gravity, the outer layers of the star collapse onto the core. They are now dramatically expelled in a nuclear explosion. Now there is a resulting shock wave that will create an expanding shell of gas and dust called a supernova remnant.

Polaris- 433.8 light years
Sirius- 8.611 light years
Alpha Centauri - 4.367 light years
Betelgeuse- 642.4 light years
Rigel- 772.9 light years.
Even though many stars are part of a binary star system, the sun is not. There is no evidence that the sun has a companion and the theory has been disproved by many infrared sky surveys.
Life Cyle of a Star
The last stages of a stars life that are possible to become are a White Dwarf, a Neutron Star, or a Black Hole.
Polaris is part of the constellation Ursa Major.

Sirius is part of the constellation Canis Major.

Alpha Centauri B is part of the Centurus constellation.

Betelgeuse and Rigel are in the Orion constellation.

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