StarsBy Danny, Tiffany, and Connor

What is a star?

A “star” is a massive, luminous ball of plasma held together by gravity.

A star forms as a collapsing cloud of material composed mainly of hydrogen, along with helium and trace amounts of heavier elements.

Stars shine due to thermonuclear fusion. This is a process where hydrogen in the core of the star, releases energy that travels through the star and eventually radiates into space.

Characteristics

Most stars are between 1 billion and 10 billion years old.

The more massive the star, the shorter its lifespan. This is because there is greater pressure in the star’s core.

Red Dwarfs can have a lifespan of up to hundreds of billions of years.

Star Types

Star Classification classified by their

spectra (elements that they absorb)

Temperature There are 7 types

O, B, A, F, G, K & M O & B stars are

uncommon but bright M stars are common but

dim

The Hertzsprung -Russell (H-R) Diagram is a graph that plots stars color (spectral type or surface temperature) vs. its luminosity. On it, astronomers plot stars’ colors, temperature, luminosity and evolutionary stage

Hertzsprung-Russell Diagram This diagram shows 3 different types

of stars Main sequence stars Super Giants/Giants Dwarf stars

Main Sequence Stars

Young stars Fueled by nuclear

fusion (converting hydrogen -> helium)

90% of stars are Main sequence stars

The hotter the brighter Yellow dwarf & Red

dwarf

Giant/Super Giant stars Old large stars These stars have depleted their hydrogen supply

and are very old. The core contracts as the outer layers expand. These stars will eventually explode

Red GiantA red giant is a relatively old star whose diameter is about 100 times bigger than it was originally.

Blue GiantA blue giant is a huge, very hot, blue star. It is a post-main sequence star that burns helium.

A supergiant is the largest known type of star; some are almost as large as our entire solar system.

Super Giant

Dwarf Stars

Small faint stars

White Dwarf

A white dwarf is a small, very dense, hot star that is made mostly of carbon. Their nuclear cores are depleted. They are about the size of the Earth and will eventually become a black dwarf

Binary Star A binary star is a system of two stars

that rotate around a common center of mass (the barycenter). About half of all stars are in a group of at least two stars.

Our Sun

The closest star to the earth is the sun.

The earth receives most of its energy from the sun.

The sun in our solar system is approximately 4.5 billion years old.

Works Cited

"Stars." Imagine The Universe! Home Page. Web. 14 Mar. 2011. <http://imagine.gsfc.nasa.gov/docs/science/know_l2/stars.html>.

"Stars." Universe Today. Web. 14 Mar. 2011. <http://www.universetoday.com/24184/stars/>.

"Stars, Constellations, Galaxies and Nebulae Facts." Kid's Cosmos-Science Resources for Teachers and Students. Web. 14 Mar. 2011. <http://www.kidscosmos.org/kid-stuff/stars-facts.html>.