Login | Sign Up | Print Page
Enchanted Learning Logo Enchanted Learning Logo
Home Site Index What's New Free Sample Pages Login Subscribe
Follow us on Twitter Like us on Facebook
Advertisement.

EnchantedLearning.com is a user-supported site.

Site members have full access to an ad-free, print-friendly version of the site.

Click here to learn more.

title image

All About Stars

AstronomyScienceStars (Astronomy)
Astronomy Table of Contents►
Astronomy Site Index►
Share this page:
Share on TwitterShare on FacebookShare on PinterestPrint this Page
Table of Contents
  • What is a star?
  • Group of stars
  • Why are stars hot and bright?
    • Nuclear fusion and nucleosynthesis
  • What is the closest star?
  • Why do stars twinkle?
  • Stellar wind

What is a star?

The Sun Each star in the sky is an enormous glowing ball of gas. Our sun is a medium-sized star.

Betelgeuse Stars can live for billions of years. A star is born when an enormous cloud of hydrogen gas collapses until it is hot enough to burn nuclear fuel (producing tremendous amounts heat and radiation). As the nuclear fuel runs out (in about 5 billion years), the star expands and the core contracts, becoming a giant star which eventually explodes and turns into a dim, cool object (a black dwarf, neutron star, or black hole, depending on its initial mass). The largest stars have the shortest life span (still billions of years); more massive stars burn hotter and faster than their smaller counterparts (like the Sun).

The composition of stars is studied using spectroscopy in which their visible light (the spectrum) is studied.

Group of stars

Double star animation In the universe, most stars occur in groups of at least two stars. Two stars that are locked in elliptical orbit around their center of mass (their barycenter) are called a binary star system. About half of all stars are in a binary star system.

A globular cluster

A globular star cluster is a spherical group of up to a million stars held together by gravity. These remote objects lie mostly around the central bulge of spiral galaxies.

There are larger groups of stars, called clusters. These are relatively unorganized collections of stars. An open cluster is a loose collection of up to about 1,000 stars. Examples of open clusters include the Pleiades and Hyades.

Huge, organized collections of stars are called galaxies. Our solar system is located in the Milky Way Galaxy, a spiral galaxy. For more in-depth information on galaxies, click here.

All groups of stars are held together by gravitational forces.

Why are stars hot and bright?

Nuclear fusion and nucleosynthesis

Stars are giant nuclear reactors. In the center of stars, atoms are taken apart by tremendous atomic collisions that alter the atomic structure and release an enormous amount of energy. This makes stars hot and bright. In most stars, the primary reaction converts hydrogen atoms into helium atoms, releasing an enormous amount of energy. This reaction is called nuclear fusion because it fused the nuclei (center) of atoms together, forming a new nucleus. The process of forming a new nucleus (and element) is nucleosynthesis.

For more information on nuclear fusion in stars, click here.

What is the closest star?

The closest star to us is the sun! Other than that, the closest star is Proxima Centauri, aka Alpha Centauri C (the dimmest star in the Alpha Centauri system). Proxima Centauri is 4.3 light-years from the Sun. It has an absolute magnitude of 15.5.

Why do stars twinkle?

Star twinkle diagram The scientific name for the twinkling of stars is stellar scintillation (or astronomical scintillation). Stars twinkle when we see them from the Earth’s surface because we are viewing them through thick layers of turbulent (moving) air in the Earth’s atmosphere.

Stars (except for the Sun) appear as tiny dots in the sky; as their light travels through the many layers of the Earth’s atmosphere, the light of the star is bent (refracted) many times and in random directions (light is bent when it hits a change in density - like a pocket of cold air or hot air). This random refraction results in the star winking out (it looks as though the star moves a bit, and our eye interprets this as twinkling).

Stars closer to the horizon appear to twinkle more than stars that are overhead - this is because the light of stars near the horizon has to travel through more air than stars overhead and subject to more refraction. Also, planets do not usually twinkle - they are big enough that this effect is not noticeable (except when the air is extremely turbulent).

Stars would not appear to twinkle if we viewed them from outer space (or from a planet/moon that didn’t have an atmosphere).

Stellar wind

Stellar wind is ionized gas that is ejected from the surface of a star (including the Sun). Older (evolved) stars give off stronger stellar winds than younger stars.

Other Links:
Estimated Grade Level
Our subscribers' grade-level estimate for this page:
4th
You Might Also Like:
Stars Quiz
Activities: The Stars
Star Classification - Types of Stars
Birth of Stars - Astronomy
Major Stars and Star Systems
Stars
The Stars
Lifecycle
Birth
Death
Nuclear Fusion
Star Types
Brightest Stars
Closest Stars
Galaxies
Nebulae
Other Solar Systems
Major Stars
Constellations
The Zodiac
Why Stars Twinkle
Activities & Links
Zoom Astronomy
— All About Astronomy —
Table of Contents
Index
More on Astronomy
Stars
Our Solar System
Astronomy Glossary
Hall of Astronomers
Printables, Worksheets, and Activities
Advertisement.
▾ See more
Site Overview
What's New
Enchanted Learning Home
Monthly Activity Calendar
Books to Print
Site Index
Enchanted Blog
K-3
Crafts
K-3 Themes
Little Explorers
Picture Dictionary
PreK/K Activities
Rebus Rhymes
Stories
Writing
Cloze Activities
Essay Topics
Newspaper
Writing Activities
Parts of Speech
Fiction
The Test of Time
Biology
Animal Printouts
Biology Label Printouts
Biomes
Birds
Butterflies
Dinosaurs
Biology Continued
Food Chain
Human Anatomy
Mammals
Plants
Rainforests
Sharks
Whales
Physical Sciences: K-12
Astronomy
The Earth
Geology
Hurricanes
Landforms
Oceans
Tsunami
Volcano
Languages
Dutch
French
German
Italian
Japanese (Romaji)
Portuguese
Spanish
Swedish
Geography/History
Explorers
Flags
Geography
Inventors
US History
Other Topics
Arts and Artists
Calendars
College Finder
Crafts
Graphic Organizers
Label Me! Printouts
Math
Music
Word Wheels
Copyright © 2000-2025 EnchantedLearning.com
How to cite a web page
-
Our Privacy Policy
-
Site Index
-
Contact Us
-
About Us
-
Subscribe
Advertisement.
Advertisement.