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Use these links (by clicking on the box) to visit websites and learn about ONE constellation that you like! When you are finished researching, go back to Google Classroom and answer the posted question.

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What?! Stars have personalities! What does that even mean?

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Star Personalities: Crash Course Kids #25.2

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Learn about how a star is born , what light years are, and why stars are different colors.

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A star is a massive ball of plasma (very hot gas) held together by gravity. It radiates energy because of the nuclear reactions inside it

It radiates heat and light, and every other part of the electromagnetic spectrum, such as radio waves, micro-waves, X-rays, gamma-rays and ultra-violet radiation. The proportions vary according to the mass and age of the star.

The energy of stars comes from nuclear fusion. This is a process that turns a light chemical element into another heavier element. Stars are mostly made of hydrogen and helium. They turn the hydrogen into helium by fusion. When a star is near the end of its life, it begins to change the helium into other heavier chemical elements, like carbon and oxygen. Fusion produces a lot of energy. The energy makes the star very hot. The energy produced by stars radiates away from them. The energy leaves as electromagnetic radiation.

Birth of a star

A star begins as a collapsing cloud of material made mostly of hydrogen, with helium and tiny amounts of heavier elements. Once the stellar core is dense enough, some of the hydrogen is changed into helium through nuclear fusion. The energy moves away from the core by a combination of radiation and convection. The star's radiation stops it from collapsing further under its own gravity. Once the hydrogen fuel at the core has been used up, those stars with at least 0.4 times the mass of the Sun expand to become a red giant. In some cases they fuse heavier elements. When the star is very old it might expand until its outer layers are pushed away. If the star is heavier, it might explode and spread most of its mass into space. The matter it spreads into space may make a new generation of stars. If the star is even larger it may collapse and form a black hole.

Earth and Sun

The star nearest to Earth is the Sun. It is not accurate to say "most of the energy on Earth comes from it". It is more accurate to say the energy of sunlight supports almost all life on Earth by photosynthesis, and drives Earth's climate and weather. The Earth has its own source of heat in its interior: see Age of the Earth. The internal heat comes from the original gravitational formation of the Earth, and from the radioactive materials inside it.

We can see other stars in the night sky when the Sun goes down. They are made mostly of hydrogen and a little bit of helium plus other elements. The sun is such a star.

Most stars look like shiny dots from Earth, because they are far away. Our Sun is the closest star to us. The earth and other planets move around () the Sun. The Sun and all things that orbit it are called the Solar System. Many other stars have planets orbiting them: they are called exoplanets.

Numbers, distances

The nearest star to our Solar System, and the second nearest star to Earth after the Sun, is Proxima Centauri. It is 39.9 trillion kilometres away. This is 4.2 light years away, meaning that light from Proxima Centauri takes 4.2 years to reach Earth.

Astronomers think there are a very large number of stars in the Universe. They estimate (guess) that there are at least 70 sextillion stars. That is 70,000,000,000,000,000,000,000; which is about 230 billion times the number of stars in the Milky Way (our galaxy).

Most stars are very old. They are usually thought to be between 1 and 10 billion years old. The oldest stars are thought to be around 13.7 billion years old. Scientists think that is close to the age of the Universe.

Stars vary greatly in size. The smallest neutron stars (which are actually dead stars) are no bigger than a city. The neutron star is incredibly dense. If you were to take a layer a micrometre thick and apply it onto a tank, it would be a very tough armor. The tank would be so heavy, it would sink into the center of the Earth.

Hypergiant stars are the largest stars in the Universe. They have a diameter over 1,500 times bigger than the Sun. If you changed the sun into one of these huge stars down where the sun is, its outer surface would reach beyond the orbit of Jupiter, and the earth would be well inside the star. The star Betelgeuse, in the Orion constellation is a red supergiant star.

When seen in the night sky without a telescope, some stars appear brighter than other stars. This difference is measured in terms of apparent magnitude. There are two reasons for stars to differ in apparent magnitude. If one star is much closer than another otherwise similar star, it will appear much brighter, in just the same way that a candle that is near looks brighter than a big fire that is far away. If one star is much larger or much hotter than another star at about the same distance, it will appear much brighter, in just the same way that if two fires are the same distance away, the bigger or hotter one will look brighter. A star's true luminosity is its absolute magnitude.

Beside light, stars also give off a solar wind and neutrinos. These are very small particles.

Stars are a source of a gravity field. This is what keeps planets close to them. It is also not unusual for two stars to orbit each other. This happens when they are close together. This is also because of gravity, in the same way as the Earth orbits the Sun. These binary stars (binary meaning "two") are thought to be very common. There are even groups of three or more stars orbiting each other. Proxima Centauri is the smallest star in a group of three.

Stars are not spread evenly across all of space. They are grouped into galaxies. A typical galaxy contains hundreds of billions of stars.

History of seeing stars

Stars have been important to people all over the world for all of history. Stars have been part of religious practices. Long ago, people believed that stars could never die. Astronomers organized stars into groups called constellations. They used the constellations to help them see the motion of the planets and to guess the position of the Sun. The motion of the Sun and the stars was used to make calendars. The calendars were used by farmers to decide when to plant crops and when to harvest them.

The life of stars

Stars are made in nebulas. These are areas that have more gas than normal space. The gas in a nebula is collected by gravity. The Orion nebula is an example of a place where gas is coming together to form stars.

Stars spend most of their lives burning ( fusing) hydrogen to make energy. When hydrogen is fused it makes helium. To fuse hydrogen it must be very hot and the pressure must be very high. Fusion happens at the center of stars, called "the core".

The smallest stars ( red dwarfs) fuse their hydrogen slowly and live for 100 billion years. Red dwarfs live longer than any other type of star. At the end of their lives, they become dimmer and dimmer. Red dwarfs do not explode.

When very heavy stars die, they explode. This is called a supernova. When a supernova happens in a nebula, the explosion pushes the gas in the nebula together. This makes the gas in the nebula very thick. Gravity and exploding stars both help to make new stars in nebulas.

Most stars use up the hydrogen at their core. When they do, their core shrinks and becomes very hot. It becomes so hot it pushes away the outer layer of the star. As the outer layer expands it makes a red giant star. Astro-physicists think that in about 5 billion years, the sun will be a red giant. Our sun will be so large it will eat the Earth. After our sun stops using hydrogen to make energy, it will use helium in its very hot core. It will be hotter than when it was fusing hydrogen. Heavy stars will also make elements heavier than helium. As a star makes heavier and heavier elements, it makes less and less energy. Elements as heavy as iron are made in heavy stars.

Average stars (like our sun) will push away their outer gases. The gas it pushes away makes a cloud called a planetary nebula. The core part of the star will remain. It will be a ball as big as the Earth and called a white dwarf. It will fade into a black dwarf over a very long time.

Later in large stars, heavier elements are made by fusion. Finally the star makes a supernova explosion. Most things happen in the universe so slowly we do not notice. But supernova explosions happen in only 100 seconds. When a supernovae explodes its flash is as bright as a 100 billion stars. The dying star is so bright it can be seen during the day. Supernova means "new star" because people used to think it was the beginning of a new star. Today we know that a supernova is the death of an old star. The gas of the star is pushed away by the explosion. It forms a giant cloud of gas called a planetary nebula. The crab nebula is a good example. All that remains is a neutron star. If the star was very heavy, the star will make a black hole. Gravity in a black hole is extremely strong. It is so strong that even light cannot escape from a black hole.

The heaviest elements are made in the explosion of a supernova. After billions of years of floating in space, the gas and dust come together to make new stars and new planets. Much of the gas and dust in space comes from supernovae. Our Sun, the Earth, and all living things are made from star dust.

Astronomers have known for centuries that stars have different colors. When looking at an electromagnetic spectrum, ultraviolet waves are the shortest, and infrared are the longest. The visible spectrum has wavelengths between these two extremes.

Modern instruments can measure very precisely the color of a star. This allows astronomers to determine that star's temperature, because a hotter star's black-body radiation has shorter wavelengths. The hottest stars are blue and violet, then white, then yellow, and the coolest are red. Knowing the color and absolute magnitude, astronomers can place the star on the Hertzsprung-Russell diagram, and estimate its habitable zone and other facts about it.

For example, our Sun is white, and the Earth is the perfect distance away for life. If our Sun was a hotter, blue star, however, Earth would have to be much farther away or else it would be too hot to have water and sustain life.

Images for kids

In Spanish: Estrella para niños

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Why are the constellations moving in the night sky? The position of the Earth matters!

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Constellation Location: Crash Course Kids #31.2

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Here are some fun facts about the Big Dipper!

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Kids who love to stargaze are probably familiar with the most identifiable star configuration in the night sky -- the Big Dipper. It's easy to find and instantly recognizable thanks to its long "handle" and large "bowl." Over the centuries, the Big Dipper has developed a rich mythology.

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Looking for more specific information about a constellation? This is a great website!

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Looking to learn more about constellations for kids? Improve your knowledge on stars and constellations and find out more about space with DK Find Out.

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This is a simple website that will give you general information about constellations. See if your favorite constellation is one here!

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Astronomy for Kids is an astronomy site designed with kids in mind, as well as their parents

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If you're not sure what a constellation is, this is a great place to start!

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Orion

Orion is one of the most visible constellations. Because of its location, it can be seen throughout the world. Orion is named after a hunter from Greek mythology. Its brightest stars are Betelgeuse and Rigel.

Constellation Orion

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Kids learn about the constellations in the science of astronomy. These stars that form patterns when viewed from the Earth have been studied since ancient times.

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Here is another website to use for general research!

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The official definition of a constellation is an area of the sky with defined boundaries, all stars and any other objects within that boundary are considered part of the constellation.

Historically and in common language stars that form patterns in the night sky are also referred to as constellations.

In modern scientific language stars that form patterns are known as asterisms, asterisms usually fall within a single constellation and bare the same name but they can also be part of multiple constellations.

There are 88 official constellations which are recognized by the International Astronomical Union.

Some constellations are only visible in the northern hemisphere, while others are only visible in the southern hemisphere.

Constellations that are visible in both hemispheres may appear upside down in the southern hemisphere.

A few constellations can be viewed all year long but most are seasonal and can only be viewed at certain times of the year.

Distant galaxies and nebulae also form parts of constellations.

The sun is the only known star in our galaxy which is not part of a constellation.

History of Constellations

For as long as mankind has walked the Earth it is likely we have always recognized patterns formed by stars in the night sky. Some European cave paintings that date back over 10,000 years bare the marks of star formations that are familiar to us even to this day. The earliest official records of constellations were made more than 3,000 years ago by the Babylonians, an ancient civilization based in what is now modern day Iraq. The twelve signs of the zodiac are based on their observations and those of their predecessors.

In the 4th century BC these zodiacal constellations and others recorded by the Babylonians were introduced into ancient Greek culture by the astronomer Eudoxus of Cnidus. Some five hundred years later the Greco-Roman scientist Claudius Ptolemy listed 48 constellations in his book Almagest, these constellations and the names he gave them exist to this day and are the basis for all the 88 official constellations listed by the International Astronomical Union.

Understanding Star Charts

To find constellations you'll need a star chart, these give you a snapshot of what the night sky will look like at any one time and at any one location. The star chart above shows you how the night sky will look above most of the United States at 8 pm in late January. These maps may seem rather baffling and confusing at first but they're actually very simple to use. To simplify matters the chart above only shows constellations but normally they will also indicate prominent stars, galaxies, nebulae and planets.

The first thing you may notice is that east and west seem to be the wrong way round, but if you imagine holding the chart above your head, which is how they are designed to be used, it becomes apparent this is not the case. The outer edge of the chart indicates the horizon, so the further the stars are from the edge the higher they will be in the sky.

The center of the chart shows the stars and constellations that will be directly overhead, so the map above shows you that the constellations of Auriga, Taurus and Perseus will be directly above you at that time.

To find your bearings it is helpful to find Polaris, the star which always points north. First find the famous Big Dipper, which is part of the constellation Ursa Major and visible all year in the Northern hemisphere, draw an imaginary line through the outer two stars of the Big Dipper's bowl and you will come to Polaris, which is the brightest star in the constellation of Ursa Minor. In the Southern hemisphere it is helpful to find the Southern Cross, which always points south, this is done by drawing a line through the bright stars Alpha and Beta Centauri.

Once you have found your bearings you can start searching out constellations and the objects they contain. Using the chart above if you look south you'll notice the constellation of Orion, perhaps the most recognizable constellation of them all. As well as the Orion nebula the constellation also contains the bright supergiant stars Betelgeuse and Rigel. Overhead and to the west you'll find the Andromeda constellation which contains the Andromeda Galaxy, the most distant object that can be viewed with the naked eye. There are many other fascinating objects to look out for and a star chart will be essential in guiding you around the night sky.

Stars do not stay fixed in the night sky, as the Earth rotates they change position, as a result the night sky will look different at midnight from what it did several hours before or after. Most constellations are also seasonal, meaning that ones that are visible in winter may not be visible in summer and vice-versa, so sky charts usually come in seasonal versions. Constellations may also be drawn slightly differently on each chart and it's also worth noting that there are separate charts for the Northern and Southern hemispheres.

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Star Constellations - Facts About Constellations | Solarsystemquick.com

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Find out what exactly a star constellation is and how many there are. Information on how to understand and use star charts to discover those fascinating objects in the night sky. How the constellations got their names and the history behind them.

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Check out this live map to see where constellations are right now in the sky!

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An online sky map, easy to use to identify stars and planets

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Ready to test your constellation knowledge? Check out this 10 question quiz!