1. Do stars have points?

No. Stars are huge, round balls of hot, glowing gas. They seem pointy to us because we see them through the moving layers of air and dust that surround Earth. The moving layers bend and break the starlight, making the stars look pointy.

The next time you take a bath or go swimming, look at your feet, Notice how the moving water breaks up the light and changes the shape of your toes. It’s like the moving layers of air scattering the light from the stars.

Earth and the moon

2. How many stars can you see on a dark, clear night?

You can see about 3000 stars with your eyes alone. But keep in mind that you are viewing only part of the sky. If the whole sky were visible, you could count about 5000 stars.

If you look through a small telescope you might see as many as 600000 stars. Through the most powerful telescope astronomers can spot millions of stars. No one is sure exactly how many stars there are altogether. But astronomers believe there are at least 200 billion stars out in space!

Starry sky

3. Which is the brightest star in the night sky?

Sirius(SIHR-ee-us), sometimes called the Dog star, is the brightest star that we can see. Although it is about the same size as the sun. Sirius is nearly 30 times brighter. Astronomers call it a star of the first magnitude– a measure of a star’s brightness.

Learn more about the Dog Star

4. What are stars made of?

The stars are mostly hot gases. The chief gas is hydrogen(HYE-druh-juhn). Hydrogen gas consists of tiny bits called atoms. The heat inside the stars makes the hydrogen atoms jump about. They keep on bumping into one another. Sometimes two hydrogen atoms bump so hard that they join together. The process is called nuclear fission. This produces a tiny flash of light and a small burst of heat.

All of these collisions add up. Inside every star, hundreds of millions of hydrogen atoms are joining together very second. The collisions shoot billions of flashes of light and burst of heat out into space at the same time. And the collisions go on and on.

Milky way

5. Where did the stars come from?

Astronomers think they know. Long, long ago, everything in the entire universe was scrunched tightly together into a small ball. Then about 13 billion years ago, there was a huge explosion. Scientists call the explosion the Big Bang. They believe that the Big Bang was the birth of the universe.

The Big Bang send gas and dust flying into space. The gas and dust were made up of tiny bits of many different chemicals. Slowly they came together in giant clouds. Gravity pulled the clouds in together, tighter and tighter, the force of gravity shaped the clouds into immense spheres.

At first, each sphere stretched across about 10 trillion miles. Over millions of years, the spheres grew smaller and smaller. In time they were a million miles across. And that’s when the first stars were born!

Galaxy

6. How did the solar system form?

Most scientists think the sun and planets were formed from a giant cloud of gas and dust about 5 billion years ago. The force of gravity pulled most of the gas and dust towards the center. This large mass became the sun. But clouds of gas and dust were left over. They continued to fly around the sun. Eventually, these clouds pulled together into much smaller balls that became the planets.

Nature of space

7. Are new stars forming today?

Yes. Plenty of gas and dust is still floating around in space. Some of it is left over form the Big Bang. Some comes from old stars that have exploded, hurling huge amounts of gas and dust out into space.

A new star begins when the clouds of gas and dust come together. When they get small enough, the gas gets hotter and hotter. The atoms bump and stick together, sending out tremendous amounts of heat and light. And new stars are created, just like the stars that formed after the Big Bang.

galaxy
galaxy

8. Do old stars die?

Indeed they do. Over billions of years, stars use up their hydrogen and get smaller. Some stars shrink and became so tiny that they are called white dwarfs. White dwarfs are very heavy. A teaspoon of a white dwarf weighs about 1,000 tons.

Sometimes the white dwarf suddenly becomes much brighter. It turns into a nova. Sometimes the star explodes and is completely destroyed. Then it’s called a supernova. The light from a supernova is a million times brighter than the light form a nova

Stars may also shrink until they are only a few miles across. Then they become black holes. The pull of gravity in a black hole is super powerful. It is so strong that it does not even let light escape. Without light, the star is completely dark in the sky.

Sun

9. Which star is closest to Earth?

The sun. It is about 93 million miles form us. That makes it close enough to look like a round ball instead of speck of starlight. It is also close enough for us to feel its tremendous heat and get its powerful light.

But don’t think it’s a quick trip to the sun. A car going 60 miles an hour would reach the sun in 177 years. At 25000 miles an hour, it would take a rocket more than five months to cover the distance. Light form the sun, which spreads along at an incredible 186000 miles per second, takes just over eight minutes to reach Earth!

Eclipse

10. How hot is the sun?

Hotter than anything on Earth! The surface of the sun is about 10000 degrees Fahrenheit(5532 *C). The inside of the sun is even hotter. It’s about 27 million degrees. Compare that to a gas kitchen stove, which only reach 1000 degrees. Only as small part of the sun’s heat and light energy reaches earth. Yet life on Earth depends on this energy. Plants need it to grow. Some animals eat the plants. Others eat the plant-eating animals. Life on Earth would be impossible without energy form the sun.

Bonus : How do astronomers take a star’s temperature?

They look as its color. As you know , things change color with heat. A piece of metal may be black. Heat it, and the metal becomes red hot. Make it even hotter, and it turns white hot.

A star’s color tells the temperature at its surface. Red stars are coolest at about 5000 degree Fahrenheit. Blue white stars are hottest. They can reach 50000 degrees. The sun, a yellow star, is in between–10000 degrees Fahrenheit.

Astronomers also take a star’s surface temperature by passing its light through a special glass called a prism. The prism breaks the light up into a series of colored lines. Form these lines, scientists can find the star’s exact temperature.

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