Easy Science

If it's time for a meteor shower, you won't need a telescope, binoculars, or a high mountain to have a "star gazing" party. You might need a warm sleeping bag and an alarm clock to wake you in the middle of the night. But then just lying down in your own back yard will put you in the perfect spot to enjoy a great show. What is a meteor shower? A meteor is a space rock—or meteoroid—that enters Earth's atmosphere. As the space rock falls toward Earth, the resistance—or drag—of the air on the rock makes it extremely hot. What we see is a "shooting star." That bright streak is not actually the rock, but rather the glowing hot air as the hot rock zips through the atmosphere. When Earth encounters many meteoroids at once, we call it a meteor shower. Why would Earth encounter many meteoroids at once? Well, comets, like Earth and the other planets, also orbit the sun. Unlike the nearly circular orbits of the planets, the orbits of comets are usuall

Asteroids are small, rocky objects that orbit the sun. Although asteroids orbit the sun like planets, they are much smaller than planets. A close-up image of the asteroid Ida taken by NASA's Galileo spacecraft. There are lots of asteroids in our solar system. Most of them live in the main  asteroid belt —a region between the orbits of Mars and Jupiter. Most asteroids in our solar system can be found in the asteroid belt, between Mars and Jupiter. Asteroids hang out in other places, too. For example, some asteroids are found in the orbital path of planets. This means that the asteroid and the planet follow the same path around the sun. Earth and a few other planets have asteroids like this. Where did asteroids come from? Asteroids are left over from the formation of our solar system. Our solar system began about 4.6 billion years ago when a big cloud of gas and dust collapsed. When this happened, most of the material fell to the center of the cloud and formed the s

A  supernova  is the biggest explosion that humans have ever seen. Each blast is the extremely bright, super-powerful explosion of a star. An illustration of one of the brightest and most energetic supernova explosions ever recorded .  What causes a supernova? One type of supernova is caused by the “last hurrah” of a dying massive star. This happens when a star at least five times the mass of our sun goes out with a fantastic bang! Massive stars burn huge amounts of nuclear fuel at their  cores , or centers. This produces  tons of energy , so the center gets very hot. Heat generates pressure, and the pressure created by a star’s nuclear burning also keeps that star from collapsing. A star is in balance between two opposite forces. The star’s gravity tries to squeeze the star into the smallest, tightest ball possible. But the nuclear fuel burning in the star’s core creates strong outward pressure. This outward push resists the inward squeeze of gravity. What holds stars t

We live on a planet called Earth that is part of our solar system. But where is our solar system? It’s a small part of the Milky Way Galaxy. A  galaxy  is a huge collection of gas, dust, and  billions  of stars and their solar systems. A galaxy is held together by gravity. Our galaxy, the Milky Way, also has a  supermassive black hole  in the middle.   When you look up at stars in the night sky, you’re seeing other stars in the Milky Way. If it’s really dark, far away from lights from cities and houses, you can even see the dusty bands of the Milky Way stretch across the sky. There are many galaxies besides ours, though. There are so many, we can’t even count them all yet! The  Hubble Space Telescope  looked at a small patch of space for 12 days and found 10,000 galaxies, of all sizes, shapes, and colors. Some scientists think there could be as many as  one hundred billion galaxies in the universe. Some galaxies are spiral-shaped like ours. They have curved arms that ma

What causes the seasons? It's all about Earth's tilt! Many people believe that Earth is closer to the sun in the summer and that is why it is hotter. And, likewise, they think Earth is farthest from the sun in the winter. Although this idea makes sense, it is  incorrect. It is true that Earth’s orbit is not a perfect circle. It is a bit lop-sided. During part of the year, Earth is closer to the sun than at other times. However, in the Northern Hemisphere, we are having winter when Earth is closest to the sun and summer when it is farthest away! Compared with how far away the sun is, this change in Earth's distance throughout the year does not make much difference to our weather. There is a different reason for Earth's seasons. Earth's axis is an imaginary pole going right through the center of Earth from "top" to "bottom." Earth spins around this pole, making one complete turn each day. That is why we have day and night, and why e

Constellations and their symbols Some curious symbols ring the outside of the  Star Finder . These symbols stand for some of the constellations in the zodiac. What is the zodiac and what is special about these constellations? Imagine a straight line drawn from Earth through the Sun and out into space way beyond our solar system where the stars are. Then, picture Earth following its orbit around the Sun. This imaginary line would rotate, pointing to different stars throughout one complete trip around the Sun—or, one year. All the stars that lie close to the imaginary flat disk swept out by this imaginary line are said to be in the zodiac. The constellations in the zodiac are simply the constellations that this imaginary straight line points to in its year-long journey. A long history of looking to the stars In ancient times, astronomers did not fully understand how Earth, the Sun, and the stars moved. Nor did they have any idea the Universe is so vast. But they were keen ob