Many years ago, people looked up at the stars and could see the enormous swath of stars that kind of looked like a white band across the night sky. This band of stars is our galaxy. People thought that the band of stars looked like a river of milk, and so they named the galaxy that we live in the Milky Way.
Earth is hit with more than 100 tons of space rock every day.
Some of the moons that orbit some of the planets in our solar system are not round or spherical in shape like the Earth’s moon. Some moons have very irregular, oblong, lumpy shapes.
In the northern hemisphere, the best time to see the Milky Way is in the summer. The center of the Milky Way is about at the location of the constellation, Sagittarius. You can see the Milky Way in the winter, but it is much dimmer, and you can mostly only see the outer rim of the galaxy.
Since the earth orbits the Sun, part of the year it is on one side of the Sun, and the other part of the year, it is on the other side of the Sun. Because of this, we see different stars at different times of the year.
The Sun is 93 million miles away from the earth. The next closest star to the earth is 24 trillion miles away.
Giant clouds of gas and dust in our galaxy are called nebulas.
More than 99% of our solar system’s mass is in the Sun.
Astronomers estimate that the Milky Way has between 200 and 400 billion stars.
Earth is the only planet in our solar system that is not named after a person in Greek or Roman mythology.
Even though we can easily see the planets Venus and Mars in the night sky, they are very different from the stars that we see. Stars have their own light. Planets have no light of their own. So even though Venus and Mars look bright and shining, they are just reflecting the light of the Sun.
It can be hard for astronomers to study the Milky Way because our planet Earth is inside of the Milky Way. It’s difficult to study or understand the “big picture” of the galaxy when it can only be viewed from inside it. It’s kind of like standing in one spot in a large city and trying to understand what that big city is like just from the perspective of the small spot where you are standing.
Sunspots are dark blotches on the surface of the Sun that are slightly cooler than the rest of the Sun. Sunspots have strong magnetic fields. Even though sunspots may look very small on the surface of the Sun, they are actually enormous. One single sunspot is usually many times wider than the Earth.
Astronomers use light years to measure distances in space. A light year is the distance light travels in one year. In a year, light travels about 6 trillion miles.
Stars are made of gasses such as helium and hydrogen. On our Sun (which is a star) the helium and hydrogen react with each other and cause small nuclear reactions. These reactions create energy which is why our Sun gives off heat and light.
In Roman times, the Moon was called luna. We still use this Latin term when we refer to thing about the Moon as lunar.
Astronomers study other galaxies in addition to our own Milky Way galaxy. These other galaxies are millions of light years away from the Earth. Because it takes millions of years for the light from other galaxies to reach the Earth, when astronomers view these galaxies with high-powered telescopes, they are actually viewing the galaxies as they were millions or billions of years ago.
It takes 24 hours for the earth to rotate on its axis one time.
The Apollo missions were designed to help the United States learn about the moon.
Apollo 7 and Apollo 9
These missions had astronauts fly around the earth in order to test equipment.
Apollo 8 and Apollo 10
These missions flew around the moon but did not land.
Apollo 11, 12, 14, 15, 16, and 17
These missions all landed on the moon. In the Apollo 11, 12, and 14 missions, the astronauts stayed very close to the landing sites and just studied the moon areas close to their landing modules. The Apollo 15, 16, and 17 missions used land rovers which were electric buggies that allowed them to travel farther on the moon and study more areas.
This mission was supposed to land on the moon but had problems with it spacecraft and had to make an emergency flight back to earth.
We all know that Mars is called the red planet because of the large amounts of iron in its soil which rusts and looks reddish. But did you know that the sky on Mars is a pink color because of the rusty dust?
Besides stars, planets, asteroids, and dust, our galaxy contains enormous amounts of dark matter. Dark matter does not glow, and so it can’t be seen. Dark matter’s gravity helps to hold everything in our galaxy together.
Astronomers think that most short-period comets come from the Kuiper Belt, an area of our solar system out past Neptune. If a comet is short-period, it takes less than 200 years to orbit the Sun. Long-period comets are thought to come from the Oort Cloud which is in the farthest part of our solar system. If a comet is long-period, it takes more than 200 years to orbit the Sun.
Our galaxy, the Milky Way, travels through space about 366 miles per second. In one year, the Milky Way moves about 11 billion miles through space.
The moon has many craters on it. They have been formed as asteroids have hit the moon.
A black hole has extra strong gravity. The gravity is so strong that it pulls dust, stars, and even light into it.
The same side of the moon always faces the earth. The first time that scientists were ever able to see the other side of the moon was in 1959 when a space probe called Luna 3 flew around the moon and took pictures.
Nebulas are enormous clouds of gas and dust. The gasses in nebulas form into stars.
Astronauts who visited the moon brought back about 840 pounds of moon rocks and soil to study.
It is very dangerous for astronauts to “walk in space”. Astronauts on the International Space Station occasionally have to wear special space suits and go outside of the space station to do repairs. Space debris is a particular danger to them because of the orbital velocity of objects travelling in space. A grain of sand in outer space would be travelling at the speed of a bullet and could puncture the space suit of an astronaut.
Our Sun is a medium-sized dwarf star.
Planets can be classified into what they are made up of. There are planets that are mostly made from rock—Mercury, Venus, Earth, Mars---and these are often called the inner planets or rocky planets. There are planets that are mostly made of gas---Jupiter, Saturn, Neptune, Uranus--and these are often called the outer planets or gas giants.
Soil on the moon is called regolith. Regolith has been formed when asteroids have hit the moon and broken moon rocks into tiny particles.
Because the moon has no atmosphere, there is no air or wind or weather on the moon.
Stars come in different sizes and colors. The biggest stars are red. Medium-sized stars are bluish in color. The smallest size stars are white. Our Sun is a yellow star. The color of stars relates to their temperatures. Even though red stars are large, they are only about half as hot as our yellow Sun. White and blue stars are 5-10 times hotter than our yellow Sun.
Imaginary lines drawn between groups of stars to form pictures, figures, shapes are called constellations. There are 88 constellations that can be seen from different places on the Earth.
Dark patches on the moon are called maria which is the Latin word for seas. People many, many years ago thought that the patches were oceans, and so they named the patches maria.
The Milky Way is part of a group of 50 nearby galaxies that scientists call “the local group”. The biggest galaxy in the local group is the Andromeda Galaxy, and it is about 2.5 times larger than the Milky Way.
There are lots of man-made objects floating around in our solar system! Scientists estimate that there are more than 8,000 objects such as satellites, pieces of old spacecraft, and even things that astronauts have dropped floating around.
The moon has no atmosphere. As a result, the moon has no weather. If you stood on the moon, the sky would always be black because there is no atmosphere. There is also no sound on the moon because sound is carried through substances like air.
The very first satellite that was ever launched was called Sputnik 1. It was launched by the Soviet Union in 1957, and it orbited the earth in 98 minutes. About a month later, the Soviet Union launched Sputnik 2, and it had a dog named Laika on board.