NASA/ESA Hubble Space Telescope image of NGC 2336, a typical spiral galaxy like our own Milky Way. (dimazel - stock.adobe.com)
It is sometimes hard to imagine how large space is outside of our home planet, Earth. Scientists call space and everything in it the universe. It is mostly the empty, inky blackness you see when you look at the night sky. But there are pockets of energy and material that are pulled together with gravity. These are galaxies.
We live on the outer part of the Milky Way Galaxy. When you see the Milky Way in the night sky you are looking toward the center of the galaxy. It seems like a fuzzy, milky-white trail. The galaxy is really a pretty spiral of stars, gas clouds, dust and planets. All of those things flow around the Sagittarius A-star (or A*), a black hole at the very center. Black holes are places where gravity is extremely strong, which helps galaxies form around them.
There are about 100 billion stars in the Milky Way galaxy, and our sun is one of them! Earth is part of a solar system. That means our planet travels in a massive oval path around the sun. This is called our orbit. Plenty of other things orbit our sun, too.
Our Solar System (shooarts - stock.adobe.com)
Nearest the sun are four rocky planets.
Mercury
Venus
Earth
Mars
Next there is an asteroid belt made of rocks and one tiny dwarf planet called Ceres.
Further away are two gas giants, which have no surface to land on.
Jupiter
Saturn
Next there are two ice giants, mostly made up of freezing liquids.
Uranus
Neptune
Beyond all the planets is the Kuiper Belt. It is an area made up of icy items and frozen rocks. Scientists call these KBOs, or Kuiper Belt Objects. Some, like Pluto and Eris are big enough to be called dwarf planets.
At the center of our solar system is our star, the sun. It gives us heat and light and helps life to form on Earth. The sun is mostly made of hydrogen and helium that are constantly reacting with each other to generate energy.
Sometimes particles of energy are blown from the sun into space. This is called solar wind. When it gets to Earth, our atmosphere acts like a force field to block it. Sometimes we can see this happen. It makes greenish waves in the sky called the aurora.
The Earth rotates on a tilt that doesn’t change direction as it goes around the sun. The northern part of the Earth is tilted away from the sun in winter. This means that in Europe we get less of the sun’s energy, which gives us wintry weather. At the same time, the southern part of the Earth is tilted toward the sun, so people who live there get summer. Once Earth moves to the other side of its orbit, the opposite is true. When the north tilts toward the sun, we get summer in Europe.
Did you know? During the winter in Europe we are closer to sun than we are in summer. That is because our orbit is an oval.
Earth’s seasons and solstices happen because of our tilt and orbit around the sun. (yusufdemirci - stock.adobe.com)
SOLSTICE and EQUINOX
One whole day on Earth lasts 24 hours. That is how long it takes our planet to rotate, or spin around one time. The amount of daylight and nighttime we get depends on how the Earth rotates on a tilt.
(again, the following may be best placed on a diagram)
In winter, when Europe is tilted away from the sun, we get very long nights. The day with the longest nighttime is called the winter solstice and it happens on December 21.
The opposite is true in the summer when Europe tilts toward the sun. The day with the longest sunlight is called the summer solstice on June 21.
There are two days between the solstices that have an equal 12 hours of sunlight and nighttime. These equinoxes happen on March 20 and September 22.
Visit spaceplace.nasa.gov to learn more about space!
