This section tests your knowledge on Earth and our universe as a whole, tectonic plates and their interactions, natural hazards, resources, and weather/climate.
Here are some specific concepts that will more than likely appear on the test.
By definition, stars are huge spheres of gas. Created by nuclear fusion, stars are held together by their own gravity. Our galaxy, the Milky Way, contains billions of stars. The Sun, a G2 yellow dwarf star, is the closest star to Earth.
Astronomers classify stars based on their properties. Three important properties include color, size, and luminosity. Let’s review each property.
A star gets its color based on its surface temperature. Red dwarf stars are the coolest in our universe. Blue stars burn the hottest. Our star, the Sun, is a G star that is classified as ‘white’, even though it gives off a yellowish glow. It falls in the middle in regard to surface temperature.
Just as stars come in a variety of colors, they also come in various sizes. Small neutron stars are sometimes as small as 30 km (around 18 miles) in diameter.
Stars tend to grow in size as they grow in mass. Large gas giants can be over 1,500 times larger. The Sun is 695,000 kilometers (431,852 miles) in diameter. That sounds huge, right? When compared to the red giant, Betelgeuse, our own star is a 1,000 times smaller.
Also known as a star’s intrinsic brightness, a star’s luminosity is one of the most commonly confused classifying traits. Most people confuse luminosity with apparent magnitude, which is how bright it appears from Earth. But scientists use the term luminosity to describe intrinsic brightness–how bright it is on the inside.
A star’s luminosity is measured by:
- surface temperature
Keeping this in mind, do you know the answer to this question? If a scientist is comparing two stars and both have the same surface temperature, which has greater luminosity? The answer– whichever has the greatest surface temperature.
It’s also important to remember that a star’s light spectrum and brightness can be used to identify compositional elements, movements, and distance from Earth. For example, the stars that are the brightest (greatest luminosity) are the closest to Earth in distance.
The Water Cycle
The most renewable of all resources, water is continually regenerated through the stages of the water cycle. Water always exists in these three places: the ocean, the land, and the atmosphere. It also takes on many forms. These include lakes, rivers, and even sheets of ice.
This is how it works:
- The Sun heats up water inside the ocean, lakes, rivers, etc. Through this process called evaporation, steam is formed. This steam is also called water vapor, and it rises into the air. Plant transpiration helps this process.
- Next, the gaseous form of water (vapor) changes back into a liquid in the sky. This process, condensation, is how clouds are formed.
- As more and more water is formed inside of the clouds, precipitation begins. The water drifts back down, filling the lakes and oceans once again.
This cycle continues to repeat. We must note that there is a relationship between the most common water reservoirs (things on the surface of Earth) and those below. Like streams, flooded plains, and swamps, subsurface reservoirs also play a hand in the water cycle. These include areas that were too saturated with liquid, allowing water to sink deep down within to be stored.
And that’s some basic info about Subtest I: General Science.