Is it a Planet?

Pluto is no longer considered a planet. Since I was in school and learned that Pluto was the ninth and smallest planet, other discoveries about the outer limits of our solar system have been made. First, Pluto lies in the Kuiper Belt, a giant ring of methane, ammonia and water ice chunks. Astronomers also found an object beyond Neptune larger than Pluto, Eris.

However, Eris is not the reason Pluto is not a planet. To be a planet an object has to 1. be spherical, 2. orbit the sun and 3. have enough mass to govern all objects in its orbit with its gravity. Earth is a planet because it meets all requirements. It is spherical, orbits the sun and controls the moon with its overwhelming gravity. Pluto, however, does not. Its mass is not enough to pull at all the many objects in the Kuiper Belt. These objects remain in their own orbits and are not disrupted by Pluto's movement and gravity.

Earth's Size

The diameter of the Earth is 12,756.2 km. The Sun, however, has a diameter 109 times bigger! It is 1,391,000 km. This means that about 1 million Earths can fit inside the sun!

So the Sun is much bigger than the planets, but the Earth, while bigger than Venus, Mercury and Mars, is significantly smaller than the outer planets. 1321.3 Earths can fit inside giant Jupiter!

Astronomy Trip to AMNH 10/26/09

My class visited the American Museum of Natural History on Monday, October 26th. We first went to the Hall of Meteorites where the museum has three pieces of an actual meteorite that fell in Greenland. I learned that the biggest piece, named Ahnighto is so massive that it sits on iron posts that go down all the way to the bedrock deep beneath the museum. I also learned that when meteorites hit the Earth they tell us about the start of the solar system because they have gone unchanged for the past 4.6 billion years. Those not big enough to get through the Earth's atmosphere burn up and we see them as "shooting stars."

Next we went to the Rose Center. We saw the Big Bang movie where I learned that the universe was much hotter, smaller and denser than it is today. It actually is expanding right now. Afterward, we went to see Journey to the Stars, a movie about the sun and the history of stars. I already knew that stars have great mass and gravity, they have great pressure, heat and density inside so fusion between Hydrogen atoms occurs which produces Helium, heat and light.
All stars do this. What I learned was that the sun is an average star: average size, average temperature, average life span. Hopefully, when the sun dies it will not explode in a supernova; only 1% of stars do this.

I still have some questions. Why can supernovas produce the heavy elements when they are expanding? Don't they have to have greater pressure than stars? And why didn't the sun pull in all the matter in the solar system when it first formed? Why was there enough matter left to make all the planets?

The atmosphere is made up of a series of layers of gas. Each layer has different characteristics (temperature, pressure, density, element composition). The air we breathe and the weather we observe is in the Troposphere.

Early Impact!

_______Fifty million years after the Earth first coalesced into a planet it was hit by another, smaller planet. Because the second planet did not hit Earth directly, the planet survived the impact and actually gained in mass. The remaining matter formed the Moon.