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Name: Ramon
Status: other
Grade: other
Location: NV
Country: N/A
Date: N/A

How do astronomers determine the composition and layers of the planets, especially the outer four planets?

Since the outer planets are gaseous giants, they can determine the structure through spectroscopic observations. For example, Jupiter's outer layers come out best in methane light.

Hope this helps!

David H. Levy


In order for us to determine anything we have to have data. This means that something from the outer four planets must reach us. Before the days when we could send probes to the other planets, there was one thing that certainly reached us from these planets: light (we could certainly "see" the planets so light that has bounced off from these planets have reached us).

Light has a distinctive way of reacting with matter. Just think of how certain substances are differently colored from others. This means that all forms of matter have a distinct "fingerprint" of light reflection or emission. So, imagine we focus our telescopes onto a planet, collect the light that bounced off that planet, then we can analyze the light and look for distinctive patterns of particular elements or substances. ...this is not easy, because all the elements and substances will be reflecting back light at the same time and the data is a mash-up of all these patterns. However, with good detective work and analysis, we have been able to determine the composition the gas planets and the atmospheres above the inner planets.

Greg (Roberto Gregorius)
Canisius College

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