Western Slope Skies
8:15 am
Fri January 17, 2014

Western Slope Skies 1/17/14

For this episode of Western Slope Skies from the Black Canyon Astronomical Society, we learn about the planet Jupiter, which can be seen shining bright in the night skies of January.

Just after dark on a clear January night, look high in the northeast.   That brilliant white “star” is not a star, but the planet Jupiter.  

Jupiter is very bright for two reasons. First, Jupiter is huge – it’s the largest planet in our solar system, fully 11 times wider than Earth.

Second, Jupiter has a vast churning, atmosphere with bright white and tan cloud tops that efficiently reflect the Sun’s light. Astronomers call Jupiter a gas giant planet, because it shares the sun’s composition of mostly of hydrogen and helium, with just a smattering of other elements and compounds. 

The planet Jupiter, captured by NASA's Cassini spacecraft during a fly-by on December 7th, 2000. The shadow of Jupiter's moon, Europa, is visible on the planet's cloud tops to the lower left.
Credit NASA

Because of Jupiter’s great mass, it has powerful gravity that greatly influences other bodies in the solar system.

Jupiter controls the orbits of many periodic comets and the location of the main asteroid belt. Jupiter’s gravity keeps many potentially dangerous solar system objects in stable orbits far from Earth, including the vast majority of asteroids.  

From time to time, Jupiter will capture a comet from solar orbit, and at least 3 comets have plunged into Jupiter’s clouds during the past 20 years. Also, NASA has used gravity assists from Jupiter to accelerate space probes to the outer planets and into interstellar space.     

Jupiter is very important in the history of science. In 1610 Galileo observed Jupiter with the newly invented telescope and charted 4 objects, now called moons, which orbit the planet. This was powerful evidence against the Earth-centered universe, an idea that had prevailed for thousands of years.    

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