Saturday, August 06, 2011

Juno Launches



(From this blog March 2007)

This photo of Jupiter combines a visual image from Hubble with X-ray data from the Chandra spacecraft. The North and South poles are alive with X-rays. Like Earth's aurora, this display occurs in both poles simultaneously 140,000 km distant! Something in Jupiter's core links the poles. Jupiter has an immense magnetic field, the strongest in the solar system. Presence of a singularity would explain Jupiter’s field, and why Jupiter gives off nearly twice as much heat as it receives from the Sun.

Cassini has seen a huge hurricane at Saturn's South Pole. The largest planet does not have a storm centred at the South Pole because Jupiter’s magnetic poles do not line up with the geographic poles. The magnetic field is angled 9.5 degrees, indicating that Jupiter’s singularity is offset like that of Earth. Jupiter completes its day in less than 10 Earth-hours. A southern jet radiating from Jupiter’s core would be bent further outward by the rapid rotation. Magnetic fields would cause the storm to rotate in an anti-clockwise direction as seen from above. For signs of such a storm, we can look at the latitude of Jupiter’s Great Red Spot.

Astronomers like Geoffrey Marcy and Debra Fisher have found "hot Jupiters" in other solar systems, giant planets orbiting very close to stars. Old ideas of planet formation can not explain these objects. They could not have formed solely from condensing gas, for solar radiation would cause the gas to evaporate. Presently astronomers speculate that they formed farther from their suns, and then drifted closer after formation. All of them? If that is true, why haven't our giant planets drifted into the Sun?

If giant planets formed around singularities, a Black Hole's gravity would prevent them from dissipating. Hot Jupiters could then form extremely close to stars. Rotating Black Holes could also account for the magnetic fields of Uranus and Neptune, and why those fields are far offset from the planets’ rotation axes. Jupiter's X-rays could result from the polar jets of a Black Hole.

Friday August 5 the Juno spacecraft successfully launched from Cape Canaveral atop an Atlas V booster. Juno will arrive in Jupiter orbit during July 2016. Attached to Juno is a plaque depicting Galileo. 500 years ago in 1610 Galileo's telescope was first to spot the moons of Jupiter. Though thinkers like Copernicus had proposed that Earth was not centre of the universe, the Galilean satellites were the first evidence of objects circling something other than Earth. Galileo's discovery challenged the prevailing cosmology.

During Galileo's time scientists also disagreed whether light travelled instantaneously or had a finite speed. Galileo suggested stationing lanterns on distant hilltops to time light's travel, but of course he lacked an accurate clock. The first measurement of the finite speed of light was based upon eclipses of the moons Galileo discovered. In the 17th century Ole Roemer explained an anomaly in timing of occultations with a delay caused by the speed of light. In 1676 Roemer predicted that one moon would appear late, and his prediction proved precisely correct. Decades passed before Ole Roemer's results were generally accepted.

Today we have laser lanterns and the distant hilltop of the Moon. The Lunar Laser Ranging Experiment from Apollo has stationed reflectors on the Moon's surface. The initial purpose was to determine the Moon's distance, but LLRE has other applications. Measurements using the Moon can determine that light's finite speed is slowing down. New data about this coming soon.

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1 Comments:

Blogger Zierot said...

erratum:
"500 years ago in 1610 Galileo's telescope was first to spot the moons of Jupiter."

400 years

5:34 AM  

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