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.

Yet It Moves

Today is "Presidents Day" in the US, a holiday for NASA employees. Abraham Lincoln was born February 12 and George Washington February 22. More important for science, February 16 is Galileo Galilei's birthday! 2009 is International Year of Astronomy because 400 years ago Galileo first demonstrated his telescope. This replica is on display at the Griffith Observatory. The telescope offered clues that Earth was not centre of the Universe.

Just as they claim today about the speed of light, scientists of Galileo's time insisted that Earth was fixed. To explain retrograde motion they invoked epicycles, wheels within wheels. (Read: "dark energy") The mathematics of epicycles were highly complicated, which kept most people from understanding astronomy and insured scientists their place in society. If someone claimed that Earth circled the Sun, they could claim that this conflicted with epicycle math.

Galileo did not start his career believing that Earth circles the Sun. When a foreign scholar visited Italy to talk on Copernican Theory, Galileo missed the lectures. Only later did Galileo realise that Copernicus might be on to something. He realised that while believers in Ptolemy had converted to Copernicus, not a single believer in the Copernican system had converted back to Ptolemy. Logically Galileo chose to join the converted.

Galileo's telescope showed phases of Venus, Rings of Saturn, and moons circling Jupiter. These were all indicators that Earth was not centre of everything. Some chose to completely ignore the evidence before their eyes, claiming it was some trick of the telescope. The discovery of double stars was seen as a fault in the telescope!

Galileo gained many detractors. Since Newton's Laws of gravitation had not yet been formulated, detractors would claim that Galileo lacked any mechanism for holding the planets in orbit. Galileo's detractors could also claim the Moon as evidence--if the Moon revolves around us, so should everything else. The learned can be the most resistant to change. Today we know who was right, and 445 years after his birth Galileo is an example for today's scientist.

Galileo Stands Vigil

This photo was taken April 24--everything in the background is now blackened by fire. Fortunately Griffith Observatory is protected by this totem of great astronomers. Galileo stands in the place of honour facing the planetarium dome. On the lawn and courtyard the planetary orbits are depicted to scale, orbiting the Sun as Galileo believed following the ellipses of his friend Kepler.

From childhood Galileo was curious about many things. His professors at Pisa could not deal with his inquisitive mind. Even today a student who wishes to learn something new is considered a threat. Galileo was forced to leave university before graduating for financial reasons. It is fortunate that he found a career teaching, for today someone without a degree would not even be allowed to teach school. (MIT's Dean of Admissions doesn't count.)

Galileo did not start his career believing that Earth circles the Sun. When a foreign scientist visited Italy to lecture on Copernican Theory, Galileo avoided the lectures. Only by talking with colleagues did Galileo realise that Copernicus might be on to something. He then realised that believers in Ptolemy had converted to Copernicus, not a single believer in the Copernican system had converted back to Ptolemy. Logically Galileo chose to join the converted.

Even as a student, Galileo gained detractors. Later some would write whole books attacking his theories. Others would claim credit for Galileo's discoveries. Today they would have the internet to spread nasty rumours. Though Galileo considered Pope Urban a friend, people whispered rumours in the Pope's ear that Galileo's book was satirised him. For these and other reasons, Galileo would be tried and sentenced to house arrest.

The 10 years of house arrest could have been worse. His friend the archibishop of Siena offered to keep Galileo as a guest. After a stay in the palace at Siena, Galileo was allowed to return to his own villa. His home had a tower suitable for observing the stars. Griffith Observatory contains a copy of Galileo's telescope. True discoveries outlast troubled times.

Galileo's Moons

Io and Europa in the same frame March 2, 2007, two days after New Horizon's flyby of Jupiter. As the spacecraft sped away it took this long-lens photo. The moons are in fact separated by 790,000 kilometres. Eruption of the volcano Tvashtar is still very visible. Io's night side is lit by Jupiter, a planet which gives off twice as much radiation as it receives from the Sun. Europa's night side is dark because it is on the other side of Jupiter.

The night of January 7, 1610 Galileo first noticed strange objects around Jupiter. By January 13 he had seen 4 moons. Discovery of new worlds was truly exciting and kept Galileo up every night. By March 22 he had finished his observations, and immediately started writing his observations in book form.

STARRY MESSENGER was published that same year and was immediately popular. The book was also controversial, because not everyone believed in the new moons. Someone named Horky, who had been a student of Johannes Kepler, wrote a book claiming that the moons were a fraud designed to gain fame and wealth. Kepler was very unhappy, but he counseled Galileo not to respond to such attacks.

Pictured to scale by New Horizons are Io, Europa, Ganymede and Callisto. The moons will be there long after the doubters are underground. Kepler's advice to Galileo was right on.

New Horizons at Jupiter

On its way to reach Pluto in 2015, the New Horizons spacecraft swung by Jupiter for some gravitational assist. As practice, it took the best picture yet of the Great Red Spot and the new Spot. Little Spot was formed from the merger of 3 smaller spots, and continues to grow. As in a tub of water, smaller vortices eventually merge into one big one.

The Great Red Spot was first observed by Domenico Cassini around 1665. It is shaped like an Earthly cyclone, but has lasted far longer. These storms form coloured spots because they extend deep into the atmosphere. They are signs of some unknown phenomena inside Jupiter. We recently saw that brown dwarfs, which occupy a size range between Jupiter and stars, are home to massive sources of energy. There is more inside Jupiter than meets the eye.

Below in 3-D is the eruption of volcano Tvashtar on Io. This moon itself emits a lot of heat. New Horizons also discovered a new volcano just reaching the surface of Io. Near Hawaii we have a submerged volcano named Lo' ihi that will someday form a new island. Objects from gas giants to little moons like Enceladus contain sources of energy. Something is going on literally beneath our feet.

Io is one of the four satellites discovered by Galileo. Objects circling a body other than Earth were a direct threat to the old Ptolemaic system. Scholars of the day refused to peer into Galileo's telescope for fear of upsetting their world view. Galileo spent the last 10 years of his life under house arrest for promoting heresy. (A bit like saying the speed of light isn't constant.) Despite his persecution, a Jupiter probe and a STAR TREK shuttle would be named for Galileo.

Jupiter and Galileo's Moons

This amazing photo of Jupiter was taken from Saturn! On February 8, 2007 Jupiter was 1.8 billion kilometres from our Cassini spacecraft. Two of the Galilean satellites are visible. When Galileo turned his telescope to the skies, he was amazed to discover Io, Europa, Ganymede and Callisto circling Jupiter. This provided evidence of objects circling something other than Earth, in defiance of Ptolemy's cosmology. Scientists of the time literally refused to peer in the telescope for fear of upsetting their world view.

“Here at Padua,” Galileo complained in a letter to Kepler, "is the principal professor of philosophy whom I have repeatedly and urgently requested to look at the moon and planets through my glass, which he pertinaciously refuses to do. Why are you not here? Whart shouts of laughter we should have at this glorious folly! And to hear the professor of philosophy at Pisa labouring before the Grand Duke with logical arguments, as if with magical incantations, to charm the new planets out of the sky.”

(Thanks Nigel, for reminding me of this quote, which I used part of in January 11 post.)

If that professor were alive today his magical incantations would no doubt include "dark energy" or whatever is fashionable and safe. He would try to prevent Galileo from speaking, publishing, or even having his observations considered. Unlike this writer, Galileo did not complete a university degree. That fact would be cited against him by today's elitists.

Despite his gap in formal education, Galileo was a fair scientist. He was willing to adjust his theories in accordance with new observations. His book "Dialogue on the Two Chief World Systems" gave equal time to opposing ideas. Some sinister folks spread rumour that the "Simplicio" character was a vague parody of the Pope. (Did they use e-mail?) Galileo was tried, forced to recant, and imprisoned for the last ten years of his life.

Below is a closer Cassini image of Jupiter, taken January 15, 2001 as the spacecraft completed its close flyby. Galilean moon Io is visible as a tiny crescent to the left. Four centuries later moons orbit planets and planets orbit the Sun just as Galileo believed. All follow elliptical orbits as Galileo's friend Kepler discovered. All follow paths controlled by Newton's gravity. The treatment given to Galileo is very relevant today.