23 Июл. 2016 г.|
Astronomy in the 17th centuryThe impact of thetelescopenew observatories France, China andother places. Named after Roman father of the gods who was the god of fun, it also represented tin, green, triangle, 8, and Thursday (French=Jeudi). Jupiter is really a small star, almost, but not quite, large enough for gravitational pressure to heat the core sufficiently for nuclear fusion to occur. With only a small telescope it is possible to see the bands of clouds across Jupiter and the largest almost permanent storm system, The Great Red Spot, as well as the four largest moons. Jupiter's four largest moons were first observed by Galileo using the telescope he had made with the assistance of his toolmaker Marc'antonio Mazzoleni, and a glass maker to make the lenses.
When Galileo observed the four largest moons of Jupiter through his telescope, in 1610, and saw how quickly they orbited round Jupiter he thought the timing of their eclipses could be used to determine longitude. The moons of Jupiter can only be seen through a telescope, and trying to hold and focus a telescope on Jupiter, on a boat bobbing about on the sea was of course, impossible. To aid their observations they planned in 1671 to get observations of Io's eclipse from the site of Tycho Brahe's observatory on the island of Hveen off the coat of Denmark, which could be compared with simultaneous observations made of the same event from Paris. Picard was assisted in Denmark by the professor of mathematics at Copenhagen University, Erasmus Bartholin (1625-1698) and his student and son-in-law, Olaf (Ole) Roemer (1644-1710). A brilliant scientist and inventor, one of his most famous - and at the time controversial discoveries - was the speed of light, from his observations of the orbits of Jupiter's moons. The Unrevealed Wonders of the Heavens by Andrew Barclay, FRAS, Engineer, Argyll House, Kilmarnock. It was in the English Mechanic of 20th October, 1893, that Andrew Barclay sent in his results from his 9in. Barclay tried to get his paper read in November 1892 at the British Astronomical Association, only to be told by the assistant secretary that "the telescopes must be distorting the image, as no such things existed as shown on my drawings. Not everyone was rude about Barclay's observations, some letters were much kinder, he had his supporters who pointed out that Copernicus and Galileo had their critics in their day. Until it was possible to send out a probe, even photographs could do little better than the drawings.
By the 1950s an amateur astronomer was receiving radio signals from Jupiter in his converted Martello Tower. More information came in the 1970s with the launch of Pioneer 10 and 11, in 1972 and 1973, and Voyager 1 and Voyager 2 in 1977.
The Voyager probes transmitted back to Earth much clearer images of the bands of whirling clouds on Jupiter's surface. The crash in July 1994, of fragments of comet Shoemaker-Levy-9 into Jupiter, left enormous holes the size of the Earth, as each fragment impacted raising great clouds of material. Further information on Jupiter and its moons came from Galileo, launched in 1989, which arrived at Jupiter in 1995.
Galileo was the first spacecraft to fly past an asteroid and the first to discover a moon of an asteroid. Galileo was the first to measure Jupiter's atmosphere with a descent probe and the first to conduct long-term observations of the Jovian system from orbit. An eruption of the largest volcano, Pele (named after the Hawaiian goddess of volcanos) was discovered by engineer Linda Morabito. The names of surface features on Io are taken from gods and heroes in the world's myths associated with fire, thunder, volcanoes, the sun and the story in Greek mythology in which Jupiter disguised himself as a cloud to get his leg over Io. In December 2013, jets of water vapour were thought to have been seen on Europa, but these have not been observed since. The names of features on Europa are taken from European gods and heroes, ancient Egypt and the story in Greek mythology in which Jupiter disguised himself as a bull to get his leg over Europa. This was a new and significant discovery and he rushed to publish this in a book called "Siderius Nuncius" (The Starry Messenger) in March. The Italian astronomer, Giovanni Domenico Cassini (1625-1712) complied and published tables for Jupiter's satellites.
Roemer was invited by Picard to work in Paris, where he also had to teach the Dauphin maths.
He noticed the time difference in the observations of the eclipses, at different times of the year when the Earth and Jupiter were at different positions in their obits and from this was able to deduce the speed of light.
In the 19th century, the British Astronomical Association was founded for amateur astronomers, and the Royal Astronomical Society admitted both amateur and professional. They admired his persistence too, in also showing his results for Mars, Venus and Saturn which also invited ridicule. In the November 23rd issue of the English Mechanic another letter was accompanied by his drawing of his improved observations.
This is a popular project in radio astronomy and a field in which the amateur at home can still be of use.
The Pioneer probes discovered that much of the heat that powers Jupiter's weather system comes from inside the planet.
They discovered that Jupiter had a thin ring of particles surrounding it to a distance of about 57,000 kilometres above the cloud tops. It was hoped that more information about the interior of Jupiter would be gleaned from the observations made of an event that was far more catastrophic than anticipated. The data Galileo sent has given information on Jupiter's atmosphere which was very different to what was expected. It found evidence of subsurface salt water on Europa, Ganymede and Callisto and revealed the intensity of volcanic activity on Io. Its surface is covered by red and yellow sulphur from the huge active volcanoes - the most actively volcanic of the planets.
The pictures sent back by Galileo, looked as if Europa's surface was covered by roads or canals.
Further observations will be made using Hubble, from the end of 2014 to early 2015 to confirm if these jets exist.
In Greek mythology Callisto was changed into the Great Bear constellation by Jupiter's long suffering wife Juno (in Greek Hera) to escape Jupiter's adulterous intentions. Chinese called it the Year Star - as their calendar cycle (which originated in India) was based on a Jupiter year of approximately 12 years , also represented the element wood, the direction of east.
With regard to publicity and funding, Galileo dedicated his work to the ruler of Tuscany Cosimo Medici, and suggested he named the newly discovered moons of Jupiter after him and his family.
At the time the dividing line was blurred - a wealthy amateur could have a professional observatory. Also for the first time Jupiter's satellites could be seen in detail, and more satellites were discovered.
They are running out of using the names of the god Jupiter's (Zeus) lovers - many as they were and will now also use names of his daughters etc.
Results, and queries, letters and feedback were catered for by society journals and more general magazines like the English Mechanic. Watching Earth sized holes punched into Jupiter raised a new awareness of the chances of something hitting Earth and what the consequences would be.
The tugging between the two satellites as they pass each other always in the same place in their orbits causes their orbits to become eccentric. It is so cold at this distance from the Sun, the ice can freeze further into harder states in which it behaves like rock. Later astronomers to whom the once powerful Medici dynasty meant nothing preferred to call them the Galilean moons. It found no clouds of water, not much lightning and and the atmosphere is predominantly hydrogen. The Galileo fly-past in June 1996 showed features on Europa that resembled the ice in the Arctic ocean on Earth. Some areas on Ganymede have many craters, while other parts have very few craters indicating that the surface here is newer and that the planet could be still geologically active. Rotates round its axis in under 12 hours and orbits Jupiter in same period so same side always faces Jupiter.
Water has been found in some parts of Jupiter, so some form of life might even be possible. The Galileo fly-by in June 1996 showed ancient cratered ice fields and younger volcanic plains, ridged ice mountains, deep furrows and smooth basins, the products of tectonic forces.
Density slightly less than water which indicates that it is formed of icy rubble - rocks and ice. The movement of the icy plates indicates that the ice is not solid down to the rocky interior of the planet but there may be a layer or slush or liquid water below the surface. This discovery was a surprise seeing how close it is to Jupiter - and the state of fiery Io - further out. The spacecraft was deliberately destroyed to protect one of its own discoveries - a possible ocean beneath the icy crust of the moon Europa.