On this day in 1989 the Galileo spacecraft was launched to explore Jupiter and its moons.
Galileo was an American unmanned spacecraft that studied the planet Jupiter and its moons, as well as several other Solar System bodies. Named after the Italian astronomer Galileo Galilei, it consisted of an orbiter and an entry probe. It was delivered into Earth orbit on October 18, 1989 by Space Shuttle Atlantis. Galileo arrived at Jupiter on December 7, 1995, after gravitational assist flybys of Venus and Earth, and became the first spacecraft to orbit Jupiter. It launched the first probe into Jupiter, directly measuring its atmosphere. Despite suffering major antenna problems, Galileo achieved the first asteroid flyby, of 951 Gaspra, and discovered the first asteroid moon, Dactyl, around 243 Ida. In 1994, Galileo observed Comet Shoemaker–Levy 9’s collision with Jupiter.
Jupiter’s atmospheric composition and ammonia clouds were recorded, the clouds possibly created by outflows from the lower depths of the atmosphere. Io’s volcanism and plasma interactions with Jupiter’s atmosphere were also recorded. The data Galileo collected supported the theory of a liquid ocean under the icy surface of Europa, and there were indications of similar liquid-saltwater layers under the surfaces of Ganymede and Callisto. Ganymede was shown to possess a magnetic field and the spacecraft found new evidence for exospheres around Europa, Ganymede, and Callisto. Galileo also discovered that Jupiter’s faint ring system consists of dust from impacts on the four small inner moons. The extent and structure of Jupiter’s magnetosphere was also mapped.
On September 21, 2003, after 14 years in space and 8 years in the Jovian system, Galileo’s mission was terminated by sending it into Jupiter’s atmosphere at a speed of over 48 kilometers per second (30 mi/s), eliminating the possibility of contaminating local moons with terrestrial bacteria. (source)
Christiaan Huygens (14 April 1629 – 8 July 1695) was a Dutch physicist, mathematician, astronomer and inventor, who is widely regarded as one of the greatest scientists of all time and a major figure in the scientific revolution. In physics, Huygens made groundbreaking contributions in optics and mechanics, while as an astronomer he is chiefly known for his studies of the rings of Saturn and the discovery of its moon Titan. As an inventor, he improved the design of the telescope with the invention of the Huygenian eyepiece. His most famous invention, however, was the invention of the pendulum clock in 1656, which was a breakthrough in timekeeping and became the most accurate timekeeper for almost 300 years. Because he was the first to use mathematical formulae to describe the laws of physics, Huygens has been called the first theoretical physicist and the founder of mathematical physics.
In 1659, Huygens was the first to derive the now standard formula for the centripetal force in his work De vi centrifuga. The formula played a central role in classical mechanics and became known as the second of Newton’s laws of motion. Huygens was also the first to formulate the correct laws of elastic collision in his work De motu corporum ex percussione, but his findings were not published until after his death in 1703. In the field of optics, he is best known for his wave theory of light, which he proposed in 1678 and described in 1690 in his Treatise on Light, which is regarded as the first mathematical theory of light. His theory was initially rejected in favor of Isaac Newton’s corpuscular theory of light, until Augustin-Jean Fresnel adopted Huygens’ principle in 1818 and showed that it could explain the rectilinear propagation and diffraction effects of light. Today this principle is known as the Huygens–Fresnel principle. read more
Vertical structures, among the tallest seen in Saturn’s main rings, rise abruptly from the edge of Saturn’s B ring to cast long shadows on the ring in this image taken by NASA’s Cassini spacecraft two weeks before the planet’s August 2009 equinox.
If the earth had rings, would we see them when it was night? It's a stupid question but still
Yes, just as the moon reflects the light of the Sun, the rings also reflect. But perhaps they would not be like the rings of Saturn, they would be smaller because the Earth has the gravity smaller than the one of Saturn to hold them and also they would not be made of ice, because they would be closer to the Sun. There is a specific point in the System Solar known as “ice line” or “snow line”. This is the point in the Solar System, where ice deposits could have survived for long periods of time. Any closer and the radiation from the Sun sublimates the ice away. Instead, the rings could be made of rock and dust.
Why does Saturn have a ring and how was the ring made?
It is not only Saturn that has rings, Jupiter, Uranus and Neptune also has rings, although they are more discreet.
The origin of the rings is unknown. The first theory concluded that its formation occurred along with that of the planets about 4 billion years ago, but recent studies indicate that they are younger, only a few hundred million years old. Another theory suggests that a comet disintegrated due to tidal forces as it passed near Saturn. Another possibility is the collision of a comet with a moon of Saturn that, when disintegrating, would have formed the mysterious structure.
Possible variations in chemical composition from one part of Saturn’s ring system to another are visible in this Voyager 2 picture as subtle color variations that can be recorded with special computer-processing techniques.