NEPTUNE IS DISCOVERED AT THE BERLIN OBSERVATORY

Today, The Grandma has received the wonderful visit of Joseph de Ca'th Lon, one of her best friends. 

 

Joseph loves Astronomy and they have been talking about Neptune, the planet that was discovered on a day like today in 1846.

Neptune is the eighth planet from the Sun and the farthest known solar planet. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times the mass of Earth, and slightly more massive than its near-twin Uranus. 

Neptune is denser and physically smaller than Uranus because its greater mass causes more gravitational compression of its atmosphere. It is referred to as one of the solar system's two ice giant planets, the other one being Uranus.

Being composed primarily of gases and liquids, it has no well-defined solid surface. The planet orbits the Sun once every 164.8 years at an average distance of 30.1 AU (4.5 billion km; 2.8 billion mi). It is named after the Roman god of the sea and has the astronomical symbol ♆, representing Neptune's trident.

Neptune is not visible to the unaided eye and is the only planet in the Solar System found by mathematical prediction rather than by empirical observation. Unexpected changes in the orbit of Uranus led Alexis Bouvard to hypothesise that its orbit was subject to gravitational perturbation by an unknown planet. After Bouvard's death, the position of Neptune was predicted from his observations, independently, by John Couch Adams and Urbain Le Verrier.

More information: NASA

Neptune was subsequently observed with a telescope on 23 September 1846 by Johann Galle within a degree of the position predicted by Le Verrier. Its largest moon, Triton, was discovered shortly thereafter, though none of the planet's remaining 13 known moons were located telescopically until the 20th century.

The planet's distance from Earth gives it a very small apparent size, making it challenging to study with Earth-based telescopes.  

Neptune was visited by Voyager 2, when it flew by the planet on 25 August 1989; Voyager 2 remains the only spacecraft to have visited Neptune. The advent of the Hubble Space Telescope and large ground-based telescopes with adaptive optics has recently allowed for additional detailed observations from afar.

Like Jupiter and Saturn, Neptune's atmosphere is composed primarily of hydrogen and helium, along with traces of hydrocarbons and possibly nitrogen, though it contains a higher proportion of ices such as water, ammonia and methane. However, similar to Uranus, its interior is primarily composed of ices and rock; Uranus and Neptune are normally considered ice giants to emphasise this distinction.

Along with Rayleigh scattering, traces of methane in the outermost regions in part account for the planet's blue appearance. Newest data from the Gemini observatory shows the blue color is more saturated than the one present on Uranus due to thinner haze of Neptune's more active atmosphere.

In contrast to the hazy, relatively featureless atmosphere of Uranus, Neptune's atmosphere has active and visible weather patterns. For example, at the time of the Voyager 2 flyby in 1989, the planet's southern hemisphere had a Great Dark Spot comparable to the Great Red Spot on Jupiter. More recently, in 2018, a newer main dark spot and smaller dark spot were identified and studied.

In addition, these weather patterns are driven by the strongest sustained winds of any planet in the Solar System, with recorded wind speeds as high as 2,100 km/h. Because of its great distance from the Sun, Neptune's outer atmosphere is one of the coldest places in the Solar System, with temperatures at its cloud tops approaching −218 °C. Temperatures at the planet's centre are approximately 5,100 °C.

Neptune has a faint and fragmented ring system (labelled "arcs"), which was discovered in 1984, then later confirmed by Voyager 2.

More information: NASA

 What I want to look at with Webb is
what we call ice giants in our solar system
-the planets Neptune and Uranus.

Heidi Hammel

AMALTHEA, A NEW MOON OF JUPITER IS DISCOVERED

Today, The Grandma has received the wonderful visit of one of her closest friends, Joseph de Ca'th Lon.

Joseph loves astronomy, and they have been talking about Amalthea, the third closest and fifth found moon of Jupiter, that was discovered by Edward Emerson Barnard on a day like today in 1892.

Amalthea is a moon of Jupiter. It has the third-closest orbit around Jupiter among known moons and was the fifth moon of Jupiter to be discovered, so it is also known as Jupiter V.

It is also the fifth-largest moon of Jupiter, after the four Galilean Moons. 

Edward Emerson Barnard discovered the moon on 9 September 1892 and named it after Amalthea of Greek mythology. It was the last natural satellite to be discovered by direct visual observation; all later moons were discovered by photographic or digital imaging.

Amalthea is in a close orbit around Jupiter and is within the outer edge of the Amalthea Gossamer Ring, which is formed from dust ejected from its surface.

Jupiter would appear 46.5 degrees in diameter from its surface. Amalthea is the largest of the inner satellites of Jupiter and is irregularly shaped and reddish. It is thought to consist of porous water ice with unknown amounts of other materials. Its surface features include large craters and ridges.

Close range images of Amalthea were taken in 1979 by the Voyager 1 and Voyager 2 spacecraft, and in more detail by the Galileo orbiter in the 1990s.

More information: NASA

Amalthea was discovered on 9 September 1892 by Edward Emerson Barnard using the 91 cm refractor telescope at Lick Observatory.

It was the last planetary satellite to be discovered by direct visual observation, as opposed to photographically, and was the first new satellite of Jupiter since Galileo Galilei's discovery of the Galilean satellites in 1610.

Amalthea is named after the nymph Amalthea from Greek mythology, who nursed the infant Zeus, the Greek equivalent of Jupiter, with goat's milk. Its Roman numeral designation is Jupiter V.

The name Amalthea was not formally adopted by the IAU until 1976, although it had been in informal use for many decades. The name was initially suggested by Camille Flammarion. Before 1976, Amalthea was most commonly known simply as Jupiter V.

The surface of Amalthea is very red. This colour may be due to sulphur originating from Io or some other non-ice material. Bright patches of less red tint appear on the major slopes of Amalthea, but the nature of this colour is currently unknown.

The surface of Amalthea is slightly brighter than surfaces of other inner satellites of Jupiter. There is also a substantial asymmetry between leading and trailing hemispheres: the leading hemisphere is 1.3 times brighter than the trailing one.

More information: NASA

The asymmetry is probably caused by the higher velocity and frequency of impacts on the leading hemisphere, which excavate a bright material -presumably ice- from the interior of the moon.

There are four named geological features on Amalthea: two craters and two faculae (bright spots). The faculae are located on the edge of a ridge on the anti-Jupiter side of Amalthea.

Craters are named after characters in Greek mythology associated with Zeus and Amalthea, faculae after locations in associated with Zeus.

During 1979, the unmanned Voyager 1 and Voyager 2 space probes obtained the first images of Amalthea to resolve its surface features, they also measured the visible and infrared spectra and surface temperature.

Later, the Galileo orbiter completed the imaging of Amalthea's surface. Galileo made its final satellite fly-by at a distance of approximately 244 km from Amalthea's centre at a height of about 160–170 km on 5 November 2002, permitting the moon's mass to be accurately determined, while changing Galileo's trajectory so that it would plunge into Jupiter in September 2003 at the end of its mission.

In 2006, Amalthea's orbit was refined with measurements from New Horizons.

More information: Solar Views

 Jupiter is so big and its gravitational pull so strong
that man would find it difficult to move about on the surface.
The answer is to whittle it down to proper size
with terrajets and nuclear power,
using the debris to increase the size of Jupiter's moons so they,
too, can be colonized.

Fritz Zwicky

'VOYAGER 2' IN CAN ROIG OBSERVATORY, LLAGOSTERA

Voyager 2, 1977 / Visiting Can Roig Observatory

Today, The Grandma has visited Can Roig Astronomical Observatory in Llagostera, Girona.

She has shared this visit with Joseph de Ca'th Lon, his closer friend, who is a fan of Astronomy and who has explained her lots of things about Voyager 2, the space probe launched by NASA on a day ike today in 1977.

During the travel from Barcelona to Llagostera, in the county og Gironès, in Girona, The Grandma has studied a new lesson of her Ms. Excel course.

Chapter 14. Schemes and views (II) (Spanish Version)

Voyager 2 is a space probe launched by NASA on August 20, 1977, to study the outer planets. Part of the Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach Jupiter and Saturn but enabled further encounters with Uranus and Neptune. It is the only spacecraft to have visited either of these two ice giant planets.

Its primary mission ended with the exploration of the Neptunian system on October 2, 1989, after having visited the Uranian system in 1986, the Saturnian system in 1981, and the Jovian system in 1979.

Voyager 2 is now in its extended mission to study the outer reaches of the Solar System and has been operating for 42 years and 3 days as of 23 August 2019. It remains in contact through the NASA Deep Space Network.

More information: Jet Propulsion Laboratory-NASA

At a distance of 120 AU from the Sun as of February 25, 2019, moving at a velocity of 15.341 km/s relative to the Sun, Voyager 2 is the fourth of five spacecraft to achieve the escape velocity that will allow them to leave the Solar System.

The probe left the heliosphere for interstellar space on November 5, 2018, becoming the second artificial object to do so, and has begun to provide the first direct measurements of the density and temperature of the interstellar plasma.

Voyager 2: Interstellar

In the early space age, it was realized that a periodic alignment of the outer planets would occur in the late 1970s and enable a single probe to visit Jupiter, Saturn, Uranus, and Neptune by taking advantage of the then-new technique of gravity assists.

NASA began work on a Grand Tour, which evolved into a massive project involving two groups of two probes each, with one group visiting Jupiter, Saturn, and Pluto and the other Jupiter, Uranus, and Neptune. The spacecraft would be designed with redundant systems to ensure survival through the entire tour.

By 1972 the mission was scaled back and replaced with two Mariner-derived spacecraft, the Mariner Jupiter-Saturn probes. To keep apparent lifetime program costs low, the mission would include only flybys of Jupiter and Saturn, but keep the Grand Tour option open. As the program progressed, the name was changed to Voyager.

The primary mission of Voyager 1 was to explore Jupiter, Saturn, and Saturn's moon, Titan. Voyager 2 was also to explore Jupiter and Saturn, but on a trajectory that would have the option of continuing on to Uranus and Neptune, or being redirected to Titan as a backup for Voyager 1. Upon successful completion of Voyager 1's objectives, Voyager 2 would get a mission extension to send the probe on towards Uranus and Neptune.

More information: Science News

Constructed by the Jet Propulsion Laboratory (JPL), Voyager 2 included 16 hydrazine thrusters, three-axis stabilization, gyroscopes and celestial referencing instruments (Sun sensor/Canopus Star Tracker) to maintain pointing of the high-gain antenna toward Earth. Collectively these instruments are part of the Attitude and Articulation Control Subsystem (AACS) along with redundant units of most instruments and 8 backup thrusters. The spacecraft also included 11 scientific instruments to study celestial objects as it traveled through space.

Built with the intent for eventual interstellar travel, Voyager 2 included a large, 3.7 m parabolic, high-gain antenna to transceive data via the Deep Space Network on the Earth. Communications are conducted over the S-band, about 13 cm wavelength, and X-band, about 3.6 cm wavelength, providing data rates as high as 115.2 kilobits per second at the distance of Jupiter, and then ever-decreasing as the distance increased, because of the inverse-square law. When the spacecraft is unable to communicate with Earth, the Digital Tape Recorder (DTR) can record about 64 kilobytes of data for transmission at another time.

Voyager 1 & Voyager 2

Voyager 2 is equipped with 3 MHW RTG. Each RTG includes 24 pressed plutonium oxide spheres, and provided enough heat to generate approximately 157 W of electrical power at launch. Collectively, the RTGs supplied the spacecraft with 470 watts at launch, halving every 87.7 years, and will allow operations to continue until at least 2020.

The Voyager 2 probe was launched on August 20, 1977, by NASA from Space Launch Complex 41 at Cape Canaveral, Florida, aboard a Titan IIIE/Centaur launch vehicle. Two weeks later, the twin Voyager 1 probe was launched on September 5, 1977. However, Voyager 1 reached both Jupiter and Saturn sooner, as Voyager 2 had been launched into a longer, more circular trajectory.

Following a mid-course correction in 1987, Voyager 2's closest approach to Neptune occurred on August 25, 1989. Through repeated computerized test simulations of trajectories through the Neptunian system conducted in advance, flight controllers determined the best way to route Voyager 2 through the Neptune-Triton system.

More information: CSIRO

Since the plane of the orbit of Triton is tilted significantly with respect to the plane of the ecliptic, through mid-course corrections, Voyager 2 was directed into a path about 4950 kilometers above the north pole of Neptune. Five hours after Voyager 2 made its closest approach to Neptune, it performed a close fly-by of Triton, the larger of Neptune's two originally known moons, passing within about 40,000 kilometers.

Voyager 2 discovered previously unknown Neptunian rings, and confirmed six new moons: Despina, Galatea, Larissa, Proteus, Naiad and Thalassa. While in the neighborhood of Neptune, Voyager 2 discovered the Great Dark Spot, which has since disappeared, according to observations by the Hubble Space Telescope.

The Great Dark Spot was later hypothesized to be a region of clear gas, forming a window in the planet's high-altitude methane cloud deck.

With the decision of the International Astronomical Union to reclassify Pluto as a dwarf planet in 2006, the flyby of Neptune by Voyager 2 in 1989 became the point when every known planet in the Solar System had been visited at least once by a space probe.

More information: Los Angeles Times

According to 'M' theory, ours is not the only universe.

Instead, 'M' theory predicts that a great many universes

were created out of nothing.

Stephen Hawking