Today, The Grandma has been reading about Himalia, the satellite of Jupiter that was discovered by CharlesDillonPerrine on a day like today in 1904.
Himalia, also known as Jupiter VI, is the largest irregular satellite of Jupiter. With a diameter of at least 140 km, it is the sixth largest Jovian satellite, after the four Galilean moons and Amalthea.
It was discovered by Charles Dillon Perrine at the Lick Observatory on 3 December 1904 and is named after the nymph Himalia, who bore three sons of Zeus, the Greek equivalent of Jupiter. It is one of the largest planetary moons in the Solar System not imaged in detail, and the third largest not imaged in detail within the orbit of Neptune.
Himalia was discovered by Charles Dillon Perrine at the Lick Observatory on 3 December 1904 in photographs taken with the 36-inch Crossley reflecting telescope which he had recently rebuilt.
Himalia is Jupiter's most easily observed small satellite; though Amalthea is brighter, its proximity to the planet's brilliant disk makes it a far more difficult object to view.
Himalia is named after the nymph Himalia, who bore three sons of Zeus, the Greek equivalent of Jupiter. The moon did not receive its present name until 1975; before then, it was simply known as Jupiter VI or Jupiter Satellite VI,although calls for a full name appeared shortly after its and Elara's discovery.
The moon was sometimes called Hestia, after the Greek goddess, from 1955 to 1975.
At a distance of about 11,400,000 km from Jupiter, Himalia takes about 250 Earth days to complete one orbit around Jupiter.
It is the largest member of the Himalia group, which are a group of small moons orbiting Jupiter at a distance from 11,400,000 km to 13,000,000 km, with inclined orbits at an angle of 27.5 degrees to Jupiter's equator. Their orbits are continuously changing due to solar and planetary perturbations.
In November 2000, the Cassini spacecraft, en route to Saturn, made a number of images of Himalia, including photos from a distance of 4.4 million km. Himalia covers only a few pixels, but seems to be an elongated object with axes 150±20 and 120±20 km, close to the Earth-based estimations.
In February and March 2007, the New Horizons spacecraft en route to Pluto made a series of images of Himalia, culminating in photos from a distance of 8 million km. Again, Himalia appears only a few pixels across.
When we first sent missions to Jupiter, no one expected to find moons that would have active volcanoes. And I could go down a long list of how often I've been surprised by the richness of nature.
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 Pioneer 11,the robotic space probe launched by NASA on a day like today in 1973.
Pioneer 11, also known as Pioneer G, is a 260-kilogram robotic space probe launched byNASA on April 5, 1973, to study theasteroid belt, the environment around Jupiter and Saturn, solar winds, and cosmicrays.
It was the first probe to encounter Saturn, the second to fly through the asteroid belt, and the second to fly by Jupiter. Later, Pioneer 11 became the second of five artificial objects to achieve an escape velocity allowing it to leave the Solar System.
Due to power constraints and the vast distance to the probe, the last routine contact with the spacecraft was on September 30, 1995, and the last good engineering data was received on November 24, 1995.
Approved in February 1969, Pioneer 11 and its twin probe, Pioneer 10, were the first to be designed for exploring the outer Solar System.
Yielding to multiple proposals throughout the 1960s, early mission objectives were defined as:
-Explore the interplanetary medium beyond the orbit of Mars.
-Investigate the nature of the asteroid belt from the scientific standpoint and assess the belt's possible hazard to missions to the outer planets.
-Explore the environment of Jupiter.
Subsequent planning for an encounter with Saturn added many more goals:
-Map the magnetic field of Saturn and determine its intensity, direction, and structure.
-Determine how many electrons and protons of various energies are distributed along the trajectory of the spacecraft through the Saturn system.
-Map the interaction of the Saturn system with the solar wind.
-Measure the temperature of Saturn's atmosphere and that of Titan, the largest satellite of Saturn.
-Determine the structure of the upper atmosphere of Saturn where molecules are expected to be electrically charged and form an ionosphere.
-Map the thermal structure of Saturn's atmosphere by infrared observations coupled with radio occultation data.
-Obtain spin-scan images of the Saturnian system in two colors during the encounter sequence and polarimetry measurements of the planet.
-Probe the ring system and the atmosphere of Saturn with S-band radio occultation.
-Determine more precisely the masses of Saturn and its larger satellites by accurate observations of the effects of their gravitational fields on the motion of the spacecraft.
-As a precursor to the Mariner Jupiter/Saturn mission, verify the environment of the ring plane to find out where it may be safely crossed by the Mariner spacecraft without serious damage.
Pioneer 11 was built by TRW and managed as part of the Pioneer program by NASA Ames Research Center. A backup unit, Pioneer H, is currently on display in the Milestones of Flight exhibit at the National Air and Space Museum in Washington, D.C. Many elements of the mission proved to be critical in the planning of the Voyager program.
Pioneer 10 and 11 both carry a gold-anodized aluminum plaque in the event that either spacecraft is ever found by intelligent lifeforms from other planetary systems.
The plaques feature the nude figures of a human male and female along with several symbols that are designed to provide information about the origin of the spacecraft.
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 EdwardEmersonBarnard 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.
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.
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.
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.
Joseph de Ca'th Lon and TheGrandma continueenjoying together talking about science.
Joseph likes Astronomy and they have been talking about the greatconjunction of the planets Jupiter and Saturn that has occurred today.
They have visited the GarrafAstronomical Observatory to enjoy this conjunction.
A great conjunction is a conjunction of the planets Jupiter and Saturn, when the two planets appear closest together in the sky.
Great conjunctions occur approximately every 20 years when Jupiter overtakes Saturn in its orbit. They are named great for being by far the rarest of the conjunctions between naked-eye planets.
The spacing between the planets varies from conjunction to conjunction with most events being 0.5 to 1.3 degrees. Very close conjunctions happen much less frequently, though the maximum of 1.3° is still close by inner planet standards: separations of less than 10 arcminutes have only happened four times since 1200, most recently in 2020.
On average great conjunction seasons occur once every 19.859 Julian years (365.25 days). This number can be calculated by the synodic period formula 1/(1/4332.59−1/10759.22) giving c. 7253.46 days -the average frequency of Jupiter overtakingSaturn from the Sun's POV due to the net effect of their 4332.59 and 10759.22-day orbits.
In
practice Earth's orbit size can cause great conjunctions to reoccur up
to some months away from the average time or the time they happen on the
Sun. Since the equivalent periods of other naked eye planet pairs are
all under 27 months this makes great conjunctions the rarest.
Occasionally
there is more than one great conjunction in a season when they occur
close enough to opposition: this is called a triple conjunction, which
is not exclusive to great conjunctions.
The
most recent great conjunction occurred on 21 December 2020, and the
next will occur on 4 November 2040. During the 2020 great conjunction,
the two planets were separated in the sky by 6 arcminutes at their
closest point, which was the closest distance between the two planets
since 1623.
The closeness is the result of one of the three approximately equally spaced
longitude zones where great conjunctions occur shifting into the
vicinity of one of the two longitudes where the two orbits appear to
intersect when viewed from the Sun, which has a point of view similar to
Earth.
The
great conjunction zones revolve in the same direction as the planets at
the rate of approximately one-sixth of a revolution per four centuries
thus creating especially close conjunctions on an approximately
four-century cycle.
More precisely, the location in the sky of each
conjunction in a series should increase in longitude by 16.3 degrees on
average, making one full cycle relative to the stars on average once
every 2,634 years. If
instead, we use the convention of measuring longitude eastward from the
First Point of Aries we have to keep in mind that the equinox
circulates once every c. 25,772 years so longitudes measured that way
increase slightly faster and those numbers become 17.95 degrees and
2,390 years.
The longitudes of close great conjunctions are currently
about 307.4 and 127.4 degrees, in the constellations of Capricornus and
Cancer respectively.
Earth's
orbit can make the planets appear up to about 10 degrees ahead of or
behind when they are at the optimal point, which also is true for any
other part of their orbits.
Saturn's orbit plane is inclined 2.485 degrees relative to Earth's, and Jupiter's is 1.303 degrees.
Interestingly, the ascending nodes of both planets are similar, 100.6 degrees for Jupiter and 113.7 degrees for Saturn, so that if Saturn is above or below Earth's orbital plane Jupiter usually is too, this is partly caused by Earth's orbit being tilted relative to all the large planets.
Because the orbit inclination directions of Jupiter and Saturn align reasonably well it would be expected that no closest approach will ever be much worse than Saturn's orbit tilt (2.485°) minus Jupiter's (1.303°). Indeed, between the year 1 and 3000, the maximum conjunction distances were 1.3 degrees in 1306 and 1940.
Conjunctions in both years occurred when the planets were tilted most out of the plane: longitude 206 degrees (therefore above the plane) in 1306, and longitude 39 degrees (therefore below the plane) in 1940.
When studying the great conjunction of 1603, Johannes Kepler thought that the Star of Bethlehem might have been the occurrence of a great conjunction. He calculated that a triple conjunction of Jupiter and Saturn occurred in 7 BC, −6 using astronomical year numbering.
A triple conjunction is a conjunction of Jupiter and Saturn at or near their opposition to the Sun.
In this scenario, Jupiter and Saturn will occupy the same right ascension on three occasions or same ecliptic longitude on three occasions depending on which definition of conjunction one uses, this is due to apparent retrograde motion and happens within months.
The most recent triple conjunction occurred in 1980 and 1981 while the next will be in 2238 and 2239. Lights in the sky that look like especially bright stars are commonplace. Jupiter & Saturn only appear to be in the same spot for a moment, but they spend weeks approaching and departing from each other.
They are visibly separate, distinct objects for the vast majority of the same evening on which the conjunction occurs, something wise men are not likely to miss. Aside from the 7 BC conjunction occurring at the wrong time, the Star ofBethlehem as described moves west, but makes a sharp turn to the south, a movement no star or planet can actually make.
Great Conjunctions never appear to be leading southward to any particular building in Isreal. Additionally, there are other, better candidates for the StarofBethlehem.
The astronomers from the Cracow Academy, Jan Muscenius, Stanisław Jakobejusz, Nicolaus Schadeck, Petrus Probosczowicze, and others observed the great conjunction of 1563 to compare Alfonsine Tables (based on a geocentric model) with the Prutenic Tables (based on Copernican heliocentrism).
In the Prutenic Tables the astronomers found Jupiter and Saturn so close to each other that Jupiter covered Saturn, actual angular separation was 6.8 minutes on 25 August 1563.
The Alfonsine Tables suggested that the conjunction should be observed on another day but on the day indicated by the Alfonsine tables the angular separation was a full 141 minutes.
The Cracow professors suggested following the more accurate Copernican predictions and between 1578 and 1580 Copernican heliocentrism was lectured on three times by Valentin Fontani.
The great conjunction of 2020 was the closest since 1623 and eighth closest of the first three millennia AD, with a minimum separation between the two planets of 6.1 arcminutes. This great conjunction was also the most easily visible close conjunction since 1226, as the previous close conjunctions in 1563 and 1623 were closer to the Sun and therefore more difficult to see. It occurred seven weeks after the heliocentric conjunction, when Jupiter and Saturn shared the same heliocentric longitude.
The closest separation occurred on 21 December at 18:22 UTC, when Jupiter was 0.1° south of Saturn and 30° east of the Sun. This meant both planets appeared together in the field of view of most small and medium sized telescopes, though they were distinguishable from each other without optical aid.
During the closest approach, both planets appeared to be a binary object to the naked eye. From mid-northern latitudes, the planets were visible one hour after sunset at less than 15° in altitude above the southwestern horizon in the constellation of Capricornus.
The conjunction attracted considerable media attention, with news sources calling it the Christmas Star due to its proximity to Christmas.
We must believe then, that as from hence we see Saturn and Jupiter; if we were in either of the Two, we should discover a great many Worlds which we perceive not; and that the Universe extends so in infinitum.
The Cassini–Huygens mission was a collaboration between NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI) to send a probe to study the planet Saturn and its system, including its rings and natural satellites. The Flagship-class unmanned robotic spacecraft comprised both NASA's Cassini probe, and ESA's Huygens lander which would be landed on Saturn's largest moon, Titan. Cassini was the fourth space probe to visit Saturn and the first to enter its orbit. The craft were named after astronomers Giovanni Cassini and Christiaan Huygens.
Launched aboard a Titan IVB/Centaur on October 15, 1997, Cassini was active in space for more than 18 years, with 13 years spent orbiting Saturn, studying the planet and its system after entering orbit on July 1, 2004. The voyage to Saturn included flybys of Venus, Earth , the asteroid 2685 Masursky, and Jupiter.
Its mission ended on September 15, 2017, when Cassini was commanded to fly into Saturn's upper atmosphere and burn up, in order to prevent any risk of contaminating Saturn's moons, some of whose environments could potentially bear life, with stowaway terrestrial microbes.
The Cassini–Huygens
The mission is widely perceived to have been successful beyond expectation. Cassini-Huygens has been described by NASA's Planetary Science Division Director as a mission of firsts, that has revolutionized human understanding of the Saturn system, including its moons and rings, and our understanding of where life might be found in the Solar System.
Cassini's original mission was planned to last for four years, from June 2004 to May 2008. The mission was extended for another two years until September 2010, branded the Cassini Equinox Mission. The mission was extended a second and final time with the Cassini Solstice Mission, lasting another seven years until September 15, 2017, on which date Cassini was de-orbited by being allowed to burn up in Saturn's upper atmosphere.
The Huygens module traveled with Cassini until its separation from the probe on December 25, 2004; it was successfully landed by parachute on Titan on January 14, 2005. It successfully returned data to Earth for around 90 minutes, using the orbiter as a relay. This was the first landing ever accomplished in the outer Solar System and the first landing on a moon other than our own. Cassini continued to study the Saturn system in the following years.
Landed on Saturn's largest moon Titan
At the end of its mission, the Cassini spacecraft executed the Grand Finale of its mission: a number of risky passes through the gaps between Saturn and Saturn's inner rings.
The purpose of this phase was to maximize Cassini's scientific outcome before the spacecraft was destroyed. The atmospheric entry of Cassini effectively ended the mission, although data analysis and production will continue afterwards.
Until September 2017 the Cassini probe continued orbiting Saturn at a distance of between 8.2 and 10.2 astronomical units from the Earth. It took 68 to 84 minutes for radio signals to travel from Earth to the spacecraft, and vice versa. Thus ground controllers could not give real-time instructions for daily operations or for unexpected events. Even if response were immediate, more than two hours would have passed between the occurrence of a problem and the reception of the engineers' response by the satellite.
I was astonished first time I saw it. It was like a big fired arrow crossing the starred sky.
I felt very small in the middle of our unknown Universe.
My interest in Astronomy is old, since I was a teenager. I have always had an incredible feeling to look up into the sky.
The sky is a big map and we can find past answers, present mysteries and it will be a useful guide for the future generations.
Joseph de Ca'th Lon, New Mexico, 1995
Comet Hale–Bopp, formally designated C/1995 O1, is a comet that was perhaps the most widely observed of the 20th century, and one of the brightest seen for many decades.
Joseph and Hale-Bopp in Cairo
Hale–Bopp was discovered on July 23, 1995 separately by Alan Hale and Thomas Bopp prior to it becoming naked-eye visible on Earth.
Although predicting the maximum apparent brightness of new comets with any degree of certainty is difficult, Hale–Bopp met or exceeded most predictions when it passed perihelion on April 1, 1997.
It was visible to the naked eye for a record 18 months, twice as long as the previous record holder, the Great Comet of 1811.
Accordingly, Hale–Bopp was dubbed the Great Comet of 1997.
Hale had spent many hundreds of hours searching for comets without success, and was tracking known comets from his driveway in New Mexico when he chanced upon Hale–Bopp just after midnight. The comet had an apparent magnitude of 10.5 and lay near the globular cluster M70 in the constellation of Sagittarius.
Joseph and Hale-Bopp over Indian Cove, 2013
Hale first established that there was no other deep-sky object near M70, and then consulted a directory of known comets, finding that none were known to be in this area of the sky.
Once he had established that the object was moving relative to the background stars, he emailed the Central Bureau for Astronomical Telegrams, the clearing house for astronomical discoveries.
Bopp did not own a telescope. He was out with friends near Stanfield, Arizona observing star clusters and galaxies when he chanced across the comet while at the eyepiece of his friend's telescope. He realized he might have spotted something new when, like Hale, he checked his star maps to determine if any other deep-sky objects were known to be near M70, and found that there were none. He alerted the Central Bureau for Astronomical Telegrams through a Western Union telegram.
Brian G. Marsden, who had run the bureau since 1968, laughed, Nobody sends telegrams anymore. I mean, by the time that telegram got here, Alan Hale had already e-mailed us three times with updated coordinates.
The following morning, it was confirmed that this was a new comet, and it was given the designation C/1995 O1. The discovery was announced in International Astronomical Union circular 6187.
Hale–Bopp's orbital position was calculated as 7.2 astronomical units (AU) from the Sun, placing it between Jupiter and Saturn and by far the greatest distance from Earth at which a comet had been discovered by amateurs.Most comets at this distance are extremely faint, and show no discernible activity, but Hale–Bopp already had an observable coma.
Joseph and Comet Hale-Bopp over Lake Mono
An image taken at the Anglo-Australian Telescope in 1993 was found to show the then-unnoticed comet some 13 AU from the Sun, a distance at which most comets are essentially unobservable. Analysis indicated later that its comet nucleus was 60±20 kilometres in diameter, approximately six times the size of Halley.
Its great distance and surprising activity indicated that comet Hale–Bopp might become very bright indeed when it reached perihelion in 1997. However, comet scientists were wary, comets can be extremely unpredictable, and many have large outbursts at great distance only to diminish in brightness later. Comet Kohoutek in 1973 had been touted as a 'comet of the century' and turned out to be unspectacular.
The comet likely made its previous perihelion 4,200 years ago, in July 2215 BCE. The estimated closest approach to Earth was 1.4 AU, and it may have been observed in ancient Egypt during the 6th dynasty reign of the Pharaoh Pepi II (Reign: 2247 - c.2216 BCE).
Pepi's pyramid at Saqqara contains a text referring to an "nhh-star" as a companion of the pharaoh in the heavens, where "nhh" is the hieroglyph for long hair.
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