This story first of all talks about a couple of constellations, named after two Greek gods which almost certainly you will have heard of: HERCULES, and PLUTO. The name Pluto was much more recently given to the last of our planets to be discovered. This was in 1930, and recently some fascinating details about this planet have been revealed for the first time.
You might be able to see the Hercules constellation in winter if you’re away from street lights, even though it doesn’t have any really bright stars: the thing to look for is a big square of stars as shown in this photo.
Part of this constellation is a group of stars that at one time were regarded as a separate constellation, called CERBERUS. In Greek and Roman mythology, it was depicted as a three-headed dog, sometimes with the claws of a lion, or the tail of a serpent:
and sometimes the dog’s hair was represented by a three-headed snake that Hercules could grab hold of -
So whose dog was Cerberus? In Greek mythology, one of the brothers of Zeus (actually the father of Hercules) was Hades but his Roman name was PLUTO. He was the owner of this fearsome dog. Cerberus was always employed as Pluto’s loyal watchdog and guarded the gates that granted access and exit to the underworld, to prevent the dead from escaping and the living from entering. Hercules had killed his wife and his sons after he had been driven mad by Hera, the queen of the gods. After recovering his sanity, Hercules deeply regretted his actions; and travelled to Delphi to visit the oracle, considered to be the most influential source of wisdom throughout ancient Greece, and a way communicate “directly” with Greek gods. Hercules asked how he could atone for his actions. He was told to perform twelve tasks requiring his immense strength: these are known as the twelve labours of Hercules. In the last of these, his twelfth labour, he went down to the underworld and asked Pluto’s permission to bring Cerberus to the surface. Pluto agreed on condition that Hercules could overpower the beast without using weapons.
it was this kneeling position of Hercules when praying to his father Zeus that gave him the name "the Kneeler". Here is a painting of Pluto and Cerberus. I think they both look very ugly:
Because Pluto was the god of the underworld, he owned all the precious metals mined from the earth. He was known as the pitiless king of the dead, because if mortals entered his underworld they could never hope to return.
There is a dwarf planet, named after Pluto. That name was chosen because being even further from the sun than Neptune, it is extremely cold and inaccessible, which is how the Ancients regarded Pluto’s kingdom of the underworld.
Most true planets go round the sun in a neat circle. Pluto’s orbital characteristics are substantially different from those of the others, which follow nearly circular orbits around the Sun close to the flat reference plane called the ecliptic. In contrast, Pluto's orbit is highly inclined relative to the ecliptic (over 17°) and highly eccentric (elliptical). Thus as shown in the diagram, this means that for part of its year, its orbit (shown in red) brings it closer to the sun than the next furthest planet (Neptune, with orbit shown in blue). Until recently, very little was known about Pluto and many experts were tempted by the prospect of sending a space probe to find out what Pluto was like. This didn’t at first seem to be a practical possibility, as such a probe would taken nearly ten years to get there.
However, one research team were encouraged by the fact that in the period 2000-2003, NASA had launched a number of competitions in which proposals for funding could be submitted under what was called the “New Frontiers Program”. The team decided to work out and submit a proposal called New Horizons, and this was selected as one of two finalists to be subject to a three-month concept study, in June 2001. Its primary mission was to perform a flyby study in 2015 of the geology and morphology of Pluto and its moon Charon, map their surface composition, and to analyze Pluto's atmosphere.
In November 2001, New Horizons was officially selected for funding as part of the New Frontiers program. However, during the Bush administration, New Horizons was effectively cancelled by not being including it in NASA's budget for 2003. An intense campaign to gain support for New Horizons was being launched. One of the New Horizons co-investigators, later the leader of the plasma investigations team, came up with arguments that helped to place New Horizons top of the list of projects considered the highest priority among the scientific community in the medium-size category of the prioritized "wish list“. This list was compiled by the USA’s National Research Council, reflecting the opinions of the scientific community.
The name of that co-investigator was Fran Bagenal. In 1976, as an undergraduate student in physics at Lancaster University in England, when asked about her ideas for a career she replied that her ambition was to be the first woman in space. Well, she didn’t manage that, but she is now a professor in the USA based at the University of Colorado, Boulder.
This resulted in funding for the mission finally being secured, and a start was made on building the spacecraft and its instruments, with a planned launch in January 2006 and arrival at Pluto in 2015.
After the Jupiter encounter, New Horizons sped toward the Kuiper Belt, and was put in hibernation mode starting June 28, 2007. During hibernation, most major systems of New Horizons were deactivated and revived only about two months every year. On Dec. 6, 2014, ground controllers revived New Horizons from hibernation for the last time to initiate its active encounter with Pluto. In 2015, on the national day of France (July 14th), the machine that had been rocketed off to Pluto more than nine years before, got there at last! flying about 7,800 kilometers above the surface of Pluto.
By the time it reached the Pluto system, the spacecraft had travelled farther away and for a longer time period (more than nine years) than any previous deep space spacecraft ever launched.
Photographic observations of Pluto, and other scientific measurements, began five months before the closest approach, and continued for at least a month after the encounter. This involved sending back signals at the speed of light, which from Pluto took four hours and 25 minutes to reach Earth from the spacecraft.
This is Pluto’s receding crescent as seen by New Horizons at a distance of 200,000 kilometers. The spectacular blue haze is a photochemical smog resulting from the action of sunlight on methane and other molecules in Pluto's atmosphere. These hydrocarbons accumulate into small haze particles, which scatter blue sunlight—the same process that can make haze appear bluish on Earth.
Spectroscopic data tell us that the flat regions are more than 98% nitrogen ice, with traces of methane and carbon monoxide. A large flat basin, thought to have been formed by an impact, appears to carry floating blocks of water ice crust and has no visible craters, indicating that its surface is less than 10 million years old.That impact probably resulted in liquid water upwelling from below, implying the existence of a subsurface ocean at least 100 km deep. Thus Pluto may have been habitable when it was first formed!
Pluto’s surface is characterised by mountains, valleys, plains and craters. The temperature can be as cold as 30 degrees above absolute zero. The tallest mountains are 6,500 to 11,000 feet high; they are big blocks of water ice, sometimes with a coating of frozen methane gas.
Pluto has a complex collection of satellites, which is intriguing given how small this dwarf planet is: about 2,400 kilometres in diameter. Its moon Charon was confirmed to be about 1,200 kilometres in diameter. The entire moon system is believed to have formed by a collision between Pluto itself and another Kuiper Belt object early in the history of the solar system. The collision flung material that coalesced into the family of satellites observed around Pluto. The moons form a series of neatly nested orbits, a bit like Russian dolls.
The known moons of Pluto are:
•Charon: Discovered in 1978, this small moon is almost half the size of Pluto. It is so big Pluto and Charon are sometimes referred to as a double planet system.
•Nyx and Hydra: These small moons were found in 2005 by a Hubble Space Telescope team studying the Pluto system.
•Kerberos: Discovered in 2011, this tiny moon is located between the orbits of Nix and Hydra.
•Styx: Discovered in 2012, this little moon was found by a team of scientists searching for potential hazards to the New Horizons spacecraft Pluto flyby in July 2015.
As New Horizons continues its secondary mission, flying through the Kuiper belt for months or even years more, it will indue course pass into what is termed the Oort Cloud:
The Oort cloud is an even more distant spherical region of icy, comet-like bodies that surrounds the solar system, including the Kuiper Belt. Some of these bodies can take anything up to a million years or more to orbit the sun, unless disrupted by a near-collision, to be sent plunging down to shine in our sky as a comet! The mission is expected to end in the mid-2030s, but by 2038, if still functioning, the probe will explore the outermost layer of the sun’s atmosphere, known as the heliosphere, a vast, bubble-like region that is is continuously "inflated" by the solar wind originating from the Sun. Beyond that, who knows what the probe might come across in interstellar space?
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