Tag: Brief Encounter

Brief Encounter With Pluto

Brief Encounter With Pluto

A brief encounter with Pluto.  On July 14 2015,  the New Horizons Spacecraft flew past our most distant planet, Pluto.  A truly historic moment in space travel.

Pluto is an a staggering 4.67 million miles (7.5 billion kilometres) from our home planet  earth.

Light & the signals from  New Horizons speeding to us  at  186,000(approx 3000 kms) per second  take over four hours to reach earth!

Here are some of the amazing photos…

pluto-charonPluto and it’s major moon Charon

pluto-mountain-range Close up of Pluto’s ice plain & mountainsPluto-REX-v3 near fly by of Pluto


Pluto was regarded as the most distant planet in our solar system after its discovery in 1930 at the Percival Lowell observatory. Urbain Le Verrier in the 1840s, using celestial  mechanics produced by Isaac Newton,   predicted the position of the then-undiscovered planet Neptune  after he had  analysed perturbations in the orbit of Uranus. Further observations of Neptune in the late 19th century made  astronomers speculate that Uranus’ orbit was being disturbed by another planet besides Neptune. In 1906,  a wealthy Bostonian Percival Lowell who had  founded the Lowell  Observatory in Flagstaff, Arizona later becoming famous for early detailed observations of Mars. From the observatory  Lowell began an extensive project in search of what was causing the perturbation, a possible ninth planet, which he termed ” Planet X“.

A young astronomer/researcher at the observatory,  Clyde Tombaugh  had the task  to systematically image the night sky in pairs of photographs taken two weeks apart, then examine each pair and determine whether any objects had shifted position. He  used a blink comparator,  a viewing apparatus used by astronomers to find differences between two wide field  photographs  of the night sky taken through optical telescopes. The blink comparator permitted rapidly switching from viewing one photograph to viewing the other, “blinking” back and forth between the two taken of the same area of the sky at different times. This allowed the user to easily spot objects in the night sky that had changed position.  On 23 January 1930, using the comparator on two photo plates, Clyde discovered the illusive planet X. As discoverer  the Lowell observatory could name this new planet  but as the discovery was world-wide news , suggested names were submitted.

A 11 year old English schoolgirl Venetia Burney from Oxford proposed the  name Pluto. She  was interested in classical mythology as well as astronomy and thought that the god of the underworld was an appropriate name for such a remote, dark and cold world.  This name was submitted to  Lowell. The object was officially named on March 24, 1930 Each member of the Lowell Observatory was allowed to vote on a short-list of three: Minerva (which was already the name for an asteroid), Cronus  and Pluto. Pluto received every vote.  The name was announced on May 1, 1930.Upon the announcement, Venetia received  five pounds (£5) (£234 as of 2012), as a reward. The choice of name was partly inspired by the fact that the first two letters of Pluto are the initials of Percival Lowell, and Pluto’s astronomical symbol (♇) is a monogram constructed from the letters ‘PL’.

Science history books have been recently amended with Pluto being ( I think unfairly) downgraded  to a minor planet and  just one member of the Kuiper Belt objects, a  field containing  primordial  debris  that are remnants from the creation of the solar system. The Kuiper Belt circles the outer solar system. This debris varies in size and  as telescope power improved,  objects as large as Pluto have been discovered within the belt and the  question of Pluto being classed as proper planet has been raised by the International Astronomical Union (IAU) .  This meant instead of the 9 planets in our solar system, we have now only the 8 ones being Mercury, Venus Earth, Mars, Jupiter, Neptune, Uranus and Saturn.

In 2002, the KBO 5000 Quaor was discovered, with a diameter then thought to be roughly 1280 kilometres, about half that of Pluto. In 2004, the discoverers of 90377 Sedna placed an upper limit of 1800 km on its diameter, nearer to Pluto’s diameter of 2320 km,  although Sedna’s diameter was revised downward to less than 1600 km by 2007. , it was argued, Pluto should be reclassified as one of the Kuiper belt objects. On July 29, 2005, the discovery of a new trans-Neptunian object named Eris was found  be approximately the same size as Pluto. This was the largest object discovered in the Solar System since Neptune’s giant moon Triton in 1846. Its discoverers and the press initially called it the tenth planet , although there was no official consensus at the time on whether to call it a planet.  Others in the astronomical community considered the discovery the strongest argument for reclassifying Pluto as a minor planet. The debate on Pluto’s came to a head in 2006 with an IAU resolution that created an official definition for the term “planet”. According to this resolution, there are three main conditions for an object to be considered a ‘planet’:

  1. The object must be in orbit around the Sun.
  2. The object must be massive enough to be a sphere by its own gravitational force. More specifically, its own gravity should pull it into a shape of hydrostatic equilibrium (the condition in fluid mechanics where a volume of a fluid is at rest or at constant velocity. This occurs when compression due to gravity y is balanced by a pressure gradient force] e.g.  the pressure gradient force prevents gravity from collapsing the Earth;s atmosphere into a thin, dense shell, while gravity prevents the pressure gradient force from diffusing the atmosphere into space).
  3. It must have cleared the neighbourhood  around its orbit, that there are no comparable objects within the planet’s orbit.

Pluto fails to meet the third condition, since its mass is only 0.07 times that of the mass of the other objects in its orbit (Earth’s mass, by contrast, is 1.7 million times the remaining mass in its own orbit Controversy still rages at Pluto’s demotion to minor planet and reclassified in the new dwarf planet  Plutoid category of trans-Neptunian objects. In 2006, NASA launched the New Horizons spacecraft to visit Pluto, it is now past  halfway between Earth and Pluto, on approach for a dramatic flight past the icy planet and its moons in July 2015. Fittingly,  the spacecraft contains ashes from the cremated remains of Clyde Tombaugh who passed away in 1997.

Photo plates used in the blink comparator  showing an object  shown
with a pointer (Planet X) that moved over six nights against the  background of more fixed stars  and confirmed as a new planet later named Pluto.

Pluto and its moons: Hubble Space Telescope.


Ralph: Visible and infrared imager/spectrometer; provides color, composition and thermal maps.


Alice: Ultraviolet imaging spectrometer; analyzes composition and structure of Pluto’s atmosphere and looks for atmospheres around Charon and Kuiper Belt Objects (KBOs).


REX: (Radio Science EXperiment) Measures atmospheric composition and temperature; passive radiometer.


LORRI: (Long Range Reconnaissance Imager) telescopic camera; obtains encounter data at long distances, maps Pluto’s far side and provides high resolution geologic data.


SWAP: (Solar Wind Around Pluto) Solar wind and plasma spectrometer; measures atmospheric “escape rate” and observes Pluto’s interaction with solar wind.


PEPSSI: (Pluto Energetic Particle Spectrometer Science Investigation) Energetic particle spectrometer; measures the composition and density of plasma (ions) escaping from Pluto’s atmosphere.


SDC: (Student Dust Counter) Built and operated by students; measures the space dust peppering New Horizons during its voyage across the solar system.

New Horizons is powered a single radioisotope thermoelectric generator (RTG), which transforms the heat from the natural radioactive decay of plutonium dioxide into electricity. The compact, rugged General Purpose Heat Source  developed and provided by the U.S. Department of Energy, carries approximately 11 kilograms (24 pounds) of plutonium dioxide fuel. It provides about 200 watts of power.

Assembly of New Horizons









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