June 22 – Discovery of Pluto’s Moon, Charon (1978)

Pluto‘s biggest moon, Charon, was discovered on June 22nd, 1978 by American astronomer James W Christy at the United States Naval Observatory.

Until recently, Charon, like Pluto, was mostly a collection of blurry smudges on photographic plates, but thanks to the 2015 flyby of NASA’s New Horizons mission, they both suddenly got a lot closer.

 

True colour image of Charon (Image credit: NASA New Horizons).

At just over 1,000 km wide, Charon is quite small.  But because Pluto is also rather diminutive, Charon has a much greater effect on its host than the average satellite, particularly regarding the location of their barycentre, or the point in space about which their two-body system orbits.   Whereas the effect of our own Moon is only enough to move the barycentre slightly away from the centre of the Earth and produce a small “wobble” because the relative masses of the two bodies are so different, Charon is so big relative to Pluto that they orbit a point well outside the surface of Pluto.  This has led some to argue that the Pluto-Charon system should be considered as a binary system, rather than a dwarf planet/moon arrangement.

 

Charon up close (image credit: NASA New Horizons).

Charon’s orbit of Pluto is almost completely circular, with an eccentricity of 0.0002 (our Moon’s is a distinctly wonky 0.05, and Pluto’s eccentricity with regard to the Sun is a positively inebriated 0.25).  So the distance of Charon from Pluto can therefore be said to be the same all the time if you round to the nearest kilometre, 17,536. On Pluto there would be no media frenzy for the next “Super Charon”).

Pluto and Charon from just under 4 million miles (6m km). Image:NASA New Horizons

Charon is named after the ferryman who the Greeks needed to pay to take their dead to the underworld (ruled by Hades, or Pluto to the Romans).  Charon was one of the old “primordial” gods of Greek mythology. His father, Erebus, was the personification of darkness, which probably gave him a head start for landing a job in the underworld.

Caron and some guests, as depicted by Ukrainian artist Alexander Dmitrievich Litovchenko

 


 

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November 28 – KBO 20000 Varuna

We hurtle way beyond the asteroid belt today, for a change, to celebrate the discovery of 20000 Varuna, first spotted for what it is on November 28th 2000 by Robert S Macmillan, despite appearing on photographic plates dating back to the 1950s.

Varuna is a fairly large classical Kuiper belt object (KBO). Estimates of its size vary widely from 600 to 1000km, but even if it turns out to be at the lower end, it still ranks highly in the KBO pecking order.

Varuna has a very rapid rotation (6.34 hours) and a double-peaked light curve. it is thought to be an elongated spheroid,  about half as wide again across the equator as from pole to pole.

Varuna pacifying Sri Rama.
Varuna pacifying Sri Rama.

The Hindu deity Varuna, after whom this particular oblate spheroid is named, has similar qualities to the Roman god Neptune, making it a good choice for what at the time was the largest known trans-Neptunian object.


Asteroid 235 Carolina was also discovered today, in 1883.  It is one of Johann Palisa‘s collection of 122 asteroids, and came while he was going through (by his standards) a dry patch in his rock hunting career.  Having discovered nine in 1882, he “only” managed two in 1883, before hitting his stride again in 1884 with six.  Part of the reason for this relative scarcity was probably that Palisa spent a good portion of the year 1883 travelling to watch a total solar eclipse.  The spot chosen for the expedition was near to Tahiti, in the chain of coral atolls known as the Line Islands.  More specifically . . . .

Caroline Island, Kiribati (image credit: NASA)
Caroline Island, Kiribati (image credit: NASA)

 

November 14 – The White Stuff

The first American to walk in space, Edward Higgins “Ed” White, was born on November 14th 1930, in San Antonio, Texas.

The son of a distinguished USAF major general, it was probably obvious from an early age that flying would figure big in his career, and after graduating from West Point in 1952 he joined the Air Force as a 2nd Lieutenant.  After a spell at Bitburg Air Force Base in West Germany, he gained a masters degree in aeronautical engineering and became a test pilot at Wright-Patterson AFB near Dayton, Ohio, rising to the rank of lieutenant colonel.

Lt Col Edward White (image credit: NASA)
Lt Col Edward White (image credit: NASA)

White was part of NASA’s 1962 second group of nine astronauts, and was quickly chosen to be the pilot of Gemini 4, and the first American to conduct an EVA (extra-vehicular activity) on June 3rd, 1965.  I have to add the word “American” because, as with so many firsts in the space race, the Russians had just pipped them to the post with Alexey Leonov, who spent 12 minutes outside the Voskhod 2 spacecraft, on March 18th.  Unsurprisingly, White had to be ordered back inside his craft from the ground, as he was reluctant to end the experience.

Ed White having the time of his life. (Image credit: NASA.)
Ed White having the time of his life. (Image credit: NASA.)

At the start of the Apollo program, White was a fairly obvious choice to be part of the first manned flight, but on February 21st, 1967, when he, along with Gus Grissom and Roger Chaffee, entered Apollo 1 for a launch rehearsal, three weeks before the planned launch date, a fire broke out in the cabin, killing all three.


1969  ⇒  Launch of Apollo XII, the second manned Moon landing (Conrad, Bean and Gordon).


2003  ⇒  Discovery of trans-Neptunian object 90377 Sedna by  Mike Brown, Chad Trujillo, and David Rabinowitz, using the Palomar Quest camera.


 

January 05 – Eris

Dwarf planet Eris is the largest known member of a collection of objects known as thescattered disc, a subset of the larger group, the trans-Neptunian objects (TNOs).  It was discovered by a team from Palomar Observatory on January 5th 2005, and was given the “minor planet designation” of 136199.  Eris has a larger mass than Pluto by about 27% (and was partly responsible for the reclassification of Pluto by the IAU as a dwarf planet), making it the ninth most massive object orbiting the Sun.

Eris - Troublemaker
Eris – Troublemaker

Eris, and its moon Dysnonia, are a very long way away.  They orbit in a wild ellipse ranging from 38 to 97 AU from the Sun (about three times farther away than Pluto).

Eris has an appropriate name.  In Greek mythology she was the goddess of chaos and discord.  Inhabitants of Pluto, if they exist, would surely agree.


1969  –  Launch of the USSR’s Venus atmospheric probe Venera 5 from Baikonur Cosmodrome in Kazakhstan.  It reached its target on May 16th, and sent back data for almost an hour while descending by parachute through the Venusian atmosphere.