January 19 – Launch of New Horizons (2006)

We have two quick asteroids to start us off today.  Asteroid 502 Sigune was discovered on January 19th 1903 by old hand Max Wolf at Königstuhl Observatory near Heidelberg.  On the same day, young whippersnapper Raymond Smith Dugan, also working at Heidelberg, discovered the second asteroid of his career, 503 Evelyn (named after his mother).


On January 19th 2006, NASA launched the New Horizons probe to Pluto, so long ago it was still a planet at the time (and always will be for some of us).  I clearly remember thinking back then that it was going to take such a long time to arrive that I’d probably have forgotten all about it, but here we are more than a decade later and the visit is now on the cusp of becoming a fond and fading memory.

New Horizons (image credit: NASA)
New Horizons (image credit: NASA)

New Horizons was a fairly large program by today’s standards, costing about $650m, which sounds expensive, but it’s actually only about $5 per US taxpayer, and spread over the 15 years of the project it’s a mere 33 cents a year: a bargain!  The mission has also visited Jupiter, and once Pluto had been passed there was a rendezvous with a Kuiper Belt Object in 2019.  The object chosen didn’t have a particularly catchy name at the time (2014 MU69), and was apparently also known in New Horizons circles as PT1 (and yes, it did stand for “Potential Target”).  PT1 later got the nickname Ultima Thule (it’s two planetesimals stuck together with one name each) but is now officially named 486958 Arrokoth.  From a typing point of view I think I prefer PT1.

The Jupiter flyby, as well as being a scientific mission in its own right, and a useful testing-ground for the instrumentation before an extended period of hibernation for the long journey to Pluto, was used to increase the speed of New Horizons by “gravity assist” to 9,000 miles per hour.  I think I’ll have to get myself one.  At that speed I could travel across the Atlantic to visit my friend Joanne in Arizona in about 20 minutes.

During the visit to Jupiter, New Horizons imaged the moon Callisto, and studied Jupiter’s ring system, magnetosphere, and the atmospheric conditions on the planet.

Calisto from New Horizons (image credit: NASA)
Calisto from New Horizons (image credit: NASA)

Scientific instruments on New Horizons are under the command of the Clyde Tombaugh Science Operations Centre in Colorado, and a small quantity of the ashes of the centre’s namesake, the man who discovered Pluto in February 1930, have been sent along for the ride.  Tombaugh died on January 17th 1997.

Imaging of Pluto using New Horizons LORRI imager began in January 2015. Hundreds of photographs were taken of the Pluto system, enabling navigators to fine tune Pluto’s exact position, and calculate the precise distance between New Horizons and its target.

And at the time we thought these images were pretty impressive; but they were nothing compared to what we got when the Pluto system was finally reached.

 

Pluto from the New Horizons probe (image credit: NASA/APL/SwRI)
Pluto from the New Horizons probe (image credit: NASA/APL/SwRI)
Surface detail of Pluto from New Horizons (image credit: NASA)
Surface detail of Pluto from New Horizons (image credit: NASA)
Pluto (image: NASA)
Pluto (image: NASA)
Charon (image: NASA)
Charon (image: NASA)
Nix (image: NASA)
Nix (image: NASA)

See what I mean?


1747Birth of Johann Elert Bode in Hamburg. The “law” named after Bode uses a formula to predict the distances of the planets from the Sun. It’s great for the first six, and was hailed a success when Uranus (a name suggested by Bode) was found in the right place. Unfortunately, the existence of the asteroid belt and Neptune were not part of the plan. Bode has a comet, an asteroid (998 Bodea) and a galaxy (M81, Bode’s Galaxy) named after him (though I suspect any inhabitants of M81 might disagree).


1965Launch of Gemini 2 from Cape Canaveral. This was an unmanned flight, but it did include a practice ingress (clambering in) and egress (being pulled out) by crewmembers of Gemini 3. Following two occasions on which the launch assembly had to be dismantled (for hurricanes Cleo and Dora) and an aborted launch on December 9th, 1964, the eighteen minute flight took place on the morning of January 19th, 1965, and was only slightly inconvenienced by a power outage at Mission Control caused by the electricity demands of the television coverage.


 

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