February 18 – Discovery of the “Planet” Pluto (1930)

I feel sorry for Pluto. When I was younger it was the ninth biggest planet in the solar system, but unfortunately is now (probably) only the second biggest “dwarf planet” following the discovery of minor-planet 136199 Eris by the Palomar Observatory on January 5th 2005. This discovery encouraged an acceleration of the debate over whether or not Pluto should ever have been called a planet, the result being that the IAU published their Definition of a Planet in the Solar System on August 24th 2006. So I suppose that’s the day on which Pluto stopped being a planet, and became a Kuiper Belt Object. And as if that weren’t damage enough for Pluto’s image, there is still a debate going on as to whether Pluto and Charon should be re-classified as a binary system. At the moment Charon is a moon of Pluto; but the centre of their combined mass doesn’t lie within either body, so strictly speaking it should get higher billing.

On the upside, Pluto does get its own Disney character, and lends its name to both plutoids (anything beyond the orbit of Neptune that has managed to attain a roughly spherical shape) and plutinos (anything in the above group that orbits the Sun twice in the same time it takes Neptune to make it round three times).

Pluto was discovered on February 18th 1930 by Clyde Tombaugh from Illinois. Tombaugh was a prolific discoverer of variable stars, and also of asteroids, many of which he found while searching for Pluto. But Pluto will always be his claim to fame, and following his death in 1997 a small quantity of his ashes were sent on their way out there aboard the New Horizons probe, which arrived at the ex-planet on July 14th 2015 to a blaze of publicity, and began sending back fabulous snapshots.

Pluto from the New Horizons probe (image credit: NASA/APL/SwRI)
Pluto from the New Horizons probe (image credit: NASA/APL/SwRI)

And not before time, as you can see from the second photograph (below); because close-ups of Pluto from the enormous distance of the Earth don’t reveal a great deal of detail.

Pluto and Charon (image: NASA)
Pluto and Charon, pre-New Horizons (image: NASA)

As well as the aforementioned Charon, Pluto has four other moons: Nix, Hydra, Kerberos and Styx. All moons of Pluto are named in accordance with the convention that they are mythological, and have some association with their parent (Hydra, for example, was the nine-headed guardian of an entrance to the underworld).

Surface detail of Pluto from New Horizons (image credit: NASA)
Surface detail of Pluto from New Horizons (image credit: NASA)

As I just mentioned, Pluto is a Kuiper Belt object (KBO). The Kuiper belt, (rhymes with sniper, not kipper, although I have to admit that I do find the concept of a kipper belt rather appealing) or, to give it its full name the Edgeworth-Kuiper Belt, stretches from about 30 to 50 AU from the Sun, and contains an enormous number of mostly smallish bodies (trans-Neptunian Objects, or TNOs) left over from the formation of the Solar System.

A Selection of KBOs (image: NASA)
A Selection of KBOs (image: NASA)

Why Edgeworth gets edged out in popular literature while Kuiper gets the kudos is something I might know more about by the time his birthday comes around (Feb 26th, 1880). Neither of them correctly predicted what the belt was like anyway, so it’s anybody’s guess.

Anyhoo, there are thought to be as many as 100,000 TNOs within the belt with a diameter of over 100km (which is why I say “smallish” not “small”) and, because Pluto is now a member, everybody knows the name of at least one.

Results from New Horizons are changing our view of Pluto for ever. It now see that a crust of water ice might be acting in place of a bedrock, supporting mountains made of frozen nitrogen and methane. It also seems that Pluto might, somehow, be still geologically active. We need to visit again!


February 18th, 1977 was the day on which the space shuttle Enterprise made her first “attached” flight. Strictly speaking, I suppose, this wasn’t the maiden flight of a shuttle, as Enterprise was securely strapped to the back of a specially adapted Boeing 747 for the duration. I now know that she didn’t have any engines or a heat shield, and was therefore incapable of actually flying in space, but at the time I was young(er), and mightily impressed (and it was the first time a shuttle’s wheels had been higher than the hangar roof, so it counts). I was even more impressed when Enterprise was flown, again attached to the 747, over the family home at Brown Edge, Staffordshire, six years later as part of a promotional tour of Europe, drumming up satellite launching business for NASA.


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.


 

November 28 – Discovery of KBO 20000 Varuna (2000)

We hurtle way beyond the asteroid belt today, for a change, to celebrate the discovery of TNO (or KBO) 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 varied widely at the time of discovery from 600 to 1000km. More recent calculations seem to be bringing it down to the lower end of that range, but it still ranks highly in the KBO pecking order.

Varuna has a very rapid rotation (one full turn every 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.

A recent report in Astrophysical Journal Letters (883 (1)) suggests the possibility of a close-in satellite orbiting Varuna, but there’s nothing conclusive, so we will have to wait and see.

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)

October 20 – Discovery of 148780 Altjira (2001)

As you can probably tell from the large number in front of its name, 148780 Altjira was discovered a considerable time later than most of the other small and medium-sized solar system bodies littering these pages (October 20th, 2001), but it gets a mention for a couple of reasons. Firstly, Altjira is a binary system of almost equally sized partners, comprising a primary object of something approaching 160 to 180 km diameter, and a secondary only a little less wide (probably about 140km) discovered six years later. Between them they comprise a classical Kuiper Belt object (KBO) also known as a cubewano, a name derived from the first such object discovered, (15760) 1992 QB1.

Arrernte performing a welcoming dance for strangers, Alice Springs, 1901.
Arrernte performing a welcoming dance for strangers, Alice Springs, 1901.

The second reason I thought this particular KBO deserved a mention was because I believe it’s the only time I’ll be referring to Aboriginal Australian mythology. Altjira is a sky god of the Aranda (or Arrernte) people of the Northern Territory, and is is credited with creating the Earth during the Dreamtime.

Altjira was discovered using the Deep Ecliptic Survey at Kitt Peak Observatory in Arizona, a very successful project to find KBOs, which, between 1998 and 2005, produced the first Neptune Trojan and the first binary trans-Neptunian object (TNO), as well as dozens of centaurs and a couple of hundred classical KBOs.


ALSO TODAY:
1962 – Launch of Kosmos 11 (aka DS-A1 No.1) by the Soviet Union, using a Vostok 2 rocket, on October 20th, 1962, from the Mayak Launch Complex. The purpose of the “DS” missions was to test various hardware, primarily concerned with the development of anti-ballistic missile defence systems. The “DS” in the name stands for Dnepropetrovsk Sputnik. Dnipropetrovsk is the third largest city in Ukraine. Kosmos 11 managed to stay in orbit until May 18th, 1963.


September 22 – Discovery of Asteroid 57 Mnemosyne (1859)

Discovered on this very day in 1859 by Robert Luther, 57 Mnemosyne is a main belt asteroid of about 113km across, sweeping round the Sun at 16.7km/s,  and taking about five and a half years to complete one orbit. Mnemosyne is a stony “S” type asteroid, with an albedo of 0.215. S types are generally brighter than most, with Iris able to reach +7.0 at opposition.

Mnemosyne was a titaness (a daughter of Uranus and Gaia),  and was mother of the nine Muses (Zeus was the father, and somehow managed to persuade Mnemosyne that they needed to sleep together for nine nights to get the job done).

It is from Mnemosyne that we get the word mnemonic.


1862  –  Asteroid 75 Eurydike discovered by C H F Peters.

Orpheus and Euridice, by Christian Gottlieb Kratzenstein.
Orpheus and Euridice, by Christian Gottlieb Kratzenstein.

1878  –  Asteroid 190 Ismene, a member of the Hildian family, discovered by C H F Peters. The family are named after asteroid 153 Hilda.


1884  –  Asteroid 242 Kriemhild discovered.


2004  –  Planetoid 120347 Salacia discovered.  Salacia has an incredibly high number, but is significant because, as you will have noticed, I used the word “planetoid”, indicating it isn’t one of my normal day-to-day asteroids.  This particular Kuiper belt object is estimated to be 850 km (530 miles) in diameter.


March 31 – 40 Harmonia

Main-belt asteroid 40 Harmonia was discovered by Hermann Goldschmidt on March 31st, 1856.  It is an S-type main belt asteroid, about 107 km in diameter.  One of 14 asteroids discovered by Goldschmidt, Harmonia is named after the Greek goddess of (obviously) harmony.  Her Roman counterpart was Concordia (who also has an asteroid named after her, discovered in 1860).  The name was chosen to mark the end of the Crimean War, which officially came to an end, with the signing of the Treaty of Paris, on the day before Harmonia was discovered.

Despite her harmonious attributes, the most popular stories surrounding this goddess involve a necklace she received on her wedding day, possibly from Hephaestus (different sources give various donors).  This necklace, while it apears to have had no adverse impact on Harmonia herself, had a long life bringing misery and death to all who owned it after her.

Polynices giving Eriphyle the necklace of Harmonia.
Polynices giving Eriphyle the necklace of Harmonia.

The photograph shows a red figure oinochoe (wine jug) by the Mannheim painter.   Eriphyle is being bribed by Polynices to get her husband Amphiaraüs to become embroiled in the battle of the “Seven Against Thebes”.  She was later to do the same to her son, Alcmaeon.  When he found out what she’d been up to, he killed her.


1886  –  Asteroid 254 Augusta was discovered by Austrian astronomer Johann Palisa on March 31st 1886.  It is a small main belt asteroid of about 12km diameter, and is of spectral type “S”.  It was named after Auguste von Littrow,  the widow of astronomer Carl Ludwig von Littrow.


1886  –  Asteroid 255 Oppavia is another main belt asteroid, and was also discovered on March 31st 1886 by Johann Palisa.  It’s rather larger than Augusta, at 57 km wide, and is a P-type.

The Arms of Opava
The Arms of Opava

Opava is the name of the town where Palisa was born.  It is currently in the Czech Republic, but at the time of Palisa’s birth it was part of the territory known as Austrian Silesia (following the War of Austrian Succession) which is why he is an Austrian astronomer.  Opava’s most famous daughter is Joy Adamson, author of “Born Free”.


2005  –  The large trans-Neptunian object (TNO) and Kuiper Belt object (KBO) Makemake was discovered nine years ago today.  As well as being as TNO, Makemake’s size allows it to bask in the title “dwarf planet”, and while various studies give varying opinions regarding the precise extent of that size, the prevailing view seems to be that it’s around 1,400 to 1500 km in diameter.  Unfortunately for early planet hunters, though, it’s also a very long way away,  (magnitude 16.7 at opposition) and has an unusually high orbital inclination, which is why it was only discovered so recently.

Spectral analysis of the surface suggest that up to 90% is covered in ices of methane and Nitrogen, with “tholins” also present, giving Makemake a reddish appearance visually.  It has almost no atmosphere, and (unusually for such a large TNO) no satellites.


1891  –  Discovery of asteroid 308 Polyxo by Alphonse Borrelly. Measuring 130 km across, Polyxo is one of the rare, mysterious T-type asteroids. There are multiple Polyxo’s in Greek mythology, but I believe this particular asteroid was named after one of the Hyades.


1997  –  Death of Lyman Strong Spitzer Jr.