Sunday, February 11, 2018

Fasten your Kuiper belt, it's going to be a bumpy night

...may not be exactly what Bette Davis said in her role as Margo Channing in All About Eve back in 1950, but it's probably what she meant.

For those of you who never click on links, here are the first three paragraphs from Wikipedia's article about the Kuiper belt:

"The Kuiper belt (/ˈkaɪpər/ or Dutch pronunciation: ['kœy̯pǝr]), occasionally called the Edgeworth–Kuiper belt, is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune (at 30 AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times as wide and 20 to 200 times as massive. Like the asteroid belt, it consists mainly of small bodies or remnants from when the Solar System formed. While many asteroids are composed primarily of rock and metal, most Kuiper belt objects are composed largely of frozen volatiles (termed "ices"), such as methane, ammonia and water. The Kuiper belt is home to three officially recognized dwarf planets: Pluto, Haumea and Makemake. Some of the Solar System's moons, such as Neptune's Triton and Saturn's Phoebe, may have originated in the region.

"The Kuiper belt was named after Dutch-American astronomer Gerard Kuiper, though he did not predict its existence. In 1992, Albion was discovered, the first Kuiper belt object (KBO) since Pluto and Charon. Since its discovery, the number of known KBOs has increased to over a thousand, and more than 100,000 KBOs over 100 km (62 mi) in diameter are thought to exist. The Kuiper belt was initially thought to be the main repository for periodic comets, those with orbits lasting less than 200 years. Studies since the mid-1990s have shown that the belt is dynamically stable and that comets' true place of origin is the scattered disc, a dynamically active zone created by the outward motion of Neptune 4.5 billion years ago; scattered disc objects such as Eris have extremely eccentric orbits that take them as far as 100 AU from the Sun.

"The Kuiper belt is distinct from the theoretical Oort cloud, which is a thousand times more distant and is mostly spherical. The objects within the Kuiper belt, together with the members of the scattered disc and any potential Hills cloud or Oort cloud objects, are collectively referred to as trans-Neptunian objects (TNOs). Pluto is the largest and most massive member of the Kuiper belt, and the largest and the second-most-massive known TNO, surpassed only by Eris in the scattered disc. Originally considered a planet, Pluto's status as part of the Kuiper belt caused it to be reclassified as a dwarf planet in 2006. It is compositionally similar to many other objects of the Kuiper belt and its orbital period is characteristic of a class of KBOs, known as "plutinos", that share the same 2:3 resonance with Neptune."

(end of excerpt from Wikipedia)

I bet your little heads are spinning faster than Pluto, Haumea, and Makemake, which (as we all know and should not be fooled by articles in Wikipedia) are a part of the Bismarck Archipelago, a group of islands off the northeastern coast of New Guinea in the western Pacific.

I'm joking.

An interesting aside, Makemake (also written as Make-make or MakeMake; pronounced [ˈmakeˈmake] -- which I, rhymeswithplague, am pretty sure has four syllables, not two -- in Rapa Nui) in the Rapa Nui mythology of Easter Island, is the creator of humanity, the god of fertility and the chief god of the "Tangata manu" or bird-man cult (this cult succeeded the island's more famous Moai era). He is a frequent subject of the Rapa Nui petroglyphs. In astronomy, the trans-Neptunian dwarf planet Makemake was so named because both the planet and the island are connected to Easter; the planet was discovered shortly after Easter 2005, and the first European contact with Easter Island was on Easter Sunday 1722. The dwarf planet's code name was "Easterbunny".

Interesting asides aside, and I'm sure Yorkshire Pudding will say that everybody knows that Makemake is both a trans-Neptunian object in the Kuiper belt and the god of fertility on Easter Island just as everybody knows that the capital of Burkina Faso is Ouagadougou, the real question before us is this:

What in the name of all that's holy is an AU?

People here in Georgia would say with confidence that AU is Auburn University over in Alabamistan, but they would be wrong. An AU is an Astronomical Unit.

Ever inquisitive, you are probably now saying, "Okay, but what is an Astronomical Unit?"

I'm glad you asked.

An Astronomical Unit is the mean distance between the Earth and the Sun, or approximately 93,000,000 miles (150,000,000 km). I say "mean distance" because -- as you all know -- the Earth's orbit around the Sun is elliptical in the same way that the moon's orbit around the Earth is elliptical. Sometimes we are closer to the sun, and sometimes we are farther away, but the mean distance is -- all together, class -- 93,000,000 miles (150,000,000 km).

Here's another aside. Just as the moon's closest approach to earth is called its perigee and its farthest distance from Earth is called its apogee, the Earth's nearest and farthest distances from the Sun are called its perihelion and apohelion, respectively.

I think that's quite enough new material for one post.

I hope you have been taking notes, because there may be testing later. Any pop quizzes will also include questions about the theoretical Oort cloud and Saturn's Phoebe, which you are expected to learn about in your outside reading.

I told you it was going to be a bumpy ride.

This has been the Rhymeswithplague Occasional Foray Into Science (ROFIS), because a lot of what we thought we knew about the Solar System has changed since most of us were in school.

(Based on the public domain Nasa images)

To help you grasp the size of the trans-Neptunian objects above, Earth is shown at the bottom center of the composite photograph, and in the lower lefthand corner is Earth’s moon.


  1. I used to enjoy all this stuff and I still find it interesting. We were taught a bit of it when taught to navigate.

  2. I vaguely remember learning a little about the Kuiper Belt in school many years ago. This was extremely interesting. But I thought AU was the atomic symbol for gold.

    1. Emma, I don’t remember one stinkin’ word about the Kuiper belt, the scattered disc, or the theoretical Oort Cloud, but (a) I went to school long before you did and (b) our school didn’t have a course in astronomy, just a chapter in general science. You are right, AU is gold (aurum in Latin). And silver is AG (argentum in Latin — AR had already been used for argon), and lead is PB plumbum in Latin).

  3. Adrian, I got most of my navigation training from Peter Pan, who said, “Second star to the right, then straight on ‘til morning” and maybe a little from the Boy Scouts. Oh, and my showed me Orion’s belt too, but it never got me anywhere.

  4. AAAARRGGH! My brain hurts after reading this post. Information overload! Brain explosion imminent! By the way - what is "Earh" in the final paragraph? Perhaps it is simply an uncharacteristic "typo" for which I am happy to forgive the author of "Rhymes With Plague" with all my heart. None of us are perfect.

    1. Y. Pudding, thank you! It was an uncharacteristic typo, as you put it, and I am grateful to you for spotting it. I spotted another one just before I published the post; I had left the ‘c’ out of ‘theoretical ‘. Your brain really would explode if you saw all the information I could have included in this post but decided to omit! I am a merciful blogger, always thinking of my readers.

  5. If I said that I read that rather more speedily that I might have done if I had the slightest interest in the subject I hope that you will forgive me. My next post might well be on the Roman Law doctrines of jus publicum and jus privatum.

  6. Graham, My middle name is Boring. Actually, my middle name is Henry, but you get what I’m saying. I am sorry to have missed the mark. Oh, well, you (that is, I) can’t win ‘em all. There’s nothing to forgive but you can consider yourself forgiven anyway.

  7. I think that I should apologise for my last comment. I think there could have been a more polite way of getting my point across. Indeed, I would probably have been better leaving no comment at all.

  8. Graham, no apology necessary, absolutely no reason for one. Never hesitate to say what you think where this blog is concerned. I know I am not everybody’s cup of tea (it’s rather obvious from the numbers I get). I do enjoy having dialogue with the few readers who hang in there. I have a thick skin and you can speak freely here (except that blue language will not be published — I’m rather old-fashioned in that regard).

  9. Actually we all have things we consider interesting or not interesting but the latter doesn't mean that it's necessarily boring just that it's not of interest. I'm ashamed to say that astrophysics is not really my subject although I have a dear friend in New Zealand who used to come down to The Cottage and chat about the subject into the wee small hours. Despite the fact that she was a lawyer if I'd started on Roman Law (which I enjoyed) she would have quickly said 'goodnight'.