Tuesday, December 16, 2008


On a couple of our many trips to Las Vegas, we took overnight trips to Flagstaff, Arizona, which is the home of Lowell Observatory. I'm always amazed at how clear the sky appears at night at the 8,000 foot altitude. One can see the Milky Way without a telescope--you can't see that in Chicago. This is a public observatory, and for a small admission price, they'll let you look through the telescope. We had the good fortune to be there to observe when Mars made a close pass a couple of years ago. It was an awesome sight.

Lowell Observatory is famous because the former planet Pluto (or was it the planet formerly known as Pluto?) was discovered there in 1930 by Clyde W. Tombaugh. Pluto, of course, hasn't gone away but instead, in 2006, in a controversial decision, was re-classified as a dwarf planet.

This was distressing to Mrs. Venetia Phair, who was the first to suggest the name "Pluto" to the discoverer Mr. Tombaugh. Mrs. Phair, an Englishwoman, who is now 89 years old, was 11 at the time. She came from a family of prominent scholars. Her father, Rev. Charles Fox Burney was a professor of theology at Oxford. Her grandfather, Falconer Madan was Librarian of the Bodleian Library at the University of Oxford. His brother, Venetia's granduncle, Henry Madan had suggested the names Phobos and Deimos for the moons of Mars. Her family carried some serious clout in the astronomical community.

As the story goes, on March 14, 1930, Falconer Madan read young Venetia The Times story about the discovery of the new planet. She suggested the name Pluto, the Roman God of the Underworld who was able to make himself invisible. Madan was so excited for his granddaughter that he forwarded that idea to astronomer Herbert Hall Turner who in turn thought enough of it to cable his American colleagues at Lowell Observatory. Tombaugh liked the name because it started with the initials of Percival Lowell who had founded the Observatory and who had years earlier predicted the existence of the new planet. A month later, the girl's suggestion was formally adopted for the planet. Inverviewed recently, Mrs. Phair declared, "At my age, I've been largely indifferent to [the debate], though I suppose I would prefer it to remain a planet."

Clyde W. Tombaugh was an interesting guy himself. Of course, his major claim to fame is the discovery of Pluto, but he also discovered 14 asteroids and called for serious scientific research of UFO's which he claimed to observe on several occasions. Tombaugh hailed from Streator, Illinois, a small village surrounded by cornfields, about 100 miles southwest of Chicago. He built a 9 inch telescope in his garage which he used to make detailed drawings of Jupiter and Mars. He sent his pictures to the Lowell Observatory, and by return mail he was offered a job as an astronomical photographer. The year was 1929, and he was 22 years old.

His job was to perform a systematic search for a new "Planet X" to confirm Percival Lowell's prediction. Lowell actually would have discovered the planet years earlier, but he had a defective photographic plate--the defect was where the new planet would have appeared.

In any event, Tombaugh took photographs of the same section of sky several nights apart. He used a device called a blink comparator to compare the different images. When one shifts between the two images, back and forth, a moving object, such as a planet, would appear to jump from one position to another. The more distant stars would remain stationary. Tombaugh did this each night for weeks at a time and developed a trained eye, which noted the moving object, Pluto. To the casual observer, the photos with millions of stars look exactly alike.

The reason astronomers predicted a "Planet X" was because irregularities in the orbit of Neptune indicated that another large planet further out was causing them. After astronomers studied Pluto, they determined that Pluto was too small to cause those irregularities. There must be another planet out there.

In 1978, astronomer James Christy discovered a slight bulge that appeared periodically on highly magnified images of Pluto. It turned out that Pluto had a moon, named Charon which is about half the size of Pluto. It is so large compared to the planet that it is not really a "moon" in its conventional sense, but rather Pluto and Charon could be considered a dwarf planet system. This was confirmed when in the late 1980's Christy observed a series of mutual eclipses which occur only twice during Pluto's 248 year orbital period when their orbital plane is edge-on as seen from Earth. His timing was very fortunate.

Christy was apparently watching too much TV because he wanted to name a star after his wife. He suggested the name Charon because his wife's name was Charlene, or "Char". That's not a name connected with mythology, but Christy learned, coincidentally, that Charon, in Greek mythology, was the ferryman of the dead, with close ties to the god Hades whom the Romans called Pluto. So there was a serendipitous ending to this story. Christy paraphrased the forgettable song by Paul Revere & the Raiders called, I Ain't Sharin' Charon.

But there were many more large objects out there waiting to be discovered. Using the Hubble telescope and other giant telescopes, we learned about Trans-Neptunian Objects (TNO's) like Quorar, Sedna, Makemake, Haumea, and now Eris, which is significantly larger than Pluto. Eris was discovered by astronomer Mike Brown in 2003. To go along with the Pluto theme, some wags have suggested that these TNO's be given names like Mickey and Goofy. Eris, which was at first unofficially called Xena , even has a moon, Dysnomia (which in English means "lawlessness" in honor of actress Lucy Lawless who portrayed Xena on the popular TV show). I'm not making this up! To date 1075 TNO's have been discovered though only 142 of them have their orbits determined so that they have been given names or number designations.

Because of the relatively small size of these objects compared to the other planets, and the prospect of discovering other similarly sized objects, the International Astronomical Union (IAU) was forced to define the term "planet" for the first time.

Incidentally, the names of astronomical objects are determined by the IAU. All the planets, asteroids, etc. have Classical names from Greek and Roman (and even Norse) mythology except for the third planet. That one was named after the legendary Johnny Earth from the South Side of Chicago, a classmate and acquaintance of mine who was known for using his head. Mr. Earth reportedly discovered the planet when he woke up seeing stars after using his head to shatter a nearby windshield with the help of a guy named Ed, during a brawl on 79th Street. Mr. Earth, informally known as the Mayor of 79th Street, departed this world (Earth) with these words of wisdom, "Always steal a Cadillac or a Lincoln, if you can't outrun 'em, you can run 'em over." Actually I am making that up, but only the part about the planet being named after Mr. Earth.

Seriously though, now that the IAU has designated dwarf planets, it assigns numbers to them in their approximate order of discovery, coupled with a name assigned by the discoverer or the provisional designation. For example, we have 90377 Sedna, or 2002 TX 300 (a provisional designation). Essentially, if you want to name a minor planet, you have to discover it. But the discoverer must write a report to the IAU explaining the reasons for assigning the name according to IAU guidelines and get the approval of a 15 person committee of professional astronomers from around the world. Some guidelines are: it must be pronounceable (in some language), it must be non-offensive, non-commercial (Exxon is out) and one word, 16 letters or less. Political or military figures must be dead for 100 years.

So-o-o, you can pay $40 or so to have a star named after you, but it is unlikely the IAU will put your name on the official star maps. So save your money! Its easier to get your name on a minor planet if you're friends with the discoverer. Even Donald Trump isn't on the astronomical map--yet.




Blogger Laurel Kornfeld said...

Pluto IS a planet because unlike most objects in the Kuiper Belt, it has attained hydrostatic equilibrium, meaning it has enough self-gravity to have pulled itself into a round shape. When an object is large enough for this to happen, it becomes differentiated with core, mantle, and crust, just like Earth and the larger planets, and develops the same geological processes as the larger planets, processes that inert asteroids and most KBOs do not have.

Not distinguishing between shapeless asteroids and objects whose composition clearly makes them planets is a disservice and is sloppy science.

As of now, there are three other KBOs that meet this criterion and therefore should be classified as planets—Haumea, Makemake, and Eris. Only one KBO has been found to be larger than Pluto, and that is Eris.

The IAU definition makes no linguistic sense, as it states that dwarf planets are not planets at all. That’s like saying a grizzly bear is not a bear. Second, it defines objects solely by where they are while ignoring what they are. If Earth were placed in Pluto’s orbit, by the IAU definition, it would not be a planet. That is because the further away an object is from its parent star, the more difficulty it will have in clearing its orbit.

Significantly, this definition was adopted by only four percent of the IAU, most of whom are not planetary scientists. No absentee voting was allowed. It was done so in a highly controversial process that violated the IAU’s own bylaws, and it was immediately opposed by a petition of 300 professional astronomers saying they will not use the new definition, which they described accurately as “sloppy.” Also significant is the fact that many planetary scientists are not IAU members and therefore had no say in this matter at all.

Many believe we should keep the term planet broad to encompass any non-self-luminous spheroidal object orbiting a star.

We can distinguish different types of planets with subcategories such as terrestrial planets, gas giants, ice giants, dwarf planets, super Earths, hot Jupiters, etc.
We should be broadening, not narrowing our concept of planet as more objects are being discovered in this and other solar systems.
In a 2000 paper, Dr. Alan Stern and Dr. Hal Levison distinguish two types of planets—the gravitationally dominant ones and the smaller ones that are not gravitationally dominant. However, they never say that objects in the latter category are not planets.

I attended the Great Planet Debate, which actually took place in August 2008, and there was a strong consensus there that a broader, more encompassing planet definition is needed. I encourage anyone interested to listen to and view the conference proceedings at http://gpd.jhuapl.edu/ You can also read more about this issue on my blog at http://laurele.livejournal.com

You can find the petition of astronomers who rejected the demotion of Pluto here: http://www.ipetitions.com/petition/planetprotest/

December 17, 2008 at 11:26 AM  
Anonymous sphinx711 said...

Thank you, Laurel. That was very informative. The dispute is a matter of form over substance. The objects out in space are there forever, and are not going to change, no matter what we call them. Astronomers are discovering new planets and objects on a regular basis and maybe we need a new classification system that people can understand.


December 18, 2008 at 9:29 PM  

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