From the USM Southworth Planetarium
“Even the lows are wonderful”
THE DAILY ASTRONOMER
November 9, 2009
Planet Hopping
So, when we guide unsuspecting audiences through the solar system, our path is linear and consistent:, We begin each planetary perambulation with a stop at the ultimate non-planet: Sol, otherwise known as the Sun. We often call it an average star and it is fortunate that the Sun never addresses this actionable slur. To us, it is hardly average: an unfathomably large, furiously hot sphere of fusion fire enclosed in roiling layers of ceaseless convection. It is the solar system centerpiece bestowing copious heat and light upon the mote-like worlds that it has trapped in orbit around it. The Sun would prove lethal if we strayed either too close or too far away from it, but sustains us provided we remain within the constraints of a narrow region; i.e., it’s an ideal spouse.
We trip over to Mercury, a fast little critter world with 700 degree days and nights steeped in temperatures below -250 degrees! And, as — Mercury is a slow turner (rotation rate of about 60 days), its frigid night lasts for thirty days! Like Barrow, but without the oil.
Venus is a treat; Once envisioned as a lush, verdant paradise of flora by the overly sentimental 20th century sci-fi writers, Venus is a cloud enshrouded blast furnace. Its surface is 900 degrees pole to pole; for a little flavour, it has sulfuric acid rains, exploding volcanoes, and a surface pressure ninety times greater than sea level on Earth. Like the Old Port before the recent renaissance.
Earth. Lots of life, activity, poetry, passion, tectonic activity and sporting events. Humans share the sphere with an assortment of exotic creatures, most of which have the misfortune of tasting good on toast. Our choice planet if only for the oxygen and many ironies.
Moon. Yes, we know that the Moon is not a planet, but as it is one of the night sky’s most captivating objects, our one natural satellite commands its own segment in most solar system shows. Apart from being held liable for werewolf transformations and psychosis induction, the Moon has been revered by generations of aging Earthlings who find the concept of a gravitational body pulling upwards to be quite appealing.
Mars. Red World. Ominous world. Seething, desolate world. World of fictional aliens and desiccated lake beds. Humanity’s destiny and greatest challenge. Eye of the devil. God of War. Palace of scantily-clad princesses upon the backs of mammoth lions. The desert sphere inspiring generations of writers. All those striving to describe Mars are united by one common trait: a curious inability to write in complete sentences.
Asteroid Belt. Not much to see here. Astronomers have currently catalogued thousands of this errant space mountains lurking in the dark beyond the realm of the inner planet. However, arcade games and Star Wars movies apart, asteroid belts are not billiard ball galleries teeming with swarms of colliding asteroids. One would be hard pressed to even encounter an asteroid if one flew through the asteroid belt. If you did, it wouldn’t be well illuminated, either. It would emerge ghost-like from the dark, like that pyramid in the 8 ball prophecy toy that we all secretly still keep in our bedrooms. (well, not us.)
Jupiter. Now, we’re out in the wilds. This is a world of a different sort. Unlike the four other planets already seen, Jupiter is a bloated gas giant. Well, so is the Sun, but Jupiter is far less massive than Sol, though it is more massive than all the other planets put together!
Being so massive, Jupiter has the lion’s share of “moons.” The current count is 63, including the four Galilean Moons, the first “moons” beyond our Moon to be discovered. Visible in the telescope as dots on either side of Jupiter, these moons were discovered by Galileo in 1610 and also often get their moment in the spotlight.
Ganymede: largest moon in the solar system, including our moon. Bigger than Mercury and therefore demands, but is denied, higher billing
Io: the most volcanically active body in the solar system, including Venus and the Packer’s offensive line. We tell children it looks like a pizza. (pause for laugh)
Callisto: beaten. and bruised. Callisto has the dubious distinction of being the most heavily cratered body in the solar system. More than 95% of its surface is pockmarked by craters, cliffs and chasms. Spends its life in a desperate daze induced by a long history of batterings. It’s the Cubs fan of the solar system.
Europa: the world of thick surface ices upon which one sees sinuous tracks of dark, -perhaps organic-material. As it might contain a warm, subterranean ocean, Europa is the last possible location of extra terrestrial life in the solar system. Seeking out any “life forms,” on Europa is one of our principal aims, especially if they taste good.
Saturn: every adjective that is remotely synonymous with “magnificent” has been employed and over employed when speaking of Saturn. It is truly the most recognizable planet in the solar system, including Earth. (It is said that 23% of middle school students can’t point out Earth on a globe.) Saturn has that complex ring system that makes it appear brighter in our sky than it otherwise would. Though they appear solid, these rings are tiny particles of ice, rock and dust. Saturn defined the outer bound of the known solar system until the 18th century.
Uranus: everybody who teaches astronomy in public hates the name of this world for obvious reasons. We astronomy types prefer to be laughed at for our lack of social graces and unorthodox fashion sense instead of for the words we say. This planet was discovered by William Herschel, an example of nature’s most artful fusion in the history of under-employment: the astronomer-musician. Like Saturn and Jupiter, Uranus has a ring system, but unlike the other planets it rotates on its side, making it appear as a blue bull’s eye. Please don’t draw any inferences from our abundance of pub-inspired analogies.
Neptune: Much better name! Discovered after astronomers noticed that something was sometimes pushing and pulling Uranus. (We’re grateful that we don’t have to say that in public.) Neptune was eventually discovered, but by two mathematicians, one in France the other in Britain. Astronomers haven’t totally recovered from the ignominy of being trumped by the math guys. Both France and Britain claimed Neptune as their own, but eventually they shared it. To their credit, both nations promised limited autonomy to Neptune’s indigenous populations.
Pluto: Was a planet since its discovery by American Clyde Tombaugh in 1930. Stopped being a planet in August 2006, when the International Astronomical Union realized that if Pluto got to be a planet, then all comparably sized objects (the Galilean Moons, most large asteroids, and Mongolia) would also demand planet status. After its demotion, Pluto was called a “trans-Neptunian object,” defined as a sizable body beyond Neptune’s orbit. In June 2008, the International Astronomical Union called Pluto a “Plutoid,” defined as a trans Neptunian object which, like Pluto, is made principally of ice. Pluto, being made of ice and not gas, serves as the quintessential “plutoid,” and by this definition, the IAU has established that Pluto is quite a bit similar to itself.
We would then proceed to the various regions beyond Pluto:
to the smaller Quaoar, named after the Inuit goddess of the sea. This name is sensible because, like the water bodies frequented by the Inuit people, Quaoar has been a solid for about four billion years.
Eris follows. Named for the goddess of discord (not too redundant), Eris is larger than Pluto. Its discovery was a decisive factor which compelled the IAU to demote Pluto, thereby perpetuating a ceaseless discord in the usually sedate astronomical community.
Here we come to the edge of the Kuiper Belt: a disc containing the nuclei of short-period comets, defined as those having orbital periods of or less than 150 Earth years. That a span of time which is longer than the human life-span should be considered by astronomers as “short period” helps explain why humanity’s happiest people remain woefully ignorant of astronomy.
Well beyond the Kuiper Belt is the Oort Cloud: a sphere of cometary nuclei from which originate the long period comets, those with orbital periods measuring in the centuries or millennia. Many years ago, some researchers theorized that the Sun has a binary companion with an mean distance of a light year or more. According to this theory, when this star, named “Nemesis,” passed through periastron (the closest point between the components of a binary system) the resultant gravitational influence caused an armada of these objects to descend upon the inner solar system. That no visible evidence of Nemesis has yet been collected is regarded by some as irrefutable proof of its existence (Re: quarks, gnomes and dragons.)
