About Planets

There are some things you really should know about planets.

Actual conversation overheard while shopping at a local dollar store last Christmas season:

Young Woman 1: Who’s that for? (Pointing at a glossy sheet held by her companion, with several planets and moons on it)

Young Woman 2: Oh, Jeff. (I’m pretty sure that’s how she spelled it mentally – she didn’t seem capable of spelling it ‘Geoff’ – and this is not intended to disparage anyone whose parents chose to spell their name the former way; I’m sure they were perfectly capable of either spelling, and merely chose “Jeff” to show their affinity for Standard American English, so that you wouldn’t feel out of place should you one day have a high-paying job on Wall Street)

Young Woman 1: What is it? (She was pointing at a large glossy print of Earth as she asked this)

Young Woman 2: Oh, I think it’s the six planets or something. Jeff’ll love it. He loves planets. (This, in reference to a sheet that held no fewer than twelve objects, all of which were pretty straightforward – objects such as our moon, which is visible on many nights from right here on Earth, should one care to look up)

Young Woman 1: I thought there were seven? (I could only see the back of her head, but she tilted it at an awkward angle indicating, I think, confusion. This confusion was not, however, endearing in the way that a small dog cocking its head to one side can be endearing)

Young Woman 2: Well, there’s Mars and Jupiter and Saturn... (She paused here, apparently running out of easy-to-name planets)

Young Woman 1: Venus? (Her head continued at its awkward angle)

Young Woman 2: Yeah.

At this point, I was thankfully distracted from their conversation, but it got me thinking – how much do people really know about their own local cosmic neighbourhood? I mean, isn’t this something pretty damn basic? Something you really should know?

A few quick facts:

- Our solar system has eight planets. If you think it is or should be nine, it’s likely because you are thinking about:

- Pluto, which is no longer considered a planet. It’s technical designation is a dwarf planet, and interestingly,

- It isn’t even the largest one – that would be Eris.

- Astronomers now believe there may be hundreds, or even thousands, of similar Kuiper Belt objects (such as Sedna, Haumea, and others being discovered all the time)

- Pluto is still special – it is also a Trans-Neptunian Body (which means it crosses Neptune’s orbit), and it may be the first of a new designation – binary dwarf planet – due to its relatively large moon, Charon

- A NASA probe has just entered into orbit around an asteroid named Vesta, and next year will enter orbit around Ceres, the nearest dwarf planet to Earth (it's located between Mars and Jupiter)

In English, the planets are named after Roman gods – except for Earth. It’s named after dirt. Really. And did you know that astronomers have discovered over 500 exo-planets since 1995? These are planets orbiting around other stars, and the ones they’re finding keep getting smaller as their instruments keep getting more sensitive. They’ve already announced one Earth-like planet (similar mass to Earth, possibility of liquid water based on its orbit) found this year, and we should be hearing about plenty more soon. Exciting times, and this is something people really should know about.

Of course, it brings to mind one of Jay Leno’s “Man on the street” interviews I saw a few years back. He asked a young woman how many planets there were. She answered, “Seven? Maybe eight?” He smiled, corrected her (Pluto was still considered a planet then, so the answer was nine), and asked her what she did for a living: she was an assistant manager at a Planetarium. Maybe I’m asking for too much?