The meaning of "fetid"; Albireo; and musings on variations in sensory perception (Shallow Thoughts)

The meaning of "fetid"; Albireo; and musings on variations in sensory perception

The street for a substantial radius around my mailbox has a wonderful, strong minty smell. The smell is coming from a clump of modest little yellow flowers.

They're apparently Dyssodia papposa, whose common name is "fetid marigold". It's in the sunflower family, Asteraceae, not related to Lamiaceae, the mints.

"Fetid", of course, means "Having an offensive smell; stinking". When I google for fetid marigold, I find quotes like "This plant is so abundant, and exhales an odor so unpleasant as to sicken the traveler over the western prairies of Illinois, in autumn." And nobody says it smells like mint -- at least, googling for the plant and "mint" or "minty" gets nothing.

But Dave and I both find the smell very minty and pleasant, and so do most of the other local people I queried. What's going on?

Another local plant which turns strikingly red in autumn has an even worse name: fetid goosefoot. On a recent hike, several of us made a point of smelling it. Sure enough: everybody except one found it minty and pleasant. But one person on the hike said "Eeeeew!"

It's amazing how people's sensory perception can vary. Everybody knows how people's taste varies: some people perceive broccoli and cabbage as bitter while others love the taste. Some people can't taste lobster and crab at all and find Parmesan cheese unpleasant.

And then there's color vision. Every amateur astronomer who's worked public star parties knows about Albireo. Also known as beta Cygni, Albireo is a double star, the head of the constellation of the swan or the foot of the Northern Cross. In a telescope, it's a double star, and a special type of double: what's known as a "color double", two stars which are very different colors from each other.

Most non-astronomers probably don't think of stars having colors. Mostly, color isn't obvious when you're looking at things at night: you're using your rods, the cells in your retina that are sensitive to dim light, not your cones, which provide color vision but need a fair amount of light to work right.

But when you have two things right next to each other that are different colors, the contrast becomes more obvious. Sort of.

Point a telescope at Albireo at a public star party and ask the next ten people what two colors they see. You'll get at least six, more likely eight, different answers. I've heard blue and red, blue and gold, red and gold, red and white, pink and blue ... and white and white (some people can't see the colors at all).

Officially, the bright component is actually a close binary, too close to resolve as separate stars. The components are Aa (magnitude 3.18, spectral type K2II) and Ac (magnitude 5.82, spectral type B8). (There doesn't seem to be an Albireo Ab.) Officially that makes Albireo A's combined color yellow or amber. The dimmer component, Albireo B, is magnitude 5.09 and spectral type B8Ve: officially it's blue.

But that doesn't make the rest of the observers wrong. Color vision is a funny thing, and it's a lot more individual than most people think. Especially in dim light, at the limits of perception. I'm sure I'll continue to ask that question when I show Albireo in my telescope, fascinated with the range of answers.

In case you're wondering, I see Albireo's components as salmon-pink and pale blue. I enjoy broccoli and lobster but find bell peppers bitter. And I love the minty smell of plants that a few people, apparently, find "fetid".