Science | Skywatch with Bill Irwin

By Bill Irwin –

This article covers June, July, and August. It’s about time, astronomy is totally married to it, the positions and motions of the heavenly bodies are the hands of a great cosmic clock. Hence the great seasonal variations. You get a sense of it being out under the stars.

The dark times shrivel up around June solstice. At our latitude, 52 degrees north, it doesn’t get completely dark. One a.m. is the darkest time on daylight saving time and the north horizon looks like dawn. South, you lose a magnitude, so the number of visible stars is nearly half what it would be if the sun were 18 degrees or more below the horizon, for a true astronomical dark.

If you were up that late and the moon was not interfering, you could still see the hazy outline of the Milky Way overhead. The planets, being bright, are not affected by the lack of dark.

Venus is the big show in the west after sunset. It is the brightest natural object after the sun and moon, with the exception of an occasional bright meteor. Since its orbit is inside the Earth’s, it moves faster around the sun and is catching up to us as it swings toward inferior conjunction between us and the sun. Since it is coming close, its size will grow, but as it gets closer to being directly in line with us and the sun, we will be increasingly looking at its dark backside and the lit portion becomes a slender crescent. This is one of the great evidences that the Earth is not in the centre of the solar system.

Meanwhile, Jupiter dominates the southeastern sky having passed being opposite the sun in the sky. If you have good binoculars or a spotting scope, you could make out the moons and see that their positions change nightly. Another of the great evidences that things go around things out there.

Saturn passes opposition mid-June and comes after Jupiter, low down in the southeast sky in the constellation Sagittarius with its prominent “teapot” asterism. You can even see the steam coming out of it, one of the great star clouds in the direction of the Milky Way’s centre. Even though it’s low and our murky atmosphere obscures the details, seeing the rings is one of the great thrills of visual astronomy. You’ve seen it on TV or in a magazine, but you didn’t fully realize it actually had rings until you really see it for the first time. There you are, standing on the ground, on a planet that is rotating and revolving around the sun and watching other planets catching up and at once you know where things are.

I’m getting excited just writing about it, because to top it off, Mars reaches opposition in mid-July. We talked about that in the last Skywatch.

So, despite the bright nights, this is a banner summer for planets.

By the time late July rolls around and then into August, we enter prime time for most casual skygazers. Nights are still warm and the perseid meteor shower peaks around August 11.

The Mt Kobau star party is from August 4–12 this year. If we escape a disastrous fire season this year, it would be the premier event for anybody interested. Up at 6,000 ft on spectacular Kobau Mountain near Osoyoos, a whole week of around 50 astronomers with all different kinds of telescopes, lectures, talks, and door prizes. No line-ups or charges to see things. Take the plunge, leave Skywatch in the past, find the inner astronomer, get eaten by different bugs!

If there is enough interest, we can do something here in the Cariboo as well, in early September, when the moon isn’t watching. We have sufficient space here at Bells Lake. The observatory location is surrounded by a campsite and there are places to park a camper or RV. Give me some feedback and it can happen.

I learned a lot watching the clock in grade school. Okay—class dismissed.

As usual, you can come right down to the arena here at the Bells Lake Observatory. Contact me at (250) 620-0596 or irwin8sound@gmail.com.

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