The title: Start off your winter with the greatest Great Conjunction in nearly 800 years.
You know, I appreciate articles on astronomical events. Let's get more people into astronomy. But don't distort things and please get your facts right.
Oh boy. I thought that headline a little bit sensational so I read the entire article. Some of the content is good but it also contains errors or ambiguous or convoluted explanations. Time for myth-busting. Here we go.
headline hoopla
I've a minor issue with the headline. I think that banner might be over-hyping the event. That said, the 800 year reference is clarified within the article. Still, I think 400 years would be fair. The historical references are important, don't get me wrong. Why not just emphasise the 20 year cycle?
How about a headline: Check out the cool conjunction of Jupiter and Saturn this winter.
quick list issues
Near the top of the article is a "quick list" highlighting interesting events. It's pretty good overall. But the author notes to Jan 24 for the "Alignment of Earth, Sun and Saturn." And then the 29th for Jupiter.
What he does not say is that there are "conjunction" events where Saturn is in conjunction with the Sun and 5 days later Jupiter is in conjunction with the Sun. Personally, I consider solar conjunctions as non-events. A thrust of this article is stuff you can see and enjoy. Solar conjunctions? There's nothing to see.
The planet is question is behind or beyond the Sun. In some cases, truly behind it, directly, such that you couldn't possibly see it. If the planet is inclined above or below the Sun, theortically it could be viewed, as nothing is blocking it. But the problem is that the Sun is right beside the planet and viewing the planet would be extremely difficult in a brilliant sky. More importantly, it is extremely dangerous.
My point is, Jan 24 and Jan 29 are moments when you know you cannot see Saturn or Jupiter. If somebody said to me, "Can we view Saturn in your telescope?" I'd say, "No, unfortunately, it's behind the Sun or very close to the Sun. It's the wrong time to look at this planet."
It is significant astronomically in another way: it tells us that the planet is transitioning from the evening to the morning sky. Astronomers know they cannot view it but they also know where to start looking for it in a few weeks or months...
So, while there's a big section on conjunctions and alignments in this article, none of this is clearly explained, sadly.
winter air
OK. I might be on thin ice on this matter...
Sutherland says that "stars, planets and the Moon appear crisper and cleaner" in the winter. Now, this is interesting because we have a weather expert, a professional meteorologist commenting on this but I really do not think this is an entirely fair comparison.
He says the humidity is lower in the winter. Really? I pulled up some historical data for Toronto, Ontario and it seems the average humidity varies between high-70% and high-90% with an overall average of 81%. Most importantly, September was the most humid month whereas May was the least. January and February were below 80 with a sharp drop in March. Curiously, since he's alluding to the official start of winter...
Geography is going to be a big factor, of course, so looking at one city is not appropriate. But I struggle with his remark that the "air overhead tends to be drier." Drier in the winter? Not by much. OK. Let's leave that as arguable or contested.
In the same sentence, he says the air is "more stable." This I really have a problem with. Astronomers, of course, use more complex or distinct measures, notably transparency and "seeing." The seeing or steadiness of the air is important for planetary and double star observing and imaging. And I believe astronomers widely argue that seeing conditions are best in the "shoulder" seasons, spring and autumn. I think the jet-stream is a major factor affecting seeing and of course that is constantly in flux. A weather expert commenting on stability should be very conversant with atmospheric seeing. Ironically, a Canadian meteorologist should be extremely familiar with it as it is a very unique product of Environment Canada.
Back a bit, to a point within that previous paragraph. Given that Canadians live across a broad range of latitudes, one's geographic location becomes a significant factor. The jet-stream effect for your location will drive the seeing conditions. I would hope a meteorologist would be cautious about local weather effects.
I believe our author is caught up in some mythology and has not done proper research. Astronomers would not universally say that the air overhead is better or more stable in the winter. In fact, I suspect many will argue it is worse. This may be anecdotal but a good number of astronomers use and quote Clear Sky Charts which is based on Environment Canada weather data! And many astronomers, pro and amateur, have Sky Quality Meters so actively measure and assess the sky. We're good at it!
I also think the author is caught up in the "stars are brighter in the winter" not considering the Sirius is in fact the number one brightest star in the night sky, a star visible in winter time! It's not a better sky; it's a very bright star. There are lots of bright stars in the winter constellations. That does not equate to better viewing. Personally, I often note significant twinkling or scintillation of stars in the winter. i.e. bad seeing.
In the end, I believe astronomers often say that winter offers poor seeing but good transparency whereas the summer can make for good seeing and less than ideal transparency.
Also, astronomers know or learn that the worst seeing is usually when the transparency is best—right after a cold front has come through. Something a meteorologist would fully appreciate. While there are always exceptions, the coldest, windiest nights usually have bad seeing.
Finally, the "darker" nights I also think could be clarified as it has to do with astronomical twilight. The winter skies may seem darker perhaps because they are longer. There is a longer period of time between astronomical twilight starting after sunset and ending before sunrise. In general, astro-twilight is about one hour from the set-rise time. In south-western Ontario, at the summer solstice, June 20 or 21, total darkness can only be about 3 hours. Travel north, that time reduces. Far enough north, of course, the sky does not get fully dark. So, again, one's observing location is a big factor. I think our author is based in south-western Ontario, at the lowest latitude in Canada.
alignment cycles
The author says:
As Earth, Jupiter, and Saturn orbit the Sun, roughly every 20 years, the timing works out to bring the two bright gas giant planets into alignment in our sky.
This is a mistake, arguably rather significant.
Jupiter orbits every 9 years; Saturn about 29. I'm assuming everyone knows the orbital period for their home planet. Sorry, a bit facetious of me.
Given Jupiter's faster inner track, it "catches" Saturn about every 20 years. That's the resonance of the Jupiter-Saturn crossings. Sutherland does toss out that later elsewhere in the article. Regardless, the wording of the aforementioned paragraph is wrong and hopefully will give any reader pause.
Running simulations in Stellarium, I checked the other numbers (some of which the author did not share) for the Jupiter-Saturn "great conjunctions."
| date | separation between planets |
separation from the Sun |
|---|---|---|
| 4 Mar 1226 | 2' | 49° |
| 16 Jul 1623 | 5' | 12° |
| 21 Dec 2020 | 6' | 30° |
where ' = arc-minutes.
He suggests the 1623 conjunction couldn't been seen. Perhaps. Certainly, they were close to the Sun. But it might have been handy to mention Galilei beginning to use a telescope 'round that time.
opposite?
When Sutherland tries to help people know where to look, he says "Jupiter and Saturn are nearly on the other side of the Sun from Earth on December 21."
No.
I think he's referring to the planets being on the far side of the solar system. And this speaks to the quick list matter with the alignment of Saturn and Jupiter. But it's all poorly worded. One could take the sentence above to reference opposition events. He does talk about opposition events at other times in the piece and does say this happened in the summer. Good. But again, I have a feeling he's referring to the solar conjunction events. But even then, they do not happen on December 21! That's over 1 month later...
For this section, he'd be better off just saying, "Jupiter and Saturn are left of the Sun, about 30 degrees away, on December 21." There. Done. Clear and indicates where to look.
While I'm wired this way, I think explain where bodies are in the solar system is going to be challenging, particularly for audience members who might have some trouble with three dimensional viewpoints for an observing point high above the solar system. It's admirable to try to explain it but one most be spot-on with terms and the visuals should very easy to interpret.
Also, he talks about about having a clear view.
This means a tall building or another high vantage point, or a wide-open field, with nothing obscuring the horizon.
He should say, "This means getting to the top of a tall building..." You do not want a tall building in your way obviously.
That's just a minor grammar issue.
next event
When Sutherland mentions the next occurrence, he says:
It's definitely worth making plans to see this event if you can. We won't see another one like it for another 60 years.
Wrong. Again, these Jupiter-Saturn events happen roughly every 20 years. During the next event, Jupiter and Saturn will be just over 1 degree apart. That will still fit in a low power telescopic view. It will still be awesome to the eye, in photos, and in binoculars. Also the Moon will be attractively close! Mercury will be in the mix too! This will occur in the morning, around 7 AM-ish for Ontario residents, on 2 November 2040. The planets will be 25 degrees from the Sun (to the right).
That's actually gonna be an amazing event (if you're a morning person; if it's clear)!
Now, some appulses will be better than others.
I think he says "like it" meaning so close but if you're trying to genuinely increase knowledge of interesting astronomical phenomena (and not sell website ads), you should list the dates of the next couple, and make reference to the distance from the Sun.
The facts are: super-tight conjunctions are rare, yes. But conjunctions of these two planets do not happen once every 800 years... That's my issue with this whole piece, really.
Sutherland includes an image with a telescopic view but did not reference the orientation or inversion or flipping. Nor is there a specific time indicator. That's a big deal for people trying to identify moons.
At this point the discussion on the "great conjunction" concludes. The article continues delving into other astronomical events... There are more problems.
perihelion
I believe Sutherland's words for the perihelion topic are fair but I was disappointed to not see a stronger stance and more facts.
For example, the furthest distance was not quoted. That would emphasise that the Earth is 1 million km closer to the Sun this time of year. I love sharing that fact with people.
More importantly, I feel this is a key opportunity to do some myth-busting. While we're closer to our star, it's winter in the northern hemisphere. That will strike some people are odd. Then a meteorologist/science writer could explain/remind that seasons are determined by the axial tilt of the planet, not the Earth-Sun distance.
conjunction function
In the CONJUNCTIONS AND ALIGNMENTS section, readers are told that events like the upcoming Jupiter-Saturn clustering "astronomers refer to... as conjunctions."
There's a subtle terminology issue here. Technically, when objects are close together it is an "appulse." Scientists will use appulse for celestial objects being close together in any orientation. You need a specific event or circumstance for a conjunction. The technical term conjunction means that the objects have the same right ascension (RA) value or have the same longitude value along the ecliptic.
As previously mentioned, Sutherland really muddies the waters with conjunctions of the planets themselves and the Sun. They're all conjunctions, generally, but solar conjunctions are a subclass. And he mucked things up with oppositions too. The whole alignment section was an opportunity to clarify the interesting alignments that happen in the solar system.
If he wanted to do this right, some good diagrams would help. He should have top-down diagrams for planetary opposition events, solar conjunctions. He should avoid getting into inferior and superior conjunction events with the inner planets in the interest of brevity.
the faint pyramid
I was heartened to see that Scott Sutherland referred to the RASC and the Observer's Handbook and Roy Bishop's article on zodiacal light. And Sutherland does caution the reader that that light pollution can spoil the view. But I think it is fair to say that extremely dark skies are required, nah, mandatory. He might give city dwellers the impression they can see this. Nope. It is very faint. You're going to have to drive out of town for this one. Or check it while at the cottage.
Also, I don't like the suggestion to "look to the western horizon." It will appear, if at all, in the south-western horizon. Be precise. This might sound like nit-picking but if there's a town due west, observers will mistake that light pollution as zodiacal light.
If I may be so bold, this is a target for an advanced astronomer. Not to sound exclusive. What I mean is: this is a challenge target for an accomplished astronomer. It was years before I saw it (in the country). Good luck but you're gonna have to work at it. Or shoot a long exposure. And don't get tricked by the light dome or a distant town or city.
The most amusing thing here is the photo. Um, that's taken from a mountain top from a remote observatory location!
commentary
I feel strongly (obviously) about this. News writers should do their due diligence and proper research. Writers providing science information are compelled to get their facts right, clarify, and illuminate. And if you don't know, reach out. Get a technical editor.
I filled out the Contact Us form again on the Weather Network website.
When I did this before, they never responded to me, while it is hinted that they will, though they receive a lot of responses.
I doubt I'll hear anything about this article.
I wanted to fact-check and correct and clarify.
No comments:
Post a Comment