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AyJay
08-28-2008, 06:45 PM
I'm looking for help with a detail in my WIP. Part of the storyline involves the Pleiades constellation, and I need to know if it would be possible to see the constellation fairly clearly with the naked eye in late summer in the Canary Islands (pretty specific, huh?). I've done several hours of web research. All I can find is general information about Northern hemisphere vs. southern hemisphere viewing. It appears that wintertime is the best time to see the Pleiades in the northern hemisphere, but the location for my WIP is subtropical, so I'm wondering if it would be different there.

Thanks a million for any help!

Priene
08-28-2008, 07:01 PM
There are two different questions here. How far north, and what time of year? If stars are too near the sun, they won't be visible at all. In the case of the Pleiades (not a constellation, but a cluster in the constellation of Taurus) they disappear from view entirely in Northern Hemisphere late spring / early summer. By late summer they're reappeared before dawn, but won't be visible until well after midnight. The geographical location won't make a difference as the Pleiades are visible way down into the Southern Hemisphere, but your MC will have to be getting up early or staying up late to do it.

Sophia
08-28-2008, 07:13 PM
Hi AyJay,

You might like to download Stellarium (http://www.stellarium.org/), which is a free planetarium program. If I set the location to Las Palmas in the Canary Islands, and keep today's date (as an example of late summer), I see that the Pleiades will rise above the horizon a little after midnight. At magnitude 1.20, they will be visible to the naked eye as long as the sky is dark and the area is rural.

AyJay
08-28-2008, 09:10 PM
Big thanks Pri and Elara. I think I'm on the right track. Elara - the Stellarium program is awesome! I've been fiddling around with it for the last hour.

My MC needs to see the Pleiades cluster very clearly at night (approx. 10pm). The time of year for the story is not too important. I wanted to set it for late August, but it could probably be adjusted. Per Stellarium, it looks like the best time of year to see the cluster at that time (in Las Palmas) would be late September. Does that sound right? Here's another sticking point: my story is set in 9,000 BC. Stellarium only goes back to 4,000-something BC. Would the position of the cluster be dramatically different thousands of years back?

Andy

Priene
08-28-2008, 09:32 PM
Here's another sticking point: my story is set in 9,000 BC. Stellarium only goes back to 4,000-something BC. Would the position of the cluster be dramatically different thousands of years back?

Andy

Whoooooooaaaaaa, hold on. Big, big difference. There's a process called precession (http://en.wikipedia.org/wiki/Precession), which means the Earth does an odd wobble on its axis each 26000 years, which changes both where north is and where the sun is during summer. Taurus is a late Autumn / winter constellation now - the Pleiades look fantastic on a cold November night - but 11000 years ago it would have been a long way around the ecliptic.

A quick calculation (I'm not guaranteeing this, because I'm no expert) makes me think that the sun would have been in Taurus during autumn back then, which means it would have best been seen in spring, when in the tropics it would have appeared overhead, and if you wanted it in the evening, late spring would be good.

The shapes of the constellations would not have looked too different back than. A reasonable amateur astronomer would see notice some changes, but stars take a long, long time to change relative positions.

AyJay
08-29-2008, 07:00 AM
Whoooooooaaaaaa, hold on. Big, big difference. There's a process called precession (http://en.wikipedia.org/wiki/Precession), which means the Earth does an odd wobble on its axis each 26000 years, which changes both where north is and where the sun is during summer. Taurus is a late Autumn / winter constellation now - the Pleiades look fantastic on a cold November night - but 11000 years ago it would have been a long way around the ecliptic.

A quick calculation (I'm not guaranteeing this, because I'm no expert) makes me think that the sun would have been in Taurus during autumn back then, which means it would have best been seen in spring, when in the tropics it would have appeared overhead, and if you wanted it in the evening, late spring would be good.

The shapes of the constellations would not have looked too different back than. A reasonable amateur astronomer would see notice some changes, but stars take a long, long time to change relative positions.

Thanks for the info. Pri. I spent most of the day trying to track down this information. Even the astronomy experts were having trouble giving me an exact answer as their simulation programs don't calculate the position of stars beyond 6,000 years ago. I'm still pressing them for some guidance on estimating the position of the Pleiades cluster during the time period of my novel. But I guess the good news is that if no one can figure it out exactly, I won't have anyone calling me out if my storyline isn't 100% accurate.

Priene
08-29-2008, 09:19 AM
Thanks for the info. Pri. I spent most of the day trying to track down this information. Even the astronomy experts were having trouble giving me an exact answer as their simulation programs don't calculate the position of stars beyond 6,000 years ago. I'm still pressing them for some guidance on estimating the position of the Pleiades cluster during the time period of my novel. But I guess the good news is that if no one can figure it out exactly, I won't have anyone calling me out if my storyline isn't 100% accurate.

My feeling is that is won't be much at all. The Pleiades are a young star cluster, formed about 100 million years ago and 425 light years away. That means they're extremely young and far away. Constellation shapes change over time because constellations are shapes made of unconnected stars, some close and some far away. The ones nearer move through the sky faster than the further ones (you get the same effect travelling in a car - the roadside shoots by so fast you can't focus on the flowers while the house on a far hill stays in view for a minute or two). So Taurus will have changed a little in its shape, and nobody then would have called it Taurus anyway. Make up your own constellation name and it doesn't matter about constellation shapes.

The Pleiades will have looked more or less exactly as they do now, though, because all the stars formed at the same time and place. If they're close together now, we can be certain they were close together then. I remember a theory that one of the stars might have faded since classical times. It's called the Seven Sisters but most people, me included, can only make out six. With a telescope, on the other hand - wow.

MelancholyMan
08-29-2008, 06:05 PM
To answer your original question: Yes.

-MM

AyJay
08-29-2008, 06:13 PM
FYI - here's the response that I got from an astronomy expert:

Keep in mind that precession over a period of 11,000 years greatly shifts the apparent positions of stars on the celestial sphere. Quite unlike today, the Pleiades in 9000 BC would have been a summer asterism that never rose very high for northern hemisphere observers.

According to my calculations, in 9000 BC the Pleiades would have been located near the winter solstice position of the Sun. The brightest Pleiad, Alcyone, would have been near RA 18:00 hrs and Dec S 21.4. It would have been in opposition to the Sun around the time of the summer solstice, and would have culminated/transited about 40 above the southern horizon in the Canaries. About one month after the summer solstice it would have culminated/transited around 22:00 (10 pm) local time.

The modern standard is to extrapolate backward the Julian calendar for ancient dates, even those before it was invented. However, over great periods of time it gets well out of sync with the seasons because its 365.25-day year is not precisely accurate. In 9000 BC the summer solstice would have occurred around August 24 in the Julian calendar, not late June. Naturally, no one in your story would have been aware of the Julian calendar.

Pri - since you mentioned it, the Seventh Sister myth is a storyline in my novel and provided a lot of my inspiration. I'm still trying to decide which Pleiad to be the lost sister. Calaeno and Sterope are the least brilliant stars. I prefer the name Calaeno for my character, but I'm asking the astronomy "gods" for their opinion.

WriteKnight
08-30-2008, 04:13 AM
Japanese name for the Seven Sisters - "Subaru" - yup, look at the logo.

AyJay
08-30-2008, 09:45 AM
Japanese name for the Seven Sisters - "Subaru" - yup, look at the logo.

Yeah, the Pleiades are pretty cool. They were an important part of many ancient cultures from North America, Europe to Asia.