[HPforGrownups] Re: Mars is Bright Tonight

[Shaun Hately]

No: HPFGUIDX 42467

On 10 Aug 2002 at 23:50, Phyllis (erisedstraeh2002) wrote:

> Such good fortune to have an astronomer respond to my post (wonder if 
> I could have anticipated it from looking at the night sky <grin>?)! A 
> most generous offer, thank you! Some dates that come to mind include 
> the night Lily and James died (October 31, 1981) and the night of the 
> detentions in the Forbidden Forest (May 26, 1992).  But looking at 
> such a map would be meaningless to me - would you be able to do some 
> interpretation as well?

I can certainly explain what the maps show - as for interpretation, I'm an astronomer 
- not an astrologer. I am concerned with the science of astronomy - not things like 
horoscopes, star signs, etc, that are covered in the areas of astrology, and I really 
can't give any commentary on that - but there may well be people who understand 
astrology on the list, and if they'd like to use the maps I put up, they are welcome to 
- given the Harry Potter universe does make use of divination and the like, such 
interpretations might be rather interesting.
 
I have put up Skymaps for England on October 31/November 1, 1981, and Scotland 
on May 26/27 1992 at http://www.alphalink.com.au/~drednort/harrystars.html

I'll talk about the Scotland one a bit below - but even with my limited astronomical 
knowledge, something quite unusual strikes me about the October 31 England map 
- from 7.03pm (when Mars set) till 5.40am (when Saturn rose), there were no 
planets in the sky over England - that's an unusually long period for there to be not 
one of the 9 major planets visible.

Phyllis:
> Is there any other way to explain the centaurs' focus on the 
> brightness of Mars that night other than that Mars was in opposition 
> at the time?  If not, then it could be that JKR wasn't trying to 
> reconcile the dates to actual events (as the Lexicon points out, 
> there are other time discrepancies, so perhaps JKR doesn't feel the 
> need to make all of the dates make sense).  So if this is the case, 
> we might not be able to glean much from looking at maps of the night 
> sky when certain key events happen.  But then again, it could show 
> something <you never know>!

Well, with regards to the brightness of Mars.

Astronomers measure the brightness of objects in the sky, in terms of 'visual 
magnitude' - it's a scale of numbers we use to indicate how bright something 
appears. The lower the number, the brighter the object. The naked eye can see 
about as high as Magnitude 6.5. The sun is magnitude -26.5, a full moon is -12.5, 
the brightest star is Sirius at magnitude -1.5. The magnitude of stars remains pretty 
constant - that of planets changes based on a number of factors - most importantly 
how far away from us they are. Mars can be anywhere from Magnitude -2 to 
Magnitude 2.

Calculations show me that for 26th May 1992, Mars was at approximately 
Magnitude 1.18 - in other words, in the fainter part of its cycle. The bigger problem 
might be the fact that it didn't rise until a little after 2am - but that's another issue...

I'm going to look at the night sky over Scotland (I'm actually using Glasgow for 
anyone who wants precision - but Scotland is small enough, it doesn't make a lot of 
difference) around 3.00am, on the 27th May 1992 (the morning of 26/27th). The 
reason for choosing this time is that it allows Mars to actually be visible to Ronan. 
We know the detention started around 11pm, and three and a half hours to the time 
they encountered Ronan does seem quite a long time, but Filch did seem to expect 
that whatever they had to do would last until dawn.

Mars is at magnitude 1.18 - even though it's at the fainter part of its cycle, it is 
always one of the brightest objects in the sky. At 3.30am, 26/5/1992, of the other 
bright planets - Mercury, Venus, Jupiter, and Saturn, only Saturn is actually up (at 
magnitude 0.44 in the Constellation Capricorn). The moon is visible. There are 
around 16 or 17 stars that are brighter than magnitude 1.18. Of these, the following 
are visible:

Altair
Capella
Arcturus
Pollux
Vega
Antares
Spica

Including the moon, Mars is the 9th brightest object in the sky over Scotland at that 
time. Given that Hogwarts seems to be a fair distance from any cities, it probably 
has good seeing in astronomical terms - so Mars would be the 9th brightest object 
out of thousands visible. It'd stand out.

Especially where it is located - yes, there are seven brighter stars up there 
somewhere, but none are anywhere near Mars - the closest bright object (except the 
Moon) are Alpheratz and Hamal - and neither of them are below magnitude 2.

Mars isn't unusually bright on 26th/27th May 1992 - but it is bright enough to 
dominate the northeastern sky over Scotland. I don't think it's unreasonable that 
Ronan would have commented on that.

Yours Without Wax, Dreadnought
Shaun Hately |webpage: http://www.alphalink.com.au/~drednort/thelab.html
(ISTJ)       |email: drednort at alphalink.com.au | ICQ: 6898200
"You know the very powerful and the very stupid have one thing in
common. They don't alter their views to fit the facts. They alter
the facts to fit the views. Which can be uncomfortable if you happen
to be one of the facts that need altering." The Doctor - Doctor Who:
The Face of Evil | Where am I: Frankston, Victoria, Australia