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In a game of ‘cat and mouse’ with the sun at our members-only solar viewing event, it was mostly cat. The sun struggled to escape the clutches of the clouds as we wheeled out the 90mm Coronado to view the sun in H-alpha in the Meridian Courtyard at the Royal Observatory.
Just over 20 members and guests had signed up for the viewing on Tuesday night and we had an almost perfect attendance record. It was an ideal number of people for the viewing – not too many, not too few – and most people got the opportunity to see some planet-sized solar prominences and a few sun spots (not even the sun is cooperating much these days, with a remarkably quiet period of activity during what is supposed to be the ‘solar maximum’ part of the 11-year cycle).
Many of those who attended had never seen the sun through a solar telescope before, so it was good to be able to offer at least a glimpse of the surface of the sun. And the guests got the opportunity to see why their friend and Flamsteed member gets so worked up about astronomy. (Note to self: bring lots of membership application forms next time.)
At least we had lots of time for questions, answers and general discussion. Nick Phillips’s expert telescope knowledge and Brian Blake’s insight into the workings of the sun came to the fore. We explained the difference between H-alpha and white light filters (including why H-Alpha can’t penetrate clouds: it’ simply part of the visible light spectrum) while explaining that astronomers study the sun in a vast range of wavelengths, including x-rays and even calcium. Nick got to mention what appears to be his favourite word these days – “plage” – as he told about the French-sounding beach-like areas around sunspots. I mentioned the discussion forum as often as I could get away with.
Best question of the evening was, Why does it take tens of thousands of years for sunlight to reach the surface of the sun? Brian explained why, but for the benefit of anyone who was there but didn’t hear his answer, here’s a link that helps unravel that particular mystery.
By 8pm it was a toss-up as to whether the sun would be swallowed up by the clouds or by the trees on the horizon, so it seemed like a good time to call it a day. Nick taught me how to repack the scope to Mike’s satisfaction.
And on the drive home, westward across Blackheath, I lowered the visor as the sun was full in my eyes.
[caption id="" align="alignnone" width="500"]
Quick! Look now and don't blink![/caption]
Posted : 30/07/2014 5:32 pm
Great report, Andy. So sorry that I couldn't be there. Only another week to wait for the next "members only" event... let's hope the weather is kinder next time!
Posted : 30/07/2014 7:01 pm
Yes a great evening. Thanks to Nick for organising. He did a great job. Also thanks to John Belling for the pint and chat. By the way who is that handsome man with long hair in the background?
Posted : 30/07/2014 8:07 pm
By the way who is that handsome man with long hair in the background?
Do you want this as your new profile pic? 😉
Posted : 30/07/2014 10:15 pm
Topic starter
This reply was modified 5 hours, 5 minutes ago by
Brian Blake. Reason: vanity
ROTFL!
Posted : 31/07/2014 1:17 am
Brian, you look like a rock star, man...Why are we so out of sync with these events, everyone I go to you're not there and the ones you go to, I can't! I just want your autograph, that all 😉
Sorry to be missing all these weekday evening members only solar viewing sessions 🙁 Got to make my earning at my evening cricket job so I can buy more telescope accessories!
I too enjoyed reading Andy's report. Which leads me to his
"Best question of the evening was, Why does it take tens of thousands of years for sunlight to reach the surface of the sun?"
I get that. I do. I learnt that from an episode of "How the Universe Works" series (brilliant series by the way, probably the best educational series of how everything works in the universe in layman terms ever imho).
What I dont get is this. If the light photons take so long to reach the surface, then when we look at the sun, why are we saying we are seeing the sun as it was average 8-8.5 mins ago? Why not the tens of thousands of years? Then there is the fact that every single photon's journey length can differ by thousands of years. So one split second, the photon reaching my pupil took 40 thousand years but the next photon that hits my pupil only took 10 thousand years...by that "logic" I expect to see a really messed up image of the sun. But I dont, I see a very organised view of the sun, so the light photons' journey to my pupil must be very orderly.
Perhaps the answer to my question is that the image of the sun we see is only from the point the photon leaves the sun's surface? That would make sense to me but then why? Why not from the moment it was released from fusion? What is the physics of our actual visual perception of the light photon's journey? I get its journey. I just don't get our visual perception of it.
Posted : 31/07/2014 11:34 am
Perhaps the answer to my question is that the image of the sun we see is only from the point the photon leaves the sun’s surface?
Yes, that's correct Tej.
It can take tens of thousands of years for energy to move through the radiative zone of the Sun. However, in the outer 30% of the Sun's radius, known as the Convective Zone, the energy is delivered outwards in about 3 months.
Only when the atoms reach the photosphere, at the top of the convection zone, can the hot atoms cool and release their excess energy once again as photons.
So it's this emission of energy at the photosphere that you are seeing.
Posted : 31/07/2014 12:07 pm
Brian, you look like a rock star, man - Tej please look like! I am a Rock star. Autograph photos available by post reasonable priced. Mike it could be my profile pic.
Posted : 31/07/2014 12:57 pm
Or this photo
Posted : 31/07/2014 12:58 pm
Topic starter
The Flamsteed Twitter account reminded me that we had a great question at the members' solar viewing evening that, in short, we couldn't answer. Question was, why is the sun's corona around 2 million K but the photosphere is less than 6000K?
Flamsteed's Twitter carries a link to a Science Daily story which might [pun alert] shed some light on the subject.
Posted : 02/08/2014 2:02 pm
