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Äàòà èçìåíåíèÿ: Mon Oct 1 12:49:59 2012 Äàòà èíäåêñèðîâàíèÿ: Tue Oct 2 03:54:47 2012 Êîäèðîâêà: koi8-r Ïîèñêîâûå ñëîâà: earth orbit |
From: TerryMoselaol.com
Subject: Lecture, Fireballs, Daft Dust, QUB Lecture, Meteorites, ISS, Comp, Mars, P/ISON
Date: 1 October 2012 00:50:40 BST
Hi all,
á
1. IAA LECTURE: "Tuning in the Radio Sun,á & the LOFAR Observatory At Birr", Wed 3 October.
Theá next lecture of the IAA'sá new season will be given by Dr Peter Gallagher of Trinity College. Peter is currently Chairman of the Astronomical Science Group of Ireland, and runs the Rosse Solará Observatory at Birr Castle. He also leads the Irish LOFAR project: LOFARá is one of the post important and powerful projects in radio astronomy which is providing new insights in almost every area of astronomy. He isá also a proud graduate of QUB.á
á á As we head towards the next solar maximum, expected next spring, there is renewed interest in our nearest star, whose vagaries are not only fascinating, but of vital interest to life on Earth.á
á á VENUE: Bell Lecture Theatre, Physics Building, Main campus, Queens' University, Malone Road, Belfast. Time: 7.30 p.m., Wednesday 3 October.á Doors open from about 7.10. Admission Free, including light refreshments. All welcome.
á
2. Amazing Fireballs: Reports are still coming in from all over Ireland about the amazing multipleá fireball which travelled over the UK & Ireland on 21 September. If you haven't already sent one, please do so asap.
á á
3. DAFT & DANGEROUSá DUST: I don't usually stick my neck out and criticize professional astronomers, but this is one of the daftest and most dangerous ideas I've come across in this subject area. Basically, the proposal is to combat global warming by using a mass driver toá move a massiveá asteroidá to the L1 Lagrangian Point (between Earth & Sun) and then blasting a huge cloud of dust off it to block some of the sunlight reaching Earth. See
á The proposal says that the ideal candidate asteroid is 1036 Ganymed. A few relevant facts:
It is an AMOR class,á approximately spherical, diameter 32km. It's an S-type, comprising mainly magnesium silicates & iron.
Mass: 3.3 x 10 >16 Kg (33,000,000,000,000,000 tonnes)
Perihelion distance 1.233 AU (115m miles, 184.5 m Km)
Period 4.34 years
Mean orbital distance from Sun: 2.662 AU (398m km) (for comparison, Mars is 1.52 AU)
Eccentricity 0.537
Inclination 26.6 degrees.
Rotation period 10 hours
Next close pass to Earth: 13 Oct 2024, distance 56 millioná km.
PROBLEMS:
1. We are unlikely to be able to build a powerful enough mass driver to move such a massive asteroid at a significant rate within the next 50 years.
2. Even if we could build it, we would need a HUGELY powerful rocket to transport it to Ganymed, then slow it down enough to land it on the surface. Even transporting it in sections and assembling it there would be well beyond our capabilities for the foreseeable future.
3. The only way to provide it with enough power would be with a big nuclear generator, which poses its own problems and risks, or with aá VAST array of solar panels, which would not work for half of its rotation period.
4. In any conceivable scenario it would take at least 100 years to moveá its perihelion iná as far asá the L1 point, 1.5m km inside theá Earth's orbit. Think about it: on average, it lies 250 million km outside the Earth's orbit!á At aphelion itá goes closer to Jupiter than to Mars!)
5. It would then take another 50 - 100á years to circularise the orbit (remember the eccentricity is 0.537 Earth's orbital eccentricity is a mere 0.0167)á
6. And the inclination is 26.6 degrees - that's very high, and that would have to be reduced to zero, which would take a huge amount of energy and time. For comparison, apart from odd littleá Mercury (i = 7.0 degrees), the highest of any of the planets is Venus at 3.395 degrees.
7. If instead,á theá inclination is reduced as the asteroidá is gradually beingá brought in to Earth's orbit, then it is going to come increasingly close to Earth each orbit. That is not only dangerous (obviously!), but the gravitational interaction with the Earth each orbit is going to GREATLY exceed the effect of the mass driver, and disturb the orbit of Ganymed, quite possibly puttingá its orbit out of control altogether! You can't just nudge an object of that mass quickly through the Earth's orbit when the Earth isn't there! So if you leave it with a high inclination until it is inside the Earth's orbit, and only then reduce the inclination, you add even longer to the timescale.
8. When (and if!) you get it stabilised at the L1 Lagrangian point, 1.5 million km on the Sunward side of the Earth, the proposal is to blast off a huge cloud of dust from its surface, to reach a diameter of 1,600 km around the asteroid.
9. Their estimate involves blasting off 5 x 10 >14 kg of material off its surface. That's 500,000,000,000,000kg. Look at the present mass of the asteroid - they propose to blast almost all of it off into space!á How long would that take? 100 - 200á years?
10. The idea is that the mass of the asteroid would keep the dust cloud in place. What asteroid? - there wouldá now beá only a tiny fragment left! OK, the dust cloud will have its own mass, and the overall total will be much the same, but since it won't be concentrated centrally it will be much easier for particles to drift away.
11. And if they are going to use solar panels to power the mass driver -á er, there's a problem: they will get so coated by dust that they will cease to work before the job has hardly started. Even if they have an automatic self cleaning mechanism, the dust cloud itself will block so much sunlight that their efficiency will be greatly reduced.
12. Even with the mass of the asteroid/dust cloud, a lot of particles will be driven away by the pressure of sunlight (radiation pressure), the Poyntingá - Robertson effect, and the Lorentz force.á
13:á Every New Moon, particularly those occurring at apogee, will pull away some of the particles on the nearest edge of the cloud, gradually depleting it - perhaps as fast as it is being generated.
14. For such a totally untried and untested idea, the precision they quote for the amount that solar radiation would be reduced is both ridiculous and alarming: 6.58%. Notá 'about 6 or 7%'. Not evená '6.6%'. No, it would beá 6.58%. That implies a degree of knowledge of all the parameters which we can't even approach, and it's dangerous to imply that we do. (The original paper may have some caveats or error barsá on that point, but even so, there are just too many unknowns.)
15. And anyway,á 6 - 7% would probably be too much - it could induce another major ice age!
16. All factorsá considered, it is unlikely that such an asteroid could be manoeuvred to the L1 point, and the required dust cloud created, within 200 years. We need a solution to the problem WELL before then. Does 200 years seem like a very long time? Well, it's over 50 years since we last set foot on the Moon, and it's unlikely we will do so again within the next 10-15 years, let alone build a base there. And this 'daft dust' idea is immeasurably more challenging than getting man to the Moon, or even to Mars.
17. An alternative proposal to use several smaller asteroids insteadá is only slightly less ridiculous.
á á BUT the most dangerous part of this whole idea is that it encourages theá irresponsible further addition of CO2 and Methane to the Earth's atmosphere because those with a vested interest, or callous indifference to the problem, can rely on ideas like this saying 'There's no problem - and if there is, sure we can fix it.'
á á I'm only a humble amateur, but would it not be simpler to stop creating the problem in the first place? (I know that not everyone agrees that GW is occurring, or that it is anthropogenic, but that is certainly the majority view, and even if human activity is not the main source - why make it worse?)
Rant over.
á
4. QUB/IAA PUBLIC LECTURE: The next in the QUBá Michael West Public Astronomy Lecture Series is entitled "The Sun", andá will be on October 17.á It will be given by well known astronomer Dr Lucie Green (you probably saw her on Stargazing Live on BBC, and she has previously given a lecture to the IAA in Belfast). She is a recognised expert on the Sun, and her talk is sure to be fascinating.á These lectures are held in conjunction with the IAA, and form part of our regular fortnightly programme. However, due to the larger than usual numbers expected, it will be held in the Larmor Lecture Theatre, also in the Physics building, instead. Admission is free, but places must be pre-booked. see: http://tinyurl.com/MichaelWestLectureSeries2012
á
5. "Meteorites Tamed" Lecture Series, Ulster Museum, by Dr Mike Simms
Mondays at 7.30pm, 22nd October Á€“ 26th November 2012
Free. Booking for each lecture essential: Go to www.nmni.com, Telephone 028 9044 0000
(Lines open Tue Á€“ Sun 10am Á€“ 6pm), Email: ulstermuseumreceptionnmni.com
SYNOPSIS: Every year visitors from Outer Space arrive on Earth. These are meteorites, messengers from beyond our planet. This series of six lectures from Dr Mike Simms will explain what meteorites are, where they come from, how they get here, and what they can tell us about the far reaches and earliest history of our Solar System.á
6. The International Space Station (ISS)á isá coming to the end of aá series of 'Morning Passes' over Ireland. It will then commence a series of evening passes on 11 / 12 October.á See www.heavens-above.com for details for your own location.
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7. ODYSSEUS SPACE CONTEST FOR EU SCHOOLS: (From Robert Hill): This is a nice challenge for schools in Ireland, North and south. See http://www.odysseus-contest.eu/
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8. Free Astronomy App:á Some of youá may be interested in this free app for iPhones and Androids/Smartphones: http://www.google.com/mobile/skymap/á (thanks to Nicola Armstrong for the suggestion)
á
9. GALE CRATER SET FOR SUMMER HEAT WAVE?
From: European Planetary Science Congress (EPSC) 2012 Press Releaseá
á á á Preliminary weather reports from the Curiosity's Remote Environment Monitoring Station (REMS) are showing some surprisingly mild temperatures during the day.á Average daytime air temperatures have reached a peak of 6 degrees Celsius at 2pm local time.á A Martian day Á€“ known as a Sol Á€“ is slightly longer than Earths at 24 hours and 39 minutes.á Temperatures have risen above freezing during the day for more than half of the Martian Sols since REMS started recording data.á Because Mars's atmosphere is much thinner than EarthÁ€™s and its surface much drier, the effects of solar heating are much more pronounced.á At night the air temperatures sink drastically, reaching a minimum of -70 degrees just before dawn.
á á á NASAÁ€™s Mars Science Laboratory touched down in Gale Crater on 5th August 2012 close to the equator of Mars at a latitude of 4.5 degrees south.á The southern hemisphere of Mars is approaching springtime, leading to speculation about possible temperatures for at the height of Martian summer.á
á á Á€œThat we are seeing temperatures this warm already during the day is a surprise and very interesting,Á€ says Dr Felipe Gö¨mez of the Centro de Astrobiologöa in Madrid.á Á€œItÁ€™s very early days and we are only now being able to test our models against REMS observations.á If this warm trend carries on into summer, we might even be able to foresee temperatures in the 20s Á€“ and that would be really exciting from a habitability point of view.á In the daytime, we could see temperatures high enough for liquid water on a regular basis.á But itÁ€™s too soon to tell whether that will happen or whether these warm temperatures are just a blip.Á€
10. MORE HYPE on COMET ISON:
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11. School of Theoretical Physics Statutory Public Lecture 2012 in association with the School of Cosmic Physics
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"Cosmic perspectives: from planets to the multiverse" by Professor Martin Rees, Baron Rees of Ludlow, O.M., F.R.S.
Mon 19 Nov 6:30pm, Theatre L, Newman Building, Arts Block, UCD. Admission free.
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12. INTERESTING WEBLINKS:á
http://www.huffingtonpost.co.uk/2012/09/28/black-hole-particle-jets-_n_1921991.html
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13. Skymaps:á You caná download currentá SkyMaps here: www.skymaps.com
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14. TWITTER:á the IAAá now has a twitter account:á IaaAstro
15. BBC THINGS TO DO WEBSITE: See theá forthcoming IAA events on á
http://www.bbc.co.uk/thingstodo
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16. JOINING the IRISH ASTRONOMICAL ASSOCIATION is now even easier: This link downloads a Word document to join the IAA. http://irishastro.org.uk/iaamembership.doc. If you are a UK taxpayer, please tick the 'gift-aid' box, as that enables us to reclaim the standard rate of tax on your subscription, at no cost to you.á See also www.irishastro.org.á
á á
Clear skies,
Terry Moseley