Chinahand 3,284 Posted August 29, 2019 Author Share Posted August 29, 2019 You could start with Phil Plait's Crash Course Astronomy. For Neptune and Uranus: Comets: Oort Cloud: 1 Quote Link to post Share on other sites
1Enoch 6 Posted September 10, 2019 Share Posted September 10, 2019 Have you got any physical evidence for this bollox? Or is it all just cartoons and pretty images? 1 Quote Link to post Share on other sites
mojomonkey 3,381 Posted September 10, 2019 Share Posted September 10, 2019 1 Quote Link to post Share on other sites
Chinahand 3,284 Posted September 15, 2019 Author Share Posted September 15, 2019 As is probably obvious I gain huge pleasure from heading out with a pair of binoculars or a telescope and looking out at the stars and planets visible in the night sky. Jupiter and Saturn are clear and visible in the early night at the moment and I had the pleasure of seeing Saturn's moon Titan for the first time a few nights ago - it only took half a century plus or minus a bit! My ambition is to get a really good astro-photograph of Saturn hanging delicate in a field of stars ... though that will probably take a couple of years of effort! I'm very very much an amateur astronomer, but the brilliance of the astronomical community is that amateur observations can still matter. Not that long ago an amateur astronomer called Gennady Borisov was taking photographs with a 0.65m telescope out in war torn Crimea and he noticed a tiny spec was moving when he overlaid multiple nightly images. He noted it down as gb00234 and reported its location to the astronomical community, who reacted with interest given the object's unusual position well above the ecliptic - the reasonably flat disc where most planets and asteroids orbit the sun. Soon bigger telescopes were brought to bear, trundling around on their bearings to the correct declination and right ascension reported by Mr Borisov. And these bigger telescopes saw a comet, with a dim tail of gas evaporating off the central nucleus. The comet was named C/2019 Q4 (Borisov) in honour of its discoverer! In the early 1600s, Johannes Kepler was the first person to realise that observations of orbiting bodies fitted to an elliptical curve and to work out how to fit the observations to their one unique conic curve as they travelled under the influence of gravity; and when astronomers did these calculations they got a bit of a shock. Rather than predicting a standard elliptical orbit for a planet, comet or asteroid repeatedly orbiting around the sun, the calculations predicted a hyperbolic trajectory. This object was zooming in from interstellar space, its path scarcely changed by the sun's gravity, before flying off and away back into the interstellar void. It is only the second time in all of history we have knowingly seen such an object. In 2017 the interstellar comet/asteroid Oumuamua zipped through the solar system creating much delight, and queries whether it was an alien space ship - especially when it accelerated away from the solar system! Luckily this time we've caught the object early in its entry of the solar system - Oumamua was only seen when it had already started to leave. However C/2019 Q4 (Borisov) is really screaming through - Oumanua has an eccentricity of 1.2, while Q4 is hyperbolic to an eccentricity of over 3. It is really moving. Predictions have been made that at any one moment at least one interstellar object should be passing through the solar system, but being able to see and observe them is a huge challenge. It was down to the patience of amateurs like Mr Borisov, quietly filling in the observational gaps left by the huge professional telescopes zoomed in to image tiny fields of view. Expect lots of telescope time to be booked to watch Q4's majestic sweep and exit from our tiny stage. Sadly Q4 is unlikely ever to be bright enough for me to see it - my telescope is too small, but over the next few weeks its trajectory will be pinned down with ever greater accuracy and maybe we will be able to back calculate and work out where it came from with some vague accuracy. Just think, billions of years ago some orbital catastrophe jettisoned a comet from its home star system, leaving it travelling the interstellar void. Now after billions up billions of kilometers of travel it is going to grace our solar system for a month or so, before travelling on and on through the galaxy. It is quite a feat to have been able to see and understand just what Q4 is. I hope we learn much more in the next few weeks, all from dots on photographic images, and the spectrum of light reflected back from our sun warming an object which hasn't felt the warmth of a star for many many ions. Just think on that. 3 Quote Link to post Share on other sites
Chinahand 3,284 Posted November 16, 2019 Author Share Posted November 16, 2019 Nice example of orbital resonance in Neptune’s moons: more here: https://www.jpl.nasa.gov/video/details.php?id=1598 Quote Link to post Share on other sites
Chinahand 3,284 Posted November 18, 2019 Author Share Posted November 18, 2019 Not quite sure if I approve of all the Low Earth Orbit Constellations being mooted as solutions to giving everyone high speed mobile internet. I'm sure it'll make Manxy have paroxysms, but I'm more concerned about space debris and ruining the night sky for astronomers. Quote Link to post Share on other sites
Bobbie Bobster 3,422 Posted November 19, 2019 Share Posted November 19, 2019 9 hours ago, Chinahand said: Not quite sure if I approve of all the Low Earth Orbit Constellations being mooted as solutions to giving everyone high speed mobile internet. I'm sure it'll make Manxy have paroxysms, but I'm more concerned about space debris and ruining the night sky for astronomers. Quote Link to post Share on other sites
shasto100 10 Posted November 19, 2019 Share Posted November 19, 2019 We use Inmarsat, Iridium, Thor7 & Thuraya networks at work. Quote Link to post Share on other sites
Uhtred 10,158 Posted November 24, 2019 Share Posted November 24, 2019 This is pretty brain-frying stuff... https://www.theguardian.com/science/2019/nov/20/big-star-energy-record-breaking-explosion-recorded Quote Link to post Share on other sites
Bobbie Bobster 3,422 Posted November 24, 2019 Share Posted November 24, 2019 Gotta have that Big Star Energy! 1 Quote Link to post Share on other sites
ed fournier 49 Posted November 30, 2019 Share Posted November 30, 2019 (edited) Saw the Starlink satellites going across yesterday morning and again today. Pretty incredible sight. So many of them! If you haven’t seen them yet, Sunday morning will hopefully be clear. Set your alarm... https://www.heavens-above.com/AllPassesFromLaunch.aspx?lat=54.2361&lng=-4.5481&loc=Isle+of+Man&alt=0&tz=GMT Edited November 30, 2019 by ed fournier 2 Quote Link to post Share on other sites
finlo 4,876 Posted November 30, 2019 Share Posted November 30, 2019 21 minutes ago, ed fournier said: Saw the Starlink satellites going across yesterday morning and again today. Pretty incredible sight. So many of them! If you haven’t seen them yet, Sunday morning will hopefully be clear. Set your alarm... https://www.heavens-above.com/AllPassesFromLaunch.aspx?lat=54.2361&lng=-4.5481&loc=Isle+of+Man&alt=0&tz=GMT I thought satallites were supposed to be in geostationary orbit? Quote Link to post Share on other sites
GD4ELI 2,753 Posted November 30, 2019 Share Posted November 30, 2019 9 minutes ago, finlo said: I thought satallites were supposed to be in geostationary orbit? Not at all. Check out LEO, MEO and HEO orbits. Quote Link to post Share on other sites
finlo 4,876 Posted November 30, 2019 Share Posted November 30, 2019 11 minutes ago, GD4ELI said: Not at all. Check out LEO, MEO and HEO orbits. For dubious reasons? Quote Link to post Share on other sites
Uhtred 10,158 Posted November 30, 2019 Share Posted November 30, 2019 1 hour ago, GD4ELI said: Not at all. Check out LEO, MEO and HEO orbits. Aren’t they Donald Duck’s nephews? 1 Quote Link to post Share on other sites
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