A team of astronomers from Armagh Observatory and Buckingham University say that the discovery of hundreds of giant comets in the wider planetary system over the last 20 years implies these objects pose a greater hazard than asteroids. The key here is that mainstream astronomers have calculated the asteroid threat over hundreds of thousands of years. The implication is that the threat from giant comets is over thousands of years – but are these numbers just drawn out of a hat.
Mark Bailey and David Asher (Armagh) and Bill Napier and Duncan Steel (Buckingham) published their researchin the December issue of Astronomy and Physics, the journal of the Royal Astronomical Society – see http://phys.org/print369998142.html
You can view a talk by Mark Bailey to an SIS meeting in Watford last September (2015) elsewhere on this web site (video recording).
These giant comets they have in mind are otherwise known as Centaurs and they are typically 50 to 100km across – or larger. These are monster comets and a single centaur combines more mass than the entire population of earth crossing asteroids found to date (all 13,500 of them presumably). Centaurs are sometimes deflected into orbits that enter the inner solar system, like any other kind of comet. These will eventually disintegrate into dust and fragments as all comets sublimate when approached by gusts of solar wind. All this material will tend to flood the inner solar system with cometary debris and they think this occurred in the historical past. They say that a centaur arrived around 30,000 years ago and is the course of time left behind trails of debris ranging in size from dust particles to lumps of comet that are more resistant to break down and these could be several km across. On that basis some of the dark asteroids in the inner solar system, including the bus that sailed past a few days ago, may be remnants of the centaur. This is in effect a revision of the Clube and Napier hypothesis as in that they visualised the arrival of a giant comet from the Oort Cloud, theoretically situated in the outer regions of the solar system. It seems they now have a more likely candidate for the dirty work – a centaur (and the second part of the name is quite apt, as they also theorise it gave birth to the Taurus meteor streams). These meteoric streams, the remnant of the passage of said centaur/comet, are likewise associated in their theory with specific episodes of environmental upheaval such as the Younger Dryas event and the 2300BC event (as described by Moe Mandelkehr in various SIS articles over the years). We might add to that, tentatively of course as no one has actually researched the possibility, the twin catastrophes between 40 and 30,000 years ago, the Oldest and the Older Dryas events, and various lesser upheavals during the Holocene period – most notably at 8200 years ago, 5000 years ago, and 1200 years ago (orthodox dates). Clube was keen to extend these episodes to the 6th century AD and even thought there might be a connection with the Little Ice Age.
You can read the full article at http://cosmictusk.com/william_napier-asher-bailey-steel-comet-centaur/… as posted by George Howard. See also https://www.ras.org.uk/news-and-press/2758-giant-comets-could-pose-dange…
At http://phys.org/print370001487.html …we have an update. Most studies of potential earth impacts focus on objects in the asteroid belt, which is situated between Mars and Jupiter, but the discovery of hundreds of monster comets (centaurs) with much larger orbits than the asteroids, requires an expansion of the hazard risk. Centaurs cross the paths of Jupiter, Saturn, Uranus and Neptune and occasionally they can be deflected into the inner solar system – becoming a threat to Earth and Mars and Venus etc. As they orbit the Sun they would gradually break up into smaller components, a family of comets if you like, just like any other kind of comet. This would result in a series of massive debris trails that would inevitably inter-act with Earth. The orbit of the latter could hardly escape being caught up in the debris trails on a cyclic basis, over and over again (punctuated with periods of quiet). However, the team are emphasizing there is no immediate risk – and they are more concerned with nailing down what has occurred in the past rather than worrying about what might happen in the future. The course of civilisation was affected – even as late as the Bronze ages.
See also www.sciencedaily.com/releases/2013/07/130725151523.htm … and going back a couple of years we have a report from the WISE survey of the heavens (actively looking for Near Earth Objects) NASAs Wide-field Infrared Survey Explorer. Here they came to the conclusion that most centaurs were actually comets – or comets in limbo (in-active but not necessarily in-active all the time). The real identity of centaurs had been an enduring mystery to astronomers but if most are now defined as giant comets there is no mystery any longer. James Bauer at NASA JPL in Pasadena in California was lead author of a paper published in The Astrophysical Journal (July 2013) and they accept they probaby originated from deeper out in the solar system (the Oort Cloud is difficult to abandon it would seem). Bauer went on to say they have unstable orbits in an unstable belt and ultimately, gravity from the giant planets will fling them either closer to the Sun or further away from their current location. This appears to be what got Bailey, Asher, Napier and Steel aroused enough to write the new paper, regurgitating the Taurid Complex hypothesis (which had gone very quiet in recent years) as the two things seemed to be mix and match piece of perfection. Back in the 1990s they caused a few ripples – but without strong evidence it never gained too much traction. Now they have just the tinder to light the match again and bring their ideas in out of the dark. The discovery of Centaurs as giant comets has provided them with a new pitch on which to play.
See also www.dailygalaxy.com/my_weblog/2015/12/destination-earth-stephen-hawking-… … and in this version of the story we have Stephen Hawking brought forth as a decade ago he said that the lack of intelligent life in our galaxy may be the result of asteroids and comets colliding with inhabited planets. We are then introduced to Bailey et al and their article. It also ties in the 1993 Comet Shoemaker-Levy collision with Jupiter and the NASA New Horizon spacecraft. Having flown past Pluto a few months ago it is now destined to meet up with a 45km wide trans-Neptune object at the end of 2018. It then moves to the Cassini Mission and an image of a moon of Saturn which appears to be a captured Centaur (or that is the theory espoused by the author). Very little is actually said about the new paper – but as mentioned previously you can download it in full from http://cosmictusk.com/william_napier-asher-bailey-steel-comet-centaur/ and at that location you will also be able to have another look at rehe Han Kloosterman article in SIS Review 2015:3 (and the comments) as well as William Thompson's 'Catastrophist' list of papers and authors (also reached elsewhere on this web site) – go to http://cosmictusk.com/kloosterman-a-man-before-his-time/