I didn't think rings were common either. It looks like the difference between asteroids and comets is one has more metal and the other has more ice to form tails. I guess the combination has some of both.
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I didn't think rings were common either. It looks like the difference between asteroids and comets is one has more metal and the other has more ice to form tails. I guess the combination has some of both.
First fuzzy shots of Pluto, from earthsky:
Here's a link showing the bright spots on Ceres which may be made of ice: http://www.nature.com/news/mystery-o...-grows-1.17313
Popular Astronomy sends subscribers email updates from time to time. Some of these are quite interesting. Below is a part of one which is on Mars. Funnily enough Immanuel Velikovsky wrote about this in the 1950s, that Venus was originally a comet (or perhaps a giant asteroid captured by the earth's gravitational pull to bring it into orbit and the clashes with Mars over many generations (I think it was every 50 years) took place until Venus established itself in a separate orbit.
Anyway, I was fascinated by the book on this I read, Earth in Upheaval, as well as the first of two books on how the ancient history of Egypt got muddled up with repeating events 50 years apart (Ages in Chaos).
METEORITE MAY REPRESENT BULK OF MARS' CRUST
Brown University
NWA 7034, a meteorite found a few years ago in the Moroccan desert, is like no other rock ever found on Earth. It has been shown to be a 4.4-billion-year-old piece of the crust of Mars and, according to a new analysis, rocks just like it may cover vast swaths of Mars. In a new paper, scientists report that spectroscopic measurements of the meteorite are a spot-on match with measurements from orbit of the Martian dark plains, areas where the planet's coating of red dust is thin and the rocks beneath are exposed. The findings suggest that the meteorite is representative of the 'bulk background' of rocks on the Martian surface. When scientists started analyzing the meteorite in 2011, they knew that they had something special. Its chemical make-up confirmed that it came from Mars, but it was unlike any other Martian meteorite. Previously, all the Martian rocks found on Earth were classified as SNC meteorites (shergottites, nakhlites, or chassignites). They are mainly igneous rocks made of cooled volcanic material, but the new object is a breccia, a mash-up of different rock types welded together in a basaltic matrix. It contains sedimentary components that match the chemical make-up of rocks analyzed by the Mars rovers. Scientists concluded that it is a piece of Martian crust -- the first such sample to be found on the Earth.
Scientists thought it might help to clear up a long-standing enigma: spectra obtained from SNC meteorites never quite match remotely-sensed spectra from the Martian surface. So after acquiring a chip of the meteorite, they used a variety of spectroscopic techniques to analyze it. The researchers say that the spectral match suggests that the 'dark plains' on Mars are dominated by brecciated rocks similar to the new meteorite. Because the dark plains are dust-poor regions, they are thought to be representative of what lies beneath the red dust on much of the rest of the planet. The researchers claim that, in the light of what is known about Mars, the idea that the surface would be rich in such breccias makes sense. Mars has more than 400,000 impact craters more than 1 km in diameter. Because brecciation is a natural consequence of impacts, it is to be expected that material similar to NWA 7034 has accumulated on Mars over time. In other words, many of the rocks on the surface of Mars are probably very similar to the meteorite.
The first 3 volumes of Velikovsky were Worlds in Collision (about Mars and Venus as Venus jostled with Mars to clear her orbit, Earth in Upheaval looking at the evidence for violent upheavals on earth, and Ages in Chaos, which look at periods of history which historians unwittingly duplicated. The first was From the Exodus to King Akhnaton which deals with the Israeli exodus and crossing the Red Sea when the waters part. The book is very scholarly and I am not able to judge it as I can't read the Old Testament Book of Exodus in its original Hebrew, but it seems to me that he makes a case for the fact that scholars made an erroneous duplication of ancient history, based on the series of plagues and the violent physical upheavals in the Middle East. I have not read Vol. 2 of Ages in Chaos: Ramses II and His Time but the 2 volumes put the case for a double-counting of the plagues and upheavals that were the results of the periodic Mars-Venus near-collisions. Another Volume Mankind in Amnesia explains the disjunction as a collective amnesia on the part of historians of the time.
Velikovsky's massive work was subject to a storm of critique and led to the banning of his books by so many prominent historians of the time that the publishers caved in and withdrew the books from publication. This was the 1950s when the Cold War was at its height. But I also read Alfred De Grazia The Velikovsky Affair (published in 1966) which attempted to defend Velikovsky. The worst period of McCarthyism was over but the damage had been done by then.
His works have been re-published in their original entirety in 2009 (paperbacks) by Paradigma Books.
I had not thought of Venus being originally a comet or asteroid before. It is even amazing to me that brecciated rocks from Mars' surface can reach the Earth. Although Velikovsky's view seems unusual, one way to check it is to see how long ago Venus was recognized in the sky as a planet.
Yes, that is one way. Velikovsky goes into this in some detail. The 4 planet system - Saturn, Jupiter, Mars, Mercury - were identified in the ancient hindu table of planets, Venus was not there (planet in Greek means "wanderer", as the planets did not follow the stable pattern of the sun and moon). Later they realised that this was because they don't go round earth as they at first believed but round the sun. Venus was a comet as it had a "tail", it "smoked".
That is it in a nutshell.
It looks like Velikovsky's theory passed my initial attempt at falsification. It makes me wonder what those early Hindus thought about Venus.
i wonder why beltQuote:
Originally Posted by free
this is usually something you buckle
or the expression
a belter
but three to form a belt is rather strange
The belt is just one obvious part of the constellation of Orion (the hunter) which looks a bit like an archer shooting a bow. The belt is very distinctive, and the easiest to distinguish. I can't find an image of the entire constellation, but this one of the belt and the armpit of Orion (Betelgeuse) is the best I can find atm.
OK I found it, middle picture here.
thanks i find the names given rather hidden.Quote:
Originally Posted by Dreamwoven
I am not quite sure why hunter exactly but there you go each to their dreams.:)Quote:
Originally Posted by Dreamwoven
I agree, it is a bit Rorschach-like and why the lines are drawn between stars they way they are is never explained. Bt seeing the whole of the Orion constellation I can see the left arm raised and two stars being the fingers of the left arm, after loosing an arrow. Orion also has 2 hunting dogs - Canis Major and Canis minor. I can't for the life of me see a dog in either of these constellations. Canis Major includes the brightest star in the heavens, Sirius.
But how they work out the names of the constellations is beyond me.
The text below is from the Society for Popular Astronomy. It shows the extreme violence of interstellar space.
At our London meeting this Saturday, 25 April, our Vice President, Prof. Tim O'Brien, will talk about novae – exploding stars.
Several times each year a new star appears in the night sky. Dubbed novae by astronomers of the past, we now know these are explosions on white dwarfs in binary star systems which can eject around an Earth’s mass of material into space at speeds of thousands of kilometres per second. The white dwarf is not destroyed in these outbursts and the nova lives to explode again – in some cases within the lifetime of a single astronomer.
Novae are now detected right the way across the spectrum from radio waves to gamma rays. Prof. O'Brien will describe the latest observations and what they teach us about these interesting astrophysical phenomena – stellar explosions that are sometimes visible to the unaided eye from our own backyards!
This replaces the talk by Dr Lewis Dartnell previously advertised.
Following the break, Robin Scagell talks about forthcoming events in the night sky, and Dr David Mannion looks at The Future of Space Travel. Where will we go after the tremendous Apollo missions, the Mars Rover and the exploration of our Solar System by interplanetary robots? Will we have bases on the Moon and Mars by the end of the 21st Century?
The meeting takes place at SOAS, University of London, starting at 2 pm. More details, and a map of how to get there, are given on the SPA website.