The much-anticipated Comet C/2012 S1(ISON) has been plummeting towards its near-rendezvous with the sun, picking up speed as it does, and this week the comet suddenly brightened dramatically and changed its appearance.  

This article from Phil Plait of Bad Astronomy, writing over at Slate, showcases some of the outstanding photographs which observers around the world have been capturing of the comet as its appearance becomes more and more spectacular.  

His article also discusses the reasons Comet ISON might have suddenly brightened, the reasons comets begin to sport multiple tails as they approach the sun, and the factors which influence the coloration of those different tails.  Here's a link from that article to an incredible photograph captured on November 15th by talented photographer of the heavens Damian Peach.

Comet ISON is now inside the orbit of our planet, closer to the sun than we are, which means that we on earth need to look towards the sun in order to locate it.  That means that, like Mercury or Venus (which are also, of course, orbiting closer to the sun than we are), it must be observed near sunrise or sunset, depending on its location.  In its current location, Comet ISON is found by looking to the east prior to the sunrise.

There are several good resources to help observers who want to look for Comet ISON.  While some skilled observers with excellent viewing conditions have reported locating Comet ISON with the naked eye, binoculars or a telescope are recommended.  Over the next few days, the comet is very close to the important star Spica, in Virgo, early in the morning prior to sunrise (Spica rises a little after 4 am right now for observers at the latitude of the Great Pyramid, and rises about four minutes earlier each morning).

Here are several resources which give directions to help observers locate Comet ISON in the predawn sky:
  • Skyhound's "Chasing Comet ISON."
  • Sky charts from Sky & Telescope showing the paths of Comet Lovejoy (higher in the morning sky than Comet ISON and nearly as bright!) and Comet ISON.
  • An excellent article with sky diagrams written on November 16 by Paul Sutherland at his Skymania site.
There are also numerous previous posts on this blog discussing the location of the constellation Virgo and how to find it, including this one, this one, and this one.

While almost every article you see about Comet ISON will declare that this is its first time through the solar system after being ejected from the hypothetical Oort cloud, there are solid reasons that individuals with open minds should question this assertion.

First of all, there are tremendous problems with the Oort cloud theory.  While the Oort cloud theory has many different variations, all of them posit an origin for comets at an incredible distance, and that poses some king-sized problems for subscribers to that theory.  This previous post discusses some of those problems, and refers to the work of Thomas Van Flandern, former Chief of Celestial Mechanics at the US Naval Observatory, who pointed out the huge problems with the Oort cloud theory and offered his own counter-hypothesis, which was that comets came from an exploded "fifth planet" in the solar system (which would have been located between Mars and Jupiter).  He also pointed out that Jan Oort himself "always maintained that an origin of comets from within the solar system, perhaps in connection with the event which gave rise to the asteroid belt, was the most probable" (footnote "e"on page 191 of Dr. Van Flandern's book Dark Matter). 

While Dr. Van Flandern maintains that an exploded planet from inside the orbit of Jupiter is the "only dynamically viable" alternative to the theory that comets come from far outside the solar system in the hypothetical Oort cloud (an assertion he makes on pages 179 and 218 of the book), the hydroplate theory of Dr. Walt Brown also proposes a theory that would explain aspects of comets that the Oort cloud cannot explain: that comets were ejected from earth during a catastrophic event, an event which also explains several hundred other pieces of evidence in the solar system and on earth which pose king-sized problems of their own for conventional theories.

In his online book, Dr. Brown devotes an entire chapter to discussing the origins of comets, and the evidence which defies explanation by hypotheses that have been proposed thus far, including the exploding planet theory and the various Oort cloud theories.  One of the biggest problems for the Oort cloud theories is the difficulty of explaining the very high number of comets in "Jupiter's family" -- comets whose orbit takes them to an aphelion (farthest point from the sun) that is between 4 and 6 astronomical units (AU -- defined as the average distance of the earth from the sun), whose orbital distance is 5.2 AU.  Dr. Brown discusses this problem on this page in his comet chapter.

The problem posed by Jupiter's family stems from the fact that if a comet really originates in the hypothetical Oort cloud, thought to be around 50,000 AU from the sun, that comet's velocity by the time it comes into the solar system is so high that slowing it down enough to join Jupiter's family is very hard to accomplish without ripping the comet apart completely.  It is possible that just the right interactions with multiple planets on the way into and/or out of the solar system could have slowed a comet down in just the right way to allow it to fall into Jupiter's family, but the high number of comets in Jupiter's family, and the fact that astronomers have noted that life in Jupiter's family is also very dangerous for a comet (with increased chance of collision with Jupiter, among other factors), bringing the life expectancy of a comet in Jupiter's family down to 12,000 years, makes an Oort cloud origin extremely unlikely.

Another important grouping of comets is composed of comets with aphelions far beyond those in Jupiter's family -- reaching distances beyond 500 AU before falling back towards the sun.  These comets have orbits that are "nearly parabolic" -- if they were to accelerate just a little more on the way out, they would escape the gravity of the sun altogether and never return.  A comet with enough energy to escape the solar system has an orbit that is termed "hyperbolic" (the boundary line between an elliptical orbit and a hyperbolic orbit is a parabola).

However, despite of the large number of comets with orbits that are near-parabolas ("just this side" of going hyperbolic), and despite the fact that incoming near-parabolic comets sometimes receive a boost in velocity and exit the solar system on a hyperbolic trajectory, no comets come in towards the sun with hyperbolic orbits.  As Dr. Brown explains in the discussion surrounding diagram 165 in his current online version of his book, "Incoming hyperbolic comets have never been seen -- a very important point" (italics in original).

This means that comets may be coming back into the inner solar system for the first time, but that based on their trajectories we cannot dogmatically declare that they have never been here before.  If they have orbital trajectories that are nearly parabolic, but that were not hyperbolic on their incoming journey, it is possible that they came from an explosive event in the inner solar system (either from earth or from an exploded "fifth planet")  and that their initial velocity was insufficient to allow them to escape.  Some comets from that initial catastrophe may have had enough velocity to escape, but of course they did not come back.  Those that we see coming back may be coming back for their first return journey, but if they are not coming in with an incoming hyperbolic trajectory it is possible -- even likely -- that they have been here before, at least once.

Thus, if the hydroplate theory is correct (and it would provide very satisfactory explanations for numerous other pieces of comet evidence discussed by Dr. Brown in his book [as well as the recent discovery of an object in the asteroid belt behaving like a comet], in addition to the large numbers of comets in both Jupiter's family and in the group with near-parabolic orbits), Comet ISON is not coming in for its very first visit to the inner solar system.  It has been here at least once before, even if only on its way out.  All the blogs and articles declaring that this is the comet's first visit (such as this one from the NASA website declaring that Comet ISON is "made of pristine matter from the earliest days of the solar system's formation" making it extremely valuable to scientists -- "a time capsule from when the solar system first formed") are wrong.  That in itself is an extremely important possibility which should cause scientists to carefully consider the hydroplate theory.

However, Dr. Brown discusses an even more astonishing possibility.  Apparently, Comet ISON is coming in so fast that it appears to have an incoming hyperbolic trajectory -- a first, and one which seems to be a huge problem for the hydroplate theory.  But Dr. Brown points out that Comet ISON's path is incredibly similar to the path of the Great Comet of 1680, as he discusses in an inset halfway down this page of his comet chapter, under Figure 167 (showing a contemporary painting by a Dutch artist of the comet's appearance).

Dr. Brown notes that some analysts soon after Comet ISON was first discovered were so struck by the similarity in trajectories between Comet ISON and the Great Comet of 1680 that they thought the two must have been the same comet in the distant past, and split apart.  Obviously this suggestion would not be possible if Comet ISON has never been in the inner solar system before and if it is really coming in on an inbound hyperbolic trajectory.

But why would those astronomers have suggested that Comet ISON was a split-apart piece from the Great Comet of 1680, instead of the return of the Great Comet of 1680 itself?  Because, based on their theories of the mass of the solar system, they believe that the Great Comet of 1680 will travel 880 AU from the sun and take 10,000 years to return.  However, Dr. Brown believes that they have underestimated the true mass of the solar system, and that additional mass lying outside the planetary region of our solar system will pull it back much sooner than conventional theorists believe -- that in fact Comet ISON is the return of the Great Comet of 1680!

There is good evidence to suggest that Dr. Brown is correct.  First, as the Pioneer spacecraft entered the region where Dr. Brown believes there is unexpected mass orbiting the sun at a great distance, they slowed down, to the surprise of scientists.  This phenomenon has since been dubbed "the Pioneer effect" or the "Pioneer anomaly."

Second, as Dr. Brown shows in Table 15 on this page of his comet chapter, there are perhaps two dozen other comets with remarkably similar orbit, which conventional scientists believe are different comets, but which Dr. Brown argues are the same comet returning earlier than conventional models would predict.  He calls these comets "strange pairs" and argues that they are not "pairs" at all.

Third, other comets have returned ahead of schedule.  Comet 153P Ikeya-Zhang, with an aphelion near 101 AU and the longest known orbital period of the "periodic comets," returned ahead of schedule, as did Comet 35P Herschel-Rigollet, as Dr. Brown discusses in the upper half of the same page in his comet chapter.

In addition to all the above, the possibility that Comet ISON is the return of the Great Comet of 1680 would then be yet another piece of evidence that -- far from posing a problem for the hydroplate theory -- adds strong additional supporting data which argues that Dr. Brown and his theory is correct!

As Dr. Brown points out, like the Great Comet of 1680, Comet ISON is going to make an extremely close approach to the sun -- to a distance of only 0.012 AU.  It is extremely unlikely for two different objects to come from so far away, from an almost identical direction, and pass so close to the sun.  It's as if, he says, it is "almost like barely missing a bull's eye from a distant star's solar system light years away."

You can see the trajectory for yourself in this excellent "orbit diagram" tool from NASA's Jet Propulsion Laboratory, which enables the viewer to zoom in and zoom out, and to spin the solar system around on different axes in order to view the comet's path from the side, from "overhead," and from any other direction in space imaginable.  With it, you can get a real perspective at how difficult it is to accept that two different bodies coming from that far away could just randomly follow that path and get that close to the sun without hitting it (see two screen shots below as an example, although zooming in and out yourself is far more effective at conveying the enormous scale of the comet's orbit).

So, as you go out to look for Comet ISON in the early pre-dawn hours, you may actually be looking at the unanticipated return of the Great Comet of 1680!  And, at the same time, you may be looking at one of the most dramatic confirmations of Dr. Walt Brown's hydroplate theory.