WILL A PIECE OF COMET ISON STRIKE EARTH IN DECEMBER 2013?

This article is about Comet Ison (aka: C2012 S1), named by the Russian discoverers after the International Scientific Optical Network telescope they used. It will pass by Earth next December 2013, and it could be brighter than the moon, which means we might even be able to see it during the day. 

Concern 1: On the inbound trajectory of Ison, it will pass extremely close to Mars around the first of October (ref picture below). What concerns would we have on Earth about a direct hit on that planet or one of its moons?

Ison_Mars_2Oct2013.jpg

Concern 2: If a comet passes too close to a planet or sun, the gravitational forces can tear it apart - this is called the Roche Limit. The Roche Limit for comets moving around the sun is 1.49 million miles, and Comet Ison will pass within 1.16 million miles - inside the Roche Limit. 

It might not break up and we have no concerns. But if it breaks up and spreads out, several things can happen. It can lose speed and be pulled into the sun, or some of the pieces may be pulled into the sun while others escape. Escaping objects will probably be slowed due to the sun’s pull and their outbound speed and trajectories will change, increasing the chance of them crossing the Earth's orbit. Remote - probably. But a chance we should be studying.  

Here's why. The real problem comes after Ison goes behind the sun and begins its return trip. When would the comet and/or pieces of comet hit the Earth? And where? Can JPL/NASA give us possible scenarios for comet breakup and potential impact? I think so - not precise, but useful for planning purposes. Then leaders can look at options for possible large-scale evacuations, and staging and storage of food and water. If we are in danger of getting hit by pieces of Ison, we should be planning for it now. 

This picture shows Ison on December 27, 2013 moving up and past Venus and Earth, if nothing happens to the comet to change the current trajectory. 

Ison_Earth_27Dec2013Arrow.jpg

JPL Orbit Tool
http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=ISON;orb=1;cov=0;log=0;cad=0#elem  

 

BELOW - - Biblical Commentary, Article about comet, and paper on Roche Limit

 

BIBLICAL COMMENTARY

Read what I wrote in Gathering Over Jerusalem 10 years ago, as I commented on events described in the book of Revelation..

"The first trumpet, Rev 8:7, announces hail and fire mixed with blood and a third of the earth burns up.  The hail and fire sound like meteors hitting the earth.  This could be a precursor of an inbound asteroid or the effect of our attempt to destroy the asteroid, causing smaller pieces to precede the larger object.  

"The second trumpet, Rev 8:8, announces a blazing mountain falling into the sea. The second bowl plague, Rev 16:3, is the sea turns to blood and dies.

This sounds like an asteroid or comet hitting the ocean somewhere with the result that some of it turns blood red and dies - a cause and effect relationship.  I don’t know why the sea turns red, unless it has something to do with the composition of the asteroid or the effect of bacteria on the dead marine life. 

"From the third bowl plague, Rev 16:4, a third of the rivers and springs turn to blood - another cause and effect relationship.  It seems that the second and third plague have similar effects.  The asteroid of the second plague causes the sea to turn red, and the third plague is the rivers and springs turning red.  Would the resultant asteroid impact dust also contaminate the rivers and springs?"  

LOOKING FORWARD

First: I am not prophesying that Earth will get hit by pieces of Ison.

Second: The comet passes Earth in December 2013 and will probably not strike unless something causes it to fall apart earlier and/or deviate from its current trajectory.

Order Gathering Over Jerusalem from Amazon.com 

Comet C/2012 S1 To Come Close To Earth In 2013, Bringing Spectacular Sky Show

http://www.huffingtonpost.com/2012/10/07/comet-c2012-s1-earth_n_1945462.html

By Michael Moyer

As it flares out of the distant Oort Cloud, the newly discovered comet C/2012 S1 (ISON) appears to be heading on a trajectory that could make for one of the most spectacular night-sky events in living memory. Why is this comet expected to be so unique?

Two reasons:

Astronomers predict that the comet will pass just 1.16 million miles from the Sun as it swings around its perihelion, or closest approach. (This may seem like a lot, but remember—the Sun is big. If we were to scale the Sun down to the size of Earth, the comet would pass well within the orbits of dozens of satellites.) The close approach will melt enormous amounts of the comet’s ice, releasing dust and gas and forming what should be a magnificent tail.

After it loops around the Sun and forms this tail, the comet should then pass relatively close to Earth—not near enough to cause any worry, but close enough to put on a great show. Viewers in the Northern Hemisphere will get the best view as the comet blooms in the weeks approaching Christmas 2013. The comet could grow as bright as the full moon.

Of course, comets have a habit of not living up to expectations. This one could be sucked into the Sun during its close approach, or not grow as much of a tail as astronomers hope.

But that hasn’t dampened enthusiasm for what Astronomy Now is awkwardly calling “a once-in-a-civilisation’s-lifetime” event. The comet expert John E. Bortle is alreadycomparing ISON with the Great Comet of 1680, which, according to contemporary accounts, caused the people of New York’s Manhattan Island to be “overcome with terror at a sight in the heavens such as has seldom greeted human eyes…. In the province of New York a day of fasting and humiliation was appointed, in order that the wrath of God might be assuaged.”

We can only hope for such a show.

Roche Limit: Why Do Comets Break Up? By Mike Luciuk 

http://www.asterism.org/tutorials/tut25-1.htm 

When comets pass close to a massive body like the Sun or Jupiter, they may break up due, at least in part, to the tidal forces encountered. Recall that tidal forces occur from differential gravity forces created on an object because of the difference in distance on either side of say, a comet from a planet or Sun. Several examples come to mind. In 1846, Biele’s comet split in two while passing close to the Sun. Comet XIV passed within 10 million miles of the Sun in 1947 and also split in two. In 1976 Comet West broke into four pieces near the Sun. More recently, Shoemaker-Levy 9 disintegrated into a 20+ fragments after passing too close to Jupiter, and returned the insult by spectacularly plunging into its aggressor. In 1850, the French astronomer E. A. Roche (1820 – 1883) stated “no satellite can exist closer to a planet than 2.44x its radius or 1.44x from its surface.” The equation he developed for this distance, the Roche limit, is  

RocheLimit.jpg

 

 

 

 

where LR is the Roche limit, from the planet’s centerm, RP is the planet’s radius, Pp is the planet’s density, Ps is the satellite’s density.

If a satellite or comet that is held together solely by its gravitational force (no tensile strength) passes within the planet’s Roche limit, it will break apart. A non-rotating liquid satellite without surface tension is an example. Note also that the limit depends on the relative densities of the two objects as well as the planet’s size. The Roche limit for Earth is approximately 20,000 km above the surface. The reason why artificial satellites within this limit don’t break apart is because they have significant tensile strength that overcomes Earth’s tidal force on the vehicles. 

Deriving the Roche limit formula by equating the planet’s tidal force to the satellite’s self-gravitational attractive force gives a result slightly different from the standard formula shown above. Instead of the 2.44 constant, we get a 2.52 value. The standard formula takes into account the oblate spheroid deformation a satellite undergoes as it experiences the tidal forces. 

We’ll examine the Roche limits for the Earth (radius 6,380 km, density 5.52), Jupiter (radius 71,500 km, density 1.33), Saturn (radius 60,300 km, density 0.69), and the Sun (radius 696,000 km, density 1.41). Comets are considered to be aggregations of ice and dust. Their significant porosity can result in nucleus densities of approximately 0.5. This structure makes them especially vulnerable to tidal forces. The density of asteroids varies widely, so we’ll assume an average density of 3.00. Most asteroids are structurally intact, giving them breakup resistance to tidal forces. Earth’s Roche limit for comets is 34,700 km or 5.43 radii and for asteroids, 19,000 km or 2.98 radii. Jupiter’s limit for comets is 242,000 km or 3.38 radii and for asteroids is 133,000 km or 1.86 radii. Saturn’s limit for comets is 164.000 km or 2.72 radii and for asteroids is 90.200 km or 1.50 radii. The Sun’s limit for comets is 2.4 million km or 3.45 radii and for asteroids is 1.3 million km or 1.90 radii.