The universe is putting on its own Thanksgiving Day light show in the form of Comet ISON, which is set to graze the sun tomorrow.
Assuming that the comet does not disintegrate under the pressure of strong gravitational forces or solar energy, it is set to be one of the most brilliant comets of this century.
The shining heavenly body will pass within 730,000 miles (1.2 million kilometers) of the sun, which is a very close shave by cosmic standards. This fact does concern astronomers, many of whom predict that the comet may not survive its brush with the fiery star.
As it traveled around the sun in 2007, Comet Encke was also battered by a coronal mass ejection (CME) that emanated from a wild solar storm. The CME tore away the comet’s tail, though this was seen to reappear as it continued to release dust and gases.
Astronomers believe that a similar fate awaits ISON as solar activity is far higher now than in 2007, and the latest comet will be 30 times closer to the sun than its predecessor Encke.
Angelos Vourlidas of the Naval Research Laboratory, and member of NASA’s Comet ISON Observing Campaign (CIOC), talked about the differences between the two events:
“… the year 2007 was near solar minimum. Solar activity was low. Now, however, we are near the peak of the solar cycle and eruptions are more frequent.”
Comet ISON will pass through a known cluster of sunspots near the sun’s equator, in an area that is known to have a high probability of CME activity. Coronal mass ejections are huge blasts – sometimes millions of miles wide- of magnetized plasma clouds emitted by sunspots. Scientists believe that they are caused by ‘magnetic reconnection’ which occurs when two opposing magnetic fields collide, creating a massive explosion which shoots debris and electromagnetic radiation into space.
Despite its explosive nature, the volatile phenomenon is unlikely to cause any damage to Comet ISON itself, as CME gases lack any real substance, but comet tails, as illustrated by Comet Encke, can be vulnerable to this type of impact and may well break off.
Vourlidas explained how the damage occurred to Encke:
“The CME that ran over Comet Encke back in 2007 was slow, barely creating a pressure pulse by compressing the solar wind ahead of it… It was this compression which caused the Encke’s tail to fly off.”
ISON is likely to be affected by even stronger solar forces than Encke but astronomers are still unable to predict what the outcome will be. Comet Encke orbits every three years and also had a perihelion, or close passage to the sun on November 21, 2013. It is one of the brightest comets of this year and should be visible with binoculars in the December morning sky, though it pales in comparison to ISON which, it is hoped, will be far more brilliant and visible to the naked eye in December.
Assuming ISON survives its perilous perihelion, which occurs November 28th at 1:38 p.m. EST (1838 GMT), it should develop into a truly heavenly spectacle, though this will be dependent on where in the world you are viewing it from. In rural areas it could definitely be a celestial sensation, but for urban viewers, the sight of ISON may be affected by light pollution leaving city dwellers with a disappointing view of its radiant beauty.
Even if the comet does sustain some damage and break up, this could actually improve visibility, as the resulting dust cloud could cause ISON to become many times brighter and unfurl a tremendously bright tail.
On its return journey, it may be dimly visible in daylight, when it will be found 2 degrees to the right of the rising sun. During the course of the day it will appear to move nearer to the sun, its closest position occurring at around 2 pm EST (1900 GMT), after which it will continue moving clockwise around to the left side.
NB: It is recommended that only experienced astronomers attempt to view ISON as it orbits the sun, as the sun’s infrared rays can cause retina damage to the eye if observers stare directly at its intense light.
Let’s hope that we all have the opportunity to behold this amazing sight in December, when it promises to become one of the most spectacular celestial events of the century.
Unknown Country will keep you updated on the latest ISON developments.