A Comet is Coming: When and Where to See it in San Miguel
By Phyllis Burton Pitluga
Gliding from deep space through our Solar System toward its first rendezvous with the sun, a three-mile (five kilometer) wide “dirty snowball” is expected to be a showpiece in our dawn sky this weekend. Submitted 10 days before publication, all of the following is “probably” because I have only seen telescopic views. As Comet ISON nears the sun, it is increasingly vaporizing into an outstretched cloud that reflects the sun’s light.
November 16, 17 and 18
Between 5:30 and 6am in the early morning, the comet should be visible as a long white “fan” when you look up in the southeastern sky (compass azimuth 111º). In the city, high mountains loom in that direction so the best locations are on the ridge along the west side of Río Laja and the presa looking across the valley to the southeast. After 6am the ever-brightening sky will begin to outshine the comet. Sunrise is about 7am depending on the altitude of your view to the east. The comet will be getting ever closer to the sun morning after morning so that sometime next week viewing will become increasingly impossible.
Comet ISON will pass closest to the sun this day (perihelion) just 730,000 miles (1.16 kilometers) above the sun’s surface. How will this ball of ice react? Will the strong gravitational pull of the sun swallow Comet ISON? Or, as it “feels” temperatures of 3600 degrees Fahrenheit (2000 degrees Celsius), will it break apart into smaller comets? The best viewing today will be on TV and the Internet where images taken from various orbiting solar telescopes and an instrument-laden balloon that was recently launched will let us see whether this comet sizzles or fizzles.
If Comet ISON survives its close passage of the sun, it will swing back up into our morning sky as it orbits back out to the far reaches of the Solar System.
All you really need to see a great comet is your eyes alone for it will be big and majestic. Binoculars will let you see more details in the coma (the round cloud of vapor coming of the comet nucleus). A careful look may also show two tails: a bright white tail reflecting the sun’s light off of released dust particles, each grain falling into its own orbit, and a second dimmer greenish-blue tail of ionized gases (so far identified: cyanogen and C2 – diatomic carbon). It is NOT the movement of the comet that determines the direction of comet tails. Both tails follow the comet as it approaches the sun and the tails precede the comet as it recedes because there is a constant flow of charged particles (protons) coming from the sun. This is called the solar wind.
History of Comet ISON
In September of 2012, two Russian amateur astronomers discovered this comet. They were using the International Scientific Optic Network. Thus, the name of the comet became Comet ISON for the initials of the telescope network. When an orbit was calculated, it was discovered that Comet ISON was then beyond the orbit of Jupiter. It is rare to see a comet that far out so expectations began to characterize Comet ISON as the coming brightest comet of the century. We will see.
Why Comets are Important
When our Solar System formed 4.5 billion years ago out of a huge flattening cloud of swirling gas and dust, the sun formed at the center where gravity crammed 99.9 percent of the material of the cloud together to the point of nuclear fusion. The ball began to shine. A star was born, our star the sun. Near to the newborn sun, the lighter gases were swept away leaving rocky inner planets (Mercury, Venus, Earth and Mars, their rocky moons and the asteroid belt). Farther out the new worlds held onto their atmospheres creating the gas giant planets (Jupiter, Saturn, Uranus and Neptune and their rock-ice moons). Even farther out, in the coldest realm, comets collected in a vast cloud 50,000 times farther from the sun than Earth. Out here the primordial gases of the Solar System have remained unchanged in the deep freeze of space. This is why comets are interesting. Every now and then a comet gets gravitationally jostled into a new orbit that sends it on a long journey toward the sun. It is our chance to learn more about our solar system of 4.5 billion years ago.