Heisenberg
Well-Known Member
http://www.independent.co.uk/news/s...e-ison--the-comet-of-the-century-8431443.html
Comet Ison has taken millions of years to reach us travelling from the so-called Oort cloud a reservoir of trillions and trillions of chunks of rock and ice, leftovers from the birth of the planets. It reaches out more than a light-year a quarter of the way to the nearest star. In the Oort cloud the Sun is but a distant point of light whose feeble gravity is just enough to hold onto the cloud. Every once in a while a tiny tug of gravity, perhaps from a nearby star or wandering object, disturbs the cloud sending some of its comets out into interstellar space to be lost forever and a few are scattered sunward. Comet Ison is making its first, and perhaps only visit to us. Its life has been cold, frozen hard and unchanging, but it is moving closer to the Sun, and getting warmer.
By the end of summer it will become visible in small telescopes and binoculars. By October it will pass close to Mars and things will begin to stir. The surface will shift as the ice responds to the thermal shock, cracks will appear in the crust, tiny puffs of gas will rise from it as it is warmed. The comet's tail is forming. By late November it will be visible to the unaided eye just after dark in the same direction as the setting Sun. Its tail could stretch like a searchlight into the sky above the horizon. Then it will swing rapidly around the Sun, passing within two million miles of it, far closer than any planet ever does, to emerge visible in the evening sky heading northward towards the pole star. It could be an "unaided eye" object for months.
Remarkably Ison might not be the only spectacular comet visible next year. Another comet, called 2014 L4 (PanSTARRS), was discovered last year and in March and April it could also be a magnificent object in the evening sky. 2013 could be the year of the great comets.
Comet Ison has taken millions of years to reach us travelling from the so-called Oort cloud a reservoir of trillions and trillions of chunks of rock and ice, leftovers from the birth of the planets. It reaches out more than a light-year a quarter of the way to the nearest star. In the Oort cloud the Sun is but a distant point of light whose feeble gravity is just enough to hold onto the cloud. Every once in a while a tiny tug of gravity, perhaps from a nearby star or wandering object, disturbs the cloud sending some of its comets out into interstellar space to be lost forever and a few are scattered sunward. Comet Ison is making its first, and perhaps only visit to us. Its life has been cold, frozen hard and unchanging, but it is moving closer to the Sun, and getting warmer.
By the end of summer it will become visible in small telescopes and binoculars. By October it will pass close to Mars and things will begin to stir. The surface will shift as the ice responds to the thermal shock, cracks will appear in the crust, tiny puffs of gas will rise from it as it is warmed. The comet's tail is forming. By late November it will be visible to the unaided eye just after dark in the same direction as the setting Sun. Its tail could stretch like a searchlight into the sky above the horizon. Then it will swing rapidly around the Sun, passing within two million miles of it, far closer than any planet ever does, to emerge visible in the evening sky heading northward towards the pole star. It could be an "unaided eye" object for months.
Remarkably Ison might not be the only spectacular comet visible next year. Another comet, called 2014 L4 (PanSTARRS), was discovered last year and in March and April it could also be a magnificent object in the evening sky. 2013 could be the year of the great comets.
