Comet ISON has entered the inner solar system!
On about October 1st, the comet that has attracted so much attention and prompted many projections, prognostications and probably a few wagers, crossed the orbit of the planet Mars to begin its final sprint to the center of the solar system. It's the last and fastest dog-leg of its long journey from the cold dark reaches of outer space to its potentially fateful close encounter with the Sun.
Discovered in September 2012 by Vitali Nevski and Artyom Novichonok with a telescope of the International Sky Observer Network, Comet ISON has since been tracked by telescopes around the world—including the one that actually goes around the world: the Hubble Space Telescope. It has even been scoped out by cameras on NASA's Mars Reconnaissance Orbiter when it sailed close to Mars a couple of weeks ago.
All of this scrutiny is aimed at learning as much about the physical nature of this ancient time capsule as possible before it reaches a crucial point in its flight through the solar system: perihelion, the point where it passes closest to the sun, on November 28. Crucial, because at that time it will be less than a single solar diameter from the Sun's surface, and exposed to intense radiation that could vaporize it and gravitational tidal forces that will work to tear it apart.
What have all of these observations told us about the betting odds of the comet's survival, or whether we'll be able to see with our eyes?