Comet ISON is still aiming for a spectacular showing this November as the comet continues to brighten rapidly. The celestial visitor is now between the orbits of Mars and Jupiter and may become one of the brightest natural objects seen in the nighttime sky.
Comet ISON is about 3.1 miles in diameter and traveling at a speed of 48,000 MPH. The comet is being watched by an increasing number of instruments as it brightens. Large, professional telescopes on Earth are tracking the object as well as space telescopes and major observatories.
By September, the comet should brighten enough to be spotted with most backyard telescopes and large binoculars. Eventually, the comet will be visible to the naked eye in November.
After that, it will continue to brighten as it rounds the sun on November 28, although it may not survive this approach, passing just 1.1 million miles from the surface of the Sun. At that close proximity, scientists think the comet could break into pieces.
Assuming ISON survives, it will remain visible on its outbound journey, with naked-eye observers enjoying the sight until mid-January. It should be easy to spot in telescopes until March.
On the night of January 14-15, Earth will pass close to ISON’s orbit, and may be dusted with fine particles from the comet. These particles are thought to be too small to spark a meteor shower that will be visible to the naked eye, but the dust could create high-altitude clouds that glow after sunset because of their height above the Earth’s surface. These are known as noctilucent clouds.
Comet ISON is expected to put on a spectacular show, even if it breaks up near the Sun. The current rate of brightening is on track for a -17 magnitude performance, which would make it brighter than the full moon. However, scientists think this pace of brightening may slow as it approaches the Sun, and it’s more realistic the comet will peak around -7 magnitude, which is closer to Venus in brightness. Experts warn that comets can often perform well below expectations, so betting on its performance is more guesswork than science.
Other questions remain about ISON. For example, its orbit appears to be very similar to that of the Great Comet of 1680, which was itself visible in the daytime sky. Astronomers have suggested that ISON may be a fragment of this comet, or rather than both comets share a common parent.
It is hoped that the appearance of Comet ISON will awaken imaginations around the world, and pique interest in astronomy for a new generation.