Today, Comet ISON is approximately 2.526 AU from the sun. That’s over 234+ million mi (377+ million km). There are less than 110 days until ISON reaches perihelion.
Over the past 5 days, between August 5th and August 10th, Comet ISON traveled a distance of approximately 0.076 AU.
That’s an average speed of roughly 1.41 million miles per day, or 2.27 million kilometers per day.
On July 29th, the time projected (tp) value calculated by NASA for perihelion (closest to the sun) was 2013-Nov-28.77833189. That’s the equivalent of November 28, 2013 at 18:40:47 UTC.
The time projected value was updated on August 9th at 14:43:37 to 2013-Nov-28.77844308. That’s the equivalent of November 28, 2013 at 18:40:57. That’s a small update of about 10 seconds.
ISON is currently between the orbits of Mars and Jupiter, but from Earth’s perspective, it appears behind the Sun’s glare. ISON entered the Sun’s glare back in June and should become observable by NASA’s equipment in mid-August or early September at the latest. It’s projected that it will become visible to the naked eye by early to mid-November.
Here are some news snippets from the past week.
“We don’t have anything to directly compare to ISON,” astronomer Matthew Knight of the Lowell Observatory in Flagstaff, Ariz., said Thursday here at the Johns Hopkins University Applied Physics Laboratory during a two-day workshop on observing ISON. Based on historical records, he said, very large comets tend to survive their encounters with the sun, while smaller ones evaporate or break into pieces under the harsh solar radiation. Comet ISON is a mid-sized comet, and its fate is very uncertain.
Like Kohoutek, comet ISON is a first-time Oort cloud visitor. What’s more, ISON will pass much closer to the sun that Kohoutek did and so astronomers may be able to see its layers chemically come apart like peeing open an onion. Unlike in 1974, today we have a powerful and diverse collection of space and ground based telescopes to following the far visitor, and the Internet to share information at the speed of light.
A comet like this only comes along once or twice a century say experts. “Sungrazing comets are common. Fresh-from-the-Oort-cloud comets are common. Comets detected more than six times farther out than the Earth’s orbit? Not so much. The combination of all three is very rare,” said comet veteran Mike A’Hearn of the University of Maryland.
Comet ISON…has been teasing professional and amateur astronomers alike in the past two months, when it has been invisible in the glare of the Sun. This is a purely geometrical effect: ISON is still 2.5 times farther from the Sun than the Earth, but is on the other side of the Sun.
Some time in August, eager amateur observers should be able to pick the comet out of bright dawn skies, as its angular distance from the Sun grows throughout this month from 12 to 30 degrees…ISON will still be an exceedingly faint object, in reach of only die-hard astrophotographers.