Today, Comet ISON is approximately 2.676 AU from the sun. That’s over 248+ million mi (400+ million km). There are less than 120 days until ISON reaches perihelion.
Over the past 5 days, between July 26th and July 31st, Comet ISON traveled a distance of approximately 0.074 AU.
That’s an average speed of roughly 1.375 million miles per day, or 2.21 million kilometers per day.
On July 20th, the time projected (tp) value calculated by NASA for perihelion (closest to the sun) was 2013-Nov-28.77831993. That’s the equivalent of November 28, 2013 at 18:40:46 UTC.
This was updated on July 29, 2013 at 11:52:19 to 2013-Nov-28.77833189. That’s the same as November 28, 2013 at 18:40:47 UTC, with just a minor update of 1 second.
ISON entered the Sun’s glare back in June and should become observable by NASA’s equipment in late 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.
…Any current determination of ISON’s ultimate fate when it gets close to the Sun later this year is speculation at best, (as is the case with almost any other sun-grazing comet) and since no one on planet Earth has seen ISON since it entered the Sun’s glare in June, there is absolutely no way to determine the comet’s current state, either. The almost unanimous shout from the astronomy internets was “Please! We just have to wait and see what happens with ISON.”
— UniverseToday.com, 07/30/2013 article by Nancy Atkinson
Astronomers suspect that ISON is a “dynamically new” comet, meaning that it’s making its first trip to the inner solar system from the distant Oort Cloud. This could explain the lack of change in ISON’s brightness so far: If the comet had never been exposed to intense light and heat, it may have possessed, until recently, a thin coating of volatile material that vaporizes at a great distance from the sun. After this coating evaporated, the comet stopped brightening, scientists speculate.
But changes could be coming soon for ISON. Even as the comet remains hidden by the glare of the sun, it is streaking toward the “frost line” — the distance from the sun at which an object’s water begins boiling off into space.
Space.com, 07/31/2013 article by Joe Rao
Comet ISON continues to hurtle toward the Sun, and the theorizing about whether it will or won’t be the comet we all regale our bored grandkids about years from now continues to run rampant.
— NASA 07/30/2013, article by Tracy Vogel