Here are the back-of-the-envelope numbers for July 8, 2013.
Today, Comet ISON is approximately 3.008 AU from the sun. There are 143 days until Comet ISON reaches perihelion.
Between June 27th and July 8th, Comet ISON traveled a distance of approximately 0.152 AU.
0.152 AU = 14,129,282.7 mi 0.152 AU = 22,738,876.3 km
That’s an average speed of roughly 1.28 million miles per day, or 2.06 million kilometers per day.
Here is a news snippet from the past week.
“Superficially resembling a skyrocket, comet ISON is hurtling toward the sun presently at a whopping 48,000 mph.
Its swift motion is captured in this time-lapse movie made from a sequence of pictures taken May 8, 2013, by NASA’s Hubble Space Telescope. At the time the images were taken, the comet was 403 million miles from Earth, between the orbits of Mars and Jupiter.
The movie shows a sequence of Hubble observations taken over a 43-minute span and compresses this into just five seconds. The comet travels 34,000 miles in this brief video, or 7 percent of the distance between Earth and the moon. The deep-space visitor streaks silently against the background stars.”
– NASA.gov, July 3, 2013