Here are the back-of-the-envelope numbers for June 27, 2013.
Today, Comet ISON is approximately 3.16 AU from the sun. There are still 154 days until Comet ISON reaches perihelion.
Over the course of the past 10 days, Comet ISON traveled a distance of approximately 0.135 AU.
0.135 AU = 12,549,034 mi 0.135 AU = 20,195,712.5 km
That’s an average speed of roughly 1.25 million miles per day, or 2.02 million kilometers per day.
Between June 26, 2013 and June 27, 2013, ISON traveled a distance of approximately 0.013 AU. This is fairly consistent with the numbers seen 10 days ago.
0.013 AU = 1,208,425.49 mi 0.013 AU = 1,944,772.32 km
That’s an average speed of roughly 50,351 mph or 81,032 km/h. That’s approximately 13.99 mi per sec or 22.51 km per sec.
Here are two news snippets from the past week.
Astronomers had predicted Comet ISON would have started to brighten by now but it has stayed constant. Right now the comet is out of observation range behind the sun in the asteroid belt. When observations begin again in August, astronomer David Schleicher explains they can see if it has brightened as expected.
– Arizona Daily Sun, June 22, 2013
Geoff Chester, a spokesman for the U.S. Naval Observatory in Washington D.C. said: “Predicting a comet’s appearance five months before it arrives is like predicting November’s weather now. There’s a lot of room for error, so it may be wise to acknowledge you don’t really know.”
– The News-Times, June 21, 2013