Comet ISON update for September 20, 2013

Tonight, Comet ISON is approximately 1.853 AU from the sun. That’s over 172+ million mi (277+ million km). There are less than 69 days until ISON reaches perihelion.

In the past month, between August 20th, and September 20th, Comet ISON traveled a distance of approximately 0.518 AU.

0.518 AU = 48,151,108.2 miles
0.518 AU = 77,491,697 kilometers

That’s an average speed of roughly 1.55 million miles per day, or 2.49 million kilometers per day over the course of 1 month.

Over the past 10 days, between September 10th and September 20th, Comet ISON traveled a distance of approximately 0.174 AU.

0.174 AU = 16,174,310.5 miles
0.174 AU = 26,030,029.5 kilometers

That’s an average speed of roughly 1.61 million miles per day, or 2.60 million kilometers per day.

Estimated average speed using available numbers from
the past 10 days
1,617,431.05 miles / 24 hours = 67,392.9 miles per hour 
(This matches the recent 67,000 mph estimate seen 
in online media.)
67,392.9 mph / 60 min = 1,123.2 miles per minute
1,123.2 mi/min / 60 sec = 18.7 miles per second

2,603,002.95 km / 24 hours = 108458.4 kilometers per hour
108,458.4 km/hr / 60 min = 1807.6 kilometers per minute
1807.6 km/min / 60 sec = 30.1 kilometers per second

On September 16th, the time projected (tp) value calculated by NASA for perihelion (closest to the sun) was 2013-Nov-28.77877111. That’s the equivalent of November 28, 2013 at 18:41:25 UTC.

ISON on 20 September, 2013

Comet ISON diagram

ISON is currently approaching the orbit of Mars as it makes its way toward the sun. Comet ISON will make a close approach to Mars on October 1st, but will not hit Mars, or any other planet during its journey. According to close-approach data from NASA, it will come within 0.429 AU of mars. That’s over 39,878,041.3 miles (or 64,177,486.5 km). That’s the equivalent of being over 166 times the distance from Earth to the moon.

Here’s a diagram of where ISON will be on October 1, 2013. Again, ISON will not hit Mars nor any other planet during its journey toward the sun.

Comet ISON approaches Mars

Comet ISON and Mars diagram

Where can I find ISON if I have a large telescope?

Astronomers from across the globe have been using powerful telescopes to capture and image ISON.

ISON is still not visible to the naked eye, but the images of ISON are usually taken during the early morning hours. Ephemeris are used to find the exact location of ISON. Sky & Telescope magazine has a good article on understanding celestial coordinates. ISON is currently in the constellation Cancer.

The images below will give you a general idea of where Comet ISON is in the late night/early morning sky during this week and where amateur and professional astronomers have been aiming their telescopes. The location is set for Dallas, TX, between the hours of 04:00 AM CT and 0700 AM CT. Comet ISON’s general vicinity is within the red marks.

Comet ISON around 04:00 AM CT on September 21, 2013

Comet ISON around 04:00 AM CT on September 21, 2013

Comet ISON around 07:00 AM CT on September 21, 2013

Comet ISON around 07:00 AM CT on September 21, 2013

Updated 09/21/2013: Here’s are a couple of photo links from Flickr user hirocun from Japan. In the following links you will get a realization of how tiny Comet ISON is in relation to everything else. Comet ISON will not be visible to the naked eye until early to mid-November while others say at late as early December. (The inset shows where Comet ISON is at, you can’t see it though. The very bright object that is in the photo is the planet Mars, and above the two is the Beehive Cluster) (Zoomed in, you still can’t see ISON, just its general location that is marked by the inset.) (You’ll need to tilt the photo 90 degrees. Again, that bright object is Mars, the inset shows where ISON is at and it’s a very tiny smudge on the bottom-left corner within the center of the overall photo. The zoomed-in inset finally shows Comet ISON.)

Here are some news snippets from the past week.

The original press release announcing the comet had fizzled has since been taken offline, and Karl Battams, an astrophysicist and computational scientist at the US Naval Research Laboratory, says the latest news about Comet ISON is all good news.

“So the actual latest is that Comet ISON continues to gradually brighten up, and is behaving almost exactly as we expect a dynamically new comet to behave. It’s still in one piece, and is beginning to show an extended coma and increasingly lengthening tail. Bottom line is that it is progressing very nicely!”

Red Orbit, 09/19/2013 article by Lee Rannals

Comet ISON will miss Earth by many millions of miles during its swing through the inner solar system — and so will its bits and pieces, if the comet happens to break apart along the way.

“During a breakup, comet fragments don’t fly off in different directions like shards in a cinematic explosion,” explains a new Comet ISON video released by the operators of NASA’s famous Hubble Space Telescope. “They break off but continue to travel along the path of their parent body. So any pieces would remain far from us, millions of kilometers away.”

NBC News, 09/20/2013 article by Mike Wall

The first close-up of ISON will come on 1 October, when it flies within 10 million kilometres of the Red Planet. “Mars has the best seat in the solar system,” says Carey Lisse of the Johns Hopkins University Applied Physics Laboratory. The HiRISE telescope on NASA’s Mars Reconnaissance Orbiter will snap sharp pictures on a par with Hubble’s images. The European Space Agency’s Mars Express will also watch, alongside NASA’s Curiosity and Opportunity rovers.

Around the same time, the first balloon mission to study a new-found comet will gaze up from Earth. The Balloon Rapid Response for ISON mission will launch from New Mexico in late September to measure water vapour and carbon dioxide emitted from the comet. “No other spacecraft can make these measurements,” says Andy Cheng, also at the Johns Hopkins University Applied Physics Lab., 09/20/2013 article by Jeff Hect

Image credits: NASA, Stellarium

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