New Images of Comet ISON Hurtling Towards the Sun

ISON would appear to be in the same ballpark as 19P/Borrelly, which was estimated at 8km × 4km ×4km (according to Wikipedia), with a mass of roughly 2e13 kg" = 2e10 metric tons. Now, the article linked to at the beginning of this thread says "...Comet ISON ... main body was spewing some 850 tons of dust per second at the beginning of the year." I assume those are also metric tons, at any rate, that seems like a lot. It figures as 7.344e7 tons per day, which I'd expect would pick up as the comet gets closer to the sun. Let's call it conservatively 10e7 (or 1e8) tons per day, on average, for all ejecta (dust, gas, etc.) Um, 2e10 metric tons of comet divided by 1e8 metric tons of ejecta per day gives us a comet with a mass of "0" after 200 days.

Granted, if the comet is really "boiling away", before it even gets inside the orbit of Venus, the rate of ejecta might slow back down, but unless I've made a grievous math error somewhere, something in the figures the article states seems a bit suspect...

Yes, I’m still wondering if I’ll see a comet in my lifetime that seems even modestly impressive (as viewed from Earth).

If this one fizzles per my speculation above, well, Bad Co. had a tune that somewhat applies...

Johnny was an school boy
When he heard his first Beatles song
Love Me Do, I think it was
And from there it didn’t take him long
Got himself a guitar
Used to play every night
Now he’s in a rock ‘n’ roll outfit
And everything’s alright
Don’t you know?

Johnny told his Mama,
“Hey, Mama, I’m goin’ away
I’m Gonna hit the big time
Gonna be a big star someday”
Mama came to the door
With a teardrop in her eye
Johnny said, “Don’t cry, Mama,
Just smile and wave goodbye”
Don’t you know?

Yeah......yeah.....

(Chorus)
Don’t you know that you are a shooting star
Don’t you know
Don’t you know
Don’t you know that you are a shooting star
And all the world will love you just as long
As long as you are

Johnny made a record
Went straight up to number one
Suddenly everyone loved
To hear him sing his song
Watchin’ the world go by
Surprisin’ it goes so fast
Johnny looked around him and said,
“Well, I made the big-time at last”
Don’t you know?
Don’t you know?

(Chorus)
A shooting star

Don’t you know that You are a shooting star
Don’t you know?
Don’t you know that You are a shooting star
And all the world will love you just as long
as long as you are

Johnny died one night, died in his bed
Bottle of whiskey, sleeping tablets by his head
Johnny’s life passed him by like a warm summer day
If you listen to the wind you can still hear him play

(chorus)
Don’t you know that you are a shooting star
Don’t you know?
Don’t you know that you are a shooting star
Don’t you don’t you don’t you don’t you don’t you know
Don’t you know that you are a shooting star

Don’t you, don’t you know that you are a shooting star

What is "boiling away" currently is mostly other than water ice (e.g., CO2, Co, etc.) according to the scientists, and what leads them to believe this is the first visit for this comet to the inner solar system because of the amount of activity taking place this far out. They expect activity to slow some, until it is closer to the sun where water ice evaporation will pick up.

More from another article:

NASA's SWIFT satellite typically studies the aftermath of exploding stars in distant galaxies. However, the satellite was used in January and February of 2013 by astronomers from the University of Maryland at College Park and Lowell Observatory to study the dust and water being expelled from the comet. These studies have also led to the first estimate of the size of Comet ISON's nucleus.

The studies determined that Comet ISON is expelling roughly 130 pounds (60 kg) of water and 112,000 pounds (51,000 kg) of dust every minute. These shed materials create Comet ISON's coma, dust tail and dust trail.

Astrophysicists compared the dust amount of dust being blown from the comet to observations of other comets of known size. Using this information, they estimated the size of Comet ISON to be 3 miles (5 km) in diameter.

Of course, Comet ISON isn't a perfect five mile wide sphere.

Although the comet is still too far to determine the exact dimensions of its nucleus, it will be like other comet nuclei - unevenly shaped with valleys and peaks, and pockmarked with tiny craters. The image to the left shows the size of dimension of comet nuclei snapped during close fly-bys by the spacecrafts. Giotto, EPOXI, Stardust and Deep Space 1 have all increased on understanding of the dimensions and size of comets.

A U.S. probe named Deep Impact went one step further. It successfully hit Comet Tempel-1 in order to discover the chemical composition beneath the icy surface. For once we created a crater, albeit a small one at 492 feet (150 m), on a comet rather than the other way around.

Comet ISON is expected to lose 10% of its size / mass during this, its first-ever, orbit through the inner solar system.

Planetary Science Institute research scientist Jian-Yang Li led a team of scientists that used The Hubble Space Telescope's Wide Field Camera 3 on April 10, 2013 to determine the size of Comet ISON's coma. On April 10, 2013 Comet ISON was around 386,000,000 miles (621,000,000 km) from the Sun. This put it inside the orbit of Jupiter. Li and his team determined the coma was roughly 3,100 miles (5,000 km) in diameter. This made it almost as wide as the distance between Los Angeles and Augusta, Maine.

Li and his team observed a jet spewing dust from the Sun-facing side of the comet. The dust tail was already 2,300 miles (3,700 km) long. If Comet ISON continues to perform, as expected, it will be one of the brightest comets in history.

The Dimensions and Diameter of Comet ISON (C/2012 S1)

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