Comet ISON

[sky otter]

if you listen to the terrible music..it's  take me out to the ball game..
you know the words..i don't care if i ever come back
somebody was havin fun..


Comet ISON's Ghost Seen By Two Spacecraft







Published on Dec 5, 2013

NASA's Cassini probe has captured the highest resolution video yet of Saturn's odd, hexagon shaped jet stream that spins around the gas giants north pole. Read more here: http://goo.gl/xBU9s8

Credit: NASA / JPL

Category Science & Technology

LicenseStandard YouTube License

[zorgon]

getting tired of NASA's "GREATEST THING SINCE SLICED BREAD" announcements only to get burnt toast

[Sgt.Rocknroll]

Ron as I told you earlier this evening about watching the Science channel show in the Planets, they kept advertising tomorrow's show on 'Super Comet Ison'. Can't wait to see what they have to say about that! Lol

[zorgon]

Will try to catch it

But those shows are usually more hype than content

[zorgon]

What's going on with the Comet C/2012 S1 (ISON) images?



Well that was the image I was interested in... so I finally found the official explanation

Comet C/2012 S1 (ISON)
Hubble, 2013 Apr 30
Combined 3-exposure image

Some bloggers have noted that the Comet C/2012 S1 (ISON) Hubble images have some surprising features. Here we briefly explain the origin of the image structures.

Quick summary: The image is the result of combining 3 exposures that produce the 3 components, and the shapes are produced by the combined motion of the Hubble telescope and the comet. The images look exactly as expected.

The image from April 30, 2013 (released on July 16, 2013) using the F606W filter has attracted the most attention. That image (shown above) is the average of 3 separate Hubble exposures. The 3 exposures are available individually for display or download from the web page, as is the combined image. The table below shows the image of the comet in each of the 3 exposures along with information about the exposures.

Comet C/2012 S1 (ISON) Hubble observations on 2013 April 30 using F606W

Exposure 1      
hlsp_ison_hst_wfc3_130430a_f606w_v1   
Start time (UT): 2013-04-30 03:35:43
Exposure: 440 seconds



Exposure 2 
hlsp_ison_hst_wfc3_130430c_f606w_v1   
Start time (UT): 2013-04-30 03:56:15
Exposure: 440 seconds



Exposure 3
hlsp_ison_hst_wfc3_130430e_f606w_v1
Start time (UT): 2013-04-30 04:16:47
Exposure: 440 seconds

You can see that the 3 parts of the structure in the combined image result from the 3 different exposures. The comet itself does not have 3 pieces. They are an artifact that results from adding up the separate exposures.

The comet does not look the same in each exposure because both the comet and the Hubble telescope are moving during the exposure. The comet is blurred, just as a picture taken out the window of a moving car will be blurred. For this image the Hubble telescope was pointing very steadily and accurately at the background stars and galaxies rather than tracking the comet.

In this case, the largest part of the blurring is due to the motion of Hubble itself rather than the motion of the comet. Hubble is orbiting the Earth every 95 minutes. The third exposure ended 46 minutes after the start of the first exposure. During that time the telescope moved from one side of its orbit to the other, a distance of about 8000 miles (~13,000 km). Because the comet is relatively nearby (compared with the distant stars and galaxies), its apparent position among the stars changes due to the different viewing position. This effect is known as parallax. It is expected when observing Solar System targets, and can produce very obvious motion or blurring in images as Hubble whips around the Earth.

There is a nice discussion of the effects of parallax on the Comet ISON images in this YouTube video. It includes detailed modeling of the parallax in these particular images and shows that the observed pattern is exactly what is expected. Another YouTube video shows the effects of combining multiple exposures.

More information about the comet can be found at the Hubblesite ISON blog. There is a specific blog post about making the Hubble color image of Comet ISON.

archive@stsci.edu
2013 August 22

http://archive.stsci.edu/hla/ison/

[sky otter]

just got to wondering about ison and this is what is out there now
good-bye comet...



http://astrobob.areavoices.com/2013/12/21/comet-ison-update-dec-21-hubble-searches-sees-nada/


Comet ISON update Dec. 21 – Hubble searches, sees nada

NASA brought the big gun to bear on our lost comet. On December 18, the Hubble Space Telescope slewed to Comet ISON's expected position and found nothing down to magnitude 25.  That's 100 million times fainter than the faintest star visible with the naked eye.

According to astronomer Hal Weaver, who planned the ISON picture session, that implies that remaining fragments would have to be smaller than about 500 feet (160 meters) in diameter.

Nothing is visible in any of the images in the photo panel above except the trails of stars and galaxies from the time exposures, reflections and the occasional zap of a cosmic ray. After Comet ISON broke apart under the searing heat of the sun and spread into a widening cloud of dust, there was a possibility that its remains would follow a slightly different orbit than the original predicted one. To make sure he was covered, Weaver photographed two possible comet locations, stacking several exposures together to enhance even the faintest objects.

"The images have been combined so that features not at the same place in the various images are suppressed. Any comet fragments would show up more clearly in this composite, though stars still show up as faint streaks", writes Zolt Lavay, author of the ISONblog at the Hubble site.

Again, nothing shows up in these either. There's probably something left of the comet, but the pieces are too small for even Hubble to see. Meanwhile, no observations of ISON from the ground have been made for nearly two weeks. Even the few reports from the beginning of the month, when the comet was presumably brighter, were mostly tentative.

What once compelled us to rise before dawn for a glimpse of one of nature's most fickle yet beautiful creations has dissipated to dust. There's speculation that a portion of its shards may return as an invisible meteor shower in mid-January, but don't count on it. Predicting this comet's near-term future is like guessing what the stock market will do next.
This entry was posted in Comets and tagged Comet ISON, dust, Hubble Space Telescope by astrobob. Bookmark the permalink.
12 thoughts on "Comet ISON update Dec. 21 – Hubble searches, sees nada" ................................................................


http://www.skyandtelescope.com/observing/highlights/193909261.html

Latest Updates on Comet ISON
by Alan MacRobert

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Only a dim "ghost of ISON" survived the comet's November 28th passage around the Sun. The comet's head dwindled away as it raced through the Sun's greatest heat, but a headless streak emerged into spacecraft view out from the other side of the encounter. It's traveling along the comet's originally prescribed track but fading steadily, with no sign of cometary activity. Nothing will be visible by eye from Earth.



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