موقع د. محمود صبيح

Comet Ison likely didn't survive sun encounter

CBC News Posted: Nov 28, 2013 9:15 AM ET Last Updated: Nov 28, 2013 5:17 PM ET


Comet Ison didn't make it


https://www.youtube.com/watch?v=UmlQ2J0VVzo





Comet Ison likely didn't survive its graze past the sun early this afternoon, astronomers say.

"It's not looking good for Ison in my opinion," said Phil Plait, an astronomer who writes for Slate's Bad Astronomy blog, during a Google Hangout organized by NASA Thursday.

"That's kind of my assessment too," agreed Karl Battams, an astrophysicist at the Naval Research Laboratory in Washington, D.C., who runs the NASA-funded Sungrazing Comets Project.

Images from NASA's SOHO spacecraft at 1:12 p.m. ET showed long tails that appeared as though they could be fading toward the sun, and the head of the comet was no longer visible.

By 2 p.m. ET, images from the Solar Dynamics Observatory spacecraft did not show the comet at all, to the surprise of Dean Pasnell, project scientist for SDO, who said the rocky material from the comet wouldn't be expected to evaporate that quickly.
SOHO-imate-1912UTC

An image of Comet ISON at 19:12 UTC (2:12 p.m. ET) captured by NASA's SOHO spacecraft shows only a fading tail near the sun, suggesting that the comet did not survive its closest approach to the sun at 1:37 p.m. ET. (SOHO/NASA)

"I'd like to know what happened to our half mile of material that was going around the sun."

Unfortunately, Pasnell said, the fact that the comet can't be seen even with SDO suggests that it is unlikely the remains of the comet will be visible from Earth.

Comet Ison is unique because it is the first sun-grazing comet ever observed from the Oort Cloud, a vast region of comets and debris near the edge of the solar system, far beyond the outermost planets. It is also one of the largest sun-grazing comets ever observed.

Comet ISON Fizzles as it Rounds the Sun
Nov. 28, 2013

https://www.youtube.com/watch?v=6j6nkLn ... r_embedded



These images from NASA's Solar Terrestrial Relations Observatory and the ESA/NASA Solar and Heliospheric Observatory show Comet ISON growing dim as it made the journey around the sun. The comet is believed to have broken up and evaporated.
Image Credit:
NASA/SDO/ESA/SOHO/GSFC
› Download video

Comet ISON went around the sun on Nov. 28, 2013. Several solar observatories watched the comet throughout this closest approach to the sun, known as perihelion. While the fate of the comet is not yet established, it is likely that it did not survive the trip. The comet grew faint while within both the view of NASA's Solar Terrestrial Relations Observatory, and the joint European Space Agency and NASA's Solar and Heliospheric Observatory. The comet was not visible at all in NASA's Solar Dynamics Observatory.



A white plus sign shows where the Comet should have appeared to SDO.
This image from NASA's Solar Dynamics Observatory shows the sun, but no Comet ISON was seen. A white plus sign shows where the Comet should have appeared. It is likely that the comet did not survive the trip.
Image Credit:
NASA/SDO

"We didn't see Comet ISON in SDO," said Dean Pesnell, project scientist for SDO.

"So we think it must have broken up and evaporated before it reached perihelion."

While this means that Comet ISON will not be visible in the night sky in December, the wealth of observations gathered of the comet over the last year will provide great research opportunities for some time. One important question will simply be to figure out why it is no longer visible.

Comet ISON May Have Survived
Nov. 29, 2013

This movie shows Comet ISON orbiting around the sun – represented by the white circle -- on Nov. 28, 2013. ISON looks smaller as it streams away, but scientists believe its nucleus may still be intact. The video covers Nov. 27, 2013, 3:30 p.m. EST to Nov. 29, 2013, 8:30 a.m. EST.
Image Credit:




ESA/NASA/SOHO/Jhelioviewer


Three view of what's left of Comet ISON rounding the sun.
ISON appears as a white smear heading up and away from the sun. ISON was not visible during its closest approach to the sun, so many scientists thought it had disintegrated, but images like this one from the ESA/NASA Solar and Heliospheric Observatory suggest that a small nucleus may be intact.
Image Credit:
ESA/NASA/SOHO/GSFC



Continuing a history of surprising behavior, material from Comet ISON appeared on the other side of the sun on the evening on Nov. 28, 2013, despite not having been seen in observations during its closest approach to the sun.

As ISON appeared to dim and fizzle in several observatories and later could not be seen at all by NASA's Solar Dynamics Observatory or by ground based solar observatories, many scientists believed it had disintegrated completely. However, a streak of bright material streaming away from the sun appeared in the European Space Agency and NASA's Solar and Heliospheric Observatory later in the evening. The question remains whether it is merely debris from the comet, or if some portion of the comet's nucleus survived, but late-night analysis from scientists with NASA's Comet ISON Observing Campaign suggest that there is at least a small nucleus intact.

A bright ISON goes into the sun, a dim ISON comes out.
Another view from SOHO's C2 chronograph shows Comet ISON appearing bright as it streams toward the sun (right). it can be seen as a dim streak heading upward and out in the left image. The comet may still be intact.
Image Credit:



ESA/NASA/SOHO/Jhelioviewer

Throughout the year that researchers have watched Comet ISON – and especially during its final approach to the sun – the comet brightened and dimmed in unexpected ways. Such brightness changes usually occur in response to material boiling off the comet, and different material will do so at different temperatures thus providing clues as to what the comet is made of. Analyzing this pattern will help scientists understand the composition of ISON, which contains material assembled during the very formation of the solar system some 4.5 billion years ago.

http://www.youtube.com/watch?feature=player_embedded&v=qdnAfrMFQkc




Comet ISON May Have Survived

Continuing a history of surprising behavior, material from Comet ISON appeared on the other side of the sun on the evening on Nov. 28, 2013, despite not having been seen in observations during its closest approach to the sun. This movie shows Comet ISON orbiting around the sun -- represented by the white circle -- and covers Nov. 27, 2013, 3:30 p.m. EST, to Nov. 29, 2013, 8:30 a.m. EST. ISON looks smaller as it streams away, but scientists believe its nucleus may still be intact. Read more: http://www.nasa.gov/content/goddard/com ... -survived/ NASA's Comet ISON website: http://www.nasa.gov/ison Video Credit: ESA/NASA/SOHO/Jhelioviewer

Comet ISON Has Changed Course!

Despite early reports which declared Comet ISON dead, following its close encounter with the sun, astronomers have now observed evidence that the much-discussed comet survived the event, albeit missing a considerable amount of its original mass. (Click Images For L

Richard C. Hoagland, provided images that suggest Comet ISON not only survived the solar rendezvous, but also changed course due to some mysterious force. Richard writes ...

Here is our Enterprise Mission evidence that ISON not only "survived" its close approach to the Sun on Thursday afternoon ... it's also now "changed course!"

These diagrams illustrate ISON's position early this AM, at 06:30 UTC, overlaid on an official NASA plot of ISON's pre-perihelion projected orbit.

They're obviously NOT the same ....

"Something" dramatic happened around perihelion ... to not only fundamentally change the geometric shape of ISON's "coma" it's now definitely "triangular" ... tetrahedral? But its trajectory as well;

ISON is now following a significantly different, slower solar orbit away from the Sun than NASA calculated previously, as can easily be seen in these Enterprise Mission orbit plots of the official NASA data.

So far, NASA has made NO "official comment."