ISON – The die hard comet

Evidence is growing that a part of the Comet ISON nucleus did in fact survive its close solar experience (see previous posting). Here is a report from NASA:

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 — 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. ET
to Nov. 29, 2013, 8:30 a.m. ET. Image Credit: ESA/NASA/SOHO/Jhelioviewer

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.

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.

Related Links:

For more information on Comet ISON: www.nasa.gov/ison

To download recent ISON imagery: http://svs.gsfc.nasa.gov/Gallery/CometISON.html

4 thoughts on “ISON – The die hard comet”

  1. I wonder if the dimming as the comet approached the sun was due to the dust particles in the coma vaporizing. Gas would scatter much less light than dust, causing the comet to fade. As it passed perihelion and began moving out, the dust being released could survive longer, so the comet could fade back into visibility.

    1. Yes, that sounds like a good possibility. Also, comets are composites of all sorts of ices, dust, rocks, etc. As one layer or chunk of stuff gets burned off, the next layer might behave quite differently.

  2. Nasa shows a much brighter triangular light emerging from behind the sun, but the ‘tail’ does not point away from the sun…. tsup w dat?

    1. Looks like gases (e.g. water vapor), dust, and/or debris (e.g. chunks of dirty ice) separated from the nucleus due to intense heat and solar wind barrage during the close encounter with the sun at perigee. All that stuff is moving along on the same trajectory as the nucleus but the lighter material is getting blown outward from the path due to the solar wind. That gives the upper arm of the triangle. The heavier stuff is going along the path of the nucleus and that gives the lower arm.

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