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The LiveScience article Incredible Hulk? Nah, This Glowing, Green Light in the Night Sky Is a Comet published just hours ago discusses Comet PANSTARRS C/2017 S3 and mentions:

bright bursts exploding from its surface twice in close succession — first on June 30, and then again about two weeks later, Sky and Telescope reported. As Hulk himself might say, "Comet flash!"

The linked Sky and Telescope article PanSTARRS Comet, Rocked by Outburst, Goes Green is dated July 17, 2018 and offers the tantallizing information that

Comet PanSTARRS (C/2017 S3) has erupted again! Now bright enough to see in binoculars, it might become a naked-eye object if it survives until perihelion.

Question: How bright is the comet now, and how is it predicted to behave in the next week or two (baring further outbursts)?


below: "On July 15, Comet PanSTARRS (C/2017 S3) appeared bright and well condensed with a narrow ion tail." Photo Credit: Michael Jäger. From here.

enter image description here

update: The Universe Today's article Catch Comet C/2017 S3 PANSTARRS In Outburst links to S Seiichi Yoshida's page for the comet, but there's no recent data!

enter image description here

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    $\begingroup$ It is now very near the sun in the sky, it is probably lost in the the twilight to earth bound observers $\endgroup$ – James K Aug 7 '18 at 10:41
  • $\begingroup$ @JamesK thanks for that, I feel better now; that I'm not missing something spectacular. $\endgroup$ – uhoh Aug 7 '18 at 15:20
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The solar elongation (angle from the Sun to the object) is about 15 degrees right now and decreasing as the comet moves in towards perihelion (closest approach to the Sun) on August 15. As James K says this means that comet is lost in the Sun's glare. Anything below 30 degrees solar elongation is tricky to impossible to see.

Assuming it survives the close perihelion passage of 0.21 AU, it is predicted to enter the field of view of the SOHO LASCO Sun-observing coronographs on August 24:

Assuming there is anything left of C/2017 S3, perihelion will occur this month on the 15th at a rather small perihelion distance of 0.21 AU. Being only 2 weeks from perihelion, it is already at a small elongation of 31 degrees on the 1st. Most observers will lose sight of it during the first week of August as its elongation drops below 25 degrees on the 4th and 20 degrees on the 6th. If the comet is still a going concern it will be visible in the SOHO LASCO C3 FOV between August 24 and September 13. The comet appear around the 7:30 position, passes to the east (left) of the Sun (halfway between the Sun and edge of FOV) and exits the FOV around the 12:30 position.

The above info is from the ALPO Comet Section. Latest LASCO image and movies are available here and many other places.

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  • $\begingroup$ This is great! Thank you for taking the time to write a thorough and well supported answer. The link to ALPO is really useful, and looking forward to "seeing" the comet in LASCO soon! (some older homebrew "movies" here and here). $\endgroup$ – uhoh Aug 7 '18 at 15:27
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    $\begingroup$ Thank you for the nice comment, hopefully it will survive perihelion. I know well the disappointment of organizing observations as part of a large campaign for a comet that didn't survive perihelion passage (C/2012 S1 ISON) $\endgroup$ – astrosnapper Aug 7 '18 at 15:36
  • $\begingroup$ I hope you didn't lose money on travel arrangements to another hemisphere as part of the campaign. $\endgroup$ – uhoh Aug 7 '18 at 15:42
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    $\begingroup$ No the telescope robots went off and did other people's observations instead $\endgroup$ – astrosnapper Aug 7 '18 at 15:55

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