Starship Asterisk*

Stardust and Comet Tails

Explanation: Heading for its closest approach to the Sun, or perihelion, on December 19 comet C/2017 K2 (PanSTARRS) remains a sight for telescopic observers as it sweeps through planet Earth's skies in the constellation Scorpius. The comet currently sports a greenish coma, long whitish dust tail, and short ion tail in this deep image from August 18. The 2x3 degree wide field of view includes part of the dusty nebula IC 4592 reflecting blue starlight. Also known as the Blue Horsehead Nebula, IC 4592 is about 400 light-years distant while the comet is just under 17 light-minutes away. First spotted at a distance well beyond the orbit of Saturn C/2017 K2 is on its maiden voyage to the inner solar system, a pristine visitor from the remote Oort cloud.

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Nice and interesting image!


Note the colors. The hot stars, Beta Scorpii (bottom right) and Nu Scorpii (inside the Blue Horsehead reflection nebula, pictured by Gideon Golan) look very blue. The comet is strikingly green. It is traffic light green, not chlorophyll green.

The reflection nebula is blue close to the illuminating star, Nu Sco, but it turns more and more reddish farther away from the star. The dust is intrinsically reddish, and it also reflects the non-blue overall color of the Milky Way.

I find the faintness of the comet's short ion tail interesting. According to the caption, this is C/2017 K2 (PanSTARRS)'s first infall into the inner Solar system, and I would have expected this "maiden comet" to be quite gas-rich. Not so, apparently. This appears to be a comet that has always been poor in volatiles.

Ann

Blue Horses Head Nebula is stardust IC 4582! ! Goes nice with
comet!

Ann wrote: ↑Sat Aug 20, 2022 4:59 am I find the faintness of the comet's short ion tail interesting. According to the caption, this is C/2017 K2 (PanSTARRS)'s first infall into the inner Solar system, and I would have expected this "maiden comet" to be quite gas-rich. Not so, apparently. This appears to be a comet that has always been poor in volatiles.

This comet is still at a distance of 2 AU, beyond the orbit of Mars. It is only now getting close enough to the Sun to start showing high activity.

What's the identiry of tail-like structure extending to upper left?

If it is the dust tail, the direction would be similar to the ion tail, i.e., left (opposit to the sun). I understand that sometimes two tails draw 'V', but this time tails draw 'L', too wide angled.
As this structure seems to be along the orbit, and it extends to the opposit to the comet's moving direction, I suspect this is the dust 'trail', not tail. If so, however, it is much brighter than typical trail.

a) it's angled dust tail
b) it's bright dust trail
c) both, or, other interpretation

RET wrote: ↑Sat Aug 20, 2022 4:42 pm What's the identiry of tail-like structure extending to upper left?

If it is the dust tail, the direction would be similar to the ion tail, i.e., left (opposit to the sun). I understand that sometimes two tails draw 'V', but this time tails draw 'L', too wide angled.
As this structure seems to be along the orbit, and it extends to the opposit to the comet's moving direction, I suspect this is the dust 'trail', not tail. If so, however, it is much brighter than typical trail.

a) it's angled dust tail
b) it's bright dust trail
c) both, or, other interpretation

APOD Robot wrote: ↑Sat Aug 20, 2022 4:05 am
Explanation: ... The comet currently sports a greenish coma, long whitish dust tail, and short ion tail in this deep image ...

bystander wrote: ↑Sat Aug 20, 2022 6:48 pm

RET wrote: ↑Sat Aug 20, 2022 4:42 pm What's the identiry of tail-like structure extending to upper left?

If it is the dust tail, the direction would be similar to the ion tail, i.e., left (opposit to the sun). I understand that sometimes two tails draw 'V', but this time tails draw 'L', too wide angled.
As this structure seems to be along the orbit, and it extends to the opposit to the comet's moving direction, I suspect this is the dust 'trail', not tail. If so, however, it is much brighter than typical trail.

a) it's angled dust tail
b) it's bright dust trail
c) both, or, other interpretation

APOD Robot wrote: ↑Sat Aug 20, 2022 4:05 am
Explanation: ... The comet currently sports a greenish coma, long whitish dust tail, and short ion tail in this deep image ...

Thanks, of course I'd read the text.

I think it's more (bright) trail, rather than (angled) tail. But, okay, I'll accept the text. It's tail.

Have a nice weekend