APOD: Comet NEOWISE and Nebulae (2020 Jul 20)

Comments and questions about the APOD on the main view screen.
Post Reply
User avatar
APOD Robot
Otto Posterman
Posts: 5345
Joined: Fri Dec 04, 2009 3:27 am
Contact:

APOD: Comet NEOWISE and Nebulae (2020 Jul 20)

Post by APOD Robot » Mon Jul 20, 2020 4:09 am

Image Comet NEOWISE and Nebulae

Explanation: Would you brave wild animals to photograph this sky? One astrophotographer did -- and we all get to reap the rewards. First, thousands of stars were visible with many of the brightest impressively blue. Next, several red-glowing nebulae were discernible, including the California Nebula on the far right, and, above it, the Heart and Soul nebulae. But the real reason to brave the local wildlife was Comet NEOWISE, visible on the left. In the featured long-duration composite taken last week, Comet NEOWISE's blue-glowing ion tail points straight up, away from the rising Sun, while the Sun-reflecting dust tail trails off toward the right. The picture combines three exposures taken consecutively over 10 minutes from the same location near Miedzygórze, Poland. A moonlit dirt road shows the path ahead, while the Śnieznik Mountains is visible on the horizon. Comet C/2020 F3 (NEOWISE) passes its closest to the Earth next week, after which the 5-km wide, evaporating, icy dirtball will fade as it glides back to the outer Solar System.

<< Previous APOD This Day in APOD Next APOD >>

User avatar
Ann
4725 Å
Posts: 13373
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Comet NEOWISE and Nebulae (2020 Jul 20)

Post by Ann » Mon Jul 20, 2020 7:48 am

Ah, lovely! Note the Double Cluster at upper right, to the right of the red Heart and Soul nebulas. The cluster to the upper right of the Double Cluster looks bluer than the cluster to the left, and that's correct too, because the right one does not contain any red giants.

Note Alpha Persei Moving Cluster below the Double Cluster, and the California Nebula at bottom right.

Ann
Color Commentator

User avatar
XgeoX
Science Officer
Posts: 215
Joined: Tue Jun 30, 2020 12:57 pm
AKA: Uncle Rico

Re: APOD: Comet NEOWISE and Nebulae (2020 Jul 20)

Post by XgeoX » Mon Jul 20, 2020 8:45 am

Beautiful image, the foreground really makes it. It resembles an impressionist work.
The only thing I don’t care for is the exaggerated color on the nebula, it looks unnatural and is distracting. Actually I think cutting off the right third would make a stronger composition.
Sorry just the illustrator in me getting nit picky. Beauty Of course is in the eye of the beholder and opions are like... 🙊 This is one of the best, out of many, images of the comet I’ve seen!

Eric

User avatar
orin stepanek
Plutopian
Posts: 8200
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: Comet NEOWISE and Nebulae (2020 Jul 20)

Post by orin stepanek » Mon Jul 20, 2020 12:03 pm

NeowiseNebs_Oszywa_960.jpg
Kudos to Jarek Oszywa: great photo! :D
Some clouds over to the left also!
Orin

Smile today; tomorrow's another day!

spaceaman
Asternaut
Posts: 6
Joined: Sat May 30, 2015 1:29 am

Re: APOD: Comet NEOWISE and Nebulae (2020 Jul 20)

Post by spaceaman » Mon Jul 20, 2020 1:43 pm

For the past few days, I have seen some good pictures of the comet. These are all Earth based pictures. I wonder if we would be able to see some closeup pictures of the comet body in space.

User avatar
Chris Peterson
Abominable Snowman
Posts: 18112
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA
Contact:

Re: APOD: Comet NEOWISE and Nebulae (2020 Jul 20)

Post by Chris Peterson » Mon Jul 20, 2020 1:46 pm

spaceaman wrote: Mon Jul 20, 2020 1:43 pm For the past few days, I have seen some good pictures of the comet. These are all Earth based pictures. I wonder if we would be able to see some closeup pictures of the comet body in space.
For the most part, there would be little advantage to images made in space. With something like the Hubble Telescope, we could get higher resolution, but that's not necessarily useful for an active comet, where the coma obscures the nucleus and where the structure in the coma and tail is large enough to be fully resolved from the ground.
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
https://www.cloudbait.com

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18805
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Would you brave wild animals to photograph this Polish sky?

Post by neufer » Mon Jul 20, 2020 1:57 pm

APOD Robot wrote: Mon Jul 20, 2020 4:09 am
Explanation: Would you brave wild animals to photograph this sky? One astrophotographer did. In the featured long-duration composite taken last week, Comet NEOWISE's blue-glowing ion tail points straight up, away from the rising Sun, while the Sun-reflecting dust tail trails off toward the right. The picture combines three exposures taken consecutively over 10 minutes from the same location near Miedzygórze, Poland. A moonlit dirt road shows the path ahead, while the Śnieznik Mountains is visible on the horizon.
https://www.rollingstone.com/politics/p ... d-1030897/
Art Neuendorffer

User avatar
MarkBour
Subtle Signal
Posts: 1377
Joined: Mon Aug 26, 2013 2:44 pm
Location: Illinois, USA

Re: APOD: Comet NEOWISE and Nebulae (2020 Jul 20)

Post by MarkBour » Tue Jul 21, 2020 12:07 am

I enjoyed looking at Dr. Nemiroff's "Lecture #11 on Comets and Meteors (http://asterisk.apod.com/viewtopic.php?f=24&t=18013)

That lecture did not give much detail about the cause for the shape of a comet's tail. Tentatively, here's my view of it:
A bright comet with two bright tails is a chance to watch a gravitational density-separation process in action. Considering an outbound comet:
  • The heat causes sublimation and out-gassing, which also kicks lots of dust and small particles off of the main nucleus.
  • At the outset, all of these are travelling in the same orbit, and could stay roughly together, as a nucleus with an atmosphere, or exosphere, anyway. But the solar wind and solar radiation both press on this collection. Apparently, the gas molecules are apt to get ionized, which I guess increases the forces they experience from the solar wind. No doubt, the ions can return to the ground state, but they still experience force.
  • So, the gas molecules, being the lightest, are getting a much greater force per unit mass than the rest. And they are thus being accelerated to a higher orbit. Indeed, coming off from the path of the comet, they look almost like a straight line outward.
  • Next, the dust and small particles are getting much less force per unit mass than the gas molecules. (Their surface for impact of the wind and radiation is much smaller than it would be if they had been dissolved into a gas of those same molecules, and they have heavier elements, so they are accelerated far less than the gas.) Nevertheless, the small particles are getting a lot more pressure per unit mass than the nucleus is. So, they spread, each at their own rate, but all generally being pushed into higher orbits than the nucleus. The spread of this tail is not only from the variances in the dust, but also they are spread throughout the differing times of release.
  • The nucleus itself is also being pushed by these forces, but since it is a large dense body, the push it receives is very small. By comparison to the other parts, it is just travelling in an orbit, and stays below all of the rest.
An inbound comet would be undergoing very similar effects. I find it more complex to think about what the tail would look like right after perihelion. Not at all sure how the skewed ""higher" orbits would look as all of this rounds perihelion in comparison to the material coming out on the outward journey.

Chris mentioned doing some very detailed simulations of this. I wonder if his models painted a different picture.
Mark Goldfain

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18805
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: Would you brave wild animals to photograph this Polish sky?

Post by neufer » Tue Jul 21, 2020 2:04 pm

neufer wrote: Mon Jul 20, 2020 1:57 pm
APOD Robot wrote: Mon Jul 20, 2020 4:09 am
Explanation: Would you brave wild animals to photograph this sky? One astrophotographer did. In the featured long-duration composite taken last week, Comet NEOWISE's blue-glowing ion tail points straight up, away from the rising Sun, while the Sun-reflecting dust tail trails off toward the right. The picture combines three exposures taken consecutively over 10 minutes from the same location near Miedzygórze, Poland. A moonlit dirt road shows the path ahead, while the Śnieznik Mountains is visible on the horizon.
Click to play embedded YouTube video.
Art Neuendorffer (MIT class of 1967)

Post Reply