APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 4478
Joined: Fri Dec 04, 2009 3:27 am

APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by APOD Robot » Fri Oct 07, 2011 4:14 am

Image The Comet Hartley 2 Cruise

Explanation: Early last November, small but active Comet Hartley 2 (103/P Hartley) became the fifth comet imaged close-up by a spacecraft from planet Earth. Still cruising through the solar system with a 6 year orbital period, Hartley 2 is making astronomical headlines again. New Herschel Space Observatory measurements indicate that the water found in this comet's thin atmosphere or coma has the same ratio of the hydrogen isotope deuterium (in heavy water) as the oceans of our fair planet. Hartley 2 originated in the distant Kuiper Belt, a region beyond the orbit of Neptune that is a reservoir of icy cometary bodies and dwarf planets. Since the ratio of deuterium is related to the solar system environment where the comet formed, the Herschel results indicate that Kuiper Belt comets could have contributed substantial amounts of water to Earth's oceans. Comet Hartley 2 appears in this starry skyscape from last November sporting a tantalizing greenish coma appropriately sailing through the nautical constellation Puppis. Below the comet are open star clusters M47 (right) and M46 (left).

<< Previous APODDiscuss Any APOD Next APOD >>
[/b]

Guest

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by Guest » Fri Oct 07, 2011 4:42 am

A beautiful photo, but my attention was drawn to the oddly (orange) colored grouping of stars in the center of the photo, just below the axis of a straight line drawn between the two dominant clusters. Since I'm not all that familiar with the area,my first guess is processing artifact. Anybody want to chime in?

User avatar
Ann
4725 Å
Posts: 11650
Joined: Sat May 29, 2010 5:33 am

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by Ann » Fri Oct 07, 2011 5:10 am

That would seem to be cluster NGC 2425. The reason for the orange color is twofold. First, the cluster is old, apparently a few billion years old, which means that the bright blue stars of the clusters have died long ago, and the brightest stars of the cluster are orange. I've also found a claim that the cluster is 3550 parsecs away, which would be more than 10,000 light-years. Whether or not the exact distance is 10,000 light-years, it is clear that the cluster is far away, and we can be sure that there is a lot of interstellar dust between us and the cluster. The dust causes reddening by scattering away blue light. NGC 2425 is undoubtedly very dust-reddened, which is the main reason why it looks so strikingly red in this image.

By comparison, the same source that puts NGC 2425 at 3550 parsecs puts M46 at 1510 parsecs and M47 at 490 parsecs. Also, this same source claims that M46 is less than a billion years old, and M47 is less than a hundred million.

Ann
Color Commentator

User avatar
bystander
Apathetic Retiree
Posts: 20807
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by bystander » Fri Oct 07, 2011 7:14 am

Researchers gain new insights into Comet Hartley 2
http://asterisk.apod.com/viewtopic.php?f=31&t=23714
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

nstahl
Science Officer
Posts: 233
Joined: Mon Nov 29, 2004 4:08 am

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by nstahl » Fri Oct 07, 2011 9:58 am

Earth’s Oceans: A Cometary Source After All?
Centauri Dreams wrote:Getting water into the inner Solar System is an interesting exercise. There has to be a mechanism for it, because the early Earth formed at temperatures that would have caused any available water to have evaporated. Scientists have long speculated that water must have been delivered either through comets or asteroids once the Earth had cooled enough to allow liquid water to exist. The former was preferred because the water content in comets is so much higher than in asteroids.

But the theory had problems, not the least of which was that comets studied in this regard showed deuterium levels twice that of Earth’s oceans. The ratio of deuterium and hydrogen, both made just after the Big Bang, can vary in water depending on its location because local conditions can affect the chemical reactions that go into making ice in space. A comparison of the deuterium to hydrogen ratio in extraterrestrial objects can be compared to water found in Earth’s oceans to identify the source of our water. Now comet Hartley 2 swings into the picture, for researchers have announced that its hydrogen/deuterium ratio is similar to Earth’s oceans.
...
Remember, previous comet studies had found hydrogen/deuterium ratios different from our oceans. The difference between these comets and Hartley 2 may be that Hartley 2 was formed in the Kuiper Belt, whereas other comets studied in this regard are thought to have first formed near Jupiter and Saturn before being flung out by the gravitational effects of the gas giants, returning millions of years later for their pass around the Sun. The hydrogen/deuterium ratio we see in water ice may well have been different in the Kuiper Belt than in ice that first formed in the inner system, where conditions are much warmer. Further comets studies may confirm the idea.
...
Surely the early oceans were the result of both comet and asteroid impacts, but the new findings point back to comets as major players. Even so, we have plenty of work to do to understand the role of the lightest elements and their isotopes in the early Solar System. Six comets besides Hartley 2 have been examined for hydrogen/deuterium levels, all with deuterium levels approximately twice that found in Earth water. Kuiper Belt comets were once thought to have even higher deuterium levels than Oort Cloud comets, an idea the Hartley 2 results have now refuted.
...

User avatar
Indigo_Sunrise
Science Officer
Posts: 438
Joined: Fri Jul 15, 2005 1:40 pm
Location: Md

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by Indigo_Sunrise » Fri Oct 07, 2011 11:06 am

Ann wrote:....found a claim,
....the same source,
Also, this same source
Ann, can you share your source/s via a link, perhaps? (Of course, if it's something you merely 'searched' for, can you let us know that, also?)


Star clusters really intrigue me, and this image is a double bonus - with green-tinged Comet Hartley 2 (103/P Hartley)floating through.
Excellent image!

8-)
Forget the box, just get outside.

User avatar
Indigo_Sunrise
Science Officer
Posts: 438
Joined: Fri Jul 15, 2005 1:40 pm
Location: Md

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by Indigo_Sunrise » Fri Oct 07, 2011 11:10 am

And bystander - LOVE the new avatar!


:D
Forget the box, just get outside.

User avatar
orin stepanek
Plutopian
Posts: 6988
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by orin stepanek » Fri Oct 07, 2011 11:45 am

Indigo_Sunrise wrote:And bystander - LOVE the new avatar!


:D
I just wonder what he'll be dressed up as tomorrow. :mrgreen:
Orin

Smile today; tomorrow's another day!

User avatar
owlice
Guardian of the Codes
Posts: 8389
Joined: Wed Aug 04, 2004 4:18 pm
Location: Washington, DC

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by owlice » Fri Oct 07, 2011 12:00 pm

He might be wondering that, too! :mrgreen:
A closed mouth gathers no foot.

User avatar
orin stepanek
Plutopian
Posts: 6988
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by orin stepanek » Fri Oct 07, 2011 12:17 pm

owlice wrote:He might be wondering that, too! :mrgreen:
Ahh! owlice; I see you're sporting a new look also. 8-)
Orin

Smile today; tomorrow's another day!

User avatar
owlice
Guardian of the Codes
Posts: 8389
Joined: Wed Aug 04, 2004 4:18 pm
Location: Washington, DC

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by owlice » Fri Oct 07, 2011 12:19 pm

Apparently so! :shock:
A closed mouth gathers no foot.

neptunium

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by neptunium » Fri Oct 07, 2011 12:36 pm

What's yours anyway, owlice?

casuspacem

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by casuspacem » Fri Oct 07, 2011 1:00 pm

"Since the ratio of deuterium is related to the solar system environment where the comet formed, the Herschel results indicate that Kuiper Belt comets could have contributed substantial amounts of water to Earth's oceans."

----"In the six hundredth year of Noah's life, in the second month, on the seventeenth day of the month, on that day all the fountains of the great deep burst forth, and the windows of the heavens were opened." Gen 7:11

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18562
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by neufer » Fri Oct 07, 2011 1:15 pm

casuspacem wrote:
"Since the ratio of deuterium is related to the solar system environment where the comet formed, the Herschel results indicate that Kuiper Belt comets could have contributed substantial amounts of water to Earth's oceans."

----"In the six hundredth year of Noah's life, in the second month, on the seventeenth day of the month, on that day all the fountains of the great deep burst forth, and the windows of the heavens were opened." Gen 7:11
At the time the animals came in the form of Methane:

http://asterisk.apod.com/viewtopic.php? ... ne#p156025
Art Neuendorffer

User avatar
Ann
4725 Å
Posts: 11650
Joined: Sat May 29, 2010 5:33 am

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by Ann » Fri Oct 07, 2011 1:15 pm

Indigo_Sunrise wrote:
Ann wrote:....found a claim,
....the same source,
Also, this same source
Ann, can you share your source/s via a link, perhaps? (Of course, if it's something you merely 'searched' for, can you let us know that, also?)


Star clusters really intrigue me, and this image is a double bonus - with green-tinged Comet Hartley 2 (103/P Hartley)floating through.
Excellent image!

8-)
I use a software from Project Pluto, called Guide 8. It contains information, or assessments, for a lot of clusters. When I clicked on NGC 2425, a smallish window opened with the information I just described. The source used by Guide for this cluster, and for M46 and M47, is http://www.astro.iag.usp.br/~wilton/clusters.txt.

Ann
Color Commentator

LMartin

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by LMartin » Fri Oct 07, 2011 1:46 pm

It's going to Kuiper belt and back here in 6 yrs? Let's gravitationally attach a telescope next to it and get some nice picts of KBOs! :shock:

I think even comet's coma is less polluting the view than Earth's atmosphere. Although I'm not sure if there is any difference in delta v compared to sanding such scope as itself (taking comet's low mass into account).

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18562
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by neufer » Fri Oct 07, 2011 1:57 pm

LMartin wrote:
It's going to Kuiper belt and back here in 6 yrs?
No.
Art Neuendorffer

User avatar
NoelC
Creepy Spock
Posts: 876
Joined: Sun Nov 20, 2005 2:30 am
Location: South Florida, USA; I just work in (cyber)space

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by NoelC » Fri Oct 07, 2011 2:34 pm

neufer wrote:At the time the animals came in the form of Methane
No cow pie in the sky:

http://www.jgpress.com/archives/_free/000550.html

-Noel

Booster

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by Booster » Fri Oct 07, 2011 4:38 pm

The oceans are big. Really big. And really, really deep. I find it hard to believe that all of that water came from comet impacts. And if they did, wouldn't comets of that mass cause planetary deformation sufficient to have reheated its surface to vaporizing temperatures again?

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18562
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

really, really deep?

Post by neufer » Fri Oct 07, 2011 5:00 pm

Booster wrote:
The oceans are big. Really big. And really, really deep. I find it hard to believe that all of that water came from comet impacts. And if they did, wouldn't comets of that mass cause planetary deformation sufficient to have reheated its surface to vaporizing temperatures again?
  • The total mass of Eris is about 16.7×1021 kg.

    The total mass of Pluto is about 13.1×1021 kg.

    The total mass of Charon is about 1.5×1021 kg.

    The total mass of [Earth's] hydrosphere is about 1.4×1021 kg
http://en.wikipedia.org/wiki/Moon#Formation wrote:
<<The prevailing hypothesis today is that the Earth–Moon system formed as a result of a giant impact: a Mars-sized body hit the nearly formed proto-Earth, blasting material into orbit around the proto-Earth, which accreted to form the Moon. Giant impacts are thought to have been common in the early Solar System. Computer simulations modelling a giant impact are consistent with measurements of the angular momentum of the Earth–Moon system, and the small size of the lunar core; they also show that most of the Moon came from the impactor, not from the proto-Earth. However, meteorites show that other inner Solar System bodies such as Mars and Vesta have very different oxygen and tungsten isotopic compositions to the Earth, while the Earth and Moon have near-identical isotopic compositions. Post-impact mixing of the vaporized material between the forming Earth and Moon could have equalized their isotopic compositions, although this is debated. The large amount of energy released in the giant impact event and the subsequent reaccretion of material in Earth orbit would have melted the outer shell of the Earth, forming a magma ocean.>>
Art Neuendorffer

User avatar
Chris Peterson
Abominable Snowman
Posts: 16215
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by Chris Peterson » Fri Oct 07, 2011 5:02 pm

Booster wrote:The oceans are big. Really big. And really, really deep. I find it hard to believe that all of that water came from comet impacts. And if they did, wouldn't comets of that mass cause planetary deformation sufficient to have reheated its surface to vaporizing temperatures again?
The oceans amount to about a billion cubic kilometers of water. With a typical comet delivering perhaps one cubic kilometer of water, filling the oceans over a few tens of millions of years isn't unreasonable, given the expected number of comets diving into the inner Solar System at its early stages.

Collisions from comets might crater the Earth, but they wouldn't deliver enough energy (by many orders of magnitude) to significantly reheat the surface. And the energies involved would not dissociate most of the water; it would simply end up in the atmosphere as water vapor.

There is nothing about the history of the Solar System or basic physics that argues against much of the Earth's surface water coming from comets; it really just comes down to observational evidence of Kuiper Belt objects, and no doubt that will accumulate over the next years.
Chris

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

TNT
Science Officer
Posts: 289
Joined: Mon Oct 03, 2011 1:57 am
Location: Heart of America

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by TNT » Fri Oct 07, 2011 9:40 pm

Hey, cool APOD! I've always wanted to see a comet, although I missed my chance with Comet Garradd... :(

Still, the picture with the comet and the two star clusters is amazing! :ssmile:

zerro1
Ensign
Posts: 29
Joined: Sun Aug 14, 2011 1:12 am

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by zerro1 » Fri Oct 07, 2011 11:26 pm

This is a fantastic Image. Really nice star color. Well Done!

Red Lord of Mars

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by Red Lord of Mars » Sat Oct 08, 2011 5:27 pm

Hello..

First timer here... I wanted to ask if the small formation in the lower left corner of the pic is the Cat's Eye Nebula..

It looks so much like it, that I am surprised no one else noticed it... :o

Red Lord

User avatar
Chris Peterson
Abominable Snowman
Posts: 16215
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: The Comet Hartley 2 Cruise (2011 Oct 07)

Post by Chris Peterson » Sat Oct 08, 2011 5:40 pm

Red Lord of Mars wrote:I wanted to ask if the small formation in the lower left corner of the pic is the Cat's Eye Nebula...
It isn't the Cat's Eye Nebula, although it is another planetary nebula, NGC 2438. While it appears to be a member of M46, it is actually an unrelated object, probably between us and M46.

(The Cat's Eye is in Draco, which is very far from Puppis, where this APOD image lies.)
Chris

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