IPB

Welcome Guest ( Log In | Register )

13 Pages V  « < 8 9 10 11 12 > »   
Reply to this topicStart new topic
Interstellar Interlopers, Coming in from the great beyond
nprev
post Jun 28 2018, 04:09 AM
Post #136


Merciless Robot
****

Group: Admin
Posts: 8783
Joined: 8-December 05
From: Los Angeles
Member No.: 602



Either that or just heated dust expanding and poofing out. The entire object was at a few degrees Kelvin for who knows how many millions of years before it entered our system.


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post
HSchirmer
post Sep 2 2018, 02:26 PM
Post #137


Member
***

Group: Members
Posts: 684
Joined: 24-July 15
Member No.: 7619



A papers came out in May measuring the different between the in-bound and out-bound trajectories.

Sugggestions are that it has lost all of it's fine surface dust, so the venting gas is throwing out sand grain sized material, which is almost impossible to detect - so, it's a "dark comet"


NON-GRAVITATIONAL ACCELERATION IN THE ORBIT OF 1I/2017 U1 (‘Oumuamua)
DRAFT 13 pages
https://www.spacetelescope.org/static/archi...3/heic1813a.pdf

Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua)
Published 24 pages
http://www.ifa.hawaii.edu/~meech/papers/20...2018-Nature.pdf




https://www.nasa.gov/feature/jpl/chasing-oumuamua
Go to the top of the page
 
+Quote Post
HSchirmer
post Sep 2 2018, 02:31 PM
Post #138


Member
***

Group: Members
Posts: 684
Joined: 24-July 15
Member No.: 7619



QUOTE (Holder of the Two Leashes @ Jun 27 2018, 10:31 PM) *
Back to being a comet? There appears to have been some outgassing after all ...


I initially argued that they should check for a change in speed because of fragmentation-
if a fragment breaks off a comet around perihelion, the period of highest stresses,
then the fragments carry slighly different velocities, AND you expose fresh ices.

That also raised the interesting possibility is that if Oumaumau was accellerated, the small fragment should be decellerated, and
might be on a solar capture orbit- analagous to models where Neptune can capturing Triton if it starts as a dual-KBO, one is ejected, the other is captured.

However, the paper finds that a fragment would have to be about 1% of the size, and nothing that big was detected.
Go to the top of the page
 
+Quote Post
Explorer1
post Nov 15 2018, 02:30 AM
Post #139


Senior Member
****

Group: Members
Posts: 2073
Joined: 13-February 10
From: Ontario
Member No.: 5221



New Spitzer results published, better constraints on size: http://iopscience.iop.org/article/10.3847/...881/aae88f/meta
Go to the top of the page
 
+Quote Post
HSchirmer
post Nov 15 2018, 02:57 AM
Post #140


Member
***

Group: Members
Posts: 684
Joined: 24-July 15
Member No.: 7619



QUOTE (Explorer1 @ Nov 15 2018, 02:30 AM) *
New Spitzer results published, better constraints on size: http://iopscience.iop.org/article/10.3847/...881/aae88f/meta


Interesting about total mass and aspect ratio.

Given the recent papers providing numbers based on solar photon acceleration suggesting high surface area, and remembering how
papers about Pluto discussed how low pressure and cryo temperatures drives the formation of multi-meter sized ice crystals,
what forms of ice (Ice II, III, IV etc) are stable in the hard vacuum of interstellar space?

Perhaps we saw the largest snowflake ever...
Go to the top of the page
 
+Quote Post
Gerald
post Nov 15 2018, 11:23 PM
Post #141


Senior Member
****

Group: Members
Posts: 2346
Joined: 7-December 12
Member No.: 6780



This phase diagram suggests orthorhombic ice XI.
But more exotic forms of water ice may exist.
And clathrates are always an option to be considered at these low temperatures and mixtures of volatile compounds in interstellar space.
But any volatiles must have been mostly protected by a non-volatile layer. Otherwise, obvious cometary activity would have been observed.
Go to the top of the page
 
+Quote Post
HSchirmer
post Feb 2 2019, 01:15 AM
Post #142


Member
***

Group: Members
Posts: 684
Joined: 24-July 15
Member No.: 7619



QUOTE (Gerald @ Nov 15 2018, 11:23 PM) *
This phase diagram suggests orthorhombic ice XI.
But more exotic forms of water ice may exist.
And clathrates are always an option to be considered at these low temperatures and mixtures of volatile compounds in interstellar space.
But any volatiles must have been mostly protected by a non-volatile layer. Otherwise, obvious cometary activity would have been observed.


Newer simpler explantion - 'Oumuamua broke up on the far side of the sun, what we saw was a spinning dust cloud.


1I/‘OUMUAMUA AS DEBRIS OF DWARF INTERSTELLAR COMETTHAT DISINTEGRATED BEFORE PERIHELION
https://arxiv.org/pdf/1901.08704.pdf
Go to the top of the page
 
+Quote Post
Explorer1
post Feb 18 2019, 04:11 PM
Post #143


Senior Member
****

Group: Members
Posts: 2073
Joined: 13-February 10
From: Ontario
Member No.: 5221



And another theory: https://arxiv.org/abs/1902.04100

A sort of 'fractal snowflake' of incredibly low density (but completely natural!) would also explain the observed properties.
Go to the top of the page
 
+Quote Post
dudley
post Feb 19 2019, 03:17 PM
Post #144


Junior Member
**

Group: Members
Posts: 68
Joined: 27-March 15
Member No.: 7426



The 'fractal snowflake' interpretation is intriguing. There seem to be problems with it, though. The authors of the paper mention some of these.
It seems difficult to understand how such a flimsy object could withstand the forces that wrenched it from its star and sent it our way. Even the relatively rapid rotation of Oumuamua would seem to threaten the continued existence of such a delicate structure.

Then, too, it's assumed that a 'fractal snowflake' would have formed beyond the snowline in its system. It seems possible that it would have begun to melt, and come apart when it passed near the Sun, on its journey through our solar system.
Go to the top of the page
 
+Quote Post
moustifouette
post Sep 12 2019, 10:07 AM
Post #145


Newbie
*

Group: Members
Posts: 17
Joined: 8-September 15
Member No.: 7773



Hello,

Discovery of a second interstellar candidate, this time a comet


here
Go to the top of the page
 
+Quote Post
HSchirmer
post Sep 12 2019, 12:22 PM
Post #146


Member
***

Group: Members
Posts: 684
Joined: 24-July 15
Member No.: 7619



QUOTE (dudley @ Feb 19 2019, 03:17 PM) *
The 'fractal snowflake' interpretation is intriguing. There seem to be problems with it, though. The authors of the paper mention some of these.
It seems difficult to understand how such a flimsy object could withstand the forces that wrenched it from its star and sent it our way. Even the relatively rapid rotation of Oumuamua would seem to threaten the continued existence of such a delicate structure.

Then, too, it's assumed that a 'fractal snowflake' would have formed beyond the snowline in its system. It seems possible that it would have begun to melt, and come apart when it passed near the Sun, on its journey through our solar system.


Perhaps another degree of freedom is the rotational energy-think of "a snowglobe of fractal snowflakes", or a "cold synestia".
It should look something like Saturn's moon Methone, a gravitationally bound snowstorm.

Instead of a collision, imagine a slow YORP effect spin upon a rubble pile asteroid, like Ryugu or Hyabusa, until they are disks or a torus.

Finally, if you imagine a body that is a rubble pile composed of rock cemented by ice. If the object has not had time to evolve a dark comet-style surface crust, then you might have a cometary body with a gravel surface. That might allow significant heat conduction into a porous interior; either from direct rock-to-rock conduction or by sublimated surface ices in gas form diffusing into the cold porous interior and refreezing.

Interesting to think about what happens for an object of rock-cemented-by-ices; if the object warms uniformly.
Once it reaches ice sublimation throughout the interior, additional warming could create a 3-dimensional fluidized bed of rock granules.
Go to the top of the page
 
+Quote Post
Explorer1
post Sep 12 2019, 12:39 PM
Post #147


Senior Member
****

Group: Members
Posts: 2073
Joined: 13-February 10
From: Ontario
Member No.: 5221



Here we go again!

Looks to be a comet this time, with an even higher eccentricity! And this time it's still on the way in, and should be visible for many months!
Go to the top of the page
 
+Quote Post
dtolman
post Sep 12 2019, 02:52 PM
Post #148


Member
***

Group: Members
Posts: 124
Joined: 20-April 05
Member No.: 291



Most impressive is that it wasn't an automated survey or space telescope that found it - but an amateur comet hunter with a home built .65 m telescope! Comet should be visible for a year in large scopes.
Go to the top of the page
 
+Quote Post
pbanholzer
post Sep 15 2019, 03:48 AM
Post #149


Junior Member
**

Group: Members
Posts: 23
Joined: 28-September 17
From: Huntsville, Alabama
Member No.: 8258



First visual spectrum of C2019/Q4 http://www.iac.es/divulgacion.php?op1=16&a...0wY3wWUq58FS8OQ
Go to the top of the page
 
+Quote Post
nprev
post Sep 15 2019, 09:30 AM
Post #150


Merciless Robot
****

Group: Admin
Posts: 8783
Joined: 8-December 05
From: Los Angeles
Member No.: 602



Topic title changed to plural. smile.gif


--------------------
A few will take this knowledge and use this power of a dream realized as a force for change, an impetus for further discovery to make less ancient dreams real.
Go to the top of the page
 
+Quote Post

13 Pages V  « < 8 9 10 11 12 > » 
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 28th March 2024 - 02:33 PM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member.