Authors: A.J.C. Almeida, N. Peixinho, A.C.M. Correia

(Submitted on 5 Oct 2009 (v1), last revised 9 Oct 2009 (this version, v2))

Abstract: Neptune Trojans and Plutinos are two subpopulations of trans-Neptunian objects located in the 1:1 and the 3:2 mean motion resonances with Neptune, respectively, and therefore protected from close encounters with the planet. However, the orbits of these two kinds of objects may cross very often, allowing a higher collisional rate between them than with other kinds of trans-Neptunian objects, and a consequent size distribution modification of the two subpopulations.

Observational colors and absolute magnitudes of Neptune Trojans and Plutinos show that i) there are no intrinsically bright (large) Plutinos at small inclinations, ii) there is an apparent excess of blue and intrinsically bright (small) Plutinos, and iii) Neptune Trojans possess the same blue colors as Plutinos within the same (estimated) size range do.

For the present subpopulations we analyzed the most favorable conditions for close encounters/collisions and address any link there could be between those encounters and the sizes and/or colors of Plutinos and Neptune Trojans. We also performed a simultaneous numerical simulation of the outer Solar System over 1 Gyr for all these bodies in order to estimate their collisional rate.

We conclude that orbital overlap between Neptune Trojans and Plutinos is favored for Plutinos with large libration amplitudes, high eccentricities, and small inclinations. Additionally, with the assumption that the collisions can be disruptive creating smaller objects not necessarily with similar colors, the present high concentration of small Plutinos with small inclinations can thus be a consequence of a collisional interaction with Neptune Trojans and such hypothesis should be further analyzed.

Comments: 15 pages, 9 figures, 6 tables, accepted for publication in A&A

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

DOI: 10.1051/0004-6361/200911943

Cite as: arXiv:0910.0865v2 [astro-ph.EP]

Submission history

From: Alexandre Correia [view email]

[v1] Mon, 5 Oct 2009 21:11:27 GMT (1697kb)

[v2] Fri, 9 Oct 2009 11:23:44 GMT (1697kb)

http://arxiv.org/abs/0910.0865

Authors: Igor V. Moskalenko, Troy A. Porter

(Submitted on 3 Jan 2009)

Abstract: We calculate the gamma-ray albedo due to cosmic-ray interactions with debris (small rocks, dust, and grains) in the Oort Cloud. We show that under reasonable assumptions a significant proportion of what is called the “extragalactic gamma-ray background” could be produced at the outer frontier of the solar system and may be detectable by the Large Area Telescope, the primary instrument on the Fermi Gamma-Ray Space Telescope.

If detected it could provide unique direct information about the total column density of material in the Oort Cloud that is difficult to access by any other method. The same gamma ray production process takes place in other populations of small solar system bodies such as Main Belt asteroids, Jovian and Neptunian Trojans, and Kuiper Belt objects. Their detection can be used to constrain the total mass of debris in these systems.

Comments: 4 pages, 1 figure, accepted by Astrophysical Journal Letters

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0901.0304v1 [astro-ph]

Submission history

From: Troy Porter [view email]

[v1] Sat, 3 Jan 2009 03:34:10 GMT (45kb)

http://arxiv.org/abs/0901.0304

Oligarchic planet formation theory predicts potentially dozens of Mars mass objects out there, and Al Stern has predicted potentially a thousand Pluto-sized objects. That’s a lot of real estate. But just what we can do with such in ours present energy challenged stage I’m unsure. Once fusion power becomes sufficiently well developed all those objects could become potential habitats.

A more SF idea I like to imagine is that wormholes could be developed as light-pipes and thus all those worlds would become viable. With wormholes also for rapid transit the Outer Solar System could potentially become more worth our colonisation efforts than the nearer stars if planet formation is as variable in its results as recent simulations suggest.

To land on an object like this you need to precisely match its velocity. That means the craft is already on the same orbit, and therefore the object is superfluous. Worse, that particular orbit constrains which interstellar objects we could observe – better to pick the observation targets first and the orbit second.

Further, assuming others are as impatient as I am, this is a slow way to get to 550 AU. I’d rather our gravitational lens observatory returned results in my lifetime.

On an different note, one SF novel (Lucifer’s Hammer, and I would not be surprised to hear about others in the same vein) posited a relatively large and unobserved minor planet in the Oort cloud (or maybe it was Kuiper belt) that every so often alters the eccentricity of other, smaller objects so that they pass into the inner solar system and cause havoc. In this novel one such object encounters Earth.