Betydningen af interstellare objekter som 'Oumuamua for panspermia hypotesen

[BjarneModerator Super Nova]

Implications of Captured Interstellar Objects for Panspermia and Extraterrestrial Life

We estimate the capture rate of interstellar objects by means of three-body gravitational interactions. We apply this model to the Sun-Jupiter system and the Alpha Centauri A&B binary system, and find that the radius of the largest captured object is a few tens of km and Earth-sized respectively. We explore the implications of our model for the transfer of life by means of rocky material. The interstellar comets captured by the “fishing net” of the Solar system can be potentially distinguished by their differing ratios of oxygen isotopes through high-resolution spectroscopy of water vapor in their tails.

 

[BjarneModerator Super Nova]

Dobbeltstjerner som Alfa Cen optræder som trafikale knudepunkter for interstellare objekter med masser helt op til planeter af jord-størrelse. De kan derfor være med til at sprede levende organismer i Mælkevejen. Men man bør være forsigtig med for vidtgående slutninger, da statistikken over interstellare objekter kun baserer sig på et enkelt tilfælde, ‘Oumuamua. Vi venter spændt på flere opdagelser.

 

[BjarneModerator Super Nova]

Arxiv.org artiklen fra 30. november om ‘Oumuamuas tumlende rotation er udkommet i tidsskriftet Nature:

The tumbling rotational state of 1I/‘Oumuamua

The discovery1 of 1I/2017 U1 (1I/‘Oumuamua) has provided the first glimpse of a planetesimal born in another planetary system. This interloper exhibits a variable colour within a range that is broadly consistent with local small bodies, such as the P- and D-type asteroids, Jupiter Trojans and dynamically excited Kuiper belt objects. 1I/‘Oumuamua appears unusually elongated in shape, with an axial ratio exceeding 5:1. Rotation period estimates are inconsistent and varied, with reported values between 6.9 and 8.3 h. Here, we analyse all the available optical photometry data reported to date. No single rotation period can explain the exhibited brightness variations. Rather, 1I/‘Oumuamua appears to be in an excited rotational state undergoing non-principal axis rotation, or tumbling. A satisfactory solution has apparent lightcurve frequencies of 0.135 and 0.126 h⁻¹ and implies a longest-to-shortest axis ratio of ≳5:1, although the available data are insufficient to uniquely constrain the true frequencies and shape. Assuming a body that responds to non-principal axis rotation in a similar manner to Solar System asteroids and comets, the timescale to damp 1I/‘Oumuamua’s tumbling is at least one billion years. 1I/‘Oumuamua was probably set tumbling within its parent planetary system and will remain tumbling well after it has left ours.

 

[BjarneModerator Super Nova]

Der er kommet en ny artikel i Scientific American om ‘Oumuamua:

Will Astronomers Be Ready for the Next ‘Oumuamua?

The encounter with ‘Oumuamua, although brief, was just the iceberg-tip of an entirely new emerging subfield of astronomy: the study of interstellar objects as a population—something theorists previously could only dream about. The lessons from ‘Oumuamua are now forcing planetary scientists and astronomers to reconsider the solar system with new eyes, and presaging the arrival of our next visitor.

For Carlos de la Fuente Marcos at the Complutense University of Madrid and his colleagues, ‘Oumuamua’s passing inspired an immediate question. Its orbital path was hyperbolic, along a curve that sweeps out from the solar system to infinity instead of closing in on itself like an ellipse. Aside from interstellar visitors, local comets and asteroids can also escape the solar system by being bent onto hyperbolic paths by gravitational tweaks from the sun or the planets. Astronomers could rule out a “local” origin for ‘Oumuamua, which was flying too fast and unaligned with the solar system’s planets to have come from anywhere besides interstellar space. Marcos wondered, though, whether other ‘Oumuamua-like objects might lurk within the full set of hyperbolic objects astronomers have observed in the past.

 

[BjarneModerator Super Nova]

Artiklen i Scientific American er baseret på denne artikel i arxiv.org, som jeg desværre har overset:

Where the Solar system meets the solar neighbourhood: patterns in the distribution of radiants of observed hyperbolic minor bodies

Observed hyperbolic minor bodies might have an interstellar origin, but they can be natives of the Solar system as well. Fly-bys with the known planets or the Sun may result in the hyperbolic ejection of an originally bound minor body; in addition, members of the Oort cloud could be forced to follow inbound hyperbolic paths as a result of secular perturbations induced by the Galactic disc or, less frequently, due to impulsive interactions with passing stars. These four processes must leave distinctive signatures in the distribution of radiants of observed hyperbolic objects, both in terms of coordinates and velocity. Here, we perform a systematic numerical exploration of the past orbital evolution of known hyperbolic minor bodies using a full N-body approach and statistical analyses to study their radiants. Our results confirm the theoretical expectations that strong anisotropies are present in the data. We also identify a statistically significant overdensity of high-speed radiants towards the constellation of Gemini that could be due to the closest and most recent known fly-by of a star to the Solar system, that of the so-called Scholz’s star. In addition to and besides 1I/2017 U1 (`Oumuamua), we single out eight candidate interstellar comets based on their radiants’ velocities.

 

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