Exploration of `Oumuamua-like objects

[BjarneModerator Super Nova]

The Feasibility and Benefits of In Situ Exploration of `Oumuamua-like objects

A rapid accumulation of observations and interpretation have followed in the wake of 1I Oumuamua’s passage through the inner Solar System. We briefly outline the consequences that this first detection of an interstellar asteroid implies for the planet-forming process, and we assess the near-term prospects for detecting and observing (both remotely and in situ) future Solar System visitors of this type. Drawing on detailed heat-transfer calculations that take both Oumuamua’s unusual shape and its chaotic tumbling into account, we affirm that the lack of a detectable coma in deep images of the object very likely arises from the presence of a radiation-modified coating of high molecular weight material (rather than a refractory bulk composition). Assuming that Oumuamua is a typical representative of a larger population with a kinematic distribution similar to Population I stars in the local galactic neighborhood, we calculate expected arrival rates, impact parameters and velocities of similar objects and assess their prospects for detection using operational and forthcoming facilities. Using Oumuamua as a proof-of-concept, we assess the prospects for missions that intercept interstellar objects (ISOs) using conventional chemical propulsion. Using a “launch on detection” paradigm, we estimate wait times of order 10 years between favorable mission opportunities with the detection capabilities of the Large-Scale Synoptic Survey Telescope (LSST), a figure that will be refined as the population of interstellar asteroids becomes observationally better constrained.

[BjarneModerator Super Nova]

Mysterious asteroid from beyond our solar system probably came from a place with two stars

Late last year, astronomers spotted the first object to enter our solar system from interstellar space—a somewhat reddish, cigar-shaped body named ‘Oumuamua. Now, a new study hints that this exotic interloper most likely began its voyage after being cast out of a double-star system.

Astronomers first classified ‘Oumuamua (Hawaiian for “scout”) as a comet, but later observations didn’t reveal the telltale signs, including clouds of dust or water vapor. That, plus the 400-meter-long object’s high speed and odd trajectory, strongly suggested that ‘Oumuamua was an asteroid, not a comet, from beyond our solar system.

But very few single-star solar systems would be able to cast out a waterless object like an asteroid, a new study suggests. That’s because such a feat would require gravitational interactions with a planet the size of Saturn or larger, something present in only about 10% of single-star solar systems near us in the Milky Way.

But solar systems that have two suns, especially those in which the stars orbit each other tightly, are much more likely to cast out asteroids, the researchers report today in the Monthly Notices of the Royal Astronomical Society. The team’s computer simulations suggest that up to 36% of binary stars can eject asteroids. When the researchers take into account the numbers of single-star versus binary systems and the numbers and sizes of planets they’re likely to have, they estimate that more than three-fourths of the asteroids cast into interstellar space come from solar systems that have two suns.

 

[BjarneModerator Super Nova]

The Excited Spin State of 1I/2017 U1 `Oumuamua

We show that Oumuamua’s excited spin could be in a high energy Long Axis Mode (LAM) state, which implies that its shape could be far from the highly elongated shape found in previous studies. CLEAN and ANOVA algorithms are used to analyze Oumuamua’s lightcurve using 818 observations over 29.3 days. Two fundamental periodicities are found at frequencies (2.77±0.11) and (6.42±0.18) cycles/day, corresponding to (8.67±0.34) h and (3.74±0.11) h, respectively. The phased data show that the lightcurve does not repeat in a simple manner, but approximately shows a double minimum at 2.77 cycles/day and a single minimum at 6.42 cycles/day. This is characteristic of an excited spin state. Oumuamua could be spinning in either the long (LAM) or short (SAM) axis mode. For both, the long axis precesses around the total angular momentum vector (TAMV) with an average period of (8.67±0.34) h. For the three LAMs we have found, the possible rotation periods around the long axis are 6.58, 13.15, or 54.48 h, with 54.48 h being the most likely. Oumuamua may also be nutating with respective periods of half of these values. We have also found two possible SAM states where Oumuamua oscillates around the long axis with possible periods at 13.15 and 54.48 h, the latter as the most likely. In this case any nutation will occur with the same periods. Determination of the spin state, the amplitude of the nutation, the direction of the TAMV, and the average total spin period may be possible with a direct model fit to the lightcurve. We find that Oumuamua is “cigar-shaped”, if close to its lowest rotational energy, and an extremely “oblate spheroid” if close to its highest energy state for its total angular momentum.

 

Jeg har i et andet indlæg i efteråret 2017 forklaret den generelle rotation af et stift legeme med 3 forskellige inertimomentakser. Denne nye undersøgelse viser, at det ikke er sikkert, at ‘Oumuamua er en lang cigar, som roterer omkring den korteste akse. Observationerne tillader også, at ‘Oumuamua er en flad oblat, som roterer om den længste akse.

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