Author Topic: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)  (Read 71696 times)

Online Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #300 on: 12/22/2017 01:05 AM »
Prospects for Backtracing 1I/`Oumuamua and Future Interstellar Objects

1I/`Oumuamua is the first of likely many small bodies of extrasolar origin to be found in the solar system. These interstellar objects (ISOs) are hypothesized to have formed in extrasolar planetary systems prior to being ejected into interstellar space and subsequently arriving at the solar system. This paper discusses necessary considerations for tracing ISOs back to their parent stars via trajectory analysis, and places approximate limits on doing so. Results indicate the capability to backtrace ISOs beyond the immediate solar neighborhood is presently constrained by the quality of stellar astrometry, a factor poised for significant improvement with upcoming Gaia data releases. Nonetheless, prospects for linking 1I or any other ISO to their respective parent star appear unfavorable on an individual basis due to gravitational scattering from random stellar encounters which limit traceability to the past few tens of millions of years. These results, however, do not preclude the possibility of occasional success, particularly after considering the potential for observational bias favoring the discovery of younger ISOs, together with the anticipated rise in the ISO discovery rate under forthcoming surveys.

Online Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #301 on: 01/10/2018 12:50 AM »
1I/2017 'Oumuamua-like Interstellar Asteroids as Possible Messengers from the Dead Stars

Discovery of the first interstellar asteroid (ISA) - 1I/2017 'Oumuamua - raised a number of questions regarding its origin. Many of them relate to its lack of cometary activity, suggesting refractory composition of 'Oumuamua. Here we explore the possibility that 'Oumuamua-like ISAs are produced in tidal disruption events (TDEs) of refractory planetoids (asteroids, dwarf planets, etc.) by the white dwarfs (WDs). This idea is supported by existing spectroscopic observations of metal-polluted WDs, hinting at predominantly volatile-poor composition of accreted material. We show that such TDEs sourced by realistic planetary systems (including a population of >1000 km planetoids and massive perturbers - Neptune-to-Saturn mass planets) can eject to interstellar space up to 30% of planetary mass involved in them. Collisional fragmentation, caused by convergent vertical motion of the disrupted planetoid's debris inside the Roche sphere of the WD, channels most of the original mass into 0.1-1 km fragments, similar to 'Oumuamua. Such size spectrum of ISAs (very different from the top-heavy distributions expected in other scenarios) implies that every WD needs to eject ~0.3M_E of refractory material through TDEs (for ISA albedo of 0.2). This figure is consistent with the existing observations of WD metal pollution once we account for observational biases by using realistic models of circum-WD planetary systems. ISAs should exhibit kinematic characteristics similar to old, dynamically hot Galactic populations; we interpret 'Oumuamua's slow Galactic motion as a statistical fluctuation. ISA ejection in individual planetary TDEs is highly anisotropic, resulting in large fluctuations of their space density. We also show that other ISA production mechanisms involving stellar remnants - direct ejection by massive planets around WDs and SN explosions - have difficulty explaining 'Oumuamua-like ISAs.

Interstellar Interlopers: Number Density and Origins of 'Oumuamua-like Objects

We provide a calculation of Pan-STARRS' ability to detect objects similar to the interstellar object 1I/2017 U1 (hereafter 'Oumuamua), including the most detectable approach vectors and the effect of object size on detection efficiency. Using our updated detection cross-section, we infer an interstellar number density of such objects (nIS≈0.2 au−3). This translates to a mass density of ρIS≈4M⊕ pc−3 which cannot be populated unless every star is contributing. We find that given current models, such a number density cannot arise from the ejection of inner solar system material during planet formation. We note that a stellar system's Oort cloud will be released after a star's main sequence life time and may provide enough material to obtain the observed density. The challenge is that Oort cloud bodies are icy and \OBJECT was observed to be dry which necessitates a crust generation mechanism.

Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #302 on: 01/10/2018 02:08 AM »
Breakthrough Listen Observations of Breakthrough Listen with the GBT (typo in original , they meant 'Oumuamua :o)

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We have conducted a search for radio emission consistent with an artificial source targeting 1I/'Oumuamua with the Robert C. Byrd Green Bank Telescope (GBT) between 1.1 and 11.6 GHz. We searched the data for narrow band signals and found none. Given the close proximity to this interstellar object, we can place limits to putative transmitters with extremely low power (0.08 W).
« Last Edit: 01/10/2018 02:09 AM by hop »

Offline Star One

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #303 on: 01/19/2018 08:38 PM »
Update on an Interstellar Asteroid

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What’s the news coming from the research world on the interstellar asteroid visitor, asteroid 1I/’Oumuamua? Read on for an update from a few of the latest studies.

http://aasnova.org/2018/01/19/update-on-an-interstellar-asteroid/

Offline hop

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #304 on: 01/25/2018 05:22 PM »
‘Oumuamua talks by Meg Schwamb and Matija Cuk at the SETI institute, Jan 23



Nothing really new for those who have followed the preprints, but a good overview.

Online speedevil

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #305 on: 01/28/2018 05:52 AM »
Has there been any work done on estimating if any of the prior surveys for asteroids/... may have caught these optically, and not picked them up due to searching only for bound bodies to improve performance?

Online Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #306 on: 02/05/2018 12:38 AM »
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.

Online Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #307 on: 02/06/2018 12:45 AM »
Spinup and Disruption of Interstellar Asteroids by Mechanical Torques, and Implications for 1I/2017 U1 (`Oumuamua)

The detection of the first interstellar asteroid, 1I/2017 U1 (`Oumuamua), has opened a new era for research on interstellar objects. In this paper, we study the rotational dynamics of interstellar asteroids (ISAs) of irregular shapes moving through the interstellar gas. We find that regular mechanical torques resulting from the bombardment of gas flow on the irregular body could be important for the dynamics and destruction of ISAs. Mechanical torques can spin up the ISA, resulting in the breakup of the original ISA into small binary asteroids when the rotation rate exceeds the critical limit determined by material strength. We find that the breakup timescale is short for ISAs of highly irregular shapes and low tensile strength. We apply our results to the first observed ISA, `Oumuamua, and suggest that its extreme elongated shape may originate from a re-assembly of the binary fragments due to gravity along its journey in the interstellar medium. The tumbling of `Oumuamua could have been induced by rotational disruption due to mechanical torques. Finally, we discuss the survival possibility of high-velocity asteroids presumably formed by tidal disruption of planetary systems by the black hole at the Galactic center.

Online Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #308 on: 02/08/2018 01:26 AM »
Why is Interstellar Object 1I/2017 U1 (`Oumuamua) Rocky, Tumbling and Very Prolate?

The recently discovered first interstellar object 1I/2017 U1 (`Oumuamua) has brightness that varies by a factor of 10, a range greater than that of any Solar System asteroid, a spectrum characteristic of Type D asteroids, and no evidence of evaporating volatiles, contrary to expectation for exo-Oort clouds. This object was the first example of the proposed "Jurads", objects depleted in volatiles and ejected from planetary systems during the post-main sequence evolution of their parent star. I suggest that heating by the star's giant stage fluidized a precursor cometary object as volatiles escaped, causing it to assume the Jacobi ellipsoidal shape of a self-gravitating incompressible liquid. The collision that produced the inferred tumbling motion must have occurred thousands of years after the formation of 1I/2017 U1 `Oumuamua. Jacobi ellipsoids have a unique relation among rotation rate, density and axial ratio. The inferred axial ratio ⪆5 implies a lower bound on the density of 1.6 g/cm3, excluding an icy interior unless it is almost entirely frozen CO2. This object is the first Jurad to be discovered and may be related to accreting objects that pollute white dwarf atmospheres and may make Soft Gamma Repeaters.

Offline Star One

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #309 on: 02/11/2018 08:28 AM »
For UK forum members tonight’s Sky At Night is all about Oumuamua.

Feature article.

http://www.bbc.co.uk/news/science-environment-43018706

Episode link.

http://www.bbc.co.uk/programmes/b09rvpts

Offline plutogno

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #310 on: 02/11/2018 07:33 PM »
The tumbling rotational state of 1I/‘Oumuamua

https://www.nature.com/articles/s41550-018-0398-z

Offline Star One

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Online Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #312 on: 02/27/2018 01:02 AM »
A Serendipitous MWA Search for Narrow-band and Broad-band Low Frequency Radio Transmissions from 1I/2017 U1 'Oumuamua

We examine data from the Murchison Widefield Array (MWA) in the frequency range 72 -- 102 MHz for a field-of-view that serendipitously contained the interstellar object 'Oumuamua on 2017 November 28. Observations took place with time resolution of 0.5 s and frequency resolution of 10 kHz. %This observation was undertaken for another purpose but due to the MWA's extremely large field-of-view, 'Oumuamua was serendipitously observed simultaneously. Based on the interesting but highly unlikely suggestion that 'Oumuamua is an interstellar spacecraft, due to some unusual orbital and morphological characteristics, we examine our data for signals that might indicate the presence of intelligent life associated with 'Oumuamua. We searched our radio data for: 1) impulsive narrow-band signals; 2) persistent narrow-band signals; and 3) impulsive broadband signals. We found no such signals with non-terrestrial origins and make estimates of the upper limits on Equivalent Isotropic Radiated Power (EIRP) for these three cases of approximately 7 kW, 840 W, and 100 kW, respectively. These transmitter powers are well within the capabilities of human technologies, and are therefore plausible for alien civilizations. While the chances of positive detection in any given Search for Extraterrestrial Intelligence (SETI) experiment are vanishingly small, the characteristics of new generation telescopes such as the MWA (and in the future, the Square Kilometre Array) make certain classes of SETI experiment easy, or even a trivial by-product of astrophysical observations. This means that the future costs of SETI experiments are very low, allowing large target lists to partially balance the low probability of a positive detection.

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #313 on: 03/09/2018 01:03 AM »
Interstellar object 'Oumuamua as an extinct fragment of an ejected cometary planetesimal

'Oumuamua was discovered passing through our Solar System on a hyperbolic orbit. It presents an apparent contradiction, with colors similar to those of volatile-rich Solar System bodies but with no visible outgassing or activity during its close approach to the Sun. Here we show that this contradiction can be explained by the dynamics of planetesimal ejection by giant planets. We propose that 'Oumuamua is an extinct fragment of a comet-like planetesimal born in a planet-forming disk that also formed Neptune- to Jupiter-mass giant planets. On its pathway to ejection 'Oumuamua's parent body underwent a close encounter with a giant planet and was tidally disrupted into small pieces, similar to comet Shoemaker-Levy 9's disruption after passing close to Jupiter. We use dynamical simulations to show that 0.1-1% of cometary planetesimals undergo disruptive encounters prior to ejection. Rocky asteroidal planetesimals are unlikely to disrupt due to their higher densities. After disruption, the bulk of fragments undergo enough close passages to their host stars to lose their surface volatiles and become extinct. Planetesimal fragments such as 'Oumuamua contain little of the mass in the population of interstellar objects but dominate by number. Our model makes predictions that will be tested in the coming decade by LSST.

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #314 on: 03/19/2018 08:22 PM »
NEWS & PRESS

‘Oumuamua likely came from a binary star system

Last Updated on Monday, 19 March 2018 11:52
Published on Monday, 19 March 2018 11:52
New research finds that 'Oumuamua, the rocky object identified as the first confirmed interstellar asteroid, very likely came from a binary star system.
 
"It's remarkable that we've now seen for the first time a physical object from outside our Solar System," says lead author Dr Alan Jackson, a postdoc at the Centre for Planetary Sciences at the University of Toronto Scarborough in Ontario, Canada.
 
A binary star system, unlike our Sun, is one with two stars orbiting a common centre.
 
For the new study, published in the journal Monthly Notices of the Royal Astronomical Society, Jackson and his co-authors set about testing how efficient binary star systems are at ejecting objects. They also looked at how common these star systems are in the Galaxy.
 
They found that rocky objects like 'Oumuamua are far more likely to come from binary than single star systems. They were also able to determine that rocky objects are ejected from binary systems in comparable numbers to icy objects.
 
"It's really odd that the first object we would see from outside our system would be an asteroid, because a comet would be a lot easier to spot and the Solar System ejects many more comets than asteroids," says Jackson, who specializes in planet and solar system formation.
 
Once they determined that binary systems are very efficient at ejecting rocky objects, and that a sufficient number of them exist, they were satisfied that 'Oumuamua very likely came from a binary system. They also concluded that it probably came from a system with a relatively hot, high mass star since such a system would have a greater number of rocky objects closer in.
 
The team suggest that the asteroid was very likely to have been ejected from its binary system sometime during the formation of planets.
 
'Oumuamua, which is Hawaiian for 'scout', was first spotted by the Haleakala Observatory in Hawaii on 19 October 2017. With a radius of 200 metres and travelling at a blistering speed of 30 kilometres per second, at its closest it was about 33,000,000 km from Earth.
 
When it was first discovered researchers initially assumed the object was a comet, one of countless icy objects that release gas when they warm up on approaching the Sun. But it didn't show any comet-like activity as it neared the Sun, and was quickly reclassified as an asteroid, meaning it was rocky.
 
Researchers were also fairly sure it was from outside our Solar System, based on its trajectory and speed. An eccentricity of 1.2 – which classifies its path as an open-ended hyperbolic orbit – and such a high speed meant it was not bound by the gravity of the Sun.
 
In fact, as Jackson points out, 'Oumuamua's orbit has the highest eccentricity ever observed in an object passing through our Solar System.
 
Major questions about ‘Oumuamua remain. For planetary scientists like Jackson, being able to observe objects like these may yield important clues about how planet formation works in other star systems.
 
“The same way we use comets to better understand planet formation in our own Solar System, maybe this curious object can tell us more about how planets form in other systems.”
 

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #315 on: 03/20/2018 01:06 AM »
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.

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #316 on: 03/28/2018 01:53 AM »
Constraints on the Density and Internal Strength of 1I/'Oumuamua

1I/'Oumuamua was discovered by the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS 1) on 19 October 2017. Unlike all previously discovered minor planets this object was determined to have eccentricity e>1.0, suggesting an interstellar origin. Since this discovery and within the limited window of opportunity, several photometric and spectroscopic studies of the object have been made. Using the measured light curve amplitudes and rotation periods we find that, under the assumption of a triaxial ellipsoid, a density range 1500<ρ<2800 kg m−3 matches the observations and no significant cohesive strength is required. We also determine that an aspect ratio of 6±1:1 is most likely after accounting for phase-angle effects and considering the potential effect of surface properties. This elongation is still remarkable but less than some other estimates.

Search for OH 18-cm radio emission from 1I/2017 U1 with the Green Bank telescope

This paper reports the first OH 18-cm line observation of the first detected interstellar object 1I/2017 U1 (`Oumuamua) using the Green Bank Telescope. We have observed the OH lines at 1665.402 MHz, 1667.359, and 1720.53 MHz frequencies with a spectral resolution of 357 Hz (approximately 0.06 km-s^{-1}). At the time of the observation, `Oumuamua was at topocentric distance and velocity of 1.07 au and 63.4 km-s^{-1}, respectively, or at heliocentric distance and velocity of 1.8 au and 39 km-s^{-1}, respectively. Based on a detailed data reduction and an analogy-based inversion, our final results confirm the asteroidal origin of `Oumuamua (as discussed in Meech et al., 2017) with an upper bound of OH production of Q[OH] < 0.17 x 10^{28} s^{-1}.

Online Mongo62

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #317 on: 04/11/2018 01:26 AM »
The Excited Spin State of 1I/2017 U1 `Oumuamua

We show that `Oumuamua's excited spin could be in a high energy 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 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.

Offline plutogno

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Re: Hyperbolic Hyperbole or Interstellar Interloper? ('Oumuamua)
« Reply #318 on: 06/27/2018 06:29 PM »
Interstellar asteroid is really a comet
http://sci.esa.int/solar-system/60464-interstellar-asteroid-is-really-a-comet/

and related (paywalled) Nature paper
Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua)
https://www.nature.com/articles/s41586-018-0254-4

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