The Great Recession, institutional dysfunction, a growing divide between urban and rural prospects, and failed efforts to effectively address immigration have paved the way for a populist backlash ...that disrupts the postwar bargain between political elites and citizens. Whether today's populism represents a corrective to unfair and obsolete policies or a threat to liberal democracy itself remains up for debate. Yet this much is clear: these challenges indict the triumphalism that accompanied liberal democratic consolidation after the collapse of the Soviet Union. To respond to today's crisis, good leaders must strive for inclusive economic growth while addressing fraught social and cultural issues, including demographic anxiety, with frank attention. Although reforms may stem the populist tide, liberal democratic life will always leave some citizens unsatisfied. This is a permanent source of vulnerability, but liberal democracy will endure so long as citizens believe it is worth fighting for.
We observed the newly discovered hyperbolic minor planet 1I/'Oumuamua (2017 U1) on 2017 October 30 with Lowell Observatory's 4.3 m Discovery Channel Telescope. From these observations, we derived a ...partial lightcurve with a peak-to-trough amplitude of at least 1.2 mag. This lightcurve segment rules out rotation periods less than 3 hr and suggests that the period is at least 5 hr. On the assumption that the variability is due to a changing cross-section, the axial ratio is at least 3:1. We saw no evidence for a coma or tail in either individual images or in a stacked image having an equivalent exposure time of 9000 s.
'Oumuamua (1I/2017 U1) is the first object of interstellar origin observed in the solar system. Recently, Micheli et al. reported that 'Oumuamua showed deviations from a Keplerian orbit at a high ...statistical significance. The observed trajectory is best explained by an excess radial acceleration Δa ∝ r−2, where r is the distance of 'Oumuamua from the Sun. Such an acceleration is naturally expected for comets, driven by the evaporating material. However, recent observational and theoretical studies imply that 'Oumuamua is not an active comet. We explore the possibility that the excess acceleration results from solar radiation pressure. The required mass-to-area ratio is (m/A) 0.1 g cm−2. For a thin sheet this requires a thickness of 0.3-0.9 mm. We find that although extremely thin, such an object would survive interstellar travel over Galactic distances of ∼5 kpc, withstanding collisions with gas and dust grains as well as stresses from rotation and tidal forces. We discuss the possible origins of such an object. Our general results apply to any light probes designed for interstellar travel.
We report on g-, r-, and i-band observations of the Interstellar Object 1I/'Oumuamua (1I) taken on 2017 October 29 from 04:28 to 08:40 UTC by the Apache Point Observatory (APO) 3.5 m telescope's ...ARCTIC camera. We find that 1I's colors are and , consistent with visible spectra and most comparable to the population of solar system C/D asteroids, Trojans, or comets. We find no evidence of any cometary activity at a heliocentric distance of 1.46 au, approximately 1.5 months after 1I's closest approach distance to the Sun. Significant brightness variability was seen in the r observations, with the object becoming notably brighter toward the end of the run. By combining our APO photometric time series data with the Discovery Channel Telescope data of Knight et al., taken 20 hr later on 2017 October 30, we construct an almost complete lightcurve with a most probable single-peaked lightcurve period of . Our results imply a double-peaked rotation period of 8.1 0.02 hr, with a peak-to-trough amplitude of 1.5-2.1 mag. Assuming that 1I's shape can be approximated by an ellipsoid, the amplitude constraint implies that 1I has an axial ratio of 3.5-10.3, which is strikingly elongated. Assuming that 1I is rotating above its critical break up limit, our results are compatible with 1I having modest cohesive strength and may have obtained its elongated shape during a tidal distortion event before being ejected from its home system.
The recent discovery by Pan-STARRS1 of 1I/2017 U1 ('Oumuamua), on an unbound and hyperbolic orbit, offers a rare opportunity to explore the planetary formation processes of other stars and the effect ...of the interstellar environment on a planetesimal surface. 1I/'Oumuamua's close encounter with the inner solar system in 2017 October was a unique chance to make observations matching those used to characterize the small-body populations of our own solar system. We present near-simultaneous g′, r′, and J photometry and colors of 1I/'Oumuamua from the 8.1 m Frederick C. Gillett Gemini-North Telescope and gri photometry from the 4.2 m William Herschel Telescope. Our g′r′J observations are directly comparable to those from the high-precision Colours of the Outer Solar System Origins Survey (Col-OSSOS), which offer unique diagnostic information for distinguishing between outer solar system surfaces. The J-band data also provide the highest signal-to-noise measurements made of 1I/'Oumuamua in the near-infrared. Substantial, correlated near-infrared and optical variability is present, with the same trend in both near-infrared and optical. Our observations are consistent with 1I/'Oumuamua rotating with a double-peaked period of 8.10 0.42 hr and being a highly elongated body with an axial ratio of at least 5.3:1, implying that it has significant internal cohesion. The color of the first interstellar planetesimal is at the neutral end of the range of solar system g − r and r − J solar-reflectance colors: it is like that of some dynamically excited objects in the Kuiper Belt and the less-red Jupiter Trojans.
We present observations of the interstellar interloper 1I/2017 U1 ('Oumuamua) taken during its 2017 October flyby of Earth. The optical colors B - V = 0.70 0.06, V - R = 0.45 0.05, overlap those of ...the D-type Jovian Trojan asteroids and are incompatible with the ultrared objects that are abundant in the Kuiper Belt. With a mean absolute magnitude HV = 22.95 and assuming a geometric albedo pV = 0.1, we find an average radius of 55 m. No coma is apparent; we deduce a limit to the dust mass production rate of only ∼2 × 10−4 kg s−1, ruling out the existence of exposed ice covering more than a few m2 of the surface. Volatiles in this body, if they exist, must lie beneath an involatile surface mantle 0.5 m thick, perhaps a product of prolonged cosmic-ray processing in the interstellar medium. The light curve range is unusually large at ∼2.0 0.2 mag. Interpreted as a rotational light curve the body has axis ratio :1 and semi-axes ∼230 m × 35 m. A 6:1 axis ratio is extreme relative to most small solar system asteroids and suggests that albedo variations may additionally contribute to the variability. The light curve is consistent with a two-peaked period ∼8.26 hr, but the period is non-unique as a result of aliasing in the data. Except for its unusually elongated shape, 1I/2017 U1 is a physically unremarkable, sub-kilometer, slightly red, rotating object from another planetary system. The steady-state population of similar, ∼100 m scale interstellar objects inside the orbit of Neptune is ∼104, each with a residence time of ∼10 years.
1I/2017 U1 ('Oumuamua), a recently discovered asteroid in a hyperbolic orbit, is likely the first macroscopic object of extrasolar origin identified in the solar system. Here, we present imaging and ...spectroscopic observations of 'Oumuamua using the Palomar Hale Telescope as well as a search of meteor activity potentially linked to this object using the Canadian Meteor Orbit Radar. We find that 'Oumuamua exhibits a moderate spectral gradient of , a value significantly lower than that of outer solar system bodies, indicative of a formation and/or previous residence in a warmer environment. Imaging observation and spectral line analysis show no evidence that 'Oumuamua is presently active. Negative meteor observation is as expected, since ejection driven by sublimation of commonly known cometary species such as CO requires an extreme ejection speed of ∼40 m s−1 at ∼100 au in order to reach the Earth. No obvious candidate stars are proposed as the point of origin for 'Oumuamua. Given a mean free path of ∼109 ly in the solar neighborhood, 'Oumuamua has likely spent a very long time in interstellar space before encountering the solar system.
This paper provides evidence of a novel facet of peer effects by showing that peer personality influences academic achievement. We exploit random assignment of students to university sections and ...find that students perform better in the presence of persistent peers. The impact of peer persistence is enduring, as students exposed to persistent peers at the beginning of their studies continue to achieve higher grades in subsequent periods. The personality peer effects that we document are distinct from other observable peer characteristics and suggest that peer personality traits affect human capital accumulation.
Currently, a large number of industrial robots have been deployed to replace or assist humans to perform various repetitive and dangerous manufacturing tasks. However, based on current technological ...capabilities, such robotics field is rapidly evolving so that humans are not only sharing the same workspace with robots, but also are using robots as useful assistants. Consequently, due to this new type of emerging robotic systems, industrial collaborative robots or cobots, human and robot co-workers have been able to work side-by-side as collaborators to accomplish tasks in industrial environments. Therefore, new human-robot interaction systems have been developed for such systems to be able to utilize the capabilities of both humans and robots. Accordingly, this article presents a literature review of major recent works on human-robot interactions in industrial collaborative robots, conducted during the last decade (between 2008 and 2017). Additionally, the article proposes a tentative classification of the content of these works into several categories and sub-categories. Finally, this paper addresses some challenges of industrial collaborative robotics and explores future research issues.
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