An Observational Upper Limit on the Interstellar Number Density of Asteroids and Comets

Engelhardt, T.; Jedicke, Robert; Vereš, Peter; Fitzsimmons, A.; Denneau, L.; Beshore, E.; Meinke, B. K.

doi:10.3847/1538-3881/aa5c8a

Cited by 147 publications

(138 citation statements)

References 49 publications

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“…Most moving objects detected by LSST will be "unremarkable" asteroids in the main belt, but this very large and deep survey (20,000 deg 2 surveyed to r magnitude 24.5 repeatedly over ten years) naturally has the possibility to discover unusual objects in all areas of astrophysics. Several authors have studied the detectability of interstellar interlopers in LSST data (Moro-Martín et al 2009;Cook et al 2016;Engelhardt et al 2017).…”

Section: Discussionmentioning

confidence: 99%

“…The theoretical existence of ejectoids has been long proposed (e.g., Sekanina 1976), with various authors using non-detections to place upper limits on the population (McGlynn & Chapman 1989;Sen & Rama 1993;Engelhardt et al 2017). Jewitt (2003) and Francis (2005) suggested that PanSTARRS could detect an interstellar object, if the number density was great enough.…”

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confidence: 99%

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Implications for Planetary System Formation from Interstellar Object 1I/2017 U1 (‘Oumuamua)

Trilling

Robinson

Roegge

et al. 2017

ApJL

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The recently discovered minor body 1I/2017 U1 ('Oumuamua) is the first known object in our Solar System that is not bound by the Sun's gravity. Its hyperbolic orbit (eccentricity greater than unity) strongly suggests that it originated outside our Solar System; its red color is consistent with substantial space weathering experienced over a long interstellar journey. We carry out an simple calculation of the probability of detecting such an object. We find that the observed detection rate of 1I-like objects can be satisfied if the average mass of ejected material from nearby stars during the process of planetary formation is ∼20 Earth masses, similar to the expected value for our Solar System. The current detection rate of such interstellar interlopers is estimated to be 0.2/year, and the expected number of detections over the past few years is almost exactly one. When the Large Synoptic Survey Telescope begins its wide, fast, deep all-sky survey the detection rate will increase to 1/year. Those expected detections will provide further constraints on nearby planetary system formation through a better estimate of the number and properties of interstellar objects.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Implications for Planetary System Formation from Interstellar Object 1I/2017 U1 (‘Oumuamua)

Trilling

Robinson

Roegge

et al. 2017

ApJL

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“…Next generation time-domain sky surveys, such as the Large Synoptic Sky Survey (Tyson 2002), will provide deeper coverage over wider areas, hopefully revealing more objects like 'Oumuamua (Cook et al 2016;Engelhardt et al 2017). This will provide better estimates of the number density and size distribution of interstellar objects which are presently poorly constrained.…”

Section: <´-( )mentioning

confidence: 99%

1I/2017 U1 (‘Oumuamua) is Hot: Imaging, Spectroscopy, and Search of Meteor Activity

Zhang

Kelley

et al. 2017

ApJL

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Abstract1I/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 10% 6% 100 nm 1  -( ) , 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 ∼10 9 ly in the solar neighborhood, 'Oumuamua has likely spent a very long time in interstellar space before encountering the solar system.

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“…In 19 years of digital-camera all-sky surveying, it is the first definitively interstellar, decameter-scale object to be found. The earlier lack of detections has implied a low density of interstellar planetesimals (Francis 2005;Cook et al 2016;Engelhardt et al 2017). Several Earth masses of ejected bodies are expected per star during planetary formation and migration (e.g., Levison et al 2010;Barclay et al 2017).…”

Section: Introductionmentioning

confidence: 99%

Col-OSSOS: Colors of the Interstellar Planetesimal 1I/‘Oumuamua

Bannister¹,

Schwamb

Fraser³

et al. 2017

ApJL

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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.

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An Observational Upper Limit on the Interstellar Number Density of Asteroids and Comets

Cited by 147 publications

References 49 publications

Implications for Planetary System Formation from Interstellar Object 1I/2017 U1 (‘Oumuamua)

Implications for Planetary System Formation from Interstellar Object 1I/2017 U1 (‘Oumuamua)

1I/2017 U1 (‘Oumuamua) is Hot: Imaging, Spectroscopy, and Search of Meteor Activity

Col-OSSOS: Colors of the Interstellar Planetesimal 1I/‘Oumuamua

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