APO Time-resolved Color Photometry of Highly Elongated Interstellar Object 1I/‘Oumuamua

Bolin, Bryce; Weaver, H. A.; Fernández, Y. R.; Lisse, C. M.; Huppenkothen, Daniela; Jones, Lynne; Jurić, Mario; Moeyens, Joachim; Schambeau, Charles; Slater, Colin T.; Ivezić, Željko; Connolly, Andrew J.

doi:10.3847/2041-8213/aaa0c9

Cited by 116 publications

(116 citation statements)

References 79 publications

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“…We note that the last pair of Gemini observations implies an excursion from our light curve model; the data are entirely reliable, given the consistent stability of the observing conditions and the calibrations and from careful inspection of the images. Our results using only our Gemini and WHT photometry with that from the DCT are independently in agreement with those of Bolin et al (2017), which used photometry from the 3.5 m Apache Point Observatory and the DCT photometry.…”

Section: Variability and Shape Of 1i/'oumuamuasupporting

confidence: 80%

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

Bannister¹,

Schwamb

Fraser³

et al. 2017

ApJL

117

100

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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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Section: Variability and Shape Of 1i/'oumuamuasupporting

confidence: 80%

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

Bannister¹,

Schwamb

Fraser³

et al. 2017

ApJL

117

100

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“…≤130 m (Bolin et al 2018). For the sake of argument, we take r O = 0.1 km as the effective radius of 'Oumuamua.…”

Section: Statistics Of Interstellar Objectsmentioning

confidence: 99%

Initial Characterization of Interstellar Comet 2I/2019 Q4 (Borisov)

Jewitt

Luu

2019

ApJL

111

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We present initial observations of the interstellar body 2I/(2019 Q4) Borisov taken to determine its nature prior to the perihelion in 2019 December. Images from the Nordic Optical Telescope show a prominent, morphologically stable dust coma and tail. The dust cross-section within 15,000 km of the nucleus averages 130 km 2 (assuming geometric albedo 0.1) and increases by about 1% per day.If sustained, this rate indicates that the comet has been active for ∼100 days prior to the observations. Cometary activity thus started in 2019 June, at which time C/Borisov was at ∼4.5 AU from the Sun, a typical distance for the onset of water ice sublimation in comets. The dust optical colors, B-V = 0.80±0.05, V-R = 0.47±0.03 and R-I = 0.49±0.05 are identical to those of a sample of (solar system) long-period comets. The colors are similar to those of 1I/(2017 U1) 'Oumuamua, indicating a lack of the ultrared matter that is common in the Kuiper belt, on both interstellar objects. The effective size of the dust particles is estimated as a = 100 µm, based on the length of the dust tail and the 100 day lifetime. With this size, the ejected dust mass is of order 1.3×10 7 kg and the current dust mass loss rate ∼ 2 kg s −1 . We set an upper limit to the nucleus radius using photometry at r n ≤ 3.8 km (again for albedo 0.1) and we use a statistical argument to show that the nucleus must be much smaller, likely a few hundred meters in radius.

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“…The first known interstellar object 1I/'Oumuamua was discovered by the Pan-STARRS telescope in October 2017, and after a short and intense observational campaign, it left behind far more questions than answers. Ground-based observations (Bannister et al (2017), Jewitt et al (2017), Meech et al (2017), Bolin et al (2017), Drahus et al (2018), Fraser et al (2018), Knight et al (2017)) generally agreed on the following: 1) effective radius: 50 -130 m, 2) axis ratio: 6:1, and 3) a rotation period 6.8 -8.7hr. However, the fact that Oumuamua could not be observed in the infrared spectrum (see Trilling et al (2018)) introduces a significant uncertainty in its albedo, and hence its size.…”

Section: Introductionmentioning

confidence: 91%

The Interstellar Object ’Oumuamua as a Fractal Dust Aggregate

Flekkøy

Luu

Toussaint

2019

ApJL

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The first known interstellar object 'Oumuamua exhibited a nongravitational acceleration that appeared inconsistent with cometary outgassing, leaving radiation pressure as the most likely force. Bar the alien lightsail hypothesis, an ultra-low density due to a fractal structure might also explain the acceleration of 'Oumuamua by radiation pressure (Moro-Martin 2019). In this paper we report a decrease in 'Oumuamua's rotation period based on ground-based observations, and show that this spin-down can be explained by the YORP effect if 'Oumuamua is indeed a fractal body with the ultra-low density of 10 −2 kg m −3 . We also investigate the mechanical consequences of 'Oumuamua as a fractal body subjected to rotational and tidal forces, and show that a fractal structure can survive these mechanical forces.

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APO Time-resolved Color Photometry of Highly Elongated Interstellar Object 1I/‘Oumuamua

Cited by 116 publications

References 79 publications

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

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

Initial Characterization of Interstellar Comet 2I/2019 Q4 (Borisov)

The Interstellar Object ’Oumuamua as a Fractal Dust Aggregate

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