Spitzer Observations of Interstellar Object 1I/‘Oumuamua

1I/'Oumuamua is the first confirmed interstellar body in our solar system. Here we report on observations of 'Oumuamua made with the Spitzer Space Telescope on 2017 November 21–22 (UT). We integrated for 30.2 hr at 4.5 μm (IRAC channel 2). We did not detect the object and place an upper limit on the flux of 0.3 μJy (3σ). This implies an effective spherical diameter less than [98, 140, 440] m and albedo greater than [0.2, 0.1, 0.01] under the assumption of low, middle, or high thermal beaming parameter η, respectively. With an aspect ratio for 'Oumuamua of 6:1, these results correspond to dimensions of [240:40, 341:57, 1080:180] m, respectively. We place upper limits on the amount of dust, CO, and CO2 coming from this object that are lower than previous results; we are unable to constrain the production of other gas species. Both our size and outgassing limits are important because 'Oumuamua's trajectory shows non-gravitational accelerations that are sensitive to size and mass and presumably caused by gas emission. We suggest that 'Oumuamua may have experienced low-level post-perihelion volatile emission that produced a fresh, bright, icy mantle. This model is consistent with the expected η value and implied high-albedo value for this solution, but, given our strict limits on CO and CO_2, requires another gas species—probably H_2O—to explain the observed non-gravitational acceleration. Our results extend the mystery of 'Oumuamua's origin and evolution.

[1]  Robert Jedicke,et al.  Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U1 ‘Oumuamua , 2017, Nature Astronomy.

[2]  C. Chen,et al.  Infrared Spectroscopy of HR 4796A's Bright Outer Cometary Ring + Tenuous Inner Hot Dust Cloud , 2017, 1708.02834.

[3]  R. Marschall,et al.  Water vapor deposition from the inner gas coma onto the nucleus of Comet 67P/Churyumov-Gerasimenko , 2018, Planetary and Space Science.

[4]  Robert Jedicke,et al.  An Investigation of the Ranges of Validity of Asteroid Thermal Models for Near-Earth Asteroid Observations , 2018, 1801.03628.

[5]  M. Belton,et al.  Rotationally Resolved 8-35 Micron Spitzer Space Telescope Observations of the Nucleus of Comet 9P/Tempel 1 , 2005 .

[6]  Lori M. Feaga,et al.  On the Rotation Period and Shape of the Hyperbolic Asteroid 1I/‘Oumuamua (2017 U1) from Its Lightcurve , 2017, 1711.01402.

[7]  E. Grün,et al.  A tale of two very different comets: ISO and MSX measurements of dust emission from 126P/IRAS (1996) and 2P/Encke (1997) , 2004 .

[8]  Alan W. Harris,et al.  A Thermal Model for Near-Earth Asteroids , 1998 .

[9]  Sebastian Kurowski,et al.  Tumbling motion of 1I/‘Oumuamua and its implications for the body’s distant past , 2018, Nature Astronomy.

[10]  Karen J. Meech,et al.  The NEOWISE-Discovered Comet Population and the CO+CO2 production rates , 2015 .

[11]  Ralf Kotulla,et al.  Interstellar Interloper 1I/2017 U1: Observations from the NOT and WIYN Telescopes , 2017, 1711.05687.

[12]  Robert L. Millis,et al.  The ensemble properties of comets: Results from narrowband photometry of 85 comets , 1995 .

[13]  Hans Rickman,et al.  Origin and Evolution of the Cometary Reservoirs , 2014 .

[14]  M. C. Wyatt,et al.  On the Nature of the Dust in the Debris Disk around HD 69830 , 2006, astro-ph/0611452.

[15]  Larry Denneau,et al.  A brief visit from a red and extremely elongated interstellar asteroid , 2017, Nature.

[16]  Sean N. Raymond,et al.  Interstellar Object ’Oumuamua as an Extinct Fragment of an Ejected Cometary Planetesimal , 2018, 1803.02840.

[17]  Davide Farnocchia,et al.  Non-gravitational acceleration in the trajectory of 1I/2017 U1 (‘Oumuamua) , 2018, Nature.

[18]  David E. Trilling,et al.  Implications for Planetary System Formation from Interstellar Object 1I/2017 U1 (‘Oumuamua) , 2017, 1711.01344.

[19]  Munetaka Ueno,et al.  AKARI NEAR-INFRARED SPECTROSCOPIC SURVEY FOR CO2 IN 18 COMETS , 2012 .

[20]  S. Debei,et al.  Seasonal mass transfer on the nucleus of comet 67P/Chuyumov–Gerasimenko , 2017, 1707.06812.

[21]  Michael Mommert,et al.  Constraints on the Density and Internal Strength of 1I/’Oumuamua , 2018, 1803.09864.

[22]  Giacomo Tommei,et al.  Multiple solutions for asteroid orbits: Computational procedure and applications , 2005 .

[23]  Simon Portegies Zwart,et al.  The origin of interstellar asteroidal objects like 1I/2017 U1 , 2017, 1711.03558.

[24]  Fabo Feng,et al.  ‘Oumuamua as a Messenger from the Local Association , 2017, 1711.08800.

[25]  D. Trilling,et al.  THE DISCOVERY OF COMETARY ACTIVITY IN NEAR-EARTH ASTEROID (3552) DON QUIXOTE , 2013, The Astrophysical Journal.

[26]  J. Licandro,et al.  Thermal properties, sizes, and size distribution of Jupiter-family cometary nuclei , 2013, 1307.6191.

[27]  Andrew J. Connolly,et al.  APO Time-resolved Color Photometry of Highly Elongated Interstellar Object 1I/‘Oumuamua , 2017, 1711.04927.

[28]  Michael Marsset,et al.  Col-OSSOS: Colors of the Interstellar Planetesimal 1I/‘Oumuamua , 2017, 1711.06214.

[29]  G. Fazio,et al.  PHYSICAL PROPERTIES OF NEAR-EARTH ASTEROID 2011 MD , 2014, 1406.5253.

[30]  Massimo Marengo,et al.  IRACproc: a software suite for processing and analyzing Spitzer/IRAC data , 2006, SPIE Astronomical Telescopes + Instrumentation.

[31]  Mohamad Ali-Dib,et al.  Ejection of rocky and icy material from binary star systems: implications for the origin and composition of 1I/‘Oumuamua , 2017, 1712.04435.

[32]  Spitzer Space Telescope Observations of the Nucleus of Comet 103P/Hartley 2 , 2009, 0906.4733.

[33]  Michael Mommert,et al.  NEOSURVEY 1: INITIAL RESULTS FROM THE WARM SPITZER EXPLORATION SCIENCE SURVEY OF NEAR-EARTH OBJECT PROPERTIES , 2016, 1608.03673.

[34]  Aaron Do,et al.  Interstellar Interlopers: Number Density and Origin of ‘Oumuamua-like Objects , 2018, 1801.02821.

[35]  Sebastian Kurowski,et al.  The Excited Spin State of 1I/2017 U1 ‘Oumuamua , 2018, 1804.03471.

[36]  Nathan Myhrvold,et al.  Comparing NEO Search Telescopes , 2015 .

[37]  Eric Gaidos,et al.  What and whence 1I/`Oumuamua: a contact binary from the debris of a young planetary system? , 2017, 1712.06721.

[38]  Samuel H. Moseley,et al.  Infrared Observations of Comets by COBE , 1998 .

[39]  M. Ćuk,et al.  1I/‘Oumuamua as a Tidal Disruption Fragment from a Binary Star System , 2017, 1712.01823.

[40]  G. Fazio,et al.  The Infrared Array Camera (IRAC) for the Spitzer Space Telescope , 2004, astro-ph/0405616.

[41]  Qicheng Zhang,et al.  1I/2017 U1 (‘Oumuamua) is Hot: Imaging, Spectroscopy, and Search of Meteor Activity , 2017, 1711.02320.

[42]  David Makovoz,et al.  MOPEX: a software package for astronomical image processing and visualization , 2006, SPIE Astronomical Telescopes + Instrumentation.

[43]  D. Trilling,et al.  ExploreNEOs. II. THE ACCURACY OF THE WARM SPITZER NEAR-EARTH OBJECT SURVEY , 2010 .

[44]  Michael Mommert,et al.  ExploreNEOs. III. PHYSICAL CHARACTERIZATION OF 65 POTENTIAL SPACECRAFT TARGET ASTEROIDS , 2011 .

[45]  D. Trilling,et al.  CONSTRAINING THE PHYSICAL PROPERTIES OF NEAR-EARTH OBJECT 2009 BD , 2014, 1403.7699.

[46]  J. I. Katz,et al.  Why is interstellar object 1I/2017 U1 (`Oumuamua) rocky, tumbling and possibly very prolate? , 2018, 1802.02273.

[47]  A. Fitzsimmons,et al.  1I/'Oumuamua is tumbling , 2017 .

[48]  Sean N. Raymond,et al.  Implications of the interstellar object 1I/'Oumuamua for planetary dynamics and planetesimal formation , 2017, 1711.09599.

[49]  D. Trilling,et al.  EXPLORENEOs. I. DESCRIPTION AND FIRST RESULTS FROM THE WARM SPITZER NEAR-EARTH OBJECT SURVEY , 2010 .

[50]  Paul D. Feldman,et al.  Comet Bowell (1980b) , 1982 .

[51]  T. B. Spahr,et al.  ExploreNEOs. V. AVERAGE ALBEDO BY TAXONOMIC COMPLEX IN THE NEAR-EARTH ASTEROID POPULATION , 2011 .