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Register a new userBreakthrough Listen Observations of 1I/Oumuamua with the GBT
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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 narrowband 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).
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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~hours at 4.5 micron (IRAC channel 2). We did not detect the object and place an upper limit on the flux of 0.3 uJy (3sigma). This implies an effective spherical diameter less than [98, 140, 440] meters and albedo greater than [0.2, 0.1, 0.01] under the assumption of low, middle, or high thermal beaming parameter eta, respectively. With an aspect ratio for `Oumuamua of 6:1, these results correspond to dimensions of [240:40, 341:57, 1080:180] meters, 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 `Oumuamuas 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 eta value and implied high albedo value for this solution, but, given our strict limits on CO and CO2, requires another gas species --- probably H2O --- to explain the observed non-gravitational acceleration. Our results extend the mystery of `Oumuamuas origin and evolution.
Breakthrough Listen (BL) is a ten-year initiative to search for signatures of technologically capable life beyond Earth via radio and optical observations of the local Universe. A core part of the BL program is a comprehensive survey of 1702 nearby stars at radio wavelengths (1-10 GHz). Here, we report on observations with the 64-m CSIRO Parkes radio telescope in New South Wales, Australia, and the 100-m Robert C. Byrd Green Bank radio telescope in West Virginia, USA. Over 2016 January to 2019 March, a sample of 1138 stars was observed at Green Bank using the 1.10-1.90 GHz and 1.80-2.80 GHz receivers, and 189 stars were observed with Parkes over 2.60-3.45 GHz. We searched these data for the presence of engineered signals with Doppler-acceleration drift rates between -4 to 4 Hz/s. Here, we detail our data analysis techniques and provide examples of detected events. After excluding events with characteristics consistent with terrestrial radio interference, we are left with zero candidates. Given the sensitivity of our observations, we can put an upper limit on the power of potential radio transmitters at these frequencies at 2x10^12 W, and 9x10^12 W for GBT and Parkes respectively. These observations constitute the most comprehensive search over 1.10-3.45 GHz for technosignatures to date. All data products, totalling ~219 TB, are available for download as part of the first BL data release (DR1), as described in a companion paper (Lebofsky et. al., 2019)
We have conducted a search for artificial radio emission associated with the Kepler-160 system following the report of the discovery of the Earth-like planet candidate KOI-456.04 on 2020 June 4 (arXiv:1905.09038v2). Our search targeted both narrowband (2.97 Hz) drifting ($pm 4$ Hz s$^{-1})$ and wideband pulsed (5 ms at all bandwidths) artificially-dispersed technosignatures using the turboSETI (arXiv:1709.03491v2) and SPANDAK pipelines, respectively, from 1-8 GHz. No candidates were identified above an upper limit Equivalent Isotropic Radiated Power (EIRP) of $5.9 times 10^{14}$ W for narrowband emission and $7.3 times 10^{12}$ W for wideband emission. Here we briefly describe our observations and data reduction procedure.
Exoplanetary systems are prime targets for the Search for Extraterrestrial Intelligence (SETI). With the recent uptick in the identification of candidate and confirmed exoplanets through the work of missions like the Transiting Exoplanet Survey Satellite (TESS), we are beginning to understand that Earth-like planets are common. In this work, we extend the Breakthrough Listen (BL) search for extraterrestrial intelligence to include targeted searches of stars identified by TESS as potential exoplanet hosts. We report on 113 30-min cadence observations collected for 28 targets selected from the TESS Input Catalog (TIC) from among those identified as containing signatures of transiting planets. The targets were searched for narrowband signals from 1-11 GHz using the turboSETI pipeline architecture modified for compatibility with the Google Cloud environment. Data were searched for drift rates of +/-4 Hz/s above a minimum signal-to-noise threshold of 10, following the parameters of previous searches conducted by Price et al. (2020) and Enriquez et al. (2017). The observations presented in this work establish some of the deepest limits to date over such a wide band (1-11 GHz) for life beyond Earth. We determine that fewer than 12.72% of the observed targets possess transmitters operating at these frequencies with an Equivalent Isotropic Radiated Power (EIRP) greater than our derived threshold of 4.9*10^(14) W.
The discovery of 1I/2017 U1 (Oumuamua) has provided the first glimpse of a planetesimal born in another planetary system. This interloper exhibits a variable colour within a range that is broadly consistent with local small bodies such as the P/D type asteroids, Jupiter Trojans, and dynamically excited Kuiper Belt Objects. 1I/Oumuamua appears unusually elongated in shape, with an axial ratio exceeding 5:1. Rotation period estimates are inconsistent and varied, with reported values between 6.9 and 8.3 hours. Here we analyse all available optical photometry reported to date. No single rotation period can explain the exhibited brightness variations. Rather, 1I/Oumuamua appears to be in an excited rotational state undergoing Non-Principal Axis (NPA) rotation, or tumbling. A satisfactory solution has apparent lightcurve frequencies of 0.135 and 0.126 hr-1 and implies a longest-to-shortest axis ratio of 5:1, though the available data are insufficient to uniquely constrain the true frequencies and shape. Assuming a body that responds to NPA rotation in a similar manner to Solar System asteroids and comets, the timescale to damp 1I/Oumuamuas tumbling is at least a billion years. 1I/Oumuamua was likely set tumbling within its parent planetary system, and will remain tumbling well after it has left ours.
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