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The serendipitous discovery of a possible new solar system object with ALMA

The unprecedented sensitivity of the Atacama Large millimeter/submillimeter array (ALMA) is providing many new discoveries. Several of these are serendipitous to the original goal of the observations. We report the discovery of previously unknown continuum sources, or a single fast moving new source, in our ALMA observations. Here we aim to determine the nature of the detections. The detections, at >5.8σ in the image plane and >14σ in the (u,v)plane, were made in two epochs of ALMA observations of a 25 arc second region around the asymptotic giant branch star W Aql in the continuum around 345 GHz. At a third epoch, covering 50x50 arcseconds, the source(s) were not seen. We have investigated if the detections could be spurious, if they could constitute a population of variable background sources, or if the observations revealed a fast moving single object. Based on our analysis, we conclude that a single object (with a flux of 3.0 mJy) exhibiting a large proper motion (87 arcsec/yr) is the most likely explanation. Until the nature of the source becomes clear, we have named it Gna. Unless there are yet unknown, but significant, issues with ALMA observations, we have detected a previously unknown objects in our solar system. Based on proper motion analysis we find that, if it is gravitationally bound, Gna is currently located at 1225 AU distance and has a size of 220880 km. Alternatively it is a much larger, planet-sized, object, gravitationally unbound, and located within 4000 AU, or beyond (out to 0.3~pc) if it is strongly variable. Our observations highlight the power of ALMA in detecting possible solar system objects, but also show how multiple epoch observations are crucial to identify what are otherwise probably assumed to be extra-galactic sources.

Comments: 6 pages, 5 figures; submitted to Astronomy & Astrophysics; Comments/suggestions on the nature of the source extremely welcome
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:1512.02650 [astro-ph.SR]
(or arXiv:1512.02650v1 [astro-ph.SR] for this version)

Submission history

From: Wouter Vlemmings [view email]
[v1] Tue, 8 Dec 2015 21:00:16 GMT (88kb)

Report of discovery of large object in far outer edges of solar system incites skeptical reactions

(—Two separate teams of researchers (one from Mexico, the other Sweden), have incited skepticism among the astronomy community by posting papers on the preprint server arXiv each describing a different large object they observed in the outer edges of the solar system. Both teams made their observations after reviewing data from ALMA—a cluster of radio dishes in the Chilean mountains.

One of the objects was found to be near W Aquilae in the night sky—the other adjacent to Alpha Centauri . Both groups report being skeptical at first regarding a faint glow, but monitored what they had seen nonetheless—to their surprise they found that the objects appeared to move relative to the stars behind them, which suggested they might be relatively close and that they might be orbiting the sun. Neither group was able to gain much evidence regarding the properties of the objects they had spied, because both of them were only able to make two observations, but both teams suggest there was enough data to allow for ruling out the object being an ordinary star.

The Swedish team nick-named the object they observed Gna, after a Nordic God known for its swiftness, and have told the press they had no intention of suggesting they had found the mythical Planet X which supposedly lies somewhere beyond Pluto. Instead they suggest it might be a large asteroid. The team from Mexico went a little further suggesting that the object they observed might possibly turn out to be a brown dwarf.

There is also the possibility, as some astronomers who have read the two papers suggest, that either or both of the objects are merely illusions, random blips or noise that for a moment or two appeared to take the shape of a very far away object. Some have even tweeted their opinions, insinuating that jumping on the Planet X bandwagon would be sheer folly.

Despite the skepticism, it is likely that other research groups will be training their instruments on the piece of sky where the objects were possibly seen, to prove or disprove their existence and to put a stop to the conjecture. Both of the teams involved have voiced their support of such efforts, noting that they would like an explanation for what they observed.

Explore further: Newly discovered celestial object defies categories

More information: A new submm source within a few arcseconds of α Centauri: ALMA discovers the most distant object of the solar system, arXiv:1512.02652 [astro-ph.SR]

The serendipitous discovery of a possible new solar system object with ALMA, arXiv:1512.02650 [astro-ph.SR]

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