A New Search for Extrasolar Planets from the Arecibo Observatory

posted by administrador on Fri, 07/14/2017 - 07:25
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La estrella de Barnard será estudiada simultáneamente desde distintos observatorios

The National Science Foundation’s Arecibo Observatory, the Planetary Habitability Laboratory of the University of Puerto Rico at Arecibo and the University of Antioquia at Medellin (Colombia), joined the Red Dots project in the search for new planets around our nearest stars. This new collaboration will simultaneously observe in both the optical and radio spectrum Barnard’s Star, a popular star in the science fiction literature. 
 
Barnard's star is a low-mass red dwarf almost six light-years away and the second-closest stellar system to our Sun after the Alpha Centauri triple-star system. There are hints of a possible super-Earth mass planet in a cold orbit around this star. 
 
The Arecibo Observatory has a new campaign to observe nearby red dwarf stars with planets. The purpose of this campaign is to detect radio emissions from these stars, such as from flares, to help characterize their radiation and magnetic environment and any potential perturbations due to other bodies. These perturbations might reveal the presence of new sub-stellar objects including planets.
 
Barnard’s Star will be the eighth red dwarf star to be recently observed by the Arecibo Observatory. Results from Gliese 436, Ross 128, Wolf 359, HD 95735, BD +202465, V* RY Sex, and K2-18 are currently being analyzed. These observations are led by Prof. Abel Méndez, Director of the Planetary Habitability Laboratory of the University of Puerto Rico at Arecibo in collaboration with Prof. Jorge Zuluaga from the Universidad de Antioquia in Colombia.
 
The Red Dots team will be joining the observations with the Arecibo Observatory of Barnard’s Star in coordination with other observatories. They are planning simultaneous photometric and spectral observations from SNO, LCO, TJO, and CARMENES from Spain, and earlier with ASH2 from Chile. All these observations will be used to understand the star but more observations by the Red Dots team will be necessary for the detection of any new planet.
 
The first extrasolar planets were discovered from the Arecibo Observatory in 1992. They were three small planets named Draugr, Poltergeist, and Phobetor around the Lich Pulsar, a fast rotating neutron star that emits a beam of electromagnetic radiation. The first planet around a sun-like star was later discovered in 1995 and today we know of more than 3,500 of them. Recent observations by the Arecibo Observatory have been able to detect brown dwarfs, but no new planet yet.
 
The first and only time that Barnard’s Star was observed from the Arecibo Observatory was during the SETI Institute’s Phoenix Project (1998-2004). The new observations are in a different frequency (4 to 5 GHz) where radio emission from stellar flares have been observed in other similar or cooler objects. This is the first time Barnard’s Star is seen with such frequencies and sensitivity.
 
The observations of Barnard’s Star are next Sunday, July 16. Another star, Ross 128, will be observed again later that day because it showed potential radio emissions that require follow-up. Results from these observations will be available later that week. The Red Dots team keeps an open journal of their observational campaign.

Strange emissions from Ross 128

So far, the Arecibo campaign observed Gliese 436, Ross 128, Wolf 359, HD 95735, BD +202465, V* RY Sex, and K2-18. Only Gliese 436 and K2-18 are known to have planets. Observations were done between April and May 2017 in the C-band (4 to 5 GHz).

Two weeks after these observations, it was realized that there were some very peculiar signals in the 10-minute dynamic spectrum that we obtained from Ross 128 (GJ 447), observed May 12 at 8:53 PM AST (2017/05/13 00:53:55 UTC). The signals consisted of broadband quasi-periodic non-polarized pulses with very strong dispersion-like features. We believe that the signals are not local radio frequency interferences (RFI) since they are unique to Ross 128 and observations of other stars immediately before and after did not show anything similar.

The origin of these signals are unknown, but there are three main possible explanations: they could be (1) emissions from Ross 128 similar to Type II solar flares, (2) emissions from another object in the field of view of Ross 128, or just (3) burst from a high orbit satellite since low orbit satellites are quick to move out of the field of view. The signals are probably too dim for other radio telescopes in the world and FAST is currently under calibration.

Each of the possible explanations has their own problems. For example, Type II solar flares occur at much lower frequencies and the dispersion suggests a much farther source or a dense electron field (e.g. the stellar atmosphere?). Also, there are no many nearby objects in the field of view of Ross 128 and we have never seen satellites emit bursts like that, which were common in our other star observations. In case you are wondering, the recurrent aliens hypothesis is at the bottom of many other better explanations.

Therefore, there is a mystery here and the three main explanations are as good as any at this moment. Fortunately, the campaign have obtained more time to observe Ross 128 next Sunday, July 16, and they might clarify soon the nature of its radio emissions, but there are no guarantees. The campaign will also observe Barnard’s star that day to collaborate with the Red Dots project. Results from these observations will be presented later that week.

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