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Tuesday, February 28, 2017

Planetary Debris Disk Detected around White Dwarf-Brown Dwarf System

Planetary Debris Disk Detected around White Dwarf-Brown Dwarf System

Feb 27, 2017 by News Staff / Source

Evidence of planetary debris surrounding a white dwarf and its substellar companion has been found by a University College London-led international team of astronomers. The discovery is remarkable because the debris appears to be rocky and suggests that terrestrial planets might exist in this exotic system.
A disc of rocky debris from a disrupted planetesimal surrounds the white dwarf-brown dwarf binary system SDSS 1557. Image credit: Mark Garlick, University College London, University of Warwick and University of Sheffield.
A disc of rocky debris from a disrupted planetesimal surrounds the white dwarf-brown dwarf binary system SDSS 1557. Image credit: Mark Garlick, University College London, University of Warwick and University of Sheffield.
The binary system in question is called SDSS J155720.77+091624.6 (hereafter SDSS 1557).
It is 1,592 light-years away from Earth and consists of a low-mass white dwarf (0.45 solar masses) and a brown dwarf (66 Jupiter’s masses).
To date, all exoplanets discovered in orbit around binary stars are gas giants and are thought to form in the icy regions of their systems.
In contrast to the carbon-rich icy material found in other binaries, the planetary material identified in SDSS 1557 has a high metal content, including silicon and magnesium.
These elements were identified as the debris flowed from its orbit onto the surface of the white dwarf, polluting it temporarily with at least 1017 g (or 1.1 trillion US tons) of matter, equating it to an asteroid at least 4 km in size.
“Building rocky planets around two suns is a challenge because the gravity of both stars can push and pull tremendously, preventing bits of rock and dust from sticking together and growing into full-fledged planets,” said lead author Dr. Jay Farihi, a researcher in the Department of Physics and Astronomy at the University College London.

“With the discovery of asteroid debris in the SDSS 1557 system, we see clear signatures of rocky planet assembly via large asteroids that formed, helping us understand how rocky exoplanets are made in double star systems.”
In the Solar System, the main asteroid belt contains the leftover building blocks for the terrestrial planets Mercury, Venus, Earth, and Mars, so planetary researchers study the asteroids to gain a better understanding of how terrestrial, and potentially habitable, planets are formed.
The same approach was used by Dr. Farihi and co-authors to study the SDSS 1557 system as any planets within it cannot yet be detected directly but the debris is spread in a large belt around the double stars, which is a much larger target for analysis.
“We know of thousands of binaries similar to SDSS 1557 but this is the first time we’ve seen asteroid debris and pollution,” said co-author Dr. Steven Parsons, from the University of Valparaíso and the University of Sheffield.
“The brown dwarf was effectively hidden by the dust until we looked with the right instrument, but when we observed SDSS 1557 in detail we recognized the brown dwarf’s subtle gravitational pull on the white dwarf.”
The astronomers studied SDSS 1557 and the chemical composition of the debris by measuring the absorption of different wavelengths of light or ‘spectra,’ using the Gemini Observatory South telescope and ESO’s Very Large Telescope.
“Any metals we see in the white dwarf will disappear within a few weeks, and sink down into the interior, unless the debris is continuously flowing onto the star,” said co-author Prof. Boris Gänsicke, from the University of Warwick.
“We’ll be looking at SDSS 1557 next with Hubble, to conclusively show the dust is made of rock rather than ice.”
A paper reporting this discovery is published in the journal Nature Astronomy (arXiv.org preprint).
_____
J. Farihi et al. A circumbinary debris disk in a polluted white dwarf system. Nature Astronomy, published online February 27, 2017; doi: 10.1038/s41550-016-0032

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How to Digitally Record/Video a UFO sighting:


Como registar digitalmente ou gravar um vídeo de um avistamento de um UFO:




Stabilize the camera on a tripod. If there is no tripod, then set it on top of a stable, flat surface. If that is not possible lean against a wall to stabilize your body and prevent the camera from filming in a shaky, unsteady manner.

Estabilize a camera com um tripé. Se não tiver um tripé, então coloque-a em cima de uma superfície estável. Se não for possível, então encoste-se a uma parede para estabilizar o corpo e evitar que a camera registe de maneira tremida e instável.

Provide visual reference points for comparison. This includes the horizon, treetops, lampposts, houses, and geographical landmarks (i.e., Horsetooth Reservoir, Mt. Adams, etc.) Provide this in the video whenever is appropriate and doesn’t detract from what your focus is, the UFO.

Forneça pontos visuais de referência para comparação. Isso inclui o horizonte, cimo das árvores, postes de iluminação, pontos de referência geográficos (como o Reservatório de Horsetooth, Mone Adams, etc) Forneça esses pontos no vídeo sempre que for apropriado e não se distraia do que é o seu foco, o UFO/a Nave.

Narrate your videotape. Provide details of the date, time, location, and direction (N,S,E,W) you are looking in. Provide your observations on the weather, including approximate temperature, windspeed, any visible cloud cover or noticeable weather anomalies or events. Narrate on the shape, size, color, movements, approximate altitude of the UFO, etc and what it appears to be doing. Also include any unusual physical, psychological or emotional sensations you might have. Narrate any visual reference points on camera so they correlate with what the viewer will see, and thereby will be better able to understand.

Faça a narração do vídeo. Forneça pormenores sobre a data, hora, local e direcção (Norte, Sul, Este, Oeste) que está a observar. Faça observações sobre as condições atmosféricas, incluindo a temperatura aproximada, velocidade do vento, quantidade de nuvens, anomalias ou acontecimentos meteorológicos evidentes. Descreva a forma, o tamanho, a cor, os movimentos, a altitude aproximada onde se encontra o UFO/nave, etc e o que aparenta estar a fazer. Inclua também quaisquer aspectos pouco habituais de sensações físicas, psicológicas ou emocionais que possa ter. Faça a narração de todos os pontos de referência visual que o espectador irá ver e que, deste modo, será capaz de compreender melhor.

Be persistent and consistent. Return to the scene to videotape and record at this same location. If you have been successful once, the UFO sightings may be occurring in this region regularly, perhaps for specific reasons unknown, and you may be successful again. You may also wish to return to the same location at a different time of day (daylight hours) for better orientation and reference. Film just a minute or two under “normal” circumstances for comparison. Write down what you remember immediately after. As soon as you are done recording the experience/event, immediately write down your impressions, memories, thoughts, emotions, etc. so it is on the record in writing. If there were other witnesses, have them independently record their own impressions, thoughts, etc. Include in this exercise any drawings, sketches, or diagrams. Make sure you date and sign your documentation.

Seja persistente e não contraditório. Volte ao local da cena e registe o mesmo local. Se foi bem sucedido uma vez, pode ser que nessa região ocorram avistamentos de UFOs/naves com regularidade, talvez por razões específicas desconhecidas, e talvez possa ser novamente bem sucedido. Pode também desejar voltar ao mesmo lugar a horas diferentes do dia (durante as horas de luz)para ter uma orientação e referência melhor. Filme apenas um ,inuto ou dois em circunstâncias “normais” para ter um termo de comparação. Escreva tudo o que viu imediatamente após o acontecimento. Logo após ter feito o registo da experiência/acontecimento, escreva imediatamente as impressões, memórias, pensamentos, emoções, etc para que fiquem registadas por escrito. Se houver outras testemunhas, peça-lhes para registar independentemente as suas próprias impressões, pensamentos, etc. Inclua quaisquer desenhos, esbolos, diagramas. Certifique-se que data e assina o seu documento/testemunho.

Always be prepared. Have a digital camera or better yet a video camera with you, charged and ready to go, at all times. Make sure you know how to use your camera (and your cell phone video/photo camera) quickly and properly. These events can occur suddenly, unexpectedly, and often quite randomly, so you will need to be prepared.

Esteja sempre preparado, Tenha sempre uma camera digital, melhor ainda, uma camera vídeo consigo, carregada e pronta a usar sempre que necessário. Certifique-se que sabe como lidar com a sua camera (ou com o seu celular/camera fotográfica) rápida e adequadamente. Esses acontecimentos podem acontecer súbita e inesperadamente e, por vezes, acidentalmente, por isso, necessita estar preparado.

Look up. Be prepared. Report. Share.

Olhe para cima, Esteja preparado, Relate, Partilhe.

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