Today’s Jesus and Mo strip, called “Trump“, came with a short summary: “God wants you to stop projecting your own desires onto him.”
Clearly Mo is a Democrat! But of course, anybody who wishes that Trump had been killed is morally off the rails, though I’ve heard that from a few people.
Rehabilitation robots, first introduced in the 1990s, are just what they sound like – robotics used to aid in regaining function through rehabilitation following an injury. The idea sounds compelling, and the technology has been advancing steadily. But still we have to ask ourselves the question – do they actually help, and what is the evidence? A recent comprehensive meta-analysis and systematic […]
The post The Evidence for Rehabilitation Robots first appeared on Science-Based Medicine.Think about background radiation and most people immediately think of the cosmic background radiation and stories of pigeon excrement during its discovery. That’s for another day though. Turns out that the universe has several background radiations, such as infrared and even gravitational wave backgrounds. NASA’s New Horizons is far enough out of the Solar System now that it’s in the perfect place to measure the cosmic optical background (COB). Most of this light comes from the stars in galaxies, but astronomers have always wondered if there are other sources of light filling our night sky. New Horizons has an answer. No!
Ok lets talk pigeon excrement. Back in 1965 two telecommunication engineers were exploring signal interference at the Bell Laboratory. Penzias and Wilson detected a faint ‘hum’ in all directions and initially put it down to pigeon excrement as they nested in the horn of the radio receiver. Instead, what they had discovered was the cosmic background radiation, the faint glow that permeates the entire universe and is the thermal radiation left over from the Big Bang. Studying it allows us to understand more about the Universe when it was 380,000 years old.
The full-sky image of the temperature fluctuations (shown as color differences) in the cosmic microwave background, made from nine years of WMAP observations. These are the seeds of galaxies, from a time when the universe was under 400,000 years old. Credit: NASA/WMAPIn the late 80’s a different type of background radiation was detected; the infrared background radiation. It consists of the diffuse infrared glow that fills the universe coming from numerous sources throughout the history of the universe. It is mostly from thermal emissions from dust grains heated by stellar radiation. In addition to this is the gravity wave background although this has yet to be detected.
Another hotly debated background is the cosmic optical background (COB), a diffuse light which originates from stars and galaxies and spans the whole of the visible spectrum. There has been gathering momentum in its study however with observations from Hubble Space Telescope and the Spitzer Infrared Telescope. The studies however revealed that a large contribution to a general background optical glow come from faint unresolved galaxies. The study of the COB allows us to explore the total energy output of the universe, about galaxy and star formation across the history of the cosmos.
The detection of the COB is a challenging one however with Earth based instruments or even those in Earth orbit plagued by interference. The zodiacal light for example is the result of sunlight scattered by interplanetary dust, it is dominant in the inner solar system and makes studies of the COB difficult. The New Horizon probe is ideally positioned out beyond the orbit of Pluto over 8 billion kilometres away from interference. On board New Horizons is the LORRI (Long Range Reconnaissance Imager) camera which was identified as an ideal platform to begin a search.
The New Horizons instrument payload that is currently doing planetary science, heliospheric measurements, and astrophysical observations. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research InstituteUsing images from the LORRI camera, a team of astronomers led by Marc Postman from the Space Telescope Science Institute attempted to measure the COB over the range 0.4 to 0.9 micrometers. The images were from high galactic latitudes to ensure no diffuse light from the Milky Way or scattered light from bright stars. Isolating the COB contribution to the total sky brightness levels required digitally subtracting the scattered light from bright stars and galaxies and from faint stars within the field that were fainter than that detectable by LORRI. Interestingly, the results showed that, based on the estimated galaxy counts in the sampled regions the COB is the result of light from all the galaxies within our observable region of the universe.
Source : New Synoptic Observations of the Cosmic Optical Background with New Horizons
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The prospect of actually resolving the event horizon of black holes feels like the stuff of science fiction yet it is a reality. Already the Event Horizon Telescope (EHT) has resolved the horizon of the black holes at the centre of the Milky Way and M87. A team of astronomers are now looking to the next generation of the EHT which will work at multiple frequencies with more telescopes than EHT. A new paper suggests it may even be possible to capture the ring where light goes into orbit around the black hole at the centre of the Milky Way.
Black holes are strange objects that are the powerhouses of many galactic phenomenon. They have a complex anatomy with a singularity at the centre, a point of infinite density where gravity is so intense that the laws of physics cease to work. Surrounding the singularity is the event horizon, the boundary beyond which, nothing, not even light can escape. Just outside the event horizon is the photon ring and it is here that light is bent into a circular orbit around the singularity. Further out than this is the accretion disk but the focus of the next generation Event Horizon Telescope will be the photon ring.
The Event Horizon Telescope name is a little misleading for it is not one telescope but a global network of radio telescopes that work together to act as a virtual Earth-sized radio telescope. The technology that makes this happen is known as interferometry where the telescopes are all connected together. The very long baseline of the telescope or put more simply the fact it is virtually VERY big means it has incredible resolution capabilities allowing it to capture the event horizon around Sagittarius A at the centre of the Milky Way and also of the black hole at centre of M87.
The ALMA array in Chile. Once ALMA was added to the Event Horizon Telescope, it increased the EHT’s power by a factor of 10. Image: ALMA (ESO/NAOJ/NRAO), O. DessibourgThe EHT was launched in 2009 but now attention is turning to the next generation. The addition of ten new dishes and a whole host of new technology will transform EHT. Modern high-speed data transfer protocols will speed up transfer times and the addition of new dishes and technology will mean EHT will be able to observe at 86, 230 and 345 GHz simultaneously. This allows for the utilisation of frequency phase transfer techniques where lower frequency data can be used to supplement higher frequency. Using this will mean integration times of minutes at 345 GHz rather than seconds opening up a whole universe of new observations such as, the photon rings of black holes.
Studies of the supermassive black hole at the centre of M87 and Sagittarius A suggest a magnetically arrested accretion disk. In this accretion model, the accretion disk forms a series of irregular spiral streams and a vertical magnetic field, which is split into separate field lines, pokes through the accretion plane. As the disk rotates the material spirals inward, dragging the field lines and twist them around the axis of rotation leading to the formation of jets. These magnetically arrested disks exhibit symmetrically polarised synchrotron emissions which were used by a team of astronomers to study the detectability of the photon ring using next generation EHT.
M87 and the jet streaming away from its central supermassive black hole. Credits: NASA, ESA and the Hubble Heritage Team (STScI/AURA); Acknowledgment: P. Cote (Herzberg Institute of Astrophysics) and E. Baltz (Stanford University)The paper authored by Kaitlyn M. Shavelle and Daniel C. M. Palumbo from the Princeton University and Harvard & Smithsonian (respectively) show through simulations that the planned enhancements to the EHT are likely to enable the detection of photon rings. In the analyses of the enhancements they find that the higher sensitivity of the new EHT will likely be more critical than better processing techniques in the detection of the photon ring.
The post Next Generation Event Horizon Telescope To Unlock Mysteries of Black Holes appeared first on Universe Today.