- 2844 - CHANDRA - X-rays to sound and Infrared? Galaxy clusters have proven key to testing dark matter and understanding dark energy. X-ray observations first revealed the wildly hot gas within clusters, gas that would have drifted away if it weren’t for the cluster’s dark matter, which gravitationally holds it in place.
-------------------- 2844 - CHANDRA - X-rays to sound and Infrared?
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- Every sound begins with a vibration. When those vibrations travel through the air, they can enter the human eardrum where they are eventually turned into electrical signals that our brain interprets as sound. These vibrations can come from many sources here on Earth as well as those in our Solar System and even across our Universe.
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- Sound travels in a wave and has its own distinct properties. One of these is frequency, which is the measurement of how many peaks (or troughs) of a wave pass a particular point over a certain period of time.
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- Frequency is most often measured in the unit of the Hertz (Hz), which is the number per second. In general, humans can hear in the range of 20 to 20,000 Hz. An elephant can hear in the range below humans, while dogs and cats are sensitive to much higher-frequency sounds. You know, the dog whistle effect.
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- Beyond the animal world, sounds can come from a variety of sources. Natural phenomena such as weather, earthquakes, and even black holes can produce very low-frequency sounds, while humans have harnessed sound for improvements in technology such as medical imaging.
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- Here we will explore how scientists are using NASA's Chandra X-ray Observatory and other instruments around the world and in space to study the cosmos through sound. Whether it comes from vocal chords in our throats or the surface of the Sun, sound plays a valuable role in our understanding of the world and cosmos around us.
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- Chandra’s 53-hour observation of the central region of the Perseus galaxy cluster has revealed wavelike features that appear to be sound waves. The features were discovered by using a special image-processing technique to bring out subtle changes in brightness.
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- These sound waves are thought to have been generated by explosive events occurring around a supermassive black hole in Perseus A, the huge galaxy at the center of the cluster. The data also shows two vast, bubble-shaped cavities filled with high-energy particles and magnetic fields.
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- These cavities create the sound waves by pushing the hot X-ray emitting gas aside. The pitch of the sound waves translates into the note of B flat, “57 octaves” below middle-C. This frequency is over a million billion times deeper than the limits of human hearing.
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- Diaz-Merced lost her sight in her early 20s while studying physics, and now regularly works with software that can help present numerical data as sound, using pitch, volume, or rhythm to distinguish between different data values.
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- Diaz-Merced programmed the Chandra X-ray data into special software and converted it into sound. X-rays to sound waves. Sonnert then sensed that the notes could become something more harmonious to the ear. He contacted Studtrucker who chose short passages from the sonified notes, about 70 bars in total, and added harmonies in different musical styles.
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- The project shows that something as far away and otherworldly as an X-ray-emitting cataclysmic variable binary star system can be significant to humans for two distinct reasons, one scientific and one artistic.
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- Turning a pulsar's rotational data into sound makes it easier to observe patterns and make comparisons between different nebulous pulsar rotational speeds. as a pulsar ages it spins at a slower speed. listen to the different pulsar heartbeats. what can you guess about how fast these different pulsars rotate? Which pulsar is the oldest? How about the youngest?
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- Neutron stars are strange and fascinating objects. They represent an extreme state of matter that physicists are eager to know more about. Yet, even if you could visit one, you would be well-advised to turn down the offer.
- The intense gravitational field would pull your spacecraft to pieces before it reached the surface. The magnetic fields around neutron stars are also extremely strong. Magnetic forces squeeze the atoms into the shape of cigars. Even if your spacecraft prudently stayed a few thousand miles above the surface neutron star so as to avoid the problems of intense gravitational and magnetic fields, you would still face another potentially fatal hazard.
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- If the neutron star is rotating rapidly, as most young neutron stars are, the strong magnetic fields combined with rapid rotation create an awesome generator that can produce electric potential differences of quadrillions of volts. Such voltages, which are 30 million times greater than those of lightning bolts, create deadly blizzards of high-energy particles.
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- These high-energy particles produce beams of radiation from radio through gamma-ray energies. Like a rotating lighthouse beam, the radiation can be observed as a pulsing source of radiation, or pulsar.
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- Pulsars were first observed by radio astronomers in 1967. The pulsar in the Crab Nebula, one of the youngest and most energetic pulsars known, has been observed to pulse in almost every wavelength, radio, optical, X-ray, and gamma-ray.
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- Infrared astronomy, study of astronomical objects through observations of the infrared radiation that they emit. Various types of celestial objects, including the planets of the solar system, stars, nebulae, and galaxies, give off energy at wavelengths in the infrared region of the electromagnetic spectrum (i.e., from about one micrometer to one millimeter).
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- The techniques of infrared astronomy enable investigators to examine many such objects that cannot otherwise be seen from the Earth because the light of optical wavelengths that they emit is blocked by intervening dust particles.
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- Infrared astronomy originated in the early 1800s with the work of the British astronomer Sir William Herschel, who discovered the existence of infrared radiation while studying sunlight.
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- The first systematic infrared observations of stellar objects were made by the American astronomers W.W. Coblentz, Edison Pettit, and Seth B. Nicholson in the 1920s. Modern infrared techniques, such as the use of cryogenic detector systems (to eliminate obstruction by infrared radiation released by the detection equipment itself) and special interference filters for ground-based telescopes, were introduced during the early 1960s.
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- By the end of the decade, Gerry Neugebauer and Robert Leighton of the United States had surveyed the sky at the relatively short infrared wavelength of 2.2 micrometers and identified approximately 20,000 sources in the northern hemispheric sky alone.
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- Since that time, balloons, rockets, and spacecraft have been employed to make observations of infrared wavelengths from 35 to 350 micrometers. Radiation at such wavelengths is absorbed by water vapor in the atmosphere, and so telescopes and spectrographs have to be carried to high altitudes above most of the absorbing molecules.
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- Specially instrumented high-flying aircraft such as the Kuiper Airborne Observatory and the Stratospheric Observatory for Infrared Astronomy have been designed to facilitate infrared observations near microwave frequencies.
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- In January 1983 the United States, in collaboration with the United Kingdom and the Netherlands, launched the Infrared Astronomical Satellite (IRAS), an unmanned orbiting observatory equipped with a 57-centimeter (22-inch) infrared telescope sensitive to wavelengths of 8 to 100 micrometers in the infrared spectrum. At these wavelengths, IRAS made a number of unexpected discoveries in a brief period of service that ended in November 1983.
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- The most significant of these were clouds of solid debris around Vega, Fomalhaut, and several other stars, the presence of which strongly suggests the formation of planetary systems similar to that of the Sun. Other important findings included various clouds of interstellar gas and dust where new stars are being formed and an object, designated 1983TB, thought to be the parent body for the swarm of meteoroids known as Geminids.
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- IRAS was succeeded in 1995–98 by the European Space Agency’s Infrared Space Observatory, which had a 60-centimeter (24-inch) telescope with a camera sensitive to wavelengths in the range of 2.5–17 micrometers and a photometer and a pair of spectrometers that, between them, extended the range to 200 micrometers.
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- IRAS made significant observations of protoplanetary disks of dust and gas around young stars, with results suggesting that individual planets can form over periods as brief as 20 million years. It determined that these disks are rich in silicates, the minerals that form the basis of many common types of rock. It also discovered a large number of brown dwarfs, objects in interstellar space that are too small to become stars but too massive to be considered planets.
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- The most advanced infrared space observatory is a U.S. satellite, the Spitzer Space Telescope, which is built around an all-beryllium 85-centimeter (33-inch) primary mirror that focuses infrared light on three instruments—a general-purpose infrared camera, a spectrograph sensitive to mid-infrared wavelengths, and an imaging photometer taking measurements in three far-infrared bands.
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- Together the instruments cover a wavelength range of 3.6 to 180 micrometers. The most striking results from the Spitzer’s observations concern extrasolar planets. The Spitzer has determined the temperature and the atmospheric structure, composition, and dynamics of several extrasolar planets
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- Although the human eye remains an important astronomical tool, detectors capable of greater sensitivity and more rapid response are needed to observe at visible wavelengths and, especially, to extend observations beyond that region of the electromagnetic spectrum.
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- Photography was an essential tool from the late 19th century until the 1980s, when it was supplanted by charge-coupled devices (CCDs). However, photography still provides a useful archival record. A photograph of a particular celestial object may include the images of many other objects that were not of interest when the picture was taken but that become the focus of study years later.
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- When quasars were discovered in 1963, for example, photographic plates exposed before 1900 and held in the Harvard College Observatory were examined to trace possible changes in position or intensity of the radio object newly identified as quasar 3C 273. Also, major photographic surveys, such as those of the National Geographic Society and the Palomar Observatory, can provide a historical base for long-term studies.
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- Photographic film converted only a few percent of the incident photons into images, whereas CCDs have efficiencies of nearly 100 percent. CCDs can be used for a wide range of wavelengths, from the X-ray into the near-infrared.
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- Gamma rays are detectable through their Compton scattering, electron-positron pair production, or Cerenkov radiation. For infrared wavelengths longer than a few microns, semiconductor detectors that operate at very low (cryogenic) temperatures are used. Reception of radio waves is based on the production of a small voltage in an antenna rather than on photon counting.
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- Spectroscopy involves measuring the intensity of the radiation as a function of wavelength or frequency. In some detectors, such as those for X-rays and gamma rays, the energy of each photon can be measured directly.
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- For low-resolution spectroscopy, broadband filters suffice to select wavelength intervals. Greater resolution can be obtained with prisms, gratings, and interferometers.
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- On the eve of the 20th anniversaries for both the Chandra and XMM-Newton X-ray observatories, we look back at seven of their most incredible discoveries.
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- This year marks the 20th anniversary of two landmark missions: the Chandra X-ray Observatory, one of NASA's Great Observatories, which launched July 23, 1999, and the European Space Agency's X-ray Multi-Mirror mission (XMM-Newton), which launched a few months later on December 10th.
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- Together, these satellites revolutionized X-ray astronomy, bringing it on par with astronomy at other wavelengths. To astronomers’ surprise, Chandra’s image of Cassiopeia A, the bloom of gas left over after a massive star went supernova some 340 years ago, revealed a star turned inside out.
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- While massive stars fuse the heaviest elements in their cores and lighter elements in surrounding, onion-like layers, the Cas A explosion had flung clumps of iron to the outermost regions. The find suggests the star’s contents mixed together right before or after its core collapsed (or both).
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- Chandra and XMM-Newton observations of iron atoms in the hot gas orbiting stellar-mass black holes have enabled astronomers to measure the black holes' spins. By measuring how a black hole’s strong gravity smears the emissions from iron ions, astronomers can see how close the gas comes to the event horizon, the closer it comes, the faster the black hole is spinning. Astronomers have used this and other X-ray-based methods to gauge the spins of dozens of black holes.
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- Monitoring by Chandra and XMM-Newton has also shed light on the slumbering beast at the center of the Milky Way known as Sgr A*. While Sgr A* doesn’t seem to be devouring gas in the manner of the supermassive black holes that power distant quasars, it’s doing something that sets off roughly daily X-ray flares.
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- Sometimes they’re accompanied by infrared sizzles, but other times the X-rays pop on their own. The flares may originate in snapping magnetic fields, the occasional ingestion of an asteroid, or something else entirely.
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- The combination of X-ray and radio observations of galaxy clusters solved a long-term mystery: The hot gas between galaxies in clusters ought to cool over time, raining down on the clusters’ central galaxies and forming stars by the handful.
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- But in many clusters astronomers haven’t found the expected stellar newborns. Turns out radio-emitting jets from the central galaxies’ supermassive black holes blow bubbles into the surrounding X-ray-emitting gas, sending out pressure waves that pump heat back into the surrounding medium, which prevents it from cooling. Astronomers soon realized that this concept of “black hole feedback” might affect everything from galaxy evolution to cosmology.
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- From the launch of the Aerobee rocket in 1962, astronomers had known that the X-ray sky wasn’t dark, instead teeming with high-energy photons. The Einstein Observatory showed that supermassive black holes, too far away or faint to be seen individually, could explain this background. But it was Chandra that sharpened the view, resolving almost all of the background into its individual sources. Data from Chandra and XMM-Newton suggest that most of the sources that remain undetected are shrouded in gas and dust.
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- X-ray observations have provided direct evidence of star-planet interactions, such as when XMM-Newton caught flares from the HD 17156 system that appeared whenever the hot Jupiter came closest to its star. X-ray data also temper ideas of habitability.
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- XMM-Newton observations revealed that high-energy radiation irradiates the three Earth-size planets in Trappist-1’s so-called habitable zone and has probably long ago stripped them of their atmospheres.
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- Observations showed that Proxima Centauri b receives 250 times more X-rays from its star than Earth does from the Sun; its habitability, too, is uncertain.
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- Galaxy clusters have proven key to testing dark matter and understanding dark energy. X-ray observations first revealed the wildly hot gas within clusters, gas that would have drifted away if it weren’t for the cluster’s dark matter, which gravitationally holds it in place.
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- Astronomers have observed clusters dating back to when the universe was less than half its current age, estimating the growth of these huge structures over cosmic time. The result: solid evidence for the existence of dark energy and a way to gauge its density and equation of state.
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- What astronomers can learn going beyond the “visible“!
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- September 27, 2020 2844
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