杏吧原创

Black holes

https://www.esa.int/ESA_Multimedia/Images/2022/07/Stephan_s_Quintet_NIRCam_and_MIRI_imaging Stephan?s Quintet ? NIRCam and MIRI imaging An enormous mosaic of Stephan?s Quintet is the largest image to date from the NASA/ESA/CSA James Webb Space Telescope, covering about one-fifth of the Moon?s diameter. It contains over 150 million pixels and is constructed from almost 1,000 separate image files. The visual grouping of five galaxies was captured by Webb?s Near-Infrared Camera (NIRCam) and Mid-Infrared Instrument (MIRI). With its powerful, infrared vision and extremely high spatial resolution, Webb shows never-before-seen details in this galaxy group. Sparkling clusters of millions of young stars and starburst regions of fresh star birth grace the image. Sweeping tails of gas, dust and stars are being pulled from several of the galaxies due to gravitational interactions. Most dramatically, Webb?s MIRI instrument captures huge shock waves as one of the galaxies, NGC 7318B, smashes through the cluster. These regions surrounding the central pair of galaxies are shown in the colours red and gold. This composite NIRCam-MIRI image uses two of the three MIRI filters to best show and differentiate the hot dust and structure within the galaxy. MIRI sees a distinct difference in colour between the dust in the galaxies versus the shock waves between the interacting galaxies. The image processing specialists at the Space Telescope Science Institute in Baltimore opted to highlight that difference by giving MIRI data the distinct yellow and orange colours, in contrast to the blue and white colours assigned to stars at NIRCam?s wavelengths.

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This new visualization of a black hole illustrates how its gravity distorts our view, warping its surroundings as if seen in a carnival mirror. The visualization simulates the appearance of a black hole where infalling matter has collected into a thin, hot structure called an accretion disk. The black hole?s extreme gravity skews light emitted by different regions of the disk, producing the misshapen appearance. Bright knots constantly form and dissipate in the disk as magnetic fields wind and twist through the churning gas. Nearest the black hole, the gas orbits at close to the speed of light, while the outer portions spin a bit more slowly. This difference stretches and shears the bright knots, producing light and dark lanes in the disk. Viewed from the side, the disk looks brighter on the left than it does on the right. Glowing gas on the left side of the disk moves toward us so fast that the effects of Einstein?s relativity give it a boost in brightness; the opposite happens on the right side, where gas moving away us becomes slightly dimmer. This asymmetry disappears when we see the disk exactly face on because, from that perspective, none of the material is moving along our line of sight. Closest to the black hole, the gravitational light-bending becomes so excessive that we can see the underside of the disk as a bright ring of light seemingly outlining the black hole. This so-called ?photon ring? is composed of multiple rings, which grow progressively fainter and thinner, from light that has circled the black hole two, three, or even more times before escaping to reach our eyes. Because the black hole modeled in this visualization is spherical and non-rotating, the photon ring looks nearly circular and identical from any viewing angle. Inside the photon ring is the black hole?s shadow, an area roughly twice the size of the event horizon ? its point of no return. This visualization is ?mass invariant,? which means it can represent a black hole of any mass. The size of the black hole's shadow is proportional to its mass, but so is the size of the accreetion disk, so its properties scale accordingly. Simulations and movies like these really help us visualize what Einstein meant when he said that gravity warps the fabric of space and time.

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Primordial black holes crossing stars, orbit figures.

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