![]() Matter is heated to millions of degrees as it is pulled toward the black hole, so it glows in X-rays. NASA's telescopes that study black holes are looking at the surrounding environments of the black holes, where there is material very close to the event horizon. No light of any kind, including X-rays, can escape from inside the event horizon of a black hole, the region beyond which there is no return. ![]() How can we learn about black holes if they trap light, and can't actually be seen? Image Credit: NASA/JPL-Caltech/Roma Tre Univ.ġ. ![]() This supermassive black hole has been extensively studied due to its relatively close proximity to our galaxy. ![]() The X-ray light is coming from an active supermassive black hole, also known as a quasar, in the center of the galaxy. High-energy X-rays (magenta) captured by NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, are overlaid on visible-light images from both NASA's Hubble Space Telescope and the Sloan Digital Sky Survey. "This does not necessarily mean that the warp does not precess at all, it could do so, but much more slowly, and we are probably unable to measure this motion until we obtain better data," concludes Martín López Corredoira, and IAC researcher and co-author of the article.Galaxy NGC 1068 is shown in visible light and X-rays in this composite image. "In previous studies it had not been noticed," explains Zofia Chrobáková, a predoctoral researcher at the IAC and the first author of the article, "that the stars which are a few tens of millions of years old, such as the Cepheids, have a much larger warp than that of the stars visible with the Gaia mission, which are thousands of millions of years old." To arrive at this result the researchers have used data from the Gaia Mission of the European Space Agency (ESA), analysing the positions and velocities of hundreds of millions of stars in the outer disc. The study concludes that, using the warp of the old stars whose velocities have been measured, it is possible that the precession can disappear, or at least become slower than what is presently believed. Now, a new study by Zofia Chrobáková and Martín López Corredoira has taken into account the variation of the amplitude of the warp with the ages of the stars. As well as its annual revolution around the Sun, and its rotation period of 24 hours, the axis of the Earth precesses, which implies that the celestial pole is not always close to the present pole star, but that (as an example) 14,000 years ago it was close to the star Vega. Precession is not a phenomenon which occurs only in galaxies, it also happens to our planet. Furthermore, these researchers found that it was quicker than the theories predicted, a cycle every 600-700 million years, some three times the time it takes the Sun to travel once round the centre of the Galaxy. In 2020, an investigation announced the detection of the precession of the warp of the Milky Way disc, which means that the deformation in this outer region is not static, but that just like a spinning top the orientation of its axis is itself rotating with time. The stars, the gas, and the dust are all warped, and so are not in the same plane as the extended inner part of the disc, and an axis perpendicular to the planes of the warp defines their rotation. At first, it was thought that the disc was completely flat, but for some decades now it is known that the outermost part of the disc is distorted into what is called a "warp": in one direction it is twisted upwards, and in the opposite direction downwards. ![]() The Milky Way is a spiral galaxy, which means that it is composed, among other components, of a disc of stars, gas and dust, in which the spiral arms are contained. ![]()
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