![]() People Meet the people behind the science.Events Plan the meetings and conferences you want to attend with our comprehensive events calendar.Blog Enjoy a more personal take on the key events in and around science.Analysis Discover the stories behind the headlines.Features Take a deeper look at the emerging trends and key issues within the global scientific community.News Stay informed about the latest developments that affect scientists in all parts of the world.Research updates Keep track of the most exciting research breakthroughs and technology innovations.Latest Explore all the latest news and information on Physics World.If all goes well, she says, they will need “a couple of years” to complete the job. Pancino says that her team will need fresh observations to classify the rest of the 260 candidates and understand how many are dual AGNs. However, more work is needed before such analyses can be done. In particular, they say that the statistical distribution of distances separating the two black holes might reveal whether spiraling requires the gravitational pull of dark matter, as well as that of ordinary matter. ![]() But he says a couple of things remain unclear: why it was necessary to confirm the multiple sources using Hubble's images instead of Gaia images alone, and how many additional dual or lensed AGNs might turn up in more sensitive or higher-redshift survey data.īy going on to measure the properties of many dual AGNs, the researchers in Italy argue it should be possible to pin down the physical processes acting on supermassive black holes as they spiral in. As a further step, they analysed the spectra of five objects that do not have matches in the Hubble catalogue, establishing that two of them were dual AGNs.ĭavid Sanders, an astronomer at the University of Hawaii at Manoa, who was not involved in the research, says that the new method will “get a lot of attention”. They then trawled through the Hubble Space Telescope catalogue to try and obtain images of these objects, and found 26 matches - in each case confirming that the objects in question do indeed contain multiple sources. Using this method, Pancino, Filippo Mannucci and co-workers in Italy, the US and Norway identified 260 objects that could potentially be either dual AGNs, single AGNs that appear to be dual as a result of gravitational lensing, or single AGNs whose light has become mixed up with that from intervening stars 1. To increase their success, Elena Pancino, at the Arcetri Observatory in Florence, suggested to some her colleagues working on AGNs that it might be possible to use a different parameter from the Gaia catalogue – one which characterizes the shape of an object’s emission, with a single peak pointing to just one source and a double peak to two sources. But so far, they have netted only four close-knit dual AGNs within the relatively early universe. Scientists have tried many approaches, including looking for sources within the Gaia catalogue whose position tends to vary over time. Spotting such dual AGNs, however, has proved extremely tricky. These pairs would be seen as dual active galactic nuclei (AGN), which are extremely bright regions at the centre of galaxies whose radiation is not generated by stars. With many galaxies thought to have a supermassive black hole at their core, these mergers should result in pairs of the exceptionally massive objects spiraling in around a common centre-of-mass until they combine and give off an intense burst of gravitational waves. Many cosmological models tell us that as the universe evolves smaller galaxies merge to form larger ones. Relying on data from a vast sky survey carried out by the European Space Agency’s Gaia spacecraft, the researchers say their technique could help theorists to refine models of merging galaxies. Credit: Caltech-IPAC.Īstronomers in Italy have devised a new method for establishing which of the countless specks of light in the night sky might correspond to pairs of supermassive black holes spiraling in towards one another within a common galaxy. In this illustration, light from a smaller black hole (left) curves around a larger supermassive black hole and forms an almost-mirror image on the other side.
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