For The First Time Ever, Astronomers Have Observed a Black Hole Using a Magnetic Field to Feed
Black holes are a mystery – dense regions of space where there’s so much gravity not even light can escape.
Manyetik alanlarla da garip bir ilişkileri var.belki de hala daha gizemli. Manyetik alanların birçok kara deliğin etrafını sardığını biliyoruz … … ama güç bakımından büyük farklılıklar gösteriyor … … ve nasıl veya neden oluştuklarını bilmiyoruz.
Şimdi yeni bir çalışma sayesinde, bu garip bulmacanın başka bir parçası yerine düştü. İlk kez, astronomlar aktif beslenmede rol oynayan süper kütleli kara deliğin etrafında bir manyetik alan gözlemlediler.
At the heart of Cygnus A – an active galaxy 600 million light-years away and one of the brightest radio sources in the sky – astronomers have seen evidence that magnetic fields are trapping the material that feeds into the supermassive black hole. Sort of like a cosmic net.
This may help scientists figure out why some galactic nuclei are hugely active, spewing out enormous collimated jets from their polar regions, while others – like the Milky Way’s own Sagittarius A* – are only intermittently active, and others seem completely dormant.
Birleşik model ‘ e göre, aktif Galaktik çekirdekler – yani, besleyen bir galaksinin merkezindeki süper kütleli kara delik – kara deliğe düşen materyalin bir akordeon diskiyle çalacaktır.
Bu accretion disk dışında bir torus, ya da çörek şeklinde yapısı, toz ve gaz accretion disk beslenir.
How that structure is created, and why it stays there, are unclear – but observations of Cygnus A suggest that magnetic fields are at work to shape the torus and keep it in place.
Traditionally, these structures have been difficult to observe in optical and radio wavelengths, but a new instrument is especially sensitive to the infrared emissions from aligned dust grains.
Using the High-resolution Airborne Wideband Camera-plus (HAWC+) on board NASA’s Stratospheric Observatory For Infrared Astronomy (SOFIA), astronomers have been able to isolate and observe the dusty torus at the heart of Cygnus A.
“It’s always exciting to discover something completely new,” said astronomer Enrique Lopez-Rodriguez of the SOFIA Science Center and the Universities Space Research Association.
“These observations from HAWC+ are unique. They show us how infrared polarisation can contribute to the study of galaxies.”
It’s not entirely clear, either, how black holes’ jets form.
We know one thing, they do not originate from beyond the event horizon, from which no electromagnetic radiation can escape.
It is thought that material from the inner edge of the accretion disc travels, again, along magnetic field lines around the outside of the black hole to be blasted out from the poles at speeds approaching that of light.
A recent study, however, found that the black hole called V404 Cygni has a much weaker magnetic field than expected, in spite of its strong jets – which means that the magnetic fields interacting with black holes may not need to be as strong as thought, or some other mechanism is at play.
Either way, future observations will be able to help shed some light on these complex dynamics, and how magnetic fields shape the extreme environments around supermassive black holes.
“If, for example, HAWC+ reveals highly polarised infrared emission from the centers of active galaxies but not from quiescent galaxies,” NASA noted, “it would support the idea that magnetic fields regulate black hole feeding and reinforce astronomers’ confidence in the unified model of active galaxies.”
The team’s research has been published in The Astrophysical Journal Letters.
Source:http://iopscience.iop.org/article/10.3847/2041-8213/aacff5/pdf
