{"id":208674,"date":"2025-05-01T06:55:27","date_gmt":"2025-04-30T20:55:27","guid":{"rendered":"https:\/\/science.nasa.gov\/universe\/the-universes-brightest-lights-have-some-dark-origins\/"},"modified":"2025-05-01T06:55:27","modified_gmt":"2025-04-30T20:55:27","slug":"the-universes-brightest-lights-have-some-dark-origins","status":"publish","type":"post","link":"https:\/\/www.vibewire.com.au\/?p=208674","title":{"rendered":"The Universe\u2019s Brightest Lights Have Some Dark Origins"},"content":{"rendered":"

Did you know some of the brightest sources of light in the sky come from the regions around black holes in the centers of galaxies? It sounds a little contradictory, but it\u2019s true! They may not look bright to our eyes, but satellites have spotted oodles of them across the universe.\u00a0<\/p>\n

One of those satellites is NASA\u2019s Fermi Gamma-ray Space Telescope<\/a>. Fermi has found thousands of these kinds of galaxies since it launched in 2008, and there are many more out there!<\/p>\n

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Watch a cosmic gamma-ray fireworks show in this animation using just a year of data from the Large Area Telescope (LAT) aboard NASA\u2019s Fermi Gamma-ray Space Telescope. Each object\u2019s magenta circle grows as it brightens and shrinks as it dims. The yellow circle represents the Sun following its apparent annual path across the sky. The animation shows a subset of the LAT gamma-ray records available for more than 1,500 objects in a continually updated repository. Over 90% of these sources are a type of galaxy called a blazar, powered by the activity of a supermassive black hole.<\/div>\n<\/div>\n
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NASA\u2019s Marshall Space Flight Center\/Daniel Kocevski<\/div>\n<\/div>\n<\/div>\n<\/div>\n

Black holes<\/a> are regions of space that have so much gravity that nothing \u2014 not light, not particles, nada \u2014 can escape. Most galaxies<\/a> have supermassive black holes at their centers, and these black holes are hundreds of thousands to billions of times the mass of our Sun. In active galactic nuclei<\/a> (also called \u201cAGN\u201d for short, or just \u201cactive galaxies\u201d) the central region is stuffed with gas and dust that\u2019s constantly falling toward <\/a>the black hole. As the gas and dust fall, they start to spin and form a disk. Because of the friction and other forces at work, the spinning disk starts to heat up.<\/p>\n

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\"Composite<\/a><\/figure>
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This composite view of the active galaxy Markarian 573 combines X-ray data (blue) from NASA\u2019s Chandra X-ray Observatory and radio observations (purple) from the Karl G. Jansky Very Large Array in New Mexico with a visible light image (gold) from the Hubble Space Telescope. Markarian 573 is an active galaxy that has two cones of emission streaming away from the supermassive black hole at its center.<\/div>\n
X-ray: NASA\/CXC\/SAO\/A.Paggi et al; Optical: NASA\/STScI; Radio: NSF\/NRAO\/VLA<\/div>\n<\/figcaption><\/div>\n<\/div>\n<\/div>\n

The disk\u2019s heat gets emitted as light, but not just wavelengths of it that we can see with our eyes. We detect light from AGN across the entire electromagnetic spectrum<\/a>, from the more familiar radio and optical waves through to the more exotic X-rays<\/a> and gamma rays<\/a>, which we need special telescopes<\/a> to spot.
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\"An<\/a><\/figure>
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In the heart of an active galaxy, matter falling toward a supermassive black hole creates jets of particles traveling near the speed of light as shown in this artist\u2019s concept.<\/div>\n
NASA\/Goddard Space Flight Center Conceptual Image Lab<\/div>\n<\/figcaption><\/div>\n<\/div>\n<\/div>\n

About one in 10 AGN beam out jets of energetic particles, which are traveling almost as fast as light. Scientists are studying these jets to try to understand how black holes \u2014 which pull everything in with their huge amounts of gravity \u2014 somehow provide the energy needed to propel the particles in these jets.<\/p>\n

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\"Side-by-side<\/a><\/figure>
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This artist\u2019s concept shows two views of the active galaxy TXS 0128+554, located around 500 million light-years away. Left: The galaxy\u2019s central jets appear as they would if we viewed them both at the same angle. The black hole, embedded in a disk of dust and gas, launches a pair of particle jets traveling at nearly the speed of light. Scientists think gamma rays (magenta) detected by NASA\u2019s Fermi Gamma-ray Space Telescope originate from the base of these jets. As the jets collide with material surrounding the galaxy, they form identical lobes seen at radio wavelengths (orange). The jets experienced two distinct bouts of activity, which created the gap between the lobes and the black hole. Right: The galaxy appears in its actual orientation, with its jets tipped out of our line of sight by about 50 degrees.<\/div>\n
NASA\u2019s Goddard Space Flight Center<\/div>\n<\/figcaption><\/div>\n<\/div>\n<\/div>\n

Many of the ways we tell one type of AGN from another depend on how they\u2019re oriented from our point of view. With radio galaxies, for example, we see the jets from the side as they\u2019re beaming vast amounts of energy into space. Then there\u2019s blazars<\/a>, which are a type of AGN that have a jet that is pointed almost directly at Earth, which makes the AGN particularly bright.\u00a0<\/p>\n

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\"Gamma-ray<\/a><\/figure>
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Blazar 3C 279\u2019s historic gamma-ray flare in 2015 can be seen in this image from the Large Area Telescope on NASA\u2019s Fermi satellite. During the flare, the blazar outshone the Vela pulsar, usually the brightest object in the gamma-ray sky.<\/div>\n
NASA\/DOE\/Fermi LAT Collaboration<\/div>\n<\/figcaption><\/div>\n<\/div>\n<\/div>\n

Fermi has been searching the sky for gamma ray sources since 2008. More than half of the sources it has found have been blazars. Gamma rays are useful because they can tell us a lot about how particles accelerate and how they interact with their environment.<\/p>\n

So why do we care about AGN? We know that some AGN formed early in the history of the universe. With their enormous power, they almost certainly affected how the universe changed over time. By discovering how AGN work, we can understand better how the universe came to be the way it is now.<\/p>\n

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