by When a star is born or dies, or when any other highly energetic phenomenon occurs in the universe, it emits X-rays, which are high-energy light particles that are invisible to the naked eye. These X-rays are the same type that doctors use to take pictures of broken bones inside the body. But instead of looking at the shadows produced by the X-ray-stopping bones inside a person, astronomers find X-rays flying through space to obtain images of events such as black holes and supernovae.
Images and spectra – charts that show the distribution of light over different wavelengths from an object – are the two main ways astronomers investigate the universe. Images tell them what things look like and where certain phenomena are happening, and spectra tell them how much energy the photons, or light particles, they are collecting have. Spectra can inform them about how the event they came from was created. When studying complex objects, they need both imaging and spectra.
Scientists and engineers designed the Chandra X-ray Observatory to detect these X-rays. Since 1999, Chandra data has provided astronomers with incredibly detailed images of some of the world’s most dramatic events.
Stars that are forming and dying cause supernova explosions that send chemical elements out into space. Chandra sees gas as stars fall into the deep gravitational holes of black holes, and sees gas a thousand times hotter than the Sun escaping galaxies in an explosive wind. It can be seen when the gravity of huge masses of dark matter captures that hot gas in huge pockets.
NASA designed Chandra to orbit the Earth because it would not be able to see any of this activity from the Earth’s surface. The Earth’s atmosphere absorbs X-rays coming from space, which is great for life on Earth because these X-rays can harm biological organisms. But it also means that even if NASA put Chandra on the top of the highest mountain, it still wouldn’t be able to detect any X-rays. NASA had to send Chandra into space.
I am an astrophysicist at the Smithsonian Astrophysical Observatory, part of the Center for Astrophysics | Harvard and Smithsonian. I’ve been working on Chandra since before it launched 25 years ago, and I’ve enjoyed seeing what the observatory can teach astronomers about the universe.
Supermassive black holes and their host galaxies
Astronomers have discovered supermassive black holes, with masses ten to 100 million times that of our Sun, at the center of all galaxies. These supermassive black holes mostly sit peacefully there, and astronomers can detect them by looking at the gravitational pull they exert on nearby stars.
But sometimes, stars or clouds fall into these black holes, which activates them and causes the region near the black hole to emit a lot of X-rays. When they are activated, they are called active galactic nuclei, AGN, or quasars.
My colleagues and I wanted to better understand what happens to the host galaxy when its black hole turns into an AGN. We picked one galaxy, ESO 428-G014, to look at with Chandra.
An AGN can dwarf its host galaxy, meaning that the AGN emits more light than all the other stars and objects in the host galaxy. The AGN also deposits a lot of energy within the confines of its host galaxy. This effect, which astronomers call feedback, is an important ingredient for researchers building simulations that model how the universe evolves over time. But we still don’t know how big a role the energy from AGN plays in star formation in its host galaxy.
Fortunately, images from Chandra can provide important insight. I use computational techniques to build and process images from the observatory that tell me about these AGNs.
The active supermassive black hole in ESO 428-G014 produces X-rays that illuminate a large area, extending as far as 15,000 light-years away from the black hole. The basic image I generated of ESO 428-G014 with Chandra data tells me that the region near the center is the brightest, and that there is a large elongated region of X-ray emission.
The same data, at slightly higher resolution, show two distinct regions of high X-ray emission. A “head,” encompassing the middle, and a slightly curved “tail” extend downward from this central region.
I can also process the data with an adaptive smoothing algorithm that brings the image into even higher resolution and creates a clearer picture of what the galaxy looks like. This shows clouds of gas around the bright center.
My team was able to see some of the ways in which the AGN interacts with the galaxy. The images show nuclear winds sweeping the galaxy, dense clouds and interstellar gas reflecting X-ray light, and jets shooting radio waves that penetrate clouds in the galaxy.
These images are teaching us how this feedback process works in detail and how to measure the amount of energy deposited by an AGN. These results will help researchers make more realistic simulations of how the universe evolves.
The next 25 years of X-ray astronomy
The year 2024 will be the 25th year since Chandra began observing the sky. My colleagues and I continue to rely on Chandra to answer questions about the origins of the universe that no other telescope can.
By providing X-ray data to astronomers, Chandra data complements information from the Hubble Space Telescope and the James Webb Space Telescope to provide astronomers with unique answers to open questions in astrophysics, such as the origin of supermassive black holes discovered at centers all the galaxies. from.
For this particular question, astronomers used Chandra to look for a distant galaxy first observed by the James Webb Space Telescope. This galaxy transmitted the light captured by Webb 13.4 billion years ago, when the universe was young. Chandra X-ray data revealed the presence of a bright supermassive black hole in this galaxy and suggested that supermassive black holes may form in the early collapse clouds of the universe.
Sharp imaging was critical to these discoveries. But Chandra is expected to last only another 10 years. To continue the search for answers, astronomers will need to begin designing the “Super Chandra” X-ray observatory that could succeed Chandra in the coming years, although NASA has yet to announce any firm plans.
This article is republished from The Conversation, a non-profit, independent news organization that brings you reliable facts and analysis to help you make sense of our complex world. It was written by Giuseppina Fabbiano Smithsonian Institution
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Giuseppina Fabbiano receives funding from NASA, SI, NSF.
