Black holes are often misunderstood to be just that: dark and mysterious voids that are somehow akin to Alice in Wonderland\u2019s mind-bending rabbit hole.\u00a0<\/p>\n
But rather than a tunnel of nothing, a black hole is actually something \u2014 and a lot of it. The densest objects in the universe, black holes exert tremendous gravitational pull, gathering in the surrounding fabric of space and time, and generating huge disks of matter that whirl toward a black hole before falling in, past the point of no return.\u00a0<\/p>\n
In recent years, as astronomers have been able to train more telescopes on the sky, for longer stretches of time, they have captured a surprising range of black hole behavior.<\/p>\n
\u201cIt used to be that we didn\u2019t have eyes on systems all the time,\u201d says Erin Kara, an associate professor of physics at MIT. \u201cNow we\u2019re seeing that they can turn on and off at rates that are much faster than we ever thought possible. We see things are getting sucked in toward black holes faster than we thought, perhaps due to stars whipping around and getting trapped in a black hole\u2019s accretion disk.\u201d<\/p>\n
Kara and her group in MIT\u2019s Kavli Institute for Astrphysics and Space Research are at the forefront of black hole physics. She is using data from telescopes in space and on the ground to study the properties of black holes, especially supermassive black holes \u2014 the ultradense giants at the centers of galaxies. Supermassive black holes are the engines of galaxy formation. Kara, who recently earned tenure at MIT, seeks to connect the extreme physics of black holes with how galaxies such as our own Milky Way come to be.<\/p>\n
\u201cIt\u2019s amazing that we as humans can know anything about what\u2019s happening billions of light years away,\u201d Kara says. \u201cThere\u2019s a lot of new open puzzles about supermassive black holes that I\u2019m excited about.\u201d\u00a0<\/p>\n
Early impact<\/strong><\/p>\n Kara was born and raised in Bethlehem, Pennsylvania, as the youngest of four. Her mother was a nurse, and her father a doctor, so it felt only natural for Kara to follow their lead. She set out on a premed track at Barnard College of Columbia University. As part of the program that first year, she took an introductory physics class and was instantly drawn to the subject\u2019s concrete, fundamental descriptions of the physical world, from the quantum to cosmic scales.\u00a0<\/p>\n \u201cPhysics was always the class that explained things at the ground level,\u201d Kara recalls. \u201cAnd I thought, wow, this is cool. I have to keep going with this.\u201d<\/p>\n In class, she kept asking questions and wanting to know more. Her professor, astronomer\u00a0Reshmi Mukherjee, took note and invited Kara to join her research group as a summer intern. The team would be working on new data from a telescope that was readying for launch. That summer, in June 2008, NASA launched the Fermi Gamma-Ray Space Telescope into low-Earth orbit, with the purpose of surveying the sky for sources of gamma rays \u2014 high-energy radiation that is produced by black holes, neutron stars, and other extreme astrophysical objects.\u00a0<\/p>\n When the telescope started sending back data,\u00a0Mukherjee\u00a0assigned Kara a project: to characterize two of the telescope\u2019s unidentified gamma-ray signals. Both signals were bright, and the question was whether they came from nearby, within the Milky Way galaxy, or much further away. If the latter was the case, it would mean the sources were possibly quasars \u2014 a type of extremely active supermassive black hole that at the time was a rarity in astronomy observations.\u00a0<\/p>\n Kara got to work on the data and soon confirmed that both sources were indeed quasars.\u00a0<\/p>\n \u201cIt was a small discovery, but it felt awesome,\u201d Kara says. \u201cAnd I love that about astronomy, that there are so many unanswered questions, and even early on in your career, you can make an impact.\u201d<\/p>\n Needless to say, Kara caught the astronomy bug, and soon opted to switch from premed to physics, though the new path was not always smooth. On Barnard\u2019s all-women\u2019s campus, introductory classes in physics were small, and professors were encouraging and approachable. In contrast, upper-level courses were held at Columbia, where Kara was one of a much larger, co-ed cohort.\u00a0<\/p>\n \u201cIt\u2019s a very unique experience to be with all women in a physics environment, and then to see how my feelings about my own abilities changed, just based on the environment,\u201d Kara reflects. \u201cI went to Columbia and all of a sudden felt like I couldn\u2019t do this. All these guys were much more confident and outwardly understanding of the material. In the end, I did well there too. And that juxtaposition helped me gain confidence and know, yeah, I belong here.\u201d<\/p>\n Black hole reverb<\/strong><\/p>\n After graduating with a major in physics and a minor in art history, Kara went abroad, to the Institute of Astronomy at Cambridge University. She earned a scholarship there to pursue a one-year master\u2019s degree in physics, but she ended up staying to complete a PhD on a topic that was just starting to grow roots: black hole X-ray reverberation.\u00a0<\/p>\n In 2009, her thesis advisor, Andy Fabian, and his team were looking through archival data from an X-ray telescope and noticed curious time delays in signals coming from around a black hole. They interpreted the signals as X-ray echoes, or reverberations. It was the first evidence of X-ray echoes around a black hole, and it helped to resolve a debate in the field over the source of the radiation.\u00a0<\/p>\n Her advisor determined that the reverb was a result of X-rays generated from the black hole\u2019s corona \u2014 a crown-shaped aura of high-energy radiation immediately surrounding the black hole \u2014 that then bounced, or reverberated, off the swirling disk of gas and dust that circles a black hole, known as an accretion disk.\u00a0<\/p>\n \u201cThey had only found these echoes in one black hole. But the archive was full of data of these reverberation signals that no one had analyzed in this particular way,\u201d Kara explains.\u00a0\u201cSo I had my whole PhD to kind of play with this archive, and it felt very discovery-driven.\u201d<\/p>\n Since that initial exploration, Kara has worked to advance the study of X-ray reverberation as a technique to map regions around black holes and other extreme astrophysical objects.\u00a0<\/p>\n A pivotal disruption<\/strong><\/p>\n After earning a PhD in physics, Kara returned to the U.S. for postdoctoral work at the University of Maryland and NASA\u2019s Goddard Space Flight Center. She intended to work on data from a new satellite, Hitomi \u2014 a Japanese mission that would detect far-off X-rays to help scientists map the large-scale structure and evolution of the universe.\u00a0After 40 days, the scientists lost control of the satellite, which ultimately began spinning uncontrollably\u00a0and broke apart in orbit. Before it failed, the telescope sent back one clean signal.<\/p>\n \u201cIt got one really good observation, which was unlike any spectrum we had ever seen before,\u201d Kara recalls.\u00a0<\/p>\n The data confirmed that the satellite\u2019s detector \u2014 a microcalorimeter that was developed at NASA \u2014 was sound. That technology is now at the heart of Hitomi\u2019s successor, the X-ray Imaging and Spectroscopy Mission, or XRISM, which has been successfully taking data since its launch in 2023. Today, Kara leads a science group as part of the XRISM mission to analyze X-ray signals from supermassive black holes.\u00a0<\/p>\n Back then, however, with the end of Hitomi, she had to pivot. She started working with a new group at NASA Goddard that was gearing up for the launch of another telescope \u2014 the Neutron Star Interior Composition Explorer, or NICER. In 2017, the telescope, which was developed and built by MIT researchers, was launched and attached to the International Space Station, where it measured the timing of incoming X-rays from astrophysical sources in deep space.\u00a0<\/p>\n The group Kara joined was analyzing NICER data for signs of tidal disruption events, which are instances when a black hole tears apart a nearby star. This was some of her earliest work on these dynamic sources, and she has since incorporated tidal disruption events \u2014 and data from NICER \u2014 as a main research area.\u00a0<\/p>\n At the hub<\/strong><\/p>\n In 2019, Kara accepted a junior faculty position in MIT\u2019s Department of Physics \u2014 a decision that to her was a \u201cno-brainer.\u201d\u00a0<\/p>\n \u201cX-ray astronomy has its history at MIT,\u201d Kara says. \u201cBruno Rossi, Hale Bradt, George Clark, Claude Canizares \u2014 it all started here. It was always a place that felt like a hub. And that was the draw.\u201d<\/p>\n Today, she and her students regularly analyze data from various satellites and telescopes such as XRISM and NICER to better understand black holes and how they grow, evolve, and affect the galaxies around them. She continues to advance X-ray reverberation mapping, which has helped scientists map the extreme regions immediately surrounding a black hole. Her group is also studying signals from other extreme X-ray sources, including tidal disruption events, quasiperiodic eruptions, and galactic black hole outbursts.\u00a0<\/p>\n Kara also plans to explore data from future observatories, including the Ultraviolet Transiet Astronomy Satellite (ULTRASAT), which will continuously scan the entire sky for hot, ultraviolet sources; and the Laser Interferometer Space Antenna (LISA), a space telescope that will detect low-frequency gravitational waves from sources such as pairs of lopsided, David-and-Goliath black holes.\u00a0<\/p>\n And she\u2019s also found time for a bit of black hole fun: In 2022, Kara collaborated with educators and music anthropologists at MIT to convert a black hole\u2019s X-ray echoes to audible sound. As a musician herself \u2014 she sings and plays the violin \u2014 she was curious how a black hole\u2019s cosmic energy might \u201csound.\u201d The\u00a0effect<\/a> was otherworldly, to say the least.\u00a0<\/p>\n \u201cOne of the reasons that I love black holes is that they are very extreme, and feel very sci-fi crazy, and things don\u2019t make sense, and physics breaks down around them. And at the same time, they\u2019re super foundational to even why we\u2019re here,\u201d Kara says. \u201cFor reasons we don\u2019t fully understand, the distribution of stars and gas and dust in a galaxy is dictated in part by the supermassive black hole at its center. Our sun is one of those stars. It\u2019s all intertwined. And untangling some of that is what motivates me.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"Black holes are often misunderstood to be just that: dark and mysterious voids that are somehow akin to…\n","protected":false},"author":2,"featured_media":554668,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_share_on_mastodon":"0"},"categories":[270],"tags":[237431,1016,18,237429,35418,24140,19,17,106263,38045,237430,133,451,52410],"class_list":["post-554667","post","type-post","status-publish","format-standard","has-post-thumbnail","category-space","tag-accretion-disk-physics","tag-black-holes","tag-eire","tag-erin-kara","tag-galaxy-formation","tag-gravitational-waves","tag-ie","tag-ireland","tag-mit-kavli-institute","tag-mit-physics","tag-nicer","tag-science","tag-space","tag-x-ray-astronomy"],"share_on_mastodon":{"url":"https:\/\/pubeurope.com\/@ie\/116814647297526906","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/554667","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/comments?post=554667"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/554667\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/554668"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=554667"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=554667"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=554667"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}