{"id":8691,"date":"2022-12-12T02:47:17","date_gmt":"2022-12-12T07:47:17","guid":{"rendered":"https:\/\/spaceandplanetarynewswire.com\/?p=8691"},"modified":"2022-12-12T02:47:18","modified_gmt":"2022-12-12T07:47:18","slug":"without-more-data-a-black-holes-origins-can-be-spun-in-any-direction","status":"publish","type":"post","link":"https:\/\/spaceandplanetarynewswire.com\/?p=8691","title":{"rendered":"Without More Data, a Black Hole\u2019s Origins Can Be \u201cSpun\u201d in Any Direction"},"content":{"rendered":"
Caption:An MIT study finds that, for now, the catalog of known black hole binaries does not reveal anything fundamental about how black holes form. Pictured is a simulation of the light emitted by a supermassive black hole binary system where the surrounding gas is optically thin (transparent). Credits:Credit: NASA\u2019s Goddard Space Flight Center<\/figcaption><\/figure>\n

Clues to a black hole\u2019s origins can be found in the way it spins. This is especially true for binaries, in which two black holes circle close together before merging. The spin and tilt of the respective black holes just before they merge can reveal whether the invisible giants arose from a quiet galactic disk or a more dynamic cluster of stars.<\/p>\n

Astronomers are hoping to tease out which of these origin stories is more likely by analyzing the 69 confirmed binaries detected to date. But a new study finds that for now, the current catalog of binaries is not enough to reveal anything fundamental about how black holes form.<\/p>\n

In a study<\/a> appearing today in the journal Astronomy and Astrophysics Letters, <\/em>MIT physicists show that when all the known binaries and their spins are worked into models of black hole formation, the conclusions can look very different, depending on the particular model used to interpret the data. <\/p>\n

A black hole\u2019s origins can therefore be \u201cspun\u201d in different ways, depending on a model\u2019s assumptions of how the universe works.<\/p>\n

\u201cWhen you change the model and make it more flexible or make different assumptions, you get a different answer about how black holes formed in the universe,\u201d says study co-author Sylvia Biscoveanu, an MIT graduate student working in the LIGO Laboratory. \u201cWe show that people need to be careful because we are not yet at the stage with our data where we can believe what the model tells us.\u201d<\/p>\n

The study\u2019s co-authors include Colm Talbot, an MIT postdoc; and Salvatore Vitale, an associate professor of physics and a member of the Kavli Institute of Astrophysics and Space Research at MIT.<\/p>\n

A tale of two origins<\/strong><\/p>\n

Black holes in binary systems are thought to arise via one of two paths. The first is through \u201cfield binary evolution,\u201d in which two stars evolve together and eventually explode in supernovae, leaving behind two black holes that continue circling in a binary system. In this scenario, the black holes should have relatively aligned spins, as they would have had time \u2014 first as stars, then black holes \u2014 to pull and tug each other into similar orientations. If a binary\u2019s black holes have roughly the same spin, scientists believe they must have evolved in a relatively quiet environment, such as a galactic disk.<\/p>\n

Black hole binaries can also form through \u201cdynamical assembly,\u201d where two black holes evolve separately, each with its own distinct tilt and spin. By some extreme astrophysical processes, the black holes are eventually brought together, close enough to form a binary system. Such a dynamical pairing would likely occur not in a quiet galactic disk, but in a more dense environment, such as a globular cluster, where the interaction of thousands of stars can knock two black holes together. If a binary\u2019s black holes have randomly oriented spins, they likely formed in a globular cluster.<\/p>\n

But what fraction of binaries form through one channel versus the other? The answer, astronomers believe, should lie in data, and particularly, measurements of black hole spins.<\/p>\n

To date, astronomers have derived the spins of black holes in 69 binaries, which have been discovered by a network of gravitational-wave detectors including LIGO in the U.S., and its Italian counterpart Virgo. Each detector listens for signs of gravitational waves \u2014 very subtle reverberations through space-time that are left over from extreme, astrophysical events such as the merging of massive black holes.<\/p>\n

With each binary detection, astronomers have estimated the respective black hole\u2019s properties, including their mass and spin. They have worked the spin measurements into a generally accepted model of black hole formation, and found signs that binaries could have both a preferred, aligned spin, as well as random spins. That is, the universe could produce binaries in both galactic disks and globular clusters.<\/p>\n

\u201cBut we wanted to know, do we have enough data to make this distinction?\u201d Biscoveanu says. \u201cAnd it turns out, things are messy and uncertain, and it\u2019s harder than it looks.\u201d<\/p>\n

Spinning the data<\/strong><\/p>\n

In their new study, the MIT team tested whether the same data would yield the same conclusions when worked into slightly different theoretical models of how black holes form.<\/p>\n

The team first reproduced LIGO\u2019s spin measurements in a widely used model of black hole formation. This model assumes that a fraction of binaries in the universe prefer to produce black holes with aligned spins, where the rest of the binaries have random spins. They found that the data appeared to agree with this model\u2019s assumptions and showed a peak where the model predicted there should be more black holes with similar spins.<\/p>\n

They then tweaked the model slightly, altering its assumptions such that it predicted a slightly different orientation of preferred black hole spins. When they worked the same data into this tweaked model, they found the data shifted to line up with the new predictions. The data also made similar shifts in 10 other models, each with a different assumption of how black holes prefer to spin.<\/p>\n

\u201cOur paper shows that your result depends entirely on how you model your astrophysics, rather than the data itself,\u201d Biscoveanu says.<\/p>\n

\u201cWe need more data than we thought, if we want to make a claim that is independent of the astrophysical assumptions we make,\u201d Vitale adds.<\/p>\n

Just how much more data will astronomers need? Vitale estimates that once the LIGO network starts back up in early 2023, the instruments will detect one new black hole binary every few days. Over the next year, that could add up to hundreds more measurements to add to the data.<\/p>\n

\u201cThe measurements of the spins we have now are very uncertain,\u201d Vitale says. \u201cBut as we build up a lot of them, we can gain better information. Then we can say, no matter the detail of my model, the data always tells me the same story \u2014 a story that we could then believe.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"

Clues to a black hole\u2019s origins can be found in the way it spins. This is especially true for binaries, in which two black holes circle close together before merging. The spin and tilt of the respective black holes just before they merge can reveal whether the invisible giants arose from a quiet galactic disk…<\/p>\n","protected":false},"author":71,"featured_media":8693,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"fifu_image_url":"https:\/\/news.mit.edu\/sites\/default\/files\/styles\/news_article__image_gallery\/public\/images\/202212\/MIT-Spin-Origins-01-press_0.jpg?itok=4X4dXZEL","fifu_image_alt":"Without More Data, a Black Hole\u2019s Origins Can Be \u201cSpun\u201d in Any Direction","footnotes":""},"categories":[207],"tags":[],"class_list":["post-8691","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research"],"_links":{"self":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts\/8691","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/users\/71"}],"replies":[{"embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=8691"}],"version-history":[{"count":1,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts\/8691\/revisions"}],"predecessor-version":[{"id":8692,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/posts\/8691\/revisions\/8692"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=\/wp\/v2\/media\/8693"}],"wp:attachment":[{"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=8691"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=8691"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/spaceandplanetarynewswire.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=8691"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}