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A new study suggests a way to find them using gravity as a detection tool and a telescope originally designed for other purposes.<\/p>\n
Hidden stellar corpses<\/p>\n
The research was led by Zofia Kaczmarek at Heidelberg University<\/a> in Germany. The study predicts this missing population could finally come into view.<\/p>\n The forecast hinges on an upcoming NASA observatory<\/a> that has not yet launched.<\/p>\n Neutron stars are the crushed cores that are left behind when massive stars collapse. <\/p>\n Each one packs more mass than the Sun into a sphere the size of a city, putting them among the densest objects in nature.<\/p>\n Most of the unconfirmed objects give off no radio pulses, no X-ray glow, and no signal easily picked up by a telescope. They drift through the galaxy<\/a> entirely unannounced.<\/p>\n \u201cMost neutron stars are relatively dim and on their own. They are incredibly hard to spot without some sort of help,\u201d Kaczmarek said. <\/p>\n Starlight that bends<\/p>\n The trick depends on microlensing, a small gravitational effect first predicted by Einstein. <\/p>\n When a massive object drifts in front of a distant star, its gravity warps spacetime and bends the background star\u2019s light around it.<\/p>\n From a telescope\u2019s<\/a> view, the distant star briefly appears brighter and slightly displaced. <\/p>\n Many can pick up the brightening, but far fewer can detect the tiny positional wobble that comes with it.<\/p>\n The same approach revealed the first confirmed isolated black hole in 2022, in a paper<\/a> that weighed an otherwise invisible compact object. <\/p>\n Until then, there was no method to confirm what these dark lenses really were.<\/p>\n Weighing dark objects<\/p>\n Because neutron stars are heavy, they bend light more than lighter objects. The size of the positional wobble scales with mass. <\/p>\n Greater mass produces a larger wobble. When the wobble is measured, the unseen object can be weighed. That detail is unusually powerful. <\/p>\n So far, astronomers have only weighed neutron stars in binary pairs, where an orbiting partner gives them a reference point. Single, drifting neutron stars<\/a> have never had their masses measured.<\/p>\n \u201cWhat\u2019s really cool about using microlensing is that you can get direct mass measurements,\u201d said Peter McGill of Lawrence Livermore National Laboratory (LLNL<\/a>).<\/p>\n The technique opens a window onto isolated neutron stars that no other method can reach.<\/p>\n Roman\u2019s hidden talent<\/p>\n That\u2019s where the Roman Space Telescope enters the picture. The flagship NASA observatory was built primarily to hunt for exoplanets and chart dark energy.<\/p>\n Its precision makes it unusually good at detecting the tiny positional wobbles that betray a passing dark mass. <\/p>\n Roman can measure both the brightening and the wobble of a lensed star with rare accuracy.<\/p>\n The mission\u2019s main microlensing campaign, the Galactic Bulge Time Domain Survey, will monitor millions of stars near the galaxy\u2019s center at 12-minute intervals. <\/p>\n The cadence was designed for finding planets<\/a>, but it works equally well for catching drifting neutron stars.<\/p>\n Isolating neutron star candidates<\/p>\n The novel piece of the analysis came from what the simulations revealed. Until this study, no one had a clean way to separate isolated neutron stars from the broader microlensing crowd.<\/p>\n When the team mapped simulated events by duration and wobble size, neutron stars clustered in a distinctive spur, clearly separate from the rest. <\/p>\n The feature only appears when both signals are measured together. A signature in plain view.<\/p>\n Within the spur sit fast-moving neutron stars that are unusually likely to produce a clean lensing signal.<\/p>\n Selecting the spur should yield a high-purity sample of isolated neutron star candidates.<\/p>\n Kicks from supernovas<\/p>\n Neutron stars don\u2019t form gently. The supernova explosion that creates one is never perfectly symmetric. The imbalance shoves the new neutron star sideways, hard and fast.<\/p>\n These natal kicks can send a star hurtling at hundreds of miles per second. Astronomers have long suspected<\/a> average kicks fall between 60 and 300 miles per second.<\/p>\n Roman\u2019s catalog could prove that. The team\u2019s simulations show the spur looks different depending on how strong the kicks are. <\/p>\n Measuring the spread of detected neutron stars would let researchers test competing supernova models against data.<\/p>\n What Roman may reveal<\/p>\n The forecast offers a concrete prediction. Once Roman starts surveying, the team expects to spot roughly 100 isolated neutron stars. <\/p>\n Their brightness changes and positional wobble are both measurable, allowing researchers to calculate their masses from the lensing data.<\/p>\n That would be a first. No isolated neutron star has had its mass measured before, and even one example would let astronomers test where the boundary between neutron stars and black holes really lies.<\/p>\n The simulations also show the survey\u2019s lower-cadence \u201cgap-filling\u201d observations are critical. <\/p>\n Skipping them would drop the detectable event yield by about 38 percent. Roman is set to launch in late 2026.<\/p>\n The study is published in the journal Astronomy & Astrophysics<\/a>.<\/p>\n \u2014\u2013<\/p>\n Like what you read? Subscribe to our newsletter<\/a> for engaging articles, exclusive content, and the latest updates.<\/p>\n Check us out on EarthSnap<\/a>, a free app brought to you by Eric Ralls<\/a> and Earth.com.<\/p>\n \u2014\u2013<\/p>\n","protected":false},"excerpt":{"rendered":"The Milky Way is thought to contain tens of millions of dead stellar remnants, perhaps hundreds of millions.…\n","protected":false},"author":2,"featured_media":443147,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[23],"tags":[111,139,69,147,392],"class_list":["post-443146","post","type-post","status-publish","format-standard","has-post-thumbnail","category-space","tag-new-zealand","tag-newzealand","tag-nz","tag-science","tag-space"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/443146","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=443146"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/443146\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/443147"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=443146"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=443146"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=443146"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}