{"id":41834,"date":"2025-09-03T23:02:09","date_gmt":"2025-09-03T23:02:09","guid":{"rendered":"https:\/\/www.europesays.com\/ie\/41834\/"},"modified":"2025-09-03T23:02:09","modified_gmt":"2025-09-03T23:02:09","slug":"uah-researchers-use-x-rays-from-quasars-to-answer-one-of-the-three-major-questions-in-cosmology-where-are-the-missing-baryons","status":"publish","type":"post","link":"https:\/\/www.europesays.com\/ie\/41834\/","title":{"rendered":"UAH researchers use X-rays from quasars to answer one of the three major questions in cosmology: where are the missing baryons?"},"content":{"rendered":"

\n\t\t\t\t\t\t\t\t\t\tBYLINE:<\/strong> Russ Nelson\t\t\t\t\t\t\t\t\t\t<\/p>\n

Researchers at The University of Alabama in Huntsville (UAH), a part of The University of Alabama System, have published a series of two papers<\/a> in the Monthly Notices of the Royal Astronomical Society<\/a> that resolve one of three major outstanding puzzles in cosmology: the \u201cmissing baryon problem,\u201d a discrepancy between the amount of baryonic matter detected from shortly after the Big Bang when compared with recent epochs. Dr. Massimiliano \u201cMax\u201d Bonamente, a professor of physics and astronomy, along with Dr. David Spence and international colleagues, used X-ray radiation from quasars to determine the \u201cmissing\u201d particles reside in the warm-hot intergalactic medium, or WHIM, a state of matter characterized by low density and high temperatures.<\/p>\n

\u201cThis is the result of over 10 years of work at UAH, primarily by myself and a recent graduate of ours, David Spence, also in collaboration with several scientists worldwide,\u201d Bonamente says. \u201cWith three major problems in modern cosmology \u2013 missing baryons, identification of dark matter, identification of dark energy \u2013 it’s case closed on the first.\u201d<\/p>\n

Baryons are subatomic particles, most commonly protons and neutrons, that comprise the bulk of visible matter in the universe. The WHIM is a crucial component of the cosmic web<\/a>, the large-scale structure of the universe composed of enormous filaments of dark matter and gas that connect galaxies to one another.<\/p>\n

\u201cThe universe is believed to start off as a \u2018ball of fire,\u2019 the Big Bang; it then cools and forms structures on various scales: stars, galaxies, filaments of galaxies,\u201d Bonamente notes. \u201cThe gas is attracted by the gravity of these filaments that stretch hundreds of millions of light-years, and the gas heats back up as it falls towards the WHIM. This is something any graduate student in physics would learn in their classical dynamics course, so astronomers were confident in this simple picture.\u201d<\/p>\n

Current observations suggest baryons make up about five percent of the total energy density of the universe. Yet, a significant fraction of present-day baryons remained unaccounted for in deep far-ultraviolet (FUV) searches. A census of baryons in the recent observable universe found that the observed baryonic matter accounts for about one half the expected amount.<\/p>\n

\u201cThe location of the missing baryons near these WHIM structures was proposed back in 1999 in a seminal paper by Princeton scientists, and then consistently seen ever since in all subsequent simulations,\u201d the researcher says. \u201cBut simulations aren\u2019t real, and we needed to look in the real, uppercase Universe.\u201d<\/p>\n

To accomplish this, Bonamente, Spence and their colleagues analyzed X-ray sources from the European Space Agency\u2019s<\/a> orbiting X-ray telescope XMM-Newton<\/a> and NASA\u2019s Chandra Observatory<\/a> to augment the FUV findings to make the breakthrough.<\/p>\n

The core of the discovery lies in studying the cosmological density of missing baryons by analyzing X-ray absorption lines in quasars, focusing on the warm-hot intergalactic medium. In quasars, X-ray absorption lines arise when X-rays emitted from the quasar’s central black hole pass through intervening gas clouds, either within the quasar’s host galaxy or even farther away in the intergalactic medium<\/p>\n

Staying grounded<\/p>\n

The study made a systematic search for the absorption lines of highly ionized oxygen atoms in the spectra of 51 XMM-Newton and Chandra background quasars. These show up as \u201cdark lines\u201d in the X-ray spectrum, created when specific wavelengths are absorbed by atoms in the gas. By learning the properties of these absorption lines, like their strength and velocity, astronomers can learn about the physical conditions and amount of the absorbing gas.<\/p>\n

\u201cFor nearly 20 years, astronomers used a single source \u2013 or a few at most \u2013 to study this effect. This results in a strong bias of results, and the problem that one source (or few) are not representative of the whole universe,\u201d Bonamente notes. \u201cSo, we wanted to amend that problem, and the only way to do it is to go \u2018big\u2019 with the largest sample we could come up with. Statistics demands a large sample in order to make the best possible estimates, so we did just that.\u201d<\/p>\n

The results of this analysis contributes to the characterization of the missing baryons, indicating they are associated with the high\u2013temperature portion of the WHIM, and possibly with large-scale WHIM filaments traced by galaxies, as predicted by numerical simulations and by other independent probes.<\/p>\n

\u201cIt is only in X-rays that the relevant absorption lines occur,\u201d Bonamente says. \u201cThis is something that is dictated by the atomic structures. The calculations of the wavelengths where the absorption lines occur \u2013 precisely in X-rays \u2013 are reliable, and make use of standard quantum-mechanics calculations that have been confirmed in our laboratories. So, we had no other choice: hot gas at those temperatures are only \u2018visible\u2019 in X-rays.\u201d<\/p>\n

Looking to the future of this research, Bonamente says there are still plenty of questions to answer.<\/p>\n

\u201cThere is work to do to improve the characterization of the WHIM and the missing baryons,\u201d the researcher says. \u201cWhat is exactly the temperature of the WHIM? How do these baryons distribute in the cosmos \u2013 closer to galaxy clusters or more in the intergalactic space? Are they rich in \u2018metals\u2019 or mostly hydrogen and helium? Answers to these questions will reduce the error bars on our measurements.\u201d<\/p>\n

With regards to solving the big challenges in cosmology in general, Bonamente likes to take a well-grounded approach.<\/p>\n

\u201cThe other problems in cosmology are more speculative, in my opinion, and it may even be that there is no dark matter or dark energy after all. But it’s good to know that the ordinary matter is as it should be. Cosmologists \u2013 and many other scientists \u2013 like to look at headline-grabbing, but speculative topics such as dark energy, when in fact there are problems more down-to-earth \u2013 pun intended \u2013 that need to be solved first. Wouldn’t you want to make sure your shoelaces are tied before you run the 100 meters at the Olympics?\u201d<\/p>\n

Bonamente adds that an effort of this magnitude could not be done without the support of many other dedicated scientists who bought into the idea and shared in the hard work.<\/p>\n

\u201cThroughout the years, I\u2019ve had the good fortune of being surrounded by great colleagues who made this project happen,\u201d the researcher concludes. \u201cIt\u2019s my pleasure to thank and acknowledge Drs. Jussi Ahoranta and Kimmo Tuominen from Helsinki University, Dr. Natasha Wijers of Northwestern University and Dr. Jelle de Plaa of SRON Utrecht, who co-authored the papers describing these findings. And my good friend Dr. Jukka Nevalainen, who has also been a long-term collaborator on this and many other projects.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"BYLINE: Russ Nelson Researchers at The University of Alabama in Huntsville (UAH), a part of The University of…\n","protected":false},"author":2,"featured_media":41835,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[77],"tags":[18,19,17,941,133],"class_list":{"0":"post-41834","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-science","8":"tag-eire","9":"tag-ie","10":"tag-ireland","11":"tag-newswise","12":"tag-science"},"share_on_mastodon":{"url":"","error":""},"_links":{"self":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/41834","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=41834"}],"version-history":[{"count":0,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/posts\/41834\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media\/41835"}],"wp:attachment":[{"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/media?parent=41834"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/categories?post=41834"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.europesays.com\/ie\/wp-json\/wp\/v2\/tags?post=41834"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}