Daily Junction.mobi portal<figure class="align-center "> <img alt="" src="https://images.theconversation.com/files/749510/original/file-20260722-57-jsx6bc.jpg?ixlib=rb-4.1.1&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/749510/original/file-20260722-57-jsx6bc.jpg?ixlib=rb-4.1.1&q=45&auto=format&w=600&h=558&fit=crop&dpr=1 600w, https://images.theconversation.com/files/749510/original/file-20260722-57-jsx6bc.jpg?ixlib=rb-4.1.1&q=30&auto=format&w=600&h=558&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/749510/original/file-20260722-57-jsx6bc.jpg?ixlib=rb-4.1.1&q=15&auto=format&w=600&h=558&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/749510/original/file-20260722-57-jsx6bc.jpg?ixlib=rb-4.1.1&q=45&auto=format&w=754&h=701&fit=crop&dpr=1 754w, https://images.theconversation.com/files/749510/original/file-20260722-57-jsx6bc.jpg?ixlib=rb-4.1.1&q=30&auto=format&w=754&h=701&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/749510/original/file-20260722-57-jsx6bc.jpg?ixlib=rb-4.1.1&q=15&auto=format&w=754&h=701&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"> <figcaption> <span class="caption">The bright dot of a Type Ia supernova (supernova 1994D) appears next to galaxy NGC 4526.</span> <span class="attribution"><a class="source" href="https://esahubble.org/images/opo9919i/">Nasa, Esa, The Hubble Key Project Team, and The High-Z Supernova Search Team</a></span> </figcaption> </figure>
<p>Secondly, the 2025 analysis relied on a flawed proxy, incorrectly assuming that the overall age of a host galaxy is identical to the specific age of the star that exploded. But galaxies are not uniform like this: even large, ancient galaxies contain localised pockets of young stars.</p>
<p>By overestimating the difference in age between the stars that explode nearby and those that explode in the distant universe, by a factor of three to five, the Yonsei University study overestimated the amount by which the age-brightness calibration could bias supernova distance measurements.</p>
<p>Once these omissions were corrected, the data behaved as expected under the standard model of cosmology. As such, evidence for an accelerating universe remains secure.</p>
<h2>Science friction</h2>
<p>While the 2025 study turned out to be incorrect, the challenge it posed was valuable. Challenging accepted ideas and rigorously testing our observations is fundamental to scientific progress.</p>
<p>Their claims provided an opportunity for cosmology teams to return to their baseline data, interrogate their core assumptions, and test different ways of calibrating the measurements. When measuring distances, however, the age effect and the mass effect are highly correlated, and therefore we (the Southampton team) believe it is incorrect to make a full age-based adjustment to distances that have already been corrected for the mass effect.</p>
<p>The Southampton team was invited, among others, to a workshop at Yonsei in June 2026, where we discussed our methods and talked about ways to include both stellar mass and stellar ages into the brightness corrections.</p>
<p>In a follow up study, recently accepted by MNRAS, the Yonsei University team maintain that the ages of stars have an important effect on the supernovae they produce. They say that two methods used in earlier studies have suppressed the importance of this phenomenon.</p>
<p>When these effects are accounted for consistently, they explain, it leads to results similar to those in the 2025 study. “We therefore continue to find evidence that stellar-population age is an important factor in Type Ia supernova standardisation,” authors Junhyuk Son and Hyejeon Cho, told The Conversation. </p>
<p>“Because the typical ages of supernova host populations change with cosmic time, understanding this effect is important for precision measurements of the Universe’s expansion history.”</p>
<p>Future measurements will depend on understanding supernova explosions better. It is a job we hope the community can take on together. But none of this removes the need for dark energy: it is still there, and still unexplained.</p>
<p>Ultimately, we have shown that existing measurements of dark energy are robust. Rather than debating whether cosmic acceleration exists, the astrophysical community can return to the exciting task of figuring out what dark energy actually is and how we best measure it.</p>
<p>Over the next 10 years, the Vera C. Rubin Observatory in Chile will carry out a project known as the <a href="https://rubinobservatory.org/explore/how-rubin-works/lsst">Legacy Survey of Space and Time</a>, which will produce a sample of supernovae 20 times larger than the DES sample used in our analysis. There is no better time to be investigating the mysteries of dark energy.<!-- Below is The Conversation's page counter tag. Please DO NOT REMOVE. --><img src="https://counter.theconversation.com/content/285748/count.gif?distributor=republish-lightbox-basic" alt="The Conversation" width="1" height="1" style="border: none !important; box-shadow: none !important; margin: 0 !important; max-height: 1px !important; max-width: 1px !important; min-height: 1px !important; min-width: 1px !important; opacity: 0 !important; outline: none !important; padding: 0 !important" referrerpolicy="no-referrer-when-downgrade" /><!-- End of code. If you don't see any code above, please get new code from the Advanced tab after you click the republish button. The page counter does not collect any personal data. More info: https://theconversation.com/republishing-guidelines --></p>
<p><span><a href="https://theconversation.com/profiles/phil-wiseman-1513455">Phil Wiseman</a>, Ernest Rutherford Fellow, <em><a href="https://theconversation.com/institutions/university-of-southampton-1093">University of Southampton</a></em> and <a href="https://theconversation.com/profiles/mark-sullivan-164795">Mark Sullivan</a>, Professor, <em><a href="https://theconversation.com/institutions/university-of-southampton-1093">University of Southampton</a></em></span></p>
<p>This article is republished from <a href="https://theconversation.com">The Conversation</a> under a Creative Commons license. Read the <a href="https://theconversation.com/the-death-of-dark-energy-is-a-false-alarm-the-universe-is-still-accelerating-285748">original article</a>.</p> </div>