The universe is probably not rushing up in any case. In accordance with a brand new examine, its growth might truly be slowing down, difficult one in all fashionable cosmology’s most elementary concepts.
The findings, printed November 6 in Month-to-month Notices of the Royal Astronomical Society, query the long-accepted perception {that a} mysterious drive referred to as “darkish power” is pushing galaxies aside at an ever-increasing price. As a substitute, researchers discovered no convincing proof that the universe continues to be accelerating.
If confirmed, the outcomes might reshape scientists’ understanding of darkish power, assist resolve the long-standing “Hubble rigidity,” and remodel theories concerning the universe’s previous and future.
Proof for a Cosmic Slowdown
Lead researcher Professor Younger-Wook Lee of Yonsei College in South Korea mentioned, “Our examine exhibits that the universe has already entered a section of decelerated growth at present epoch and that darkish power evolves with time far more quickly than beforehand thought.
“If these outcomes are confirmed, it might mark a serious paradigm shift in cosmology for the reason that discovery of darkish power 27 years in the past.”
For almost three many years, astronomers have believed that the universe’s growth was accelerating attributable to darkish power, a mysterious drive appearing as a type of “anti-gravity.” This conclusion was initially based mostly on measurements of distant kind Ia supernovae, a discovery that earned the 2011 Nobel Prize in Physics.
Rethinking the Universe’s “Customary Candles”
The brand new analysis from Yonsei College challenges that basis. Sort Ia supernovae, lengthy thought-about dependable “customary candles” for measuring cosmic distances, seem like influenced by the age of the celebrities that create them.
Even after standardizing their brightness, the group discovered that supernovae originating from youthful stars are inclined to look fainter, whereas these from older stars seem brighter. Analyzing information from 300 host galaxies, the researchers confirmed this age impact with a unprecedented stage of confidence (99.999%).
Which means that a part of the dimming as soon as attributed to cosmic acceleration might truly outcome from stellar inhabitants variations moderately than common growth.
A New Mannequin Emerges
When the group corrected for this age-related bias, the supernova information not match the usual ΛCDM mannequin, which assumes a relentless type of darkish power. As a substitute, it matched extra carefully with a more recent mannequin supported by the Darkish Vitality Spectroscopic Instrument (DESI) mission.
This different mannequin attracts on baryonic acoustic oscillations (BAO) — basically historical sound waves from the Massive Bang — and information from the cosmic microwave background (CMB). Each sources recommend that darkish power isn’t fixed however as an alternative weakens and adjustments over time.
When researchers mixed the corrected supernova information with BAO and CMB outcomes, the proof turned overwhelming: the universe doesn’t seem like accelerating anymore, however has entered a section of decelerated growth.
A Universe Already Slowing
Professor Lee defined, “Within the DESI mission, the important thing outcomes had been obtained by combining uncorrected supernova information with baryonic acoustic oscillations measurements, resulting in the conclusion that whereas the universe will decelerate sooner or later, it’s nonetheless accelerating at current.
“Against this, our evaluation — which applies the age-bias correction — exhibits that the universe has already entered a decelerating section at this time. Remarkably, this agrees with what’s independently predicted from BAO-only or BAO+CMB analyses, although this truth has acquired little consideration up to now.”
Testing the Findings
To strengthen their conclusions, the Yonsei group is performing what they name an “evolution-free take a look at.” This strategy examines solely supernovae from younger, coeval galaxies — these with stars of comparable ages — throughout the whole redshift vary. Early outcomes already help the primary discovering.
“Throughout the subsequent 5 years, with the Vera C. Rubin Observatory discovering greater than 20,000 new supernova host galaxies, exact age measurements will enable for a much more sturdy and definitive take a look at of supernova cosmology,” mentioned analysis professor Chul Chung, a co-lead writer of the examine, together with PhD candidate Junhyuk Son.
The Vera C. Rubin Observatory and the Way forward for Cosmology
Situated excessive within the Chilean Andes, the Vera C. Rubin Observatory homes the world’s strongest digital digital camera. Having begun scientific operations this yr, it’s anticipated to revolutionize our understanding of each the photo voltaic system and the broader universe.
After the Massive Bang, roughly 13.8 billion years in the past, the universe expanded quickly earlier than gravity slowed it down. Then, round 9 billion years after its beginning, scientists found that growth had begun rushing up once more. This was attributed to darkish power, which is believed to make up about 70 p.c of the universe.
Darkish Vitality’s Thriller Deepens
Regardless of many years of examine, darkish power stays one in all science’s most puzzling enigmas. Final yr, information from DESI in Tucson, Arizona hinted that the affect of darkish power might need modified over time, an thought now gaining traction with the Yonsei group’s new outcomes.
With superior devices like DESI and the Vera C. Rubin Observatory, astronomers hope to lastly uncover what darkish power actually is — and the way it shapes the destiny of the universe.
