Have we been measuring the Universe unsuitable this complete time? New discovery may clear up an enormous cosmic thriller

It’s not simple measuring distances within the Universe, however astronomers have a couple of methods of getting round the issue.

One manner is by observing exploding stars often called supernovae, and specifically a sort of supernova often called a Type Ia supernova.

The thought is that these stellar explosions at all times glow with the identical brightness, so astronomers can observe how brilliant they seem from Earth, in contrast with how brilliant they really are, and thereby decide how distant they’re.

But recent proof exhibits supernovae aren’t the trusty yardsticks we thought, placing the usual mannequin of an accelerating, increasing Universe doubtful.

Dark vitality is the identify given to the truth that the growth of the Universe appears to be accelerating, not slowing down, and it is one of many largest mysteries in science.

But if we have been measuring the Universe unsuitable, does that imply the problem of darkish vitality lastly has an evidence?

Young-Wook Lee is the director of the Centre for Galaxy Evolution Research at Yonsei University, Seoul, South Korea.

We spoke to him a couple of research he carried out that exhibits the growth of the Universe could possibly be slowing down in spite of everything.

How do astronomers suppose the Universe is increasing?

Astronomers have lengthy believed the Universe is increasing at an accelerating fee, pushed by what we name ‘dark energy’.

This led to a mannequin often called Lambda chilly darkish matter (ΛCDM), by which the density of darkish vitality doesn’t fluctuate with time.

Then, 27 years in the past, a gaggle of scientists noticed distant supernovae – particularly Type Ia supernovae – and located they had been dimmer than anticipated.

This fitted the predictions of ΛCDM very properly, which is how we received the mannequin of the Universe we now have as we speak.

What did your group uncover?

Type Ia supernovae had been used to check ΛCDM as a result of they had been thought to blow up with an virtually equivalent intrinsic brightness, making them good reference objects.

Instead, we discovered that the brightness of Type Ia supernovae is strongly affected by the age of the celebrities they arrive from. 

After taking account of their age, supernovae from youthful populations of stars seem fainter and people from older stars seem brighter.

We discovered an especially excessive significance fee for our findings (over 99.9999999% confidence) in a pattern of over 300 galaxies.

This signifies that the dimming of supernovae doesn’t simply come up from cosmological results just like the acceleration of the Universe, but additionally from stellar astrophysics.

As a outcome, the info we collected not matches the ΛCDM mannequin. 

What various mannequin of the Universe does this level to?

Our knowledge factors to a mannequin of the Universe based mostly on ‘time-varying dark energy’, the place as a substitute of darkish vitality appearing in a set, fixed manner, its impacts fluctuate with time.

These fashions are additionally supported by knowledge from different tasks, just like the Dark Energy Spectroscopic Instrument (DESI). 

How did you make this discovery?

We began this challenge in 2010, when South Korea lacked its personal telescope.

We despatched two college students to Chile and Arizona to gather extraordinarily high-quality spectral knowledge of 60 galaxies.

Our challenge has since been prolonged to 300 host galaxies by using photometric age measurements.

This knowledge is sort of a fingerprint, giving astronomers an correct thought of the properties of an astronomical object, together with its composition. 

It was from this knowledge, and the well-established DESI mannequin, that we discovered that the age of the host galaxy impacts the brightness of supernovae inside it. 

What if the ΛCDM mannequin of growth is unsuitable?

The historical past of the Universe will change. Even the age of the Universe will change barely.

Interestingly, the way forward for the Universe will change too. It may probably result in a ‘big crunch’ state of affairs – which some cosmologists have mentioned based mostly on our outcome – the place the Universe collapses again right down to a singularity after ending its growth.

We can’t say for sure at this stage, nevertheless it’s sure that the Universe’s story shall be rewritten.

Why wasn’t this correction made earlier?

In most earlier research regarding these supernovae, the ages of the host galaxies weren’t instantly measured. Instead, they had been inferred not directly from the mass of the host galaxy.

This apply has develop into routine, however we’ve discovered that mass isn’t a dependable proxy for age, as a result of galaxies evolve very in a different way with redshift (or cosmic time).

By making use of a correction based mostly on instantly measured ages, relatively than on a proxy, we now have been in a position to present a dramatically completely different outcome for cosmology.

What’s subsequent?

We have a brilliant future forward, with the launch of telescopes just like the Vera Rubin Observatory, which South Korean astronomers are additionally members of.

It will uncover greater than 20,000 new supernovae host galaxies, and exact measurements will allow a extra definitive check of supernova cosmology.

This interview appeared within the January 2026 challenge of BBC Sky at Night Magazine