Hubble tension Archives

September 15, 2024September 15, 2024 by Matt Williams

Early Dark Energy Could Resolve Two of the Biggest Mysteries in Cosmology

This is a small portion of the field observed by NASA’s James Webb Space Telescope’s NIRCam (Near-Infrared Camera) for the Cosmic Evolution Early Release Science (CEERS) survey. It is filled with galaxies. The light from some of them has traveled for over 13 billion years to reach the telescope. Credit: NASA, ESA, CSA, Steve Finkelstein (University of Texas at Austin)

Of all the mysteries facing astronomers and cosmologists today, the “Hubble Tension” remains persistent! This term refers to the apparent inconsistency of the Universe’s expansion (aka. the Hubble Constant) when local measurements are compared to those of the Cosmic Microwave Background (CMB). Astronomers hoped that observations of the earliest galaxies in the Universe by the James Webb Space Telescope (JWST) would solve this mystery. Unfortunately, Webb confirmed that the previous measurements were correct, so the “tension” endures.

Since the JWST made its observations, numerous scientists have suggested that the existence of Early Dark Energy (EDE) might explain the Hubble Tension. In a recent study supported by NASA and the National Science Foundation (NSF), researchers from the Massachusetts Institute of Technology (MIT) suggested that EDE could resolve two cosmological mysteries. In addition to the Hubble Tension, it might explain why Webb observed as many galaxies as it did during the early Universe. According to current cosmological models, the Universe should have been much less populated at the time.

March 23, 2024March 23, 2024 by Scott Alan Johnston

Red Giants Offer a New Way to Measure Distance in the Universe

The Large Magellanic cloud. Credit: CTIO/NOIRLab/NSF/AURA/SMASH/D. Nidever (Montana State University) Image processing: Travis Rector (University of Alaska Anchorage), Mahdi Zamani & Davide de Martin.

For nearly three decades now, it’s been clear that the expansion of the Universe is speeding up. Some unknown quantity, dramatically dubbed ‘dark energy’, is pushing the Universe apart. But the rate at which the Universe’s expansion is increasing – called the Hubble Constant – hasn’t yet been nailed down to a single number.

Not for lack of trying.

March 15, 2024March 15, 2024 by Matt Williams

Webb Continues to Confirm That Universe is Behaving Strangely

Image of NGC 5468, a galaxy located about 130 million light-years from Earth, combines data from the Hubble and James Webb space telescopes. Credit: NASA/ESA/CSA/STScI/A. Riess (JHU/STScI)

Over a century ago, astronomers Edwin Hubble and Georges Lemaitre independently discovered that the Universe was expanding. Since then, scientists have attempted to measure the rate of expansion (known as the Hubble-Lemaitre Constant) to determine the origin, age, and ultimate fate of the Universe. This has proved very daunting, as ground-based telescopes yielded huge uncertainties, leading to age estimates of anywhere between 10 and 20 billion years! This disparity between these measurements, produced by different techniques, gave rise to what is known as the Hubble Tension.

It was hoped that the aptly named Hubble Space Telescope (launched in 1990) would resolve this tension by providing the deepest views of the Universe to date. After 34 years of continuous service, Hubble has managed to shrink the level of uncertainty but not eliminate it. This led some in the scientific community to suggest (as an Occam’s Razor solution) that Hubble‘s measurements were incorrect. But according to the latest data from the James Webb Space Telescope (JWST), Hubble’s successor, it appears that the venerable space telescope’s measurements were right all along.

February 12, 2024February 12, 2024 by Brian Koberlein

Measuring Distances in the Universe With Fast Radio Bursts

FAST catches a real pulse from FRB 121102. Credit: NAOC

Now and then there is a bright radio flash somewhere in the sky. It can last anywhere from a few milliseconds to a few seconds. They appear somewhat at random, and we still aren’t sure what they are. We call them fast radio bursts (FRBs). Right now the leading theory is that they are caused by highly magnetic neutron stars known as magnetars. With observatories such as CHIME we are now able to see lots of them, which could give astronomers a new way to measure the rate of cosmic expansion.

January 16, 2024January 16, 2024 by Brian Koberlein

Astronomers Rule Out One Explanation for the Hubble Tension

One of the brightest Cepheid variable stars, RS Puppis. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-Hubble/Europe Collaboration

Perhaps the greatest and most frustrating mystery in cosmology is the Hubble tension problem. Put simply, all the observational evidence we have points to a Universe that began in a hot, dense state, and then expanded at an ever-increasing rate to become the Universe we see today. Every measurement of that expansion agrees with this, but where they don’t agree is on what that rate exactly is. We can measure expansion in lots of different ways, and while they are in the same general ballpark, their uncertainties are so small now that they don’t overlap. There is no value for the Hubble parameter that falls within the uncertainty of all measurements, hence the problem.

November 11, 2023November 11, 2023 by Brian Koberlein

If You Account for the Laniakea Supercluster, The Hubble Tension Might Be Even Larger

Illustration of the Laniakea Supercluster. Credit: Andrew Z. Colvin

One of the great unsolved mysteries of cosmology is known as the Hubble tension. It stems from our inability to pin down the precise rate of cosmic expansion. There are several ways to calculate this expansion, from observing distant supernovae to measuring the Doppler shift of maser light near supermassive black holes, and they all give slightly different results. Maybe we don’t fully understand the structure of the Universe, or maybe our view of the heavens is biased given that we are located deep within a galactic supercluster. As a new study shows, the bias problem is even worse than we thought.

October 6, 2023October 6, 2023 by Matt Williams

Colliding Neutron Stars Could Help Measure the Expansion of the Universe

Artist's impression of two neutron stars colliding, known as a "kilonova" event. Credits: Elizabeth Wheatley (STScI)

According to some in the astrophysical community, there has been something of a “Crisis in Cosmology” in recent years. Though astronomers are all aware that the Universe is in a state of expansion, there has been some inconsistency when measuring the rate of it (aka. the Hubble Constant). This issue arises from the Cosmic Distance Ladder, where astronomers use different methods to measure relative distances over longer scales. This includes making local distance estimates using parallax measurements, nearby variable stars, and supernovae (“standard candles”).

They also conduct redshift measurements of the Cosmic Microwave Background (CMB), the relic radiation left over from the Big Bang, to determine cosmological distances. The discrepancy between these two methods is known as the “Hubble Tension,” and astronomers are eager to resolve it. In a recent study, an international team of astrophysicists from the Niels Bohr Institute suggested a novel method for measuring cosmic expansion. They argue that by observing colliding neutron stars (kilonovae), astronomers can relieve the tension and obtain consistent measurements of the Hubble Constant.

September 4, 2023September 4, 2023 by Brian Koberlein

It's Going to Take More Than Early Dark Energy to Resolve the Hubble Tension

Artist impression of a cluster of galaxies in the early Universe. Credit: S. Dagnello; NSF/NRAO/AUI

Our best understanding of the Universe is rooted in a cosmological model known as LCDM. The CDM stands for Cold Dark Matter, where most of the matter in the universe isn’t stars and planets, but a strange form of matter that is dark and nearly invisible. The L, or Lambda, represents dark energy. It is the symbol used in the equations of general relativity to describe the Hubble parameter, or the rate of cosmic expansion. Although the LCDM model matches our observations incredibly well, it isn’t perfect. And the more data we gather on the early Universe, the less perfect it seems to be.

August 4, 2023August 4, 2023 by Brian Koberlein

JWST is the Perfect Machine to Resolve the Hubble Tension

The cosmic distance ladder sets the scale of the universe. Credit: NASA/JPL-Caltech

You’ve just found the perfect work desk at a garage sale, and you measure it to see if it will fit in your apartment. You brought a tape measure to size it up and find it’s 180 cm. Perfect. But your friend also brought a tape measure, and they find it’s 182 cm, which would be a smidge too long. You don’t know which tape measure is right, so you have a conundrum. Astronomers also have a conundrum, and it’s known as the Hubble tension.

April 19, 2023April 19, 2023 by Matt Williams

The First Light in the Universe Helps Build a Dark Matter Map

A view of Stephan’s Quintet, a visual grouping of five galaxies from the James Webb Telescope. Credit: NASA/ESA/CSA/STScI

In the 1960s, astronomers began noticing a pervasive microwave background visible in all directions. Thereafter known as the Cosmic Microwave Background (CMB), the existence of this relic radiation confirmed the Big Bang theory, which posits that all matter was condensed onto a single point of infinite density and extreme heat that began expanding ca. 13.8 years ago. By measuring the CMB for redshift and comparing these to local distance measurements (using variable stars and supernovae), astronomers have sought to measure the rate at which the Universe is expanding.

Around the same time, scientists observed that the rotational curves of galaxies were much higher than their visible mass suggested. This meant that either Einstein’s Theory of General Relativity was wrong or the Universe was filled with a mysterious, invisible mass. In a new series of papers, members of the Atacama Cosmology Telescope (ACT) collaboration have used background light from the CMB to create a new map of Dark Matter distribution that covers a quarter of the sky and extends deep into the cosmos. This map confirms General Relativity and its predictions for how mass alters the curvature of spacetime.