Cosmology Archives

February 21, 2024February 21, 2024 by Carolyn Collins Petersen

A New, More Accurate Measurement for the Clumpiness of the Universe

Clusters of galaxies as observed by the eROSITA instrument. Colors indicate the redshift of the clusters, up to about 9 billion years of lookback time. Credit: MPE, J. Sanders for the eROSITA consortium. — Clusters of galaxies as observed by the eROSITA instrument. The idea is to determine the clumpiness (or distribution) of matter in the Universe. Colors indicate the redshift of the clusters, up to about 9 billion years of lookback time. Credit: MPE, J. Sanders for the eROSITA consortium.

Cosmologists are wrestling with an interesting question: how much clumpiness does the Universe have? There are competing but not compatible measurements of cosmic clumpiness and that introduces a “tension” between the differing measurements. It involves the amount and distribution of matter in the Universe. However, dark energy and neutrinos are also in the mix. Now, results from a recent large X-ray survey of galaxy clusters may help “ease the tension”.

February 16, 2024February 17, 2024 by Brian Koberlein

Euclid Begins its 6-Year Survey of the Dark Universe

The areas that the space telescope Euclid will observe. Credit: ESA/Euclid/Euclid Consortium

On July 1, 2023, the Euclid Spacecraft launched with a clear mission: to map the dark and distant Universe. To achieve that goal, over the next 6 years, Euclid will make 40,000 observations of the sky beyond the Milky Way. From this data astronomers will be able to map the positions of billions of galaxies, allowing astronomers to observe the effects of dark matter.

February 7, 2024February 7, 2024 by Carolyn Collins Petersen

How Does the Cosmic Web Drive Galaxy Evolution?

A computer simulation of what gas and stars in a galaxy cluster look like, and how they look embedded in the cosmic web. The assembly of galaxy clusters has implications for the clumpiness of the Universe throughout time. Credit: Yannick Bahé.

Galaxies experience a long strange trip through the cosmic web as they grow and evolve. It turns out that the neighborhoods they spend time in on the journey change their evolution, and that affects their star formation activity and alters their gas content.

February 7, 2024February 7, 2024 by Brian Koberlein

Dust Ruins Another Way of Measuring Distance in the Universe

A dusty spiral galaxy known as M66. Credit: NASA, ESA and the Hubble Heritage (STScI/AURA)-ESA/Hubble

Astronomers have many ways to measure the distance to galaxies billions of light years away, but most of them rely upon standard candles. These are astrophysical processes that have a brightness we can calibrate, such as Cepheid variable stars or Type Ia supernovae. Of course, all of these standard candles have some inherent variability, so astronomers also look for where our assumptions about them can lead us astray. As a case in point, a recent study in The Astrophysical Journal shows how galactic dust can bias distance observations.

January 18, 2024January 18, 2024 by Evan Gough

The JWST Solves the Mystery of Ancient Light

This image shows the galaxy EGSY8p7, a bright galaxy in the early Universe where light emission is seen from, among other things, excited hydrogen atoms — Lyman-alpha emission. The galaxy was identified in a field of young galaxies studied by Webb in the CEERS survey. In the bottom two panels, Webb’s high sensitivity picks out this distant galaxy along with its two companion galaxies, where previous observations saw only one larger galaxy in its place. This discovery of a cluster of interacting galaxies sheds light on the mystery of why the hydrogen emission from EGSY8p7, shrouded in neutral gas formed after the Big Bang, should be visible at all. Image Credit: ESA/Webb, NASA & CSA, S. Finkelstein (UT Austin), M. Bagley (UT Austin), R. Larson (UT Austin), A. Pagan (STScI), C. Witten, M. Zamani (ESA/Webb)

The very early Universe was a dark place. It was packed with light-blocking hydrogen and not much else. Only when the first stars switched on and began illuminating their surroundings with UV radiation did light begin its reign. That occurred during the Epoch of Reionization.

But before the Universe became well-lit, a specific and mysterious type of light pierced the darkness: Lyman-alpha emissions.

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.

January 9, 2024January 9, 2024 by Evan Gough

1,500 New Type 1A Supernova Found as Part of the Dark Energy Survey

An example of a supernova discovered by the Dark Energy Survey within the field covered by one of the individual detectors in the Dark Energy Camera. The supernova exploded in a spiral galaxy with redshift = 0.04528, which corresponds to a light-travel time of about 0.6 billion years. In comparison, the quasar at the right has a redshift of 3.979 and a light-travel time of 11.5 billion years. Image Credit: DES Collaboration/NOIRLab/NSF/AURA/M. Zamani

Supernova explosions are fascinating because they’re so cataclysmic, powerful, and awe-inspiring. They’re Nature’s summer blockbusters. Humans have recorded their existence in ancient astronomical records and stone carvings, and in our age, with telescopes.

Now, the Dark Energy Survey (DES) has uncovered the largest number of Type 1A supernovae ever found with a single telescope.

December 21, 2023December 21, 2023 by Evan Gough

Webb Sees a Supernova Go Off in a Gravitationally Lensed Galaxy – for the Second Time

NASA’s James Webb Space Telescope has spotted a multiply-imaged supernova in a distant galaxy designated MRG-M0138. Image Credit: NASA, ESA, CSA, STScI, Justin Pierel (STScI) and Andrew Newman (Carnegie Institution for Science).

Nature, in its infinite inventiveness, provides natural astronomical lenses that allow us to see objects beyond the normal reach of our telescopes. They’re called gravitational lenses, and a few years ago, the Hubble Space Telescope took advantage of one of them to spot a supernova explosion in a distant galaxy.

Now, the JWST has taken advantage of the same lens and found another supernova in the same galaxy.

December 11, 2023December 14, 2023 by Matt Williams

Why Was it Tricky to Know the Distances to Galaxies JWST Was Seeing?

Obtaining accurate redshift measurements is a challenge, even with telescopes like Webb. Credit: NASA

One of the chief objectives of the James Webb Space Telescope (JWST) is to study the formation and evolution of the earliest galaxies in the Universe, which emerged more than 13 billion years ago. To this end, scientists must identify galaxies from different cosmological epochs to explore how their properties have changed over time. This, in turn, requires precise dating techniques so astronomers are able to determine when (in the history of the Universe) an observed galaxy existed. The key is to measure the object’s redshift, which indicates how long its light has been traveling through space.

This is the purpose of the Cosmic Evolution Early Release Science Survey (CEERS), a collaborative research group that analyzes Webb data to learn more about galactic evolution. These galaxies are known as “high-redshift,” meaning that their light emissions are redshifted all the way into the infrared spectrum. Galaxies that existed ca. 13 billion years ago can only be observed in the near-infrared spectrum, which is now possible thanks to Webb’s Near-Infrared Camera (NIRCam). Even so, obtaining accurate redshift measurements from such distant galaxies is a very tricky, and requires advanced techniques.

December 8, 2023December 9, 2023 by Matt Williams

If Our Part of the Universe is Less Dense, Would That Explain the Hubble Tension?

Ten areas in the sky were selected as “deep fields” that the Dark Energy Camera imaged several times during the survey, providing a glimpse of distant galaxies and helping determine their 3D distribution in the cosmos. Credit: NSF/DES/NOIRLab/DOE/FNAL/AURA/University of Alaska Anchorage/

In the 1920s, Edwin Hubble and Georges Lemaitre made a startling discovery that forever changed our perception of the Universe. Upon observing galaxies beyond the Milky Way and measuring their spectra, they determined that the Universe was expanding. By the 1990s, with the help of the Hubble Space Telescope, scientists took the deepest images of the Universe to date and made another startling discovery: the rate of expansion is speeding up! This parameter, denoted by Lambda, is integral to the accepted model of cosmology, known as the Lambda Cold Dark Matter (LCDM) model.

Since then, attempts to measure distances have produced a discrepancy known as the “Hubble Tension.” While it was hoped that the James Webb Space Telescope (JWST) would resolve this “crisis in cosmology,” its observations have only deepened the mystery. This has led to several proposed resolutions, including the idea that there was an “Early Dark Energy” shortly after the Big Bang. In a recent paper, an international team of astrophysicists proposed a new solution based on an alternate theory of gravity that states that our galaxy is in the center of an “under-density.”