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Astronomers have assembled the largest-ever compilation of high-precision galaxy distances, called Cosmicflows-4. Galaxies, such as the Milky Way, are the building blocks of the universe, each comprised of up to several hundred billion stars. Galaxies beyond our immediate neighborhood are rushing away, faster if they are more distant, which is a consequence of the expansion of the universe that began at the moment of the Big Bang. Measurements of the distances of galaxies, coupled with information about their velocities away from us, determine the scale of the universe and the time that has elapsed since its birth.

“Since galaxies were identified as separate from the Milky Way a hundred years ago, astronomers have been trying to measure their distances,” said Brent Tully, astronomer at the University of Hawaii at Manoa. “Now by combining our more accurate and abundant tools, we are able to measure distances of galaxies, and the related expansion rate of the universe and the time since the universe was born with a precision of a few per cent.”

From the newly published measurements, the researchers derived the expansion rate of the universe, called the Hubble Constant, or H0. The team’s study gives a value of H0=75 kilometers per second per megaparsec or Mpc (1 megaparsec = 3.26 million light years), with very small statistical uncertainty of about 1.5 percent.

There are a number of ways to measure galaxy distances. Generally, individual researchers focus on an individual method. The Cosmicflows program spearheaded by Tully and Kourkchiincludes their own original material from two methods, and additionally incorporates information from many previous studies. Because Cosmicflows-4 includes distances derived from a variety of independent, distinct distance estimators, intercomparisons should mitigate against a large systematic error.

Astronomers have assembled a framework that shows the universe’s age to be a little more than 13 billion years old, however, a dilemma of great significance has arisen in the details.

Physics of the evolution of the universe based on the standard model of cosmology predicts H0=67.5 km/s/Mpc, with an uncertainty of 1 km/s/Mpc. The difference between the measured and predicted values for the Hubble Constant is 7.5 km/s/Mpc – much more than can be expected given the statistical uncertainties. Either there is a fundamental problem with our understanding of the physics of the cosmos, or there is a hidden systematic error in the measurements of galaxy distances.

Cosmicflows-4 is also being used to study how galaxies move individually, in addition to flowing with the overall expansion of the universe. Deviations from this smooth expansion arise due to the gravitational influences of clumps of matter, on scales ranging from our Earth and Sun up to congregations of galaxies on scales of a half billion light years. The mysterious dark matter is the dominant component on larger scales. With knowledge of the motions of galaxies in response to the mass around them, we can recreate the orbits that galaxies have followed since they were formed, giving us a better understanding of how the universe’s vast, dark-matter-dominated structures have formed over the eons of time.

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Hubble Uncovers Multi-Age Stars in Ancient Cluster, Reshaping Galaxy Origins

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July 19, 2025

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Hubble Uncovers Multi-Age Stars in Ancient Cluster, Reshaping Galaxy Origins

Astronomers call ancient star clusters like NGC 1786 “time capsules” for their galaxy, preserving some of its oldest stars. A new image from NASA’s Hubble Space Telescope offers an unprecedented close-up of this dense cluster 160,000 light-years away in the Large Magellanic Cloud. Hubble’s data show that NGC 1786 contains stars of different ages – a surprising find, since such clusters were once thought to hold a single stellar generation. This multi-age discovery is reshaping our view of how galaxies built their first stars, and suggests more complex early history.

Mixed-Age Stars in a Galactic Time Capsule

According to the official source, this Hubble image shows the globular cluster NGC 1786, a ball of densely packed stars in the Large Magellanic Cloud about 160,000 light-years from Earth. Astronomers captured this picture as part of a program comparing ancient clusters in nearby dwarf galaxies (like the LMC) with clusters in our own Milky Way. The surprising discovery is that NGC 1786 hosts stars of multiple ages. In fact, astronomers expected all stars in such a cluster to form at the same time, so finding multiple stellar generations was unexpected. This suggests even ancient clusters in other galaxies have more complex, layered histories than scientists expected.

Clues to Galaxy Evolution

For astronomers, the discovery provides clues to galaxy formation. Each globular cluster is like a snapshot of its galaxy’s past, so finding multiple stellar generations implies the Large Magellanic Cloud built its stars in stages rather than all at once. By comparing NGC 1786 to clusters in the Milky Way, researchers can retrace how both galaxies assembled their oldest stars. As one NASA scientist notes, this study “can tell us more not only about how the LMC was originally formed, but the Milky Way Galaxy, too”. Overall, the discovery supports a picture of gradual galactic growth through multiple waves of star formation and mergers, rather than a single early burst.

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sPHENIX at RHIC Delivers First Results, Sets Stage for Quark–Gluon Plasma Studies

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July 19, 2025

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sPHENIX at RHIC Delivers First Results, Sets Stage for Quark–Gluon Plasma Studies

Brookhaven’s sPHENIX detector at the Relativistic Heavy Ion Collider (RHIC) has reported its first physics measurements of gold-ion collisions. Designed for heavy-ion experiments, sPHENIX recorded precision counts of thousands of charged particles and their energies from head-on gold–gold impacts. These early results confirm the detector’s performance and pave the way for its main mission: exploring the quark–gluon plasma (QGP), the hot, dense state of matter thought to have filled the universe microseconds after the Big Bang. By verifying basic collision properties, the experiment lays the foundation for deeper QGP studies.

Probing the Quark–Gluon Plasma

According to two papers, the quark–gluon plasma is an exotic state of matter made of free quarks and gluons that existed microseconds after the Big Bang. Colliding heavy nuclei at RHIC (200 GeV per nucleon) creates a tiny fireball where nuclear matter “melts” into this plasma. sPHENIX was built to probe these extreme conditions. It is essentially an upgrade of Brookhaven’s earlier PHENIX detector.

sPHENIX found that head-on (central) Au+Au collisions produce about ten times more charged particles and energy than glancing (peripheral) collisions. This matches earlier RHIC results and confirms the detector is performing as designed. With this baseline established, researchers will pursue the QGP’s rarest probes – fully reconstructed jets – to study how quarks and gluons lose energy in the plasma.

Implications and Next Steps

RHIC’s final 2025 run of gold-ion collisions will exploit every detector’s capabilities. At the same time, CERN’s LHC collides lead nuclei at much higher energy, and its ALICE/ATLAS/CMS experiments have observed similar QGP effects like jet quenching. The two colliders probe complementary regimes, so sPHENIX’s precise RHIC measurements will enrich the global picture of the plasma.

Next, sPHENIX will treat energetic jets as a microscope on the QGP. By comparing energy loss in heavy-quark vs. light-quark jets, scientists can test whether the plasma is a smooth fluid or contains clumps. As one co-spokesperson notes, the first measurements “establish the basis” for sPHENIX’s QGP program and herald “the start of a very exciting chapter” of discovery.

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Chandra Spots Distant Baby Planet Losing Its Atmosphere Under Intense X-ray Assault

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July 19, 2025

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Chandra Spots Distant Baby Planet Losing Its Atmosphere Under Intense X-ray Assault

Astronomers using NASA’s Chandra X-ray Observatory have discovered a Jupiter-sized exoplanet that is being fried by the radiation from its parent star. The study determined that the star plan is getting extended so fast that it must be evaporating, losing more than 10 times the mass of Jupiter every billion years. This baby world is only 8 million years old, located some 330 light-years from Earth, and orbits perilously close to its host star, at a distance of 8.2 million miles. The powerful X-rays it is bombarded with are slowly blowing away the planet’s atmosphere, and it’s at risk of being stripped bare and turned into a rocky core in a billion years or so.

X-ray Radiation From Host Star Is Rapidly Stripping Baby Exoplanet TOI 1227 b’s Atmosphere

As per a NASA statement, the planet’s mass—roughly 17 times that of Earth—is not enough to resist the high-energy onslaught from its parent star, which, despite being cooler and less massive than our Sun, emits stronger X-rays. By analysing Chandra observations alongside computer models, Attila Varga of the Rochester Institute of Technology and colleagues concluded that the exoplanet sheds the equivalent of Earth’s atmosphere every 200 years or so. “It’s almost incomprehensible what’s happening to this planet,” Varga stated.

X-rays are vital for the study of the evolution of planets in systems far away from our own, say co-authors Joel Kastner. The radiation not only heats TOI 1227 b’s atmosphere but also inflates it, making it more vulnerable to escape. Over time, this process will cause the planet to lose more than 10% of its mass, equal to two Earths. “The future for this baby planet doesn’t look great,” mentioned Alexander Binks of Eberhard Karls University of Tübingen.

To determine the planet’s age, researchers analysed the motion of its host star relative to other populations of stars and then used models of its brightness. TOI 1227 b is a rare object among planets with an age less than 50 million years since it is hosted by a low-mass star and has a long orbital period of 28 days. But the planet is already past its expiration date.

The team’s findings, which shed light on the impact of high-energy environments on young planets, have been accepted for publication in The Astrophysical Journal and are available in preprint on arXiv.

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