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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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Dark Dwarfs: New Star-Like Objects May Reveal Nature of Dark Matter

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July 9, 2025

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Dark Dwarfs: New Star-Like Objects May Reveal Nature of Dark Matter

Astronomers predict an unseen class of star-like bodies called “dark dwarfs” near our galaxy’s center. A new study suggests these objects could shine thanks to annihilating dark matter, not nuclear fusion. Dark matter makes up about a quarter of the universe and interacts via gravity. If WIMP-like dark matter particles collect in a brown dwarf, they would annihilate and heat it, causing a faint glow. Dark dwarfs would be too light to fuse hydrogen, but would keep lithium-7 in their atmospheres, offering a signature. This prediction comes from a JCAP study. The discovery of one could reveal dark matter’s nature.

Predicted Dark Dwarf Properties

According to the paper, sub-stellar objects just below the hydrogen-burning threshold would be powered by dark matter. The authors find that the minimum mass for hydrogen fusion shifts above ∼0.075 M⊙ in dense dark-matter environments, so lighter brown dwarfs instead become stable dark-matter–powered stars (‘dark dwarfs’) via WIMP annihilation inside them. They predict such objects only appear in regions with extremely high dark-matter density, like the Galactic center (ρ_DM ≳ 10^3 GeV/cm^3), because further out the halo is too tenuous. Crucially, dark dwarfs should retain lithium-7 in mass ranges where ordinary brown dwarfs burn it away, providing a clear observational signature.

Observational Prospects and Implications

Sakstein notes that powerful telescopes like the James Webb Space Telescope might even already detect extremely cold objects like dark dwarfs near the galactic center. Alternatively, astronomers could survey brown dwarf populations for a rare sub-class with anomalous lithium content. Notably, even one confirmed dark dwarf would strongly favor heavy, self-annihilating dark matter.

Sakstein explains that finding dark dwarfs would provide “compelling evidence” for dark matter that is massive and interacts with itself – essentially WIMPs or similar particles. He notes that lighter candidates (like axions) would not produce such stars, so a dark dwarf discovery would disfavor those models. While not a proof of WIMPs, a dark dwarf detection would imply dark matter behaves like WIMPs (heavy and weakly interacting). Indeed, future surveys and JWST observations will also test these predictions.

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NASA Astronaut Captures Rare Red Sprite Over Storm from Space Station

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July 9, 2025

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NASA Astronaut Captures Rare Red Sprite Over Storm from Space Station

In early July 2025, NASA astronaut Nichole “Vapor” Ayers snapped a rare image of a giant red “sprite” phenomenon erupting above a thunderstorm, as she orbited 250 miles (400 km) above Earth. Sprites are brief, luminous columns caused by powerful lightning discharges far below. Ayers noted that having the ISS vantage makes for a “great view above the clouds” and helps scientists analyze these elusive events. This sprite appeared over storm clouds spanning Mexico and the southern U.S. on July 3, 2025. The sighting coincides with NASA’s Spritacular citizen-science project, which crowdsources photos of sprites and other upper-atmosphere flashes.

Rare ‘Sprite’ Phenomenon Explained

According to NASA, sprites are one of the “least understood” and most visually striking upper-atmosphere phenomena. They are brief columns of red light that flash high above thunderclouds, triggered by powerful lightning strikes. Data show sprites often form around 50 miles (80 km) altitude above Earth. These fleeting bursts take varied shapes – tendrils, plumes or towering columns of red light.

In Ayers’s photo, the sprite looks like an inverted scarlet umbrella extending into the sky. Each sprite flash lasts only a few milliseconds, so every image provides valuable data. Observations from orbit and the ground are steadily building a clearer picture of these mysterious storm-driven events. For example, NASA’s Juno mission even recorded sprite-like flares in Jupiter’s atmosphere, suggesting similar lightning processes on other worlds.

Crowdsourcing Sprites

To gather more data on sprites, NASA launched the Spritacular citizen-science project. Through Spritacular, volunteers with cameras can submit photos of upper-atmosphere flashes for research. The project’s website reports over 800 volunteers from 21 countries have uploaded about 360 sprite sightings since its 2022 launch. Each contribution helps scientists map where and how sprites occur. Ayers’s ISS photo adds a valuable perspective that complements citizen reports.

Space.com notes that multiple ISS crew members have begun photographing sprites from orbit, bolstering the data. Spritacular principal investigator Dr. Burcu Kosar says the project “will bridge the gap” between casual observers and researchers. NASA scientists say many questions about how and why sprites form “remain unanswered”, so more images could soon help decode the mystery.

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Progress 92 Spacecraft Docks at ISS with Vital Supplies for Expedition 73

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July 9, 2025

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Progress 92 Spacecraft Docks at ISS with Vital Supplies for Expedition 73

The progress of 92 spacecraft, which is unpiloted, reached the space-facing port of the Poisk of the orbiting laboratory at 2:55 a.m. IST on Sunday, July 5, 2025. At 5:25 p.m. EDT, Saturday, July 5, 2025, the spacecraft landed. The spacecraft launched a 1:02 a.m. IST on July 4, 2025, on a Soyuz rocket from Kazakhstan’s Baikonur Cosmodrome. This spacecraft by Roscosmos is for providing tons of food, fuel and other supplies for the Expedition 73 crew on the International Space Station.

Six-Month Docking to Aid Research and Waste Management on ISS

As reported by NASA, it will be there on the dock for around six months before its departure and re-entry into the atmosphere of the Earth to dispose of the trash that the crew has loaded. This spacecraft includes a wide variety of essential items for astronomers. Apart from food and fuel, there are some equipment and spare parts also which are needed by the astronauts. Such items help the astronauts to perform their daily activities and conduct the planned experiments in space. It would be very difficult to maintain the life support and let the operations continue without any hampering.

Progress 92 Delivers Crucial Supplies to Support Expedition 73

Dr. Natalia Sergeyevna, the Roscosmos scientist, said in a statement that this successful docking portrays our strength in the continuous support to the ISS for the successful completion of Expedition 73. Every cargo mission is crucial and needs to ensure safety, health, and productivity. NASA praised the mission, calling the Progress Cargo deliveries a key part of keeping long-duration space missions going in a smooth manner.

Along with the everyday needs, the cargo also carried the materials for research related to health, plant growth, space materials and fluid dynamics. Scientists can better understand how living and working in space impacts their bodies and the milieu.

Progress 92 will stay docked at the ISS for about six months. After the work, the spacecraft will undock and make its re-entry into the atmosphere of the Earth and burn up safely. Cargo missions not just supply but also manage waste, keeping the ISS efficient and clean.

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