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A gigantic array of radio dishes proposed for the Utah desert could advance our understanding of physics and help us decode cosmic radio signals. Now, scientists have outlined how it would work.

Beginning in the 1950s, radio astronomy has opened up a powerful view into the inner workings of the universe, revealing everything from how stars form to incredible images of our galaxy’s gigantic black hole. Now, astronomers are building a gigantic array of radio dishes, called the Deep Synoptic Array 2000 (DSA-2000). The array consists of 2,000 radio dishes, each 16 feet (5 meters) across, laid out in a radio-quiet part of the Utah desert.

While the shortest day of the year typically falls in winter, summer will have its fair share of abnormally short days this year. According to TimeandDate, Earth will spin unusually fast in July and August, resulting in shorter days.

From the point of view of the sun, it takes Earth roughly 86,400 seconds (24 hours) to complete one full rotation. This changes slightly from day to day, and these small variations are measured with atomic clocks. The number of milliseconds above or below 86,400 seconds is referred to as length of day.

Until 2020, the shortest length of day ever recorded was -1.05 milliseconds, meaning it took the Earth 1.05 milliseconds less than 86,400 seconds to complete one rotation. Since then, Earth has beaten this record every year, with the shortest day of all being -1.66 milliseconds.

This month,TimeandDate reports that Earth will get close to its previous record. On July 9, the length of date is expected to be -1.30 milliseconds, followed by -1.38 milliseconds on July 22 and -1.51 milliseconds on August 5.

“Nobody expected this,” Leonid Zotov, a leading authority on Earth rotation at Moscow State University, told the outlet. “The cause of this acceleration is not explained.” Zotov added that most scientists believe it is something inside the Earth. “Ocean and atmospheric models don’t explain this huge acceleration,” he said.

Despite this acceleration, Zotov predicts that Earth will slow down soon. “I think we have reached the minimum,” he told TimeandDate. “Sooner or later, Earth will decelerate.” In the meantime, scientists will continue to study the reason behind Earth’s length of day variations.

Of course nothing and no one can actually see dark matter, but the accurate mapping of its warping influence on this new image from the James Webb Space Telescope is as good as it gets.

Containing two very large galaxy clusters, together known as the Bullet Cluster, the blue hues in the image represent where the light from galaxies in the background is passing through areas of dark matter which are altering it.

“Webb’s images dramatically improve what we can measure in this scene — including pinpointing the position of invisible particles known as dark matter,” said Kyle Finner, a co-author on a paper analyzing the data behind the images, and an assistant scientist at IPAC at Caltech in Pasadena.

All galaxies are made up of stars, gas, dust, and dark matter, which are bound together by gravity. These galaxy clusters act as gravitational lenses, magnifying and or distorting the light of background galaxies, and allowing scientists to infer the distribution of dark matter therein.

Currently an unsolved and hypothetical entity, dark matter is believed to constitute 85% of the matter in the universe. Because it doesn’t interreact with light or electromagnetism, dark matter exists to us only through its influence on visible matter. The influence takes the form of gravitational effects that cannot be explained by the theory of General Relativity.

After decades of studying the effects of dark matter, the general belief is that it builds structures as the universe expands, while at the same time another mysterious force, dark energy, is believed to be pushing those structures away from one another.

One of the best ways to study dark matter is to identify instances of gravitational lensing. James Jee, a co-author on the same paper, professor at Yonsei University, and research associate at UC Davis in California, explained to NASA that it’s like looking at stones below a pond of clear, still water.

“You cannot see the water unless there is wind, which causes ripples,” Jee explained. “Those ripples distort the shapes of the pebbles below, causing the water to act like a lens.”

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In this example, the dark matter is the water and the background galaxies are the pebbles.

Jee, Finner, and their colleagues measured thousands of galaxies in Webb’s images to accurately “weigh” both the visible and invisible mass in these galaxy clusters. They also carefully mapped and measured the collective light emitted by stars that are no longer bound to individual galaxies—known as intracluster stars.

MORE OF JAMES WEBB’S RECENT WORK: James Webb Telescope Debuts New Trick: Blocking Out Stars and Photographing Their Planets

The revised map of the Bullet Cluster is shown in two layers. On top of an image from Webb’s NIRCam (Near-Infrared Camera) is data from NASA’s Chandra X-ray Observatory that shows hot gas in pink, including the bullet shape at right. Refined measurements of the dark matter, calculated by the team using Webb’s observations, are represented in blue.

“We confirmed that the intracluster light can be a reliable tracer of dark matter, even in a highly dynamic environment like the Bullet Cluster,” said the paper’s lead author, Sangjun Cha.

SHARE This Excellent Primer On Dark Matter And Its Effects From James Webb…

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NASA’s James Webb Space Telescope (JWST) has produced a new image of the Bullet Cluster, which is a titanic collision between two individual galaxy clusters.

The image, produced in conjunction with NASA’s Chandra X-ray Observatory, reveals not only the location and mass of dark matter present, but also points the way toward one day figuring out what dark matter is actually made of.

In the new image, we see the hot gas within the Bullet Cluster in false-color pink, detected by Chandra. The inferred location of dark matter is represented in blue (also false color), as measured by the JWST. Note that the blue and the pink are separate — what has caused the dark matter and the gas to separate, and how were astronomers able to produce this map of the material within the Bullet Cluster?

Located 3.9 billion light-years away, the Bullet Cluster has been an occasionally controversial poster child for dark-matter studies. Back in 2006, the Hubble Space Telescope and the Chandra X-ray Observatory worked together to image the Bullet, showing the presence of its dark matter based on how light from more distant galaxies was being gravitationally lensed by the dark matter’s mass.

Collisions between galaxy clusters are the perfect laboratories for testing our ideas about dark matter, because they are nature’s way of throwing together huge amounts of the stuff. This gives us a chance to test how dark matter particles interact with each other, if at all, and the degree of any interaction would be a huge clue as to the properties of the mysterious dark matter particle.

Yet despite the dramatic Hubble and Chandra images, the Bullet Cluster — and, indeed, other galaxy cluster collisions — haven’t always played ball. For instance, the velocities at which the sub-clusters are colliding seem too high for the standard model of cosmology to explain.

Now the JWST has entered into the fray. A team led by Ph.D. student Sangjun Cha of Yonsei University in Seoul, South Korea, and professor of astronomy James Jee at both Yonsei and the University of California, Davis, have used the most powerful space telescope ever built to get a best-ever look at the Bullet Cluster.

Hubble and Chandra had previously shown that, as the two individual galaxy clusters in the Bullet Cluster collided, the galaxies and their surrounding dark matter haloes had passed right through each other. This makes sense for the galaxies — the distances between them are so great that the chance of a head-on collision between any two is slim. It also suggests that the degree with which dark matter particles interact with each other — what we refer to as their collisional cross section — is small; otherwise, the interaction would have slowed the clouds of dark matter down, and we would detect it closer to where Chandra sees the hot, X-ray emitting intracluster gas. In contrast to the dark matter, these huge gas clouds can’t get out of each other’s way, so they slam into each other and don’t progress any further.

The end result is that the hot gas is found stuck in the middle of the collision, and the galaxies and dark matter belonging to each sub-cluster are found on opposite sides, having glided right through one another.

“Our JWST measurements support this,” Jee told Space.com. “The galaxy distribution closely traces the dark matter.”

JWST was able to produce a better map of the distribution of matter, both ordinary and dark, in the Bullet Cluster by detecting, for the first time, the combined glow from billions of stars that have been thrown out of their galaxies and are now free-floating in the space between the galaxies in each sub-cluster. Cha and Jee’s team were then able to use the light from these “intracluster stars” to trace the presence of dark matter and gain a more accurate map of its distribution in the Bullet Cluster.

However, this has just raised more mysteries. The more refined map of the dark matter shows that, in the larger sub-cluster, on the left, the dark matter is arranged in an elongated, “hammerhead” shape that, according to Jee, “cannot be easily explained by a single head-on collision.”

This elongated mass of dark matter is resolved into smaller clumps centered on what we call the brightest cluster galaxies — giant elliptical galaxies that are the brightest galaxies in the sub-cluster located at its gravitational core. In contrast, the dark matter halo around the sub-cluster on the opposite side is smaller and more compact.

Cha and Jee’s team suspect that the elongated, clumpy mass of dark matter could only have formed when that particular sub-cluster, which was a galaxy cluster in its own right before the Bullet collision, underwent a similar collision and merger with another galaxy cluster billions of years before the formation of the Bullet.

“Such an event would have stretched and distorted the dark-matter halo over time, resulting in the elongated morphology that we observe,” said Jee.

Despite the new discoveries such as this from JWST’s more refined observations of the Bullet cluster, it is still not enough to resolve the issue of the collision velocities of the two sub-clusters.

“Even with these updates, the required collision velocity remains high relative to expectations from cosmological simulations,” said Jee. “The tension persists and remains an active area of research.”

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Dark matter makes up over a quarter of all the mass and energy in the universe, and roughly 85% of all matter, so figuring out its secrets, in particular its collisional cross-section and the cause of those high velocities, is going to be essential if we want to better understand this universe in which we live.

Alas, the JWST observations of the Bullet Cluster alone are not enough to confirm what the collisional cross-section of dark matter must be. However, they do tighten the estimate of the upper limit for the value of the cross-section, constraining the list of possibilities.

Astronomers are already in the process of rigorously measuring as many galaxy cluster collisions as possible, seen from all angles and distances, to try and constrain this value further. Gradually, we’ll be able to rule out different models for what dark matter could be, until we’re left with just a few. Coupled with experimental data from direct dark matter searches from detectors deep underground, such as the LUX-ZEPLIN experiment at the Sanford Underground Research Facility in South Dakota, we could soon be on the cusp of answering one of science’s greatest mysteries: what is dark matter?

The JWST observations were reported on June 30 in The Astrophysical Journal Letters.

NASA’s SPHEREx space telescope has settled into low-Earth orbit, where it is transmitting data back home and providing a public wellspring of space data for both professional and citizen scientists.

First launched in March of this year, SPHEREx (the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer) is currently creating all-sky maps of the universe as its primary mission, with secondary goals to support other space observation platforms. While not the first all-sky mission, SPHEREx improves upon previous attempts by boasting 102 infrared wavelength observations, compared to the earlier WISE mission’s four wavelengths.

NASA’s SPHEREx Mission

As astronomers study increasingly distant parts of the universe, spectroscopy has become a crucial tool for understanding the cosmos. This allows researchers to analyze infrared wavelength data from distant celestial bodies and identify the molecules present within them. SPHEREx scientists will utilize this technique to search for essential elements for life, such as water ice and organic molecules, throughout the Milky Way galaxy.

The telescope’s 102 wavelengths will provide precise data for the ongoing search, and the SPHEREx mission will also study universal expansion by measuring the distant light emissions from all galaxies over time.

“Because we’re looking at everything in the whole sky, almost every area of astronomy can be addressed by SPHEREx data,” said Rachel Akeson, the lead for the SPHEREx Science Data Center at IPAC. IPAC is a science and data center for astrophysics and planetary science at Caltech in Pasadena, California.

SPHEREx’s mission is currently scheduled to run for two years, during which it will complete two all-sky surveys annually, resulting in a total of four maps. Halfway through the mission, the SPHEREx team is planning to release a 102-wavelength sky map at the one-year mark.

Transparency and Access to Space Data

SPHEREx is part of NASA’s overall commitment to transparency and data sharing. The data is hosted by the IPAC Infrared Science Archive (IRSA), which also contains data from other NASA infrared and submillimeter missions, such as WISE and 2MASS. By providing public access to their data, the SPHEREx team hopes others will utilize the resource to produce many more studies than what their team can accomplish alone.

“We want enough information in those files that people can do their own research,” Akeson said.

SPHEREx’s observations are available to the public within 60 days of when the readings occurred. During that roughly two-month period, the team performs processing on the data to remove or note questionable data due to artifacts, align images with their astronomical coordinates, and account for potential defects in instrumentation.

The team is also committed to being transparent about how the data is processed, publishing the procedures used in tandem with the data releases. 

“SPHEREx is part of the entire legacy of NASA space surveys,” said IRSA Science Lead Vandana Desai. “People are going to use the data in all kinds of ways that we can’t imagine.”

Supporting Other Discovery Missions

The SPHEREx data will also provide an important supplement to other space telescope missions. Its broad scope will enable astronomers to identify interesting targets for closer observation by the James Webb Space Telescope and refine exoplanet parameters from NASA’s TESS observations.

Additionally, SPHEREx can be directed towards searching for dark matter and energy, working in tandem with the European Space Agency’s Euclid mission and NASA’s forthcoming Nancy Grace Roman Space Telescope, with a targeted May 2027 launch. 

“By making the data public, we enable the whole astronomy community to use SPHEREx data to work on all these other areas of science,” Akeson said.

Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.

This photo taken on July 4, 2025 shows the rising sun in Jiamusi City, northeast China’s Heilongjiang Province. The Earth passed the aphelion on July 4, which is the time of year when the Earth is farthest from the sun, and the apparent diameter of the sun is the smallest in the year. (Photo by Zhu Zongqiang/Xinhua)

This photo taken on July 4, 2025 shows the rising sun in Qingzhou City, east China’s Shandong Province. The Earth passed the aphelion on July 4, which is the time of year when the Earth is farthest from the sun, and the apparent diameter of the sun is the smallest in the year. (Photo by Wang Jilin/Xinhua)

This photo taken on July 4, 2025 shows the rising sun in Jiamusi City, northeast China’s Heilongjiang Province. The Earth passed the aphelion on July 4, which is the time of year when the Earth is farthest from the sun, and the apparent diameter of the sun is the smallest in the year. (Photo by Qu Yubao/Xinhua)

A tourist takes photos with the rising sun at Dongji Pavilion in Fuyuan City, northeast China’s Heilongjiang Province, July 4, 2025. The Earth passed the aphelion on July 4, which is the time of year when the Earth is farthest from the sun, and the apparent diameter of the sun is the smallest in the year. (Xinhua/Zhang Tao)

This photo taken on July 4, 2025 shows the rising sun in Yichun City, northeast China’s Heilongjiang Province. The Earth passed the aphelion on July 4, which is the time of year when the Earth is farthest from the sun, and the apparent diameter of the sun is the smallest in the year. (Photo by Li Shaojun/Xinhua)

Tourists take photos of the rising sun at Dongji Pavilion in Fuyuan City, northeast China’s Heilongjiang Province, July 4, 2025. The Earth passed the aphelion on July 4, which is the time of year when the Earth is farthest from the sun, and the apparent diameter of the sun is the smallest in the year. (Xinhua/Zhang Tao)

An aerial drone photo taken on July 4, 2025 shows the rising sun at the Sanjiangkou ecological tourism area in Tongjiang City, northeast China’s Heilongjiang Province. The Earth passed the aphelion on July 4, which is the time of year when the Earth is farthest from the sun, and the apparent diameter of the sun is the smallest in the year. (Photo by Liu Wanping/Xinhua)