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Mysterious 'little red dots' at the beginning time may finally have an explanation, thanks to newfound 'little blue companions'

After using the James Webb Space Telescope (JWST) to peer back toward the beginning of time, astronomers have proposed a radical new explanation for one of the universe's most flummoxing phenomena.

Little red dots (LRDs) are mysteriously compact, brilliant celestial objects found predominantly when the universe was less than 10% of its current age.

As revealed by JWST's unmatched infrared sensitivity, LRDs emerged incredibly early, only around 600 million years after the Big Bang, and then began disappearing about a billion years later.

Now, in a paper published in The Astrophysical Journal Letters, astronomers have proposed a novel formation mechanism for LRDs: They may be birthed by previously undiscovered celestial companions, whose intense ultraviolet (UV) radiation causes gas clouds to collapse into incredibly dense and exotic objects, like "black hole stars."

An illustration of a glowing ball of gas showing its core layers.

An illustration of a black hole star, or quasi-star, powered by a black hole surrounded by a cocoon of gas. (Image credit: (MPIA/HdA/T. Müller/A. de Graaff) via Wikimedia Commons)

"The most surprising aspect… is that these little red dots are not just 'red dots,' but there is a more complex emission nearby and around them," Josephine Baggen, an astronomer at Yale University and first author of the study, told Live Science in an email. "We think those what we call 'companions' are starlight."

Connecting the dots

In the study, the researchers compiled a sample of 83 LRDs, imaged with JWST, from ultradeep surveys. They found that 36 of the 83 LRDs, including over 80% of the brightest ones, hosted at least one companion that shined bright in blue-ish ultraviolet light; little red dots with little blue companions.

A series of small boxes showing red dots in deep space.

The LRDs sampled in this study. (Image credit: (Baggen et al., ApJL, 2026) )

These companions had masses ranging from hundreds of millions to billions that of the sun, suggesting that they may be star clusters or relatively small early galaxies, Baggen told Live Science.

These UV-spewing companions spurred the formation of LRDs from immense gas clouds, the team's new proposal states. Normally, cold molecular gas clouds fragment and condense into stars. But the intense UV irradiation from the companions halted the fragmentation process, potentially squeezing the gas clouds into supermassive stars that directly collapsed into black holes while skipping the explosive supernova stage that normally marks these stars' deaths.

This proposal helps to explain why LRDs appear bright in red optical light and UV wavelengths, with a dip between the two caused by the wavelengths of light absorbed by hydrogen gas. Rather than originating from a single object, the optical red light derives from the LRD, the UV light comes from its nearby companion, and the dip is thought to be caused by the dense cocoon of gas around the LRD.

As a result, the researchers suggested that all LRDs may have such partners but they may be too close together to be distinguished. Conversely, some companions may be separated by greater distances than the researchers accounted for in this study, requiring future observations to zoom out.

Galactic potential?

Intriguingly, this work may illuminate a couple of early-universe enigmas. First, the black holes manifesting from these interactions may be between 100,000 and 1 million solar masses, forming the "seeds" necessary to explain how ancient supermassive black holes grew so surprisingly massive so early in cosmic history.

Additionally, because LRDs may merge with the relatively small, UV-spewing galaxies that birthed them, this process may have created the impressively immense galaxies all around us today.

"We do think that this might be the birth of the supermassive black holes around these UV companions, born 'outside the galaxy,' [which] will eventually merge," Baggen told Live Science. "Whether this is what happened to the Milky Way in its earliest phases, we cannot really say, but it is plausible! There is still a lot of debate about how LRDs evolve and what they turn into at later times."

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Science word of the day: Heliosphere

Science word of the day: Heliosphere

Pronunciation: HEE'-lee-uhs-feer

What it means: The heliosphere is the region around the sun that's affected by the solar wind, a flow of charged particles emanating from the sun. Think of the heliosphere like a giant bubble encompassing the sun and planets, reaching out into space at three times the distance of Pluto. This bubble protects the solar system from radiation emanating from outer space, but the solar wind can also erode planetary atmospheres. Luckily, Earth is protected by its own bubble, the magnetosphere, which helps deflect the solar wind.

How to use it in a sentence: Because the entire solar system is traveling through space, scientists have long pictured the heliosphere as comet-shaped, but recent research suggests the bubble of solar wind looks more like a sad, deflated croissant.

Can you crack our science word of the day puzzle, Chain Word?

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'It's absolutely exciting!': Astronomers discover an atmosphere around an Earth-like planet in the habitable zone for first time ever

Astronomers have found the strongest evidence yet that a rocky planet beyond our solar system has managed to hold onto an atmosphere — a crucial ingredient for life as we know it.

The discovery marks the first time scientists have detected an atmosphere surrounding a rocky planet orbiting in the habitable zone of another star, the region around a star where temperatures could enable liquid water to exist on a planet's surface. The findings, published July 16 in the journal Science, could help astronomers narrow the search for potentially habitable worlds beyond our cosmic backyard.

"It's absolutely exciting," Edward Schwieterman, associate professor of astrobiology at the University of California, Riverside, who was not involved in the study, told Live Science in an email. "We are getting closer to studying the atmospheres of worlds that could plausibly harbor life, with evidence of that life embedded in their observable spectra."

The planet, known as LHS 1140 b, lies about 48 light-years away from Earth and orbits a small, cool red dwarf star. At roughly 5.6 times Earth's mass, the exoplanet is classified as a super-Earth: a rocky planet larger than our own but much smaller than gas giants like Neptune.

It receives less than half the sunlight Earth gets, giving it an estimated surface temperature of around minus 53 degrees Fahrenheit (minus 47 degrees Celsius), according to previous estimates not accounting for an atmosphere. That makes the planet cold, but in the range astronomers consider potentially habitable.

Cosmic gas leak

Scientists have discovered thousands of exoplanets over the past few decades, including many rocky worlds. But determining whether those planets have atmospheres has proven far more difficult, because atmospheres around rocky planets are incredibly thin compared with those of giant planets, making them much harder to detect across vast cosmic distances.

Instead of looking for the atmosphere directly, the researchers behind the new study searched for a subtle clue that one existed: helium gas leaking into space. Using the WINERED spectrograph on the Magellan Clay Telescope in Chile, the team watched LHS 1140 b cross in front of its star and let a sliver of starlight filter through the planet's atmosphere on its way to Earth. As it did, the team looked for a tiny dip in the star’s light at the exact wavelength of infrared light that helium blocks — a telltale sign that gas was streaming off the planet and into space.

The prediction rested entirely on a mathematical model that had never been confirmed for a rocky planet. However, in September 2024, the team caught LHS 1140 b and a smaller, hotter neighboring planet, LHS 1140 c, transiting their star on the same night, less than 40 minutes apart. The researchers detected a clear helium signal from LHS 1140 b, while LHS 1140 c showed nothing.

An illustration of a planet in deep space with a glowing sun behind it.

NASA concept art depicting LHS 1140 b as a rocky super-Earth — a type of potentially habitable planet most similar to our own. (Image credit: NASA)

The contrast matters: LHS 1140 c orbits much closer to its star than LHS 1140 b does and receives roughly five times the radiation, yet it's also smaller and less gravitationally bound — conditions that should make any escaping gas easier, not harder, to spot. Finding nothing there suggests LHS 1140 c's atmosphere was stripped away long ago, while LHS 1140 b, sitting farther out in cooler, calmer conditions, has managed to hold onto its own.

The discovery addresses a question astronomers have been working to answer for decades.

"Twenty years ago we wondered whether other terrestrial-type planets even existed," study co-author Robin Wordsworth, a professor of Earth and planetary sciences at Harvard, said in a statement. "Then we learned they're common, and found some in the habitable zone. The next question was whether any of them had managed to keep an atmosphere. Now we know at least one has."

A step forward in the hunt for life

The find is especially notable because red dwarf stars like LHS 1140 can bombard nearby planets with high-energy radiation capable of stripping atmospheres away over time. Based on the star's estimated age of at least 3.1 billion years, the researchers say LHS 1140 b's atmosphere has likely persisted despite that bombardment, suggesting some rocky planets around these common stars can hang onto their atmospheres for far longer than once assumed.

But the researchers caution that detecting helium does not mean the planet is inhabited — or even that it is habitable. The observations reveal only the planet's thin upper atmosphere, not its full composition. Scientists still don't know whether LHS 1140 b has oxygen, carbon dioxide, water vapor or other gases that could make its surface more Earth-like and hospitable to life.

Instead, the discovery opens a new way to study distant rocky worlds.

"The study demonstrates that, at least in some cases, we will be able to begin characterizing the atmospheres of potentially habitable planets," Schwieterman said. "If only rocky planets orbiting Sun-like stars retained atmospheres, we might have to wait one to two decades for the launch of the Habitable Worlds Observatory to search for biosignatures on rocky planets. I'm certainly excited about what comes next!"

Future observations will aim to determine what the rest of LHS 1140 b's atmosphere is made of and investigate whether it may harbor oceans or other features associated with habitability.

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James Webb telescope uses trippy Einstein prediction to probe the farthest reaches of the universe — Space photo of the week

Quick facts

What it is: The collision-prone galaxy cluster MACS J0553.4-3342

Where it is: In the constellation Columba

When it was shared: July 2026

Around 100 years ago, Albert Einstein made an audacious prediction about space. The frequently right (but occasionally wrong) physicist theorized that, just as the curved lens of a magnifying glass bends light to increase an object's apparent size, massive celestial objects can curve the very fabric of the universe with their gravity — causing distant sources of light to bend, warp, and appear magnified as their rays pass through the region on their way to Earth.

Today, this phenomenon — called gravitational lensing — has been confirmed through dozens of telescope observations, and is a crucial tool that observatories like the James Webb Space Telescope (JWST) use to probe the light of the oldest, faintest galaxies in the universe. And in this newly released JWST image of a tumultuous young galaxy cluster, Einstein’s gravitational funhouse effect is on full display.

In the foreground, two bright white points of light ringed with white halos signify the gravitational center of MACS J0553.4-3342, a gargantuan collection of bound galaxies located in the constellation Columba (the dove). These two white beacons are massive elliptical galaxies, each wreathed in their own sub-cluster of smaller galaxies, according to a statement from the European Space Agency (ESA). And the two clusters are not getting along.

Studying the galaxies’ light as it appeared roughly 4.4 billion years ago, astronomers can tell the clusters are in the messy process of merging together. The two principal elliptical galaxies have already slammed through each other once, and now sit at a distance of around 1 million light-years apart (that’s about 10 Milky Ways lined up in a row). Eventually, that gap will close as the massive galaxies swoop back toward each other, finally combining into one.

A full-size image of JWST's observations

A full-size view of JWST's observations (Image credit: ESA/Webb, NASA & CSA, S. Fujimoto)

But the real jewels in this galactic trove are hidden in the contorted, orange arcs of light that bookend the cluster on either side. Here, the magnifying effect of gravitational lensing is acting in full force — allowing JWST to detect the light of several faint galaxies from less than a billion years after the Big Bang.

Three bright dots in the arc on the left are actually three repeated images of a single galaxy, according to ESA. The trippy effect appears several times throughout the image, with each elongated orange streak cracking open a warped window onto an ancient corner of the universe that would otherwise be impossible to see.

Through observations like these, scientists using JWST have discovered that the oldest stars and galaxies in the universe have grown larger and faster than our leading theories of cosmology predict should be possible. Using one cosmic oddity to uncover another, this gravitational lens could keep astronomers busy for decades to come.

See more space photos of the week:

A view of Earth from the moon, with half the Earth illuminated and the gray surface of the moon in the foreground.'Human minds should not go through this'

The Artemis II crew recalls the unreal moment when Earth disappeared

An image of a spiral galaxy on a splotchy black and white background with a stream of black material emerging from the galaxyHidden structure in 1st Vera Rubin image

First-light images from the Vera C. Rubin Observatory reveal a 163,000-light-year stream of stars emanating from a nearby galaxy.

Hundreds of gold and orange clouds with feathered trails going down behind them. The small clouds are covering a few scattered, bright stars.JWST peeps the 'Eye of God'

A spectacular James Webb telescope image reveals intricate structures inside the Helix Nebula.

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'Fireball' meteorite that smashed into New Jersey home contains ingredients of life from an ancient proto-planet, study finds

Scientists have discovered the building blocks of life inside a meteorite that smashed through a New Jersey home two years ago. The space rock contains amino acids, carbon compounds and other "prebiotic" molecules similar to what may have helped kick-start life on our planet, a new study shows.

Scientists on the study team — led by Peter Jenniskens, a meteor astronomer with affiliations at the SETI Institute and NASA's Ames Research Center — praised the homeowner in Hillsborough, N.J., for quickly preserving the meteorite after it fell through the roof on July 16, 2024, despite the adverse circumstances. His actions included using disposable gloves and aluminum foil to place pieces of the meteorite fragments into glass jars.

"I was at home at the time, heard a loud crash and found a hole in the ceiling of the master bedroom," the homeowner, who was not named, said in a statement from the SETI Institute. "I smelled a strong, sulfur-like odor and saw many black fragments, along with debris and black dust that covered my bed, carpet and surrounding areas."

A close up of a gray rock with jagged edges.

A close-up of the Hillsborough meteorite’s surface. (Image credit: SETI Institute)

Those meteorite pieces were precious, the scientists said, and likely came from an ancient solar system planet that wasn't fully formed. "A forensic study of the fragments revealed that they contained preserved bits from near the surface of a small primitive asteroid where it experienced concentrated salty fluids — a process not previously known from this type of protoplanet world," Jenniskens said in the statement.

The study, published July 15 in the journal Science Advances, also traced how the meteorite got to the house. Earlier on July 16, 2024, at least 60 observers in New York, New Jersey and other Northeastern states spotted a meteor later confirmed to be traveling at 32,000 mph (51,500 km/h). At least 16 people in New York and New Jersey reported feeling the meteor's shock wave.

The rock broke apart in midair, with observer reports stopping when the meteor reached 22 miles (35 kilometers) in altitude, although Newark Liberty International Airport briefly tracked pebbles falling from the sky with Doppler weather radar after that. Fragments from only one meteorite ‪—‬ called Hillsborough, after the town where it crashed through the New Jersey home ‪—‬ were recovered.

The American Meteor Society used its cameras in Northford, Connecticut, and Douglassville, Pennsylvania — along with a doorbell camera in Wayne, New Jersey — to figure out the meteor's origin, Mike Hankey, an operations manager at the American Meteor Society and co-author of the study, said in the statement. "The path traced back to low in the asteroid belt."

Hillsborough is the second stony meteorite of its type ever spotted in a fall. Later analysis showed that the meteorite is full of ancient brines or salt. Scientists classified the meteorite as a type of stony space rock called a carbonaceous chondrite.

Scientists will compare the salt minerals to samples of asteroids Ryugu and Bennu, both of which contain ingredients of life and are samples of another carbonaceous chondrite type that formed earlier than Hillsborough. This analysis could help scientists further trace the origins of life-friendly chemistry in the early solar system.

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'Shared cosmic experience': 'Potentially hazardous' asteroid Apophis could be visible to 90% of Earth's population during ultraclose 2029 flyby, new maps reveal

Up to 90% of Earth's population may be able to see the enormous "God of Chaos" asteroid Apophis zoom past our planet in less than three years, scientists say. The skyscraper-size space rock will come closer to us than some satellites, making it clearly visible to the naked eye during the "once-in-a-millennium" skywatching event.

This will be the first time humans have ever been able to predict a flyby of an asteroid visible to the naked eye, and it could be a once-in-a-lifetime experience for the up to 7.6 billion people who manage to see it, scientists said at the Apophis T-3 Years workshop, held June 18-19 at the University of Padua in Italy.

"Sighting Apophis as it passes by is a way of feeling a shared cosmic experience, realizing the smallness of Earth in the vastness of space," Richard Binzel, a planetary scientist and asteroid expert at MIT who helped organize the recent workshop and create new maps of the flyby, told Live Science in an email.

The asteroid, dubbed 99942 Apophis (or simply Apophis), is a peanut-shaped object that spans about 1,500 feet (450 meters) across at its widest point, or around as wide as the Empire State Building is tall, making it large enough to wipe out a city if it ever impacted our planet. Apophis likely originated from the solar system's main asteroid belt between Mars and Jupiter, but it now resides between the orbits of Venus and Earth, circling our home star roughly every 10.5 months. The name Apophis comes from Apep, the Egyptian serpent god of darkness and disorder, which has earned the space rock the nickname "God of Chaos."

On April 13, 2029, Apophis will make a superclose flyby of Earth, reaching a minimum distance of around 19,000 miles (30,600 kilometers) from our planet, according to The Planetary Society. That's much farther away than the International Space Station and the thousands of other spacecraft in low Earth orbit, but it's closer than several hundred satellites stationed in an elevated geosynchronous orbit. (Apophis poses no threat to these high-altitude satellites because they can easily be maneuvered away from its projected path.)

A map of Earth showing which regions are in darkness and within viewing range of Apophis at its most visible point

At the recent Apophis T-3 Years workshop, scientists shared new maps showing how many people will be within viewing range of the asteroid at each point of its seven-hour flyby of Earth. (Image credit: eclipseatlas.com)

There is currently zero chance that Apophis will impact our planet during the flyby or within the next 100 years. However, some experts have suggested that there is still a slim chance that the asteroid's trajectory could change before it reaches us. Other experts worry that the upcoming flyby could permanently alter the space rock or nudge it off course, potentially increasing the chances it could hit us in the future.

Therefore, scientists are keen to monitor the flyby in great detail and will coordinate observations from telescopes around the world to understand the potentially hazardous asteroid better. Several spacecraft, including NASA's OSIRIS-APEX, will also attempt to fly past Apophis to study its structure and trajectory. The event is so significant that the United Nations has declared 2029 the International Year of Asteroid Awareness and Planetary Defence.

Researchers also hope the flyby will provide a unique opportunity to inspire the next generation of space scientists. "I hope people will find the Apophis flyby intriguing, as it is not anything fearful or frightening at all," Binzel said. "Who knows how many young people might find a spark of curiosity that leads them on a path to a career in space studies."

Who will see Apophis?

The new maps help break down who might be able to see Apophis throughout the roughly seven-hour period it passes by our planet. The asteroid will be visible only to people who are positioned within its path at twilight or night amid clear skies and limited light pollution.

A graphic of the night sky showing the path of Apophis relative to constellations

Apophis will slowly move across the night sky through a set of well-known constellations, although its exact position will depend on where in the world you are. (Image credit: eclipseatlas.com)

At the start of the flyby, when Apophis is farthest from Earth, the asteroid could be visible to around 4.5 billion people across Australia and most of Asia. By the end of the flyby, when the space rock reaches its closest point to us, it might be visible to around 1.9 billion people in eastern South America, northern Africa and parts of Europe, according to the new maps.

Peak visibility will occur around halfway through the flyby, when Apophis might be seen by as many as 5.7 billion people across eastern Africa, Southern Europe, Australia, and all of Asia and the Middle East. At this point, astronomical observatories situated on Spain's Canary Islands will likely snap the best photos of the asteroid's flyby, according to Live Science's sister site Space.com.

North America is the only continent that will not get a clear view of Apophis.

For those who are lucky enough to see the passing space rock, the asteroid will appear as a "modest star passing slowly across the sky, much like a slow-moving satellite," Binzel said, and it will shine as brightly as the stars in the Big Dipper.

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NASA Sets Briefings for SpaceX Crew-13 Mission to Space Station

The SpaceX Crew-13 members are pictured in their pressure suits seated inside a mockup Dragon spacecraft during a preflight training session at the company's headquarters in Hawthorne, California. From left are, Roscosmos Sergey Teteryatnikov, NASA astronauts Luke Delaney and Jessica Watkins, and CSA (Canadian Space Agency) astronaut Joshua Kutryk.
NASA’s SpaceX Crew-13 members are pictured in their pressure suits seated inside a mockup Dragon spacecraft during a preflight training session at the company’s headquarters in Hawthorne, California. From left are Roscosmos Sergey Teteryatnikov, NASA astronauts Luke Delaney and Jessica Watkins, and CSA (Canadian Space Agency) astronaut Joshua Kutryk.
Credit: SpaceX

NASA and its partners will discuss the upcoming crew rotation mission to the International Space Station during a pair of news conferences on Monday, Aug. 3, from the agency’s Johnson Space Center in Houston.

Mission leadership will provide an overview of NASA’s SpaceX Crew‑13 mission at 12 p.m. EDT. Next, crew members will discuss their training and mission preparations at 2 p.m. This is Crew-13’s final media availability prior to traveling to the agency’s Kennedy Space Center in Florida for launch.

NASA will stream these events live. Learn where to watch online:

https://www.nasa.gov/live

The Crew-13 mission will carry NASA astronauts Jessica Watkins and Luke Delaney, CSA (Canadian Space Agency) astronaut Joshua Kutryk, and Roscosmos cosmonaut Sergey Teteryatnikov to the orbiting laboratory. The crew will launch aboard a SpaceX Dragon spacecraft on the company’s Falcon 9 rocket from Space Launch Complex 40 at Cape Canaveral Space Force Station in Florida no earlier than mid-September.

International media attending in person must email the NASA Johnson newsroom at jsccommu@mail.nasa.gov by 5 p.m., Tuesday, July 21. United States-based media attending in person must respond by 5 p.m., Thursday, July 30. Media joining virtually must respond by 10 a.m. the day of the event. NASA’s media accreditation policy is available online.

Briefing participants are as follows (all times Eastern and subject to change based on real-time operations):

12 p.m.: Mission Overview News Conference

  • Joel Montalbano, deputy associate administrator, Human Spaceflight Mission Directorate, NASA Headquarters
  • Dana Weigel, manager, Low Earth Orbit Program, NASA Johnson
  • Mathieu Caron, director, Astronauts, Life Sciences, and Space Medicine, CSA
  • Julianna Scheiman, director, NASA Science and Dragon Programs, SpaceX

2 p.m.: Crew-13 News Conference

  • Jessica Watkins, commander, NASA
  • Luke Delaney, pilot, NASA
  • Joshua Kutryk, mission specialist, CSA
  • Sergey Teteryatnikov, mission specialist, Roscosmos

Following the news conference, crew members will be available for limited media interviews. All interview requests must be submitted by 5 p.m. on July 30, to the NASA Johnson newsroom at: jsccommu@mail.nasa.gov.

This will be the second flight to the space station for Watkins, who was selected as a NASA astronaut in 2017. Watkins grew up in Lafayette, Colorado, and earned an undergraduate degree in geological and environmental sciences from Stanford University, as well as a doctorate in geology from the University of California, Los Angeles. As a geologist, she studied the Martian surface and was a member of the Curiosity rover science team at NASA’s Jet Propulsion Laboratory in Southern California. Watkins first launched to the space station as a crew member aboard NASA’s SpaceX Crew-4 mission, spending a total of 170 days in space across space station Expeditions 67/68 in 2022. She will be the first NASA astronaut to launch aboard a SpaceX Dragon spacecraft twice.

Selected as a NASA astronaut in 2021, Delaney earned a bachelor’s degree in mechanical engineering at the University of North Florida and a master’s degree in aerospace engineering at the Naval Postgraduate School. The Florida native is a distinguished naval aviator who participated in exercises throughout the Asia Pacific region and conducted missions in support of Operation Enduring Freedom. As a test pilot, Delaney evaluated developmental aircraft systems and served as a test pilot instructor. He also worked as a research pilot at NASA’s Langley Research Center in Hampton, Virginia, where he supported airborne science missions. This is the first spaceflight for Delaney.

The Crew-13 mission also is the first spaceflight for Kutryk. Prior to his selection as a CSA astronaut in 2017, he served as a CF-18 fighter pilot, flying missions in support of Canada’s NATO, U.N., and North American Aerospace Defense Command commitments. A native of Fort Saskatchewan, Alberta, Kutryk also worked as an experimental and operational test pilot at the Aerospace Engineering Test Establishment in Cold Lake, Alberta. Kutryk received a bachelor’s degree in mechanical engineering from the Royal Military College of Canada in Kingston, Ontario, and he is a distinguished graduate of the United States Air Force Test Pilot school in Edwards, California. He has master’s degrees in space studies, flight test engineering, and defense studies.

This mission will be Teteryatnikov’s first trip to the orbiting laboratory. He graduated from the Naval Academy, St. Petersburg, Russia, in 2011 as an engineer specializing in ship power plant operations. Before his selection as a test cosmonaut, Teteryatnikov served in various naval engineering roles, including undersea vessels and specialized engine room operations. He was selected for the Gagarin Research and Test Cosmonaut Training Center Cosmonaut Corps in 2021 and has served as a test cosmonaut since 2023.

For more information about the mission, visit:

https://www.nasa.gov/mission/nasas-spacex-crew-13

-end-

Joshua Finch / Jimi Russell
Headquarters, Washington
202-358-1100
joshua.a.finch@nasa.gov / james.j.russell@nasa.gov

Leah Cheshier / Anna Schneider
Johnson Space Center, Houston
281-483-5111
leah.d.cheshier@nasa.gov / anna.c.schneider@nasa.gov

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Last Updated
Jul 20, 2026
Editor
Jessica Taveau
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Establishing a VTE Risk Score for Astronauts Algorithm

Spontaneous echo contrast (SEC) grade 3 with peripheral echogenicity.
NASA/Pavela

In April 2026, NASA’s Office of the Chief Health and Medical Officer (OCHMO) initiated a working group to review updated VTE case information, additional data gathered revealing altered blood flow status within a cohort of astronauts, and discuss progress of research and clinical activities intended to mitigate the risk of VTE during spaceflight with new evidence-based clinical practice recommendations.

Recommendations

The following is a summary of the working group’s recommendations:

  • The working group’s conclusions emphasized that stasis in the left internal jugular vein (IJV) is consistently viewed as a dominant risk factor for VTE in microgravity, though there is active debate regarding the relative contributions of slow qualitative flow, endothelial factors and/or retrograde flow.
  • Limitations of current in-flight ultrasound capabilities to accurately measure stasis/slow flow was cited as a concern, especially if using only stasis as a factor for indicating the need for prophylaxis.
  • Additional review of assessing stasis with ultrasound in-flight was recommended.
  • After reviewing the risk factors, additional discussions following the working group led to the majority of the panel agreeing that stasis and retrograde flow warranted use of prophylaxis.
  • The working group also recommended assessing all other risk factors other than stasis to also determine when prophylaxis is warranted.
  • Based on a literature review and summary of the panel contributions, a VTE Risk Score for Astronauts Algorithm was developed, which includes providing anticoagulation prophylaxis for stasis alone, or a combination of other thrombosis risk factors that are weighted by terrestrial literature.

Risk of Venous Thromboembolism During Spaceflight

NASA initially formed a working group in October 2024 after diagnosing venous thromboembolisms (VTEs) in astronauts during ISS missions. Experts reviewed case data, updated Clinical Practice Guidelines, and examined possible causes.

Approximate location of identified thrombi in crewmembers.
Source: Modified from Cerebral Sinus Venous Thrombosis – University of Colorado Denver
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