News

This Pair Of Brown Dwarfs Can’t Get Enough Of Each Other

Binary stars are known to transfer mass to one another. In extreme cases, mass transfer can even cause a supernova explosion. That happens when a white dwarf draws matter from a companion.

But astronomers have never seen a pair of brown dwarfs transferring mass.

Brown dwarfs are stuck in a no man’s land between planet and star. They’re more massive than gas giants, but less massive than the smallest main sequence stars, red dwarfs. Brown dwarfs are sometimes called failed stars or substellar objects because they’re simply not massive enough to trigger and sustain hydrogen fusion like main sequence stars do. Instead, they emit some light and heat due to deuterium fusion.

This artist’s illustration shows the relative sizes of the Sun, a low mass star, a brown dwarf, Jupiter, and the Earth. The image is to scale. Image Credit: NASA, ESA, SDO, NASA-JPL, Caltech, A.Simon (NASA-GSFC); Designer: E. Wheatley (STScI)

Astronomers aren’t certain how common brown dwarfs are because they’re so dim and difficult to detect. But estimates suggest that the Milky Way could contain up to 100 billion of them. Like other stars, many of these billions of brown dwarfs are in binary pairs.

New research in The Astrophysical Journal Letters focuses on ZTF J1239+8347, a binary brown dwarf pair in an especially close orbit with one another. The research is titled “A Mass Transferring Brown Dwarf Binary on a 57 Minute Orbit,” and the lead author is Samuel Whitebook. Whitebook is a grad student in the Division of Physics, Mathematics, and Astronomy, at Caltech.

The pair of brown stars has an orbital period of 57.41 minutes. That’s an extremely tight orbit, and observations with NASA’s Swift Observatory and other facilities show that the two brown dwarfs are in a stable mass-transferring relationship. The researchers identified a hot spot on the surface of the donor brown dwarf that moves as the pair orbits each other.

There are two possible outcomes for this arrangement.

In one scenario, the accreting BD will continue to gain mass until it becomes massive enough to fuse hydrogen. It will then be a main sequence star.

In the other scenario, the pair will eventually merge and become one. This will also result in a more massive, main sequence star. In both cases, there’s an increase in luminosity.

“The failed stars get a second chance,” lead author Whitebook said in a press release. “Brown dwarfs don’t have internal engines like stars do, but this result shows they can exhibit very interesting dynamic physics.”

Mass transfer between binary stars isn’t a mysterious process. The more massive partner pulls on the atmosphere of the less massive partner. Eventually, the material overflows from the donor’s Roche lobe and becomes part of the accretor.

“When one star’s gravity is overcome by the other’s, matter starts flowing from the less dense star to the denser star,” Whitebook says. “It’s like the matter sloughs off through a nozzle.”

This is the first time astrophsyicists have detected mass transfer like this in a brown dwarf binary. In fact, it’s so unusual that others in the astronomy research community are struggling to accept the findings. “These are very exotic objects,” said co-author Thomas Prince, also from the Division of Physics, Mathematics, and Astronomy at Caltech. “We’ve told some of our colleagues about them, and they didn’t believe such a thing exists.”

The authors didn’t believe their findings without hesitation. They considered other explanations for the observations. It’s possible that one of the objects isn’t actually a brown dwarf, but is instead a compact object like a neutron star. They rejected this because there would be brighter x-ray emissions.

A cataclysmic variable is also another candidate. It involves a white dwarf accreting material from a secondary star, in this case a brown dwarf. But the optical spectra goes against this, as does the hot spot. “Additionally, in this configuration, it is impossible for the hot spot to be on an irradiated BD, as the irradiating WD would be visible in the optical spectrum at all times,” the authors explain.

They settled on an accreting BD binary because it fits the evidence best.

The system is also valuable scientifically because it can be a test case for mass transfer. “ZTF J1239+8347 provides a potentially valuable probe of the dynamics of stable mass transfer at the lowest detectable mass scales,” the authors write.

*This figure compares ZTF J1239+8347’s orbital period and mass to double white dwarfs (DWDs) and black widow neutron star—substellar object binaries (BWs). It also shows that typical brown dwarf binaries have longer orbital periods than ZTF J1239+8347. Image Credit: Whitebook et al. 2026. ApJL*

ZTF J1239+8347 is pretty close, only about 1,000 light-years away. It’s a good candidate for more observations with the JWST. “Future observations of the system with the James Webb Space Telescope (JWST) could constrain the temperature of the accretor atmosphere better and could detect the atmosphere of the donor system,” the authors write. These observations would also give better measurements of the system’s mass ratio. Better measurements of the hot spot would also provide constraints on the mass transfer rate.

But like many things in astronomy and astrophysics, finding more examples of a binary brown dwarf pair experiencing mass transfer will lead to a deeper understanding. Fortunately, the Vera Rubin Observatory will likely find more of these binary stars.

“We expect the Vera Rubin Observatory to detect dozens more of these objects,” Whitebook says. “We want to find more to understand the population and how common it is. We predict this happens more than you think.”

News

ICE shootings protested in Pasadena on National Day of Action

urlhttps3A2F2Fcalifornia times brightspot.s3.amazonaws.com2F2d2F392F16f7756b428785707935b1a3

Approximately 50 demonstrators gathered Saturday morning in Pasadena as part of a national action to honor lives lost during immigration enforcement operations and in detention centers during the Trump administration.

They wore fliers around their necks, hung with yellow thread, bearing the smiling faces and names of some of the 75 people who have died since January 2025.

“Killed by ICE” was printed above a photo of each person, including local resident Roberto Carlos Montoya Valdez, a 52-year-old killed while trying to flee immigration agents who descended on a Home Depot in Monrovia last year.

The Los Angeles residents, part of the San Gabriel Foothills Indivisible group, carried American flags and held signs that read “No ICE No War” and “Stop ICE Murders.”

“Good morning, Pasadena,” Betsy Hanger, an organizer with the group, boomed into a megaphone as she walked through an intersection. “Honk for democracy. Honk if you want ICE off our streets now.”

A chorus of horns sounded as drivers signaled their support.

Organizer Andra Clarke held a banner in each hand that read “Neighbors Say ICE Out.” The sign around her neck carried the name and photo of Francisco Gaspar-Andrés, a 48-year-old who died in a Texas detention center in December.

Clarke, 61, said the group has been gathering at the intersection of Colorado Boulevard and Fair Oaks Avenue every Saturday since March. Last weekend, they celebrated civil rights activist John Lewis.

This Saturday, though, their focus was aimed at ICE.

“Now 75 people have died at the hands of ICE,” Clarke said. “We were originally told, ‘Oh they’re going to go after the criminals, the people who are the worst of the worst.’ That’s a lie; that is not what’s happening.

“They’re targeting communities, they’re targeting people of color. It’s fascism. … Anybody who cares about humanity should care about what’s happening.”

Clarke said it hit her hard when she learned of the two recent deaths at the hands of ICE.

The event was also a vigil honoring 52-year-old Lorenzo Salgado Araujo, who was killed by an ICE agent in Houston on July 7 while driving his construction crew to a job site, and Johan Sebastian Guerrero, 25, who was fatally shot by an ICE officer in Maine during a traffic stop earlier this month.

“It’s like, again? It just doesn’t end. It feels like it never ends — the evil.”

Shortly before noon, Clarke used a megaphone to read aloud the names of the dozens who have died. After each name read, Hanger struck a singing bowl, the vibrations sounding out in the corner where they stood. At times, she read “unidentified man” or “four unidentified women.”

Next to them was a poster board with a photo of Daphy Michel, a 31-year-old woman found unresponsive at a bus shelter in Pittsburgh after ICE released her “into cold winter conditions and no care for mental health episodes or notice to relatives.”

“Let’s take a moment of silence for all those who were taken,” Clarke said, bowing her head.

Among those gathered to listen was Leticia Lopez, a 65-year-old South Pasadena resident whose voice trembled as she talked about the impact of hearing about another arrest or death tied to enforcement operations.

“It gets me to the core,” she said, striking her chest. “It’s not getting any better, it’s getting worse. I just feel like I need to do something.”

Lopez, who wore a shirt that read “Immigrants are not criminals but the president is,” said her mother and grandmother were forcefully repatriated from Arizona to Mexico.

Her mother, who was raised in Mexico, later met her father there. He moved to the U.S. in the 1950s as a bracero. Hearing the stories of today, she said, “triggers everything that they went through.”

“When I see it happening, it’s a generational trauma that I feel,” she said. Lopez said people around her are carrying passports and documents in public to prove they’re citizens.

“Because they’re afraid they might be profiled, picked up, kidnapped by ICE. When my son goes out, I worry,” she said of her 28-year-old.

Later that afternoon, about four miles away outside of Home Depot in Pasadena, organizers staked in the ground dozens of white crosses that bore photos of the dead — the majority of them men. Attendees of the vigil laid flowers at the crosses in a makeshift cemetery.

“Shot dead by ICE,” read one with a photo of Keith Porter Jr., who was killed by an off duty ICE officer in California.

Several of them contained details of how the deaths unfolded. A man killed after a tractor trailer struck him as he fled an ICE raid in Florida. A Cuban immigrant who died in a detention center (his death was later ruled a homicide). A Mexican national who fell 30 feet to his death during a raid in California.

Among the photos on crosses were Renee Good and Alex Pretti.

“Are we going to wait until 70 more die to do something?” asked Marlom Portillo, an educator with the National Day Laborer Organizing Network, as he staked more crosses into the ground.

“What they want us to do is forget them,” Portillo added. “We will never get tired of denouncing this atrocity.”

“There are more people who died than there are people here protesting,” Kathleen Vallee, a Monrovia resident, observed to her friend. “And that says a lot about us.”

Vallee said when she attended the “No Kings” protest, it was “jam-packed.” Only a dozen people had gathered around 20 minutes into the vigil.

“It turns my stomach,” Vallee said, hands clasped. “This just seems to be seeping up from the sewer into our democracy and that motivates me.”

As the small crowd assembled, demonstrators carried signs that read “Every person is sacred,” “we keep us safe” and “neighbors say ICE out.” One woman carried a handmade sign that read: “Who will they come for next?”

Sheri Lochner, a 64-year-old Monrovia resident, is part of East Pasadena Community Defense Corner, a small group that “provides support and a sense of community” for day laborers.

Lochner said she watched as immigrant agents took six or seven men at an Oct. 1 ICE raid at the Monrovia Home Depot.

“So un-American,” Lochner said, as she scanned the rows of crosses. “This isn’t right.”

She added that her mom, who voted for Trump the first time, agreed with her.

“I speak up, I will not be silent,” she added.

News

Inside the Rushed Effort to Get Trump His New Air Force One

A New York Times investigation found that President Trump’s push to speed delivery of the aircraft led to ballooning costs and trade-offs in safety features.

News

Lucky 13! Starship Deploys Starlink Satellites and Splashes Down Intact

SpaceX’s Starship super-rocket deployed operational next-generation Starlink satellites for the first time during its 13th flight test, which addressed snags that arose in the previous test.

The 407-foot-tall, two-stage rocket rose from its Starbase launch pad in Texas at 5:51 p.m. CT today (10:51 p.m. UTC), with all 33 Raptor engines firing on the Super Heavy booster. On the way up, the rocket set a record for maximum dynamic pressure, also known as Max-Q.

Minutes after liftoff, the Starship upper stage — known as Ship — separated to continue on the flight test’s trajectory, and then the booster relit its engines for a controlled splashdown in the Gulf of Mexico. SpaceX launch commentator Dan Huot noted that not all of the engines fired up as planned — making for a splash that was a bit spicier than expected but still safe.

During the next phase of the test, Ship sent out 20 operational Starlink V3 satellites from a deployment system that’s been nicknamed the “Pez Dispenser.” For about 20 minutes, SpaceX’s engineering team ran a series of tests to check the deployment of solar arrays and see how the satellites were able to communicate with other spacecraft in the telecom network using laser systems.

“Not only were we able to make contact with all 20, but we also made comms over lasers with all of them as well,” SpaceX engineer Kate Tice said. “So, that is awesome.”

The satellites weren’t meant to stay in orbit. After the tests were completed, all 20 re-entered the atmosphere and burned up. But the data gathered during the tests will help SpaceX ensure that future batches of Starlink V3 satellites work properly.

Starlink V3 satellites are built to download data at speeds of up to 1 terabit per second, which marks a substantial technological advance over the V2 satellites that make up the bulk of the Starlink constellation. Adding V3 satellites to the network will upgrade Starlink’s capacity for direct-to-device services.

After satellite deployment, the upper stage executed a relight of one of its six Raptor engines in mid-flight, and then descended through the atmosphere to a splashdown in the Indian Ocean. On the way down, Ship’s heat shield weathered fiery flashes of plasma that made for quite a fireworks show on the in-space video transmitted down to Earth via Starlink. At the very end, the upper stage settled down intact in the water, spouting flames as it floated.

“That is a first. That is the softest splashdown we have ever had with a Starship there in the Indian Ocean,” Huot said. “This is a dream scenario for the team that’s trying to get this heatshield data.”

This marked the second test of SpaceX’s beefed-up Starship V3 rocket. The previous test in May followed a similar flight profile and was rated a success, but SpaceX made some modifications to systems on the Super Heavy booster as well as on the upper stage to address engine performance issues.

SpaceX’s initial attempt to launch the 13th flight test was aborted a week ago, at the moment of ignition, when four Raptor engines failed to start up for launch. After the scrub, SpaceX found six booster engines that raised concerns and replaced them for today’s second try.