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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.”

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Trump border advisor says ICE to deploy to U.S. airports Monday

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What began as a social media post from President Trump on Saturday has grown quickly into a full-scale plan to deploy ICE agents to U.S. airports.

Amid a partial government shutdown, TSA lines have grown to be hours long at some U.S. airports, creating problems for travelers across the country. Call-out rates have started to increase at some airports, and the U.S. Department of Homeland Security said at least 376 TSA agents have quit since the partial shutdown began Feb. 14.

White House border advisor Tom Homan said that ICE plans to dispatch agents to airports as soon as Monday, and that he was working with other officials to determine where to send agents.

“It’s a work in progress,” Homan said during a Sunday appearance on CNN. “But we will be at airports tomorrow helping TSA move those lines along.”

Homan stressed that ICE agents would provide support where possible, so that TSA staffers could better fulfill specialized positions.

“I don’t see an ICE agent looking at an X-ray machine, because they are not trained in that,” Homan said.

In a statement Sunday, a spokesperson for Gov. Gavin Newsom said Trump’s push to send ICE into airports “is proving the problem in real time.”

“ICE has become the president’s lawless, under-trained, personal police force, deployed to serve his agenda — not the law,” according to the statement. “That’s exactly why it needs to be reined in.”

The plans were seemingly first set in motion following Trump’s social media post on Saturday that read, “If the Radical Left Democrats don’t immediately sign an agreement to let our Country, in particular, our Airports, be FREE and SAFE again, I will move our brilliant and patriotic ICE Agents to the Airports where they will do Security like no one has ever seen before.”

Expanding the argument for the deployment beyond simply alleviating long lines at TSA, Trump said ICE would also oversee “the immediate arrest of all Illegal Immigrants who have come into our Country, with heavy emphasis on those from Somalia.”

Speaking from the floor of the Senate on Sunday, Democratic Leader Chuck Schumer (D-N.Y.) said, “ICE agents, who are untrained and have caused problems everywhere they’ve gone, lurking at our airports — that’s asking for trouble. And it will certainly make the chaos at our airports worse.”

At the core of the partial shutdown is a disagreement between congressional Republicans and Democrats over continued funding for the Department of Homeland Security.

Republicans want to fund all parts of Homeland Security, while Democrats want that funding tied to ICE reforms. Democrats have put forward bills to fund key components of Homeland Security, including the TSA, which Republicans have opposed.

Though negotiations are said to be ongoing, the shutdown could drag on even longer as Congress is scheduled for a two-week recess beginning at the end of this week, and each side blames the other for the continued shutdown.

In a social media post, Vice President JD Vance wrote, “We’ve all seen the chaos unleashed by Democrats at airports across the country. It’s preposterous that Chuck Schumer continues to hold TSA funding hostage.”

Senator Patty Murray (D-Wash.), vice chair of the Senate Appropriations Committee, said in a statement, “Right now, Republicans are holding TSA agents’ paychecks hostage because they want to provide more money to ICE, without basic reforms to protect Americans’ rights and safety.”

Appearing on MS NOW on Saturday, before Homan’s confirmation that ICE would be sent to airports, Rep. Eric Swalwell (D-Dublin) said, “Americans don’t want ICE in our communities, they don’t want them in our airports. They by and large, as I support, want ICE to be abolished.”

Swalwell did not respond to a request for comment on Sunday, but posted on X, saying, “Pay TSA. Do not pay ICE.”

In a Sunday interview with ABC, Transportation Secretary Sean Duffy said, “Democrats want to see long lines at airports as leverage. President Trump’s trying to take that leverage away and not make the American people suffer.”

The pushback to the White House’s plans to put ICE in airports was immediate.

Rep. Bennie G. Thompson (D-Miss.), ranking member of the Committee on Homeland Security, released a statement that read, “Masked, armed police at travel checkpoints is a hallmark of dystopian movies. Now, Donald Trump is threatening to bring this tool of fascism to America. He is manufacturing chaos at airports for political leverage and trying to force Democrats to accept unaccountable secret police at security checkpoints around the country.”

Also speaking to CNN on Sunday, House Democratic Leader Hakeem Jeffries said, “The last thing that the American people need are for untrained ICE agents to be deployed at airports all across the country, potentially to brutalize or, in some instances, kill them. We’ve already seen how ICE conducts itself.”

In a statement Sunday, Everett Kelley, national president of the American Federation of Government Employees, which represents TSA officers, said, “More than 50,000 TSA employees have worked without pay for over five weeks. Hundreds have quit. And Washington’s answer isn’t to pay them. It’s to send ICE agents to do their jobs.

“ICE agents are not trained or certified in aviation security,” Kelley added. “You cannot improvise that. Putting untrained personnel at security checkpoints does not fill a gap. It creates one. … Congress has the power to fund TSA today. It’s time for them to stop playing politics and do their jobs.”

Representatives from Los Angeles International Airport did not immediately respond to a request for comment. A spokeswoman for Orange County’s John Wayne Airport said she was not currently aware of any communication or Homeland Security guidance on the proposed plan.

A spokesperson for San Francisco International Airport said airport officials have not yet received anything specific from Homeland Security about a deployment of ICE agents. He said SFO security personnel are not part of TSA, and as a result, the airport has not had any checkpoint backups.

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Who Is Antigone? The 2500-Year-Old Rebel With a Cause.

“Antigone” gave us the original “bad girl,” but its themes go beyond that. How do adaptations keep making Sophocles’ ideas about democracy and theater new?

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How Will Martian Gravity Affect Skeletal Muscle?

NASA and the China National Space Agency (CNSA) plan to send astronauts to Mars as early as the next decade. Naturally, this ambitious goal requires a great deal of planning, research, and the anticipation and preparation for all potential challenges in advance. Among them, astronaut health and safety are paramount. In addition to the hazards associated with the long transit times – radiation and the effects of long periods in microgravity – there’s the issue of Mars itself. Aside from exposure to elevated radiation levels, Martian gravity is about 38% of Earth’s.

This has the potential to lead to long-term health risks. An international team of researchers is currently studying how Martian gravity will affect a key aspect of human health: skeletal muscle. This muscle, which is the most abundant tissue in the human body (accounting for more than 40% of total body mass), is essential to movement and metabolic health. What’s more, this tissue is especially sensitive, and lower gravity could potentially result in the substantial loss of muscle strength, size, and performance. It is therefore important to determine how this muscle tissue will fare in the Martian environment.

The research team was composed of scientists from the Institute of Medicine at the University of Tsukuba, Tohoku Medical Megabank Organization, the Advanced Research Center for Innovations in Next-GEneration Medicine (INGEM), the Beth Israel Deaconess Medical Center, the Brigham and Women’s Hospital, the Japan Aerospace Exploration Agency’s (JAXA) Space Environment Utilization Center, and multiple universities. The results of their research appeared in the journal Science Advances

*Experiments aboard the International Space Station with mice showed that muscle atrophy can be mitigated and prevented in lower gravity. Credit: NASA/ESA–T. Pesquet*

For their experiment, the team studied how lower gravity affected skeletal muscle tissue in 24 mice sent to JAXA’s Kibo experimental module. These mice were then placed in a JAXA-developed centrifuge device called the Multiple Artificial-gravity Research System (MARS), where they were subjected to four different levels of gravity – microgravity, 0.33 g, 0.67 g, and 1 g – over a 28-day period. The mice were subjected to pre-flight testing before launch at NASA’s Kennedy Space Center, where they were returned for post-flight sampling.

These samples were then examined by scientists at the Metabolism and Muscle Biology Lab in the Department of Nutrition at the University of Rhode Island (URI). As Professor Marie Mortreux, who leads the MMBL, attested in a Rhoby Today news story:

While we can simulate spaceflight on Earth in humans, it’s extremely complicated and costly. We have centrifuges that can be used to temporarily expose humans to certain gravity levels, but it is not homogeneous nor constant. We used gravity levels that were equally separated, to have a better picture of the dose-response of each system to gravity. The test group that was exposed to 0.33g was extremely close to Martian gravity (0.38g). Our findings for that group can be translated into actions to enable Mars exploration.

Mortreux and her team analyzed the weight, strength, and movement of the mice once they were returned to NASA’s Kennedy Space Center. Their analysis showed that 0.33 g mitigated spaceflight-induced muscle atrophy, with full prevention at 0.67 g. They also measured the mice’s forelimb grip strength using Electrical impedance myography (EIM), which showed that 0.67 g was sufficient to maintain muscle performance.

*The research team at Kennedy Space Center confirming the protocol and timing prior to receiving animals for post-flight sampling. Credit: URI*

Their results collectively demonstrated that 0.67 g is a critical threshold for mitigating muscle atrophy caused by prolonged spaceflight. In addition, an analysis of the mice’s blood plasma identified 11 metabolites that showed gravity-dependent changes, suggesting they could serve as potential biomarkers to monitor physiological adaptations in astronauts. This work builds on previous research she performed with Professor Mary Bouxsein (a co-author on the study) at Harvard Medical School.

Whereas Dr. Bouxsein developed the ground-based mouse model of partial gravity in the early 2010s, Montreux developed the rat model of partial gravity at Harvard. As such, the two are well-acquainted with the impact that different gravity levels have on musculoskeletal tissues.

“Since this mission aimed to assess gravity as a continuum, we were perfectly positioned to see if our ground-based results had similar outcomes when reduced mechanical loading was applied in orbit,” said Montreux. “Working with an international team was challenging and exciting. I think my experience working in Italy, France, and the United States prepared me for those big-scale collaborations.”

One takeaway from this study is that future missions to Mars will need to be mindful of mitigating skeletal muscle loss during the long transit between Earth and Mars. For astronauts to maintain mobility, muscle strength, and carry out regular science operations. The same holds true for their physical health upon returning to Earth.

These findings suggest that rotating toruses would be a wise addition to any future spaceflight plans, a la NASA’s Non-Atmospheric Universal Transport Intended for Lengthy United States Exploration (NAUTILUS-X) and similar aspects.

Further Reading: Rhody Today, Science Advances