A new study has confirmed that a black hole eight billion light years away is zipping away from its galaxy’s center at 2,000 kilometers per second, or more than 4.5 million miles per hour. The result also provides, for the first time, very strong evidence that it is possible for two black holes to merge.

The galaxy where this is happening, named 3C 186, was first discovered in 2017. Initial observations suggested that 3C 186 was the result of two galaxies (and their respective black holes) merging. However, there were still other possible explanations for the physical distance detected between the galaxy’s center and the black hole. The new study, published in Astronomy and Astrophysics, strongly supports only one of the remaining scenarios: that two black holes merged and the resulting black hole is moving away from the galaxy’s center.

“This is probably the most clear-cut case” illustrating this phenomenon that scientists are aware of, says Eileen Meyer, associate professor of physics. She is co-lead of the new study with Gianluca Castignani at the University of Bologna.

Speedy departure

The two major findings—the black hole merger and its ouster from the galaxy’s center—are related. Theorists have predicted that if two black holes were to merge, they would release huge amounts of energy in the form of gravitational waves, Meyer explains. 

Sometimes, “depending on how the black holes are spinning and their relative mass and how they’re oriented,” she says, that energy is not equally distributed in all directions. If there is “a lot of gravitational wave energy in one direction, there is consequently going to be literally kinetic energy given to the black hole in the other direction.” That means the black hole is going to move—in this case, very quickly.

“There were basically two pieces of evidence that made this story come together,” Meyer says. First, an earlier paper used high-resolution imaging from the Hubble Space Telescope to establish the physical offset between the black hole and the galaxy’s center. “That in itself might not have been weird,” Meyer says, because after two galaxies merge, “stuff is flying all over the place,” and it can take time for the black hole to settle in the center of the new, merged galaxy, she explains.

However, Castignani and Meyer’s new paper confirmed a critical second finding: the velocity of the black hole. 

The imaging plus the velocity comes as close as you can in astronomy to proving the scenario that Meyer and her colleagues favor: a merged black hole has been kicked out from the center of its galaxy as a reaction to gravitational wave energy headed in the opposite direction. This is the first time both physical offset and velocity have come together so convincingly.

Shifting understanding

Meyer and colleagues figured out the velocity of the black hole by measuring the radiation emitted by carbon monoxide (CO) gas in the galaxy. They used a ground-based observatory called the Northern Extended Millimeter Array (NOEMA), located in the French alps, to collect the measurements.

The wavelength of the radiation emitted from CO gas increases as it travels across the universe from 3C 186 to NOEMA, a phenomenon referred to as red-shift. The farther away something is, the greater the red-shift will be. Galaxy 3C 186 is stable overall, so one would expect the radiation it emits to all have the same red-shift. However, NOEMA detected radiation with a smaller red-shift coming from the gas near the black hole. That indicates the black hole is moving quickly toward NOEMA relative to the center of 3C 186—in this case, at 2,000 km/s.

Detecting the velocity “was the thing that made us say, maybe this isn’t just some post-merger weirdness, but instead the black hole is offset because it has traveled out from what should have been the center of the galaxy,” Meyer says.

Detective work

The research team wasn’t looking specifically for the galaxy 3C 186 when their study began. The initial observations came from what’s called a “snapshot proposal” with the Hubble Space Telescope. 

Sometimes space-based observatories like Hubble make observations that require multiple orbits around Earth. But between these major observations, scientists can utilize smaller chunks of time for other studies that need only a quick “snapshot.” The data the researchers receive aren’t of the same quality as longer exposures, but they can be very useful. 

In this snapshot study, the researchers received images of a couple dozen of their 100 or so preferred targets as Hubble traversed a partial orbit. “This black hole merger was observed by chance,” Meyer says. “There were odds against us.”

In astronomy, there can be pressure to choose a “safe” proposal, where researchers seek new data on a particular space object that’s already known to be interesting. In snapshot proposals, you often don’t know what you’re going to find, Meyer says, “but sometimes you need to take a chance on the unknown to make new discoveries.’”

As it turns out, this time they made a major discovery, adding to the story of how black holes merge. “When you build a story out of the evidence, it’s a bit like detective work,” Meyer says.

For systems so far away, scientists often can’t directly image everything that’s happening. Instead, Meyer explains, they have to infer what’s going on from the light produced, and it can be hard to narrow down the possible scenarios for what’s actually happening. This new study takes a big step forward by translating theoretical predictions into actual observed phenomena at galaxy 3C 186.

Finding the first

The new finding confirming that two black holes merged, and that the resulting black hole is traveling away from the galaxy’s center, “is actually very important,” Meyer says. “People always want the evidence for the scientific story, and now we have that evidence.”

The results are also encouraging for a new major mission led by the European Space Agency. The Laser Interferometer Space Antenna (LISA) will observe gravitational waves from space and could help detect more instances of merged black holes at the centers of galaxies.

“If you find one, you know there’s got to be many more,” given the sheer number of galaxies out there, Meyer says. “The first one is definitely important.”

Meredith Oyen, Associate Professor of History and Asian Studies, UMBC

U.S. House Speaker Nancy Pelosi hasn’t confirmed when – or even if – she is to visit Taiwan. Yet such is the sensitivity over the island’s status that reports of her possible trip have resulted in a warning by China of “serious consequences” and a suggestion by President Joe Biden that the visit was “not a good idea.” Amid the rhetoric and heightened tensions, Taiwan is conducting military drills.

The comments follow a report by the Financial Times that Pelosi planned to take a delegation to Taiwan in August. The outlet based its report on six people “familiar with the situation”; Pelosi’s spokesperson has said she could neither confirm not deny the reported trip.

As someone who has long studied the U.S.‘s delicate diplomatic dance over Taiwan, I understand why this reported trip has sparked reaction in both Washington and Beijing, given the current tensions in the region. It also marks the continuation of a process that has seen growing U.S. political engagement with Taiwan – much to China’s annoyance.

Cutting diplomatic ties

The controversy over reports of Pelosi’s potential visit stems from the “one China” policy – the diplomatic stance under which the U.S. recognizes China and acknowledges Beijing’s position that Taiwan is part of China. The policy has governed U.S. relations with Taiwan for the last 40-plus years.

In 1979, the U.S. abandoned its previous policy of recognizing the government of Taiwan as that of all of China, instead shifting recognition to the government on the mainland.

As part of this change, the U.S. cut off formal diplomatic ties with Taiwan, with the U.S. embassy in Taiwan replaced by a nongovernmental entity called the American Institute in Taiwan.

The institute was a de facto embassy – though until 2002, Americans assigned to the institute would have to resign from U.S. State Department to go there, only to be rehired once their term was over. And contact between the two governments was technically unofficial.

As the government in Taiwan pursued democracy – starting from the lifting of martial law in 1987 through the first fully democratic elections in 1996 – it shifted away from the assumption once held by governments in both China and Taiwan of eventual reunification with the mainland. The government in China, however, has never abandoned the idea of “one China” and rejects the legitimacy of Taiwanese self-government. That has made direct contact between Taiwan and U.S. representatives contentious to Chinese officials.

Indeed, in 1995, when Lee Teng-hui, Taiwan’s first democratically elected president, touched down in Hawaii en route to Central America, he didn’t even set foot on the tarmac. The U.S. State Department had already warned that the president would be refused an entry visa to the U.S., but had allowed for a brief, low-level reception in the airport lounge during refueling. Apparently feeling snubbed, Lee refused to leave the airplane.

Previous political visits

Two years after this incident came a visit to Taiwan by then-House Speaker Newt Gingrich.

Similarly to the possible Pelosi visit, the one by Gingrich annoyed Beijing. But it was easier for the White House to distance itself from Gingrich – he was a Republican politician visiting Taiwan in his own capacity, and clearly not on behalf of then-President Bill Clinton.

Pelosi’s possible visit could be different, because she is a member of the same party as President Joe Biden, and China may assume she has Biden’s blessing, despite his comments to the contrary.

Asked on July 20 about his views on the potential Pelosi trip, Biden responded that the “military thinks it’s not a good idea right now.”

The comment echoes the White House’s earlier handling of a comment by Biden in which he suggested in May 2022 that the U.S. would intervene “militarily” should China invade Taiwan. Officials in the Biden administration rolled back the comment, which would have broken a long-standing policy of ambiguity over what the U.S. would do if China tried to take Taiwan by force.

Similarly with Pelosi, the White House is distancing itself from a position that suggests a shift in U.S.-Taiwanese relations following a period in which the U.S. had already been trying to rethink how it interacts with Taiwan.

Shifting policy?

In 2018, Congress passed the bipartisan Taiwan Travel Act. This departed from previous policy in that it allowed bilateral official visits between the U.S. and Taiwan, although they are still considered to be subdiplomatic.

In the wake of that act, Donald Trump’s Health and Human Services secretary, Alex Azar, became the highest-ranking U.S. official to visit Taiwan since 1979. Then in 2020, Keith Krach, undersecretary for economic growth, energy and the environment, visited Taiwan.

And in April 2022, a U.S. congressional delegation visited Taiwan. Pelosi herself was reportedly due to visit the island that same month, but canceled after testing positive for COVID-19.

Each of these visits has provoked angry statements from Beijing.

A high-profile visit – even one without the public backing of the White House – would signal support to the island at a time when the invasion of Ukraine by Russia has raised questions over the international community’s commitment to protect smaller states from more powerful neighbors.

Meanwhile, the erosion of democracy in Hong Kong has undermined China’s commitment to the idea of “one nation, two systems.” The principle, which allowed Hong Kong to maintain its economic, political and social systems while returning to the mainland after the end of British rule, had been cited as a model for reunification with Taiwan. The Chinese Communist Party also plans to hold its 20th congress in the coming months, making the timing sensitive for a Taiwan visit from a high-profile U.S. political figure such as Pelosi.

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Meredith Oyen, Associate Professor of History and Asian Studies, University of Maryland, Baltimore County

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Dear Faculty and Staff,

As we prepare for the new academic year and the temperatures rise outside, we recognize that everyone needs a break. Join the Professional Staff Senate and Campus Life for Yappy Hour!

All faculty and staff are welcome to bring their pets to the Quad on Tuesday, August 2, from 4 p.m. -- 6 p.m. Come to socialize your pet with other pets or for a break to play with your coworkers' pets! Free giveaways, treats, and sniffs for all!

If you have questions, please contact Morgan Simonds at simonds1@umbc.edu.