Second only to black holes, neutron stars – incredibly dense star remnants – are the densest objects in the universe. When neutron stars collide, they create ripples in the fabric of space and time in a way that we can detect on Earth.

We can then use these ripples to measure one of the universe’s most fundamental but elusive properties – how fast it is expanding. This is called the Hubble constant, and scientists have pursued and debated it for decades.

In recent years, the debate has intensified. Scientists using different techniques keep arriving at divergent answers. This growing problem, known as the “Hubble tension”, has become one of the biggest challenges in modern cosmology.

In a study published in The Astrophysical Journal today, we have developed a new approach in an attempt to pin down the Hubble constant. To do so, we re-examined gravitational waves caused by a dramatic collision of two neutron stars.

We believe our results provide the most precise measurement of the Hubble constant to date using the gravitational wave method.

Why do we need the Hubble constant?

Knowing how fast the universe is expanding is fundamental for astronomers. It sets the cosmic scale for our measurements, enabling us to determine the true distance and size of astrophysical objects. Even more profoundly, it tells us about how the universe began and how it could end.

Given its importance, we’ve been trying to measure the Hubble constant with several methods. According to the standard theory of how the universe evolves, all methods should find the same answer.

For years, the various methods appeared to broadly agree, but with large margins of error. Within the last couple of decades, astronomers have made great strides to increase precision and reduce uncertainty.

Some teams achieved precise measurements using leftover light from the Big Bang. This method is described as using the “distant universe”, because the light has travelled for nearly the entire age of the universe to reach us.

Other teams have used light from much nearer objects, such as pulsating stars and supernovae, to make their own precise measurements. These are known as “nearby universe” measurements.

Shockingly, these two sets of high-precision measurements disagree – by a lot. The distant universe measurement puts the Hubble constant at 67–68km/s per megaparsec (a vast unit of astronomical distance: 3.26 million light years). The near universe result is higher – around 72–74km/s per megaparsec.

This is the Hubble tension.

What does it mean? Could it be something has gone awry in one or both methods? Despite intense scrutiny, nobody has found any mistakes. Alternatively, our understanding of how the universe evolves may be missing something fundamental and we need “new physics” to resolve it.

To settle this cosmic debate, new and independent methods of measuring the Hubble constant are highly sought after.

Enter gravitational waves

Gravitational waves offer an entirely independent way to measure the expansion of the universe. These large ripples in the fabric of space-time are produced when extremely dense objects – such as black holes – collide.

Neutron stars are the dense remains of stars that exploded into supernovas, but were not quite heavy enough to collapse into black holes afterward. The first gravitational waves were detected from colliding black holes just over a decade ago.

In 2017, scientists made history when they also detected gravitational waves from a neutron star collision, labelled GW170817. Unlike a black hole collision, it produced a glow of light, enabling astronomers to identify the nearby galaxy where it occurred.

By combining that information with the gravitational wave signal, researchers could make a new measurement of the Hubble constant based directly on Einstein’s theory of gravity. Problem solved? Unfortunately, no. The measurement was not as precise as those that make up the Hubble tension.

In fact, it fell right in between the competing measurements, much to everyone’s frustration.

Over the last nine years, astronomers have worked to improve the precision of the GW170817 measurement. The best results came from tracking the aftermath of the collision using a worldwide network of radio telescopes. When the two neutron stars collided and merged, they produced an ultra-fast jet of charged particles. The telescopes revealed the motion and structure of this jet’s afterglow.

This data reduced the uncertainty, but the measurements remained consistent with both sides of the Hubble tension.

What we found

In our new study, we found several ways to improve on earlier analyses, including more sophisticated models, improved statistical techniques, and a careful treatment of key sources of uncertainty.

By reanalysing the extraordinarily precise telescope observations of the merger’s aftermath in greater detail, we found that models commonly used in earlier studies struggled to match the data.

We believe this has produced the most accurate Hubble constant measurement yet from GW170817: 61–70km/s per megaparsec.

Intriguingly, our result agrees more closely with measurements from the distant universe than those based on the nearby universe – despite our method also relying on the nearby universe.

This suggests there may not be something wrong with our understanding of the universe. Instead, the tension may arise from subtle calibration issues affecting other nearby universe methods.

Our result is still four times less precise than the leading nearby-universe measurements. We will need to detect more neutron star collisions to definitively settle the Hubble tension using gravitational waves. Such events are rare, so it may be a while – but for now, our study provides an important new clue in one of astronomy’s biggest problems.

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President Donald Trump can be best politically taken down by being impeached for his offenses — even if the impeachments themselves do not result in his removal from office.

After dismissing the recent wave of criticisms of the Democratic Party for nominating democratic socialists in a series of New York congressional elections, Salon’s Heather Digby Parton wrote on Sunday that “impeachment is still a very big deal with extremely high stakes. You never know if it just might work because party loyalties have been shown to only go so far. Despite this disclaimer — and despite his historic approval ratings — Trump holds tremendous sway over his party, and it’s highly unlikely he would ever be convicted unless he is drooling and incontinent, and even then.”

Yet that would not be the point of impeaching him, Parton wrote. It would rather be to keep Trump’s various unethical actions in the public eye, no matter how desperately Republicans try to bury them.

“This week data journalist G. Elliot Morris published a Strength In Numbers/Verasight poll that points to one strategy I think is important,” Parton wrote. “When asked ‘Are there grounds to impeach Trump?’ 53% of respondents said yes. When asked to name specifics, the top responses were ‘corruption,’ ‘self-enrichment,’ ‘abuse of power’ and ‘defying the courts.’ There was more — a lot more, from the Epstein files and the Iran war to incompetence, lying and deportations. But by far, the primary grounds most people chose were corruption and abuse of power, the kinds of behaviors that impeachment was designed for. And there is simply no denying that all of it is true.”

Parton noted that America’s system of government may be breaking down, as evidenced by how three presidents were either impeached or faced certain impeachment between 1974 and the present (Richard Nixon, Bill Clinton and Donald Trump) compared to only one president being impeached between 1789 and 1974 (Andrew Johnson). Even though no president has ever been forcibly removed from office, Parton added that this “doesn’t mean the process is a useless exercise.” Indeed, the goal should not be to remove him from office, but to make it impossible for Trump supporters to distract from his alleged misconduct.

“He is the most corrupt president in history, and that fact, with all its dark details, needs to be aired for the public to see while he is in office,” Parton wrote. “After Trump leaves office, there is little chance that any successive administration would be able to charge him, even though the expansive immunity conferred upon him by the Supreme Court ostensibly only applies to official duties. We know any such charges would be litigated to death, and by the time it finally came to trial, he might very well be dead, and the case would be moot.”

Trump has already made it clear that he resents his past impeachments, even though neither of them resulted in his removal from office. Under the Constitution, a president is impeached with a simple majority of the House of Representatives but can only be removed with two-thirds of the Senate voting to do so. He was impeached twice in his first term, first for attempting to extort Ukraine for dirt on former Vice President Joe Biden and then again in 2021 for trying to overthrow the government on Jan. 6. Years later, he is pushing to get the impeachments expunged, with a White House spokesperson describing those attempts as “sham efforts” and “shameful.”

“I think it makes a lot of sense the more the evidence comes out, the more we know they really were sham impeachments,” House Speaker Mike Johnson told The Wall Street Journal about Trump’s wish to expunge the impeachments. “We were saying it at the time, now we know. And they make a very compelling case that it should be expunged from the record, because it was a hyperpartisan attack job.”

Yet the impeachment expungements, if they happened, would be meaningless.

“A repeal of the impeachment vote might be legally possible, but it wouldn’t alter the original impeachment happening in the first place,” Dr. Carla Winston, a senior lecturer on international relations at the University of Melbourne in Australia, told The i Paper regarding the expungement campaign. “The actual practical effect of an impeachment by the House is to set up a trial in the Senate … but since the trial did not end in a conviction, there really is no legal effect to void or nullify.”

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Unaffordable home prices are not the kind of thing billionaire President Donald Trump has had to worry about his whole life, but his voters are having a hard time with it in his economy. Locally elected Republicans are feeling more heat over the economic situation than Trump in his gold-plated Oval Office, however, and this is pressing Columbia, SC. Mayor Daniel Rickenmann to plead Trump for mercy.

“I think it’s terrible for the Republican Party, to be quite honest,” said Rickenmann, speaking to an MS NOW “Weekend” panel Saturday morning about the possibility of Trump vetoing a popular housing bill to force Senate Republicans to pass the SAVE Act. “… When you have Senator (Rick) Scott and Senator (Elizabeth) Warren working together, this is what this country is based on, so we’re really excited. You know, look, in 10 days this bill will be law. And I don’t think the President would be wise to even think about vetoing something like this. This is monumental. This is the beginning. First housing bill in 30-plus years.”

Trump is facing a likely disastrous midterm election threatening to remove his protective Republican buffer in the House and Senate — which is the only thing protecting him from numerous investigations into claims of fraud and various tampering. Knowing this, Trump is determined to pass the SAVE Act, an election bill that critics say will make it harder to vote.

But passing the SAVE Act means also means nuking the Senate filibuster and removing the Senate parliamentarian, which Senate GOP leaders are loathe to do. For this reason, Trump is holding all bills hostage until the Republican majority commits to passing the SAVE Act to the White House for a signature.

But Trump may have other reasons behind his indifference to the Housing Bill, said MS NOW Eugene Daniels, who played footage of Trump dismissing the need for lower housing prices.

“I made billions of dollars with housing. I know housing better than anybody. Maybe anywhere. It is all about the interest rate. Lower the interest rate. You can have all the housing you want. But you have to understand: I don’t want to … hurt people that own houses too. These people, for the first time in their lives, they have valuable houses, they become rich. I don’t want to hurt them either.”

“What’s interesting is several weeks ago, a month ago, he talked about how this is important,” responded Rickenmann. “This is the number one issue across America in every city. … If you’re a Democratic city, Republican city, whatever, there’s three and a half million units needed across this country. … We had over 1,800 [building permits issued] in our city. We’re pushing everything we can. But to say that it’s just interest rates is not true. And to say this isn’t monumental as also very disappointing, in my point of view.”

“It is very important for us to protect the integrity of elections,” Rickenmann insisted. “But at the same time, we can’t hold one bill for other. We’ve got to work on thousands of things together, and I don’t like the impression that one bill is being held up for another. That’s just not the way things need to work.”

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