Probing the mysteries of neutron stars with a surprising earthly analog

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2 years ago

July 10, 2023

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inscrutable interiors — Probing the mysteries of neutron stars with a surprising earthly analog Ultracold gases in the lab could help scientists better understand the universe.

Katie McCormick – Jul 9, 2023 11:34 am UTC Enlarge / Spectral analysis indicates that silica is present in this supernova remnant, Cassiopeia A.NASA/JPL-Caltech/ O. Krause (Steward Observatory) reader comments 28 with

Ever since neutron stars were discovered, researchers have been using their unusual properties to probe our universe. The superdense remnants of stellar explosions, neutron stars pack a mass greater than the Suns into a ball about as wide as San Francisco. A single cup of this star matter would weigh about as much as Mount Everest.

These odd celestial bodies could alert us to distant disturbances in the fabric of spacetime, teach us about the formation of elements, and unlock the secrets of how gravity and particle physics work in some of the most extreme conditions in the universe.

Theyre at the center of a lot of open questions in astronomy and astrophysics, says astrophysicist Vanessa Graber of the Institute of Space Sciences in Barcelona.

But to accurately interpret some of the neutron stars signals, researchers must first understand what goes on inside them. They have their hunches, but experimenting directly on a neutron star is out of the question. So scientists need another way to test their theories. The behavior of matter in such a superdense object is so complicated that even computer simulations arent up to the task. But researchers think they may have found a solution: an earthly analog.

Though young neutron stars can have temperatures in the millions of degrees in their interior, by one important energetic measure neutrons are considered cold. Physicists think that is a characteristic they can exploit to study the inner workings of neutron stars. Instead of looking to the sky, researchers are peering into clouds of ultracold atoms created in laboratories here on Earth. And that might help them finally answer some longstanding questions about these enigmatic objects. Advertisement Space oddities

The existence of neutron stars was first proposed in 1934, two years after the discovery of the neutron itself, when astronomers Walter Baade and Fritz Zwicky wondered if a celestial body made entirely of neutrons might remain after a supernova explosion. Though they didnt get all the details right, their general idea is now widely accepted.

Stars power themselves by fusing the nuclei of lighter atoms into those of heavier atoms. But when stars run out of those lighter atoms, nuclear fusion stops and there is no longer an outward pressure to fight against the inward force of gravity. The core collapses and the stars outer layer races inward. When this layer hits the dense core, it bounces off and explodes outward, producing a supernova. The dense core that remains afterward is a neutron star. Enlarge / The remains of a supernova witnessed in the year 1054, the Crab Nebula contains a rapidly spinning neutron star known as a pulsar.CREDIT: NASA: X-RAY: CHANDRA (CXC), OPTICAL: HUBBLE (STSCI), INFRARED: SPITZER (JPL-CALTECH)

It wasnt until the 1960s that Zwicky and Baades hypothetical neutron stars were finally detected. Radio astronomer Jocelyn Bell Burnell noticed a strange, regularly pulsed radio wave signal from space while working as a graduate student at the University of Cambridge. She was detecting something that had never been seen before: a special kind of neutron star called a pulsar, which flashes beams of radiation at regular intervals as it spins, like a lighthouse. (Her adviser, along with the director of the observatorybut not Bell Burnelllater received the Nobel Prize for the discovery.)

Since then, thousands of neutron stars have been detected. As some of the densest, highest-pressure objects in the universe, neutron stars might help us learn about what happens to matter at extremely high densities. Understanding their structure and the behavior of the neutron matter composing them is of paramount importance to physicists. Advertisement

Scientists already know that the neutrons, protons, and other subatomic particles that compose a neutron star arrange themselves differently depending on where in the star they are. In certain sections, they pack rigidly like water molecules in a block of ice. In others, they flow and swirl like a frictionless fluid. But exactly where the transition happens and how the different phases of matter behave, physicists arent sure.

A superdense star born of a nuclear fireball seems, on its face, to have very little in common with a dilute cloud of ultracold particles. But they can share at least one useful characteristic: They are both below a threshold known as the Fermi temperature that depends onand is calculated based onthe matter each system is made of. A system that is well above this temperature will largely behave according to the laws of classical physics; if it is well below, its behavior will be ruled by quantum mechanics. Certain ultracold gases and neutron star material can both be well below their Fermi temperatures and consequently can act in similar ways, says Christopher Pethick, a theoretical physicist at the Niels Bohr Institute in Copenhagen and coauthor of an early overview of neutron stars in the 1975 Annual Review of Nuclear Science.

Matter that is below its Fermi temperature can obey remarkably universal laws. This universality means that, while we dont have easy access to several-million-degree neutron star matter, we could learn about some of its behavior by experimenting with ultracold gases that can be created and manipulated in laboratory vacuum chambers on Earth, says theoretical astrophysicist James Lattimer of Stony Brook University in New York, author of a summary of the science of nuclear matter in the 2012 Annual Review of Nuclear and Particle Science.

Of particular interest to Lattimer is a theoretical state called a unitary gas. A gas is unitary when each of its particles sphere of influence becomes infinite, meaning that they would influence each other no matter how far apart they are. This is impossible to have in reality, but ultracold atom clouds can get closeand so can the matter inside of neutron stars. Its similar to a unitary gas, Lattimer says, but its not a perfect unitary gas. Page: 1 2 Next → reader comments 28 with Advertisement Channel Ars Technica ← Previous story Next story → Related Stories Today on Ars

Politics

Ukraine presses Russia for 30-day ceasefire as Starmer among leaders in Kyiv for talks

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2 hours ago

May 10, 2025

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Ukraine presses Russia for 30-day ceasefire as Starmer among leaders in Kyiv for talks

Sir Keir Starmer has joined other European leaders in Kyiv to press Russia to agree an unconditional 30-day ceasefire.

The prime minister is attending the summit alongside French President Emmanuel Macron, recently-elected German Chancellor Friedrich Merz and Polish Prime Minister Donald Tusk.

It is the first time the leaders of the four countries have travelled to Ukraine at the same time – arriving in the capital by train – with their meeting hosted by President Volodymyr Zelenskyy.

It comes after Donald Trump called for “ideally” a 30-day ceasefire between Kyiv and Moscow, and warned that if any pause in the fighting is not respected “the US and its partners will impose further sanctions”.

Security and defence analyst Michael Clarke told Sky News presenter Samantha Washington the European leaders are “rowing in behind” the US president, who referred to his “European allies” for the first time in this context in a post on his Truth Social platform.

“So this meeting is all about heaping pressure on the Russians to go along with the American proposal,” he said.

“It’s the closest the Europeans and the US have been for about three months on this issue.”

Ukraine’s foreign minister Andrii Sybiha said Ukraine and its allies are ready for a “full, unconditional ceasefire” for at least 30 days starting on Monday.

Ahead of the meeting on Saturday, Sir Keir, Mr Macron, Mr Tusk and Mr Merz released a joint statement.

European leaders show solidarity – but await Trump’s backing

Dominic Waghorn

International affairs editor

@DominicWaghorn

The hope is Russia’s unilateral ceasefire, such as it’s worth, can be extended for a month to give peace a chance.

But ahead of the meeting, Ukrainian sources told Sky News they are still waiting for President Donald Trump to put his full weight behind the idea.

The US leader has said a 30-day ceasefire would be ideal, but has shown no willingness yet for putting pressure on Russian president Vladimir Putin to agree.

The Russians say a ceasefire can only come after a peace deal can be reached.

European allies are still putting their hopes in a negotiated end to the war despite Moscow’s intransigence and President Trump’s apparent one-sided approach favouring Russia.

Ukrainians would prefer to be given enough economic and military support to secure victory.

But in over three years, despite its massive economic superiority to Russia and its access to more advanced military technology, Europe has not found the political will to give Kyiv the means to win.

Until they do, Vladimir Putin may decide it is still worth pursuing this war despite its massive cost in men and materiel on both sides.

“We reiterate our backing for President Trump’s calls for a peace deal and call on Russia to stop obstructing efforts to secure an enduring peace,” they said.

“Alongside the US, we call on Russia to agree a full and unconditional 30-day ceasefire to create the space for talks on a just and lasting peace.”

The leaders said they were “ready to support peace talks as soon as possible”.

But they warned that they would continue to “ratchet up pressure on Russia’s war machine” until Moscow agrees to a lasting ceasefire.

“We are clear the bloodshed must end, Russia must stop its illegal invasion, and Ukraine must be able to prosper as a safe, secure and sovereign nation within its internationally recognised borders for generations to come,” their statement added.

“We will continue to increase our support for Ukraine.”

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The European leaders are set to visit the Maidan, a central square in Ukraine’s capital where flags represent those who died in the war.

They are also expected to host a virtual meeting for other leaders in the “coalition of the willing” to update them on progress towards a peacekeeping force.

Military officers from around 30 countries have been involved in drawing up plans for a coalition, which would provide a peacekeeping force in the event of a ceasefire being agreed between Russia and Ukraine.

This force “would help regenerate Ukraine’s armed forces after any peace deal and strengthen confidence in any future peace”, according to Number 10.

World

Terror group supporters posted on TikTok from site targeted in Indian airstrikes

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2 hours ago

May 10, 2025

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Terror group supporters posted on TikTok from site targeted in Indian airstrikes

Social media accounts expressing support for a Pakistan-based terror group linked to al Qaeda appear to have posted recent videos from a Pakistan mosque targeted by Indian airstrikes.

Sky News has found videos posted on TikTok, YouTube and Google that appear to be filmed at the Markaz Taiba Mosque in Muridke. The captions and usernames contain expressions of support for the Lashkar-e-Taiba (LeT) and a group called ‘313’.

Sky News has found and geolocated multiple videos that appear to be filmed in the area where the captions include either or both ‘313’ and LeT.

Some of the videos show men in the streets with guns. Another post captioned a video of children doing martial arts training inside the targeted mosque, “we are little soldiers, and we fight the non-believers”.

The caption uses the hashtag #جہاد313, which translates to ‘313’ jihad.

‘313’ appears to refer to the 313 Brigade, a proscribed terror organisation in Pakistan.

In a TikTok video posted to the Google page for Markaz Taiba Mosque in Muridke, a man can be seen walking along the street with a gun.

The account that posted that video wrote in their description, “Lashkar Taiba, Mujahid Force, ‘313’ and Markaz Taiba Muridke”, self-proclaiming their support for the groups.

India’s retaliatory strikes on Pakistani-adminstered Kashmir and Pakistan on 7 May came after a deadly attack in Indian-administered Kashmir last month.

Gunmen opened fire on tourists, killing 26 people and injuring dozens in a popular holiday spot near Pahalgam, Kashmir, on 22 April.

LeT were accused by India of involvement in the Pahalgam attack through their proxy the Resistance Front, which claimed responsibility for the attack.

LeT, which is designated as a terrorist organisation by the UN Security Council and the UK, focuses on fighting Indian control in Kashmir and is based in the Punjab region of Pakistan.

Pakistan denies allegations of terror camps operating in the country. This region has been in the control of the Punjabi government since 2010. The Punjab government condemned the Indian strikes, and declared a state of emergency across Punjab.

Muskan Sangwan, senior intelligence analyst at TRAC, a terrorism research and analysis consortium, told Sky News: “Brigade 313 is al Qaeda in Pakistan. It’s an umbrella organisation for members of several groups like Taliban, Lashkar-e-Jhangvi, Haqqat ul-Jihad-al-Islami, Jaish-e Muhammad, Lashkar-e-Taiba, and Jundullah.”

Ms Sangwan explained that ‘313’ refers to the number of companions said to have fought with the Prophet Mohammed in the Battle of Badr.

TRAC have seen a recent uptick in TikTok videos and other social media posts that refer to ‘313’.

Many of the accounts are linked to each other.

Ms Sangwan said: “They [the TikTok users] mostly use ‘313’ as a hashtag… trying to push that hashtag to as many people it can reach on social media.”

Sky News sought to verify the location by comparing before and after videos from the strike location, and using the video released by the Indian army conducting the strike.

One video showing damage at the strike location was posted by a user with 313 in their TikTok username.

Below is satellite imagery that shows the destruction of the site.

In one TikTok, the video is captioned “bring your arms and ammunition and go to war”. The text on the screen of the TikTok is ‘313’ and he is carrying a gun.

The group are comfortable with having an online presence. On the Google tag for Markaz Taiba Mosque in Muridke, men pose for a group photo. Almost all the people in the photo have used ‘313’ on TikTok.

Ms Sangwan explained: “With these people from Muridke, pushing this propaganda on social media would generate a lot of significance in terms of recruitment and in terms of gaining support from local people and from other people.”

Sky News’ Asia correspondent Cordelia Lynch has reported on the ground in Muridke.

India says it struck Markaz Taiba, a site in Muridke about 15 miles (25km) from the border, which has long been claimed to be a terrorist training site associated with LeT.

MEMRI, a US-based research group that monitors terrorist threats, told Sky News: “It has been known for decades that Lashkar-e-Taiba has its headquarters in Muridke.”

Sky News contacted the Pakistan Ministry of Defence for comment. Khawaja Asif, Pakistan’s defence minister, told Sky News: “This appears to be a random video with background music added later – consistent with how TikTok trends often function. If this is to be considered credible evidence, we could produce millions of similar clips ourselves.”

Mr Asif also said that any suggestion that the mosque was used as a base by terrorists was a “completely false, social media made up hoax”.

On 7 May, after the strikes in Pakistan, the Indian subcontinent branch of al Qaeda issued a statement condemning India’s actions and encouraging its supporters to wage jihad against India.

The Data and Forensics team is a multi-skilled unit dedicated to providing transparent journalism from Sky News. We gather, analyse and visualise data to tell data-driven stories. We combine traditional reporting skills with advanced analysis of satellite images, social media and other open source information. Through multimedia storytelling we aim to better explain the world while also showing how our journalism is done.