Category: Technology

That magical night sky

Or more to the point of this article: Dark Matter.

Along with huge numbers of other people, I have long been interested in the Universe. Thus this article from The Conversation seemed a good one to share with you.

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When darkness shines: How dark stars could illuminate the early universe

NASA’s James Webb Space Telescope has spotted some potential dark star candidates. NASA, ESA, CSA, and STScI

Alexey A. Petrov, University of South Carolina

Scientists working with the James Webb Space Telescope discovered three unusual astronomical objects in early 2025, which may be examples of dark stars. The concept of dark stars has existed for some time and could alter scientists’ understanding of how ordinary stars form. However, their name is somewhat misleading.

“Dark stars” is one of those unfortunate names that, on the surface, does not accurately describe the objects it represents. Dark stars are not exactly stars, and they are certainly not dark.

Still, the name captures the essence of this phenomenon. The “dark” in the name refers not to how bright these objects are, but to the process that makes them shine — driven by a mysterious substance called dark matter. The sheer size of these objects makes it difficult to classify them as stars.

As a physicist, I’ve been fascinated by dark matter, and I’ve been trying to find a way to see its traces using particle accelerators. I’m curious whether dark stars could provide an alternative method to find dark matter.

What makes dark matter dark?

Dark matter, which makes up approximately 27% of the universe but cannot be directly observed, is a key idea behind the phenomenon of dark stars. Astrophysicists have studied this mysterious substance for nearly a century, yet we haven’t seen any direct evidence of it besides its gravitational effects. So, what makes dark matter dark?

A pie chart showing the composition of the universe. The largest proportion is 'dark energy,' at 68%, while dark matter makes up 27% and normal matter 5%. The rest is neutrinos, free hydrogen and helium and heavy elements.
Despite physicists not knowing much about it, dark matter makes up around 27% of the universe. Visual Capitalist/Science Photo Library via Getty Images

Humans primarily observe the universe by detecting electromagnetic waves emitted by or reflected off various objects. For instance, the Moon is visible to the naked eye because it reflects sunlight. Atoms on the Moon’s surface absorb photons – the particles of light – sent from the Sun, causing electrons within atoms to move and send some of that light toward us.

More advanced telescopes detect electromagnetic waves beyond the visible spectrum, such as ultraviolet, infrared or radio waves. They use the same principle: Electrically charged components of atoms react to these electromagnetic waves. But how can they detect a substance – dark matter – that not only has no electric charge but also has no electrically charged components?

Although scientists don’t know the exact nature of dark matter, many models suggest that it is made up of electrically neutral particles – those without an electric charge. This trait makes it impossible to observe dark matter in the same way that we observe ordinary matter.

Dark matter is thought to be made of particles that are their own antiparticles. Antiparticles are the “mirror” versions of particles. They have the same mass but opposite electric charge and other properties. When a particle encounters its antiparticle, the two annihilate each other in a burst of energy.

If dark matter particles are their own antiparticles, they would annihilate upon colliding with each other, potentially releasing large amounts of energy. Scientists predict that this process plays a key role in the formation of dark stars, as long as the density of dark matter particles inside these stars is sufficiently high. The dark matter density determines how often dark matter particles encounter, and annihilate, each other. If the dark matter density inside dark stars is high, they would annihilate frequently.

What makes a dark star shine?

The concept of dark stars stems from a fundamental yet unresolved question in astrophysics: How do stars form? In the widely accepted view, clouds of primordial hydrogen and helium — the chemical elements formed in the first minutes after the Big Bang, approximately 13.8 billion years ago — collapsed under gravity. They heated up and initiated nuclear fusion, which formed heavier elements from the hydrogen and helium. This process led to the formation of the first generation of stars.

Two bright clouds of gas condensing around a small central region
Stars form when clouds of dust collapse inward and condense around a small, bright, dense core. NASA, ESA, CSA, and STScI, J. DePasquale (STScI), CC BY-ND

In the standard view of star formation, dark matter is seen as a passive element that merely exerts a gravitational pull on everything around it, including primordial hydrogen and helium. But what if dark matter had a more active role in the process? That’s exactly the question a group of astrophysicists raised in 2008.

In the dense environment of the early universe, dark matter particles would collide with, and annihilate, each other, releasing energy in the process. This energy could heat the hydrogen and helium gas, preventing it from further collapse and delaying, or even preventing, the typical ignition of nuclear fusion.

The outcome would be a starlike object — but one powered by dark matter heating instead of fusion. Unlike regular stars, these dark stars might live much longer because they would continue to shine as long as they attracted dark matter. This trait would make them distinct from ordinary stars, as their cooler temperature would result in lower emissions of various particles.

Can we observe dark stars?

Several unique characteristics help astronomers identify potential dark stars. First, these objects must be very old. As the universe expands, the frequency of light coming from objects far away from Earth decreases, shifting toward the infrared end of the electromagnetic spectrum, meaning it gets “redshifted.” The oldest objects appear the most redshifted to observers.

Since dark stars form from primordial hydrogen and helium, they are expected to contain little to no heavier elements, such as oxygen. They would be very large and cooler on the surface, yet highly luminous because their size — and the surface area emitting light — compensates for their lower surface brightness.

They are also expected to be enormous, with radii of about tens of astronomical units — a cosmic distance measurement equal to the average distance between Earth and the Sun. Some supermassive dark stars are theorized to reach masses of roughly 10,000 to 10 million times that of the Sun, depending on how much dark matter and hydrogen or helium gas they can accumulate during their growth.

So, have astronomers observed dark stars? Possibly. Data from the James Webb Space Telescope has revealed some very high-redshift objects that seem brighter — and possibly more massive — than what scientists expect of typical early galaxies or stars. These results have led some researchers to propose that dark stars might explain these objects.

Artist's impression of the James Webb telescope, which has a hexagonal mirror made up of smaller hexagons, and sits on a rhombus-shaped spacecraft.
The James Webb Space Telescope, shown in this illustration, detects light coming from objects in the universe. Northrup Grumman/NASA

In particular, a recent study analyzing James Webb Space Telescope data identified three candidates consistent with supermassive dark star models. Researchers looked at how much helium these objects contained to identify them. Since it is dark matter annihilation that heats up those dark stars, rather than nuclear fusion turning helium into heavier elements, dark stars should have more helium.

The researchers highlight that one of these objects indeed exhibited a potential “smoking gun” helium absorption signature: a far higher helium abundance than one would expect in typical early galaxies.

Dark stars may explain early black holes

What happens when a dark star runs out of dark matter? It depends on the size of the dark star. For the lightest dark stars, the depletion of dark matter would mean gravity compresses the remaining hydrogen, igniting nuclear fusion. In this case, the dark star would eventually become an ordinary star, so some stars may have begun as dark stars.

Supermassive dark stars are even more intriguing. At the end of their lifespan, a dead supermassive dark star would collapse directly into a black hole. This black hole could start the formation of a supermassive black hole, like the kind astronomers observe at the centers of galaxies, including our own Milky Way.

Dark stars might also explain how supermassive black holes formed in the early universe. They could shed light on some unique black holes observed by astronomers. For example, a black hole in the galaxy UHZ-1 has a mass approaching 10 million solar masses, and is very old – it formed just 500 million years after the Big Bang. Traditional models struggle to explain how such massive black holes could form so quickly.

The idea of dark stars is not universally accepted. These dark star candidates might still turn out just to be unusual galaxies. Some astrophysicists argue that matter accretion — a process in which massive objects pull in surrounding matter — alone can produce massive stars, and that studies using observations from the James Webb telescope cannot distinguish between massive ordinary stars and less dense, cooler dark stars.

Researchers emphasize that they will need more observational data and theoretical advancements to solve this mystery.

Alexey A. Petrov, Professor of physics and astronomy, University of South Carolina

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

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Alexey Petrov says at the end of the article that more observations are required before we humans know all the answers. I have no doubt that in time we will have the answers.

Me sharing a political interview

It is not something I have done before.

This is a blog about dogs in the main and many different subjects as well. For example, I am very interested in the formation of the planet; see the post coming up soon.

However, my good buddy, Dan Gomez, a Californian, sent me a link to an interview, and I quote “After the Israel-Hamas deal was signed earlier this month, Jared Kushner and Steve Witkoff, President Trump’s envoys and the leading brokers of the agreement, sat down with Lesley Stahl to discuss their unconventional deal-driven approach.”

It is a 60 Minutes interview.

I found it most interesting and completely at odds with the majority of all types of media that think that President Trump is despicable.

My view of politicians of democracies is that 99% of them are talkers. Presumably, Trump is a doer.

I would be interested to hear what others think, especially those who were born in the U.S.A.

More Bark & Bond.

🐶❤️ Because the love of a dog changes your day.

Thank you, John.

Bark & Bond

A terrific set of videos!

John Zande sent me an email yesterday. It contained a link that when clicked on took me to a series of videos.

Here is the first one I looked at:

That link sent by John is here: https://www.youtube.com/@BarkBondOfc

Technology, and Scamming

The title says it all!

We live in a world that is rapidly becoming more and more digital. But we also live in a world where the criminals are becoming better at carrying out their crimes. So a recent article in The Conversation seemed appropriate to republish.

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Scams and frauds: Here are the tactics criminals use on you in the age of AI and cryptocurrencies

Scammers often direct victims to convert cash to untraceable cryptocurrency and send it to them. Joe Raedle/Getty Images

Rahul Telang, Carnegie Mellon University

Scams are nothing new – fraud has existed as long as human greed. What changes are the tools.

Scammers thrive on exploiting vulnerable, uninformed users, and they adapt to whatever technologies or trends dominate the moment. In 2025, that means AI, cryptocurrencies and stolen personal data are their weapons of choice.

And, as always, the duty, fear and hope of their targets provide openings. Today, duty often means following instructions from bosses or co-workers, who scammers can impersonate. Fear is that a loved one, who scammers also can impersonate, is in danger. And hope is often for an investment scheme or job opportunity to pay off.

AI-powered scams and deepfakes

Artificial intelligence is no longer niche – it’s cheap, accessible and effective. While businesses use AI for advertising and customer support, scammers exploit the same tools to mimic reality, with disturbing precision.

Deepfake scams use high-tech tools and old-fashioned emotional manipulation.

Criminals are using AI-generated audio or video to impersonate CEOs, managers or even family members in distress. Employees have been tricked into transferring money or leaking sensitive data. Over 105,000 such deepfake attacks were recorded in the U.S. in 2024, costing more than US$200 million in the first quarter of 2025 alone. Victims often cannot distinguish synthetic voices or faces from real ones.

Fraudsters are also using emotional manipulation. The scammers make phone calls or send convincing AI-written texts posing as relatives or friends in distress. Elderly victims in particular fall prey when they believe a grandchild or other family member is in urgent trouble. The Federal Trade Commission has outlined how scammers use fake emergencies to pose as relatives.

Cryptocurrency scams

Crypto remains the Wild West of finance — fast, unregulated and ripe for exploitation.

Pump-and-dump scammers artificially inflate the price of a cryptocurrency through hype on social media to lure investors with promises of huge returns – the pump – and then sell off their holdings – the dump – leaving victims with worthless tokens.

Pig butchering is a hybrid of romance scams and crypto fraud. Scammers build trust over weeks or months before persuading victims to invest in fake crypto platforms. Once the scammers have extracted enough money from the victim, they vanish.

Pig-butchering scams lure people into fake online relationships, often with devastating consequences.

Scammers also use cryptocurrencies as a means of extracting money from people in impersonation scams and other forms of fraud. For example, scammers direct victims to bitcoin ATMs to deposit large sums of cash and convert it to the untraceable cryptocurrency as payment for fictitious fines.

Phishing, smishing, tech support and jobs

Old scams don’t die; they evolve.

Phishing and smishing have been around for years. Victims are tricked into clicking links in emails or text messages, leading to malware downloads, credential theft or ransomware attacks. AI has made these lures eerily realistic, mimicking corporate tone, grammar and even video content.

Tech support scams often start with pop-ups on computer screens that warn of viruses or identity theft, urging users to call a number. Sometimes they begin with a direct cold call to the victim. Once the victim is on a call with the fake tech support, the scammers convince victims to grant remote access to their supposedly compromised computers. Once inside, scammers install malware, steal data, demand payment or all three.

Fake websites and listings are another current type of scam. Fraudulent sites impersonating universities or ticket sellers trick victims into paying for fake admissions, concerts or goods.

One example is when a website for “Southeastern Michigan University” came online and started offering details about admission. There is no such university. Eastern Michigan University filed a complaint that Southeastern Michigan University was copying its website and defrauding unsuspecting victims.

The rise of remote and gig work has opened new fraud avenues.

Victims are offered fake jobs with promises of high pay and flexible hours. In reality, scammers extract “placement fees” or harvest sensitive personal data such as Social Security numbers and bank details, which are later used for identity theft.

How you can protect yourself

Technology has changed, but the basic principles remain the same: Never click on suspicious links or download attachments from unknown senders, and enter personal information only if you are sure that the website is legitimate. Avoid using third-party apps or links. Legitimate businesses have apps or real websites of their own.

Enable two-factor authentication wherever possible. It provides security against stolen passwords. Keep software updated to patch security holes. Most software allows for automatic update or warns about applying a patch.

Remember that a legitimate business will never ask for personal information or a money transfer. Such requests are a red flag.

Relationships are a trickier matter. The state of California provides details on how people can avoid being victims of pig butchering.

Technology has supercharged age-old fraud. AI makes deception virtually indistinguishable from reality, crypto enables anonymous theft, and the remote-work era expands opportunities to trick people. The constant: Scammers prey on trust, urgency and ignorance. Awareness and skepticism remain your best defense.

Rahul Telang, Professor of Information Systems, Carnegie Mellon University

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

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That last paragraph really spells out how it is in the modern world. I repeat that last sentence: “Awareness and skepticism remain your best defense.“

Life on other planets

A fascinating article from The Conversation.

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Earth-size stars and alien oceans – an astronomer explains the case for life around white dwarfs

White dwarf stars, like this one shown shrouded by a planetary nebula, are much smaller than stars like our Sun. NASA/R. Ciardullo (PSU)/H. Bond (STScI)

Juliette Becker, University of Wisconsin-Madison

The Sun will someday die. This will happen when it runs out of hydrogen fuel in its core and can no longer produce energy through nuclear fusion as it does now. The death of the Sun is often thought of as the end of the solar system. But in reality, it may be the beginning of a new phase of life for all the objects living in the solar system.

When stars like the Sun die, they go through a phase of rapid expansion called the Red Giant phase: The radius of the star gets bigger, and its color gets redder. Once the gravity on the star’s surface is no longer strong enough for it to hold on to its outer layers, a large fraction – up to about half – of its mass escapes into space, leaving behind a remnant called a white dwarf.

I am a professor of astronomy at the University of Wisconsin-Madison. In 2020, my colleagues and I discovered the first intact planet orbiting around a white dwarf. Since then, I’ve been fascinated by the prospect of life on planets around these, tiny, dense white dwarfs.

Researchers search for signs of life in the universe by waiting until a planet passes between a star and their telescope’s line of sight. With light from the star illuminating the planet from behind, they can use some simple physics principles to determine the types of molecules present in the planet’s atmosphere.

In 2020, researchers realized they could use this technique for planets orbiting white dwarfs. If such a planet had molecules created by living organisms in its atmosphere, the James Webb Space Telescope would probably be able to spot them when the planet passed in front of its star.

In June 2025, I published a paper answering a question that first started bothering me in 2021: Could an ocean – likely needed to sustain life – even survive on a planet orbiting close to a dead star?

An illustration showing a large bright circle, with a very small white dot nearby.
Despite its relatively small size, a white dwarf – shown here as a bright dot to the right of our Sun – is quite dense. Kevin Gill/Flickr, CC BY

A universe full of white dwarfs

A white dwarf has about half the mass of the Sun, but that mass is compressed into a volume roughly the size of Earth, with its electrons pressed as close together as the laws of physics will allow. The Sun has a radius 109 times the size of Earth’s – this size difference means that an Earth-like planet orbiting a white dwarf could be about the same size as the star itself.

White dwarfs are extremely common: An estimated 10 billion of them exist in our galaxy. And since every low-mass star is destined to eventually become a white dwarf, countless more have yet to form. If it turns out that life can exist on planets orbiting white dwarfs, these stellar remnants could become promising and plentiful targets in the search for life beyond Earth.

But can life even exist on a planet orbiting a white dwarf? Astronomers have known since 2011 that the habitable zone is extremely close to the white dwarf. This zone is the location in a planetary system where liquid water could exist on a planet’s surface. It can’t be too close to the star that the water would boil, nor so far away that it would freeze.

A diagram showing a sun, with three planets at varying distances away. The closest one is labeled 'too hot' the next 'just right' and the farthest 'too cold'
Planets in the habitable zone aren’t so close that their surface water would boil, but also not so far that it would freeze. NASA

The habitable zone around a white dwarf would be 10 to 100 times closer to the white dwarf than our own habitable zone is to our Sun, since white dwarfs are so much fainter.

The challenge of tidal heating

Being so close to the surface of the white dwarf would bring new challenges to emerging life that more distant planets, like Earth, do not face. One of these is tidal heating.

Tidal forces – the differences in gravitational forces that objects in space exert on different parts of a nearby second object – deform a planet, and the friction causes the material being deformed to heat up. An example of this can be seen on Jupiter’s moon Io.

The forces of gravity exerted by Jupiter’s other moons tug on Io’s orbit, deforming its interior and heating it up, resulting in hundreds of volcanoes erupting constantly across its surface. As a result, no surface water can exist on Io because its surface is too hot.

A diagram showing Jupiter, with four Moons orbiting around it. Io is the Moon closest to Jupiter, and it has four arrows pointing to the planet and other moons, representing the forces exerted on it.
Of the four major moons of Jupiter, Io is the innermost one. Gravity from Jupiter and the other three moons pulls Io in varying directions, which heats it up. Lsuanli/Wikimedia Commons, CC BY-SA

In contrast, the adjacent moon Europa is also subject to tidal heating, but to a lesser degree, since it’s farther from Jupiter. The heat generated from tidal forces has caused Europa’s ice shell to partially melt, resulting in a subsurface ocean.

Planets in the habitable zone of a white dwarf would have orbits close enough to the star to experience tidal heating, similar to how Io and Europa are heated from their proximity to Jupiter.

This proximity itself can pose a challenge to habitability. If a system has more than one planet, tidal forces from nearby planets could cause the planet’s atmosphere to trap heat until it becomes hotter and hotter, making the planet too hot to have liquid water.

Enduring the red giant phase

Even if there is only one planet in the system, it may not retain its water.

In the process of becoming a white dwarf, a star will expand to 10 to 100 times its original radius during the red giant phase. During that time, anything within that expanded radius will be engulfed and destroyed. In our own solar system, Mercury, Venus and Earth will be destroyed when the Sun eventually becomes a red giant before transitioning into a white dwarf.

For a planet to survive this process, it would have to start out much farther from the star — perhaps at the distance of Jupiter or even beyond.

If a planet starts out that far away, it would need to migrate inward after the white dwarf has formed in order to become habitable. Computer simulations show that this kind of migration is possible, but the process could cause extreme tidal heating that may boil off surface water – similar to how tidal heating causes Io’s volcanism. If the migration generates enough heat, then the planet could lose all its surface water by the time it finally reaches a habitable orbit.

However, if the migration occurs late enough in the white dwarf’s lifetime – after it has cooled and is no longer a hot, bright, newly formed white dwarf – then surface water may not evaporate away.

Under the right conditions, planets orbiting white dwarfs could sustain liquid water and potentially support life.

Search for life on planets orbiting white dwarfs

Astronomers haven’t yet found any Earth-like, habitable exoplanets around white dwarfs. But these planets are difficult to detect.

Traditional detection methods like the transit technique are less effective because white dwarfs are much smaller than typical planet-hosting stars. In the transit technique, astronomers watch for the dips in light that occur when a planet passes in front of its host star from our line of sight. Because white dwarfs are so small, you would have to be very lucky to see a planet passing in front of one.

The transit technique for detecting exoplanets requires watching for the dip in brightness when a planet passes in front of its host star.

Nevertheless, researchers are exploring new strategies to detect and characterize these elusive worlds using advanced telescopes such as the Webb telescope.

If habitable planets are found to exist around white dwarfs, it would significantly broaden the range of environments where life might persist, demonstrating that planetary systems may remain viable hosts for life even long after the death of their host star.

Juliette Becker, Assistant Professor of Astronomy, University of Wisconsin-Madison

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

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I take my hats off to the researchers that are looking for life elsewhere.

Black holes

How black holes challenge our technological world.

I had no idea until reading this recent article that distant black holes are essential for measuring accurately where we are. Have a read.

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Scientists look to black holes to know exactly where we are in the Universe. But phones and wifi are blocking the view

ESA / Hubble / L. Calçada (ESO), CC BY

Lucia McCallum, University of Tasmania

The scientists who precisely measure the position of Earth are in a bit of trouble. Their measurements are essential for the satellites we use for navigation, communication and Earth observation every day.

But you might be surprised to learn that making these measurements – using the science of geodesy – depends on tracking the locations of black holes in distant galaxies.

The problem is, the scientists need to use specific frequency lanes on the radio spectrum highway to track those black holes.

And with the rise of wifi, mobile phones and satellite internet, travel on that highway is starting to look like a traffic jam.

Why we need black holes

Satellites and the services they provide have become essential for modern life. From precision navigation in our pockets to measuring climate change, running global supply chains and making power grids and online banking possible, our civilisation cannot function without its orbiting companions.

To use satellites, we need to know exactly where they are at any given time. Precise satellite positioning relies on the so-called “global geodesy supply chain”.

This supply chain starts by establishing a reliable reference frame as a basis for all other measurements. Because satellites are constantly moving around Earth, Earth is constantly moving around the Sun, and the Sun is constantly moving through the galaxy, this reference frame needs to be carefully calibrated via some relatively fixed external objects.

As it turns out, the best anchor points for the system are the black holes at the hearts of distant galaxies, which spew out streams of radiation as they devour stars and gas.

These black holes are the most distant and stable objects we know. Using a technique called very long baseline interferometry, we can use a network of radio telescopes to lock onto the black hole signals and disentangle Earth’s own rotation and wobble in space from the satellites’ movement.

Different lanes on the radio highway

We use radio telescopes because we want to detect the radio waves coming from the black holes. Radio waves pass cleanly through the atmosphere and we can receive them during day and night and in all weather conditions.

Radio waves are also used for communication on Earth – including things such as wifi and mobile phones. The use of different radio frequencies – different lanes on the radio highway – is closely regulated, and a few narrow lanes are reserved for radio astronomy.

However, in previous decades the radio highway had relatively little traffic. Scientists commonly strayed from the radio astronomy lanes to receive the black hole signals.

To reach the very high precision needed for modern technology, geodesy today relies on more than just the lanes exclusively reserved for astronomy.

Radio traffic on the rise

In recent years, human-made electromagnetic pollution has vastly increased. When wifi and mobile phone services emerged, scientists reacted by moving to higher frequencies.

However, they are running out of lanes. Six generations of mobile phone services (each occupying a new lane) are crowding the spectrum, not to mention internet connections directly sent by a fleet of thousands of satellites.

Today, the multitude of signals are often too strong for geodetic observatories to see through them to the very weak signals emitted by black holes. This puts many satellite services at risk.

What can be done?

To keep working into the future – to maintain the services on which we all depend – geodesy needs some more lanes on the radio highway. When the spectrum is divided up via international treaties at world radio conferences, geodesists need a seat at the table.

Other potential fixes might include radio quiet zones around our essential radio telescopes. Work is also underway with satellite providers to avoid pointing radio emissions directly at radio telescopes.

Any solution has to be global. For our geodetic measurements, we link radio telescopes together from all over the world, allowing us to mimic a telescope the size of Earth. The radio spectrum is primarily regulated by each nation individually, making this a huge challenge.

But perhaps the first step is increasing awareness. If we want satellite navigation to work, our supermarkets to be stocked and our online money transfers arriving safely, we need to make sure we have a clear view of those black holes in distant galaxies – and that means clearing up the radio highway.

Lucia McCallum, Senior Scientist in Geodesy, University of Tasmania

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

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The last paragraph of Lucia’s article is key, in my opinion. Hopefully me posting this article will assist in the task of increasing awareness,

The mystery of Dark Matter

This very interesting article is worth a read.

Patrice Ayme published a post on Wednesday, 25th June, 2025 that is deeply conected to the following post from The Conversation.

His post was called: ‘How Does The Universe Expand? The Way Cosmologists Decided That It Does, FLRW Metric! A Causal Loop Is At The Heart Of Modern ΛCDM Cosmology!’

Thus I recommend that you read that article and then the one that is republished by me, with permission, from The Conversation.

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The Vera C. Rubin Observatory will help astronomers investigate dark matter, continuing the legacy of its pioneering namesake

The Rubin Observatory is scheduled to release its first images in 2025. RubinObs/NOIRLab/SLAC/NSF/DOE/AURA/B. Quint

Samantha Thompson, Smithsonian Institution

Everything in space – from the Earth and Sun to black holes – accounts for just 15% of all matter in the universe. The rest of the cosmos seems to be made of an invisible material astronomers call dark matter.

Astronomers know dark matter exists because its gravity affects other things, such as light. But understanding what dark matter is remains an active area of research.

With the release of its first images this month, the Vera C. Rubin Observatory has begun a 10-year mission to help unravel the mystery of dark matter. The observatory will continue the legacy of its namesake, a trailblazing astronomer who advanced our understanding of the other 85% of the universe.

As a historian of astronomy, I’ve studied how Vera Rubin’s contributions have shaped astrophysics. The observatory’s name is fitting, given that its data will soon provide scientists with a way to build on her work and shed more light on dark matter.

Wide view of the universe

From its vantage point in the Chilean Andes mountains, the Rubin Observatory will document everything visible in the southern sky. Every three nights, the observatory and its 3,200 megapixel camera will make a record of the sky.

This camera, about the size of a small car, is the largest digital camera ever built. Images will capture an area of the sky roughly 45 times the size of the full Moon. With a big camera with a wide field of view, Rubin will produce about five petabytes of data every year. That’s roughly 5,000 years’ worth of MP3 songs.

After weeks, months and years of observations, astronomers will have a time-lapse record revealing anything that explodes, flashes or moves – such as supernovas, variable stars or asteroids. They’ll also have the largest survey of galaxies ever made. These galactic views are key to investigating dark matter.

Galaxies are the key

Deep field images from the Hubble Space Telescope, the James Webb Space Telescope and others have visually revealed the abundance of galaxies in the universe. These images are taken with a long exposure time to collect the most light, so that even very faint objects show up.

Researchers now know that those galaxies aren’t randomly distributed. Gravity and dark matter pull and guide them into a structure that resembles a spider’s web or a tub of bubbles. The Rubin Observatory will expand upon these previous galactic surveys, increasing the precision of the data and capturing billions more galaxies.

In addition to helping structure galaxies throughout the universe, dark matter also distorts the appearance of galaxies through an effect referred to as gravitational lensing.

Light travels through space in a straight line − unless it gets close to something massive. Gravity bends light’s path, which distorts the way we see it. This gravitational lensing effect provides clues that could help astronomers locate dark matter. The stronger the gravity, the bigger the bend in light’s path.

Many galaxies, represented as bright dots, some blurred, against a dark background.
The white galaxies seen here are bound in a cluster. The gravity from the galaxies and the dark matter bends the light from the more distant galaxies, creating contorted and magnified images of them. NASA, ESA, CSA and STScI

Discovering dark matter

For centuries, astronomers tracked and measured the motion of planets in the solar system. They found that all the planets followed the path predicted by Newton’s laws of motion, except for Uranus. Astronomers and mathematicians reasoned that if Newton’s laws are true, there must be some missing matter – another massive object – out there tugging on Uranus. From this hypothesis, they discovered Neptune, confirming Newton’s laws.

With the ability to see fainter objects in the 1930s, astronomers began tracking the motions of galaxies.

California Institute of Technology astronomer Fritz Zwicky coined the term dark matter in 1933, after observing galaxies in the Coma Cluster. He calculated the mass of the galaxies based on their speeds, which did not match their mass based on the number of stars he observed.

He suspected that the cluster could contain an invisible, missing matter that kept the galaxies from flying apart. But for several decades he lacked enough observational evidence to support his theory.

A woman adjusting a large piece of equipment.
Vera Rubin operates the Carnegie spectrograph at Kitt Peak National Observatory in Tucson. Carnegie Institution for Science, CC BY

Enter Vera Rubin

In 1965, Vera Rubin became the first women hired onto the scientific staff at the Carnegie Institution’s Department of Terrestrial Magnetism in Washington, D.C.

She worked with Kent Ford, who had built an extremely sensitive spectrograph and was looking to apply it to a scientific research project. Rubin and Ford used the spectrograph to measure how fast stars orbit around the center of their galaxies.

In the solar system, where most of the mass is within the Sun at the center, the closest planet, Mercury, moves faster than the farthest planet, Neptune.

“We had expected that as stars got farther and farther from the center of their galaxy, they would orbit slower and slower,” Rubin said in 1992.

What they found in galaxies surprised them. Stars far from the galaxy’s center were moving just as fast as stars closer in.

“And that really leads to only two possibilities,” Rubin explained. “Either Newton’s laws don’t hold, and physicists and astronomers are woefully afraid of that … (or) stars are responding to the gravitational field of matter which we don’t see.”

Data piled up as Rubin created plot after plot. Her colleagues didn’t doubt her observations, but the interpretation remained a debate. Many people were reluctant to accept that dark matter was necessary to account for the findings in Rubin’s data.

Rubin continued studying galaxies, measuring how fast stars moved within them. She wasn’t interested in investigating dark matter itself, but she carried on with documenting its effects on the motion of galaxies.

A quarter with a woman looking upwards engraved onto it.
A U.S quarter honors Vera Rubin’s contributions to our understanding of dark matter. United States Mint, CC BY

Vera Rubin’s legacy

Today, more people are aware of Rubin’s observations and contributions to our understanding of dark matter. In 2019, a congressional bill was introduced to rename the former Large Synoptic Survey Telescope to the Vera C. Rubin Observatory. In June 2025, the U.S. Mint released a quarter featuring Vera Rubin.

Rubin continued to accumulate data about the motions of galaxies throughout her career. Others picked up where she left off and have helped advance dark matter research over the past 50 years.

In the 1970s, physicist James Peebles and astronomers Jeremiah Ostriker and Amos Yahil created computer simulations of individual galaxies. They concluded, similarly to Zwicky, that there was not enough visible matter in galaxies to keep them from flying apart.

They suggested that whatever dark matter is − be it cold stars, black holes or some unknown particle − there could be as much as 10 times the amount of dark matter than ordinary matter in galaxies.

Throughout its 10-year run, the Rubin Observatory should give even more researchers the opportunity to add to our understanding of dark matter.

Samantha Thompson, Astronomy Curator, National Air and Space Museum, Smithsonian Institution

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

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It is difficult to say anything more as my comment will mean practically nothing compared to Patrice Ayme and Samantha Thompson.

I am just grateful that these fine people publish their research with permission for it to be republished elsewhere. Thank you!

The building blocks of numbers

We are talking of prime numbers.

Science and mathematics have been a long interest of mine and I regret that I did not go to university to study science. But that was a long time ago!

However, thanks to The Conversation I can write about mathematics, in this case Prime Numbers.

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Prime numbers, the building blocks of mathematics, have fascinated for centuries − now technology is revolutionizing the search for them

Prime numbers are numbers that are not products of smaller whole numbers. Jeremiah Bartz

Jeremiah Bartz, University of North Dakota

A shard of smooth bone etched with irregular marks dating back 20,000 years puzzled archaeologists until they noticed something unique – the etchings, lines like tally marks, may have represented prime numbers. Similarly, a clay tablet from 1800 B.C.E. inscribed with Babylonian numbers describes a number system built on prime numbers.

As the Ishango bone, the Plimpton 322 tablet and other artifacts throughout history display, prime numbers have fascinated and captivated people throughout history. Today, prime numbers and their properties are studied in number theory, a branch of mathematics and active area of research today.

A history of prime numbers

A long, thin shard of bone with small lines scratched into it.
Some scientists guess that the markings on the Ishango bone represent prime numbers. Joeykentin/Wikimedia Commons, CC BY-SA

Informally, a positive counting number larger than one is prime if that number of dots can be arranged only into a rectangular array with one column or one row. For example, 11 is a prime number since 11 dots form only rectangular arrays of sizes 1 by 11 and 11 by 1. Conversely, 12 is not prime since you can use 12 dots to make an array of 3 by 4 dots, with multiple rows and multiple columns. Math textbooks define a prime number as a whole number greater than one whose only positive divisors are only 1 and itself.

Math historian Peter S. Rudman suggests that Greek mathematicians were likely the first to understand the concept of prime numbers, around 500 B.C.E.

Around 300 B.C.E., the Greek mathematician and logician Euler proved that there are infinitely many prime numbers. Euler began by assuming that there is a finite number of primes. Then he came up with a prime that was not on the original list to create a contradiction. Since a fundamental principle of mathematics is being logically consistent with no contradictions, Euler then concluded that his original assumption must be false. So, there are infinitely many primes.

The argument established the existence of infinitely many primes, however it was not particularly constructive. Euler had no efficient method to list all the primes in an ascending list.

a diagram showing prime numbers as dots in rows, with composite numbers as dots arranged in rectangles of at least two rows of dots, with the same number of dots in each row.
Prime numbers, when expressed as that number of dots, can be arranged only in a single row or column, rather than a square or rectangle. David Eppstein/Wikimedia Commons

In the middle ages, Arab mathematicians advanced the Greeks’ theory of prime numbers, referred to as hasam numbers during this time. The Persian mathematician Kamal al-Din al-Farisi formulated the fundamental theorem of arithmetic, which states that any positive integer larger than one can be expressed uniquely as a product of primes.

From this view, prime numbers are the basic building blocks for constructing any positive whole number using multiplication – akin to atoms combining to make molecules in chemistry.

Prime numbers can be sorted into different types. In 1202, Leonardo Fibonacci introduced in his book “Liber Abaci: Book of Calculation” prime numbers of the form (2p – 1) where p is also prime.

Today, primes in this form are called Mersenne primes after the French monk Marin Mersenne. Many of the largest known primes follow this format.

Several early mathematicians believed that a number of the form (2p – 1) is prime whenever p is prime. But in 1536, mathematician Hudalricus Regius noticed that 11 is prime but not (211 – 1), which equals 2047. The number 2047 can be expressed as 11 times 89, disproving the conjecture.

While not always true, number theorists realized that the (2p – 1) shortcut often produces primes and gives a systematic way to search for large primes.

The search for large primes

The number (2p – 1) is much larger relative to the value of p and provides opportunities to identify large primes.

When the number (2p – 1) becomes sufficiently large, it is much harder to check whether (2p – 1) is prime – that is, if (2p – 1) dots can be arranged only into a rectangular array with one column or one row.

Fortunately, Édouard Lucas developed a prime number test in 1878, later proved by Derrick Henry Lehmer in 1930. Their work resulted in an efficient algorithm for evaluating potential Mersenne primes. Using this algorithm with hand computations on paper, Lucas showed in 1876 that the 39-digit number (2127 – 1) equals 170,141,183,460,469,231,731,687,303,715,884,105,727, and that value is prime.

Also known as M127, this number remains the largest prime verified by hand computations. It held the record for largest known prime for 75 years.

Researchers began using computers in the 1950s, and the pace of discovering new large primes increased. In 1952, Raphael M. Robinson identified five new Mersenne primes using a Standard Western Automatic Computer to carry out the Lucas-Lehmer prime number tests.

As computers improved, the list of Mersenne primes grew, especially with the Cray supercomputer’s arrival in 1964. Although there are infinitely many primes, researchers are unsure how many fit the type (2p – 1) and are Mersenne primes.

By the early 1980s, researchers had accumulated enough data to confidently believe that infinitely many Mersenne primes exist. They could even guess how often these prime numbers appear, on average. Mathematicians have not found proof so far, but new data continues to support these guesses.

George Woltman, a computer scientist, founded the Great Internet Mersenne Prime Search, or GIMPS, in 1996. Through this collaborative program, anyone can download freely available software from the GIMPS website to search for Mersenne prime numbers on their personal computers. The website contains specific instructions on how to participate.

GIMPS has now identified 18 Mersenne primes, primarily on personal computers using Intel chips. The program averages a new discovery about every one to two years.

The largest known prime

Luke Durant, a retired programmer, discovered the current record for the largest known prime, (2136,279,841 – 1), in October 2024.

Referred to as M136279841, this 41,024,320-digit number was the 52nd Mersenne prime identified and was found by running GIMPS on a publicly available cloud-based computing network.

This network used Nvidia chips and ran across 17 countries and 24 data centers. These advanced chips provide faster computing by handling thousands of calculations simultaneously. The result is shorter run times for algorithms such as prime number testing.

A small rectangle metal chip reading 'nVIDIA'
New and increasingly powerful computer chips have allowed prime-number hunters to find increasingly larger primes. Fritzchens Fritz/Flickr

The Electronic Frontier Foundation is a civil liberty group that offers cash prizes for identifying large primes. It awarded prizes in 2000 and 2009 for the first verified 1 million-digit and 10 million-digit prime numbers.

Large prime number enthusiasts’ next two challenges are to identify the first 100 million-digit and 1 billion-digit primes. EFF prizes of US$150,000 and $250,000, respectively, await the first successful individual or group.

Eight of the 10 largest known prime numbers are Mersenne primes, so GIMPS and cloud computing are poised to play a prominent role in the search for record-breaking large prime numbers.

Large prime numbers have a vital role in many encryption methods in cybersecurity, so every internet user stands to benefit from the search for large prime numbers. These searches help keep digital communications and sensitive information safe.

Jeremiah Bartz, Associate Professor of Mathematics, University of North Dakota

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

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I find it unbelievable that there are prizes for the first 100 million-digit prime number and also the first 1 billion-digit prime number. It is so far away from my understanding of these numbers that all I can say is: I find it unbelievable!

Artificial Intelligence and Mars

NASA hasn’t landed humans on Mars yet. But thanks to robotic missions, scientists now know more about the planet’s surface than they did when the movie, The Martian, was released.

Our human knowledge is constantly growing. In many, many directions. Here is a fascinating (well it is to me!) article from The Conversation.

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A decade after the release of ‘The Martian’ and a decade out from the world it envisions, a planetary scientist checks in on real-life Mars exploration

‘The Martian’ protagonist Mark Watney contemplates his ordeal. 20th Century Fox

Ari Koeppel, Dartmouth College

Andy Weir’s bestselling story “The Martian” predicts that by 2035 NASA will have landed humans on Mars three times, perfected return-to-Earth flight systems and collaborated with the China National Space Administration. We are now 10 years past the Hollywood adaptation’s 2015 release and 10 years shy of its fictional timeline. At this midpoint, Mars exploration looks a bit different than how it was portrayed in “The Martian,” with both more discoveries and more controversy.

As a planetary geologist who works with NASA missions to study Mars, I follow exploration science and policy closely. In 2010, the U.S. National Space Policy set goals for human missions to Mars in the 2030s. But in 2017, the White House Space Policy Directive 1 shifted NASA’s focus toward returning first to the Moon under what would become the Artemis program.

Although concepts for crewed missions to Mars have gained popularity, NASA’s actual plans for landing humans on Mars remain fragile. Notably, over the last 10 years, it has been robotic, rather than crewed, missions that have propelled discovery and the human imagination forward.

A diagram showing the steps from lunar missions to Mars missions. The steps in the current scope are labeled 'Human presence on Moon,' 'Practice for Mars Exploration Demo' and 'Demo exploration framework on Mars.' The partial scope step is labeled 'Human presence on Mars.'
NASA’s 2023 Moon to Mars Strategy and Objectives Development document lays out the steps the agency was shooting for at the time, to go first to the Moon, and from there to Mars. NASA

Robotic discoveries

Since 2015, satellites and rovers have reshaped scientists’ understanding of Mars. They have revealed countless insights into how its climate has changed over time.

As Earth’s neighbor, climate shifts on Mars also reflect solar system processes affecting Earth at a time when life was first taking hold. Thus, Mars has become a focal point for investigating the age old questions of “where do we come from?” and “are we alone?”

The Opportunity, Curiosity and Perseverance rovers have driven dozens of miles studying layered rock formations that serve as a record of Mars’ past. By studying sedimentary layers – rock formations stacked like layers of a cake – planetary geologists have pieced together a vivid tale of environmental change that dwarfs what Earth is currently experiencing.

Mars was once a world of erupting volcanoes, glaciers, lakes and flowing rivers – an environment not unlike early Earth. Then its core cooled, its magnetic field faltered and its atmosphere drifted away. The planet’s exposed surface has retained signs of those processes ever since in the form of landscape patterns, sequences of layered sediment and mineral mixtures.

Rock shelves layered on top of each other, shown from above.
Layered sedimentary rocks exposed within the craters of Arabia Terra, Mars, recording ancient surface processes. Photo from the Mars Reconnaissance Orbiter High Resolution Imaging Science Experiment. NASA/JPL/University of Arizona

Arabia Terra

One focus of scientific investigation over the last 10 years is particularly relevant to the setting of “The Martian” but fails to receive mention in the story. To reach his best chance of survival, protagonist Mark Watney, played by Matt Damon, must cross a vast, dusty and crater-pocked region of Mars known as Arabia Terra.

In 2022 and 2023, I, along with colleagues at Northern Arizona University and Johns Hopkins University, published detailed analyses of the layered materials there using imagery from the Mars Reconnaissance Orbiter and Mars Odyssey satellites.

By using infrared imagery and measuring the dimensions of surface features, we linked multiple layered deposits to the same episodes of formation and learned more about the widespread crumbling nature of the terrain seen there today. Because water tends to cement rock tightly together, that loose material indicates that around 3.5 billion years ago, that area had a drying climate.

To make the discussions about this area easier, we even worked with the International Astronomical Union to name a few previously unnamed craters that were mentioned in the story. For example, one that Watney would have driven right by is now named Kozova Crater, after a town in Ukraine.

More to explore

Despite rapid advances in Mars science, many unknowns remain. Scientists still aren’t sure of the precise ages, atmospheric conditions and possible signatures of life associated with each of the different rock types observed on the surface.

For instance, the Perseverance rover recently drilled into and analyzed a unique set of rocks hosting organic – that is, carbon-based – compounds. Organic compounds serve as the building blocks of life, but more detailed analysis is required to determine whether these specific rocks once hosted microbial life.

The in-development Mars Sample Return mission aims to address these basic outstanding questions by delivering the first-ever unaltered fragments of another world to Earth. The Perseverance rover is already caching rock and soil samples, including ones hosting organic compounds, in sealed tubes. A future lander will then need to pick up and launch the caches back to Earth.

Sampling Mars rocks could tell scientists more about the red planet’s past, and whether it could have hosted life.

Once home, researchers can examine these materials with instruments orders of magnitude more sensitive than anything that could be flown on a spacecraft. Scientists stand to learn far more about the habitability, geologic history and presence of any signs of life on Mars through the sample return campaign than by sending humans to the surface.

This perspective is why NASA, the European Space Agency and others have invested some US$30 billion in robotic Mars exploration since the 1960s. The payoff has been staggering: That work has triggered rapid technological advances in robotics, telecommunications and materials science. For example, Mars mission technology has led to better sutures for heart surgery and cars that can drive themselves.

It has also bolstered the status of NASA and the U.S. as bastions of modern exploration and technology; and it has inspired millions of students to take an interest in scientific fields.

The Perseverance rover and the Ingenuity helicopter on the Martian surface, with the rover's camera moving to look down at Ingenuity.
A selfie from NASA’s Perseverance Mars rover with the Ingenuity helicopter, taken with the rover’s extendable arm on April 6, 2021. NASA/JPL-Caltech/MSSS

Calling the red planet home?

Colonizing Mars has a seductive appeal. It’s hard not to cheer for the indomitable human spirit while watching Watney battle dust storms, oxygen shortages and food scarcity over 140 million miles from rescue.

Much of the momentum toward colonizing Mars is now tied to SpaceX and its CEO Elon Musk, whose stated mission to make humanity a “multi-planetary species” has become a sort of rallying cry. But while Mars colonization is romantic on paper, it is extremely difficult to actually carry out, and many critics have questioned the viability of a Mars habitation as a refuge far from Earth.

Now, with NASA potentially facing a nearly 50% reduction to its science budget, the U.S. risks dissolving its planetary science and robotic operations portfolio altogether, including sample return.

Nonetheless, President Donald Trump and Musk have pushed for human space exploration to somehow continue to progress, despite those proposed cuts – effectively sidelining the robotic, science-driven programs that have underpinned all of Mars exploration to date.

Yet, it is these programs that have yielded humanity’s richest insights into the red planet and given both scientists and storytellers like Andy Weir the foundation to imagine what it must be like to stand on Mars’ surface at all.

Ari Koeppel, Postdoctoral Scientist in Earth and Planetary Science, Dartmouth College

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

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Nothing to add from yours truly except to say that this quote is highly relevant: “Challenges are what make life interesting and overcoming them is what makes life meaningful.” – Joshua J. Marine

(And this was the result of me looking online for quotes and coming across 50 quotes from USA Today.)