Something strange found in our outer solar system .

There’s something going on in our outer solar system. But it couldn’t be Planet Nine. Something wonky going on somewhere in the outer reaches of the Solar System, beyond Neptune’s orbit. Some objects orbit differently from all else, and we don’t know why.

A popular hypothesis is that these orbits could be messed with an unseen object called Planet Nine. Astronomers are searching avidly for this planet. But physicists came up with an alternative explanation earlier this year that they think is more plausible.

That’s according to astrophysicists Antranik Sefilian from the University of Cambridge in the United Kingdom and Jihad Touma from the American University of Beirut in Lebanon.

If it sounds familiar, that’s because Sefilian and Touma aren’t the first to think about this idea. But their calculations are the first to explain important features of these objects strange orbits while taking into account the other eight planets in the Solar System. studying a dwarf planet in the Kuiper Belt noticed that several TNOs were “detached” from the powerful gravitational influence of the gas giants of the Solar System and had strange looping orbits different from the rest of the Kuiper Belt.

But these six objects ‘ orbits were also clustered together in a way that did not seem to be random. Something seemed to tug them into that position. A giant, previously unseen planet could do so, according to modeling.

This planet has remained elusive so far-not necessarily odd, as there are considerable technical challenges to seeing such a distant dark object, especially when we don’t know where it is. But its evasiveness leads scientists to search for alternative explanations.

“The hypothesis of the Planet Nine is fascinating, but if the hypothesized ninth planet exists, detection has so far been avoided,” Sefilian said back in January when his study was released. Adding that the team wanted to see if there was a less dramatic explanation of the strange TNO orbits.

“Instead of allowing a ninth planet and then worrying about its formation and unusual orbit, we thought why not just take into account the gravity of small objects that constitute a disc beyond Neptune’s orbit and see what it does for us?”

When researchers first detected there’s something going on in our outer Solar System they created a computer model of the detached TNOs, as well as the Solar System planets (and their gravity), and a huge debris disc past the orbit of Neptune. They were able to recreate the clustered looping orbits of the detached TNOs by applying tweaks to elements such as mass, eccentricity, and disc orientation.

“If you remove Planet Nine from the model and instead allow lots of small objects scattered across a wide area, collective attractions between those objects could account for the eccentric orbits we see in some TNOs just as easily,” Sefilian said.

This solves a problem faced by the University of Colorado Boulder scientists when they first floated last year’s collective gravity hypothesis. While their calculations could account for the gravitational effect on the detached TNOs, they were unable to explain why their orbits were all tilting the same way.

And there is yet another problem with both models. The Kuiper Belt needs a collective gravity of at least a few Earth masses in order to produce the observed effect. However, current estimates put the Kuiper Belt mass at only 4-10% of the Earth’s mass.

But, according to the Solar System formation models, it should be much higher. And, Sefilian notes, when you’re inside it, it’s hard to see the whole of a debris disc around a star, so it’s possible that the Kuiper Belt is much more than we can see.

“While we don’t have direct observational evidence for the disc and we don’t have it for Planet Nine, so we’re investigating other possibilities,” said Sefilian.

“It is also possible that both things could be true there could be a massive disk and a ninth planet. We are gathering more evidence with the discovery of each new TNO that could help explain their behaviour.”

The research of the team has been published in the Astronomical Journal and on arXiv, you can read the entire paper free.

The stars that Voyager and Pioneer probes will visit in millions of years' time

 Highlight -

• Scientists have plotted the trajectories of the Voyager and Pioneer probes as they travel beyond solar system
• The two Voyager craft both launched in the late 1970s and left the heliosphere in 2012 and 2018, respectively
• Voyager 1 is expected to reach Proxima Centauri, the closest star to the sun, in about 16,700 years, they say
• It will take much longer for Voyager 2 to get there, at an estimated 20,300 years from now, study found

It's been six months since NASA's Voyager 2 spacecraft left the protective bubble around our solar system known as the heliosphere and officially crossed into interstellar space, marking the second time ever a human-made object has traveled so far.

Voyager 2 followed in the footsteps of its predecessor, Voyager 1, and both craft will eventually be joined in the 'space between the stars' by the Pioneer 10, Pioneer 11, and New Horizons missions.

It's been six months since NASA's Voyager 2 spacecraft left the protective bubble around our solar system and officially crossed into interstellar space, marking the second time ever a human-made object has traveled so far. Their position in relation to our solar system is shown above

WHAT IS THE HELIOSPHERE? 

The sun sends out a constant flow of solar material called the solar wind, which creates a bubble around the planets called the heliosphere.

The heliosphere acts as a shield that protects the planets from interstellar radiation. 

Voyager 2 passed the outer edge of the heliosphere on Nov. 5. 

This boundary, called the heliopause, is where hot solar wind meets the cold, dense interstellar medium. 

In a new study published in the journal IOPscience, a duo from NASA and the Max Planck Institute for Astronomy in Germany attempted to plot the close approaches Voyager 1 and 2 and Pioneers 10 and 11 will eventually make in interstellar space.

For all but one, Proxima Centauri will be the first flyby – though this won't come for many thousands of years.

Voyager 1 will pass the star in about 16,700 years, though from a faraway distance of about 3.59 light-years away, followed by Pioneer 11 in 18,300 years and Voyager 2 in 20,300 years.

Pioneer 10, on the other hand, will first fly past the small star Ross 248, roughly 10.3 light-years away.

Calculating the path of these craft so far in the future is no simple task, and the team built upon methods they previously used to trace the possible origin of the mysterious interstellar object 'Oumuamua.

We answer this here using the accurate 3D positions and 3D velocities of 7.2 million stars in the second Gaia data release (GDR2, Gaia Collaboration 2018), supplemented with radial velocities for 222,000 additional stars obtained from Simbad.'

While there are some uncertainties, the researchers were able to narrow down the trajectories to make note of the stars each craft will come relatively close to, within 15 parsec (about 50 light-years).

In some cases, the scientists expect the craft to get within 1 pc of certain stars, or a distance of just over 3 light-years. All of these encounters, however, will occur far in the future.

Voyager 1 is expected to come within 0.3 pc, or less than 1 light-year, of the star TYC 3135-52-1, which sits roughly 46.9 light-years from the sun.

This flyby will occur about 302,700 years from now.

It will also make a close approach of Gaia DR2 2091429484365218432 in about 3.4 billion years, coming within about 1.27 light-years.  

The research highlights the extreme journeys these craft will make as they press on long beyond even our own lifetimes. 

'It was mostly a bit of fun,' author Coryn A. L. Bailer-Jones, of the Max Planck Institute for Astronomy told Space.com.

But it also reminds us how long it takes to get to nearby stars at the kind of speeds these spacecraft have achieved (around 15 km/s relative to the sun).'

WHAT IS INSIDE THE DISK ON THE VOYAGER PROBES?

Voyager 1 and 2 both carry a Golden Record of Earth with 115 pictures of life on our planet and messages in 59 languages that aim to serve as evidence of our civilisation.

The 12-inch gold-plated copper disk contains a variety of natural sounds, such as waves, wind, thunder, birds, whales and other animals.

It also has a message from Jimmy Carter who was the US president when the spacecraft launched.

'This is a present from a small, distant world, a token of our sounds, our science, our images, our music, our thoughts and our feelings', he said.

'We are attempting to survive our time so we may live into yours.'

It carries a photograph of page 6 of Isaac Newton's Philosophiæ Naturalis Principia Mathematica Volume 3, De mundi systemate (On the system of the world).

The record has a protective aluminium jacket as well as a catridge and a needle.

'The spacecraft will be encountered and the record played only if there are advanced space-faring civilisations in interstellar space', said Carl Sagan of Cornell University.

'But the launching of this bottle into the cosmic ocean says something very hopeful about life on this planet.'

It also contains a solar location map of Earth so future civilisations could find our planet.

This Martian Full Moon Looks Like Candy

These three views of the Martian moon Phobos were taken by NASA's 2001 Mars Odyssey orbiter using its infrared camera, THEMIS. Each color represents a different temperature range. Credit: NASA/JPL-Caltech/ASU/SSI

For the first time, NASA's Mars Odyssey orbiter has caught the Martian moon Phobos during a full moon phase. Each color in this new image represents a temperature range detected by Odyssey's infrared camera, which has been studying the Martian moon since September of 2017. Looking like a rainbow-colored jawbreaker, these latest observations could help scientists understand what materials make up Phobos, the larger of Mars' two moons.

Odyssey is NASA's longest-lived Mars mission. Its heat-vision camera, the Thermal Emission Imaging System (THEMIS), can detect changes in surface temperature as Phobos circles Mars every seven hours. Different textures and minerals determine how much heat THEMIS detects.

This movie shows three views of the Martian moon Phobos as viewed in visible light by NASA's 2001 Mars Odyssey orbiter. The apparent motion is due to movement by Odyssey's infrared camera, Thermal Emission Imaging System (THEMIS), rather than movement by the moon. Image Credit: NASA/JPL-Caltech/ASU/SSI 

"This new image is a kind of temperature bullseye - warmest in the middle and gradually cooler moving out," said Jeffrey Plaut, Odyssey project scientist at NASA's Jet Propulsion Laboratory in Pasadena, California, which leads the mission. "Each Phobos observation is done from a slightly different angle or time of day, providing a new kind of data."

On April 24, 2019, THEMIS looked at Phobos dead-on, with the Sun behind the spacecraft. This full moon view is better for studying material composition, whereas half-moon views are better for looking at surface textures.

"With the half-moon views, we could see how rough or smooth the surface is and how it's layered," said Joshua Bandfield, a THEMIS co-investigator and senior research scientist at the Space Sciences Institute in Boulder, Colorado. "Now we're gathering data on what minerals are in it, including metals."

Iron and nickel are two such metals. Depending on how abundant the metals are, and how they're mixed with other minerals, these data could help determine whether Phobos is a captured asteroid or a pile of Mars fragments, blasted into space by a giant impact long ago.

These recent observations won't definitively explain Phobos' origin, Bandfield added. But Odyssey is collecting vital data on a moon scientists still know little about - one that future missions might want to visit. Human exploration of Phobos has been discussed in the space community as a distant, future possibility, and a Japanese sample-return mission to the moon is scheduled for launch in the 2020s.

"By studying the surface features, we're learning where the rockiest spots on Phobos are and where the fine, fluffy dust is," Bandfield said. "Identifying landing hazards and understanding the space environment could help future missions to land on the surface."

Odyssey has been orbiting Mars since 2001. It takes thousands of images of the Martian surface each month, many of which help scientists select landing sites for future missions. The spacecraft also serves an important role relaying data for Mars' newest inhabitant, NASA's InSight lander. But studying Phobos is a new chapter for the orbiter.

"I think it's a great example of taking a spacecraft that's been around a very long time and finding new things you can do with it," Bandfield said. "It's great that you can still use this tool to collect groundbreaking science."

Something Strange Punched a Hole in the Milky Way.

There's a "dark impactor" blasting holes in our galaxy. We can't see it. It might not be made of normal matter. Our telescopes haven't directly detected it. But it sure seems like it's out there.

"It's a dense bullet of something," said Ana Bonaca, a researcher at the Harvard-Smithsonian Center for Astrophysics, who discovered evidence for the impactor.

Bonaca's evidence for the dark impactor, which she presented April 15 at the conference of the American Physical Society in Denver, is a series of holes in our galaxy's longest stellar stream, GD-1. Stellar streams are lines of stars moving together across galaxies, often originating in smaller blobs of stars that collided with the galaxy in question. The stars in GD-1, remnants of a "globular cluster" that plunged into the Milky Way a long time ago, are stretched out in a long line across our sky.

Under normal conditions, the stream should be more or less a single line, stretched out by our galaxy's gravity, she said in her presentation. Astronomers would expect a single gap in the stream, at the point where the original globular cluster was before its stars drifted away in two directions. But Bonaca showed that GD-1 has a second gap. And that gap has a ragged edge — a region Bonaca called GD-1's "spur" — as if something huge plunged through the stream not long ago, dragging stars in its wake with its enormous gravity. GD-1, it seems, was hit with that unseen bullet. [Gallery: Dark Matter Throughout the Universe]

This image from Bonaca's presentation shows the most detailed map yet of GD-1, revealing the apparent second gap and spur.Credit: New Astrophysical Probes of Dark Matter, Ana Bonaca/GAIA

"We can't map [the impactor] to any luminous object that we have observed," Bonaca told Live Science. "It's much more massive than a star… Something like a million times the mass of the sun. So there are just no stars of that mass. We can rule that out. And if it were a black hole, it would be a supermassive black hole of the kind we find at the center of our own galaxy."

It's not impossible that there's a second supermassive black hole in our galaxy, Bonaca said. But we'd expect to see some sign of it, like flares or radiation from its accretion disk. And most large galaxies seem to have just a single supermassive black hole at their center.

Top: This image shows what GD-1 appears to actually look like. Bottom: This image shows what computer models predict GD-1 should look like.Credit: New Astrophysical Probes of Dark Matter, Ana Bonaca/GAIA

With no giant, bright objects visible zipping away from GD-1, and no evidence for a hidden, second supermassive black hole in our galaxy, the only obvious option left is a big clump of dark matter. That doesn't mean the object is definitely, 100%, absolutely made of dark matter, Bonaca said.

"It could be that it's a luminous object that went away somewhere, and it's hiding somewhere in the galaxy," she added.

But that seems unlikely, in part due to the sheer scale of the object.

"We know that it's 10 to 20 parsecs [30 to 65 light-years] across," she said. "About the size of a globular cluster."

Top: This image again shows what GD-1 appears to actually look like. Bottom: This image shows what computer models predict GD-1 would look like after an interaction with a large, heavy object.Credit: New Astrophysical Probes of Dark Matter, Ana Bonaca/GAIA

But it's hard to entirely rule out a luminous object, in part because the researchers don't know how fast it was moving during the impact. (It may have been moving very fast, but not quite as heavy as expected — a true dark bullet — Bonaca said. Or it could have been moving more slowly but been very massive — a sort of dark hammer.) Without an answer to that question, it's impossible to be certain where the thing would have ended up.

Still, the possibility of having found a real dark matter object is tantalizing.

Right now, researchers don't know what dark matter is. Our universe seems to act like the luminous matter, the stuff we can see is just a small fraction of what's out there. Galaxies bind together as if there's something heavy inside them, clustered in their centers and creating enormous gravity. So most physicists reason that there's something else out there, something invisible. There are lots of different opinions as to what it's made of, but none of the efforts to directly detect dark matter on Earth have yet worked.

This dense ball of unseen something plunging through our Milky Way offers physicists a new scrap of evidence that dark matter might be real. And it would suggest that dark matter is really "clumpy," as most theories about its behavior predict. [Beyond Higgs: 5 Elusive Particles That May Lurk in the Universe]

If dark matter is "clumpy," then it's concentrated in irregular chunks distributed roughly across galaxies — much like the luminous matter we see concentrated in stars and nebulae. Some alternative theories, including theories that suggest dark matter doesn't exist at all, wouldn't include any clumps — and would have the effects of dark matter distributed smoothly across galaxies.

So far, Bonaca's discovery is one of a kind, so new that it hasn't yet been published in a peer-reviewed journal (though it was met appreciatively by the crowd of physicists at the prestigious conference).

To pull it off, she relied on data from the Gaia mission, an European Space Agency program to map billions of stars in our galaxy and their movements across the sky. It formed the best existing catalog of the stars that seem to be part of GD-1.

Bonaca buttressed that data with observations from the Multi Mirror Telescope in Arizona, which showed which stars were moving toward Earth, and which were moving away. That helped distinguish between stars that were really moving with GD-1, and those that just sat next to it in Earth's sky. That effort produced the most precise image ever of GD-1, which revealed the second gap, the spur, and a previously unseen region of the stellar stream.

Down the road, Bonaca said, she wants to do more mapping projects to reveal other regions of the sky where something unseen seems to be knocking stars around. The goal, she said, is to eventually map clumps of dark matter all across the Milky Way.

NASA's asteroid warning: Gigantic rogue body heading towards earth at 93,000 kilometers per hour

An asteroid named 2019 JB1 is heading towards earth at a mind-blowing speed of 93,000 kilometers per hour, NASA has confirmed. Asteroid trackers of the United States space agency revealed that this space body measuring 1,280 feet will make a close flyby in the early hours of May 20, 2019.

As per NASA, 2019 JB1 is a near-earth object (NEO). The space agency considers all asteroids and comets in orbit of the Sun at a distance of 1.3 astronomical units as near-earth objects. It should be noted that one astronomical unit is equal to about 92.95 million miles, and it is actually the distance between the earth and the sun.

On May 20, 2019, JB1 may come as close as 6.4 million km from the earth. A distance of 6.4 million kilometers may seem too huge in human terms, but considering the depth and vastness of the universe, this distance is quite small in astronomical terms.

Even though the chances of 2019 JB1 hitting the earth is very less, NASA believes that any impact from such gigantic space bodies could bring about cataclysmic effects in the affected area.

A few weeks back, NASA administrator Jim Bridenstine also revealed that the possibilities of an apocalyptic asteroid hit are not something reserved for Hollywood disaster movies. In a recent speech at the Planetary Defense Conference, Bridenstine predicted that life-threatening asteroid hits could happen in the future.

Credit. NASA

Could we get more clear image of Black Hole ?

Image of super massive black hole at the center of M87 galaxy taken by Event Horizon Telescope . Published on 10th April 2019.The Event Horizon Telescope, a planet-scale array of eight ground-based radio telescopes forged through international collaboration, captured this image of the supermassive black hole and its shadow that's in the center of the galaxy M87.

The first-ever photo of a black hole amazed people across the world. Now, astronomers are aiming to take even sharper pictures of these enigmatic structures by sending radio telescopes into space.

The historic photo became public on April 10, when the worldwide research collaboration known as Event Horizon Telescope (EHT) unveiled the hazy but nevertheless incredible photo of the supermassive black hole at the center of the galaxy Messier 87. 

Astronomers at Radboud University in the Netherlands have recently shared their plans to work with the European Space Agency (ESA) and others to get a better look at black holes by placing two to three satellites in a circular orbit around Earth. The concept is called the Event Horizon Imager (EHI).

The resolution of a radio image is limited by the size of the telescope that receives the signal, and that's why EHT used a network of dish telescopes around the world to essentially turn Earth into a planet-size virtual telescope. By expanding the distances between the radio observations, astronomers could someday present the public with a clearer, more detailed view of a black hole, researchers said in a statement from Radboud University.

In space, the EHI has a resolution more than five times that of the EHT on earth, and images can be reconstructed with higher fidelity. Top left: Model of Sagittarius A* at an observation frequency of 230 GHz. Top left: Simulation of an image of this model with the EHT. Bottom left: Model of Sagittarius A* at an observation frequency of 690 GHz. Bottom right: Simulation of an image of this model with the EHI.

"There are lots of advantages to using satellites instead of permanent radio telescopes on Earth, as with the Event Horizon Telescope (EHT)," Freek Roelofs, a researcher at Radboud University and lead author of an article describing this potential project, said in the statement.

"In space, you can make observations at higher radio frequencies, because the frequencies from Earth are filtered out by the atmosphere," Roelofs added. "The distances between the telescopes in space are also larger. This allows us to take a big step forward. We would be able to take images with a resolution more than five times what is possible with the EHT."

A crisper look would offer more than just aesthetics. According to the statement, imagery by EHI could be used to test Einstein's Theory of General Relativity in greater detail, because ''you can take near perfect images to see the real details of black holes,'' Heino Falcke, radio astronomer at Radboud University and co-author on the new work, said in the statement. ''If small deviations from Einstein's theory occur, we should be able to see them."

EHI would initially function apart from EHT, but a hybrid system to combine space observations with those taken from the ground could be a possibility.

Evidence of a neutron star smashing into a black hole

This illustration shows the merger of two black holes and the gravitational waves that ripple outward as the black holes spiral toward each other. New gravitational wave observations may point to a different sort of collision.

Detecting gravitational waves doesn’t have the sort of bombshell panache it did when it first happened three years ago, but that doesn’t make it any less remarkable. These observatories—arguably the most sensitive instruments humans have ever built—keep teaching us about events in the universe that were hidden until very recently. We’ve studied pairs of black holes merging, neutron stars colliding into one-another, and now, we may have finally witnessed signs of a black hole slamming into a neutron star. That’s something scientists were never really sure was even possible.

“It is a discovery of a novel astrophysical system whose existence was not certain,” says Katerina Chatziioannou, a member of the LIGO team at the Perimeter Institute in Waterloo, Canada, and a soon-to-be professor at Caltech. “These systems have been theorized to form in various astrophysical environments, so proving that they exist and estimating how common they are will tell us about the environments in which they are formed.

To sum up: two new sets of gravitational wave observations were detected on April 25 and April 26, by the pair of interferometers run by the Laser Interferometer Gravitational-Wave Observatory (LIGO) based in Livingston, Louisiana, and Hanford, Washington, as well as the Virgo interferometer based in Italy. While the former signals seem to originate from a pair of neutron stars (ultra-dense bodies composed of closely-packed neutrons, formed by the collapse of massive stars after a supernova) crashing into one-another, the latter seem to come from a rare black hole-neutron star merger.

These newest detections come hot off the heels of major upgrades to the LIGO and Virgo observatories. The power of their lasers have been doubled, reducing the effect of “noise” and increasing the sensitivity of the detectors by nearly 40 percent. “These detections could have been made previously, but the improved sensitivity allows us to get a more accurate picture,” says Rana Adhikari, a LIGO team member and professor of physics at Caltech. “Like having a conversation in a quiet room instead of a busy coffee shop.”

The April 25 detection of two neutron stars smashing, which scientists are calling S190425z, is thought to have happened about 500 million light-years away from Earth (two to three times farther than the first neutron star merger observed). Only the LIGO Livingston and Virgo observatories picked up the gravitational waves of this event (Hanford’s observatory was offline at the time), and the lack of a complete detection means we’re still unclear on the precise origin of the event (it took place in a rage that covers one-fourth of the sky).

Meanwhile, the April 26 neutron star-black hole crash, called S190426c, probably happened about 1.2 billion light-years away. All three observatories caught its much-weaker signal, so scientists have narrowed the location down to a 3 percent area of the sky.

How do we know this is a mash-up of a neutron star and a black hole and not just pairs of either type? According to Chatziioannou, it comes down to mass. Neutron stars typically have a lower mass than black holes, and estimates made from the gravitational wave signals that were measured fall into a middling, Goldilocks-like range that’s not too light and not too heavy.

Unfortunately, that’s about all we really do know about the origin of the April 26 signals. We need to confirm that they indeed originate from a neutron star colliding with a black hole before we can figure out what those objects looked like before, and what the resulting cosmic chimera looks like now. Chatziioannou explains that she and her team need some time to sift through the gravitational wave data as well as other measurements like gamma rays and x rays. It would also help to discover more events like this in the coming months to ensure it isn’t a false alarm. For now, the probability that this is neutron star-black hole merger is four times higher than the odds it is simply a binary neutron star.

But there is certainly no lack of ideas for how such an event occurred. One theory, says Shaon Ghosh, a postdoctoral research associate at the University of Wisconsin Milwaukee and a member of the LIGO team, is a “co-evolving system, where two massive stars spend their lifetime in a binary system, evolve and then form a neutron star and a black hole. These two compact objects emit gravitational waves, losing energy and angular momentum and shrinking the separation between them and eventually coalescing.” Another theory involves something called dynamical capture, where an unrelated neutron star and a black hole accidentally get too close, and start to gravitationally interact with each other, until they eventually merge.

Ghosh emphasizes that since black holes don’t actually have a surface, a neutron star and a black hole merger isn’t really a collision that might spew matter out in every direction, but rather a soft smash-up of the two bodies. “If the event was indeed from a coalescence of a neutron star and a black hole,” says Ghosh, “then the gravity of the black hole may sufficiently deform the neutron star,” ripping it up into bits. It could form a cosmic orbit of matter hanging around the black hole’s point-of-no-return.

If we get confirmation, however, it would be an astounding discovery. The confirmation of gravitational waves has consistently been touted as proof of a major part of Einstein’s theory of general relativity, but many have hoped our detection of these signals could help us glimpse a whole new world of astrophysics. It looks like these could be one of the first examples of that realized potential.

“Any system that involves a neutron star carries information about dense matter at extreme densities,” says Chatziioannou. “So by studying the gravitational wave data we might be able to infer something about the properties of the neutron star matter.” Ghosh adds that follow-up observations ought to help us understand the disruptive physical effects that occur under the extreme gravity exerted by black holes.

It’s going to take time for the LIGO and Virgo teams to sit down with the results and make more sense of them, but if these first round of hypotheses hold true, we’re on the cusp of a major paradigm shift in our understanding of the astrophysics of the known universe.

For a Split Second, a (Simulated) Particle Went Backward in Time

  In photography and film, a broken egg can be         perfectly unscrambled to its original state. But in   real life, quantum mechanics prevent even a     single particle from reversing its own course   through time.

This is not typically seen in regular life — with the possible exception of middle-agers who develop a sudden taste for sports cars and young trophy spouses. The question is, why not?

In what amounts to a technological triumph for the aspiring Benjamin Buttons of the virtual world, a team of quantum physicists reported earlier this year that they had succeeded in creating a computer algorithm that acts like the Fountain of Youth.

Using an IBM quantum computer, they managed to undo the aging of a single, simulated elementary particle by one millionth of a second. But it was a Pyrrhic victory at best, requiring manipulations so unlikely to occur naturally that it only reinforced the notion that we are helplessly trapped in the flow of time.

Most of us already sense that the atoms of a scrambled egg can’t be unscrambled back inside a pristine shell. Now it seems that, under general conditions, even a single particle probably can’t go backward without help and careful tinkering.

“We demonstrate that time-reversing even ONE quantum particle is an unsurmountable task for nature alone,” Valerii M. Vinokur, of Argonne National Laboratory, said in an email message; he is one of the five aspiring time lords led by Gordey B. Lesovik of the Moscow Institute of Physics and Technology.

Playing quantum billiards

On paper, the basic laws of physics are reversible; they work mathematically whether time is running forward or backward. But if time is just another dimension of space-time, as Einstein said, it’s a strange one-way dimension. In the real world we can climb out of the subway and turn left or right, but we don’t have the choice of going forward or back in time. We are always headed toward the future.

Left, IBM’s Q dilution refrigerator, which houses a quantum computer. Right, scientists Hanhee Paik and Sarah Sheldon examine hardware inside an open dilution fridge at IBM’s Thomas J. Watson Research Center in Yorktown Heights, N.Y.

CrediWe seem to be at the mercy of the second law of thermodynamics, which states that disorder and complexity only increase in a closed system such as, say, the universe. Thus, the atoms in an egg never unscramble themselves, in part because there are countless more ways for them to be thoroughly scrambled than successfully reassembled.We seem to be at the mercy of the second law of thermodynamics, which states that disorder and complexity only increase in a closed system such as, say, the universe. Thus, the atoms in an egg never unscramble themselves, in part because there are countless more ways for them to be thoroughly scrambled than successfully reassembled.

We seem to be at the mercy of the second law of thermodynamics, which states that disorder and complexity only increase in a closed system such as, say, the universe. Thus, the atoms in an egg never unscramble themselves, in part because there are countless more ways for them to be thoroughly scrambled than successfully reassembled.

But the arrow of time takes its direction not only from big numbers. According to quantum theory, that paradoxical body of rules governing the subatomic universe, not even a single particle can reverse its own course through time.

The uncertainty principle, which lies at the heart of quantum mechanics, states that, at any given moment, either the location or the velocity of a subatomic particle can be specified, but not both. As a result, a particle such as an electron, or a system of them, is represented by a mathematical entity called a wave function, whose magnitude is a measure of the probability of finding a particle in a particular place or condition.

The wave function extends throughout space and time. The law describing its evolution, known as the Schrödinger equation, after Austrian physicist Erwin Schrödinger​, is equally valid running forward or backward. But getting a wave function to go in reverse is no small trick.

Dr. Vinokur likened the challenge to sending a speeding billiard ball back to where it started. Seems easy: Just hit it with a cue stick. But if it’s a quantum ball, the uncertainty principle kicks in: You can know how hard to hit the ball, or in which direction to hit it, but not both.

“Because of the uncertainty principle, the quantum ball will never return back to the point of the origin,” Dr. Vinokur said.

Moreover, in quantum mechanics, the ball is actually a wave: Once its location is known, it spreads like ripples on a pond and evolves. Making it go backward takes more than a nudge with a cue stick. It requires reversing the phases of the waves, turning crests into troughs, and so forth, an operation too complex for nature to accomplish on its own.

Yes, no and maybe

Enter the quantum computer.

Unlike regular computers, which process a series of zeros and ones, or bits, quantum computers are made of so-called qubits, each of which can be zero and one at the same time. A quantum computer can perform thousands or millions of calculations simultaneously, so long as nobody looks to see what the answer is until the end.

Many of the largest tech companies, including Google, Microsoft and IBM, are racing to build such machines, which eventually could solve problems that regular computers can’t, such as breaking currently unbreakable cryptographic codes. Some scientists argue that nature itself is a quantum computer, and that the greatest utility of such a computer will be in simulating and exploring the paradoxes of quantum weirdness.

Dr. Lesovik and his colleagues set out to do just that. They wanted to try to make a wave function go backward, using an IBM quantum computer that is available online to the public.

A four-qubit superconducting square circuit in an IBM quantum computer.

CreditIBM Research

“It remains to be seen,” the team wrote in their paper posted online in February, “whether the irreversibility of time is a fundamental law of nature or whether, on the contrary, it might be circumvented.”

The IBM computer they used represents a baby step in the direction of what theorists call “quantum supremacy.” It had only 5 qubits (IBM devices with 16 and 20 qubits are also available), compared to Google’s top-of-the-line 72-qubit “Bristlecone” computer. To keep things even simpler, the group only used two or, sometimes, three of the qubits.

The time-reversal experiment was a four-step process. First the qubits were teed up in a simple initial state that mimicked “an artificial atom,” Dr. Vinokur said. Moreover, the qubits were entangled, by what Einstein called “spooky action at a distance” — whatever happened to one qubit affected measurements of the other one (or two, depending on how many were deployed).

Then the team tapped the qubits with a series of microwave radio pulses, which nudged the qubits from a simple state into more complexity. After a millionth of a second, the scientists then halted this phase — “the evolution program” — and treated the qubits with another microwave pulse, to reverse their phase and ready them to devolve to their youthful selves.

“In graphic language, we convert spreading rings in the pond into the rings that are ready to go back to their origin,” Dr. Vinokur said. That took another millionth of a second.

Finally, the team turned the “evolution” program back on. And the qubits went back to their original alignment — back to their own past. In effect, they got a millionth of a second younger.

The algorithm almost always worked. It succeeded in returning the qubits to their youthful states 85 percent of the time when the calculation involved two qubits, but only half the time when three qubits were used. The authors attributed the reduced reliability to imperfections in the quantum computer, and to the tendency of qubits to fall out of sync when their numbers increase.

Ultimately, it will take machines with hundreds of qubits to achieve the ambitions of quantum mathematicians. When such computers become available, the team’s time-reversal algorithm could be used to test them, Andrey V. Lebedev, a physicist at ETH Zurich in Switzerland and an author on the paper, said in a news release from the Moscow Institute of Physics and Technology.

In the meantime, anyone with a quantum computer can play Benjamin Button, using their algorithm. “Now everybody can make qubits younger,” Dr. Vinokur said.