New research of oldest light confirms age of the universe

Credit: © Andrea Danti / stock.adobe.com

Just how old is the universe? Astrophysicists have been debating this question for decades. In recent years, new scientific measurements have suggested the universe may be hundreds of millions of years younger than its previously estimated age of approximately 13.8 billions of years.

Now new research published in a series of papers by an international team of astrophysicists, including Neelima Sehgal, PhD, from Stony Brook University, suggest the universe is about 13.8 billion years old. By using observations from the Atacama Cosmology Telescope (ACT) in Chile, their findings match the measurements of the Planck satellite data of the same ancient light.

The ACT research team is an international collaboration of scientists from 41 institutions in seven countries. The Stony Brook team from the Department of Physics and Astronomy in the College of Arts and Sciences, led by Professor Sehgal, plays an essential role in analyzing the cosmic microwave background (CMB) -- the afterglow light from the Big Bang.

"In Stony Brook-led work we are restoring the 'baby photo' of the universe to its original condition, eliminating the wear and tear of time and space that distorted the image," explains Professor Sehgal, a co-author on the papers. "Only by seeing this sharper baby photo or image of the universe, can we more fully understand how our universe was born."

Obtaining the best image of the infant universe, explains Professor Sehgal, helps scientists better understand the origins of the universe, how we got to where we are on Earth, the galaxies, where we are going, how the universe may end, and when that ending may occur.

The ACT team estimates the age of the universe by measuring its oldest light. Other scientific groups take measurements of galaxies to make universe age estimates.

The new ACT estimate on the age of the universe matches the one provided by the standard model of the universe and measurements of the same light made by the Planck satellite. This adds a fresh twist to an ongoing debate in the astrophysics community, says Simone Aiola, first author of one of the new papers on the findings posted to arXiv.org.

"Now we've come up with an answer where Planck and ACT agree," says Aiola, a researcher at the Flatiron Institute's Center for Computational Astrophysics in New York City. "It speaks to the fact that these difficult measurements are reliable."

In 2019, a research team measuring the movements of galaxies calculated that the universe is hundreds of millions of years younger than the Planck team predicted. That discrepancy suggested that a new model for the universe might be needed and sparked concerns that one of the sets of measurements might be incorrect.

The age of the universe also reveals how fast the cosmos is expanding, a number quantified by the Hubble constant. The ACT measurements suggest a Hubble constant of 67.6 kilometers per second per megaparsec. That means an object 1 megaparsec (around 3.26 million light-years) from Earth is moving away from us at 67.6 kilometers per second due to the expansion of the universe. This result agrees almost exactly with the previous estimate of 67.4 kilometers per second per megaparsec by the Planck satellite team, but it's slower than the 74 kilometers per second per megaparsec inferred from the measurements of galaxies.

"I didn't have a particular preference for any specific value -- it was going to be interesting one way or another," says Steve Choi of Cornell University, first author of another paper posted to arXiv.org. "We find an expansion rate that is right on the estimate by the Planck satellite team. This gives us more confidence in measurements of the universe's oldest light."

As ACT continues making observations, astronomers will have an even clearer picture of the CMB and a more exact idea of how long ago the cosmos began. The ACT team will also scour those observations for signs of physics that doesn't fit the standard cosmological model. Such strange physics could resolve the disagreement between the predictions of the age and expansion rate of the universe arising from the measurements of the CMB and the motions of galaxies.

The ACT research is funded by the National Science Foundation (NSF), and the NSF also funds the work of Professor Sehgal and colleagues at Stony Brook.

Breakthrough in deciphering the birth of supermassive black holes

“On the left, a color composite image of the Hubble space telescope in the center of” Mirachs Ghost “. On the right, the new ALMA image of this same region, revealing the distribution of the cold and dense gas which swirls around this center of this object in exquisite detail. »Credit: Cardiff University

A research team led by scientists from Cardiff University says it is closer to understanding how a supermassive black hole (SMBH) was born thanks to a new technique that allowed them to zoom in on one of these. enigmatic cosmic objects with unprecedented detail.

Scientists do not know if SMBH formed in extreme conditions soon after the big bang, in a process called effondrement direct '', ou ont été cultivées beaucoup plus tard à partir de trous noirs seed ”resulting from the death of massive stars.

If the first method were true, SMBH would be born with extremely large masses – hundreds of thousands to millions of times more massive than our Sun – and would have a fixed minimum size.

If the latter were true, the SMBH would start relatively small, about 100 times the mass of our Sun, and would begin to grow over time by feeding on the stars and the gas clouds that live around them.

Astronomers have long strived to find the lowest mass SMBHs, which are the missing links needed to decipher this problem.

In a study released today, the Cardiff-led team pushed the boundaries, revealing one of the lowest mass SMBHs ever observed in the center of a nearby galaxy, weighing less than a million times the mass from our sun.

The SMBH lives in a galaxy known as “Mirach’s Ghost”, due to its proximity to a very bright star called Mirach, which gives it a ghostly shadow.

The results were obtained using a new technique with the Atacama Large Millimeter / submillimeter Array (ALMA) network, an advanced telescope located at the top of the Chajnantor plateau in the Chilean Andes which is used to study the light of some of the coldest objects in the Universe.

“The SMBH in Mirach’s Ghost appears to have mass in the range predicted by” direct collapse “models,” said Dr. Tim Davis of the School of Physics and Astronomy at Cardiff University.

“We know it is currently active and swallowing gas, so some of the more extreme” direct collapse “models that only do very massive SMBHs cannot be true.

“That alone is not enough to tell the difference between the ‘seed’ image and ‘direct collapse’ – we have to understand the statistics for that – but it is a giant step in the right direction. ”

Black holes are objects that have collapsed under the weight of gravity, leaving behind small but incredibly dense regions of space from which nothing can escape, not even light.

A SMBH is the largest type of black hole which can represent hundreds of thousands, even billions of times the mass of the Sun.

It is believed that almost all large galaxies, like our own Milky Way galaxy, contain an SMBH located at its center.

“SMBHs have also been found in very distant galaxies as they appeared a few hundred million years after the big bang,” said Dr. Marc Sarzi, a member of Dr. Davis’ team at the Armagh Observatory & Planetarium.

“This suggests that at least some SMBHs could have become very massive in a very short time, which is difficult to explain according to the models of formation and evolution of galaxies. ”

“All black holes develop when they swallow clouds of gas and disturb stars that venture too close to them, but some have a more active life than others. ”

“Searching for the smallest SMBHs in nearby galaxies could therefore help us reveal how SMBHs start,” said Dr. Sarzi.

In their study, the international team used new techniques to zoom further than ever before into the heart of a small neighboring galaxy, called NGC404, allowing them to observe the swirling clouds of gas that surrounded the SMBH in its center.

The ALMA telescope allowed the team to resolve gas clouds in the heart of the galaxy, revealing details just 1.5 light years in diameter, making it one of the gas maps to the Highest resolution ever in another galaxy.

Being able to observe this galaxy with such high resolution allowed the team to overcome a decade of conflicting results and reveal the true nature of SMBH in the center of the galaxy.

“Our study shows that with this new technique, we can really begin to explore both the properties and the origins of these mysterious objects,” continued Dr. Davis.

“If there is a minimum mass for a supermassive black hole, we have not yet found it. ”

The results of the study were published today in the Royal Astronomical Society Monthly Notices.

393,044 km / h: the Parker probe is the fastest man-made object

Nasa’s Parker Solar Probe has just broken the record for the fastest man-made object closest to the Sun that it had established.

Launched in August 2018 by NASA, the Parker Solar Probe probe is designed to study the Sun's crown by approaching at a distance of less than 7 million kilometers. Before that, the spacecraft that came closest to our star was the Helios 2 probe which had crossed the Sun at 43 million kilometers in 1976. The Parker probe instruments will help scientists understand how the crown of the Sun and the solar wind affect the Earth and the rest of the solar system.

The probe is placed in an orbit which brings it closer and closer to the Sun while reaching unprecedented speeds. During her fourth perihelion (point on the trajectory of a celestial object or vessel in heliocentric orbit which is closest to the Sun) dated January 29, she broke her own records of speed and proximity to the Sun. Here are the data communicated by NASA:

• Fastest artificial object: 393,044 km / h
• Spaceship closest to the sun: 18.6 million km

The two previous records from November 2018:

• Fastest artificial object: 247,000 km / h
• Spaceship closest to the sun: 42.7 million km

As it gets closer to the Sun, the Parker probe will continue to beat its own records until 2024, when it is expected to be approximately 6.9 million kilometers from its surface.

A first batch of data transmitted by the probe was the subject of a publication in the journal Nature last December. They partially lift the veil on the magnetic fields and the energetic particles of the Sun.

2020 promises to be an exciting year for the study of our star. On January 29, the Daniel K. Inouye solar telescope installed in Hawaii, took pictures of the surface of the Sun like never before. This telescope, which is the most powerful in the world, is not even in use yet. It should be fully operational in July and offer us a multitude of exceptional images.

Another important meeting, on February 9, the European Space Agency will launch the Solar Orbiter. This spacecraft will not get as close to the sun as the Parker spacecraft, but it will help improve our knowledge of the planet, including taking the very first images of the polar regions of the Sun.

Russian satellite appears to be tracking US spy satellite in Earth orbit

A Russian satellite uncomfortably positioned itself near an American spy satellite orbiting the Earth, which has led space trackers to speculate that the foreign vehicle was doing its own spying.

The Russian spacecraft is supposed to inspect other satellites, and experts from the space community believe it can now keep a watchful eye on the secret American vehicle. But the motivation behind this harassment in space is still unknown.

Throughout the month of January, amateur satellite trackers kept an eye on the strange behavior of this Russian probe, known as the Kosmos 2542. Launched in November of last year, Kosmos 2542 was in orbit in the same plane that a satellite operated by the National Reconnaissance Office called USA 245, which has been in space since 2013.

"Now Kosmos 2542 is close to United States 245 all the time"
The NRO is a military agency specializing in surveillance and operates a large band of classified satellites that are supposed to spy on places around the world, so it is entirely possible that USA 245 is doing something that the United States would like to keep secret. The fact that the two satellites are on the same plane is not enough to sound the alarm, since the satellites only cross about every 10 days.

"[It] is suspicious, but does not prove anything, because there are many different satellites on this plane," writes Michael Thompson, graduate teaching assistant at Purdue University specializing in satellites and introdynamics, in a e-mail to Le bord.

Kosmos 2542 attracted special attention last week when it performed a series of maneuvers, using its on-board thrusters to get closer to USA 245. Now Kosmos 2542 is close to USA 245 all the time. Thompson writes that the Russian satellite has been in constant sight of its American target for almost two weeks. The two satellites are 150 to 300 km apart at all times, making them essentially neighbors in the vast area of ​​the low Earth orbit. Kosmos 2542 is drifting slowly, but it will be in direct line of sight to USA 245 for weeks, even months, according to Thompson. (It's unless Russia decides to move it again.)

SOMETHING TO POTENTIALLY WATCH: COSMOS 2542, A RUSSIAN INSPECTION SATELLITE, RECENTLY SYNCHRONIZED ITS ORBIT WITH USA 245, A NRO KH11.
ONE WIRE: PIC.TWITTER.COM/LQVYIIYBMD

- MICHAEL THOMPSON (@M_R_THOMP) JANUARY 30, 2020

Thompson revealed all of this information in a Twitter feed, suggesting that Kosmos 2542 is carrying out an inspection of one of the American assets. And this is not a completely unexpected conclusion to draw. Before Russia launched the satellite, the Russian Defense Ministry claimed that the spacecraft was indeed designed to inspect other satellites in space, according to the Russian Space Web site, which tracks the Russian space industry. . Most assumed that it would inspect other Russian spacecraft, unclassified spy satellites operated by the United States.

Of course, we ultimately don't know the real reason why Kosmos 2542 did these maneuvers. But most experts say there is really only one good explanation: one satellite tracks the other.

"The conclusion that he is monitoring the NRO satellite is speculation, but it is informed by orbital data," wrote Brian Weeden, director of program planning for the Secure World Foundation, in an email to Edge. "Right now, this is the most likely explanation we have for why the Russian satellite maneuvered as it did and why it is in this orbit."

What happens next is not clear. Chances are good, no danger will come to the American satellite, as Russia says its probe is only for inspection. However, concerns have been expressed that the satellites could be mutually in space if they got close enough. The Ministry of Defense has sounded the alarm about satellites hitting other satellites, spraying them with chemicals or firing them with lasers to destroy them. This kind of space war hasn't happened yet, but it is certainly on the radar of the United States government.

In addition, there is no defined protocol on what to do when the satellite of another country becomes too user-friendly. "One of the big concerns is that we don't have agreed rules or standards on how these close-in approaches should be done," says Weeden. "It means an increased risk that someone may have a bad perception of what is going on, perhaps even confuse it with an attack."

It's not like this kind of behavior is completely new. Weeden noted that Russia and China have carried out extensive inspections of their own satellites in the past. And in 2015, a Russian satellite called Luch stood next to two American communications satellites operated by Intelsat, and stayed there for five months before moving. On the other hand, the United States is also guilty of this practice, says Weeden. The U.S. military operates a series of satellites as part of its geosynchronous spatial awareness program (GSSAP), which are responsible for approaching and verifying satellites operated by other countries.

For now, Thompson says he will continue to monitor the whereabouts of Kosmos 2542. Details of the satellite's route are available at space-track.org, a website that publishes tracking data collected by the US Air Force on as many satellites and pieces of debris in orbit as possible. He notes that he is certainly not the only one watching either. "Since the orbits of these Russian satellites are public information, anyone who wants to can watch it, and I know many people in our community are," says Thompson.

NASA telescope captured the most detailed images of the Sun ever taken

The Sun is a hostile place, where boiling plasma accompanies unpredictable eruptions. Today, the highest resolution photos and videos ever taken from its surface show this action in unprecedented detail. The National Science Foundation (NSF) in the United States published, Wednesday, January 29, data and images of the first observations of its Inouye solar telescope in Hawaii. The images reveal a pattern of coiled plasma that covers the surface of the Sun. Each cell structure is the size of Texas.

Following the completion of its construction on June 30, this new telescope will help usher in a new era in solar science. This in particular thanks to the help of the NASA Parker solar probe, which revolves around the Sun, and the next solar orbiter, which will be launched next week. This trio of telescopes could help scientists predict dangerous solar flares. They can also provide other photos and videos like the ones below. Here are the new images, and what to expect next.

The first photos of the Inouye solar telescope reveal a pattern of coiled plasma that covers the surface of the Sun. Each cell structure has a size comparable to that of Texas.

L'image couvre une zone de 36 370 kilomètres de large à la surface du Soleil. NSO/NSF/AURA

The smallest elements in this image - the tiny white dots between the plasma cells - are the same size as Manhattan.

"From the first test, we were able to get the highest resolution images of the solar surface ever taken," said Thomas Rimmele, director of the telescope, at a press briefing.

he NSF's 4-meter Inouye Solar Telescope sits atop the Haleakalā volcano on the island of Maui, Hawaii, above the clouds. NSO / NSF / AURA

"The first light was a very tense but also exciting moment. The atmosphere in the telescope's control room was similar to that of a rocket launch. When the first images appeared on the screen, they exceeded my expectations, "added the researcher. The 4-meter telescope is located at the top of the Haleakala volcano on the island of Maui (Hawaii), at an altitude of 3,000 meters.

The resolution of Inouye images is five times that of previous solar telescopes.

"So far, we have probably only seen the tip of the iceberg. We have not been able to see the smallest magnetic elements that should exist on the entire surface of the Sun," said Thomas Rimmele .

SpaceX Starlink launch & Falcon 9 first stage landing, 29 January 2020

WASHINGTON - SpaceX completed its second Starlink launch in January 29, according to a target rate that the company set last year to launch two dedicated Starlink missions each month throughout 2020.

SpaceX has said it will test its satellites around this low altitude, where it expects any failure to consume in the Earth's atmosphere after a few months. After completing the checks, SpaceX plans to raise the satellites to an operational orbit of 550 kilometers.

The launch - SpaceX's fourth for Starlink without counting two demonstration satellites launched in 2018 - included an improved set of satellites designed for better spectral efficiency and better throughput. Bad weather delayed the mission by about a week.

The Falcon 9's first stage booster landed on the drone ship "Of Course I Still Love You" in the Atlantic Ocean, completing its third space voyage. SpaceX previously used the booster to launch the company's Crew Dragon capsule during a March 2019 demonstration mission for NASA and to launch three Canadian radar satellites last June.

SpaceX managed to catch half a payload fairing with "Mrs. Tree", a boat equipped with a large net. Jessica Anderson, a SpaceX manufacturing engineer who co-narrated the launch, said the second half of the fairing had missed her recovery boat. Chef, "but seemed to have a freshwater landing.

"We will remove this fairing halfway out of the water and hopefully reuse it in the future," she said.

Changes to Starlink

SpaceX has now launched 242 Starlink broadband satellites, although not all of the satellites were part of the constellation when it entered service, a milestone scheduled for later this year in Canada and the United States.

A dozen Starlink satellites have not raised their orbit, according to observations by Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics, who tracks the movements of the satellites.

SpaceX spokesperson James Gleeson, when asked about the 10 satellites, said that SpaceX "was carrying out controlled desorbitation of several first iteration Starlink satellites", using on-board propulsion.

“Although these satellites are operational and capable of providing service, the second iteration of the Starlink satellites that SpaceX has started to deploy offers better spectrum efficiency, more capacity and optimized service to the end user,” said -he declares.

SpaceX's Starlink satellites launched on January 29 each weigh around 260 kilograms, an increase of 33 kilograms compared to the 60 satellites launched in May 2019.

SpaceX said the most recent Starlink satellites have four phased array antennas. Previous satellites have been described as having "multiple" phased array antennas.

SpaceX has changed the design of Starlink since the start of the program. The first 60 satellites have been described as being 95% demolished during reentry, which means that some components were at risk of reaching the surface of the Earth. During the second dedicated launch in November, the Starlink design included completely removable parts.

SpaceX is also experimenting with ways to reduce the impact of Starlink on astronomy. Earlier this month, the company launched a satellite dubbed "DarkSat" with a darkening coating to make it less visible to astronomers and ground observatories.

SpaceX CEO Elon Musk said in May 2019 that future versions of Starlink will include inter-satellite links. He then said that the company wanted to keep the Starlink satellites in orbit for four to five years before desorbing them and replacing them with newer and better models.

How can gravitational waves help us to understand the universe ?

The discovery of gravitational waves opens a new era for astronomy and our understanding of the universe. But how ?.

In the beginning, there was light: the sky that we observe with the naked eye or with the first glasses, the astronomy of the visible. The discovery of electromagnetic waves at the end of the 19th century opened the door to a whole range of new techniques for exploring space: infrared, ultraviolet, X-rays, gamma rays, radio waves, microwaves ... the night sky became much less dark, and there were many discoveries.

These slices of universe that we don't see

But electromagnetic waves have a practical limitation: they can be deflected, distorted, and even hidden. We only see a small part of the universe, despite the wide palette offered by the different wave ranges.

Take an example: the Milky Way. When we look at the sky (outside the cities), we can clearly see this white trail, which corresponds to the "slice" of our spiral galaxy. It is also an obstacle to observation: if we can go looking for distant objects in other directions, the brightness and the number of stars, dust or other objects present in the galaxy hide us whole slices of universe, hidden behind them.

Thus, last week, astronomers announced the discovery of several hundred galaxies hitherto unknown. They were simply hidden behind the Milky Way. Who knows how many other objects are hidden from our view?

Gravitation can also be a problem for observation, under certain circumstances. The masses, especially those of stars and galaxies, deflect light rays of all kinds. As a result, some will not reach us, or will come to us distorted. Again, a brake on observation.

Light up the dark side

Gravitational waves, on the other hand, do not have this kind of problem. They are waves in space-time itself: the different objects and forces that are there will not stop them, deflect them, distort them.

The waves captured on September 14, 2015 by the LIGO observatories traveled 1.3 billion light years to give us an image of a fusion of black holes that we would not have been able to obtain otherwise.

What new information could gravitational waves give us? Here is a non-exhaustive list:

-Black holes. Obviously, gravitational waves transmit information to us about them, and that should improve our knowledge of these objects. Not only stellar black holes, resulting from the "death" of a star, but also supermassive black holes located in the center of many galaxies.

- Major catastrophic events: collisions of stars and in general, everything concerning very massive objects, in particular neutron stars, or even explosions of supernovae.


- The beginnings of the universe. The subject is vast: light could not circulate freely in the universe until 380,000 years after the Big Bang. Before that, the universe is opaque to us. Gravitational waves could change that, and help confirm (or deny) certain theories.

For example, the Bicep experiment, which in 2014 believed to detect the imprint of gravitational waves in the fossil radiation of the beginnings of the universe, also hoped to demonstrate the existence of a phase of very rapid expansion that we called "cosmic inflation". In general, the gravitational waves could bring us elements on what could have happened in the first moments of the Big Bang.

- Check certain theories. Or not. Relativity, of course, the Big Bang, but also "string theory". The latter, which aims in particular to unify relativity and quantum mechanics, is for the moment only a sum of mathematical equations. One can imagine that in the future astrophysicists could demonstrate the existence of processes described by this theory, by observing "cracks in the fabric of space-time" which would emit gravitational waves.

A new technological era?

The parallel between electromagnetic waves and gravitational waves can naturally lead us to another question: since we have developed a whole technology around the former, does this mean that the latter will also bring about a technological revolution? After all, those who first discovered the properties of electromagnetic waves did not necessarily imagine medical radiology, microwave ovens or reality TV shows.

If we see here and there flourish some unorthodox studies on the use of gravitational waves for secret communications, armament, nuclear fusion or propulsion systems, skepticism is rather the norm in this area among scientists . To use gravitational waves, you would have to move really very massive objects. The waves so small that were detected by Ligo required the fusion of two large black holes between them like more than 60 suns! While Stephen Hawking recently said that putting a black hole in the mass of a mountain into orbit could provide all the energy the Earth needs, we're not there yet 

But just because the direct technological use of gravitational waves is akin to science fiction doesn't mean they won't bring us anything. Understanding the physical processes at work in the universe alone is a potential mine of practical applications. The many discoveries that will be made in the future thanks to an "astronomy of gravitational waves" most certainly conceal unknown treasures which will advance not only science, but consequently technology.

There is also another direct contribution of gravitational waves to technology: the innovations developed to detect them. The Ligo observatories had to equip themselves with systems to isolate their instruments from seismic vibrations, for example. Like all technological progress, they will probably spread and find other uses. Again, the "window" is wide open.

China launches satellite that can photograph every metre of ground

TAIYUAN, Jan. 15 (Xinhua) - China on Wednesday placed a new optical remote sensing satellite for commercial use in its planned orbit from the Taiyuan Satellite Launch Center in northern China's Shanxi Province.

The satellite, belonging to the Jilin-1 family of satellites and also bearing the name Red Flag-1 H9, was launched by a Long March-2D carrier rocket at 10.53 am (Beijing time).

The new satellite, developed by Chang Guang Satellite Technology Co., Ltd., has super wide coverage and a resolution of less than one meter. It is also capable of storing and transmitting data at high speed.

It will work with 15 other Jilin-1 satellites already in orbit to form a constellation offering remote sensing data and services to government and industrial users.

Thanks to the same carrier rocket, three small satellites, including NewSat7 and NewSat8, developed by an Argentine company, have also been launched into space.

The Long March-2D carrier rocket was developed by the Shanghai Academy of Space Flight Technology under the China Aerospace Science and Technology Corporation.

The launch on Wednesday represented the 325th mission of the Longue Marche family's rockets.

Stephen Hawking : humanity must prepare to become interstellar

Faced with the great crises awaiting humanity, Stephen Hawking reiterated during an intervention in Beijing the urgency of preparing for the interstellar journey. According to him, we have half a millennium: “by 2600, the Earth will turn into a big ball of fire. 

Last Year during a video presentation at the Tencent Web Summit in Beijing, the famous physicist Stephen Hawking said again how much time he thinks it is time for humanity to find a second home.

The researcher alludes of course to the great ecological, biological, climatic, energy, demographic and consequently economic crises which are underway or which are looming on our horizon (2100). The vital prognosis of the Earth - at least, of the biosphere - is under way.

"By 2600, the Earth will turn into a big ball of fire," he warns. Humanity must make plans to leave the planet, otherwise we risk extermination. So if we still want to live "another million years," we must "boldly go where no one has gone before," reports The Sun.

Illustration of the nanoprobe project to explore Proxima b. © Breakthrough Starshot

Breakthrough Starshot, a first step towards interstellar exploration

A few months ago, Stephen Hawking had already said his conviction that the future of humanity is elsewhere, in space, in search of other lands: "We lack space and the only places to go are the other worlds. It's time to explore other solar systems. Lying down may be the only thing that saves us from ourselves. ”

Finally, Stephen Hawking invited the investors present at the meeting to take part in Breakthrough Initiatives which he supports. Seeking life elsewhere and ways to communicate with other extraterrestrial civilizations are the motivations of this program. And there is also Breakthrough Starshot, a project that plans to send nanosensors pushed by lasers to the star closest to us, Proxima Centauri. It is of course, for him, a way to prepare our future.

Also present in Beijing, Pete Worden, former director of NASA's Ames research center and now director of Breakthrough Starshot, said, "Hopefully soon after the middle of the century we will have our first image from another planet that could support life in orbit around the nearest star. "

Except for a collapse of our civilization, the Alpha system of the Centaur seems within our reach.

Humanity will have to leave the Solar System if it is to survive

Article by Jean Étienne published on December 14, 2006

The hypothesis of a major catastrophe destroying humanity is not new. However, the more we study the protohistory of our planet or even of our Solar System, the more this possibility seems to move away from simple conjecture to become plausible, even probable in the more or less distant future.

It is on this observation that Professor Stephen Hawking, one of the most brilliant physicists of our time, has based himself to estimate that if humanity wants to survive, it will one day have to think of emigrating on at least another planet compatible with life.

"The survival of the human race will be threatened as long as it remains concentrated in its entirety on a single planet. Disasters like a collision with an asteroid are perfectly capable of destroying us all without leaving a single survivor. When we have been able to create Autonomous colonies in deep space, our future will be assured. But conditions similar to those we know on Earth existing nowhere in our Solar System, we will necessarily have to join an extrasolar planet, "he recently stated in substance in the columns of the Daily Telegraph.

Perfectly aware that the current chemical propulsion systems of spacecraft would not allow to undertake such a journey except by agreeing to devote a few tens of millennia to it, Stephen Hawking proposes to develop the idea of ​​the deformation of space which would allow , in theory at least, to move instantly to the destination regardless of the distance. This theory, the study of which is barely in its infancy, postulates that an object could cross enormous distances by taking a shortcut between two points of a curved space folded in on itself, or by passing by a "wormhole", a sort of spatio-temporal vortex whose concept remains currently confined to science fiction ... But have we never found that if we let time run out, reality ends well often go beyond the most unbridled science fiction concepts?

Stephen Hawking with the device allowing him to communicate thanks to a computer. © DAMTP, University of Cambridge

Unfortunately, our means of travel are likely to remain subject for a long time to the limit of the speed of light, approximately 300,000 km / second, which places us the closest star to 4 years of travel excluding the acceleration phases. and slowdown on arrival. It is still necessary to reach this speed.

"We can approach the speed of light using the energy produced by the annihilation of matter and antimatter," adds Professor Hawking. "Thus, it will be possible to win the nearest star in about six years, but for the crew subjected to the effects of the theory of relativity, this period will appear much shorter".

A long-standing quadriplegic, speaking with a specially-built speech synthesizer, Stephen Hawking is the Lucasian professor of mathematics at Cambridge University, the same man who had been employed three years ago. centuries by Sir Isaac Newton. Specializing in Cosmology, Relativity and Quantum Gravitation, he is often considered one of the greatest minds of our time, sometimes even the greatest, all ages combined.

Artificial intelligence lights up black hole fusion

A simulation using an artificial intelligence algorithm succeeds in predicting the characteristics of the fusion of two black holes.

Nearly five years after the discovery of the first gravitational wave in September 2015, a team from the Center for Theoretical Astrophysics of the California Institute of Technology (CalTech, United States) has just published an article which reveals its details , collisions of black holes. Published in Physical Review Letters of January 11, this work presents the most precise simulation to date to describe the fusion of these compact stars.

Machine learning
Thus these researchers laid bare the most cataclysmic event that can occur in the Cosmos: the fusion of two black holes, two extremely compact stars, at the origin of the emission of a gravitational wave. Theoretically predicted by Einstein in 1916, it took physicists a century to invent complex and extremely sensitive detectors such as interferometers capable of detecting the tiny vibrations of space-time that are gravitational waves. For this new study, the researchers used an artificial intelligence algorithm based on machine learning. The learning was done from 900 fusion simulations of two black holes from the Simulating eXtreme Spacetimes (SXS) program calculated on the Wheeler supercomputer from Caltech.

The hunt for new physics

The team manages to predict not only the characteristics of the final black hole, such as its mass and speed of rotation, but also the shape of the gravitational wave that this collision should produce. The use of AI is justified because during the last seconds before the fusion, when the two black holes describe spirals more and more close together, the exact calculation of the shape of the emitted wave is difficult to perform with the traditional methods. The precision of their simulation will be a precious tool for the future generation of detectors: these will be able to surprise small variations in the shape of the wave and possibly track down the tiny effects of new physics.

Does the merge of black holes lead to a loss of information?

In 1976, following his work on black holes, Stephen Hawking raises a paradox: according to general relativity, the information absorbed by a black hole is lost when it evaporates. However, the laws of quantum mechanics impose a conservation of information. In the same way, when two black holes merge, they lose part of their total mass. Does this phenomenon also lead to a loss of information?

During the ten black hole mergers detected by the LIGO and Virgo interferometers in the last two years, each of the black holes involved lost a fraction of total mass during the process, around 5% on average. If the information is encoded in the mass of black holes, then it should be lost.

In any case, this is what general relativity says. When a particle falls into a black hole, all its properties - baryonic number, leptonic number, isospin, etc. - no longer play any role in the physics of the black hole. Information related to these properties is believed to be lost. In other words, according to Einstein's theory, the entropy of a black hole is zero.

Black hole and entropy: information stored on the event horizon

However, this consideration contrasts with the laws of thermodynamics and quantum mechanics. Any object with a defined temperature, energy and physical properties has a non-zero entropy, which can never decrease. If the material from which the black hole originates has a non-zero entropy, then throwing material into it would only increase its entropy. The black hole must therefore have a finite, positive and non-zero entropy.

According to these rules, all the properties of a particle (spin, charge, mass, polarization, etc.) falling into a black hole constitute information which must therefore be stored somewhere. If it’s not the singularity, then it’s in another place. And it was physicist John Wheeler who was the first to suggest that this information could be stored on the event horizon.

According to the formula of the Schwarzschild radius Rs = 2GM / c², it is the mass of a black hole which determines the size of its event horizon. It is therefore natural to think that the entropy can actually be located on the surface of this horizon.

As the mass of a black hole increases, its event horizon expands, storing the entropy / additional information absorbed. According to the work of Jakob Bekenstein and Stephen Hawking, this information would be encoded as qubits in Planck areas.

The fate of information when two black holes merge

During the fusion of two black holes, the mass of the resulting black hole is equivalent to the sum of the mass of the two black holes, reduced by 10% (5% of mass lost for each of the objects). Thus, if each black hole has a mass of 1 M, the final black hole will have a mass of 1.9 M. This means that, simultaneously, gravitational waves are emitted and transport an energy of 0.1 Mc².

From this observation, three scenarios are possible:

1. the information of the two initial black holes remains entirely encoded on the event horizon of the final black hole, the gravitational waves do not therefore carry it
2. the majority of the information is found encoded in the gravitational waves, the final black hole keeping only a very small amount
3. information is shared more or less equally between gravitational waves and the final black hole

The entropy of a black hole is proportional to the area of ​​its event horizon, the latter itself being proportional to mass squared. This means that if two initial black holes have an entropy of S, then a final black hole of 1.9 times the mass of the two black holes has an entropy of 3.6 S, which is clearly enough to store the information of the initial black holes. This is the premise of the Bekenstein-Hawking entropy.

However, gravitational waves must carry some of this information. Indeed, they are generated by the changes imprinted in the geometry of space-time during fusion, and their energy comes from the change of distribution of matter-energy of space-time. However, without the theory of effective quantum gravity, it is impossible to determine how much information is retained by the final black hole and how much is transferred to gravitational waves.

In any case, when two black holes are merged, there is no loss of information, since the entropy of the final state is higher than that of the initial state. But there is currently no way to extract the amount of entropy or information from gravitational waves or the event horizon of a black hole. Only theory here is capable of providing a few pieces of information.