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.

Major discovery on the Big Bang

Scientists who were looking for means of propulsion for rockets and planes have discovered how supernovas explode, relays "L'Express".

Funded by the United States military, scientists found, somewhat by accident, the beginnings of an explanation. By looking for new means of propulsion for planes and rockets, their experiences led them on the route of type Ia supernovae (SNIa) and especially on the way they explode. To be more precise, the supernova designate all the phenomena which lead to the explosion of a star. At L'Express, Kareem Ahmed, assistant professor in the mechanical and aerospace engineering department at the University of Florida, shares his enthusiasm. Their discovery "may even be the missing piece in the puzzle of astrophysical theories," he explains.

From a simple flame to an explosion

Supernovae are decisive in the evolution of the Universe. The thermonuclear explosions of these dead stars would also be comparable to that of the Big Bang. "They also led to discover that the Universe is in accelerated expansion, or the existence of dark energy", details Kareem Ahmed. Scientists have come across one of the possible mechanisms that lead to their explosion by recreating implosions.

Using sophisticated equipment loaned by the US military, such as a "turbulent shock tube" and supercomputers, they determined the conditions under which a single flame causes a large-scale hypersonic reaction. "We have discovered the essential criterion allowing a flame to generate its own turbulences and to accelerate them spontaneously until producing a detonation," explains the researcher at L'Express. By infusing enough turbulence into the flame space, the flame completely burned the energy around it. The hypersonic explosion is five times faster than the speed of sound, at 6,174 km / h, the newspaper said. A mechanism similar to that which produces type Ia supernovae.

A neutron star sought for 30 years finally discovered

Cardiff University scientists would have found this star hidden for several years behind a cloud of dust, reveals "The Independent"

For thirty years, scientists around the world have relentlessly tracked her down. A neutron star is said to have been found by researchers at Cardiff University, says The Independent. A neutron star forms when a giant star dies and its heart collapses.

Entitled 1987A, the supernova, which gave birth to the coveted neutron star, was first seen on February 23, 1987. Visible from Earth, the star shone for many months with comparable light intensity to 100 million suns.

During this period, scientists were able to study it, examine it and follow the life and death course of an "extreme" star. 1987A belongs to the Large Magellanic Cloud galaxy, which is 160,000 light years from the blue planet, a distance which is ultimately quite close to the scale of the Universe. But when he died, the neutron star vanished.

Cloud of dust

Astronomers are looking for that special star that the giant star left behind after its death. For thirty years, it would have been hidden by a huge cloud of cosmic dust. But scientists now claim they have finally been able to locate it. One of the bright parts of the cloud would have put the chip in the ear of astronomers. The area in question appears to be the place where the neutron star took refuge.

This discovery could help learn more about how giant stars evolve during their life, but also how they die and what happens next. "Our discoveries will allow astronomers to better understand the giant stars and their life cycle, but also what they leave behind," said Dr. Mikako Matsuura, member of the study committee. According to him, "if the cloud of dust gradually dissipates, astronomers will have the opportunity to observe a neutron star for the first time".

A new class of black holes discovered

Thanks to an innovative method, researchers may have detected a "low mass" black hole

Some 104 years after Albert Einstein's theory of general relativity, a team of researchers may have made a major discovery about the existence of black holes. In developing a "new way" to detect them, the team of experts "potentially identified one of the first examples of a new class of low-mass black holes," said Todd Thompson, professor of astronomy. at the University of Ohio, in the journal Science.

"The masses of things tell us about their formation and evolution, as well as their nature," said the researcher, lead author of the study. And to add: “People are trying to understand the explosions of supernovae, the explosion of supermassive stars, how the elements are formed within supermassive stars. So if we could reveal a new set of black holes, we would better see why such stars explode, such others do not, such stars form black holes, and such others of neutron stars. And it opens up a new field of study. "

Less mass than a conventional black hole
A potential discovery made using data from the Apogee collaboration (in French, Experience on the galactic evolution of the Apache Point observatory). It collected the light spectra of more than 100,000 stars in the Milky Way in order to detect a particularly not very massive stellar black hole. Experts then reduced the star panel to 200 stellar specimens and finally isolated a giant red star.

The star orbited around an element with a mass less important than a black hole, and much heavier than any neutron star. Using mathematical calculations, the researchers finally determined that it was a black tower with a mass equivalent to 3.3 times that of the Sun. Never seen before.

Discovery of a first planet orbiting a white dwarf

At least one exoplanet has been able to survive the violent transitions that a solar-type star experiences during its lifetime, to the final stage.

In several billion years, when the Sun has swollen to the point of encompassing the orbit of Mars, or even that of Earth, becoming a giant red, will have exhausted all its nuclear fuel, then deflated until it becomes a white dwarf d 'a diameter comparable to that of Earth, will there always be planets around it to testify to it? Astronomers have just made a discovery which proves that this is not impossible! For the first time ever, these scientists have unearthed a giant gas planet orbiting a white dwarf. However, its detection was indirect since what the researchers saw was the evaporation of the outer layers of the planet under the effect of the powerful ultraviolet radiation from the star. In fact, if most of the gases thus torn from the exoplanet escape into space, part of them feed a disc which wraps around the white dwarf and grows at a speed of around 3,000 tonnes per second. The composition of this disc betrays the phenomenon.

The star baptized WDJ0914 + 1914 is located about 1,500 light years from Earth, in the constellation of Cancer. Small, this white dwarf is, however, extremely hot since its temperature is around 28,000 degrees Celsius (about five times the temperature of our Sun). As for the surviving planet, probably quite similar to Neptune, it would be two to four times larger than the star around which it orbits in just ten days and at a distance of about 10 million km. This proximity (on an astronomical scale) is astonishing since the current orbit of the planet is located in the perimeter formerly occupied by the star in the red giant stage. This therefore implies that the giant planet got closer to its star once it became white dwarf, due to gravitational interactions, perhaps with other planets of the system which would also have survived ...

For the moment, obviously, there is nothing to confirm this. However, this unprecedented discovery could lead to other detections of exoplanets orbiting such end-of-life stars. Some, orbiting much cooler white dwarfs, might not be stripped of their atmosphere in this way. And, if others suffered the same fate, the study of the disc forming around the dwarf star could provide valuable information on their atmospheres. These two perspectives are therefore as interesting as the other from a scientific point of view.

Cheops: a mission to shed light on exoplanets

The Swiss-European satellite should bring exoplanetology into a new era. That of the study of exoplanets that Cheops is about to measure.

Since the discovery of the first exoplanet 51 Pegasi b by the Swiss Michel Mayor and Didier Queloz, Nobel Prize in physics 2019 for this discovery, the list of these mysterious extrasolar planets has grown considerably. The limit of 4,000 having been briskly crossed this year, it now looks like a directory of fire PTT! As for the new entrants, unless they are particularly original, they hardly do any more talk about them. What good… since we basically know very little about these planets and that everything we can say about it is still written in the conditional tense. With the Cheops satellite, Switzerland and the European Space Agency nevertheless hope to bring exoplanetology into a new era. In fact, unlike its predecessors Corot and Kepler, Cheops does not have the mission to scan a particular area of ​​the sky to discover new exoplanets whose abundance is no longer in doubt. No, as its name in full CHaracterising ExOplanets Satellite indicates, its role is to observe already identified planetary systems to characterize them and start to bring order and a little more sense in all this, under the responsibility scientist from Didier Queloz, of the Geneva observatory.

A three and a half year mission

What are these planets made of? Do they have an atmosphere? And, if so, what is its composition? Do they have liquid water on their surface? Finally, what do they tell us about the formation of our own solar system? To try to answer these burning questions, scientists first need to know the density of these bodies. Data which they generally do not have and which, at such a distance, can only be obtained by comparing their mass and their size. This is where Cheops comes in. Positioned in low orbit about 700 kilometers above our heads, its telescope equipped with a 30 cm mirror must allow it to measure a maximum of exoplanets with unequaled precision, of the order of 10%. To do this, he will watch them pass in front of their star in order to observe very precisely the drop in luminosity induced and will thus determine their radius, that is to say by applying the method of transits. This will make it possible to obtain the density of those whose mass has already been determined during their detection by the method of radial velocities. Which consists in measuring the oscillation of the star resulting from the gravitational attraction exerted by a planet in orbit around it, this one resulting directly from the mass of the object. However, the task will not be easy, since most exoplanets can only be observed with one or the other of the two methods described above.

Scheduled to last three and a half years, the mission nevertheless aims to provide a short list of well-documented terrestrial-type planets on which the next generation telescopes - such as the James Webb telescope, whose commissioning is scheduled for 2021 and the E-ELT (European Southern Observatory) expected for 2025 - will be able to concentrate on going further in the knowledge of these distant worlds. By the way, Cheops could obviously glean some new aspirants, but also perhaps get their hands on rings, moons and succeed in measuring the temperature of hot Jupiters which intrigue astrophysicists so much since, in our case, in the solar system, giants are more of the frozen kind…

Three central black holes in the heart of a single galaxy

This new discovery could help explain how the largest galaxies in the Universe were able to form so quickly.

Astronomers have discovered three supermassive black holes at the heart of a single galaxy.
Thanks to the Muse instrument equipping the Very Large Telescope based in Chile, an international team of astronomers has just discovered a celestial object with unique characteristics: a galaxy having at its center, not one, but three supermassive black holes.

Called NGC 6240, it is about 400 million light years from Earth in the direction of the constellation Ophiuchus. With its unusual shape reminiscent of a butterfly or a lobster, extremely luminous in the infrared domain, this galaxy had already been talked about just ten years ago, when the Chandra space telescope revealed that 'it contained two supermassive black holes. Today, Muse's extreme sensitivity allows us to detect one more.

Cosmic pocket square
As for these black holes, they are not only three, but they are also colossal. Conventionally, the black holes that inhabit the heart of galaxies are at least a million times more massive than the Sun. This is, for example, the case of Sagittarius A * which is in the center of our Milky Way and which weighs about 4 million solar masses. Nothing compares to the central black holes of NGC 6240 which each have a mass equivalent to no less than 90 million Sun!

How could something so big have escaped astronomers so far? Besides the fact that seeing a black hole which, by definition, emits no light by itself is far from easy, it is also that these three black holes are, on an astronomical scale, practically glued to each other. other. They fit in a cosmic pocket handkerchief of only 3,000 light years!

Merger of three galaxies

Besides the curiosity that such a formation can arouse, never seen before in the Universe, its existence sheds light on one of the fundamental questions in astronomy. How could galaxies as large as those we observe today have formed in just 13.8 billion years (since it is the age of the Universe)? In fact, if NGC 6240 has three black holes, it is actually the result of the fusion of three smaller galaxies. Each of the central black holes of the latter having finally found itself in the center of the whole.

This confirms one of the scenarios proposed to explain the accelerated growth of certain galaxies: they would have grown by the simultaneous fusion of three galaxies and why not more! It is a first step. To be convinced, it would now be necessary to find other objects of the same type in order to prove that NGC 6240 is not just an isolated case.

Nasa: discovery of a new planet that could harbor life

If you ask astronomers how many planets in the universe harbor life, they will likely say there are only two possible answers: one or infinity. We can rule out zero, thanks to the decidedly alive Earth, which means that so far one is the answer. But if we discover another, the answer jumps straight past two to infinity. The reason: You can posit a universe in which the confluence of factors that made life possible here are so complex that the right roll of the dice could statistically happen only once. But if it can happen more than once, why should there be any limit? (Actually, something could be so rare in nature that it happens only two or three times, but the overall zero-one-infinity idea originated with theologians debating atheism, monotheism and infinite polytheism, and planetary scientists just kind of liked it and claimed it as their own.)

Humans have always hoped for infinity, since it would be an awfully lonely universe if we’re the only planet with its porch light on. And with the recent explosion in the discovery of exoplanets (planets orbiting other stars), astronomers now believe that virtually every star in the Milky Way is circled by at least one planet. There are up to 250 billion stars in our galaxy and about 100 billion other galaxies out there—trillions upon trillions of places life could be thriving.

In their search for such worlds, astronomers focus their energy on Earth-like, rocky planets, with atmosphere, water and an orbit that places them in the so-called habitable zone, where temperatures are just right for the water to exist in liquid form. Last week, NASA announced a jackpot: an Earth-sized world in the habitable zone of a hospitable star, just 100 light years from here. The star is known as TOI 700 and the planet is TOI 700 d, the outermost of a litter of three planets. TOI 700 is a red dwarf, a class of stars smaller and cooler than our sun, which were at first thought of as poor candidates for nurturing life, due to their relatively low temperature. But the fact is, as long as the planets orbit close enough to the hearth of the star, they get plenty of light and warmth—and TOI 700 d does.

It was the Transiting Exoplanet Survey Satellite (TESS) that discovered the star, and the Spitzer Space Telescope that took its environmental and chemical measures. TESS uses four on-board telescopes to look for the slight dimming in the light of a star when an orbiting planet passes in front of it. Spitzer makes its observations principally in the infrared spectrum, which is an indicator of heat that can, in turn, yield a lot of data on composition and chemistry.

TOI 700’s other two planets orbit too close to the star’s fires for water not to boil away. But TOI 700 D, which is about 20% larger than Earth, orbits its sun at a distance of about 15 million miles—that’s far closer than Earth’s 93 million miles from the sun, but given the lower temperature of a red dwarf, the planet receives roughly 86% of the stellar warmth Earth does.

Computer models for conditions on TOI 700 D based on that suggest the planet is tidally locked, meaning it keeps the same face turned toward its sun all the time. But an atmosphere could nonetheless help distribute heat to the dark side, and temperatures would certainly be comfortable in the border regions between light and shadow. In one model, the planet is watery, with an atmosphere that is principally carbon dioxide—similar to ancient Mars before it lost its atmosphere and water. In another, the planet is dry and cloudless. Overall, researchers modeled 20 different versions of TOI 700 d, any one—or none—of which could be correct.

That very wealth of possibilities is a statement both of our imagination and our ignorance: we can gather the data we need to imagine more than a dozen and a half plausible versions of the same planet—but don’t have enough data to say which, if any, is correct. And as for the possible existence of life there? We can’t even guess. But exoplanet science is a brand new game. It was only in 1992 that the first exoplanet was discovered. At this point, we’ve not even moved past the training-wheels stage of studying them. If TOI 700 d proves anything though, it’s that there may be extraordinary potential on an extraordinary number of worlds. If you’re a betting person trying to answer that astronomers’ multiple-choice question, consider putting your money on infinity.

The planet Mars is losing water faster and faster

Contrary to what had been established, the precious liquid present in the form of ice evaporates faster than expected

The question torments all astronomers around the world. Will humans find water on Mars if they ever manage to set foot on its soil? If scientists knew that the precious liquid had gradually disappeared from Mars over time, a recent study claims that the process would actually be much faster than expected and that the water would evaporate at an underestimated speed, explains The Independant. And it is now the whole project of a human expedition to the red planet that is called into question. Water evaporates when the sun transforms its molecules into hydrogen and oxygen atoms.

The planet's gravity is then unable to hold them back and they disappear into space. There was a time when Mars was filled with water as several studies have shown. Rivers and lakes were part of the landscape. NASA predicts that the first Mars expedition is expected to materialize within ten years. However, we must qualify. There is nothing to indicate that there will be no more water when man takes his first steps on Martian soil. The evaporation process indeed spans several million years.

With the seasons

The study was carried out using data collected by the Trace Gas Orbiter probe launched in March 2016 and which has been crisscrossing the atmosphere of the red planet since October 2016. On the North Pole of the sun, ice is melting at a speed important, especially when the Sun is closest. The presence of water is intrinsically linked to the discovery of life.

"Not enough, therefore, to question the plans of NASA which plans a human expedition during this century," says Franck Montmessin, French researcher who participated in the study,  “By analyzing the TGO data, we could see that the loss of Martian water is much faster than we thought. And, above all, that it has a cyclical, seasonal rhythm, which depends on the solar lighting at the level of the poles, "he explains.

Two habitable super-Earths discovered around nearby stars

Two recently detected exoplanets, named GJ229Ac and GJ180d, will constitute new prime targets for the search for life.



You probably won't remember their name, but astronomers are not going to forget them. The two exoplanets that researchers at the Carnegie Institution have just discovered have remarkable characteristics. Called GJ229Ac and GJ180d, they are both of a size close to that of Earth, in other words probably rocky, and located in the habitable zone of their respective stars, that is to say capable of harboring l liquid water. These first two elements therefore make them planets theoretically suitable for the appearance of life. But that's not all…

If they deserve so much attention, it is also because they orbit around stars that are closest to our Sun. Indeed, GJ229Ac and GJ180d orbit around two red dwarfs, Gliese 229 (GJ229) and Gliese 180 (GJ180), located respectively 19 and 39 light years from us. If this may seem enormous, it is very little on an astronomical scale. Thus, the closest star to the Sun, Proxima Centauri, is already 4.2 light years away from it. On the scale of the Milky Way, which is approximately 100,000 light years wide, these potentially habitable super-Earths are therefore found in the suburbs of the solar system. For all these reasons, even if the hospitality of the planets orbiting red dwarf stars is still under discussion, it is a safe bet that GJ229Ac and GJ180d will be among the first targets of telescope observations. new generations, such as the James-Webb telescope, which is scheduled to start operating in March 2021.

While waiting for these state-of-the-art devices to look into their case, scientists already have some information on these almost neighboring worlds. The mass of GJ229Ac and that of GJ180d are equivalent to 7.9 and 7.5 times that of Earth. The first revolves around its star in 122 days and the second in 106 days. Finally, while GJ229Ac is the potentially habitable super-Earth orbiting a star which has a brown dwarf companion closest to us, GJ180d constitutes the “temperate” super-Earth whose orbit is not locked. (unlike the Moon which always presents the same face to the Earth and the majority of exoplanets orbiting red dwarfs) closest to us. A feature that further increases the chances that GJ180d can shelter life

SpaceX: last successful test before sending a manned flight to the International space station

Elon Musk's space company successfully simulated, at the Kennedy Center in Florida, the emergency ejection of astronauts from a rocket.

It was the last step before I could send a manned flight to the International Space Station. On Sunday January 19, SpaceX successfully simulated the emergency ejection of astronauts from a rocket moments after launch, according to a live broadcast of the test, the last major test before the shipment is expected in a few months from a NASA crew to the International Space Station. The test launch, with no one on board, started at 10:30 a.m. at the Kennedy space center in Florida with the takeoff of a Falcon 9 rocket, at the top of which the new SpaceX capsule, Crew Dragon, was fixed. The rocket was programmed as if it were to launch the spacecraft into orbit.

One minute and 24 seconds after takeoff, at an altitude of approximately 19 kilometers above the Atlantic and while the rocket was traveling at more than 1,500 km / h, an abandonment sequence was triggered to simulate a anomaly: the capsule ignited its powerful SuperDraco thrusters to eject from the rocket and distance itself from it as quickly as possible. In a manned mission, the maneuver would save the astronauts strapped inside Dragon, if the rocket ever had a problem or followed a bad trajectory.

Shortly after the sudden separation, the rocket disintegrated into a large ball of fire, which SpaceX had warned of. Crew Dragon continued, alone, its course towards the sky until about 40 km of altitude, before falling naturally towards the Atlantic Ocean. Then, the four large parachutes of the capsule opened to slow the fall and the ditching in the Atlantic, where rescue teams had been pre-positioned. Nine minutes after takeoff, Crew Dragon landed, apparently without damage. Analysis of the capsule and the flight data will confirm whether everything went well, and whether the vehicle is considered reliable for placing astronauts there. A press conference will take place Sunday at 11:30 a.m. (4:30 p.m. GMT) with officials from NASA and SpaceX.

Two American astronauts for a flight in March

The seemingly normal course of this perilous test is great news for SpaceX and for NASA, which urgently needs to certify a vehicle to transport its astronauts to the ISS this year. Since 2011, the United States has been obliged to have its astronauts travel on the Russian Soyuz rockets, the only ones to have this capacity since the retirement of the American shuttles. NASA signed a similar contract with Boeing, which developed the Starliner capsule.

In March 2019, SpaceX had made a one-week empty round trip to the ISS with Crew Dragon. In April, a ground test of the SuperDraco propellants had caused an explosion, but SpaceX and Nasa claim to have solved the problem after investigation. Boeing was to perform the same mission to the ISS in December, but an orbit error led to shortening the mission and bringing back Starliner two days after launch, a setback for the aerospace giant. The first manned flight of Crew Dragon will have as passengers American astronauts Doug Hurley and Bob Behnken. If all goes well, this mission will take place at the earliest in early March, said Kathy Lueders, head of NASA's commercial flight program on Friday.