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…