The first steps of an exoplanet seen for the first time

Finding exoplanets around young stars close to our Earth is the dream of astronomers. They see it as an opportunity to study closely the formation and evolution of this type of planetary system. And such an opportunity presents itself to them today with a red dwarf and its Neptune type planet.

AT Microscopii is a star in the Small Satellite Set … “data-url =” “data-more =” Read more “>constellation of Invented in 1595 by Zacharias Janssen
Invention of the microscope
The invention of this device remains disputed, several sources … “data-image =” marke-bresser-02.jpg “data-url =” “data-more =” Read more “>Microscope. Although only 32 light years de notre Structure du globe…” data-image=”” data-url=”” data-more=”Lire la suite”>Terre, she is invisible toeye naked. It is smaller than our Sun is the closest star to Earth, from which it is about 150 million kilometers apart. The Sun is located 8.5 kparsecs from the center of the Milky Way. In the classification of stars, the sun is a G2 type star.
La masse…” data-image=”” data-url=”” data-more=”Lire la suite”>Soleil. This is what astronomers call a woman rouge. It is less than 30 million years old – 150 times less than our Sun. And keeps around it a vast disc of debris, the rest of its formation.

For more than a decade, astronomers have hoped to find an exoplanet there. It is now done. The data transmitted by the Transiting Exoplanet Survey Satellite (Tess) and speak telescope spatial Spitzer confirm the presence of a Giant neptune – 58 times more massive than our Earth and 8% more voluminous than Neptune – who goes around AT Microscopii in 8.5 days. A planet called AU Mic b.

The system offers astronomers a unique opportunity to study how the planets and their atmospheres form, evolve and interact with their stars. “We believe that AU Mic b formed far from its star and migrated to its orbit current, which can happen when the planets gravitatively interact with a disk of gas or with other planets “, explains in a communicated, Thomas Barclay, associate researcher in the Tess program at Goddard Space Flight Center (It’s inUnited States).

Learn more about the formation of planets

This new system appears very different from another, yet belonging to the same stellar association. The system formed by Beta Pictoris and its two exoplanets. The star is already bigger and hotter than AT Microscopii. But it is also surrounded by a disk of debris. In contrast Beta Pictoris b and c are at least 50 times more massive than AU Mic b. And they take 21 and 3.3 years respectively to go around their star.

“The orbit of Beta Pictoris b does not seem to have migrated. The differences between these similar age systems can tell us a lot about how the planets form and migrate. ”, remarks Thomas Barclay.

Another transit event may have been seen in the data

Before concluding, astronomers report that another transit event – this is how they call the passage, from our point of view, of a planet in front of its star – could have been seen in the data of Tess. To confirm the existence of a second exoplanet in the AU Mic system, however, we will have to wait for new observations later this year.

Mysterious ripples discovered near the star AU Microscopii

By analyzing images acquired with the In 1993, ESO launched the VLT (Very Large Telescope) project and decided to install it on the Cerro Paranal site in the Chilean Andes, where the climate is particularly favorable for astronomical observations. It … “data-image =” “data-url =” .com / sciences / definitions / univers-vlt-2147 / “data-more =” Read more “>VLT and Hubble, astronomers have been able to study a dust disk located around a nearby star called AU Microscopii. They discovered hitherto unknown structures there. Similar to animated waves of a movement fast, they are nothing like what has been observed or envisaged so far. The origin and nature of these structures offer researchers a whole new field of investigation.

Article fromTHAT published on 08/10/2015

AU Microscopii (AU Mic) is a young star, located 32 light years from our Solar system. She is surrounded by a dust disk extended consisting ofasteroids smashed to pieces by violent collisions. The study of similar debris discs is likely to supplement our knowledge of the processes of planetary formation from such structures.

Astronomers looked for the slightest sign of distorted or lumpy structure – testifying to the possible existence of planets – in the AU Mic disc. To this end, in 2014, they used the instrument Sphere, newly installed on the VLT (Very Large Telescope), in Chile. Helped by this powerful device capable of discerning the slightest contrasting detail, they then made a strange discovery.

“Our observations revealed something unexpected”, reports Anthony Boccaletti, researcher at Lesia (Observatoire de Paris, CNRS, UPMC, Paris-Diderot) and first author of the article published in the October 8, 2015 edition of the journal Nature. “The images acquired by Sphere reveal a set of unexplained structures within the disc. They have an arched or wavy shape, very different from what has already been observed in the past. “

The ripples in the dust disk surrounding the AU Microscopii star are visible in this time-lapse animation created from images acquired by Hubble and the VLT with Sphere. © Eso, Nasa, Esa

Very fast ripples

On the new images appear, such as Wave and swell
Note that, offshore, we will talk more readily of … “data-image =” “data- url = “” data-more = “Read more”>waves on the surface of the water, five arches generally forming an undulating structure at different distances from the star. After identifying them using Sphere data, the team consulted old images of the disc acquired in 2010 and 2011 by the spectrographe Hubble STIS imager. It thus appeared, not only that these structures appeared on the images of the space telescope, but also that they had changed over time. In fact, these undulations move at a speed having a direction and an intensity is represented by a vector, the speed vector. Relative speed is the speed of a body in relation to another or in relation to a benchmark. “Data-image =” 9 / 319daf63f4_77541_leibniz-dp.jpg “data-url =” “data-more =” Read the definition “>speed very high ! But observe the disk by the edge complicates the interpretation of its three-dimensional structure.

“After having carried out a new processing of the images resulting from the data ofHubble, we managed to reconstruct the movements of these strange structures over a period of four years, specifies Christian Thalmann (ETH Zurich, Switzerland). We were able to see that the arches were moving away from the star at speeds of up to 40,000 km / h! »

The structures farthest from the star seem to move at higher speed than the nearest. At least three of the structures move so quickly that they may well escape the gravitational pull of the star. The existence of such high speeds excludes the hypothesis that these structures result from disturbances caused on the disc by objects – such as planets – orbiting the star. An unknown element, and truly unusual, must be at the origin of the acceleration of these undulations and their speed so high.

Seeking explanations for the phenomenon

“This discovery brought its share of surprises, adds Carol Grady of the Euréka Scientific Group. And, because nothing like this has been observed or predicted by theory in the past, we can only speculate on the occurrence and the origin of the phenomenon observed ”.

The team cannot say with certainty the cause of these mysterious undulations around the star. However, it considered and ruled out a set of possible phenomena such as the collision of two massive and rare objects similar to asteroids releasing large amounts of dust, or even spiral waves generated by gravitational instabilities inside the system.

“It is possible that the strange structure has a link with the star’s outbreaks. AU Mic is a very active star, important and abrupt bursts d’energy occur on or near its surface, explains Glenn Schneider, of the Steward Observatory, in Arizona, also co-author of the study. One of these bursts could have triggered something on one of the planets – if there are planets -, for example, a violent expulsion of organic matter, nitrogenous matter, etc.
There are different families like:

organic matter, which constitutes living things (animals or plants) or … “data-image =” jpg “data-url =” “data-more =” Read more “>matter which would now spread through the disc, propelled by the intensity of the eruption. “

“Sphere is only in its first year of operation and it is already capable of studying such a disc. We can therefore only welcome this most promising result which confirms the great capabilities of the instrument ”, concludes Jean-Luc Beuzit, co-author of this research and co-designer of the instrument.

The team aims to continue to observe the AU Mic system using Sphere and other instruments, including Alma, in order to understand the processes at work. For the moment, these strange structures remain a real mystery.

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