Asteroid Ryugu is made of dust grains older than the sun!

Asteroid Ryugu is made of dust grains older than the sun!

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[EN VIDÉO] These are all known asteroids in our solar system. Look how many there are: Here are all the asteroids identified by astronomers since they were first discovered in 1801. The number of discoveries has literally skyrocketed since the late 20th century.

In 1950, Erwin Schrödinger, one of the founders of quantum mechanics, who had worked both on the elucidation of the nature of life and on the appearance of matter in a model of relativistic cosmology, explained in one of the four public lectures entitled “Science as a constituent element of humanism” that “the isolated knowledge acquired by a group of specialists in a narrow field has no value in itself; it has value only in the synthesis that binds it to all other knowledge, and only to the extent that in that synthesis it really contributes to answering the question: who are we? “.

In fact, with space missions like that of the Japanese probe Hayabusa-2, which was in orbit around the asteroid (162173) Ryugu from June 2018 to November 2019, we are searching for our roots and our cosmic identity. There she took samples that have since arrived on Earth and are still being analyzed.

A presentation of the Hayabusa 2 mission. For a fairly accurate French translation, click on the white rectangle at the bottom right. Then the English subtitles should appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose French. ©DLR

They are therefore from a member of the Apollo family of asteroids, near-Earth asteroids, and it is even one of those that are potentially dangerous. It was discovered in 1999 and it quickly became clear that it belonged to the C-type asteroids, i.e. it was similar to the carbonaceous chondrite meteorites known on Earth.

Their chemical composition is therefore similar to the matter of the molecular and dusty cloud in which the primitive solar system was born, without the light and volatile elements such as ice. It was therefore a target of choice to understand the origin of the planets and the sun, and therefore the origin of the biosphere and the noosphere, so Hayabusa-2 gave us much more than just close-up views of the asteroid (162173) Ryugu.

We can see this with the announcement of an article by an international team of researchers led by Jens Barosch and Larry Nittler of the Carnegie Institution for Science, published in The Astrophysical Journal Letters.

The members of this team let it be known that they found nothing less than pre-solar grains in the samples brought back from Hayabusa-2.

A key to the stellar cycle in the Milky Way

By this we mean solid materials that condensed into grains, not in the protoplanetary disk of gas and dust that cooled around the young Sun about 4.5 to 4.6 billion years ago, but in the stellar atmospheres of before the Sun was born Stars existed before and from which they were expelled at the end of their lives to find themselves in the interstellar medium and then in the protosolar nebula at the origin of the solar system.

Remember that there is a true stellar cycle in the Milky Way, causing it to chemically evolve with increasing heavy element enrichment of the interstellar medium. In this medium, molecular and dusty clouds, dense and cold, collapse by gravity, destabilized under the action of a pressure, whether from density waves in the arms of our galaxy or from the shock wave of a supernova explosion.

As the clouds collapse, they fragment and form nurseries, some of which will develop very rapidly, exploding into supernovae and injecting new heavy elements into the cloud where star formation continues. The explosion of one of these stars, called Coatlicue, is believed to have caused the collapse of the protosolar cloud in which our Sun was born. More generally, stars at the end of their lives will return the matter that formed them to the interstellar medium, but with new elements, an environment in which new stars are born for the same reasons.

Jens Barosch therefore says that among the finds in the Ryugu samples, “different types of pre-solar grains come from different types of stars and stellar processes that we can identify from their signatures. The ability to identify and study these grains in the laboratory can help us understand the astrophysical phenomena that shaped our solar system and other cosmic objects.”

Indeed, using sophisticated microanalytical instruments, cosmochemists can measure the abundance of different isotopic nuclei of an element, differing in their number of neutrons, and compare them to those measured in the carbonaceous chondrites that impacted Earth.

On this subject, and still in a Carnegie Institution for Science press release, Larry Nittler states that “the composition and abundance of the presolar grains we found in the Ryugu samples are similar to those we previously found in carbonaceous chondrites to have. This gives us a more complete picture of the formation processes of our solar system, which can inform models and future experiments with samples from Hayabusa2 as well as other meteorites.”

In this video, Philip Heck talks about his research on pre-solar grains, minerals that formed before our solar system was born. Science at FMNH is a podcast and video series that provides a behind-the-scenes look at the science, collections and research at the Field Museum in Chicago. For a fairly accurate French translation, click the white rectangle at the bottom right. Then the English subtitles should appear. Then click on the nut to the right of the rectangle, then on “Subtitles” and finally on “Translate automatically”. Choose French. © Field Museum

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