Part of the Milky Way formed much earlier than we thought!

Image composite de la totalité du ciel terrestre comprenant les données de quelque 1,8 milliard d'étoiles de la Voie lactée. Observation réalisées par le satellite Gaia et dévoilées fin 2020 dans le cadre du Gaia EDR3. © ESA, Gaia, DPAC, CC BY-SA 3.0 IGO

Coming out Big BangEspecially afterChapter From Cosmic radiationContains the visible universe Atoms OfHydrogen And d ‘RadiationMany of them Isotopes And a bit Lithium But there is no trace of such heavy elementsNitrogenThe Carbon And thisOxygen. First Stars They form and eventually bring out the universe Dark age So one can assume that having a better approximation is not Metals And with a Metallicity Zero as they say Astronomers In their language, i.e. no elements heavier than helium.

According to Fixed cosmological modelIt must first form small galaxies, which together form larger galaxies that will grow rapidly. Gas Sent by fibers Black material Cooling according to the new paradigm of galaxy evolution, these fibers play a fundamental role and are only secondary to all fusion of galaxies, contrary to what we still thought a year ago.

It is still believed, however, that basically one Spiral galaxy Initially develops as a Protoplanetary disk With one Cloud The gravity of the rotating object falls. The Centrifugal force Opposing this contraction perpendicular to the axis of rotation, the initial cloud is flat.

A galaxy that is changing chemistry

The theory of galaxy structure and evolution proves that stars form very quickly because they are so large. Beyond 8 Masses Solar cells, they explode Supernovae After assembling the heavier embryos up Iron, Enriching a galactic medium in galaxies where new stars are born. So there is the chemical evolution of stars and galaxies that allows dating. Thus, a Red dwarfDecreases in metallic elements beyond lithium would indicate a star born 10 billion years ago Yellow dwarf Like us The sunRich in heavy elements, a few billion years younger.

The Theory of evolution Star size and Brightness A star varies according to its age for a given mass. Thus, when some stars see the thermonuclear fusion of the heavier elements of the nuclei at their centers, the star will continue in an envelope around this center while at a short point called the subgeneration. The red giant.

In short, by analyzing the chemical composition and brilliance of a star, we can calculate its age, which astronomers have done to approximately 250,000 stars. Milky Way With help Large Sky Area Multi-Object Fiber Spectroscopic Telescope (I.e. Telescope Multi-object spectroscopy Optical fiber Large field, abbreviated lamost) – a Chinese optical telescope with a diameter of four meters.

Mao Zedong and Hans-Walter Ricks of the Max-Blank Institute for Astronomy in Heidelberg, Germany, combined data from Lamost with data on the brightness and position of similar stars in the I ‘set.Initial data release3 From the Gaia satellite of (EDR3)ESA Dedicated to astronomy. The results of this combination have been published in popular magazines Natural.

In this edition of Space 2018, we go to the stars: astronomers using the European space telescope Gaia have compiled an unprecedented list of one billion stars in the Milky Way, which led to decades of discovery. © Euronews

A galactic archeology that can be read in layers of stars

About Kaya’s astronomical data levels and best measurements Gears About 1.5 billion stars in the Milky Way. The latest was released in December 2020, and by 2021 Lamost had delivered 9 million stars. Only a few of these stars were in the red subgiant phase, studied with 250,000 lamostas, but eventually the halo and disk structure and dating Milky Way were clarified.

Its structure is doubled. The first is a thin, dense disk, about 2,000 in thickness Light years And where are the hands of our galaxy, the stars are mainly born today. He himself is still immersed in a disk Spreads Its thickness is about 6,000 light years.

The thin disk contains most of the stars we see as a dim band of light in the sky Night time We call it the Milky Way. The thick disk is three times the height of the thin disk but the radius is small, only a few percent of the Milky Way galaxy in the solar system.

The Star halo Almost spherical stars andSpherical clusters Around the Milky Way. The stars there are as old as the Milky Way galaxy with less metallicity. No dust like disk. This halo is immersed in a hot plasma halo, in turn a Dark matter particle halo According to the standard cosmological model.

A different galaxy chronology

It now appears that there may have been two uniquely important stages in the history of the Milky Way, which is surprising, according to the ESA report.

The first phase begins 0.8 billion years later Big Bang About 13 billion years ago, the thick disk was the opposite of what we already thought and it was starting to form stars there. But about 2 billion years later, after an acceleration in the rate of star formation, a major peak occurs and is explained by the young Milky Way and a fusion. Dwarf galaxy, A galaxy called Gaia-Enceladus. The name comes from Greek mythology: EnceladusDuring Gigantomachi, one of the giants, the son of Gaia (Earth) and Uranus (heaven), was buried under the mountain without action by Athena. EdnaOccurs from Earthquakes And explosions.

This fusion is certainly comparable to the mass of our galaxy’s self-gravitational stellar fluid, thrown into a pool, and was thought to have in some way “heated” the thin disk star gas. , It evaporates and expands to form a thick disk.

It was during this time that the star halo formed at the same time and for the same reason.

But in the case now proposed, the thin disk would have been born only after this merger and star formation on the thick disk would have continued until about 6 billion years after the Big Bank drastically reduced its gas content. During this time, the metallicity of the thick disk is increased by more than 10 times.

As a bonus, astrophysicists determined that the metallicity on the disk was relatively uniform, indicating that turbulent composition processes provide efficient transport and a combination of newly formed elements released into the galaxy by supernova explosions.

This scene may be a scene of several large spiral galaxies. We will probably find out through observations made in the coming decade James Webb Space Telescope.

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