They unraveled a 100-year-old astronomical mystery: the Milky Way wasn’t always a spiral galaxy

They unraveled a 100-year-old astronomical mystery: the Milky Way wasn't always a spiral galaxy

How do galaxies evolve? Have they always been huge masses of spiral-shaped stars? How do they interact when they come together or collide?

There are many questions that we can ask ourselves about these monsters of space, where our Milky Way It also has answers to give us to the questions that the scientific community has been asking for more than 100 years.

In order to answer them, this week, An Australian astronomer has solved a centuries-old mystery on how galaxies evolve from one type to another and has published it in a top-level international scientific journal.

The same study shows that the Milky Way, the galaxy we live in, was not always a spiral. This is the work of Professor Alister Graham, published in Monthly Notices of the Royal Astronomical Society, which used new and old knowledge and observations to reveal how galaxies evolve in a process known to the scientific community as speciation.

Research shows that Collisions and subsequent mergers between galaxies are a form of “natural selection” which drives the process of cosmic evolution. Something common in all galaxies that also involves our own, the Milky Way.

It is the survival of the fittest. Astronomy now has a new anatomical sequence and eventually an evolutionary sequence in which galaxy speciation is seen to occur through the inevitable marriage of galaxies ordered by gravity.”

In the decades From 1920 and 1930, astronomer Edwin Hubble and others established a sequence of different galaxy anatomies, now known as the Hubble sequence or Hubble tuning fork diagram.

Spiral galaxies like ours, composed of “arms”, Well-ordered, spiraling around a central concentration or “bulge” of stellar bodies, they sit at one end of this sequence.

While the elliptical galaxies such as M87, Composed of an ellipse of billions of stars buzzing chaotically around a disordered central concentration, they sit on the other. Bridging the gap between the two are elongated sphere-shaped galaxies, which lack spiral arms, called lenticular galaxies. But what has been missing from this widely used system so far are the evolutionary paths that link one galaxy shape to another.

“What governs the organization of matter in the universe, on the microscale, is gravity. Matter accretes, condenses, forms clouds of interstellar material, including stars. Major subject organizations, We talk about billions of stars, interstellar matter, dark matter, form galaxies. They are not ‘static’ objects, in the same way that stars have a process of evolution from birth to death, galaxies also change. The issue is to explain how they do it,” he began to explain to Infobae the doctor in astrophysics and researcher at Conicet, Beatriz Garcia, asked about how galaxies evolve.

Galactic evolution is not a new topic, it is indeed a discussion of about a century. and there are proposals that even presented or present diagrams that were thought evolutionary (such as Hubble’s) but that only show a morphological classification. In recent decades they have remarks What combine the visible part of the universe, images acquired by the Hubble Telescope, and infrared (as in the case of this study, which works with those of the Spitzer Telescope): the infrared allows to add low-temperature matter, mainly clouds of interstellar material and add that content to the simulations and modeling that is done in a certain way, making matter evolve, “added the expert.

And he said that the recently published study proposes that Spiral galaxies would be evolutionarily found between two types of lenticular-shaped galaxies (as biconvex lenses) rich and poor in powder. “We are talking about completing, in some way, the galactic evolutionary path,” he summarized the e.specialist member of the International Collaboration in QUBIC.

Galaxies may contain billions of stars neatly following circular orbits in a crowded disk or buzzing chaotically in a spherical or ellipse-shaped swarm. These disks may harbor spiral patterns, with such spiral galaxies defining one end of the long-standing Hubble sequence.

In this sequence, lentil-shaped galaxies, known as lenticular galaxies with a central spherical structure in a spiralless disk, were considered the bridging population between disk-dominated spiral galaxies like our Milky Way and elliptical-shaped galaxies like M87.

In the new study, Professor Graham analysed optical images from the Hubble Space Telescope and infrared images from the Spitzer Space Telescope. of 100 nearby galaxies. By comparing their stellar and central black hole mass, he discovered two types of lenticular galaxies: old and dust-poor and dust-rich.

According to their research, dust-rich lenticular galaxies are built from spiral galaxy mergers. Spiral galaxies may have a small central spheroid plus a disk containing spiral arms of stars, gas, and dust coming out of the center. Dusty lenticular galaxies have noticeably more prominent spheroids and black holes than spiral galaxies and dust-poor lenticular galaxies.

In a turn of events, Professor Graham’s research has shown that spiral galaxies reside halfway between the two types of lentil-shaped galaxies. “This redraws our much-loved sequence of galaxies. More importantly, we now see evolutionary paths through a sequence of galaxy weddings, or what businesses might call acquisitions and mergers,” Graham said.

If dust-poor lenticular galaxies accumulate gas and material, this can gravitationally perturb their disk., giving rise to the spiral shape and favoring the formation of stars, which results in the change in structure and shape. The Milky Way has several smaller satellite galaxies, such as Sagittarius and Canis Major (and others not so small with which it interacts very efficiently, such as the Magellanic Clouds, the closest), and its structure shows us that encounters with other objects have already happened, and that matter has been added, “said astrophysicist García.

He added: “According to this and several other studies, the Milky Way was probably once a dust-poor lenticular galaxy that accumulated material And over time it evolved into the spiral galaxy we live in today. Deep-sky images (which allow us to see galaxies at very different distances from us) that were possible from Hubble, but are also possible thanks to hundreds of ground-based telescopes seem to show that galaxies that we detect or observe as spirals behave similarly.”

About the Galaxy collisions, experts theorize that they can become “dramatic” in some cases. And particularly in our neighborhood. In about 4 to 6 billion years when the Milky Way and the Andromeda Galaxy collide. “Such an event will destroy the current spiral patterns in both galaxies, resulting in a galaxy merging with a more dominant spheroid, spewing many dust clouds, and accompanied by an increase in the mass of the central black hole. It will lead to the birth of a dust-rich lenticular galaxy,” Graham predicts.

Thus, the subsequent merger of two dusty lenticular galaxies seems enough to completely erase their disks and create an elliptical-shaped galaxy, unable to retain clouds of cold gas that harbor dust. In some ways, dust-poor lenticular galaxies appear as a fossil record of the primordial galaxies of the Universe.. These disk-dominated galaxies are very old and common.

This could help explain the discovery by the James Webb Space Telescope (JWST) of a massive galaxy dominated by spheroids only 700 million years after the Big Bang. The new research could also indicate that the merger of elliptical galaxies is a process that could explain the existence of some of the most massive galaxies in the universe, which lie at the heart of clusters of more than 1000 galaxies.

“To be able to make historyThe universe or galactic (or stellar) evolution and that model is conscious, reliable, observations are needed. But these are observations that require powerful telescopes that allow observing distant galaxies, in addition to those that obviously interact with the Milky Way because they are close, part of the Galaxy Cluster We Call Local Group And of course, in addition to telescopes that detect the visible region of the electromagnetic spectrum, telescopes that detect infrared observations outside that energy region are required. The technology to achieve these results is recent.,” Garcia said about this new study that comes to solve centuries-old questions.

“The classification proposed by Edwing Hubble and other colleagues between 1920 and 1930 probably marked the beginning of this Proposal associated with galactic evolution. That proposal lacked a lot of experimental data,” the expert justified.

And he stressed: “It is important to sustain the continued scientific work over time. The results in basic sciences are not instantaneous or immediate, it is required, in addition to having clear objectives, of time, technology, people”.

The expert concluded: “It is also possible that the population questions investments in issues that do not matter in everyday life, however (and that is another mission of scientists), Everything that is done in basic research impacts sooner or later in the life of each person, either by answering fundamental questions associated with the human condition, or because to answer them required a certain technological development that helped to push the limit of knowledge but, in turn, has other uses, and there are many examples in this regard.


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