To map these structures, astronomers focus on individual stars. The composition of each star records its place of birth, age, and composition at the time of its birth, so by studying starlight it is possible not only to create genealogies but also to map galaxies. By placing stars in time and place, astronomers can trace history and infer how the Milky Way was built piecemeal over billions of years.
The first large-scale efforts to study the formation of the primordial Milky Way galaxy began in the 1960s, when Orin Eggen, Donald Linden Bell, and Alan Sandage, a former graduate student of Edwin Hubble, discovered that the galaxy They claimed that it had disintegrated from a rotating gas cloud. For a long time afterwards, astronomers believed that the first structure to appear in our galaxy was a halo, followed by a bright, dense disk of stars. As more powerful telescopes came online, astronomers began to create increasingly accurate maps and refine their ideas about how galaxies came together.
Everything changed in 2016 when the first data from the European Space Agency’s Gaia satellite returned to Earth. Gaia will precisely measure the paths of millions of stars across the galaxy, helping astronomers determine where those stars are located, how they move through space, and how fast they travel. You can know. Thanks to Gaia, astronomers have been able to paint a clearer picture of the Milky Way, and that picture has revealed many surprises.
This bulge is peanut-shaped rather than spherical, and is part of a large bar stretching out at the center of our galaxy. The galaxy itself is twisted like the brim of a tattered cowboy hat. The thick disk is also widening and thickens toward the edges, which may have formed before the halo. Astronomers don’t even know how many spiral arms this galaxy actually has.
The map of our island world is not as tidy as it once seemed. It’s not calm either.
“If you look at traditional pictures of the Milky Way, you’ll see a nice spherical halo and a regular-looking disk, all calm and still. But what we now know is that this galaxy is out of balance. It’s a state of affairs,” he said. charlie conroy, an astronomer at the Harvard-Smithsonian Center for Astrophysics. “The image of simplicity and orderliness has been completely abandoned in recent years.”
New map of the Milky Way
Three years after Edwin Hubble realized that Andromeda was a galaxy in its own right, he and other astronomers were busy imaging and cataloging hundreds of island universes. Because these galaxies were thought to exist in several common shapes and sizes, Hubble developed a basic classification system known as the tuning fork diagram. It divides galaxies into two categories: elliptical and spiral.
Astronomers still use this scheme to classify galaxies, including our own. For now, the Milky Way is spiral-shaped, with arms that are the main nurseries for stars (and therefore planets). For half a century, astronomers thought there were four major arms: the Sagittarius arm, the Orion arm, the Perseus arm, and the Cygnus arm (or what we unimaginatively called the local arm). (lives on small branches). But new measurements of supergiants and other objects paint a different picture, and astronomers are wondering how many arms they have, how big they are, and even whether our galaxy is an oddity among islands. There is no consensus either.
“Surprisingly, very few outer galaxies exhibit four spirals extending from the center to the outer region.” Chouilletsaid an astronomer at China’s Zishan Observatory in an email.
