Our cosmic home is typical for stars, but not for galaxies | by Ethan Siegel | Starts With A Bang! | Aug, 2024

MarylandDigitalNews.comSCIENCE

posted on Aug. 19, 2024 at 2:28 pm

This view of the Hercules galaxy cluster showcases an enormous number of large, massive galaxies clustered together in a single region of space. Although these galaxies contain most of the stars within this region of space, there are several dozen times as many galaxies total, with most of them being faint, low-mass, and below the threshold of detectability to the instrument used to acquire this image. (Credit: ESO/INAF-VST/OmegaCAM. Acknowledgement: OmegaCen/Astro-WISE/Kapteyn Institute)

Most stars in the Universe are located in big, massive, Milky Way-like galaxies. But most galaxies aren’t like ours at all.

Upon viewing the night sky, many frequently wonder what remains unseen.

This long-exposure image captures a number of bright stars, star-forming regions, and the plane of the Milky Way above the southern hemisphere’s ALMA observatory. The nearest stars are only a few light-years away: less than a factor of 10 from the edge of the Oort cloud. But more distant stars and features, still visible with the naked human eye, can be tens of thousands of light-years away instead. (Credit: ESO/B. Tafreshi (twanight.org))

Our glittering stellar canopy contains only a few visible galaxies.

Behind the dome of a series of European Southern Observatory telescopes, the Milky Way towers in the southern skies, flanked by the Large and Small Magellanic Clouds, at right. Although there are several thousand stars and the plane of the Milky Way all visible to human eyes, there are only four galaxies beyond our own that the typical unaided human eye can detect. (Credit: ESO/Z. Bardon (www.bardon.cz)/ProjectSoft (www.projectsoft.cz))

With the power of modern observatories, so much more becomes apparent.

This comparison image, showing the same region as imaged by Hubble’s eXtreme Deep Field (top) and JWST’s JADES survey (bottom) showcases a selection of many ultra-distant galaxies found in the young Universe. When we observe the Universe at great distances, we’re seeing it as it was in the distant past: smaller, denser, hotter, and less evolved. Back to the limits of JWST’s capabilities, we see evidence for stars and galaxies everywhere. (Credit: NASA, ESA, CSA, STScI (JWST); ESA/Hubble & NASA and the HUDF09 team (Hubble))

A total of between 200–400 billion stars exist within the Milky Way alone.

The European Space Agency’s space-based Gaia mission has mapped out the three-dimensional positions and locations of more than one billion stars in our Milky Way galaxy: the most of all-time. The ability to measure stellar parallax, or how the actual (rather than apparent) position of a star changes over the course of a calendar year, is greatly aided by superior instrumentation, large aperture size, Gaia’s location in space, and the development of photography and computerized identification of the relative shifting of stars. Over multiple years, Gaia can help provide information about the velocities of these stars as well. (Credit: ESA/Gaia/DPAC)

Many possess Sun-like qualities: abundant in heavy elements, and containing rich planetary systems.

MarylandDigitalNews.comAugust 19, 2024

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