Due to the newest Gaia satellite catalog from the European House Company (ESA), a world crew led by astronomers from the Paris Observatory–PSL and the CNRS has achieved probably the most correct measurement of the mass of the Milky Way. This examine opens necessary questions in cosmology, notably on the quantity of dark matter contained in our galaxy.
The total mass of the Milky Way is estimated to be solely 200 billion occasions that of the sun (2.06 x 1011 solar masses), marking a major downward revision—roughly 4 to 5 occasions decrease than earlier estimates.
This new worth was derived from the third data release of the Gaia catalog published in 2022, which offers complete knowledge for 1.8 billion stars, encompassing all three spatial elements and three velocity elements in a six-dimensional space throughout the Milky Way.
The bearable lightness of the Milky Way
Utilizing the Gaia knowledge, scientists had been capable of assemble probably the most correct rotation curve ever noticed for a spiral galaxy, on this case our personal galaxy, and deduce its mass. Previous to Gaia, acquiring a sturdy rotation curve for our galaxy was difficult, in contrast to the case for exterior spiral galaxies. This problem stemmed from our place throughout the Milky Way, which made it unattainable to exactly distinguish the motions and distances of stars within the galactic disk.
Of their examine printed on September 27, 2023, within the journal Astronomy and Astrophysics, scientists discovered the rotation curve of our galaxy is atypical: in contrast to these decided for different massive spiral galaxies, it’s not flat.
Quite the opposite, on the outskirts of the disk of the galaxy, this curve begins to lower quickly, following the prediction referred to as the Keplerian decline.
Questioning cosmology
Acquiring a rotation curve for the Milky Way that displays a Keplerian decline necessitates situating our galaxy inside a cosmological framework.
Certainly, one of many main breakthroughs in fashionable astronomy was the conclusion that rotational velocities of the massive disks of spiral galaxies had been a lot sooner than what could be anticipated from a Keplerian decline. Within the Nineteen Seventies, astronomers Vera Rubin, who used observations of ionized fuel, and Albert Bosma, who studied impartial fuel, demonstrated that the rotation velocity of spiral galaxies stays fixed, nicely past their optical disks.
The fast consequence of this discovery was the proposition of the existence of dark matter —further to observable matter—distributed in a halo surrounding the disks of spiral galaxies. With out this dark matter, the rotation curves would have adopted a decline referred to as “Keplerian.” The latter signifies the absence of serious quantities of matter exterior the optical disk.
Extra data:
Y.-J. Jiao et al, Detection of the Keplerian decline within the Milky Way rotation curve, Astronomy & Astrophysics (2023). DOI: 10.1051/0004-6361/202347513. On arXiv: DOI: 10.48550/arxiv.2309.00048
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The revisited mass of the Milky Way is way smaller than expectations from cosmology (2023, September 27)
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