How massive is the Milky Way? Its a simple concern to ask, but a hard one to address. Envision a single cell in your body attempting to identify your total mass, and you get an idea of how difficult it can be. In spite of the obstacles, a brand-new study has computed a precise mass of our galaxy, and its smaller than we thought.
The speed at which a star orbits is proportional to the amount of mass within its orbit, so from a galaxys rotation curve you can map the function of mass per radius and get a good concept of its overall mass. Weve measured the rotation curves for numerous close-by galaxies such as Andromeda, so we understand the masses of many galaxies quite precisely.
Considering that we are in the Milky Way itself, we dont have an excellent view of stars throughout the galaxy. Toward the center of the galaxy, there is a lot gas and dust we cant even see stars on the far side. So instead we measure the rotation curve utilizing neutral hydrogen, which emits faint light with a wavelength of about 21 centimeters. This isnt as precise as excellent measurements, but it has actually given us an approximation of our galaxys mass. Weve also looked at the motions of the globular clusters that orbit in the halo of the Milky Way. From these observations, our best quote of the mass of the Milky Way is about a trillion solar masses, take or offer.
The distribution of stars seen by the Gaia studies. Credit: Data: ESA/Gaia/DPAC, A. Khalatyan( AIP) & & StarHorse team; Galaxy map: NASA/JPL-Caltech/R. Hurt
This brand-new research study is based on the 3rd information release of the Gaia spacecraft. It consists of the positions of more than 1.8 billion stars and the motions of more than 1.5 billion stars. While this is only a fraction of the approximated 100-400 billion stars in our galaxy, it is a large sufficient number to calculate an accurate rotation curve. Which is exactly what the team did. Their resulting rotation curve is so accurate, that the team could determine whats referred to as the Keplerian decrease. This is the outer region of the Milky Way where excellent speeds start to drop off roughly in accordance with Keplers laws considering that nearly all of the galaxys mass is more detailed to the stellar center.
The best fit to their information put the mass at about 200 billion solar masses, which is a fifth of previous price quotes. The outright upper mass limit for the Milky Way is 540 billion, meaning that the Milky Way is at least half as enormous as we believed.
Recommendation: Jiao, Yongjun, et al. “Detection of the Keplerian decline in the Milky Way rotation curve.” arXiv preprint arXiv:2309.00048 (2023 ).
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One way to figure out a galaxys mass is by looking at whats known as its rotation curve. The speed at which a star orbits is proportional to the amount of mass within its orbit, so from a galaxys rotation curve you can map the function of mass per radius and get a good concept of its total mass. Weve determined the rotation curves for a number of neighboring galaxies such as Andromeda, so we know the masses of many galaxies rather precisely.
From these observations, our finest price quote of the mass of the Milky Way is about a trillion solar masses, offer or take.
The best fit to their data placed the mass at about 200 billion solar masses, which is a fifth of previous estimates.