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Our Large, Adult Galaxy Is As Massive As 890 Billion Suns

The milky way
(Image: © European Souther Observatory)

Our home galaxy has a new, super-precise mass measurement: about 890 billion times the mass of our sun. That's 3.9 tredecillion lbs. (1.8 tredecillion kilograms), a tredecillion being a 1 with 42 zeros after it, or 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000. That amounts to about 6 billion billion billion elephants, 296 quadrillion Earth masses or 135 times the mass of the supermassive black hole in the image released back in April.

Measuring the Milky Way's mass presents some unusual difficulties, because we live in it. There's no way to stick galaxies on scales, so researchers typically "weigh" galaxies by tracing the movements of stars inside the galaxies, which can reveal how the galaxy's gravity is influencing those stars. But while anyone with a reasonably good telescope can spot the full Andromeda galaxy, most of the body of the Milky Way is hidden from us. 

Related: 11 Fascinating Facts About Our Milky Way Galaxy

Nearby stars and dust clouds block faraway stars from our view, so researchers have to use more-sophisticated technological and statistical methods to infer what how our galaxy is moving and what it looks like from the outside. Also, our own solar system is moving in its own eccentric way through the galaxy, and so researchers have to correct for that in these measurements.

The new study relied on two key compilations of data. This information revealed how gas, stars and other material move in different parts of the Milky Way. Scientists can use this to produce a "rotation curve" that reveals how heavy the galaxy really is.

"The disk of our galaxy is spinning but not uniformly," said study co-author Fabio Iocco, an astrophysicist at Imperial College London. "Objects at different distances from the center of the galaxy go around that center at different speeds."

That "spinning force," he told Live Science, has to be balanced against the gravitational force of the galaxy at each point on the galactic disk. If it weren't, the galaxy would shred itself and stars and nebulas would be flung out into the intergalactic emptiness.

"If you do it for different distances, from the center until very far away, you get an estimate of the mass enclosed at increasing distances. So you can draw not only a total mass, but a mass distribution," Iocco said.

Of course, the Milky Way consists of more than just stars and gas and other visible things. Like with nearly all known galaxies, most of our galaxy's mass is locked up in an unseen halo of dark matter, exerting gravitational influence without forming any astrophysical objects that we can directly observe.

In this case, the researchers found that the dark matter's mass is equal to about 830 billion times the mass of our sun, or about 93% of the galaxy's total mass.

The researchers compared their results to past efforts to measure the galaxy's mass and found that their conclusions largely lined up nicely with past research. The paper, which has not yet been published in a peer-reviewed journal, was made available Monday (Dec. 9) to the arXiv database.

Originally published on Live Science.

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  • rod
    "In this case, the researchers found that the dark matter's mass is equal to about 830 billion times the mass of our sun, or about 93% of the galaxy's total mass."

    That is a critical component in the mass measurement of 890E+9 solar masses for the Milky Way.
    Reply
  • Alexanderzi
    So just imagine, which kind of the matter could weight so many??? Ofcorse it is very density metal's
    Reply
  • rod
    Alexanderzi said:
    So just imagine, which kind of the matter could weight so many??? Ofcorse it is very density metal's

    metals are placed on the Periodic Table of the Elements, no dark matter is there at this time. Metals can also be detected in starlight too as well as molecules in the gas in the interstellar medium. So far dark matter remains elusive. At the present - there seems to be no evidence that our solar system is composed, 93% of dark matter :)
    Reply
  • Alexanderzi
    rod said:
    metals are placed on the Periodic Table of the Elements, no dark matter is there at this time. Metals can also be detected in starlight too as well as molecules in the gas in the interstellar medium. So far dark matter remains elusive. At the present - there seems to be no evidence that our solar system is composed, 93% of dark matter :)
    I'm assure you it is, yes metal's consist in the starlight, because each star has earthcore which consist of the metal's or liquid metal's , so every particles of the light must consist some element's of this beginning.
    Reply
  • rod
    Alexanderzi said:
    I'm assure you it is, yes metal's consist in the starlight, because each star has earthcore which consist of the metal's or liquid metal's , so every particles of the light must consist some element's of this beginning.

    My comment - In astronomy, *metals* is jargon for elements on the Periodic Table that are heavier than helium, e.g. lithium, carbon, iron, etc. Stars having *earthcore*, I do not find in references like 'Advanced Stellar Astrophysics" by William K. Rose, Cambridge University Press, 1998.
    Reply
  • Alexanderzi
    rod said:
    My comment - In astronomy, *metals* is jargon for elements on the Periodic Table that are heavier than helium, e.g. lithium, carbon, iron, etc. Stars having *earthcore*, I do not find in references like 'Advanced Stellar Astrophysics" by William K. Rose, Cambridge University Press, 1998.
    You didn't find it, because no body been there, and this is just a theory. Everything in our life has begin core, I think even a stars must have it too. May be it core consist of the liquid metal's , or something like liquid hydrogen. Did you read that some scientist's transformed liquid hydrogen to the liquid metal's through very high pressure, so this mean that every particle's of any element's could turn in the other element's. - In the other words they are compressed molecule's so high , that this transform to the liquid matter with metal's , so I think in the star must be the same things inside it, because there are great pressure but very hot environment.
    Yes metal's mean any element's which denser than gas and has a good conduction, so any metallic element's are metal's, because it is a matter itself. For instance you cannot though that silica are the metal's , but the silica denser than gases, but silica semi-conductor. Silica is something between matter and gases, silica is half burned matter, has numerical value 4. That's why e.g. Saturn has very high amount's of Silica compounds, because the Saturn are 4th planet. A half burned matter.
    Reply