What Is The Mass Of Entire Milky Way Galaxy?

  • As per the latest measurement, our galaxy weighs in at approximately 1.5 trillion solar masses. 
  • This means the Milky Way has a mass of 2.98 x 1042 kilograms.
  • Astronomers used ESA’s Gaia and NASA’s Hubble observations to obtain this precise figure. 

The Milky Way is the 2nd largest galaxy in the Local Group: Its stellar disk is about 100,000 light-years wide and 1,000 light-years thick. Obviously, you can’t put such a massive structure on a scale, but researchers at NASA have managed to calculate the most precise mass of our galaxy, using Hubble Space Telescope and Gaia Satellite.

According to the previous researches that used a wide range of observational methods, the mass of Milky Way ranges between 3 trillion to 500 billion solar masses.

As per the latest measurement, our galaxy weighs in at approximately 1.5 trillion solar masses (the mass of the Sun is 1.989 x 1030 kilograms). This means the Milky Way has a mass of 2.98 x 1042 kilograms.

How Can They Be So Sure?

A small portion of galaxy’s mass comes from about 200 billion stars and a supermassive black hole at the core (that has a mass of about 4.1 million solar masses within a volume with radius smaller than 6.7 billion kilometers).

Majority of the mass (nearly 85%) of the Milky Way appears to be a hypothetical form of matter, known as dark matter. It doesn’t interact with observable electromagnetic radiation but keeps the stars in their galaxies.

There are billions of galaxies in the universe with masses ranging from 1 billion to 30 trillion solar masses. The mass of Milky Way seems fairly normal for a galaxy of its brightness.

Researchers used ESA’s Gaia and NASA’s Hubble to examine the 3D movement of sets of hundreds of thousands of stars orbiting the galaxy’s center. These sets are also known as globular star clusters.

Source: NASA

The dark matter cannot be observed, but its influence on visible celestial bodies such as the globular clusters can be used to measure its mass. The team analyzed Hubble and Gaia data to measure the globular clusters’ sideways motion to obtain a more accurate speed (the more massive the galaxy, the quicker its stars move under the gravitational acceleration).

Mass Of Entire Milky Way GalaxyThe fundamental architecture of our galaxy containing globular star clusters | Credit: NASA, ESA

Hubble measures the far distant, faint stars, whereas Gaia focuses on close stars to generate an accurate 3D map of celestial objects throughout the Milky Way and trace their movements.

In this study, researchers analyzed Hubble measurements for 12 globular clusters across 130,000 light-years, and Gaia measurements for 34 clusters across 65,000 light-years. They then combined these observations as anchor points to precisely calculate the mass of the Milky Way across 1,000,000 light-years from Earth.

Some of the earliest stars in our galaxy are 13 billion years old: they were formed a few hundred years after the Big Bang, when Milky Way had no spiral disk. Since clusters of such stars are at great distances, they can help researchers precisely measure the amount of dark matter surrounding the Milky Way far beyond the spiral disk of stars.

Read: Milky Way Merged With Another Galaxy Instead Of Forming Alone

The findings would help astronomers put galaxy into a cosmological context in a more precise manner and compare it to other galaxies in the evolving universe, as well as answer plenty of cosmological questions.

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