Every wonder just how big the Milky Way galaxy really is? In the late 1920s, astronomers thought all of the stars in the universe were contained inside of the Milky Way. It wasn’t until Edwin Hubble discovered a special star known as a Cepheid variable, which allowed him to precisely measure distances, that astronomers realized that the fuzzy patches once classified as nebula were actually separate galaxies (Redd, 2013).

This very wide-field view of the Milky Way shows the extent of the new VISTA infrared image of the centre of the galaxy. These data cover the region known as the bulge of the galaxy and have been used to study a much larger number of individual stars in the central parts of the Milky Way than ever before. The region covered by the new VISTA mosaic is shown as a rectangle.

How Big Is Our Galaxy?

NASA estimates the galaxy at 100,000 light-years across. Since one light year is about 9.5 x 10¹²km, so the diameter of the Milky Way galaxy is about 9.5 x 10¹⁷ km in diameter. The thickness of the galaxy ranges depending on how close you are to the center, but it’s tens of thousands of light-years across. Since the galaxy is estimated to 100,000 light-yeas (1 billion M☉) according to NASA scientist, we measure other galaxies as it compares to the size of ours. Our nearest neighbor galaxy called M31 or Andromeda Galaxy is slightly larger at 1.23 T M☉or 1,23 billion M☉.

Our galaxy is part of a collection known as the Local Group. Because some of these galaxies are prominent in our sky, the names tend to be familiar. The Milky Way is on a collision course with the most massive member of the group, M31 or the Andromeda Galaxy . The Milky Way is the second-largest member, with M33 (the Triangulum Galaxy) the third-largest, NASA says. Andromeda appears much brighter in the night sky due to its size and relatively closer distance. There are about 30 members of this group (Howell, 2015).

Made From Other Galaxies

The Milky Way wasn’t always as it is today – a beautiful, warped spiral. It became its current size and shape by eating up other galaxies, and is still doing so today. In fact, the Canis Major Dwarf Galaxy is the closest galaxy to the Milky Way because its stars are currently being added to the Milky Way’s disk. And our galaxy has consumed others in its long history, such as the Sagittarius Dwarf Galaxy (Williams, 2016).

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References

Redd, N. T. (2013). Milky Way Galaxy: Facts About Our Galactic Home. Retrieved from: http://www.space.com/19915-milky-way-galaxy.html

Howell, E. (2015). How Big is the Milky Way? Retrieved from: http://www.universetoday.com/75691/how-big-is-the-milky-way/

Williams, M. (2016). 10 Interesting Facts About the Milky Way. Retrieved from: http://www.universetoday.com/22285/facts-about-the-milky-way/