A New Perspective on the Milky Way's Mass and Size
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Chapter 1: Understanding the Milky Way's Size
The Milky Way galaxy is undoubtedly vast, yet determining its precise scale has remained a challenge. Previous assessments estimated its total mass between 500 billion and 3 trillion solar masses, largely due to the elusive nature of dark matter, which constitutes the majority of the galaxy's mass. A team from the European Southern Observatory (ESO) has successfully measured the Milky Way's mass, including the dark matter component, concluding it weighs approximately 1.5 trillion solar masses.
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Section 1.1: The Challenge of Measuring Mass
Scientists have long struggled to quantify the mass of the Milky Way because dark matter may represent up to 85 percent of all matter within it. This mysterious substance does not interact with light or other forms of electromagnetic radiation, making it undetectable by conventional means. Nevertheless, its presence is inferred from its gravitational effects on visible matter. For instance, without the hidden mass of dark matter, calculations indicate that galaxies would disintegrate instead of maintaining their rotational structure.
Subsection 1.1.1: Innovative Measurement Techniques
The ESO research team devised an innovative method to estimate the Milky Way's mass without directly observing dark matter. Utilizing NASA's Hubble Space Telescope in conjunction with Europe’s Gaia spacecraft, they investigated the motion of globular clusters that orbit the Milky Way. These clusters, while part of the galaxy, also have their own independent orbits. The team analyzed 46 globular clusters—34 observed by Gaia and 12 by Hubble—with the furthest located approximately 129,000 light-years from Earth.
The velocity of these clusters correlates directly with the mass of the Milky Way (greater mass results in faster orbits), enabling the researchers to arrive at a total mass of 1.5 trillion solar masses. This figure specifically pertains to the mass contained within 129,000 light-years from the galactic center. Although the disk of the Milky Way spans about 100,000 light-years, this measurement aligns well with prior predictions.
Section 1.2: Implications of Accurate Measurements
Having a reliable estimate of the galaxy's mass is crucial for enhancing our comprehension of the universe. While the Milky Way is just one of countless galaxies, it is the one we can study with the greatest detail. Understanding the distribution and impact of dark matter is vital for elucidating how structures like the Milky Way—and even more distant galaxies—formed over cosmic time. This knowledge serves as a critical piece in the grand puzzle of the universe.
Chapter 2: The Milky Way's Mass in Context
The first video titled "Our Galaxy May Be 10 Times Bigger Than We Thought" explores the potential vastness of the Milky Way, suggesting it may be much larger than previously estimated.
The second video titled "How much does the Milky Way weigh? - New result from Hubble and Gaia" discusses recent findings regarding the galaxy's mass, shedding light on its overall structure and dynamics.