THE ANDROMEDA GALAXY IS SLIGHTLY LESS MASSIVE THAN THE MILKY WAY

A new technique for measuring the mass of galaxies has been applied to our closest galactic neighbour - and it has found that the Andromeda galaxy is roughly the same size as the Milky Way, and not two to three times bigger as was previously thought.

The new measurement was obtained by a technique that calculates the speed required to escape the gravitational pull of a galaxy, or escape velocity. 

The escape velocity for Andromeda is about 470 (+- 40) km/s while our galaxy, the Milky Way has an escape velocity of about 550km/s. Ths puts the mass of Andromeda at 1.2 trillion solar mass versus the Milky Way's 1.5-2 trillion suns. 

This research is lead astrophysicist Prajwal Kafle from the International Centre for Radio Astronomy Research together with his team. 

While giving to the fact that it is hard to measure the parameters of our galaxy as we are inside it, improvements in our measurements will continue to revise the parameters of both Andromeda and Milky Way in the future. 

Source: Science Alert https://www.sciencealert.com/andromeda-galaxy-much-smaller-than-thought-same-size-milky-way

A 2018 research suggests that our galaxy is double in extension than the conventional 100,000 light years. 

Recent research has doubled the Milky Way's span to perhaps 200,000 light-years, showing that while the population of stars grows less dense in our galaxy's outer rim, a gauzy scattering stretches well past what scientists had previously observed.

Researchers made the find after analyzing the abundances of metals (heavy elements) in stars, also known as their metallicities using the survey data from the Apache Point Observatory Galactic Evolution Experiment (APOGEE) and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), which collect the spectra of stars. A star's spectrum is the breakdown of its light into different colors. By analyzing the pattern of colors, scientists learn what elements are present within the star.

They found out that stars at 30KPC (kiloparsec) (100,000 light years) from the galactic center has the same metal content as stars found at the disk. Although this data for our galaxy disk has been revised, scientists still believe that our galaxy contains roughly 400 billion stars with countless planets, dust, comets and other objects. 

Source: Space.com https://www.space.com/41047-milky-way-galaxy-size-bigger-than-thought.html