How does the Milky Way compare to the Andromeda Galaxy?



  1. 0 Votes
    Milky Way
    (The Milky Way)

    Hopefully, you know that right now you’re a resident of the planet Earth. Earth belongs to a formation of planets that we call the Solar System (Solar, as the involved planets revolve around a star that we call the Sun). In turn, the Solar System is a member of a larger group of planets known as the Milky Way Galaxy. 
    What group, however, is the Milky Way a member of? The answer is the “Local Group”, which comprises about thirty galaxies in total. It has a diameter of ten million… not miles, but light-years. That is truly a massive distance.
    In this article, I’ll be comparing and contrasting the Milky Way with its “sibling” within the Local Group. This is the Andromeda Galaxy, which is the closest galaxy to the Milky Way. 
    Naming and Size
    Different cultures have their own different beliefs for how the Milky Way came to be. They also have their own names for the galaxy. As for the English version, the name “Milky Way” comes from Ancient Greek: the Greek Galaxias, which is the origin for the word “galaxy”, is a derivation of the Greek word for “milk”: gala. One particular Greek myth had the “queen goddess”, Hera, nursing one of her sons, Hercules. During the milking, milk leaked from Hera’s breast, spilling into the sky and creating the Milky Way.  
    The Andromeda Galaxy is named after the constellation Andromeda, of which it is a member. Again, the tales of the Greek serve as precedent; in Greek mythology, Andromeda was a princess who was chained to a rock and left for a vicious sea beast named Cetus. She was eventually saved by the hero Perseus. 
    The Milky Way’s disk has a diameter of 100,000 light years and a thickness of 1,000 light years. In a drastic increase from previous estimates, it is now believed to have a total mass of about three trillion solar masses – that is, three trillion suns. 
    As a spiral galaxy, the Andromeda Galaxy is oblong and has two angular diameters, both measured in “arcminutes”. Its major diameter is 190 arcminutes; its minor diameter is 60 arcminutes. Its mass has been estimated to be about 1.2 billion solar masses; again, this translates to a mass about 1.2 billion as large as that of the Sun. 
    As galaxies both, the Milky Way and Andromeda Galaxy are each composed of billions of stars. According to NASA, the Milky Way contains about one hundred billion stars, while other more liberal estimates place the number at 200-400 billion. This may seem whopping, but the Andromeda Galaxy is even more impressive! The Andromeda Galaxy has around a trillion stars – multiple times as many as the Milky Way.
    Structurally, the two galaxies are similar. Each are “spiral galaxies”. This means that they have “galactic discs” at their centers, and numerous “spiral arms” extend outwards from those centerpieces. All of this is surrounded by a faint layer of old stars and other stellar material; this is known as the “halo”.
    Relevant Distances and Positions

    It is likely of some interest to you where exactly our Solar System lies within the Milky Way. The Solar System is located inside of one of the smaller “spiral arms”, one called the Orion Arm. It is about 27,000 light years from the center of the Milky Way. As such, it takes a tremendously long time – 225-250 million years! – for the Solar System to orbit around the galactic center (as Earth would orbit around the Sun). This period of time is known as a “cosmic year”. For reference, it is believed that in the period of time since humans evolved from primates, the Solar System has only gone through 1/1250 of a cosmic year.
    The Andromeda Galaxy is about two-and-a-half million light years away; interestingly, however, it is steadily moving closer to the Milky Way. This has led to a prediction that the Milky Way and the Andromeda Galaxy will eventually collide. Like the cosmic year, though, the time scale of this proposed collision is massive. According to the New Scientist, this collision won’t happen for another five billion years! Then, the Milky Way and the Andromeda Galaxy will become one elliptical galaxy – what one scientist calls “Milkomeda”. And this article will surely be out of date!
    Andromeda Galaxy

    (The Andromeda Galaxy) 

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    The Milky Way and Andromeda galaxies are both spiral galaxies, the Milky Way being confirmed as a barred spiral galaxy.  It is believed also that Andromeda Galaxy is barred but that we cannot see its bar due to the flat angle it makes with our view from Earth.

    A barred spiral galaxy (Notice the bar-shape of the center of the galaxy.):

    The Andromeda Galaxy is thought to contain around one trillion stars, compared to our galaxy’s 200-400 billion.  Astronomers estimate that it is 220,000 light-years across.  The Milky Way is roughtly 100,000 l-y across.  Both galaxies are thought to have giant black holes at their centers.  Andromeda is one of the few blue-shifted galaxies, meaning that it is actually moving toward the Sun, which could also imply that some day the Milky Way and Andromeda will collide in about 2.5 billion years.  Not much is known about what will happen, but one proposed theory is that the two may merge to become a large elliptical galaxy.   

  3. 0 Votes

    how do i supposed to know


  4. 0 Votes

    how do i supposed to know


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