November 20, 2012

Milky Way is destined for head-on collision with Andromeda Galaxy

Astronomers announced they can now predict with certainty the next major cosmic event to affect our Galaxy, Sun, and Solar System: the titanic collision of our Milky Way Galaxy with the neighboring Andromeda Galaxy

milky way collision with andromeda

The Milky Way is destined to get a major makeover during the encounter, which is predicted to happen four billion years from now. It is likely the Sun will be flung into a new region of our Galaxy, but our Earth and Solar System are in no danger of being destroyed.

The solution came through painstaking NASA Hubble Space Telescope measurements of the motion of Andromeda, which also is known as M31. The galaxy is now 2.5 million light-years away, but it is inexorably falling toward the Milky Way under the mutual pull of gravity between the two galaxies and the invisible dark matter that surrounds them both.

andromeda milky way collision

The scenario is like a baseball batter watching an oncoming fastball. Although Andromeda is approaching us more than two thousand times faster, it will take four billion years before the strike.

milky way galaxy collision with andromeda

Computer simulations derived from Hubble's data show that it will take an additional two billion years after the encounter for the interacting galaxies to completely merge under the tug of gravity and reshape into a single elliptical galaxy similar to the kind commonly seen in the local Universe

andromeda galaxy milky way collision

Although the galaxies will plow into each other, stars inside each galaxy are so far apart that they will not collide with other stars during the encounter. However, the stars will be thrown into different orbits around the new galactic center. Simulations show that our solar system will probably be tossed much farther from the galactic core than it is today.

milky way collision with andromeda galaxy

To make matters more complicated, M31's small companion, the Triangulum galaxy, M33, will join in the collision and perhaps later merge with the M31/Milky Way pair. There is a small chance that M33 will hit the Milky Way first.

andromeda milky way galaxy collision

The universe is expanding and accelerating, and collisions between galaxies in close proximity to each other still happen because they are bound by the gravity of the dark matter surrounding them. The Hubble Space Telescope's deep views of the universe show such encounters between galaxies were more common in the past when the universe was smaller.

milky way galaxy collision with andromeda galaxy

A century ago astronomers did not realize that M31 was a separate galaxy far beyond the stars of the Milky Way. Edwin Hubble measured its vast distance by uncovering a variable star that served as a "milepost marker."

Edwin Hubble went on to discover the expanding universe where galaxies are rushing away from us, but it has long been known that M31 is moving toward the Milky Way at about 250,000 miles per hour. That is fast enough to travel from here to the Moon in one hour. The measurement was made using the Doppler Effect, which is a change in frequency and wavelength of waves produced by a moving source relative to an observer, to measure how starlight in the galaxy has been compressed by Andromeda's motion toward us.

andromeda galaxy milky way galaxy collision

Previously, it was unknown whether the far-future encounter will be a miss, glancing blow, or head-on smashup. This depends on M31's tangential motion. Until now, astronomers have not been able to measure M31's sideways motion in the sky, despite attempts dating back more than a century. The Hubble Space Telescope team, led by van der Marel, conducted extraordinarily precise observations of the sideways motion of M31 that remove any doubt that it is destined to collide and merge with the Milky Way.

Image Credit: NASA, ESA, Z. Levay and R. van der Marel (STScI), and A. Mellinger
Explanation from:


  1. There is scenario for unfolding Universe.

  2. The vistas of cosmology

    While I bumble about the place
    I love to ponder aerospace
    I love to wonder at the stars
    Whilst sawing through my prison bars
    I’ve lived too long with shuttered mind
    Along with most of humankind
    But Science now has gifted me
    The vistas of cosmology.

    I’ve stood upon the Martian plains
    And strained to see a humble light
    A speck, a dot, a tiny mite
    The echo of my dragging chains
    Our home, our fragile biosphere
    So far away, and yet so near.

    I’ve hovered underneath the rings
    Where Saturn’s shadow gave me pause
    As if I heard some gentle strings
    That hinted at celestial cause.
    There shielded from the solar glare
    Entranced into a distant stare
    Again I saw our tiny world
    Among a million stars unfurled.

    I love that tiny, hard pressed sphere
    Where tyrants seek to domineer
    Where brutish tends to soon outsmart
    The lute strings of a gentle heart.
    But Science now has gifted me
    The vistas of cosmology.

    They say it is my place of birth
    And there I must collect my worth
    But I say with a shrug and smile
    I’ll only linger for a while.

    For I was born among the stars
    Long before the prison bars
    My very atoms forged with ease
    In massive stellar factories.

    My father is the Universe
    Astronomy my patient nurse
    I have no fear of what’s unsure
    For I have searched, and felt its cure.

    A Cosmic Kindness, hidden well
    Enchants me with its ancient spell.
    I love to wonder at the stars
    Whilst sawing through my prison bars.

  3. I think my order for an umbrella from Amazon will come in time :) Seriously it will be beautiful indeed!