There really won't be a big bang!
Throughout the year, during most of our public and private programs, we manage to view M31, the Andromeda Galaxy, at the Oregon Observatory. The staff member manning the telescope viewing our neighboring galaxy explains something like: “the M31 galaxy or Andromeda galaxy is our closest visible neighboring galaxy. Andromeda is about two and a half million light years away and is approaching our Milky Way at about 250,000 miles per hour. The two galaxies are due to collide in about 5 billion years.” Sometimes the staff member may go on and explain more or answer questions about this fact. The guest makes appropriate astonished remarks and moves on to another object.
The brief discussion with our visitors is actually echoing the barest minimum of a very complex and fascinating phenomenon that is being studied carefully and intensively by astronomers the world over.
NASA’s official online home to the Hubble Space Telescope is called HubbleSite. Recently, HubbleSite published a detailed description of the pending collision between the Milky Way and the Andromeda galaxy. According to the article: “NASA 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…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.”
NASA also produced what is considered an accurate depiction of what the collision event will look like using “painstaking Hubble Space Telescope measurements of the motion of Andromeda.” Computer simulations of Hubble data show that the collision will begin in about four billion years with an additional two billion years before the two galaxies will totally merge.
“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.”
HubbleSite has produced a video that includes an animated simulation of the collision between the Milky Way and Andromeda. The photos graphically show us what it is likely to look like from the vantage point of earth.
“This illustration sequence depicts the collision of the Milky Way (right) and Andromeda galaxies and shows the predicted merger between our Milky Way galaxy and the neighboring Andromeda galaxy.”
First Row, Left: Present day.
First Row, Right: In 2 billion years the disk of the approaching Andromeda galaxy is noticeably larger.
Second Row, Left: In 3.75 billion years Andromeda fills the field of view.
Second Row, Right: In 3.85 billion years the sky is ablaze with new star formation.
Third Row, Left: In 3.9 billion years, star formation continues.
Third Row, Right: In 4 billion years Andromeda is tidally stretched and the Milky Way becomes warped.
Fourth Row, Left: In 5.1 billion years the cores of the Milky Way and Andromeda appear as a pair of bright lobes.
Fourth Row, Right: In 7 billion years the merged galaxies form a huge elliptical galaxy, its bright core dominating the nighttime sky.
(Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas, and A. Mellinger)
More information on this and much more Hubble Space Telescope news and photos may be found at the HubbleSite.org. The animated version of the pictured sequence may be found at this link: http://hubblesite.org/news/2012/20 .