Panius wrote:
This is the first time that i've heard an astronomer say this.
Most scientists still seem to believe that Andromeda will
collide with the Milky Way in about 5 billion years.
And i've been saying all along that the blue shift can only
show radial velocity, that Andromeda could be coming
in our general direction at an angle that would cause it to
miss us by a country megaparsec. That the chances of
it actually colliding with us could be slim to none.
Thanks, David, for this bit of validation. Do you know if
there are other astronomers out there who are warming
up to this view?
The only astronomers who are saying that M31 will (ie: with certainty) collide
with us are either those who are not very well versed in the subject, or those
who are trying for some headlines (I suspect the latter). The radial velocity
component of M31 (corrected for our solar-system's rotation about the
Milky-Way's galactic core) has been known for at least several decades, so
when I heard about someone trumpeting about a "collision", I said to myself,
"Its probably grant-renewal time again", as you see these sort of news
releases put forward by groups hoping to get enough publicity to justify the
continuation of funding. I saw this a few years ago when some group claimed
that the Earth had a "companion" body, when it was nothing of the sort (merely
an asteroid that happened to have an orbital period of about one year).
Indeed, the corrected value of the approach speed component is only on
the order of *100 kilometers per second*. I have seen values up to as high as
110 km per second in approach, but again, this is only the radial velocity and
not the true space velocity. M31's companion galaxy M32 has a corrected
radial velocity of 86 kilometers per second *in recession*, so obviously its
orbital motion about M31 is a significant factor in that figure. I still see
claims on the internet of outrageous velocity figures for M31, all because
some yo-yo forgot to subtract out the rotational speed component of our solar
system about the galactic core (you would think someone who is supposedly
well-versed in Astronomy would have mastered simple freshman-level vector
mechanics by now).
And how do you feel about the possibility that our Milky
Way, the Andromeda and the Triangulum are revolving
around a common CG that might even consist of a huge
mass of dark matter?
There is no evidence of this, so as far as I am concerned, its merely
speculative. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory:
http://www.hydeobservatory.info/
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