Expert: Tom Whiting - 6/6/2006

Question
Dear Sir,

I am an amateur researcher now day researching the subject of solar flares, what I want to know is this that do the solar flares also carry some form of shock waves and what is their effect on the earth's surface as we know that the solar flare are caused by the nuclear explosions on sun which definately produce shock waves.

Another question that I want to ask is that as we know that sun it self has a perminant position in the milky way and is moving in a particular direction.

What I want to know is this that is it keeping its position because of some gravitational pull from the centre of the galaxy probably by some black hole and if its the gravitational pull by the black hole what is its effect on the earth and moon. can we some how detect this gravitation pull.

Kindly explain.

Thanks & Best regards

Asim

Answer
Hi Asim,
I am not an expert on solar astronomy, but I can cover your
other questions.
However, I do know that the sun emits solar flares in a three
dimensional volume, so the odds that a solar flare is directed
right toward the Earth, are small.  But it does happen, on occasion, that one is directed our way.  The shock waves you speak of are generally in the form of high energy particles that, about 48 hours after the CME  (coronal mass ejection) occurs, the Earth experiences a very nice Aurora (Northern Lights) display, and some electrical networks can suffer blackouts from the surge of electricity caused by the mass ejection.  Fortunately, the ionosphere and the rest of our atmosphere, protects life on the planet from the harmful effects of those high energy ionized particles, by directing
those charged particles to the magnetic poles of the Earth.
(Obviously they are not life threatening...life has been around
for over 3 billion years on this planet, and we're still doing fine).

Yes, the sun is orbiting the center of the galaxy in a particular
orbit,  so no,  we have no permanent "at rest" position.
(there is no such thing as "absolute" rest in our Universe...
everything is moving,  relative to everything else).

Currently the direction of the Solar System is toward the
star Vega in the northern sky, or a point just west of Vega
toward the Hercules side...it's called The "Sun's Way"....
we know this because all the stars in this region are
diverging from each other, whereas on the other side of the
sky we see stars slowly converging at the other end.
So that's the direction we, the sun and Solar System, are
heading around the center of the galaxy (located on the
Sagittarius/Scorpius border)...one orbit taking
about 250 million years, or thereabouts.
And yes, we, the Solar System,  roughly maintain an orbital distance of some 30,000 light-years from the center of the Milky Way Galaxy.

And yes, you are correct...we maintain that distance from
the center of the Galaxy because of gravity of the mass of
stars (and perhaps a giant black hole) near the center of
the Galaxy.....as does all the other outer stars (basically our
neighbors)  in the Milky Way.  We are located in the Orion Arm, the next to last arm out, only the Perseus Arm is more distant, and the last arm out.  

We "detect" the gravitational pull of the center of the galaxy
by inference....since, in 4.6 billion years we have not departed
(escaped) from the Milky Way Galaxy....and none of our
stellar neighbors have escaped either), then obviously
the gravity of the Milky Way Galaxy is doing a fine job
keeping the Sun and it's solar system well confined to
our orbital position around the Galaxy.  We have made at least 18 trips around the Milky Way in our 4.6+billion year existence.  In fact, it's rare to find a star...any star...that has achieved escape velocity from the Milky Way...I believe there are only 3 or 4 known stars that are on there way out of the Milky Way; not very many considering that the Galaxy contains approximately 200 billion stars.

The actual gravity of the Galaxy does not affect the Earth-moon system to any great extent- I doubt that it could be measured...it affects the more massive sun.....and we in turn, are locked into the gravitational well of the sun....so where the sun goes, so we go....as that is our strongest gravitational pull...as it is for all the solar system objects.

 If the sun ever left the Milky Way, we would just follow along with the sun for the ride...in fact, as long as we are gravitationally tied to the sun, it doesn't matter where we go thru space.


Hope all this helps,
Clear Skies,
Tom Whiting
Erie, PA


FOLLOW UP:
Oh, a very good website which may help in your research
of the Milky way and the Sun's path is given at
http://en.wikipedia.org/wiki/Milky_Way

Hope this helps,
Tom W.