Is the sun currently transiting the galactic equator?

Question

I'm researching whether "galactic energy" might possibly be contributing to exponentially increasing worldwide volcanic activity (see http://www.earthchanges-bulletin.com/earthchanges/gallery/Quakes/index.htm for charts) which could possibly be a major cause of global warming, and I'm finding conflicting information:

either the sun has been crossing the galactic equator for the last 20 years or so (see reference to a book by Jean Meeus at http://www.bibliotecapleyades.net/esp_2012_03.htm),

OR

the sun is 88 light-years north of the galactic equator (see http://www.idialstars.com/tspm.htm).

Quite a difference. So which one is correct?

(Meeus gets a reference at http://helios.gsfc.nasa.gov/qa_plan.html, so apparently is the real deal.)

Answer 1

Those two sources are talking about two different things. The Meeus reference is about the position of the Sun in our sky relative to the centerline of the Milky Way. This has to do with the tilt of Earth's orbit relative to the plane of the galaxy, as well as the tilt of Earth's axis relative to its orbit. The Sun appears approximately at the galactic equator on the solstices. There is some uncertainty as to the precise position of the galactic equator, but according to the position appearing in most modern star atlases, the solstices were exactly on the line in 1999. The exact position is fuzzy, because the galaxy is not a solid object but a swarm of hundreds of billions of stars. The galactic equator represents the average plane of rotation for all those stars.

The second reference is about where our solar system is located within the galaxy. Our sun is in 226-million-year orbit around the galactic center, that takes us above and below the galactic plane. The current position of that orbit puts us 88 light years above that plane.

In summary, the first link is talking about the apparent position in the sky of the line of the galactic equator, while the second one is talking about our physical location in the galaxy. Two totally different things.

Answer 2

The best estimates these days, is that the sun is about 14 light-years above the galactic equator.

Answer 3

Jean Meeus' books are largely concerned with solar system dynamics and coordinate systems. There is the equatorial coordinate system, used to define the position of stars in the sky (right ascension and declination) which uses the earth's equator as the defining plane. Then there is the ecliptic coordinate system, based on the earth's orbital plane, mainly used to define positions of the moon and planets. There is also the galactic plane, based on the estimated centre line of the band of stars around the sky which forms the milky way galaxy. This is used (for example) to study the distribution of novae, which tend to have a small value of galactic latitude. Meeus' books give examples of coordinate transformations from one system to another and various other interesting geometrical configurations. He noticed that 26,000 year precession of the earth's axis was carrying the solstice points across the galactic equator and found that the exact date of the crossing was in 1998. Another way of looking at it was that the sun's galactic latitude was near to zero at the solstices in that year. Since then, the sun's galactic latitude at the solstices has been increasing. All that happened was an interesting geometrical configuration and no more.

Now that all of the 2012 cranks are making their appearance, the fact that the solstice on December 21st 2012 coincides with the end of the Long Count of the Mayan calendar has been added to the fact that the sun is near the galactic equator to create an "event" out of all proportion to its true significance. The cranks seem to overlook the fact that the solstice sun - galactic equator "alignment" happens every year and has become far less exact now than it was in 1998. Moreover, having no real understanding of astronomy, the cranks confuse this with the 3D model of the galaxy, with the solar system revolving round once every 225 million years and talk about the solar system crossing the central plane of the galaxy. In fact we are moving away from the central plane and won't dip down through it for another 30 million years or so. The idea that our passage through this plane can be pinned down to an exact date in 4 years time is plainly nonsense.

So your references don't conflict as long as you remember the difference between the 2D and 3D versions. The 2012 cranks have yet to understand that distinction.

Additional notes:

There isn't any increased gravitational pull at the galactic equator. There is no reason why there should be. Our distance from the galactic centre doesn't alter appreciably neither does the mass of the galaxy.

Imagine the 3D model, with the galaxy as a flattened disc of stars and the solar system rotating round it in a period of 225 million years. The solar system is actually "tipped over" at an angle of about 60 degrees as it goes round, so as the Earth orbits the Sun, sometimes we see the sun in the same direction as the plane of the galaxy, looking roughly towards the centre, then 3 months later, it is in a part of the sky which is 60 degrees away from the galactic plane. After another 3 months, the sun is back in line with the galactic plane, but this time looking away from the centre. It is this twice-yearly "lining up" of the sun with the galactic plane which people confuse with the whole solar system physically crossing the central plane as it bobs up and down in its 225 million year orbit.

As for the 1998 alignment, that was purely a function of the direction in which the earth's axis happened to be pointing. The solstices and equinoxes are directions in space, centred on the Earth. Imagine them as spokes of a wheel, slowly moving round the plane of the Earth's orbit, taking 26,000 years to complete a circuit. In 1998, one of those "spokes" (the December solstice) was pointing at the plane of the galaxy. It doesn't require the Earth to be physically in the central plane of the galaxy in order for this line to be pointing towards it.