What is the angle between the equator of the sun, and the plane of the Earth's orbit
I want to know the angle between the plane that passes through the centre of sun and is perpendicular to its spin axis, and the plane that contains the orbit of earth around sun?
Is this a fixed value or it is variable over time (and if so, how does it vary) !
Wikipedia (https://en.wikipedia.org/wiki/Sun) tells us where the Sun's "north pole" points (explicitly, that it's about 7.25 degrees from the ecliptic), which I believe answers your question?
The plane that contains the orbit of the Earth is known as the "ecliptic". The rotation of the sun is tilted by 7.25 degrees to the ecliptic, and this value does not vary over time.
The rotation of the Earth is also tilted, by 23.45 degrees to the ecliptic, it is this angle that causes seasons.
An old paper Position of the Sun's axis describes how the Earth crosses the solar equator on June 4th and Dec. 6th each year.
Nasa has a factsheet, that has this and other information about our nearest star.
It must have been a very interesting experiment indeed that was used to measure the axis of rotation of the Sun. I'm just guessing that points of reference were hard to find.
You can measure the velocity of the sun's surface by the doppler effect, The parts of the sun that are rotating towards us are blue shifted. That lets you measure the velocity all around the sun, and so find the solar axis and equator.
It is an Earth-centric thing to ask (which is fine). Does Jupiter, the heaviest planet, orbit over the Sun's equator? More generally, what is the angle between the Sun's axis and the angular momentum of the entire Solar system (including planets in more or less tilted orbits)?