Some of the stars in the universe are members of binary
star systems. My sources give different percentages, but there are
enough of them so that you could plan for a binary star system for your
worlds.
Binary stars travel
with a partner, another star that is linked to them by gravity.
The stars do not orbit around
each other. They orbit around their
common center of mass.
The
center of
mass is where the fulcrum would be if the stars were balanced on a seesaw.
This is how it
works with people.
The weight is the same and the distance
is the same on each side.
The board is horizontal because . .
the weights and the distances are the same on both sides of the Center
of Balance.
Now let's do it
with stars. Here is a pair of binary
stars:
Each star
has about the same mass as our sun.
The
center of mass is where the fulcrum would be
if this were a seesaw.
Notice that we are talking about mass
here.
Mass is about how much matter there is.
Check the page on Weight, Mass
and Density to see how weight and mass are related.
The important idea here is that if the mass is the same and the
distance is the same on both sides of the center of mass, this system is
stable and will work.
So . . .
What happens if the masses are not the same?
Let's look at the seesaw again.
Here is a mom with a little child.
The seesaw will not work if the fulcrum is in the middle.
See where the Center of Balance is.
weight * distance = weight * distance
Again, this works for stars and also for twin
planets.
This system has a large star and a tiny star,
but it is balanced.
Here is another stable relationship.
mass * distance = mass * distance
4 * 2 = 1 * 8
What happens if a distance changes?
mass * distance = mass * distance
4 * 1 = 1 * 4
So long as the numbers are equal on both
sides, the stars may be near each other or distant from one another.
Go on here to
see possible orbits for these stars.
