Its 17 times heavier, We don't know how big it is from the info in the article. You say the surface gravity is 3g (I presume you got this information from another article since it isn't mentioned in your link). So this gives us the information we need to calculate its size.

If the planet were the same size as earth, its surface gravity would be 17g, so we know it must be bigger. We know the surface gravity is inversely proportional to the square of the radius, so
17/R^2 = 3.
or
R^2 = 17/3 = 5.66666...
and
R = sqrt (5.6666...) = 2.3805

So the planet is about 2.4 times the radius of earth, or 19,044 miles in diameter.