Orbits in a gravitational field

Initialize the position, velocity and acceleration vectors for the Earth

Clear["Global`*"]
r[0]={1.496 (10^11),0};
v[0]={0,(Sqrt[((G M)/(1.496 (10^11)))])};
G=(6.6726/(10^11));M=1.991 (10^30);
h=21600;
v[1]:=v[0]+(1/2) h a[0];

Define the position, velocity and acceleration vectors for the Earth

a[n_]:=-(((G M) {r[n][[1]],r[n][[2]]})/(((r[n].r[n]))^(3/2)))
v[n_]:=v[n]=v[n-1]+h a[n-1]
r[n_]:=r[n]=r[n-1]+h v[n]

Now, plot the x-y coordinates

ListPlot[Table[r[n],{n,0,1461,21}],AspectRatio->Automatic,AxesLabel->{"x","y"}]