\documentclass[border=2pt]{standalone}

% Drawing
\usepackage{tikz}

% Tikz Library
\usetikzlibrary{calc, quotes, angles}

% Notation
\usepackage{physics, bm}

\begin{document}

	%Macros
	\pgfmathsetmacro{\r}{0.8}	
	\pgfmathsetmacro{\Phi}{40}
	\pgfmathsetmacro{\Theta}{60}
	
	\begin{tikzpicture}
		%Grid
%		\draw[thin, dotted] (0,0) grid (8,8);
%		\foreach \i in {1,...,8}
%		{
%			\node at (\i,-2ex) {\i};	
%		}
%		\foreach \i in {1,...,8}
%		{
%			\node at (-2ex,\i) {\i};	
%		}
%		\node at (-2ex,-2ex) {0};
		
		% Coordinates
		\coordinate (earth) at (1,2);
		\coordinate (moon) at (8,1);
		\coordinate (earth-point1) at ({\r*cos(\Theta)+1},{\r*sin(\Theta)+2});
		\coordinate (A) at (2.5,3.5);
		\coordinate (B) at (6.5,2.5);
		
		% Earth
		\draw[thick, fill=blue, draw=blue] (earth) circle (\r);
		% Text
		\node (a) at (A) {Earth};
		
		% Moon
		\node[circle, inner sep=1.5pt, outer sep=2pt, fill=black!30] (MOON) at (moon) {};
		% Text 
		\node[below, shift={(0,-0.1)}] at (MOON) {$m$};
		\node (b) at (B) {Moon};
		
		% Lines
		\draw[-latex] (earth) -- (MOON) node[pos=.55, below left] {$\vb{r}_o$};
		\draw[-latex] (earth) -- (earth-point1) node [pos=0.6, left] {$\vb{r}$};
		\draw[-stealth] (a) to[bend left=30] ({\r*cos(\Phi)+1},{\r*sin(\Phi)+2});
		\draw[-stealth] (b) to[bend left=30] (MOON);
		\draw[dashed, -latex, black] (earth) -- (MOON) -- ($(earth)!1.3!(moon)$) node [above, shift={(-0.1,0.1)}] {$z$};
		
		% Angles
		\pic[draw, "$\theta$", angle eccentricity=2.5, angle radius=5pt] {angle = moon--earth--earth-point1};
		
		% Point
		\draw[fill=black] (earth) circle (1pt) node[below, shift={(0,-0.1)}] {$\mathrm{O}$};
	\end{tikzpicture}
	
\end{document}