I want to combine these two sketches together so the file called stars sits behind all the objects but on the background on the file called in space- how would i do this?

Stars:
void setup(){
 size(900,900);
 smooth();
 noLoop();
}
void draw(){
 background(0);
 for (int i=50; i<500; i++){
   drawX(int((#FCFF58)),int(random(10)),int(random(width))
   ,int(random(height)),10);
 }
}
void drawX(int gray, int weight, int x, int y, int dsize){
  stroke(gray);
  strokeWeight(weight);
  line(x,y,x+dsize,y+dsize);
  line(x+dsize,y,x,y+dsize);
 
}

In Space
float y=0.0;
PImage img;
PImage b;

void setup(){ size(900,800);
 img=loadImage("flag2.png");
  b=loadImage("Spaceship3.png");
 smooth ();
 
}

void draw () {
 background(0);
   background(0);

 
 fill(#FA2014);//planet

noStroke();
ellipse(y, 45, 100, 100);
noFill();

fill(#1242FA);
noStroke();
ellipse(y,200,170,170);
noFill();
 y=y+ 1;
// if (y>900)//y>height
//   y=0.0;
if (y>900){
  y=90;

 }

fill(255);//moon
noStroke();
ellipse(450,900,1000,900);
noFill();

 image(img,100,450,80,150);//Flag
 println(img.width);// prints the image width
 
  image(b,520,40,170,130);//spaceship
 println(b.width);// prints the image width

fill(#793937);
stroke(#793937);
strokeWeight(12);//ears
point(440,210); //top point
point(450,240); //left point
point(430,240); //right corner
point(440,270); //bottom point

line(440,210,450,240);//ears
line(440,210,430,240);
line(430,240,440,270);
line(450,240,440,270);

point(480,210); // ears-top point
point(470,240); //left point
point(490,240); //right corner
point(480,270); //bottom point

line(480,210,470,240);//ears
line(480,210,490,240);
line(490,240,480,270);
line(470,240,480,270);
noStroke();

rect(470,475,30,40); //legs
rect(420,475,30,40); //legs

noStroke();
fill(#793937);
stroke(#793937);
strokeWeight(10);
ellipse(460,300,73,80); //head
ellipse(460,415,109,150); //body
noFill();


fill(#672A2A);
ellipse(460,415,95,110); //inner body
noFill();
fill(#793937);
stroke(0);
strokeWeight(1);
arc(475, 311, 30, 30, PI/2, PI);//mouth
arc(445, 311, 30, 30, 0, PI/2);//mouth
noFill();


fill(#0A0000);
ellipse(445,290,10,7); //left eye
ellipse(480,290,10,7); //right eye

noFill();

fill(200);
ellipse(445,290,4,4); //left eye
ellipse(480,290,4,4); //right eye
noFill();

fill(255);
point(460,310); //middle of nose
point(400,310); //left top point
point(400,320); //left middle point
point(400,330); //left bottom point
stroke(255);
line(460,310,400,310);
line(460,310,400,320);
line(460,310,400,330);

point(460,310); //middle of nose
point(523,310); //left top point
point(523,320); //left middle point
point(523,330); //left bottom point

line(460,310,523,310);
line(460,310,523,320);
line(460,310,523,330);

fill(0);
noStroke();
ellipse(460,310,9,9); //nose

noFill();
noStroke();
stroke(0);
fill(255);
rect(456,322,3.5,5);//teeth
rect(461,322,3.5,5); //teeth

fill(#793937);
triangle(403,436,403,401,449,420);//arms
triangle(516,436,520,401,474,420);//arms

fill(255,100);
ellipse(460,273,177,157);

line(mouseX-5,mouseY,mouseX+5,mouseY);
line(mouseX,mouseY-5,mouseX,mouseY+5);
println("x "+mouseX+" :y "+mouseY);
}

Thanks