You might have the best results moving the stars with events - ie. using sin/cos to work out the position. I can't remember the exact math.
Still, you could probably fake it fairly well by
1) use Set Width/Set Height, and enter a formula involving the distance to the center eg. 0.1 * distance(.X, .Y, 320, 240) (assuming 320, 240 is the centre point where the star comes from). This means the width and height would increase by 1 pixel every 10 pixels it moved, for example.
2) again it's probably not the correct formula for true 3D movement, but you could try Always - set speed to current speed + 100 * TimeDelta
, or something. The speed will then increase by 100 pixels per second every second.