Astronomers use a method called parallax to measure distances to some stars. To understand...

Astronomers use a method called parallax to measure distances to some stars. To understand this method, hold your thumb up at arm's length, close one eye, and place your thumb in front of a distant object. Then, without moving your thumb, switch eyes, and you will see your finger seems to shift with respect to the distant object behind it. The effect is called parallax. Astronomers measure parallax by very carefully measuring the position of a nearby star with respect to more distant stars behind it. Six months later when Earth is on the opposite side of its orbit, they measure those positions again. If the star is close enough, a measurable parallax will be seen. The position of the star relative to the more distant background stars will have shifted. Even

for the nearest star, the shift is very small, less than an arc-second, or (-^-)ö. companying illustration, the line of sight to the star in January is different than t July, when Earth is on the other side of its orbit. As seen from Earth, the posit the nearby star appears to sweep through the angle shown. Half of this angle parallax,). If p = 0.00021111° to the nearest star Proxi-ma Centauri, find the di! from Earth to this star if the distance from the sun to Earth is 93,000,000 miles.