# What Provides Two Different Vantage Points to Observe the Parallax of a Distant Star such as Cygnus X-1

## Observing Parallax of Distant Stars

**The parallax of a distant star such as Cygnus X-1 can be observed by using two different vantage points on Earth**, such as two observatories located at different locations or the same observatory observing the star at different times of the year. By measuring the apparent shift in the position of the star when observed from these vantage points, astronomers can calculate the parallax angle and determine the distance to the star.

## Explanation

**Parallax is a phenomenon used to measure the distance to nearby stars.** It occurs due to the apparent shift in the position of an object when viewed from different vantage points. To observe the parallax of a distant star like Cygnus X-1, astronomers use two different vantage points on Earth.

These vantage points can be two observatories located at different locations on Earth or the same observatory observing the star at different times of the year. By measuring the apparent shift in the position of the star when observed from these two vantage points, astronomers can calculate the parallax angle.

The parallax angle is the angle formed by the line connecting the two vantage points and the line connecting the vantage points to the star. Using trigonometry, astronomers can then determine the distance to the star.

## Example

Let's say astronomers observe Cygnus X-1 from two observatories located 1000 kilometers apart. They measure the apparent shift in the position of the star to be 1 arcsecond. Using the parallax formula, they can calculate the distance to Cygnus X-1.

## Direct Answer

**The parallax of a distant star such as Cygnus X-1 can be observed by using two different vantage points on Earth**, such as two observatories located at different locations or the same observatory observing the star at different times of the year. By measuring the apparent shift in the position of the star when observed from these vantage points, astronomers can calculate the parallax angle and determine the distance to the star.