Let's say you want to see if another star goes through a starspot cycle like our Sun goes through a sunspot cycle. To be sure it is cyclic activity, you should watch the star for two cycles. If the other star's cycles last as long as our Sun's sunspot cycle, how long should you study the star?
about 22 years

Which sequence of transformations on preimage ∆abc will not produce the image ∆a'b'c'? a. reflection across the line y = x b. rotation 180° clockwise about the origin followed by a reflection across the line y = -x c. reflection across the x-axis followed by a reflection across the y-axis d. reflection across the line y = -x followed by a rotation 180° counterclockwise about the origin e. reflection across the y-axis followed by a rotation 90° clockwise about the origin

Select the word from the list that best fits the definition of branch of islam that is in iran

8. is a technique that uses the images from several telescopes to produce a single image. a. reflection b. interferometry c. radiation d. refraction