Suggested Searches

APOD

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

See Explanation. Moving the cursor over the image will bring up an annotated version. Clicking on the image will bring up the highest resolution version available.See Explanation. Moving the cursor over the image will bring up an annotated version. Clicking on the image will bring up the highest resolution version available.

Equinox: Analemma over the Callanish Stones

Explanation: Does the Sun return to the same spot on the sky every day at the same time? No. A more visual answer to that question is an analemma , a composite image taken from the same spot at the same time over the course of a year. The featured analemma was composed from images taken every few days at noon near the village of Callanish in the Outer Hebrides in Scotland , UK . In the foreground are the Callanish Stones , a stone circle built around 2700 BC during humanity's Bronze Age . It is not known if the placement of the Callanish Stones has or had astronomical significance. The ultimate causes for the figure-8 shape of this and all analemmas are the tilt of the Earth axis and the ellipticity of the Earth's orbit around the Sun . At the solstice s, the Sun will appear at the top or bottom of an analemma. Equinox es, however, correspond to analemma middle points -- not the intersection point. Today at 1:54 am ( UT ) is the equinox (“equal night”), when day and night are equal over all of planet Earth. Many cultures celebrate a change of season at an equinox .

Date September 23, 2018
Credit Image Credit & Copyright: Giuseppe Petricca
Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
A service of: ASD at NASA / GSFC,
NASA Science Activation & Michigan Tech. U.