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.

2007 September 23
See Explanation.  Clicking on the picture will download
 the highest resolution version available.

The Equal Night
Credit: STS-68 Crew, NASA

Explanation: Today, the Sun crosses the celestial equator heading south at 0951 UT. Known as the equinox, the astronomical event marks the first day of autumn in the northern hemisphere and spring in the south. Equinox means equal night and with the Sun on the celestial equator, Earth dwellers will experience nearly 12 hours of daylight and 12 hours of darkness. Of course, for those in the south, the days will grow longer with the Sun marching higher in the sky as summer approaches. A few weeks after the September Equinox of 1994, the Crew of the shuttle orbiter Endeavor recorded this image of the Sun poised above the Earth's limb. Glare illuminates Endeavor's vertical tail (pointing toward the Earth) along with radar equipment in the payload bay.

Tomorrow's picture: youngs suns


< | Archive | Index | Search | Calendar | Glossary | Education | About APOD | Discuss | >

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC
& Michigan Tech. U.