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.

December 27, 1996

HET: The New Largest Optical Telescope
Credit: UT Austin, PSU, Stanford, GAUG, & LMUM

Explanation: Most of our universe is too dim to see. To peer into our cosmos' unknown depths, astronomers must deploy new tools - and the classic new tool is a larger telescope. Pictured above is the new Hobby-Eberly Telescope (HET) which recently declared "first light" in western Texas. HET currently has the largest single mirror of any optical telescope -- 11 metres in diameter. Telescopes in space, like the Hubble Space Telescope, are much smaller but avoid the Earth's atmosphere blurring out fine detail. HET's huge size, on the other hand, allows it to see very dim objects and determine their spectrum. HET's unusual design allows the primary mirror to stay put during an observation! Only smaller focusing instruments suspending above the primary move to track an astronomical object.

Tomorrow's picture: CG4: A Ruptured Cometary Globule

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
A service of: LHEA at NASA/ GSFC
&: Michigan Tech. U.