Diffraction Spikes: When Stars Look Like Crosses
Explanation:
Unusual appendages around bright stars are commonplace,
but never seem to be mentioned. What are they?
First, a
telescope brings starlight falling over a
large area to a small area.
To get at this small area, however,
one must go inside a
reflecting telescope,
and one good way to do this is to use support rods,
which are right in the view of the
telescope.
The
wave nature of light causes it to
deflect when passing near these rods.
Light scatters away from the original destination
point ending up elsewhere and appearing as
"
diffraction spikes."
These annoying spikes steal precious light
from the central image and hide light from fainter, more interesting stars.
Above, astronomers are more interested in the
half-circled point near the image center, than the cool-looking
diffraction spikes from the bright star at the bottom.
Apparently, that
half-circle
is a new stellar system forming in the
Lagoon Nebula.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings,
and Disclaimers
NASA Official: Jay Norris.
Specific
rights apply.
A service of:
LHEA at
NASA /
GSFC
& Michigan Tech. U.
