W5: Pillars of Star Formation
How do stars form?
Images of the star forming region W5
like those in the
infrared by NASA's Wide Field Infrared Survey Explorer
(WISE, later
NEOWISE) satellite
provide clear clues with indications that
massive stars near the center of empty cavities
are older than stars near the edges.
A likely reason for this is that the older stars in the center are actually
triggering
the formation of the younger edge stars.
The triggered
star formation
occurs when hot outflowing gas compresses cooler gas into
knots dense
enough to gravitationally contract into stars.
In the featured
scientifically colored infrared image,
spectacular pillars
left slowly evaporating from the hot outflowing gas
provide further visual clues.
W5 is also known as
Westerhout 5 (W5) and IC 1848.
Together with IC 1805, the nebulas
form a complex region of star formation popularly dubbed the
Heart
and Soul Nebulas.
The featured image
highlights a part of W5 spanning about 2,000 light years
that is rich in
star forming pillars.
W5 lies about 6,500 light years away toward the
constellation of Cassiopeia.