604 in M33
were the colors assigned in this image?
This image of NGC 604 was taken in several different
wide-band (W) and narrow-band (N) filters with the
Wide Field Planetary Camera
2 onboard Hubble. Ten filters were used in conjunction
to create this Hubble Heritage color composite.
The key on the image at right shows the relative
color assignments of the seven narrow-band and three
How does NGC 604 compare with other nearby star-forming
NGC 604 contains more than 200 hot, bright stars
within a cloud that is nearly 1,300 light-years
across. By contrast, the Orion Nebula contains just
four bright central stars and is 100 times smaller
than NGC 604. Within our Local Group, only the Tarantula
Nebula in the Large Magellanic Cloud exceeds NGC
604 in the number of young stars even though the
Tarantula Nebula is slightly smaller in size.
What does the image look like
if only some of the filters are used?
With 10 different filters, there
are many permutations on what the image may
look like if only a few of the filters are
used to produce a color image. The Original
Images page shows what each individual
filter looks like. A press release image of
NGC 604 was released in 1996 (STScI
PRC96-27) which included only a few of
the narrow-band filters.
NGC 604 in
H. Yang (U. Illinois) and NASA
How was the central cavity in
NGC 604 created?
Most of the brightest and hottest
stars form a loose cluster located within a cavity
near the center of the nebula. Stellar winds from
these hot blue stars, along with supernova explosions,
are responsible for carving out the hole at the
center. The bright stars in NGC 604 are extremely
young by astronomical standards, having formed a
mere 3 million years ago.
How hot are the bright blue stars
in the center of NGC 604?
The most massive stars in NGC 604
exceed 120 times the mass of our Sun, and their
surface temperatures are as hot as 72,000 degrees
Fahrenheit (40,000 Kelvin). Ultraviolet radiation
floods out from these hot stars, making the surrounding
nebular gas fluoresce.
image of NGC 604 (left) and its
host galaxy, M33 (right).
Visit the NOAO
website for larger images.
T.A. Rector (NRAO/AUI/NSF and
Where is NGC 604 located?
NGC 604 lies in a spiral arm of the
nearby galaxy M33, located about 2.7
million light-years away in the direction
of the constellation Triangulum. M33,
a member of the Local Group of galaxies
that also includes the Milky Way and
the Andromeda Galaxy, can be seen easily
with binoculars. NGC 604 itself can
be seen with a small telescope, and
was first noted by the English astronomer
William Herschel in 1784.