<s>
The	O
galaxy	B-Application
color	I-Application
–	I-Application
magnitude	I-Application
diagram	I-Application
shows	O
the	O
relationship	O
between	O
absolute	O
magnitude	O
(	O
a	O
measure	O
of	O
luminosity	O
)	O
and	O
mass	O
of	O
galaxies	B-Application
.	O
</s>
<s>
from	O
the	O
COMBO-17	O
survey	O
that	O
clarified	O
the	O
bimodal	O
distribution	O
of	O
red	O
and	O
blue	O
galaxies	B-Application
as	O
seen	O
in	O
analysis	O
of	O
Sloan	O
Digital	O
Sky	O
Survey	O
data	O
and	O
even	O
in	O
de	O
Vaucouleurs	O
's	O
1961	O
analyses	O
of	O
galaxy	B-Application
morphology	O
.	O
</s>
<s>
The	O
red	O
sequence	O
includes	O
most	O
red	O
galaxies	B-Application
,	O
which	O
are	O
generally	O
elliptical	O
galaxies	B-Application
.	O
</s>
<s>
The	O
blue	O
cloud	O
includes	O
most	O
blue	O
galaxies	B-Application
,	O
which	O
are	O
generally	O
spirals	O
.	O
</s>
<s>
Unlike	O
the	O
comparable	O
Hertzsprung	O
–	O
Russell	O
diagram	O
for	O
stars	O
,	O
galaxy	B-Application
properties	O
are	O
not	O
necessarily	O
completely	O
determined	O
by	O
their	O
location	O
on	O
the	O
color	O
–	O
magnitude	O
diagram	O
.	O
</s>
<s>
The	O
diagram	O
also	O
shows	O
considerable	O
evolution	B-Application
through	O
time	O
.	O
</s>
<s>
The	O
red	O
sequence	O
earlier	O
in	O
the	O
evolution	B-Application
of	O
the	O
universe	O
was	O
more	O
constant	O
in	O
color	O
across	O
magnitudes	O
and	O
the	O
blue	O
cloud	O
was	O
not	O
as	O
uniformly	O
distributed	O
but	O
showed	O
sequence	O
progression	O
.	O
</s>
<s>
New	O
research	O
suggests	O
the	O
green	O
valley	O
is	O
actually	O
composed	O
of	O
two	O
different	O
populations	O
of	O
galaxies	B-Application
:	O
one	O
of	O
late-type	O
galaxies	B-Application
,	O
where	O
star	O
formation	O
has	O
been	O
quenched	O
due	O
to	O
their	O
gas	O
supplies	O
being	O
shut	O
off	O
followed	O
by	O
exhaustion	O
of	O
their	O
gas	O
reservoirs	O
for	O
several	O
billion	O
years	O
,	O
and	O
another	O
of	O
early-type	O
galaxies	B-Application
where	O
both	O
the	O
gas	O
supplies	O
and	O
gas	O
reservoirs	O
have	O
been	O
destroyed	O
very	O
quickly	O
,	O
likely	O
because	O
of	O
mergers	O
with	O
other	O
galaxies	B-Application
and/or	O
the	O
presence	O
of	O
an	O
active	O
galactic	O
nucleus	O
.	O
</s>
<s>
The	O
Milky	O
Way	O
and	O
the	O
Andromeda	O
Galaxy	B-Application
are	O
assumed	O
to	O
lie	O
in	O
the	O
green	O
valley	O
due	O
to	O
their	O
star	O
formation	O
slowing	O
down	O
as	O
a	O
result	O
of	O
both	O
running	O
out	O
of	O
gas	O
.	O
</s>
