from earth stars can look very similar
to each other
just a bunch of bright twinkles of light
but if you look carefully you'll see
that the stars are a whole array of
different colors
and people have noticed this range of
colors in the stars for a long time
in the first century bc chinese
astronomers recorded the star
beetlejuice in the orion constellation
as having a white or yellowish hue but
many centuries later
in the year 150 a.d egyptian astronomer
ptolemy
noted the star's readiness or red color
which is the same color it exhibits
today
while this may seem like a simple
observation this change in color over
time
actually indicates that the star went
through a major change in its life cycle
in general noting the color of a star
can tell us so much about its age
temperature and even its chemical
composition a good place for us to begin
is by understanding what color actually
is no i promise i'm not going all
philosophical in you
i'm talking about how we characterize
the color of a star in astronomy
it's all about electromagnetic radiation
a form of energy that's all around us
this energy travels in waves and is
generally separated into seven
categories depending on the frequency
and lengths of these waves on one end of
the spectrum we have the quick bursts of
gamma rays
x-rays and ultraviolet radiation in the
middle we have a slim spectrum of
visible light
these are the colors we can actually see
and on the other end are the longer
slower wavelengths of infrared radiation
microwaves and radio waves
so the visible light we see as colors is
really only a small fraction of the
electromagnetic waves generated in the
universe
it's useful then that stars emit most of
their energy as
visible light think about turning on a
gas stove
at the bottom where it's hottest the
flame burns blue and white
and up at the top of the flame where
it's cooler it burns
yellow orange it's the same with stars
the hotter the star the more blue white
it is in color
similarly the cooler the star the more
orange or red it appears
astronomers use a sort of thermometer
for stars
though stars emit multiple colors of
wavelengths at one time
the dominant color will win out and be a
good indicator of its temperature
and it's a sliding scale too in terms of
what other types of electromagnetic
radiation
a star is giving off the energy can slip
into wavelengths that are invisible to
the naked eye
which is why it's super useful to modern
astronomers
to be able to capture different types of
electromagnetic radiation
they do this using different types of
telescopes for example
to detect the hottest most energetic
stars
or the hot glow of a stellar nursery
you'd need to filter for ultraviolet
there are other factors besides
temperature that affect a star's color
including the distance of the star from
earth and the elements it's made of
so each element within a star is
associated with a specific wavelength
by measuring the amount of energy at
those wavelengths we can tell the amount
of hydrogen
helium and other various trace elements
that are in a star
this technique is called spectroscopy
one way to see all of the individual
wavelengths is to pass a star's light
through a filter on a telescope that
takes out all the other kinds of light
the james clark maxwell telescope does
this in its own way
by selecting very specific wavelengths
to observe
it specializes in those at super low
energy
so we're looking at the reddest deeper
than the reddest red that any human
could ever see so we see things that are
cold in space or don't emit a lot of
energy
at least nearby so the two things that
we really specialize in
are the formation and birth of stars and
planets
looking at the gas and dust between the
stars
that gives birth to new stellar systems
and we also specialize in looking at
galaxies that are
very very far away near the beginning of
our cosmic history
to figure out where all of these large
scale galactic structures
in our universe first come from there's
a variety of
different sort of hidden universes that
are out there when we look up at the
night sky
our eyes only pick up a very small
sliver of the total light that's
actually coming in
we need specialized instruments to see
some of the physical material that's out
there
and it emits at these different
wavelengths it's amazing how a different
filter or even
type of telescope can completely change
our perception of the night sky
there's actually a good example of this
that you can try for yourself
if you live in the northern hemisphere
there's a very famous star you can find
in the constellation
cygnus called albirio you can find it at
the beak of cygnus which is also the
bottom of the northern cross
to the naked eye alberio appears as a
bright white star
but this is deceiving with a simple
telescope or even
a steadily held set of binoculars you
can see that alberio is
actually two stars one blue and one gold
but again when seen together with just
your eyes it appears blue white
it's an incredible example of how a pair
of very differently colored stars
can shift in appearance depending on how
we view them
also fun fact that gold star is actually
also two stars
so the next time you have a chance to
look at the night sky
in a good light pollution-free place
look for albireo in the northern
hemisphere
but if the timing or location isn't
right every star has a color
some are white blue orange yellow or red
thank you so much for watching this
video about the colors of stars
my name is serafina nance and this is
seeker constellations
if you have an astronomy related
question or an idea for an episode topic
let us know down in the comments below
thanks for watching