Stars appear in different colors like blue, white, red, due to their surface temperatures according to Wein's law. Hotter stars have shorter wavelengths and appear blue, while cooler stars have longer wavelengths and appear red. The surface temperature of a star can be estimated by measuring its color. Blue stars are the hottest, around 25,000 degrees Celsius, while red stars are the coolest around 3,000 degrees Celsius.

1. COLORS OF
STARS
By:JohainaU. Nor

2. • Stars radiate light a little like glowing
coals in a campfire. Just as a glowing red-
hot coal is cooler than a white-hot coal, for
example, so a red star is cooler than a white
star, and a white star is cooler than a blue
star. This was a major scientific
discovery… simply by measuring the color
of light coming from a star, and applying a
little physics, it was possible to estimate a
star’s surface temperature.

3. Why are the
STARS
different color?

4. • Stars appear to be
exclusively white at first
glance. But if we look
carefully, we can notice a
range of colors: blue,
white, red, and even

5. Why should this be?
Why should the stars
come in so many
colors? Why not just
white?………….

6. • It turns out the answer is because
they are hot. All matter emits
radiation, peaking at a
wavelength (which can
sometimes be seen as a color)
which is dependent solely on the
temperature of the body.This is
known asWein's law
(pronouncedVeen's law).

7. • Most objects we encounter in everyday
life are somewhere around room
temperature. Give or take a few thousand
degrees.This effect, known as blackbody
radiation, happens to all objects,
regardless of it's temperature. Objects
which have a surface temperature just a
few degrees above absolute zero (which is
-273 c.) radiate most of their radiation in
the form of radio waves. Hotter than that,
and the object glows in microwaves.

8. • After that, it radiates largely in the form of
infrared waves. Hotter still, and the object
glows red, then orange, yellow, green, then
blue.This is the reason metal glows when it
is hot.When the temperature is hot
enough to have the atoms or molecules
moving at wildly different speeds at the
surface, all at around room temperature,
the object will be seen to glow white hot,
as white light is made from a composite of
all the visible colors.

9. • When an object reaches a temperature where it
becomes too hot to radiate black body radiation in
the visible wavelengths, it will shine in ultraviolet
wavelengths. Hotter still, x-rays, and finally gamma
rays.
•
• Why does this happen? Because as an object grows hotter,
there is, logically, more energy being released. As the energy
level of radiation is increased, the wavelength becomes
shorter and shorter. When the human eye perceives different
wavelengths of visible light, we interpret it as different
colors. This is why a rainbow always appears with the same
colors in the same order. Red, orange, yellow, green, blue,
indigo, and violet. You will never see a rainbow with any

10. Why are some stars
brighter than others?
• In general, a star’s brightness depends upon its
distance from us, its temperature and its size.
With stars of the same size, the hotter stars will
the brighter. With stars at the same distance and
of the same size, the hotter stars will be the
brighter. With stars at the same distance and the
same temperature, the larger stars will appear.

11. • The coolest stars are around 3,000 degrees c.They
are the red stars. Stars like the sun are next,
glowing at about 6,000 degrees c., and are, of
course, orange/yellow (although as we discussed
last week, the Sun is greener than you think).
• 10,000 degrees c. will buy you a green star, and the
going price on a blue star is around 25,000 degrees
c.There are cool stars which radiate in the infrared,
and will last dozens of billions of years.There are
stars which expend their energy in the ultraviolet,
and will last only a fraction of the lifetime of the
Sun. Many of these stars cannot be seen with the

12. Colors of stars
from hottest to
coldest

13. Observe the picture:

14. • Notice that hottest stars are blue,
while coldest stars are red. This
seems unusual to most people,
who associate red whit hot and
blue with cold. This is because we
see fire as yellow, orange or red,
but light produced by hotter
sources is blue.

15. Thank you for
listening!!!!!!

16. Get ⅟₄ sheet of
paper and answer
the following
questions!

17. Are you ready
for the short
quiz???

18. 1.Why are stars has a different
color?
2. What color of a star is the hottest
star?
3.Which is brighter ? Hotter or
Cooler?
4.
5.
Give me atleast 2
examples colors of
stars.

19. Exchange
papers!!!!

20. Answers:
1.Because they are HOT.
2. BLUE
3. HOTTER
4.
5.