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[Key Words]
[What Is A Star]
[How
Long Does It Take For A Star To Form]
[How Bright Is A Star]
[How Hot Is A Star]
[How Far Away Are Stars]
What Is A Star?
A star is
a giant ball of gas which releases energy produced by nuclear
fusion in its core. Stars are composed of at least 99%
hydrogen and helium. These elements are combined by nuclear
fusion to create heavier elements, such as carbon.
There are many different types of stars. These include
variable stars, supernovae, novae, and others. Each of these
stars have their own characteristics that make them unique.
How
Long Does It Take For A Star To Form?
There are many different stages in the lifetime of a
star. Usually, it takes up to millions or billions of years to
complete these stages. It takes a few million years for a gas
cloud to collapse and become a star. Stars that have about 50
times the mass of our sun can last for about 10 million years. On
the other hand, stars with 1/100 the mass of our sun can last for
up to one trillion years.
[More about the life of a star]
How Bright Is A Star?
Our sun's luminosity is about
average as compared to other stars throughout the galaxy. Some celestial
objects are up to 600,000 times as bright, while others are
1/550,000 as bright. Generally though, stars range from being
1/10,000 times as bright to 10,000 times as bright as our sun.
Brightness is measured in magnitude.
Apparent
magnitude (m) is determined by distance and
absolute
magnitude (M). Apparent magnitude is basically how
bright it appears on earth. Absolute magnitude is how bright the
object would be if view from 10 parsecs away (about 32
light-years).
There is a simple system used to
express the difference between magnitudes. A magnitude 1 (written
1m) is about 2.5 times as bright as a 2m, a
2m is about 2.5 times ad bright as a 3m,
and so on. In the end, a 0m is exactly 100 times as
bright as a 5m. An object with a magnitude of six is
the dimmest the naked eye can see. Some objects are so bright
that their magnitude is negative. For example, Venus has a
magnitude of -4, and the sun's magnitude is -27!
The brightest star is Sirius with an apparent magnitude of
-1.45, other bright stars are as follows.
| Name |
Constellation |
Absolute
Magnitude |
Apparent
Magnitude |
Distance in
Light-years (aprox.) |
| Sirius |
Canis Major |
+1.4 |
-1.45 |
8.58 |
| Canopus |
Carina |
-4.7 |
-0.73 |
196 |
Rigel Kentaurus
(AKA Alpha Centauri) |
Centaurus |
+4.3 |
-0.1 |
4.37 |
| Arcturus |
Boötes |
-0.2 |
-0.06 |
36 |
| Vega |
Lyra |
+0.5 |
+0.04 |
26 |
| Capella |
Auriga |
-0.6 |
+0.08 |
46 |
How Hot Is A Star?
Stars are extremely hot. There is no set temperature
for a star. It basically depends on the size, mass, and stage of
the star. Temperature also depends on the part of the star. The
center of A star is much hotter than the outside of a star.
Normal stars can get as hot as 90,000° F. Our sun's temperature
is about 10,000° F. Newly created neutron stars and white dwarfs
start off being about 360,000° F before cooling down to below
90,000° F.
How Far Away Are
Stars?
The distance to a star is measured in light-years.
A light-year is the distance that light travels in one year. This
number is about 6 trillion miles. The nearest star (besides our
sun) is 4.24 light-years from earth. This means that light
emitted for this star takes 4.24 years to reach earth. Some stars
are over millions of light-years away. The closest star is the
sun. Beyond that is Proxmia Centauri, at 4.24 light-years away.
Alpha Centauri is at 4.37 light-years, and beyond that is
Barnard's star at 5.97 light-years away.
Next Topic: Life Cycle
of a Star
[Key Words]
[What Is A Star]
[How
Long Does It Take For A Star To Form]
[How Bright Is A Star]
[How Hot Is A Star]
[How Far Away Are Stars]
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