Transcript Black Holes - WhatsOutThere

There are several black holes
throughout space. A black hole is a
region of space where gravity's pull
is so strong that nothing can escape
it.
What is a black hole?
• A black hole is a region of space where
gravity’s pull is so strong that not even
light can escape it. It is called “black”
because it absorbs all the light that hits it,
reflecting nothing. Although black holes
are invisible, astronomers know black
holes exist because of the impact they
have on the space around them.
How many types of black holes are
there
• According to astronomists, there may be three types of
black holes, the stellar, the super massive and the
miniature black holes-depending on their size. Super
massive black holes most likely exist in the centre of
most galaxies, including our own galaxy, the milky way.
They are named super massive if it has the equivalent
size of billions of suns. Miniature black holes are the
black holes that would only take within the existing time
of our universe to evaporate. A stellar black hole is when
its only about 20-30 times the suns mass and has been
formed by a star.
Do all stars become black holes?

Not all stars do become black holes, only stars
with very large masses can become black holes.
Our sun, for instance, is not big enough to
become a black hole, in four billion years from
now the sun will die a quiet death, killing no
one. More massive stars that are more then 20
times the suns mass may eventually become a
black hole.
How are black holes formed?

Black holes are formed when a star runs out of its
nuclear fuel that it needs to produce light, and it can
no longer hold its own weight and begins to collapse.
When this happens, a fraction of its outer layer that
often still contains some nuclear fuel activates a
reaction, and the star explodes. Then the core of the
star continues to collapse and depending if the core is
massive it will continue collapsing into a black hole.
A smaller star will stop collapsing and turn into a
neutron star.
What evidence do we have for the
existence of black holes?

Astronomers have found convincing evidence for
the existence of super massive black holes in the
center of several galaxies. The biggest black
hole is 3 billion times the mass of our sun, in the
centre of the ‘m87’ galaxy. The discovery is
based on a whirlpool of hot gas orbiting a big
black hole. For many years x-ray emissions from
the ‘double star system Cygnus-1’ has convinced
many astronomers that the system contains a
black hole. With much more precise
measurements available recently, there is very
strong evidence for a black hole in ‘Cygnus-1.’
What does a black hole
look like?
 We are not sure what a black hole looks like,
as they are invisible because no light can
escape from it. Astronomers can still identify
black holes by examining the effects on the
objects around them. They study clouds of gas
and stars moving at a very fast pace, and
normally conclude that there is a black hole in
that vicinity after further research. When a
smaller black hole and star orbit each other,
the black hole can be identified by astronomers
when the black hole starts pulling light from the
star.
Bibliography
► HubbleSite
- Reference Desk – FAQs
► http://cosmology.berkeley.edu/Education/BH
faq.html
► http://spaceplace.nasa.gov/en/kids/blackhol
e/index.shtml
► http://design.lbl.gov/education/blackholes/i
ndex.html
► http://imagine.gsfc.nasa.gov/docs/ask_astro
/black_holes.html
Conclusion

I have now thoroughly answered all of my
questions and my opinion is that a black
hole is like a giant cosmic vacuum cleaner
that sucks up anything that floats into its
path. I wonder if the sun really will die a
quiet death…..?
 Thanks for watching my PowerPoint
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