Download PPT

Ask the Scientists
Questions for Dr. Butner
Star Formation 1/29/11
How can you tell the difference between a star that is
forming and a star that is about to collapse
 For massive stars, it might not be so easy as those stars
seem to live very short lives. However, even for these stars,
they seem to disperse their surrounding cloud material
before they die.
 So as a starting point we might say that…
 New stars (forming stars) are surrounded by cold dust and
gas
 Dying stars (stars about to collapse) might have shells of
material (planetary nebulae or winds) that they have sent off
into space signaling that their internal structure is becoming
unstable
Examples
Spectra are also different between the objects as well
so you can use the derived properties (temperature,
density, abundances) to help sort out which is which.
Star Formation
Note the extended gas/dark nebulae
Planetary Nebulae
Relatively Isolated Environment
What is the role of dark matter in the
process of star formation
 Dark Matter – it is the material responsible for
gravitational effects seen on very large scales
 Galaxies need dark matter (or something) to explain their
rotation curves
 Clusters of galaxies need dark matter to explain the
member velocities (i.e. if bound by gravity there is more
material than we see).
 So what does that mean for star formation?
 Local star formation – probably not a big impact since the
density of dark matter in our neck of the woods in the
galaxy not great
 But…
Early Star Formation
Dark Matter Can Be Important
 Recent results from the Herschel satellite suggest
 Early galaxies seem to have a burst of star formation
when the associated amount of mass including dark
matter is about 300,000,000,000 solar masses!
 See this story in Science Daily from 02/17/11
http://www.sciencedaily.com/releases/2011/02/110216133951.htm
 Early stars might be affected by dark matter
 Lots of models are being developed to explore HOW dark
matter might change the mass of stars that are formed and
hence the early production of heavier elements.
Are dark matter and dark energy related to
star formation?
 Dark matter may influence early galaxy formation and
the first stars.
 See recent results from Hubble Space Telescope and
Herschel Telescope
 Check out http://www.sciencedaily.com
 Dark energy will affect star formation in the future as its
influence grows. It will make star formation harder as
even the galaxies are pulled apart.
Are the dark clouds collapsing, spreading
or both?
 Both
 In some cases, they are collapsing as gravity wins over
other forces
 In other cases, they are spreading (expanding) as other
forces – such as stellar winds, radiation pressure, thermal
pressure – overcome gravity
 Currently astronomers are trying to figure out what is
going on with specific examples – and see what
influences are important at what time in the process…
The sun will expand into a red giant before
collapsing into a white dwarf, causing the
earth to heat up to an uninhabitable
climate. All planets should be similarly
affected.
When Mars warms up could it become a
viable ``surrogate planet’’ for life since it
has water?
A definite maybe!
The Yes part
•If there is enough water underground…
•If we move a comet ``onto’’ Mars, we can add water
The Maybe part
•Depends on the actual brightness of the sun.
•It might get more than 100 x its current brightness
•If it is too bright, even Mars might be too hot.
•Jupiter’s moon Europa might be a better choice…
1
Tplanet
 L L (1  reflectivity)  4

star
sun 


 280 K 
2


d
(1
AU)




Tplanet  Planet Temperature(deg rees Kelvin)
Lstar /Lsun  Stellar Lumin osities(in units of the sun)
d /(1AU)  distan ce of planet from sun in astronomical units
(or Earth orbital radii)
reflectivity  what fraction of the star' s energy bounces off
the top of the planet  i.e. does not heat the planet