Ask the ScientistsQuestions for Dr. ButnerStar 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

ExamplesSpectra are also different between the objects as

wellso you can use the derived properties

(temperature, density, abundances) to help sort out which is which.

Star FormationNote the extended gas/dark nebulae

Planetary NebulaeRelatively 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 scalesGalaxies need dark matter (or something) to

explain their rotation curvesClusters 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 FormationDark 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 matterLots 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 TelescopeCheck 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…

Tplanet 280K Lstar Lsun (1 reflectivity )d (1 AU) 2

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Tplanet Planet Temperature (degrees Kelvin)

Lstar /Lsun Stellar Luminosities(in units of the sun)d /(1AU) distance of planet from sun in astronomical units

(or Earth orbital radii)

reflectivity what fraction of the star's energy bounces offthe top of the planet i.e. does not heat the planet