Wednesday, August 25, 2010

Binary Stars: A Rough Neighborhood

NASA/JPL-Caltech
In an earlier post, Planets thrive around binary star systems, we learned that planetary systems around binary stars, specifically tight binary stars, may be more common than planetary systems around single stars (by a ratio of 3:1). However, the title "Planets thrive" may be misleading. While there may be more planets around tight binary star systems, they may exist in a rough neighborhood.

Gravity Slam Dancing

The problem arises from the gravitational dance of the binary stars. As they dance tightly around a common center of gravity, they find themselves moving closer to each other, always facing each other. This is not a sweet, romantic dance. The stars spin rapidly, creating massive magnetic fields and intense solar winds. But worse yet is that the intense solar winds slow the stars down, pulling them closer to each other. As stars dance closer, their gravitational effects on the planets orbiting them change - creating chaos and a great likelihood for collisions between planets, asteroids, and comets.

There Goes the Neighborhood

This chaos does not bode well for life. While it may be argued that some chaos is good as it may add to evolutionary pressure, too much chaos is not good - especially if that chaos means your planet colliding with another, or being pummeled by one too many extinction event asteroids. And even if your planet does not collide with another, it may change orbit, moving out of the habitable zone. Either way, there goes the life-giving neighborhood.

This is not to say life in a tight binary star system is impossible, or that high order sentient life cannot evolve and survive; but it does mean that such a system is not the top candidate to target in a search for life.

Reference:

Clavin, Whitney. "Pulverized Planet Dust May Lie Around Double Stars." Jet Propulsion Laboratory. NASA. 23 August 2010. Web. 25 August 2010.

Saturday, August 21, 2010

Life in the Infrared

In1996 scientists were surprised to find a version of chlorophyll, chlorophyll d, in a cyanobacterium (blue-green algae or blue-green bacteria) that can photosynthesize light at 710nm, just in the infrared region. How it can get enough energy to photosynthesize is a mystery right now. It is possible that it acts more like chlorophyll a, passing on the captured energy to other chlorophyll molecules which then do the actual photosynthesis.

Recently, Dr Min Chen, from the University of Sydney, discovered in cyanobacterium living inside stromatolites another chlorophyll molecule which can absorb infrared light - this time deeper into the infrared range at 720 nm. This molecule, chlorophyll f, raises the same question as with chlorophyll d: how does it get enough energy from infrared light to photosynthesize oxygen? Or does it act as a helper, passing on the energy to other chlorophyll?

While this discovery has implications for biotechnology and bioenergy, it also has implications for life on other planets. As Dr. Chen remarks:

the fact that we have discovered a cyanobacterium that exploits a tiny modification in its chlorophyll molecule to photosynthesise in light that we cannot see, opens our mind to the seemingly limitless ways that organisms adapt to survive in their environment.
This helps expands the environmental range where we can look for life. For instance, it helps increase the possibility of life arising around class M stars (see Color of Life for more information). Yet more evidence that Dr. Ian Malcolm's (Jurassic Park) adage is correct: life will find a way.

Reference:

Chen, Min, et. al. "A Red-Shifted Chlorophyll." Science Magazine. 19 August 2010. Web. 21 August 2010. <http://www.sciencemag.org/cgi/content/abstract/science.1191127>