Of Matters Light and Dark

maxistentialist:

Laser directed towards the center of the Milky Way.

Some explanation:

Astronomers build bigger telescopes to get finer resolution.  The problem is, the atmosphere is turbulent and complicated and causes images to smear out.  That’s why astronomers go to remote, high altitude places.  There’s less light pollution and the atmosphere is much calmer.  Above the atmosphere, however, this isn’t a problem.  That’s why Hubble images are so much more beautiful than ground-based images, even though ground based telescopes have mirrors with 20 times more collecting area.

A modern solution to this problem is called “Adaptive Optics,” which takes the light from a bright star and measures how the waves get distorted by the atmosphere.  If the star is bright enough, the optics can make that measurement in real-time and then automatically deform the mirror with little actuators to correct for the distortion due to the atmosphere at any time.  This technique has been used, to great success, to study stars orbiting around the massive black hole at the center of our galaxy, which is exactly what this telescope is doing.

The problem is, many of the places we want to look don’t have sufficiently bright, nearby stars that we can pick out and measure the distortion due to the atmosphere.  So what do astronomers do?  They make their own stars!  This technique, called “Laser Guide Star Adaptive Optics” uses a laser that excites sodium atoms in the upper atmosphere and makes them shine like a bright star, basically putting a bright star in the sky right where it’s needed for the adaptive optics.

Cool, right?