March/April 2012
Automation Update

Laser frequency comb to aid quest for Earth-like planets

If there is life on other planets, a laser frequency comb developed at the National Institute of Standards and Technology (NIST) may help find it.

Such a comb-a tool for precisely measuring frequencies, or colors, of light-has for the first time been used to calibrate measurements of starlight from stars other than the Sun, reports ScienceDaily. The good results suggest combs will eventually fulfill their potential to boost the search for Earth-like planets to a new level.

The comb was transported to Texas to calibrate a light analyzing instrument called a spectrograph at the Hobby-Eberly telescope.

The NIST comb calibrated measurements of infrared starlight. This type of light is predominantly emitted by M dwarf stars, which are plentiful in Earth's part of the galaxy and might have orbiting planets suitable to life.

To search for planets orbiting distant stars, astronomers look for periodic variations in the apparent colors of starlight over time. A star's nuclear furnace emits white light, which is modified by elements in the star's and Earth's atmosphere that absorb certain narrow bands of color. Periodic changes in this characteristic "fingerprint" can be caused by the star wobbling from the gravitational pull of an orbiting planet.

The wobbling effect is very subtle. Astronomers are limited by the precision of techniques used to measure the starlight, and infrared frequencies in particular can be challenging to measure precisely with conventional tools. But the NIST comb, which spans an infrared wavelength range of 1450-1700 nanometers, provides strong signals at narrowly defined target frequencies and is traceable to international measurement standards.

The NIST comb measured radial velocity (star wobble) with a precision of about 10 meters per second.