Astrocomb Helps Make Hunt for Earth-Like Planets More Precise

The Hobby-Eberly Telescope in Texas has a new astrocomb for helping it look for life in space.
Jessica Miley

New technology is helping scientists look for Earth-like planets with more precision than ever before. A National Institute of Standards and Technology (NIST) “Astrocomb” can provide record-setting starlight measurements that could even help locate extraterrestrial life


NIST has custom-built a new frequency comb for use in an instrument called a spectrograph at the Hobby-Eberly Telescope in Texas. The comb precisely measures frequencies, or colors, of light and assist in the accuracy of the starlight analysis done by the spectrograph. 

Comb helps scientist examine stars with more precision 

The comb provides the precision needed for discovering and characterizing planets orbiting M dwarf stars. These stars makeup 70 percent of the stars in the galaxy and are plentiful near Earth, the research team said.

"The comb immediately allowed our Penn State colleagues to make measurements they could not otherwise make," NIST Fellow Scott Diddams said.

"These improved tools should allow us to find habitable planets around the most ubiquitous stars in our galaxy."

Scientists search for planets by examining the white light emitted from a stars' nuclear furnace. Astronomers examine this light for periodic changes, these changes appear as variations in the apparent colors of starlight over time. 

Planets subtly 'wobble' neighboring star

The change in color is caused by the star being pulled back and forth by the gravitational pull of an unobservable orbiting planet. The stars wobble is very subtle and can only be observed by highly precise spectrographs. 


Many planets have been discovered using this technique but finding planets with a similar mass to Earth is slightly harder with the existing technology. The new comb will make the detection of Earth-like planets far easier thanks to its increased precision in the infrared region of the electromagnetic spectrum. 

NIST researchers in Boulder, Colorado, invented the astrocomb twenty years ago, and have been refining and improving their accuracy ever since.

The new Texas comb was made especially for the reading capability of Penn State's Habitable Zone Planet Finder spectrograph and spans the target infrared wavelength band of 800-1300 nm. 

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Astrocomb Helps Make Hunt for Earth-Like Planets More Precise
Source: NIST

It has around 5,000 widely spaced "teeth," or specific color calibration points. The powerful piece of equipment is small, totaling just 60 by 152 square centimeters in size and made of relatively simple commercial components. 

It has been designed to stand up to continuous use in a rugged environment. The comb works by calibrating and tracking the exact colors in a star’s ‘fingerprint’ and reports any periodic variations. It is created with new electro-optic laser technology and can be traced to international measurement standards. 

Long time coming for planet-hunting telescope

The project has been under development for several years. A test of an earlier version of the comb was done in 2012 and the final version saw ‘first night’ in February 2018. 

The most recent version has a broader light range and is more stable than the earlier demo version. This is the first anywhere in the world that is in operation at near-infrared wavelengths. Research on the comb is published in the latest edition of Optica.

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