An Astro-comb is a type of
frequency comb In optics, a frequency comb is a laser source whose spectrum consists of a series of discrete, equally spaced frequency lines. Frequency combs can be generated by a number of mechanisms, including periodic modulation (in amplitude and/or phase) of a ...
used in observational
astronomy
Astronomy () is a natural science that studies astronomical object, celestial objects and phenomena. It uses mathematics, physics, and chemistry in order to explain their origin and chronology of the Universe, evolution. Objects of interest ...
to increase the resolution of
spectrograph
An optical spectrometer (spectrophotometer, spectrograph or spectroscope) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum, typically used in spectroscopic analysis to identify mat ...
s. The resulting increase in
spectral resolution The spectral resolution of a spectrograph, or, more generally, of a frequency spectrum, is a measure of its ability to resolve features in the electromagnetic spectrum. It is usually denoted by \Delta\lambda, and is closely related to the resolvi ...
allows for the detection of small variations in stellar
radial velocities caused by smaller orbiting exoplanets (e.g. Earth-mass planets), among other applications. Astro-combs are distinguished from conventional frequency combs by their focus on high
repetition frequencies (with mode spacings of ≥10 GHz).
A "green Astro-comb" was installed in January 2013 in the High Accuracy Radial velocity Planet Searcher in the Northern hemisphere (
HARPS-N
HARPS-N, the ''High Accuracy Radial velocity Planet Searcher for the Northern hemisphere'' is a high-precision radial-velocity spectrograph, installed at the Italian Telescopio Nazionale Galileo, a 3.58-metre telescope located at the Roque de los ...
) spectrograph at the
Telescopio Nazionale Galileo
The Galileo National Telescope, ( it, Telescopio Nazionale Galileo; TNG; code: Z19) is a 3.58-meter Italian telescope, located at the Roque de los Muchachos Observatory on the island of La Palma in the Canary Islands, Spain. The TNG is operated ...
on the
Canary Islands
The Canary Islands (; es, Canarias, ), also known informally as the Canaries, are a Spanish autonomous community and archipelago in the Atlantic Ocean, in Macaronesia. At their closest point to the African mainland, they are west of Mo ...
. The device was developed by a team led by Chih-Hao Li of
Harvard University
Harvard University is a private Ivy League research university in Cambridge, Massachusetts. Founded in 1636 as Harvard College and named for its first benefactor, the Puritan clergyman John Harvard, it is the oldest institution of high ...
. This Astro-comb uses a
pulsed laser Pulsed operation of lasers refers to any laser not classified as continuous wave, so that the optical power appears in pulses of some duration at some repetition rate. Silfvast, William T. (1996). ''Laser Fundamentals'', Cambridge University Press ...
to filter starlight before feeding the signal into a spectrograph. Currently, it is gathering data from Venus to demonstrate its ability to discover exoplanets.
See also
*
Frequency comb In optics, a frequency comb is a laser source whose spectrum consists of a series of discrete, equally spaced frequency lines. Frequency combs can be generated by a number of mechanisms, including periodic modulation (in amplitude and/or phase) of a ...
*
Comb filter
In signal processing, a comb filter is a filter implemented by adding a delayed version of a signal to itself, causing constructive and destructive interference. The frequency response of a comb filter consists of a series of regularly space ...
Citations
References
New Approaches to Precision Astrophysical SpectroscopyThe Walsworth Group, October 10, 2016. Accessed November 30, 2016.
TNG, HARPS-N and Astro Comb ready to characterize the first earth twinFundación Galileo Galilei - INAF Telescopio Nazionale Galileo, July 28, 2015. Accessed December 1, 2016
A green astro-comb to search for Earth-like planetsChih-Hao Li, SPIE, January 29, 2015. Accessed November 30, 2016.
Physorg.com
Phys.org is an online science, research and technology news aggregator offering briefs from press releases and reports from news agencies (a form of journalism sometimes pejoratively called churnalism). The website also produces its own science jo ...
, April 2, 2008. Accessed April 2, 2008.
Astro-combing for PlanetsAstro Biology Magazine, April 9, 2008. Accessed April 11, 2008.
Pulses to Find Planets (Archive o
Pulses to Find PlanetsAstro Biology Magazine, May 11, 2008. Accessed May 15, 2008. Based on a National Institute of Standards and Technology news release.)
Astronomical spectroscopy
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