Astro-comb

An astro-comb is a type of frequency comb used in observational astronomy to increase the accuracy of wavelength calibration in spectrographs.^[1]^[2] The increased accuracy reduces systematic errors and enhances detection of small variations in stellar radial velocities caused by smaller orbiting exoplanets (e.g. Earth-mass planets), among other applications.^[3]^[4] Astro-combs are distinguished from conventional frequency combs by their focus on high repetition frequencies (with mode spacings of ≥10 GHz).^[5]

A green astro-comb was installed in January 2013 in the high accuracy radial velocity planet searcher in the northern hemisphere (HARPS-N) spectrograph at the Telescopio Nazionale Galileo on the Canary Islands.^[6] The device was developed by a team led by Chih-Hao Li of Harvard University. This astro-comb uses a pulsed laser to filter starlight before feeding the signal into a spectrograph. As of December 2016, it is gathering data from Venus to demonstrate its ability to discover exoplanets.^[7]

References

^ "Frequency Combs to Measure Cosmic Velocities". Astrocombs. LMU University of Munich. 2015-03-08. Retrieved 25 January 2022.
^ "NIST 'Astrocomb' Opens New Horizons for Planet-Hunting Telescope". National Institute of Standards and Technology (NIST). National Institute of Standards and Technology (NIST). February 19, 2019. Retrieved 25 January 2022.
^ Chae, Eunmi; Kambe, Eiji; Motohara, Kentaro; Izumiura, Hideyuki; Doi, Mamoru; Yoshioka, Kosuke (1 July 2021). "Compact green Ti:sapphire astro-comb with a 43 GHz repetition frequency". Journal of the Optical Society of America B. 38 (7): A1. arXiv:2101.05926. Bibcode:2021JOSAB..38A...1C. doi:10.1364/JOSAB.419078. S2CID 231627499.
^ "Astro Combs". Astro Combs. Harvard & Smithsonian. 2017-03-03. Retrieved 25 January 2022.
^ Ravi, Aakash; Phillips, David F.; Beck, Matthias; Martin, Leopoldo L.; Cecconi, Massimo; Ghedina, Adriano; Molinari, Emilio; Bartels, Albrecht; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L. (17 November 2017). "Astro-comb calibrator and spectrograph characterization using a turn-key laser frequency comb". Journal of Astronomical Telescopes, Instruments, and Systems. 3 (4) 045003. arXiv:1705.07192. Bibcode:2017JATIS...3d5003R. doi:10.1117/1.JATIS.3.4.045003. S2CID 13676771.
^ "A green astro-comb to search for Earth-like exoplanets". spie.org. Retrieved 2016-12-01.
^ "TNG :: TNG, HARPS-N and Astro Comb ready to characterize the first earth twin". www.tng.iac.es. Retrieved 2016-12-01.

New Approaches to Precision Astrophysical Spectroscopy The Walsworth Group, October 10, 2016. Accessed November 30, 2016.
TNG, HARPS-N and Astro Comb ready to characterize the first earth twin Fundación Galileo Galilei - INAF Telescopio Nazionale Galileo, July 28, 2015. Accessed December 1, 2016
A green astro-comb to search for Earth-like planets Chih-Hao Li, SPIE, January 29, 2015. Accessed November 30, 2016.
'Astro-comb' helps search for Goldilocks planet Physorg.com, April 2, 2008. Accessed April 2, 2008.
Astro-combing for Planets Astro Biology Magazine, April 9, 2008. Accessed April 11, 2008.
Pulses to Find Planets, (Archive of Pulses to Find Planets Astro Biology Magazine, May 11, 2008. Accessed May 15, 2008. Based on a National Institute of Standards and Technology news release.)