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]

See also

• Comb filter

References

1. "Frequency Combs to Measure Cosmic Velocities". Astrocombs. LMU University of Munich. 2015-03-08. Retrieved 25 January 2022.
2. "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.
3. 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.
4. "Astro Combs". Astro Combs. Harvard & Smithsonian. 2017-03-03. Retrieved 25 January 2022.
5. 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.
6. "A green astro-comb to search for Earth-like exoplanets". spie.org. Retrieved 2016-12-01.
7. "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.)