ESPRESSO

ESPRESSO spectrograph concept at the Preliminary Design Review.
ESPRESSO spectrograph optical design at the Preliminary Design Review.

ESPRESSO (Echelle SPectrograph for Rocky Exoplanet- and Stable Spectroscopic Observations)[1] is a third-generation, fiber fed, cross-dispersed, echelle spectrograph mounted on the European Southern Observatory's Very Large Telescope (VLT). The unit saw its first light on September 25, 2016.[2][3]

ESPRESSO is the successor of a line of echelle spectrometers that include CORAVEL, Elodie, Coralie, and HARPS. It measures changes in the light spectrum with great sensitivity, and will be used to search for Earth-size rocky exoplanets via the radial velocity method. For example, Earth induces a radial-velocity variation of 9 cm/s on the Sun; this gravitational "wobble" causes minute variations in the color of sunlight, invisible to the human eye but detectable by the instrument.[4] The telescope light is fed to the instrument, located in the VLT Combined-Coude Laboratory 70 meters away from the telescope, where the light from up to 4 Unit Telescopes of the VLT can be combined. The Principal Investigator is Francesco Pepe.

Sensitivity

Data from ESPRESSO First Light.[5]

ESPRESSO will build on the foundations laid by the High Accuracy Radial Velocity Planet Searcher (HARPS) instrument at the 3.6-metre telescope at ESO’s La Silla Observatory. ESPRESSO will benefit not only from the much larger combined light-collecting capacity of the four 8.2-metre VLT Unit Telescopes, but also from improvements in the stability and calibration accuracy that are now possible by laser frequency comb technology. The requirement is to reach 10 cm/s,[6] but the aimed goal is to obtain a precision level of a few cm/s. This would mean a large step forward over current radial-velocity spectrographs like ESO's HARPS. The HARPS instrument can attain a precision of 97 cm/s (3.5 km/h),[7] with an effective precision of the order of 30 cm/s,[8] making it one of only two spectrographs worldwide with such accuracy. The ESPRESSO would greatly exceed this capability making detection of Earth-size planets from ground-based instruments possible. Commissioning of ESPRESSO at the VLT started late 2017.

The instrument is capable of operating in 1-UT mode (using one of the telescopes) and in 4-UT mode. In 4-UT mode, in which all the four 8-m telescopes are connected incoherently to form a 16-m equivalent telescope, the spectrograph will detect extremely faint objects.[4][9][10]

For example, for G2V type stars:

  • Rocky planets around stars as faint as V ~ 9 in (in 1-UT mode)
  • Neptune mass planets around stars as faint as V ~ 12 (in 4-UT mode )
  • Earth-size rocky planets around stars as faint as V ~ 9 (CODEX on the E-ELT) (2025)[11]

ESPRESSO will focus the observations on the best-suited candidates: non-active, non-rotating, quiet G dwarfs to red dwarfs. It will operate at the peak of its efficiency for a spectral type up to M4-type stars.

Instrument

First light of the ESPRESSO instrument with all four Unit Telescopes.[12]

ESPRESSO will use as calibration a laser frequency comb (LFC), with backup of two ThAr lamps. It will have three instrumental modes: singleHR, singleUHR and multiMR. In the singleHR mode ESPRESSO can be fed by any of the four UTs.[13]

Status

Engineering rendering of the ESPRESSO instrument[14]

All design work was completed and finalised by April 2013, with the manufacturing phase of the project commencing thereafter.[1] ESPRESSO was tested on June 3, 2016,.[15][16][17] ESPRESSO first light occurred on September 25, 2016, during which they spotted various objects, among them the star 60 Sgr A.[2][3] and after being shipped to Chile and installed at the VLT, ESPRESSO saw its first light there on 27 November 2017.[18][19] ESPRESSO is currently in testing phase, but by December 2018 it will officially begin its mission proper.[20]

Scientific objectives

The main scientific objectives for ESPRESSO are:[21][22]

  • The measurement of high precision radial velocities of solar type stars for the search for rocky planets in the habitable zone of their star.
  • The measurement of the variation of the physical constants
  • The analysis of the chemical composition of stars in nearby galaxies.

Consortium

ESPRESSO is being developed by a consortium consisting on the European Southern Observatory (ESO) and seven scientific institutes:

ESPRESSO specifications

ESPRESSO
Telescope VLT (8m)
Scope Rocky planets
Sky aperture 4 arcsec
R ~200.000
λ coverage 380 nm-686  nm[23]
λ precision 5 m/s
RV stability < 10 cm/s
4-VLT mode (D = 16 m) with RV = 1 m/s
Source:[11][24][22]

Radial velocity comparison tables

Planet Mass Distance
AU		 Radial velocity
(vradial)		 Note
Jupiter 1 28.4 m/s
Jupiter 5 12.7 m/s
Neptune 0.1 4.8 m/s
Neptune 1 1.5 m/s
Super-Earth (5 M⊕) 0.1 1.4 m/s
Alpha Centauri Bb (1.13 ± 0.09 M⊕) 0.04 0.51 m/s (1[25])
Super-Earth (5 M⊕) 1 0.45 m/s
Earth 0.09 0.30 m/s
Earth 1 0.09 m/s
Source: Luca Pasquini, power-point presentation, 2009[11] Notes: (1) Most precise vradial measurements ever recorded. ESO's HARPS spectrograph was used.[25][26]
Planets[11]
Planet Planet Type
Semimajor Axis
(AU)		 Orbital Period
Radial velocity
(m/s)		 Detectable by:
51 Pegasi b Hot Jupiter 0.05 4.23 days 55.9[27] First-generation spectrograph
55 Cancri d Gas giant 5.77 14.29 years 45.2[28] First-generation spectrograph
Jupiter Gas giant 5.20 11.86 years 12.4[29] First-generation spectrograph
Gliese 581c Super-Earth 0.07 12.92 days 3.18[30] Second-generation spectrograph
Saturn Gas giant 9.58 29.46 years 2.75 Second-generation spectrograph
Proxima Centauri b Habitable planet (potentially) 0.05 11.19 days 1.38[31] Second-generation spectrograph
Alpha Centauri Bb Terrestrial planet 0.04 3.23 days 0.510[32] Second-generation spectrograph
Neptune Ice giant 30.10 164.79 years 0.281 Third-generation spectrograph
Earth Habitable planet 1.00 365.26 days 0.089 Third-generation spectrograph (likely)
Pluto Dwarf planet 39.26 246.04 years 0.00003 Not detectable

MK-type stars with planets in the habitable zone

Stellar mass
(M☉)		 Planetary mass
(M⊕)		 Lum.
(L0)		 Type RHAB
(AU)		 RV
(cm/s)		 Period
(days)
0.10 1.0 8×10−4 M8 0.028 168 6
0.21 1.0 7.9×10−3 M5 0.089 65 21
0.47 1.0 6.3×10−2 M0 0.25 26 67
0.65 1.0 1.6×10−1 K5 0.40 18 115
0.78 2.0 4.0×10−1 K0 0.63 25 209
Source:[33][34]

See also

References

  1. 1 2 "ESO - Espresso". Retrieved 2012-10-24.
  2. 1 2 http://www.eso.org/public/usa/announcements/ann16073/ ESPRESSO Sees Light at the End of the Tunnel
  3. 1 2 http://www.media.inaf.it/2016/10/17/prima-luce-espresso-coude-lab/ ESPRESSO vede la luce in fondo al “tunnel”
  4. 1 2 "ESPRESSO - Searching for other Worlds". Centro de Astrofísica da Universidade do Porto. 2010-10-16. Retrieved 2010-10-16.
  5. ↑ "First Light for ESPRESSO — the Next Generation Planet Hunter". www.eso.org. Retrieved 7 December 2017.
  6. ↑ Pepe, F.; Molaro, P.; Cristiani, S.; Rebolo, R.; Santos, N. C.; Dekker, H.; Mégevand, D.; Zerbi, F. M.; Cabral, A.; et al. (January 2014). "ESPRESSO: The next European exoplanet hunter". Astronomische Nachrichten. 335 (1): 8–20. arXiv:1401.5918. Bibcode:2014arXiv1401.5918P. doi:10.1002/asna.201312004.
  7. ↑ "32 planets discovered outside solar system - CNN.com". CNN. 19 October 2009. Retrieved 4 May 2010.
  8. ↑ "ESPRESSO – Searching for other Worlds". Centro de Astrofísica da Universidade do Porto. 16 December 2009. Retrieved 2010-10-16.
  9. ↑ Pepe, Francesco A; Cristiani, Stefano; Rebolo Lopez, Rafael; Santos, Nuno C; Amorim, Antonio; Avila, Gerardo; Benz, Willy; Bonifacio, Piercarlo; Cabral, Alexandre; Carvas, Pedro; Cirami, Roberto; Coelho, João; Comari, Maurizio; Coretti, Igor; De Caprio, Vincenzo; Dekker, Hans; Delabre, Bernard; Di Marcantonio, Paolo; d'Odorico, Valentina; Fleury, Michel; García, Ramón; Herreros Linares, José Miguel; Hughes, Ian; Iwert, Olaf; Lima, Jorge; Lizon, Jean-Louis; Lo Curto, Gaspare; Lovis, Christophe; Manescau, Antonio; et al. (July 2010). "ESPRESSO: the Echelle spectrograph for rocky exoplanets and stable spectroscopic observations". Ground-based and Airborne Instrumentation for Astronomy III. 7735. American Institute of Physics. pp. 77350F. Bibcode:2010SPIE.7735E..0FP. doi:10.1117/12.857122.
  10. ↑ Pepe, Francesco A; Cristiani, Stefano; Rebolo Lopez, Rafael; Santos, Nuno C; Amorim, Antonio; Avila, Gerardo; Benz, Willy; Bonifacio, Piercarlo; Cabral, Alexandre; Carvas, Pedro; Cirami, Roberto; Coelho, João; Comari, Maurizio; Coretti, Igor; De Caprio, Vincenzo; Dekker, Hans; Delabre, Bernard; Di Marcantonio, Paolo; d'Odorico, Valentina; Fleury, Michel; García, Ramón; Herreros Linares, José Miguel; Hughes, Ian; Iwert, Olaf; Lima, Jorge; Lizon, Jean-Louis; Lo Curto, Gaspare; Lovis, Christophe; Manescau, Antonio; et al. (July 2010). "ESPRESSO: the Echelle spectrograph for rocky exoplanets and stable spectroscopic observations" (PDF). Ground-Based and Airborne Instrumentation for Astronomy Iii. 7735: 77350F. Bibcode:2010SPIE.7735E..0FP. doi:10.1117/12.857122. Retrieved 2013-03-12.
  11. 1 2 3 4 "ESPRESSO and CODEX the next generation of RV planet hunters at ESO". Chinese Academy of Sciences. 2010-10-16. Archived from the original on July 4, 2011. Retrieved 2010-10-16.
  12. ↑ "ESO's VLT Working as 16-metre Telescope for First Time - ESPRESSO instrument achieves first light with all four Unit Telescopes". www.eso.org. Retrieved 13 February 2018.
  13. ↑ https://arxiv.org/abs/1401.5918 ESPRESSO: The next European exoplanet hunter
  14. ↑ "ESO Awards Contracts for Cameras for New Planet Finder". ESO Announcement. Retrieved 8 August 2013.
  15. ↑ https://obswww.unige.ch/wordpress/espresso/2016/06/04/espresso-first-laboratory-light/
  16. ↑ ESPRESSO Planet Hunter Heads for Chile. European Southern Observatory. 22 August 2017. Accessed on 12 October 2017
  17. ↑ Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations, ESO
  18. ↑ http://www.eso.org/public/unitedkingdom/announcements/ann17053/ ESPRESSO Planet Hunter Heads for Chile
  19. ↑ https://phys.org/news/2017-12-espressothe-planet-hunter.html
  20. ↑ The black box set to revolutionise the search for life beyond Earth, archived from the original on 2018-02-09, retrieved 2018-08-20
  21. ↑ ESPRESSO - A VLT Project. Accessed 12 October 2017.
  22. 1 2 ESPRESSO Baseline Specification. European Southern Observatory (ESO). Accessed: 12 October 2017
  23. ↑ ESPRESSO. ESO.
  24. ↑ Pepe, F; Molaro, P; Cristiani, S; Rebolo, R; Santos, N. C; Dekker, H; Mégevand, D; Zerbi, F. M; Cabral, A; Di Marcantonio, P; Abreu, M; Affolter, M; Aliverti, M; Allende Prieto, C; Amate, M; Avila, G; Baldini, V; Bristow, P; Broeg, C; Cirami, R; Coelho, J; Conconi, P; Coretti, I; Cupani, G; D'Odorico, V; De Caprio, V; Delabre, B; Dorn, R; Figueira, P; et al. (2014). "ESPRESSO: The next European exoplanet hunter". arXiv:1401.5918v1 [astro-ph.IM].
  25. 1 2 "Planet Found in Nearest Star System to Earth". European Southern Observatory. 16 October 2012. Retrieved 17 October 2012.
  26. ↑ Demory, Brice-Olivier; Ehrenreich, David; Queloz, Didier; Seager, Sara; Gilliland, Ronald; Chaplin, William J.; Proffitt, Charles; Gillon, Michael; Guenther, Maximilian N.; Benneke, Bjoern; Dumusque, Xavier; Lovis, Christophe; Pepe, Francesco; Segransan, Damien; Triaud, Amaury; Udry, Stephane (25 March 2015). "Hubble Space Telescope search for the transit of the Earth-mass exoplanet Alpha Centauri Bb". Monthly Notices of the Royal Astronomical Society. 450 (2): 2043–2051. arXiv:1503.07528 [astro-ph.EP]. Bibcode:2015MNRAS.450.2043D. doi:10.1093/mnras/stv673. Cite uses deprecated parameter |class= (help)
  27. ↑ "51 Peg b". Exoplanets Data Explorer.
  28. ↑ "55 Cnc d". Exoplanets Data Explorer.
  29. ↑ Endl, Michael. "The Doppler Method, or Radial Velocity Detection of Planets". University of Texas at Austin. Retrieved 26 October 2012.
  30. ↑ "GJ 581 c". Exoplanets Data Explorer.
  31. ↑ "Proxima Cen b". The Extrasolar Planets Encyclopaedia.
  32. ↑ "alpha Cen B b". Exoplanets Data Explorer.
  33. ↑ "An NIR laser frequency comb for high precision Doppler planet surveys". Chinese Academy of Sciences. 2010-10-16. Retrieved 2010-10-16.
  34. ↑ Osterman, S; Diddams, S; Quinlan, F; Bally, J; Ge, J; Ycas, G (2010). "A near infrared laser frequency comb for high precision Doppler planet surveys". EPJ Web of Conferences. 16: 02002. arXiv:1003.0136. Bibcode:2011EPJWC..1602002O. doi:10.1051/epjconf/20111602002.
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