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GRAVITY (VLTI)

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VLTI GRAVITY
Beam Combining Instrument (BCI), which is the main part of GRAVITY from the outside
BCI with the cover removed

GRAVITY is an instrument on the interferometer of the Very Large Telescope (VLTI). It either combines the light of the four Unit Telescopes (UT) or the smaller four Auxiliary Telescopes. The instrument works with adaptive optics and provides a resolution of 4 milliarcseconds (mas) and can measure the position of astronomical objects down to a few 10 microarcseconds (μas).[1] VLTI GRAVITY has a collecting area of 200 m2 and the angular resolution of a 130 m telescope.[2]

Instrument details

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GRAVITY was built by a consortium led by the Max Planck Institute for Extraterrestrial Physics.[3] Other partner institutes are from France, Germany, Portugal and the European Southern Observatory.[4] The first light images included the discovery that Theta1 Orionis F in the Trapezium Cluster is a binary.[3]

GRAVITY can operate in single-field mode or in dual-field mode. In the dual-field mode it can interfere two astronomical objects at the same time and acquire this way very accurate astrometry. The instrument data can also be used for K-band spectroscopy with tree spectral resolutions. GRAVITY has the following sub-components:[4]

  • IR wavefront sensing system CIAO (located at the Unit Telescopes) that will work with the MACAO deformable mirror
  • A polarisation control system to counteract polarisation effects in the VLTI
  • An active pupil guide system including LED sources mounted on each of the telescope secondary mirror support (spiders)
  • A field-guide system to track the position of the source
  • The Beam Combining Instrument (BCI)

The Beam Combining Instrument is the primary unit of GRAVITY. It performs acquisition and provides interferometric fringes. BCI is cryogenically cooled and located in the VLT-I laboratory.[4]

Science

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Orbit of stars at the center of the Milky Way imaged with GRAVITY

GRAVITY is mainly used to observe the stars orbiting the supermassive black hole Sagittarius A*[5] and the position of exoplanets and brown dwarfs around their host star.[6][7] It is also used for other studies that require a high resolution, such as the study of circumstellar disks[8] and the study of AGNs.[9]

GRAVITY+

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GRAVITY+ is the upgrade of GRAVITY, which will increase its sensitivity and increase its sky coverage. The upgrade is performed incrementally to reduce the disruption of astronomical observations.[10][11]

References

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  1. ^ information@eso.org. "GRAVITY". www.eso.org. Retrieved 2024-10-17.
  2. ^ GRAVITY Collaboration; Abuter, R.; Accardo, M.; Amorim, A.; Anugu, N.; Ávila, G.; Azouaoui, N.; Benisty, M.; Berger, J. P.; Blind, N.; Bonnet, H.; Bourget, P.; Brandner, W.; Brast, R.; Buron, A. (2017-06-01). "First light for GRAVITY: Phase referencing optical interferometry for the Very Large Telescope Interferometer". Astronomy and Astrophysics. 602: A94. arXiv:1705.02345. Bibcode:2017A&A...602A..94G. doi:10.1051/0004-6361/201730838. ISSN 0004-6361.
  3. ^ a b "First Light For Future Black Hole Probe". www.mpe.mpg.de. Retrieved 2024-10-17.
  4. ^ a b c "ESO - Instrument Description". www.eso.org. Retrieved 2024-10-17.
  5. ^ information@eso.org. "ESO Telescope Sees Star Dance Around Supermassive Black Hole, Proves Einstein Right". www.eso.org. Retrieved 2024-10-17.
  6. ^ information@eso.org. "GRAVITY Instrument Breaks New Ground in Exoplanet Imaging - Cutting-edge VLTI instrument reveals details of a storm-wracked exoplanet using optical interferometry". www.eso.org. Retrieved 2024-10-17.
  7. ^ Balmer, William O.; Pueyo, Laurent; Stolker, Tomas; Reggiani, Henrique; Maire, A. -L.; Lacour, S.; Mollière, P.; Nowak, M.; Sing, D.; Pourré, N.; Blunt, S.; Wang, J. J.; Rickman, E.; Kammerer, J.; Henning, Th. (2023-10-01). "VLTI/GRAVITY Observations and Characterization of the Brown Dwarf Companion HD 72946 B". The Astrophysical Journal. 956 (2): 99. arXiv:2309.04403. Bibcode:2023ApJ...956...99B. doi:10.3847/1538-4357/acf761. ISSN 0004-637X.
  8. ^ GRAVITY Collaboration; Perraut, K.; Labadie, L.; Bouvier, J.; Ménard, F.; Klarmann, L.; Dougados, C.; Benisty, M.; Berger, J. -P.; Bouarour, Y. -I.; Brandner, W.; Caratti O Garatti, A.; Caselli, P.; de Zeeuw, P. T.; Garcia-Lopez, R. (2021-11-01). "The GRAVITY young stellar object survey. VII. The inner dusty disks of T Tauri stars". Astronomy and Astrophysics. 655: A73. arXiv:2109.11826. Bibcode:2021A&A...655A..73G. doi:10.1051/0004-6361/202141624. ISSN 0004-6361.
  9. ^ "Science". www.mpe.mpg.de. Retrieved 2024-10-17.
  10. ^ information@eso.org. "GRAVITY+". www.eso.org. Retrieved 2024-10-17.
  11. ^ Gravity+ Collaboration; Abuter, R.; Alarcon, P.; Allouche, F.; Amorim, A.; Bailet, C.; Bedigan, H.; Berdeu, A.; Berger, J. -P.; Berio, P.; Bigioli, A.; Blaho, R.; Boebion, O.; Bolzer, M. -L.; Bonnet, H. (2022-12-01). "The GRAVITY+ Project: Towards All-sky, Faint-Science, High-Contrast Near-Infrared Interferometry at the VLTI". The Messenger. 189: 17–22. arXiv:2301.08071. Bibcode:2022Msngr.189...17A. doi:10.18727/0722-6691/5285. ISSN 0722-6691.
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