# BlackGEM

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Telescope array

BlackGEM Location(s) Chile Organization KU Leuven Netherlands Research School for Astronomy Radboud University Nijmegen Diameter 65 cm (2 ft 2 in) Website astro.ru.nl/blackgem/ Related media on Commons [edit on Wikidata]

**BlackGEM** is an array of [optical telescopes](/source/Optical_telescope) located at the [La Silla](/source/La_Silla_Observatory) [astronomical observatory](/source/Astronomical_observatory) in [Chile](/source/Chile).[1][2] This system is specifically designed to detect the optical counterparts from [gravitational wave](/source/Gravitational_wave) sources detected with [Virgo](/source/Virgo_interferometer) and [LIGO](/source/LIGO). Principal investigator of the array is [Paul Groot](https://en.wikipedia.org/w/index.php?title=Paul_Groot&action=edit&redlink=1).

## Characteristics

Prototype BlackGEM telescope in the dome in [Nijmegen](/source/Nijmegen), The Netherlands.[3]

The BlackGEM array will consist of 10-15 telescopes each 65 cm in diameter when completed. This configuration uniquely allows the pointing of the combined telescope to be matched to the often elongated ellipse-shaped source-location estimates provided by gravitational wave detectors. Once an optical counterpart has been detected, all telescopes are pointed at the target giving a light-collecting area and sensitivity equivalent to that of a single 3.5 m diameter telescope, but with a larger two-square-degree [field of view](/source/Field_of_view#Astronomy).

Each telescope is equipped with a 10,000 by 10,000 pixel [CCD](/source/Charge-coupled_device) with 9 micron pixel size that samples the full focal plane of the telescope. This, combined with the (f/5.5) [focal length](/source/Focal_length) of the telescope, means that the [angular resolution](/source/Angular_resolution) of the instrument is limited only by the [seeing](/source/Astronomical_seeing) (which is about 1 [arcsecond](/source/Minute_and_second_of_arc) at La Silla). Being located at this longitude enables rapid [spectroscopic](/source/Astronomical_spectroscopy) follow-up of any detected gravitational wave source with, for instance, the [Very Large Telescope](/source/Very_Large_Telescope).

## Operational phases

The array will eventually comprise 15 telescopes, each of 65cm diameter, making BlackGEM a powerful survey instrument. The first phase of operations will therefore perform a complete survey of the southern sky in 6 different filters, to generate the necessary templates for [image subtraction](/source/Image_subtraction). In parallel to this phase, multi-[epoch](/source/Epoch_(astronomy)) imaging will give a characterization of any fast (shorter than one day) [transient](/source/Transient_astronomical_event) sources down to 23rd [magnitude](/source/Magnitude_(astronomy)). In parallel, the BlackGEM array will act on triggers from the gravitational wave detectors to look for optical emission from such events as [merging](/source/Stellar_collision) [black holes](/source/Black_hole) and [neutron stars](/source/Neutron_star).

As of 2022, three (of a planned 15) telescopes are in place at ESO's La Silla Observatory. Due to the [COVID-19 pandemic](/source/COVID-19_pandemic), on-site work on the telescopes was temporarily on pause.[4] As of 2024, some discoveries are beginning to be made by BlackGEM.[5]

## See also

- [Lists of telescopes](/source/Lists_of_telescopes)

## References

1. **[^](#cite_ref-1)** ["BlackGEM - Joining the search for the sources of gravitational waves"](https://www.eso.org/public/teles-instr/lasilla/blackgem/). [European Southern Observatory](/source/European_Southern_Observatory). Retrieved July 1, 2017.

1. **[^](#cite_ref-2)** Groot, Paul J.; Bloemen, S.; Vreeswijk, P.; van Roestel, J.; Nelemans, G.; Klein-Wolt, M.; Poole, R. Le; Pieterse, D.; Rodenhuis, M. (2024-05-29). "The BlackGEM Telescope Array. I. Overview". *Publications of the Astronomical Society of the Pacific*. **136** (11). [arXiv](/source/ArXiv_(identifier)):[2405.18923](https://arxiv.org/abs/2405.18923). [Bibcode](/source/Bibcode_(identifier)):[2024PASP..136k5003G](https://ui.adsabs.harvard.edu/abs/2024PASP..136k5003G). [doi](/source/Doi_(identifier)):[10.1088/1538-3873/ad8b6a](https://doi.org/10.1088%2F1538-3873%2Fad8b6a).

1. **[^](#cite_ref-3)** ["BlackGEM Telescope to be Sited at ESO's La Silla Observatory - Exciting gravitational wave follow-up telescope conceived"](https://www.eso.org/public/announcements/ann17067/). *www.eso.org*. Retrieved 9 October 2017.

1. **[^](#cite_ref-4)** ["BlackGEM – Telescope array for detecting gravitational wave counterparts"](https://astro.ru.nl/blackgem/). Retrieved 2022-03-24.

1. **[^](#cite_ref-5)** Groot, P.; Tranin, H.; Vreeswijk, P.; Ramsay, G. (2024). ["AT2024qc in WISEA J103650.74-260918.8 at 55 MPC"](https://www.wis-tns.org/astronotes/astronote/2024-9). *Transient Name Server Astronote*. **9**: 1. [Bibcode](/source/Bibcode_(identifier)):[2024TNSAN...9....1G](https://ui.adsabs.harvard.edu/abs/2024TNSAN...9....1G).

[Portals](https://en.wikipedia.org/wiki/Wikipedia:Contents/Portals):
- [Chile](https://en.wikipedia.org/wiki/Portal:Chile)
- [Astronomy](https://en.wikipedia.org/wiki/Portal:Astronomy)
- [Stars](https://en.wikipedia.org/wiki/Portal:Stars)
- [Spaceflight](https://en.wikipedia.org/wiki/Portal:Spaceflight)
- [Outer space](https://en.wikipedia.org/wiki/Portal:Outer_space)
- [Solar System](https://en.wikipedia.org/wiki/Portal:Solar_System)

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