Multi Unit Spectroscopic Explorer

Looking like a machine straight out of the movie The Matrix, with its Medusa-like hoses and connections, MUSE is the latest of the second-generation instruments to be installed on Yepun (UT4), the fourth Unit Telescope of the Very Large Telescope at the Paranal Observatory.

Like SINFONI, MUSE is an integral field spectrograph (IFS). An IFS allows you to observe the entirety of an astronomical object in one go, and for each pixel measures the intensity of the light as a function of its colour, or wavelength. The resulting data is a 3D set where each pixel of the image has a full spectrum of the light. MUSE splits the field of view into 24 individual image segments or channels which are each split further into 48 slices or “mini slits”, giving a total of 1152 mini slits. Each set of 48 mini slits is injected into a spectrograph, which disperses the light into its constituent colours, and MUSE measures over 4000 of these colours! From this, the 3D image is created. The instrument is designed to work with GALACSI’s adaptive optics system to compensate for the natural turbulence in the Earth’s atmosphere, giving much clearer images. With nearly 400 million pixels to be processed in real time, MUSE has presented Paranal Observatory with new computation and communication challenges. During commissioning alone, nearly half a billion spectra were produced!

MUSE has been built with the intention of studying the content and processes going on in the very early Universe, when the first stars and galaxies were forming,” explains Fernando Selman, Instrument Scientist for MUSE. “Closer in time and space, MUSE will map the dark matter distribution in clusters of galaxies using the gravitational microlensing effect on background galaxies.” MUSE will also provide detailed information about the internal dynamics of many classes of galaxies with unprecedented detail. “It has already been used to study the Sombrero Galaxy in Virgo, and, in the same cluster, a recently discovered new type of object — a galaxy being destroyed after falling into the cluster and encountering the cluster’s hot gaseous corona,” continues Fernando. An image of this galaxy is shown on this page. The stars themselves found within bigger objects will also be a focus of study — impressive vistas of the Tarantula Nebula and its huge collection of massive young stars have been obtained during the testing phase, and an enormous mosaic of the Orion Nebula has been produced.

In our immediate neighbourhood,” Fernando says, “the commissioning team produced images of Jupiter and Saturn that illustrate the amazing optical quality of the instrument, better than any mathematical measurement could do! During its lifetime we expect many great contributions from this instrument to a wide range of astronomical investigations.

Science highlights with MUSE

  • Plenty to come! The instrument had just been installed at the telescope when this page was written.
  • MUSE Reveals True Story Behind Galactic Crash (eso1437)
  • List of the scientific papers produced by MUSE, via the SAO/NASA Astrophysics Data System (ADS)


The authoritative technical specifications as offered for astronomical observations are available from the Science Operation page.

Name: Multi Unit Spectroscopic Explorer
Site: Paranal
Telescope: Very Large Telescope, UT4
Focus: Nasmyth
Type: Integral field spectrograph, imager
Wavelength coverage: 480–930 nm
Spatial resolution: Seeing limited, with 0.2-arcsecond pixels. With the GALACSI Adaptive Optics system: diffraction limited with 0.025-arcsecond pixels.
Spectral resolution: From 1700 in the blue to 3400 in the red.
First light date: March 2014 (eso1407)
Images taken with the instrument: Link
Images of the instrument: Link
Science goals: Galaxy formation, nearby galaxies, stars and resolved stellar populations, Solar System



France: Centre de Recherche Astrophysique de Lyon (CRAL); Laboratoire d’Astrophysique de Tarbes-Toulouse (LATT)

The Netherlands: Leiden Observatory (Sterrewacht Leiden)

Germany: Göttingen Astrophysics Institute (AIG); Potsdam Astrophysikalisches Institut (AIP)

Switzerland: Astrophysics department of the Zurich Polytechnic Institute of Technology (ETH)