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Why MSE?

The Maunakea Spectroscopic Explorer (MSE) is a project to build a 10-meter class telescope that is fully devoted to spectroscopic exploration of our universe. The only such facility of its kind, MSE would analyse the light from millions of distant stars and galaxies per year to give uniquely powerful insights into the chemistry and dynamics of the Cosmos from the Milky Way galaxy to the largest scales of the Universe. The project will be realized by replacing the current 3.6m Canada-France-Hawaii Telescope with a large, wide-field, telescope operating a dedicated suite of spectroscopes.

Why Spectroscopy?

Astronomy images, while visually stunning, hold a limited amount of information for astronomers. To really understand objects, astronomers need to break the light into its component colors, called spectra. Astronomers analyze spectra to determine the composition and physical properties of an object (the temperature, chemistry and much more), as well as determining the motion of the object to reveal its dynamical history (and, in the case of extra-galactic objects, its “redshift”, which gives us the object’s age). This wealth of important physical information is only knowable by dispersing the light using spectroscopes.

With a 10-meter mirror, MSE will take about 3000 spectra per hour, or around 7 million spectra a year. Once astronomers have those spectra, they can analyse large statistical samples of similar objects or identify those rare objects that could be studied in greater detail on larger telescopes. These could be stars similar to our sun, stars with a unique composition, galaxies at a specific distance or many, many other projects.

What will MSE study?

With 7 million spectra per year, MSE astronomers will do more than look for interesting objects to follow up on other larger telescopes. One of the driving areas of research that MSE is designed to excel at is the galactic archaeology of our Milky Way. MSE will give us maps of the spectra of the stars in roughly a quarter of the volume of our Milky Way galaxy, around 20 million different stars. These maps will allow astronomers to characterize the chemical composition and dynamics of stars throughout all components of the Milky Way galaxy, reveal the nucleosynthetic history of the Galaxy and allow the construction of a model of the formation and development of the Milky Way throughout cosmic history. Further afield, MSE will produce unprecedented datasets of tens of millions of distant galaxies, to better understand the formation and properties of supermassive black holes, the star formation history of the Universe, and to act as a critical tool for better understanding the nature of Dark Matter and Dark Energy.

The scientific feasibility study goes into more detail on the science case for MSE.

Why Replace CFHT?

Maunakea is one of the best sites in the world for astronomy. CFHT’s site on the summit ridge is arguably the best single site for observations on all of Maunakea, making it an extremely desirable location. Previous engineering studies establish that CFHT’s existing summit facility can be modified to support a much larger telescope within the current CFHT footprint. By reusing much of the existing structure and pier, the facility can be upgraded while minimizing the work at the summit and impact on the surrounding summit ridge.

When operational, MSE will bridge existing large sky surveys and the next generation of telescopes. Large surveys, like SDSS, PanStarrs and CFHT’s own Legacy Survey, image millions of faint galaxies and stars. However, there is no other planned or existing facility that can target these faint objects in the numbers required to provide the spectra that are critical to better understand their astrophysical properties and so fully exploit the scientific potential of these datasets. MSE will fill that observational void.