ESO’s MATISSE Instrument Looks For Nano-Diamonds Around Nearby Stars

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On a recent gorgeous autumn afternoon high above Nice, France, my Uber driver screeched to an abrupt halt at the storied entrance to the Observatoire de la Cote d’Azur. It’s the kind of exotic setting that evokes visions of Hollywood on the Riviera, a la Grace Kelly and Cary Grant. But despite the observatory architecture’s old-world air, cutting-edge research is being conducted within. In particular, a state-of-the-art telescopic instrument now installed in the far reaches of Chile’s Atacama Desert was built inside these walls.

Since 2018, MATISSE, the Multi Aperture Mid-Infrared SpectroScopic Experiment (MATISSE) at the European Southern Observatory’s Very Large Telescope (VLT) in Chile has been in the commissioning phase. Some 50 people have been working on its implementation for a decade, with tens of doctoral researchers who are already benefiting from its observations.

The 16 million Euro ($17.6 million) instrument will observe protoplanetary disks, the active centers of distant galaxies; the birth of massive stars; and our Milky Way’s galactic center.

My favorite MATISSE science goal is the stellar physics to better understand the mass loss of stars, says Bruno Lopez, MATISSE’s principal investigator and an astronomer at Nice Observatory. Most stars lose their mass at the end of their lives, he says, but we exist because we are made of materials processed and recycled by stars.


Even now our own sun is losing mass, says Lopez. The solar protons that make up the solar wind is part of this mass loss, he says.

MATISSE will also enable astronomers to observe the earliest stages of planet formation around sunlike stars. By observing the warm material surrounding very young stars, Lopez says he and colleagues want to search for initial conditions of planet formation.

We want to see how dust grains —- the elementary materials of solar systems —- are transformed by conditions near the star, says Lopez.

Interferometry can combine light from a celestial target so that the optical paths between each telescope down to the detectors are perfectly equalized. This enables astronomers to synthesize data from a celestial target so that it mimics a much larger aperture telescope.

The resolution is equal to as much as a 150-meter optical telescope, says Lopez. This allows us to see details down to a fraction of an astronomical unit around young stars as much as 450 light years away, he says.

But if interferometry can mimic the results of a large aperture telescope, why build large aperture ground-based telescopes in the first place?

When you build a monolithic telescope you increase the collecting power and sensitivity useful for observing the faint deep sky and distant galaxies, says Lopez. Interferometry, in contrast, also gives astronomers the ability to improve a telescope’s angular resolution (or how precisely you can see the detail in a given image).

MATISSE can either combine light from the VLT’s four giant 8.2 meter telescopes or the smaller four 1.8 meter auxiliary telescopes.

Lopez would also like to use MATISSE to detect and characterize nanometer-sized diamonds in space. MATISSE is already observing nano-diamonds around a few stars, including HD 9748, a young 10-million year-old star that has yet to begin its life on the hydrogen-burning main sequence.

Lopez and colleagues expect to submit a journal paper about their observations of diamonds around this hot, blue star by February.

Only four stars are currently known to have diamonds in their circumstellar disks, says Lopez.

MATISSE is being touted as an observational means to link the Near-IR to the millimeter wavelength spectrum.

In protoplanetary disks, if you observe in the Near IR; you mostly observe the material at temps of 1000 to 1500 K, says Lopez. In the millimeter range, by contrast, you observe cold material and gas emission with temperatures between 60 to 100 K, he says.

And as Lopez demonstrates our own skin is a very sensitive detector of this wavelength range. To make his point, he places his two palms facing each other, so that they are just a couple of inches apart.

“It’s easy to feel our body’s mid-infrared 300 kelvin emission; our skin is a perfect Mid-IR sensor,” said Lopez.

It really does work. Try it yourselves.

With MATISSE, we are able to see emission from 300 to 1500 K material, says Lopez. This allows us to study a protoplanetary disk from a fraction of an astronomical unit nearest to the star, up to about 10 AU (Earth-Sun distances), he says.

After our sit-down interview, Lopez drives us up the hill to a spectacular overlook not far from the observatory’s venerable 93-centimeter refractor telescope. Although its grand dome is currently under renovation, the structure itself was designed by Gustav Eiffel back when his plans for the Eiffel Tower were still just a twinkle in his eye.

How times have changed.

Today, Lopez and colleagues can sit in the comfort of their offices and make their MATISSE observations from half a world away. ESO staff astronomers and technicians are onsite to actually move the telescope into position to make the observations for the team back in Nice who are connected to the VLT via Skype.

MATISSE observations with the VLT’s four 8.2-meter units are planned for the 8th of December from Lopez’s desktop computer.

Lopez is already collaborating with NASA on how MATISSE can complement observations with the James Webb Space Telescope (JWST), now scheduled for launch in 2021. Both MATISSE and the JWST will observe in the same wavelength domain.

And although MATISSE has a resolving power 15 times better than the JWST, the new space telescope will still be a thousand times more sensitive to faint objects, says Lopez.