🔊 #NowPlaying on #BBC6Music's #AmbientFocus

Elodie:
🎵 Vieux Silence

#Elodie

https://open.spotify.com/track/6lQZSbJnGpLzAaOmarw90t

https://ideologicorgan.bandcamp.com/album/vieux-silence

Elle a de la chance #Elodie #NOPLP

Ça pue pour #Elodie #NOPLP

Je pense qu’elle ne risque rien #Elodie #NOPLP

#SpotifyWrapped apparently I'm an #Adventurer #littlebig #enya #rigobertabandini #elisa #elodie

Since 2006, #SOPHIE is replacing #ELODIE at the 1.93-m telescope and a major upgrade, #SOPHIERed, is planned for early 2023.

#SOPHIE is able to reach a radial velocity precision down to 1m/s.

SOPHIE is also in a thermally controlled room. I'm working with this instrument since 2009 and I never had the opportunity to actually see it (only on this picture). I was able to enter the temperature-controlled room only once, to perform some test / measurements.
Maybe next year for #SOPHIERed ?

All these optical elements can now be seen on the ground floor of the 1.93-m telescope at the #HauteProvence #Observatory (🇫🇷 ). Here are a few pictures of #ELODIE I took for you.

#Astronomy #exoplanet

All these optical elements can now be seen on the ground floor of the 1.93-m telescope at the #HauteProvence #Observatory (🇫🇷 ). Here are a few pictures of #ELODIE I took for you.
.
#Astronomy #exoplanet

#ELODIE is a cross-dispersion spectrograph, meaning that the stellar light is first dispersed by a grating and then cross-dispersed by a prism. This makes spectrum to appear like a ladder (echelle in 🇫🇷 ) and not a single line spectrum. We call these kind of optical design an echelle spectrograph (see picture).

- 48 & 49: the fibers
- 38: the grating
- 42: the prism.
- 47: the CCD cooled by liquid nitrogen to -100ºC (-148°F).

Other optical elements are collimation mirrors.

The third instrumental #breakthrough was to use digital detectors (CCD) that started to be used in astronomy in the late 80's / early 90's. #ELODIE was developed in 1994 so this technology was pretty new in #astronomy. CCDs offer much more stable and precise measurements. They also have many pixels allowing to record the entire visible spectrum at once (see picture). In comparison, #CORAVEL was using a (1-px) photo-multiplicator to measure the stellar light.

The second instrumental #breakthrough for the development of #ELODIE was to install the spectrograph in a stable, temperature controlled room, to avoid any deformation of the opto-mechanical elements that lead to instrumental radial velocity variation, that we want to avoid.

The pictures below show #ELODIE, sitting on a marble table and covered to limit thermal changes in its environment.

However, in the mid-1990's when #ELODIE was developed, very few people actually managed to feed stellar light through fibers. It indeed requires a very precise optical alignment (with micro-lensing at the fiber entrance) and most attempt at the time led to low throughput. But André managed to do it, which was really an instrumental #breakthrough at that time.

We can see in this picture the same orange fibers entering the optical parts of the #ELODIE spectrograph.

To improve the radial velocity precision, #ELODIE had to be a much more stable instrument, in a temperature- and pressure-controlled environment which was not compatible with the dome.

So, André Baranne (a french astronomer at Marseille Observatory who also built #CORAVEL in 1977) suggested to use optical #fibers to feed the stellar light from the #telescope to the instrument. We can see these fibers in orange in this picture of the bonnette, mounted on the 1.93-m telescope at #HauteProvence.

The jump in precision between the #CORAVEL (300m/s) and the #ELODIE (10m/s) spectrographs was due to several achievements.

CORAVEL was mounted directly on the back of the swiss telescopes at either the #HauteProvence or #LaSilla observatories. In such case, the instrument's #optical and #mechanical components are deformed by #temperature, #humidity and the position of the telescope. Such deformation was a clear limitation to the radial velocity precision.

#ELODIE is a #spectrograph that was able to measure the radial velocity of #stars via the #Doppler effect with a precision down to about 10m/s.

It is actually the successor of the #CORAVEL spectrograph with which Michel Mayor & Antoine Duquennoy studied the population of binary stars in the #solar neighborhood. #CORAVEL had a precision down to about 300m/s which is not enough to discover (most) exoplanets.

#ELODIE is thus a super coravel.

In 1995, the swiss #astronomers Michel Mayor and Didier Queloz discovered the first #exoplanet orbiting a #Sun-like #star: 51 Peg b. For that, they received the 2019 Physics' #Nobel Prize.

This discovery opened a new field of research in #astronomy. It was based on #observations done with the 1.93m #telescope at #HauteProvence #observatory (🇫🇷 ) with the instrument #ELODIE.

Below ⤵️ is a #thread presenting this instrument who allowed the discovery of 51Peg b.

#astrophysics #Science