TESS : the Ultimate Exoplanets Hunter !

What if the next life-hosting and Earth-like planet would be discovered within the upcoming 2 years ?

Although the answer is not as obvious as we could imagine, it remains not impossible either, thanks to the very recent launch of the space mission TESS by NASA.

The exoplanet hunting has never been at the heart of our preoccupation as today !

How did exoplanets survey begin ?

Since the discovery of the first exoplanet in 1992 (named Poltergeist and orbiting around a Pulsar), mankind just became aware that the Universe, despite its immensity, could hide other planets, other solar systems and even potentially other Earths, where proliferation of life could be possible.

Before the birth of space telescopes, these planets orbiting foreign stars located inside our Galaxy were mainly discovered in few quantity, using ground-based telescopes only.

We had to wait the 2000s for the famous Hubble Space Telescope to be used for the first time as a tool looking for exoplanets. Its primary task was about to confirm the presence of exoplanet which had been previously discovered. Later on March 22, 2005 NASA announced that its Spitzer telescope performed the first direct exoplanet observation ever. Nonetheless, the performances and availability of the Hubble and the Spitzer telescopes do not make them suitable enough to reach high-expected results needed for this kind of research.

NASA therefore decided to launch a space mission entirely dedicated for exoplanets hunting : Kepler.

The desire to go further

If the number of discovered exoplanets as of May 2018 reached 3767, it is mainly thanks to Kepler mission which counts 2512 confirmed exoplanets for itself. Definitely the biggest amount of exoplanets for a single mission.

After 9 years of commission, the Kepler’s end of mission is coming and it is currently transmitting its last data before NASA will decide to shut it down forever. However, one the main drawbacks remains its narrow area of monitoring, which was not as wide as what the next generation TESS will perform.
It is time now to dive in depth into TESS scientific and technical details.

TESS : a prolific mission ahead

The Transiting Exoplanet Survey Satellite (or TESS) was launched on April 18, 2018 by a SpaceX Falcon 9 rocket.
TESS is not a single space telescope but actually a 4-wide-view-telescope-embedded satelliteDuring its mission estimated to last two years, scientists want to monitor more than 200 000 bright stars and detect potential change of luminosity caused by an exoplanet crossing the disk of its host star. This detection method of exoplanets is a so-called “transiting method”.

So, the ambition of TESS is to unveil at least 20 000 exoplanets whose 5 % of them would be similar to the Earth, in term of size.

 This ambition would be never fulfilled without scanning the whole starry sky. One of the main features of this space telescope is indeed the ability to use four great-aperture telescopes (f/1.4), covering a wide zone of 24×24 degrees each. Consequently, the total zone used by TESS is 400 times bigger than the one used by the Kepler telescope !

How does TESS detect exoplanets ?

Nearly the whole sky will be observed and divided into North-South hemispheres which count 13 zones each. TESS will perform a single zone monitoring within 4 weeks. It amounts to saying that the 26 zones will be entirely monitored after 2 years.

The orbit where the telescope has been moved on is strongly elliptical, with a 14 days period. Every nearest approach of the Earth, TESS will transmit systematically the data acquired during its 2-week-long measurements. As a matter of fact, these data are mostly images taken by the four CCD sensors of 16.8 Mega pixels each. They are extremely relevant because they contain all the photometric properties of the stars, namely their light variation throughout the time.

From these measurements, not only the size of the exoplanets could be deduced but also the orbital parameters such as their orbital period, distance from their host star… An estimation of their mass could only be done by the biggest ground-based observatories.

Catching some exoplanets using your own telescope is not science-fiction !

Tough, observing exoplanets is not only limited to scientific and professional research. Using less top-of-the-range telescopes, affordable to amateurs, it is actually possible to detect some exoplanets with the transiting method like TESS. A telescope which features a 400 mm minimum focal length, a diameter from 80 mm and a camera – the same specs as the Stellina telescope for example) allow you to make your first lights in exoplanet hunting.

As you might probably guess, TESS is bound to obtain more sensitive light curves and has a far higher efficiency. Its scientific mission is expected to start on mid-June, few times after it will reach its work-orbit.

Guillaume Doyen


The most beautiful destinations to watch the stars

Summer is coming and you’re wondering where you could spend your next holidays. Why not run away the endless activity of cities or crowded tourist destinations to reconnect with nature and the starry sky? When was the last time you saw the Milky Way or a shower of shooting stars? Maybe a long time (and for some children, maybe never!). The Vaonis team wanted to share with you its list of favorite places around the world for stargazing.

Désert Atacama

Chile – The Atacama Desert

This is probably the most favorite destination of all amateur astronomers from all over the world. The Atacama Desert, located in the northern part of Chile in South America, is one of the driest regions in the world and covers more than 100,000km² (40,500 sq. mi.). Astronomical research centres like NASA have established there to benefit from the purity and clarity of the starry sky. You will be able to visit for instance the La Silla Observatory, the Alma Observatory with its giant antennas or the Cerro Paranal Observatory which hosts the Very Large Telescope. The landscapes of the Atacama desert are breathtaking: turquoise lagoons, salty deserts, volcanoes and geysers, mountains and valleys…  The biodiversity will surprise you by its extraordinary variety of life, despite the extreme weather. Day or night, you will be amazed by the beauty of the Atacama desert landscapes.

Iceland aurora

Iceland – Its Northern Lights

More accessible than Chile if you live in Europe, Iceland also offers breathtaking landscapes. The destination is particularly appreciated for the observation of aurora borealis, but you will need to invest in warm clothes because you will have to be patient until you manage to see northern lights. Iceland also offers varied and beautiful wild landscapes: you can hike among glaciers, volcanoes, geysers, hot springs and lava fields, but the weather is difficult to predict.
The good thing in Iceland is that you will not have to drive several hours before enjoying a sky and air free from pollution (there’s only 330 000 inhabitants in Iceland, the population of a small town in France!).
Be careful, the summer days are very long there. At the June solstice, locals can observe the sun for up to 24 hours… It is called the Midnight Sun. To enjoy the beauty of the starry nights and the auroras, you will have to wait until the end of August to visit the island (until the end of April). In winter, the nights are very long (only 5 hours of sunshine in December).

Stargazing in Canary Island


Spain – Canary Islands

Spanish archipelago located in the Atlantic near Morocco, the Canary Islands are also easily accessible for Europeans, with the difference that this destination benefits from a more stable weather (320 days of sun/year). The archipelago is composed of 7 islands, two of which are very appreciated by starry sky lovers, amateurs and professionals alike:
– Tenerife: its national park, located at an average altitude of 2000m, and its Teide volcano have been awarded with the “Starlight Destination” label. Depending on the night, you can observe up to 83 of the 88 recognized constellations. El Palmar viewpoint , located further north of the island, will allow you to enjoy a night under the stars and observe all the beauty of the Milky Way.
– La Palma: here you can find the Roque de los Muchachos Observatory, one of the most important in the world, belonging to the Canary Islands Astrophysical Institute (IAC). Depending on the weather conditions, you will be able to observe a surprising cloud formation: the sea of clouds.
Guided tours are organized in several observatories of the archipelago, where you will be accompanied by astronomy enthusiasts who will share with your their passion of the universe.

Mauna Kea Observatories

Hawaï – Mauna Kea

Mauna Kea is located on the American island of Hawaii, in the middle of the Pacific Ocean. It is a volcano culminating at more than 4 000m altitude, which hosts several observatories and the largest and most powerful telescopes in the world (it will host one of the Extremely Large Telescopes: the Thirty Meter Telescope). It is one of the most important scientific observation sites in the world. Thanks to its geographical situation and climate (little humidity), the island offers an exceptional night sky, very dark with a very pure air, ideal conditions to observe the stars.

Pic du Midi Stellina

France – The Pic du Midi

Located in the Pyrenees mountains, between Spain and France, the Pic du Midi reaches an altitude of 2800m and hosts an astronomical and meteorological observatory. Because of its proximity to our offices, it remains one of the favourite places to observe the stars. Accessible using the unique aerial tramway, the site offers an unobstructed view on the mountain range or on the sea of clouds that occasionally forms. The observatory offers stays, guided tours and workshops led by astronomers and scientists. The Pic du Midi has obtained the Dark Sky Reserve label enabling it to enhance and protect its sky as a natural and cultural heritage. Thanks to its involvement and actions (public education, awareness of light pollution, responsible lighting), the site offers exceptionally pure nights. Today, it is the only Dark Sky Reserve labelled by the International Dark-sky Association in France!


Path Of Totality, Umbra And Penumbra

Solar eclipses, due to the conditions they need to bring together, are a rare phenomenon. On August 21, 2017 will be a solar eclipse visible from the United States that the team of Vaonis won’t miss for anything and who will record the event with its smart telescope Stellina. While waiting for the event, we give you some explanations on this singular astronomical phenomenon. After talking about the conditions of observation of an eclipse, here is some information about the different zones from where you can watch an eclipse.

The path of totality

Solar eclipses are observable in the shadow zone created by the Moon’s occultation of the Sun. In the case of a total eclipse and only in this one, the shadow zone where it is possible to observe this phenomenon of total eclipse is called “path of totality“.

Bande de totalité éclipse Etats-Unis 2017

Author: Wolfgang Strickling

The shadow of the Moon moves from West to East on Earth. The projection of its shadow on the Earth all along its trajectory is called “shadow band“. The width of the shadow band varies depending on the apparent size of the Moon and can reach up to 250 kilometers if the apparent diameter is important.

View solar eclipses from the path of totality

From the path of totality, it is possible to correctly observe the five phases of a total solar eclipse. At first, we observe the first contact between the Sun and the Moon when the two contours touch for the first time. Then, the Moon will continue its progression until the second contact, when the Sun will have completely disappeared to finally reach the maximum of the eclipse at the level of the perfect alignment of the two bodies. The third contact will then be observable soon after and will be the last moment when the Sun will be completely obscured by the Moon. At the end of the eclipse, we observe the fourth and last contact before it finally ends.

Phases of solar eclipse


Solar eclipse penumbra

Si le phénomène d’éclipse totale n’est lui visible que depuis la bande de totalité, l’éclipse peut quant à elle être observée depuis une zone plus large. De part et d’autre de la bande de totalité, il est possible de constater un phénomène de pénombre. Pour les personnes ne pouvant pas se rendre au niveau de la bande de totalité, se trouver dans la zone créée par le cône de pénombre peut-être une alternative pour observer non pas une éclipse totale mais une éclipse partielle où seulement une partie du soleil serait cachée par l’un des côtés de la Lune.
If the phenomenon of total solar eclipse is only visible from the path of totality, the eclipse can be observed from a wider area. On both sides of the totality band, it is possible to observe a phenomenon of penumbra. For people who are not able to travel somewhere inside the path of totality, being in the zone created by the penumbra may be an alternative to observe not a total eclipse but a partial eclipse where only a part of the sun would be hidden by one side of the moon.


Duration And Frequency Of Solar Eclipses

Solar Eclipse: Moon hiding the SunSolar eclipses, due to the conditions they need to bring together, are a rare phenomenon. On August 21, 2017 will be a solar eclipse visible from the United States that the team of Vaonis won’t miss for anything and will record with its Stellina smart telescope. While waiting for the event, we give you some explanations on this singular astronomical phenomenon. After talking about the conditions of appearance of an eclipse in a first article, here is some information on their duration and frequency.

How many solar eclipses per year

In 1000 years, there are 840 partial eclipses, 791 annular eclipses, 635 total eclipses and 114 hybrid eclipses between the Earth and the Moon. This makes it possible to estimate the appearance of an eclipse, any type combined, 2-3 times a year and a total solar eclipse every 3 years. The Great American Eclipse of 2017 is the second and last eclipse to occur in 2017.

Why eclipses do not occur at each New Moon?

The New Moon is the phase of the lunar cycle during which the Moon is found between the Sun and the Earth. It occurs every 29.5 days. During this phase, the Moon is not visible in the night sky. This astronomical phenomenon is therefore similar to that of a solar eclipse. However, for an eclipse of the sun to occur, the Moon must be perfectly located on a line that runs between the center of the Sun and the Earth, an occasion that rarely occurs.

Next total eclipse in France

To enjoy the next total solar eclipse in France, we will have to be patient! Indeed, the next total eclipse will occur only in 2081.

For people who don’t want to wait that long, the next total eclipse closest to France will be visible from Spain or Iceland and will take place on August 12, 2026. You can see on the image, made by Xavier Jubier ( the trajectory that will follow this eclipse.Eclipse Espagne 2026

Maximum duration of a solar eclipse

Currently, a total solar eclipse can not exceed 7 minutes and 32 seconds. This maximum duration may vary slightly over a millennium and the trend is currently on the decline: the maximum duration is decreasing. During the 8th millennium, the longest total solar eclipse will last at most 7 minutes and 2 seconds theoretically.

Regarding the solar eclipse of the United States of August 21, 2017, you will need to go to Kentucky to enjoy the longest of the event: the eclipse will last 2 minutes 40 seconds.


The Best Places To Watch The 2017 Total Solar Eclipse

If the total solar eclipse of August 21, 2017 is observable from the United States, all the places do not allow to observe the phenomenon in the same way. So, we have selected some of the best places based on weather forecasts, light pollution, the duration of the entire eclipse phase and the activities around the event.

Madras, Oregon

Duration of the totality phase estimated at 2 minutes 4 seconds from 10:19 (local time). If some clouds are expected on the coast, the interior of the territory should benefit from ideal weather conditions.

St. Joseph, Missouri

Duration of the totality phase estimated at 2 minutes 39 seconds from 13:06 (local time). One of the places where the duration of the eclipse will be the longest. A meeting is being held at Rosecrans Memorial Airport where it will be possible to listen to speakers and use the solar telescopes provided.

Madras OregonSnake River Valley, Idaho

Duration of the totality phase estimated at 2 minutes 18 seconds from 11:33 (local time). It is a valley composed of lava fields and farms. The area is known for its very good weather.

Carbondale, Illinois

Duration of the totality phase estimated at 2 minutes 41 seconds from 13:20 (local time). This is one of the place where the solar eclipse will last “long” but there is a risk of clouds to take into account.

Casper WyomingCasper, Wyoming

Totality phase estimated to last 2 minutes 26 seconds from 11:42 (local time). A place that offers good weather forecasts.

Hopkinsville, Kentucky

Duration of the totality phase estimated at 2 minutes 41 seconds from 13:24 (local time). If you want to observe the eclipse while enjoying celebration and festivities (Eclipse Con, Summer Salute …), this is the place to be!

Sandshills NebraskaSandhills of western Nebraska

Duration of the totality phase estimated at 2 minutes 30 seconds from 11:49 (local time). They expect good weather conditions for the eclipse. This is a very appreciated place for night stargazing with magnificent views on the Milky Way, thanks to the blackness of its sky.

Nashville, Tennessee

Totality phase duration is estimated at 1 minute 57 seconds from 13:27 (local time). The perfect opportunity to view the solar eclipse while enjoying the a musical journey in the birthplace of country music.

Great Smoky Mountain National Park

Totality phase should last 1 minute 17 seconds starting at 2:35 pm (local time). For a shorter observation and an entirely different experience: you will be able to see the shadow of the moon running through the landscape.

Columbia USColumbia, South California

Duration of the totality phase estimated at 2 minutes 30 seconds from 2:43pm (local time). The most accessible place with the possibility to observe the longest duration of the eclipse from the beach.


Those who do not have the chance to travel to enjoy the total solar eclipse will be able to follow the entire Eclipse live thanks to Cyril, founder of Vaonis, who will capture every moment with Stellina, from Madras, Oregon.


Tips To View A Solar Eclipse

Eclipse glasses you will wear

Lunettes eclipse

Observing the sun with the naked eye is prohibited so as not to damage the retina. During a solar eclipse, it is therefore recommended to use solar filters sold most often in the form of cardboard glasses.

During total solar eclipses, it is possible to remove your eclipse glasses during the whole phase (when the lunar disc completely covers the solar disk) to enjoy the natural beauty of the phenomenon. Be careful, it will only last a few minutes!

These solar eclipse glasses are specially designed for sun observation. They must meet an international ISO standard or have the CE mark, which certifies that glasses are suitable for direct observation of the sun, such as during an eclipse.

Beware of fake and misleading advice! Do not use X-rays, slides or multiple layers of sunglasses, as you may sometimes hear. If your solar eclipse glasses are damaged or scratched, it is recommended to use another pair.

Solar filter you will use

Filtre solaireNever look at the sun and an eclipse through a camera, a telescope, binoculars or other optical instruments, even with sunglasses. Again, damage to your eyesight (and your device) could be very serious! A famous saying expresses it well, “we can observe only 2 times an eclipse without filter, once with the right eye, once with the left eye” … There are solar filters specific to astronomical instruments that filter the ultraviolet and infrared rays and reduce the brightness of the sun entering the eye or the sensor. As with the naked eye, the solar glasses can be removed during the brief period of totality, giving you the opportunity to capture every detail of this unique moment. If you plan to immortalize this phenomenon using a camera, we advise you to train, for example on the moon, to optimize the setting of your device.

In advance you will prepare

Solar eclipses are popular astronomical phenomena that attract many curious but also true enthusiasts. These eclipse hunters can book their trip more than a year in advance and travel more than two weeks before the eclipse to the best viewing spots to get the best location. As a result, the best locations become crowded very quickly. Depending on the popularity of the observation point, prepare your schedule in advance. Also follow the weather forecast! You just have to hope that the sky is perfectly clear.

Stellina solaire

Stellina, a solar version in project

A version of Stellina designed for solar observation is being studied for future development. It will work on the same principle as the first telescope designed by Vaonis: an all-in-one telescope, sleek and remote controlled using a mobile device to photograph the sun. This next version will only be used for the observation of the sun and will let users capture solar eclipses or sun eruptive prominences, becoming the first all-in-one telescope dedicated to solar photography. We’ll give more details soon!

Photos credit: Astroshop – Vaonis

What's a solar eclipse

What Is A Solar Eclipse?

Solar eclipses, due to the conditions they need to bring together, are a rare phenomenon. On August 21, 2017 will be a solar eclipse visible from the United States, an event that the team of Vaonis won’t miss for anything and will record with its smart telescope Stellina. While waiting for the event, we give you some explanations on this singular astronomical phenomenon.

An eclipse occurs when one astronomical body is hidden behind another. In astronomy this can happen on different occasions:

Solar eclipse

This is the most impressive phenomenon. When the Moon is between the Earth and the Sun, part of our planet is in the shadows. Formerly feared and inexplicable, solar eclipses are today perfectly understood and can even be predicted thousand years in advance!

Eclipse lunaireLunar eclipse

This phenomenon occurs more often than solar eclipse because the Earth has a larger size and is more likely to obscure the moon. Some of you may have noticed that when the lunar eclipse occurs, the moon does not disappear entirely. This is because of the Earth’s atmosphere that acts like a lens and deviate the rays of the sun. The most deviated color is red, that’s why the moon looks sometimes red or orange.

Total or annular solar eclipse?

Depending on the apparent diameter of the Moon and the Sun, a solar eclipse can be total or annular. The orbits of the planets are not perfectly circular but rather describe an elliptical movement. As a result, depending on the position in their orbit, the Moon will have an apparent size different from the Sun:

Eclipse solaire

    • when the apparent diameter of the moon is nearly equivalent to the Sun, we can observe from the Earth a lunar disc which covers the solar disk, plunging some regions of the world into darkness. It’s a total eclipse.
    • when the apparent diameter of the moon is slightly smaller than that of the sun, the moon does not cover the entire sun, drawing a ring of fire around the lunar disc. It’s an annular eclipse.

Do not mix diameter and apparent diameter
The diameter corresponds to the intrinsic dimension of the object. The apparent diameter varies according to the place where an object is observed. For example, the stars visible at night have a diameter often similar to the sun, yet they appear very small because of their far distance. The eclipses occur thanks to a nice coincidence, the moon is 400x smaller than the sun but is also 400x closer to us. It is for this reason that these two bodies have a very similar apparent diameter.

The Great American Eclipse 2017

On August 21, 2017 will be the second solar eclipse of the year and the first total solar eclipse in the United States since the beginning of the 21st century. This is a highly expected event for amateur astronomers but not only. Millions of Americans will attend this natural phenomenom and have already bought their solar glasses! Even outside of the United States, eclipse hunters and sky lovers have booked their trip to the U.S. more than one year in advance to attend this spectacular event.