Launch expected today: NASA's space telescope TESS on a search for exoplanets

It might not be any bigger than your own refrigerator, but the TESS telescope will deliver the stuff of your wildest sci-fi fantasies: Earth-sized planets by the hundreds, and all in the next two years.

The launch of Transiting Exoplanet Survey Satellite (TESS), better known as TESS, is now set for Wednesday, April 18 at 6:51 p.m. EDT. The space probe is powerful.

Its four cameras will monitor the 200,000 brightest stars in the vicinity of our sun, and, as with its predecessor telescope, Kepler, NASA scientists hope to find thousands of exoplanet candidates and to also confirm many of those as genuine.

About 300 of them, NASA estimates, may turn out to be about the size of our Earth.

Weltraumteleskop TESS

For the first time, a scientific space probe will be launched by SpaceX

For astronomers it has been incredibly difficult to find exoplanets. In contrast to the stars they circle, they do not emit their own light or radiation and usually stay in the dark – almost impossible to detect with optical telescopes.

Furthermore, being in far away galaxies, they are unbelievably tiny from the perspective of Earth.  

Such exoplanets only give a hint about their existence when they transit in front of their respective sun – from the perspective of Earth. They then cast a shadow and, for the time of their transit, the light emitted from their star gets somewhat dimmer.

The change in the light, the time it takes and the frequency with which such darkening occurs give astronomers important information that they can use to compute the characteristics of the planet: Its size its orbit and the distance from the planet. 

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Kepler 90: Nasa entdeckt acht Planeten in fremdem Sonnensystem

Kepler has found throusands of exoplanets in a tiny section of Milky Way

The predecessor

NASA already used this physical method with its satellite Kepler between 2009 and 2013. The space probe observed 150,000 stars permanently and registered the slightest light fluctuations.

The satellite focused on a rather narrow section of the Milky Way located in the constellations of Cygnus, Lyra and Draco. At the end of the three-and-a-half year mission, Kepler had found more than 5,000 new candidates for exoplanets and actually confirmed the existence of half of them.

Read more: NASA finds more Earth-sized planets that could support life

Due to technical problems, though, the Kepler mission later had to be refined. From 2014 on the spacecraft, under the mission name K2, searched through a larger section of the skies for different celestial bodies and events, such as supernova explosions, star systems, asteroids and comets.

Even then, Kepler still managed to find more exoplanets.

Now, Kepler is finally running out of fuel. This, in addition to other technical difficulties, is one of the reasons NASA opted to launch its successor, TESS.

Kepler 90: Nasa entdeckt acht Planeten in fremdem Sonnensystem

Some of the planets Kepler found - in the solar system of the same name

Small satellite, big expectations

This new satellite is expected to deliver data for two years. Its range of observation is 400 times larger than that of Kepler, and in contrast to its predecessor, TESS will not always be looking at the same section of the sky: It divides the heavens into 26 sectors. The craft will monitor each of those sectors for 27 days.

And TESS can do even more. Astronomers from universities as well as other partners have had the opportunity to list about 20,000 other celestial objects that TESS will take a look at - and about which it will deliver more up-to-date data.

At the end of this year, the European Space Agency (ESA) is planning to launch the Characterizing ExoPlanets Satellite (CHEOPS). It will be equipped with only one telescope and will be positioned in a sun-synchronous orbit, meaning that it will fly around the Earth in such a way that the sun – from the perspective of the space probe – is always in the same place.

Unlike TESS, the primary task for CHEOPS will not be to search for more exoplanets. Rather, it is going to look into already known exoplanets to measure them more precisely than ever before.

Another planet Earth?

Exoplanet Kepler-186f is located 500 light years away from us, orbiting red dwarf Kepler-186. That small sun has only about 4 percent of the energy of our sun. Kepler-186f orbits that sun at a perfectly calibrated distance: water would neither freeze nor evoporate on the planet, which is a precondition for life. But the question of whether there is water on Kepler-186f at all remains unanswered.

What does it look like?

There are no detailed pictures of exoplanets - just artistic representations like this one of Kepler-186f. But not even a drawing exists of the most recently discovered exoplanet, Kepler-438b. He orbits a sun-like star about 470 light years away from Earth and is just slightly larger than our planet. NASA published the discovery on January 6th.

Spaceship Kepler: on the hunt for planets

Spaceship Kepler has been searching for Earth-like planets since 2009. They must be located in the habitable zones of suns or sun-like stars with temperatures that could allow for life, at least theoretically. They must also consist of rock or metal compounds and have a solid surface - in contrast to gas-giants.


This artistic drawing of Kepler-62e shows a planet covered by ocean. Scientists agree that Earth-like exoplanets most likely have large oceans. The only thing known for sure: Kepler-62e is located in the constellation of Lyra, 1,200 light years away from us. And his mother star Kepler-62 has yet another earth-like planet...

The Kepler-62 brothers

Kepler-62f's diameter is 1.4 times the size of Earth's diameter. The Earth-like planet is located a bit further out in the solar-system than his larger brother Kepler-62e, which is 1.61 times as bis as Earth. Both may be suited for life. Researchers believe that the existence of rocks and water is plausible.

Orbiting two suns

Even though Kepler-16b is located at the edge of an inhabitable zone, there is most likely no life on it. This is a pity, because every morning and every evening one would be able to observe two sunrises and sunsets from there. The planet orbits two suns. Too bad Kepler-16b is most likely a Gas-planet, composed of rock and ice - not good for breathing fresh air.

The Hubble Space Telescope offers many perspectives

The Pillars of Creation are located in the Eagle Nebula about 7,000 light years away. The joint ESA and NASA Hubble Space Telescope took new pictures of the formation. This picture is taken through an infrared light spectrum. Inside the Pillars there are numerous bright stars and young stars - including entire solar systems.

Lights on!

The same picture through visible light: more fog, but also more color. Dust and gas in the pillars are pierced by radiation originating from young stars. These new Hubble Telescope pictures enable researchers to monitor changes in the formation over a longer period of time.

A star is born

NGC 4102 is a LINER-Galaxy : a Low-Ionization Nuclear Emision-line Region. This means it's emitting ionized radiation, like roughly one third of all galaxies. In its center, there is a sun-burst region, where young stars seem to be born. It has a diameter of about 1,000 light years. Scientists don't understand the exact processes in the center yet.

A Messier cluster

This cluster of stars, located in the northern part of the Hercules formation, is called Messier 92. In dark nights with clear skies, we can see it from Earth with bare eyes. The cloud includes roughly 330,000 stars, most of which consist of hydrogen and helium. Heavier elements like metalls seem to be very rare there.

The best view of Andromeda

The original of this photo of the Andromeda Galaxy is 1.5 billion pixels in size - the most detailed picture ever taken of that galaxy. It includes 100 million stars and thousands of star clusters. To watch it in its entire beauty, one would need 600 HD-TV-screens. The ends of the picture are 40,000 light years apart.

Better than Star Wars

Just as the new episode of Star Wars hits cinemas, space telescope Hubble took this picture of a cosmic lightsaber. The celestial structure is located about 1,300 light years away. And that's exactly what it is: the birth of a star system, including some interstellar dust. The space telescope takes breathtaking pictures. Here are some more…

Eyes in space

Since 1990, the king of all space telescopes has been orbiting earth at a speed of over 17,000 mph (27,000 km/h) and an altitude of 340 miles. Hubble is 11 meters long and weighs 11 tons, making it comparable in weight and size to a school bus.

Scoping out cosmic bubbles

Hubble has helped us understand the birth of stars and planets, approximate the age of the universe and examine the nature of dark matter. Here we see a gigantic ball of gas created by a supernova explosion.

Mystical being

The Carina Nebula is one of the most significant open clusters of stars in our galaxy. The colors on this breathtaking photograph aren't only pretty to look at, however; they also reveal much about the chemical makeup of the gases.

Fleeting colors

Different gases emit all kinds of different colors. Red, for instance, is a sign of sulfur. Green is hydrogen. And blue is oxygen.

Hubble needs glasses

The first pictures Hubble sent back were a catastrophe, however, because its main mirror had been ground to the wrong shape. In 1993, Space Shuttle Endeavor took experts to Hubble to fix the problem, giving it a pair of glasses. That was just one of five updates the telescope has received over the years, the last one coming in 2009.

Space kindergarten

Hubble took this amazing picture in December 2009. The blue dots are very young stars, just a few million years old. This kindergarten of stars is found in the Large Magellanic Cloud, a nearby galaxy, and a satellite of our Milky Way.


How about this snapshot from space? Nobody really knows what exactly Hubble had in its lense here, but that doesn't mean the shot is any less stunning. This image is just one of over 30,000 that Hubble has captured for the ages.

Divine Sombrero

This virtually transcendent photograph is - like most Hubble images - a composition of many single shots. The Sombrero Galaxy is an unbarred spiral galaxy in the Virgo constellation and is located a mere 28 million light years from the earth.

Hubble in the flesh

The telescope was named after the American astronomer Edwin Powell Hubble (1889-1953). He was the first person to observe that the universe is expanding, and with it he paved the way for our current cosmological understanding of the Big Bang as initiator of the universe.

The Pillars of Creation

These column-shaped structures are found in the Eagle Nebula, around 7000 light years away from earth. They were documented by Hubble and have received worldwide recognition under the name "Pillars of Creation."

Space smiley

At 25 years and counting, we can all be happy that Hubble will continue to provide us with fascinating images from space. This, by the way, is Hubble's latest creation - a space smiley! The easy explanation? It was made by bending light.