The CHEOPS space telescope launched into space at 9:54 a.m. Central on Wednesday after it had been postponed due to an issue with the launch device. The final countdown for liftoff was interrupted an hour and 25 minutes before it was scheduled to launch on Tuesday on board the Soyuz launcher.

“The Soyuz launcher and its satellite payloads were placed in a fully safe standby mode,” according to a statement by Arianespace. — Updated at 10:33 a.m. Eastern, December 18.

Original story is below.

Now is a golden era for planet discovery, unmatched by any time before it. Over the past 25 years, some 4,000 exoplanets — those planets beyond our solar system — have been discovered, and around 3,000 more are awaiting confirmation.

What’s on these planets could potentially answer astronomy’s biggest question: “Are we alone in the universe?”

The European Space Agency (ESA) is hoping to get a little closer to solving this long-standing mystery with the launch of a first-of-its-kind telescope designed to study exoplanets in detail.

Called “CHEOPS” (short for CHaracterizing ExOPlanet Satellite), the 3.5-year mission is scheduled to launch on Tuesday aboard a Russian Soyuz-Fregat rocket from Europe’s Spaceport in Kourou, French Guinea. The launch is scheduled for 3:54 a.m. Eastern time on Tuesday, December 17.

The CHEOPS launch will be livestreamed on ESA TV. Coverage begins at 3:30 a.m. Eastern time.

CHEOPS is the first mission dedicated to the study of exoplanets, providing follow-up measurements of ones that have already been discovered, and finalizing a list of potentially habitable planets.

“Cheops will take exoplanet science to a whole new level,” Günther Hasinger, ESA Director of Science, said in a statement.

CHEOPS hitched a ride on board the Soyuz spacecraft. ESA

A brief history of finding exoplanets

In 1992, astronomers Aleksander Wolszczan and Dale Frail were observing a pulsar star located some 2,300 light-years away when they discovered two planets orbiting around it. That marked the discovery of the first exoplanets, and opened up a new field of study in astronomy.

Since then, thousands of alien planets were discovered, thanks to NASA’s Kepler mission and the Transiting Exoplanet Survey Satellite(TESS) missions.

Kepler zooms in on stars to see if there are planets orbiting within their habitable zone, while TESS surveys 200,000 of the brightest stars in the sky.

What will CHEOPS will look for?

The upper composite of the Soyuz that will lift ESA’s Cheops mission into space, along with the primary passenger, the Italian space agency’s Cosmo-SkyMed Second Generation satellite, and three CubeSats – including ESA’s OPS-SAT – is hoisted on top of the 3-stage rocket at Europe’s Spaceport in Kourou, French Guiana. ESA - M. Pedoussaut

Of the exoplanets we know today, CHEOPS will be targeting gaseous exoplanets the same size as Earth, or ones that are slightly smaller than Neptune called super-Earths or mini-Neptunes.

There are around 20 Earth-sized and 34 mini-Neptunes that are potentially habitable.

Using a single camera, CHEOPS will observe the host stars of these exoplanets. The space telescope will be placed 700 kilometers above the Earth, and its camera will constantly be facing the Earth’s night side so that the Sun’s light does not interfere with its observations.

By measuring the dip in brightness of a star’s light as the planet orbits in front of it, the mission will provide a more accurate measurement of the planet’s size, as well as the composition of its atmosphere.

A planet’s atmosphere is a critical indicator of its habitability. Firstly, planets need to have an atmosphere to support life, and that atmosphere needs to be thick enough to provide insulation for the planet’s temperature.

The mission will also help scientists determine a planet’s density, using the detailed measurements of the size of the planet and combining them with information on the mass of the planet. The density of the planet provides clues for the structure and composition of the planet, whether it is rocky or gaseous.

CHEOPS will be able to identify the best candidates for future studies by missions that are scheduled to launch within the next few years. It was selected from 26 proposals in 2012.

The James Webb Space Telescope, scheduled to launch in March, 2021, will be used to search for the signatures of water and methane on exoplanets. ESA also has two upcoming exoplanet missions, Planetary Transits and Oscillations of stars Plato and Atmospheric Remote-sensing Infrared Exoplanet Large-survey Ariel, launching in 2026 and 2028.

Plato will provide accurate characterizations of an exoplanet’s host star, while Ariel will study the atmosphere of around 1,000 exoplanets.

The story was updated to reflect the delay in liftoff