A new exoplanet mission took to the skies early this morning (Dec. 18), on a quest to better understand the metrics of distant worlds.

The European probe, called Characterizing Exoplanet Satellite (CHEOPS) , lifted off atop a Soyuz rocket from Guiana Space Center in Kourou, French Guiana, at 3:54 a.m. EST (0854 GMT; 5:54 a.m. local time). The dazzling predawn event drew a flock of spectators.

The Soyuz successfully deployed CHEOPS into Earth orbit about 2.5 hours after liftoff, representatives of France-based launch provider Arianespace said.

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Several other satellites are riding on the rocket as well. All were deployed as planned by about 4 hours minutes after launch, making Arianespace's ninth and final mission of 2019 complete.

A Soyuz rocket carrying the CHEOPS exoplanet satellite and several other payloads lifts off from French Guiana on Dec. 18, 2019. (Image credit: ESA via Twitter)

CHEOPS' main mission involves examining bright, relatively nearby stars that astronomers know have planets orbiting them. Watching known planets orbit their stars is important to better understand certain characteristics, such as how long their orbits are and how big the planets are. Astronomers are interested in learning about the habitability of distant worlds, which depends in part on if a planet is rocky (closer to Earth's size) or gaseous (closer in size to Uranus, Neptune, Saturn or Jupiter).

CHEOPS will "make high-precision observations of the planet's size as it passes in front of its host star," European Space Agency (ESA) officials wrote in a mission description . "It will focus on planets in the super-Earth to Neptune size range, with its data enabling the bulk density of the planets to be derived — a first-step characterization towards understanding these alien worlds."

CHEOPS will do this via the "transit method," measuring how much a host star dims when a planet crosses its face from the probe's perspective. This is a tried and true exoplanet technique; it was also used by NASA's pioneering Kepler space telescope, for example, and is currently employed by the American space agency's Transiting Exoplanet Survey Satellite (TESS).

CHEOPS is a small-class mission; its price tag is about 50 million euros ($55.7 million at current exchange rates).

Four other satellites joined CHEOPS on its ride into space. They are:

The COSMO-SkyMed Second Generation satellite, an imaging craft for the Italian Space Agency and Minister of Defence;

ANGELS (Argos Neo on a Generic Economical and Light Satellite), for the French national space agency (CNES), which will study Earth's environment from orbit;

EyeSat, a satellite for CNES. It will study astronomical phenomena such as our own Milky Way galaxy and the zodiacal light, the latter of which is thought to be reflected light from dust and ice particles that shows up in dark skies.

OPS-SAT, an experimental satellite for ESA's mission control. This satellite will allow controllers to test out new techniques (such as for navigation) in a low-risk environment, since this satellite is dedicated to testing and trying things out. OPS-SAT could generate better mission operations for future satellites, ESA officials have said.

This morning's launch was originally supposed to happen yesterday (Dec. 17), but technical issues with the rocket caused a one-day delay.

Editor's note: This story was updated at 11:30 am ET with the news of the satellites' successful deployment into Earth orbit.

Follow Elizabeth Howell on Twitter @howellspace . Follow us on Twitter @Spacedotcom and on Facebook .