An illustration of TESS in front of a lava planet orbiting its host star. TESS is expected to identify thousands of potential new planets for further study and observation.

Image Credit: NASA/GSFC.

A new voyage is hopefully setting sail tonight; one that could lead to the discovery of many new worlds, some of which may even harbor life. Guided by the moon and pointed toward the stars, the goal of TESS —the Transiting Exoplanet Survey Satellite—is to identify rocky planets around nearby stars by detecting and analyzing distinctive dips in starlight.TESS is a scout, equipped with four high-tech cameras to systematically capture images of 200,000 of the Milky Way's stars over the next two years. For each target, TESS will create a kind of flip-book of images that will tell the story of how the star’s brightness changes over time. In these images, astronomers will search for the slight changes in brightness that happen when a planet passes between its home star and TESS's lenses. The project is led by astronomers at the Massachusetts Institute of Technology, and managed by NASA’s Goddard Space Flight Center.Most of the exoplanets we know about today were identified by Kepler , a planet-hunting mission carried out by the Kepler spacecraft. Although Kepler and TESS are both spacecraft searching for exoplanets, TESS will explore a region of the sky about 350 times larger than Kepler, and will focus on stars that are brighter and closer to us. This last part is important: TESS is keeping a special eye out for rocky-looking planets (rather than gaseous ones like Jupiter or Saturn), with the ultimate goal of allowing astronomers to follow up on promising leads with telescopes that can tell us more about the planets—something that isn’t really possible with the Kepler-identified planets.By finding exoplanets with TESS and investigating them with other telescopes, astronomers hope to identify rocky planets existing in the habitable “Goldilocks zone” of a star, where the conditions are just right for supporting life. In addition, they hope to explore the atmospheres of these planets through spectroscopy , and search for evidence of life. TESS’s search will cover 85% of the sky, focusing on the southern sky during its first year and the northern sky during the second year.TESS's launch was originally scheduled for yesterday, but was rescheduled for tonight after weather concerns put the safety of the launch into question. Missions like this have to be timed to the minute—the rocket has to be activated within a thirty-second window to get into the right orbit—and if the mission crew isn't sure that the payload will make it safely to space, things have to be called off until conditions improve. With any luck, after launching into space from Cape Canaveral on a SpaceX Falcon 9 rocket tonight, TESS will receive a gravitational slingshot assist from the moon before eventually settling into an orbit designed specifically for this mission , one that's never been used before. The orbit is highly elliptical and has a period of 13.65 days. This unique orbit keeps the spacecraft away from areas of high radiation, maximizes the amount of sky it can observe, and keeps it very stable.Seeing a rocket launch live is an incomparable experience, but most of us obviously won't be able to make it to Cape Canaveral to send TESS off in person. Fortunately, NASA's got our backs: you can watch a live stream of the launch right here!In addition to taking multiple up-close-and-personal images of each target star, TESS will take images of large areas of the sky every 30 minutes—images that could capture asteroids, supernovae, or other astronomical objects that move more quickly or have a shorter lifespan than the background stars.What will TESS discover? You can see some imaginative guesses from members of the public at the Fly your Exoplanet webpage, and even submit your own . While it’s fun to try and imagine, the reality is that TESS will probably discover things we can’t even predict. Zooming in on the new worlds and other objects of interest that TESS finds will occupy astronomers—and probably imaginations—for many years to come.