NASA has started planning its next big project, the space-based Habitable Worlds Observatory. This ambitious mission aims to search for signs of life on planets orbiting other stars, using a powerful telescope and a starshade that blocks the glare of the host stars.

The HWO is one of four concepts that NASA is considering for its next flagship mission, which is expected to launch in the 2030s. The other three are the Lynx X-ray Observatory, the Origins Space Telescope, and the Large UV/Optical/IR Surveyor. NASA will select one or two of these concepts for further development in 2024.

The Habitable Worlds Observatory (HWO) is a proposed mission concept that would consist of two spacecraft: a 4-meter telescope and a 52-meter starshade. The telescope would observe the light from distant planets, while the starshade would fly information with it, blocking the light from the parent stars. This would allow the telescope to detect the faint signals of the planets’ atmospheres, which could reveal clues about their habitability and potential biosignatures.

The HWO would use a technique called spectroscopy to analyze the light from the planets. Spectroscopy is the study of how light interacts with matter, and it can reveal information about the chemical composition, temperature, and pressure of a planet’s atmosphere. By comparing the spectra of different planets, scientists could identify which ones have Earth-like conditions, such as liquid water, oxygen, and ozone.

The HWO would be a revolutionary instrument that would advance our understanding of the diversity and evolution of planetary systems. It would have a primary mirror with a diameter of 15 meters, which is about five times larger than the Hubble Space Telescope. This would allow it to collect more light and resolve finer details on distant worlds.

The HWO would focus on planets in the habitable zone of their stars, which is the range of distances where liquid water could exist on the surface. The habitable zone depends on the size and brightness of the star, as well as the planet’s orbit and rotation.

The HWO would target planets around sun-like stars, as well as smaller and cooler stars called M dwarfs. M dwarfs are the most common type of star in our galaxy, and they host many planets, some of which are in the habitable zone.

The HWO would be a groundbreaking mission for astrobiology, the study of life in the universe. It would be able to detect biosignatures, which are features in a planet’s atmosphere that indicate the presence of life. For example, oxygen and methane are biosignatures on Earth, because they are produced by living organisms and are unlikely to exist together without life. The HWO would also be able to measure other factors that affect habitability, such as climate, weather, seasons, and geology.

The HWO would use a technique called coronagraphy to block out the glare of the host stars and reveal the faint light reflected by their planets. It would also use a technique called spectroscopy to analyze the chemical composition of the planetary atmospheres and look for clues of life, such as oxygen, methane, and water.

The HWO would aim to survey hundreds of exoplanets, ranging from Earth-sized rocky worlds to giant gas planets. It would focus on planets in the habitable zone, or the region around a star where liquid water could exist on the surface. It would also look for planets with moons, rings, or magnetic fields that could enhance their habitability.

The HWO would complement other missions that are currently studying exoplanets, such as the Transiting Exoplanet Survey Satellite (TESS) and the James Webb Space Telescope (JWST). TESS is finding thousands of new exoplanet candidates by detecting their transits, or dips in brightness when they pass in front of their stars. JWST, which is scheduled to launch later this year, will observe some of these planets and measure their temperatures, pressures, and weather patterns.

The HWO is an ambitious and visionary project that would open a new window into the cosmos. It would inspire generations of scientists and explorers to pursue the quest for life beyond Earth. It would also challenge us to reflect on our own place and role in this vast and wonderful universe.

The HWO is still in the early stages of development, and it faces many technical and financial challenges. The mission would require precise engineering and coordination between the telescope and the starshade, as well as a large budget and a long duration. However, if successful, the HWO would revolutionize our understanding of our place in the cosmos, and answer one of the most profound questions in science: Are we alone?