In the Milky Way, there may be as many as 20 billion potentially habitable planets outside our solar system (also known as ‘exoplanets’), any one of which could contain some form of life. Yet we’ve only searched 7,000 of them. As computer scientist Professor James Davenport says: “if the night sky was comparable to an ocean, we’ve only searched a hot tub equivalent.”
But how does one search an entire planet over 25 trillion miles away? The way to do so is through biomarkers; chemicals in a planet’s atmosphere – such as oxygen, ozone and methane – that can only be explained by biological processes.
With the announcement of NASA’s new telescope – the Habitable Worlds Observatory (HWO) – combing for biomarkers may now become significantly easier. The HWO will not only be more powerful and potentially bigger than the current best telescope (the James Webb Space Telescope (JWST)) but specially designed to examine evidence for life.
In August 2024 at NASA’s Goddard Space Flight Centre in Maryland, the project began ‘pre-phase A’. In Phase A, the proposed mission and system architecture will be developed – this could kick off in the next two years. However, a definitive green light for HWO is not expected before the early 2030s, with the launch unlikely before the first half of the 2040s.
The HWO and the JWST will both be in the region of space known as the L2. This area – 1.5 million kilometres away – is directly "behind" the Earth as viewed from the Sun, and is where neither the Earth nor the Sun can obstruct a telescope both visually and gravitationally. Since this area is so far away from Earth, telescope maintenance is difficult. Unlike with the JWST, engineers plan to design the HWO in such a way that it can be serviced – not by astronauts, but by robots.
Scientists have formulated four major themes for the HWO: 1) Drivers of galaxy growth, 2) Evolution of elements over cosmic time, 3) Placing the Solar System in a galactic context, and 4) Living worlds. We are one small step along the journey, but this is one giant leap towards answering the question: what’s really out there?