When the James Webb Space Telescope finally launches (late this month, if the schedule holds) it will forever change astronomy.
Assuming that its complex, month-long deployment in space works as planned, it will become the most powerful and far-seeing observatory in the sky. It will have unprecedented capabilities to probe the earliest days of the universe, shedding new light on the formation of the first stars and galaxies. And it will observe in new detail the most distant regions of our solar system.
Deep space astrophysics is what JWST was first designed for in the early 1990s, and that will be its transformative strength.
But much is also being made of what JWST can do for the study of exoplanets and some are even talking about how it just might be able to find biosignatures — signs of distant life.
While it is probably wise to never say never regarding an observatory with the power and capabilities of JWST, the reality is that it was not designed to look for the exoplanets most likely to be habitable. Actually, when it was first proposed, the observatory had no exoplanet-studying capabilities at all because no exoplanets had yet been found.
What was added on is substantial and exoplanet scientists say JWST can help advance the field substantially. But there are definite limits and finding biosignatures — life — is almost certainly a reach too far for JWST.
Astronomer Jacob Bean of the University of Chicago, who has played a leadership role in planning JWST exoplanet observations for the telescope’s early day, says that people need to know these limitations so the pioneering exoplanet science that will be possible with JWST is not seen as somehow disappointing.
As he explained, it is essential to understand that the kind of exoplanet observing that the JWST will mostly do is “transit spectroscopy.” This involves staring at a star when an exoplanet is expected to transit in front of it. When that happens, light from the star will pass through the atmosphere of the exoplanet (if there is one) and through spectroscopy scientists can determine what molecules are in that hoped-for atmosphere.… Read more