Science With the Webb Space Telescope – What Questions Will It Answer?

Webb Space Telescope adjusting orientation. Credit: NASA’s Goddard Space Flight Center

Webb’s science goals cover a very broad range of themes, and will tackle many open questions in astronomy. They can be divided into four main areas:

Key questions: Where and how do planetary systems form and evolve?

Thanks to the rapidly evolving field of exoplanet studies – planets beyond our Solar System – Webb will be able to contribute to key questions such as: is Earth unique? Do other planetary systems similar to ours exist? Are we alone in the Universe?

Exoplanet mission timeline. The first discoveries of exoplanets in the 1990s, by ground-based observatories, completely changed our perspective of the Solar System and opened up new areas of research that continues today. This infographic highlights the main space-based contributors to the field, including not only exoplanet-dedicated missions, but also exoplanet-sensitive missions, past, present, and future. Credit: ESA

Webb will study in detail the atmospheres of a wide diversity of exoplanets. It will search for atmospheres similar to Earth’s, and for the signatures of key substances such as methane, water, oxygen, carbon dioxide, and complex organic molecules, in the exciting hope of finding the building blocks of life. In this way, Webb will complement ESA’s Atmospheric Remote-sensing Infrared Exoplanet Large-survey (Ariel), a space telescope that will study what exoplanets are made of, how they formed, and how they evolve.

Closer to home, Webb will also study the outer planets in our own Solar System. Many exoplanets resemble Neptune and Uranus, thus studying planets in our own solar neighborhood can provide new insights for better understanding planetary formation in general.

Key questions: How and where do stars form? What determines how many of them form and their individual masses? How do stars die and how does their death impact the surrounding medium?

Artist impression of some possible evolutionary pathways for stars of different initial masses. Some proto-stars, brown dwarfs, never actually get hot enough to ignite into fully-fledged stars, and simply cool off and fade away. Red dwarfs, the most common type of star, keep burning until they have transformed all their hydrogen into helium, turning into a white dwarf. Sun-like stars swell into red giants before puffing away their outer shells into colorful nebula while their cores collapse into a white dwarf. The most massive stars collapse abruptly once they have burned through their fuel, triggering a supernova explosion or gamma-ray burst, and leaving behind a neutron star or black hole. Credit: ESA

Stars transform the Universe’s simple elements into heavier elements and, through supernova explosions, spread them throughout the cosmos. Observing in the infrared part of the spectrum, Webb will be capable of peering through the dusty envelopes around new-born stars. Its superb sensitivity will also allow astronomers to directly investigate faint protostellar cores — the earliest stages of star birth.

Webb will study brown dwarfs, dim objects with masses in between those of a planet and a star that are not themselves massive enough to start thermonuclear reactions and become fully fledged stars. Webb will determine how and why clouds of dust and gas collapse into stars, or become gas giant planets or brown dwarfs.

Webb will also see the most massive stars explode as supernovae and leave behind more clouds of dust and gas, along with the precious heavy metals that enrich the cosmos to form new generations of stars.

Key questions: What did the early Universe look like? When did the first stars and galaxies emerge?

The Hubble Ultra Deep Field of galaxies. A new study of the star formation activity in 179 of the galaxies in this image including many dating from about six billion years ago confirms an earlier puzzling result: lower mass galaxies tend to make stars at a rate slightly slower than expected. Credit: NASA, ESA, and S. Beckwith (STScI) and the HUDF Team

For the first time in human history we have the opportunity to directly observe the first stars and galaxies forming. Webb’s infrared vision makes it a powerful time machine that will peer back over 13.5 billion years, pushing beyond the limits of Hubble’s “deep fields” that showed us young galaxies when they were only few hundred million years old and were small, compact, and irregular. Webb’s infrared sensitivity will not only look back further in time but will also reveal dramatically more information about stars and galaxies in the early Universe. While Hubble looked at ‘toddler’ galaxies, Webb will see the ‘baby’ phase!

Webb’s data will also answer the compelling questions of how black holes formed and grew early on, and what influence they had on the formation and evolution of the early Universe.

Key questions: How did the first galaxies evolve over time? What can we learn about dark matter and dark energy?

This illustration summarises the almost 14-billion-year long history of our Universe. It shows the main events that occurred between the initial phase of the cosmos, where its properties were almost uniform and punctuated only by tiny fluctuations, to the rich variety of cosmic structures that we observe today: stars and galaxies. The series of panels on the right side of the illustration zooms into the cosmic large-scale structure to reveal first a cluster of galaxies, then a spiral galaxy similar to our own Milky Way Galaxy, and finally, the Solar System. Credit: ESA – C. Carreau

Today’s Universe is populated by galaxies – cosmic islands made of hundreds of billions of stars. Their sizes and shapes are vastly different, holding clues to how they formed and evolved. In the first few billion years, the Universe was very dynamic, with galaxies undergoing merging events or being ripped apart, and were peppered by supernova explosions from short-lived, massive stars. Operating at infrared wavelengths, Webb can observe the bulk of the light from these primordial galaxies and reveal their dust-shrouded star birth and matter-absorbing black holes.

Webb will also shed light on dark matter, the material that fills the cosmos but is not directly visible. In this way, Webb will complement ESA’s Euclid mission that will map the geometry of the Universe and is specifically designed to study dark energy, the force behind the Universe’s accelerating expansion, and dark matter.