Our knowledge of exoplanets is growing rapidly.
In recent years astronomers have discovered myriad worlds beyond our solar system
even deducing information about their sizes, temperatures and atmospheres
But how can scientists know these details about planets that exist at such a vast distances from us?
Discovering Exoplanets from Transits.
Exoplanets raise some tantalizing questions
from the possibility of other Earth-like worlds to alien life.
But pursuing answers to these questions is not an easy task
Exoplanets emit almost no visible light of their own
and orbit stars at great distances from Earth, making them very difficult to observe.
Transits offer one of the best chances to study exoplanets.
This is when a planet crosses between its host star and Earth,
temporarily reducing the star's apparent brightness.
The duration and change in intensity of the light curve
give astronomers clues about the planet's size and orbit.
Additional smaller dips in light levels just before or after the transit
can indicate a satellite; an exomoon.
Transits can even tell us what a planet is made of.
The tiny fraction of light that passes through its atmosphere
interacts with atoms and molecules there.
The light then carries information about them,
which scientists use to infer conditions
like temperature, chemical composition and formation history.
However, this method has limits.
Transits only happen if a planet's orbit actually crosses between its host star and Earth
so its orbit must be edge-on towards us.
This is the case for just a small fraction of planetary systems
Where they do occur, transits happen infrequently and last for a relatively short time
so chance observations are unlikely.
Transits are also bias towards finding larger exoplanets that are closer to their host star.
These planets block out more light, producing a larger dip in brightness that is easier to detect.
So transits don't represents the full diversity of worlds out there.
There can even be false positives.
Sometimes a dip in brightness is caused by something else such as one star passing in front of another
in a binary system.
Despite these limitations, transits have revealed scores of other worlds
thanks to the sheer number of stars and planets in the universe
and the sophisticated technology that looks for them.
The Hubble Space Telescope is a major milestone in this field.
Hubble has made the first atmospheric study of Earth-sized exoplanets,
captured the first image of an exoplanet in visible light,
and discovered the first organic molecule in the atmosphere of an exoplanet.
However, these remarkable discoveries push Hubble to its very limits.
To delve even deeper into these distant worlds,
we need even more powerful telescopes.
The upcoming James Webb Space Telescope will take this technology to the next level.
James Webb will observe the universe at infrared wavelengths with unprecedented sensitivity.
This is especially advantageous for studying exoplanets
because molecules in exoplanet atmospheres leave most clues in the infrared range.
Specifically, these wavelengths could help us find habitable planets.
Planets with the right conditions to sustain liquid water emit heat radiation that peaks in the infrared.
James Webb's sensitivity to these crucial wavelengths is bound to uncover more secrets of exoplanets
and might even find life elsewhere in the Universe.
This Hubblecast script was translated by Bethany Downer.