Purpose
Currently, the direct detection of extrasolar planets (or exoplanets) is extremely difficult. This is primarily due to:
- Exoplanets appear extremely close to their host stars when observed at astronomical distances. Even the closest of stars are several light years away. This means that while looking for exoplanets, one would typically be observing very small angles from the star, on the order of several tens of milli-arcseconds. Angles this small are impossible to resolve from the ground due to astronomical seeing.
- Exoplanets are extremely dim compared to their host stars. Typically, the star will be approximately a billion times brighter than the orbiting planet. This makes it near-impossible to see planets against the star's glare.
The difficulty of observing such a dim planet so close to a bright star is the obstacle that has prevented astronomers from directly photographing exoplanets. To date, only a handful of exoplanets have been photographed . The first exoplanet to be photographed, 2M1207b, is in orbit around a star called 2M1207. Astronomers were able to photograph this planet because it is a very unusual planet. Specifically it does not suffer from the two difficulties mentioned above. It is very far from the host star, approximately 55 astronomical units (about twice the distance of Neptune). Furthermore, the planet is orbiting a very dim star, known as a brown dwarf. Because the planet is so far from its dim host star, it is not lost in the glare. However, this is a very specific scenario, and would be unlikely to be useful in finding Earth-like planets capable of supporting life.
To overcome the difficulty of distinguishing a planet in the glare of a bright star, the New Worlds Mission would block the star's light with an occulter. The occulter would block all of the starlight from reaching the observer, while allowing the planet's light to pass undisturbed.
Read more about this topic: New Worlds Mission
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