Direct imaging is a challenging technique for detecting exoplanets, as they are typically very faint and close to their host stars. The other methods listed are more commonly used and have been successful in detecting a large number of exoplanets.

Transit is the term used to describe the periodic dimming of a star's light caused by an exoplanet passing in front of it. This dimming occurs because the exoplanet blocks some of the star's light from reaching the observer.

Gas giants are large, low-density exoplanets that are primarily composed of gases like hydrogen and helium. They are similar to the gas giants in our own solar system, such as Jupiter and Saturn.

Exoplanet is the term used to describe an exoplanet that orbits a star other than the Sun. The term 'extraterrestrial planet' is also sometimes used, but 'exoplanet' is the more common and widely accepted term.

The discovery of exoplanets has provided strong evidence for the nebular hypothesis, which is the leading theory for the formation of our solar system. However, it has not confirmed the nebular hypothesis, as there are still some aspects of the theory that are not fully understood.

Habitable planet is the term used to describe a planet that is located within the habitable zone of its host star, where liquid water could potentially exist on its surface. The term 'Goldilocks planet' is sometimes used to refer to a habitable planet that has conditions that are just right for life to thrive.

Hot Jupiters are typically not large in size, despite their high temperatures. They are often comparable in size to Jupiter or Saturn.

Terrestrial planet is the term used to describe a planet that is composed primarily of rock and metal, similar to the terrestrial planets in our solar system. These planets are typically smaller and denser than gas giants.

Direct imaging is not a potential method for detecting biosignatures on exoplanets, as it is extremely challenging to directly image exoplanets, let alone detect biosignatures on their surfaces.

Non-habitable planet is the term used to describe a planet that is located outside of its host star's habitable zone, where liquid water cannot exist on its surface. These planets may be too hot, too cold, or have other conditions that make them unsuitable for life as we know it.

The discovery of exoplanets has challenged the idea that our solar system is unique in the universe. It has shown that planetary systems are common and diverse, and that there may be many other planets out there that could potentially harbor life.

Super-Earth is the term used to describe a planet that is located between the size of a terrestrial planet and a gas giant. These planets are typically larger than Earth but smaller than Neptune.

The lack of telescopes is not a potential challenge in studying exoplanets, as there are many telescopes that are capable of detecting and studying exoplanets. The other challenges listed are real and significant obstacles that astronomers face when studying exoplanets.

Tidally locked planet is the term used to describe a planet that is tidally locked to its host star, meaning that one side of the planet always faces the star and the other side is always dark. This can lead to extreme temperature differences between the two sides of the planet.

Astrometry is not a potential method for searching for exoplanets, as it is not sensitive enough to detect the small wobbles in a star's position caused by an orbiting exoplanet. The other methods listed are more commonly used and have been successful in detecting a large number of exoplanets.