What are Habitable Zone planets

The region surrounding a star that is neither too hot nor too cold is known as the habitable zone, where liquid water can exist on a planet's surface. 

Exoplanets in the habitable zones of their stars are appealing sites to look for life because liquid water is a necessary component for life as we know it. 

In some circumstances, like as the subterranean ocean of Europa, liquid water can exist at a star's habitable zone. 

As far as we are aware, only Earth contains liquid water on its surface and can sustain life among all the planets, moons, asteroids, and comets in our solar system. Because our planet is located in the "habitable zone" of our solar system, this is the case. Because of the distance from the Sun, none of our water boils, although

About 40 planets, including the nearest extrasolar planet, Proxima Centauri b, and three planets in the TRAPPIST-1 system, have been found that are both roughly Earth-sized and orbiting within the habitable zones of their stars. Astronomers have also used simulations of the climates of other extrasolar planets such as Kepler-452bto determine that they could have surface water under the right climatic conditions.

The size of the habitable zone clearly depends on the luminosity of the star, which determines the equilibrium temperature of the planet. However, modern models for the range of the habitable zone take into account more subtle effects, such as the effect of the carbonate-silicate cycle in regulating carbon dioxide in a planet's atmosphere. Work on this particular process by Penn State scientists, including Professor James Kasting, has shown that the habitable zone extends farther from a star than originally assumed.

1. Optimistic habitable zone:Regions that receive an amount of radiation from their star less than Venus did 1 billion years ago and more than Mars did 3.8 billion years ago ago. These “recent Venus” (RV) and “early Mars” (EM) limits are chosen because observations suggest liquid water existed on those planets until 1 or 3.8 billion years ago, respectively.
2. Conservative habitable zone:A greenhouse effect model. The inner edge is defined by the “runaway greenhouse,” where stellar flux will vaporize an ocean. The outer edge is defined as the “maximum greenhouse,” where Rayleigh scattering dominates over the greenhouse effect.
3. Astronomers are always on the lookout for Earth-like planets in our cosmic backyard — either to detect signs of life on them, predict what sort of fate our home planet would meet, or find humans an alternative home. And while the Earth is one of a kind and the only known world to support life, scientists have managed to build quite a list of Earth-like exoplanets in our galactic neighbourhood.
   The most recent additions to this list are GJ 1002b and GJ 1002c. Dubbed 'potentially habitable', these babies can be seen orbiting a red dwarf star. The best part? They're only 16 lightyears away from us!
   Humans might not be popping off to and fro these newly discovered worlds anytime soon, but space-distance-wise, 16 lightyears is very much on the lower end.
   Further, the exoplanets lie in their star GJ 1002's 'habitable zone', which is essentially the area around a star that is neither too hot nor too cold to support liquid water — a vital ingredient for life.

   GJ 1002 is a cool, faint red dwarf star with one-eight the mass of our Sun. Consequently, the star’s habitability zone is very close to it — even closer than the Earth is to the Sun. In fact, the inner planet GJ 1002b takes just ten days to orbit the star, while GJ1002 requires just over 21 days to do so.

   These exoplanets were found owing to a collaboration between the European Southern Observatory's (ESO) instrument ESPRESSO (Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations) and CARMENES (Calar Alto high-Resolution search for M dwarfs with Exoearths with Near-infrared and optical Échelle Spectrographs).

   ESPRESSO and CARMENES observed the exoplanets' parent star during two separate periods, with CARMENES studying GJ 1002 between 2017 and 2019 and ESPRESSO collecting data from the red dwarf between 2019 and 2021.

   Just being in a habitable zone does not mean that GJ 1002b and GJ 1002c can support life. For example, in our solar system, both Venus and Mars fall in the Sun's habitable zone as well, but are incapable of hosting life.

   However, the proximity of the exoplanets to Earth means that they make excellent targets for astronomers aiming to study the atmospheres of Earth-like worlds outside the solar system.