K2-18b, an exoplanet with water and in the habitable zone has been discovered by scientists.
- Of all the 4000 exoplanets discovered so far, this is the first exoplanet with water has been discovered.
- The water is found in the planet’s atmosphere as water vapour.
- The discovery is Mae by a team of scientists from the University College London (UCL).
- They observed the planet using Hubble Space Telescope which analysed the starlight filtered through the atmosphere of K2-18b between 2016 and 2017.
- It has earth-like temperatures and could possibly support life.
- The planet’s orbit is in the Goldilocks zone of its star. That is it is neither too close to the start nor too far away but in the right place where water can exist in its liquid form.
- As per computer modelling, scientists suggested that water vapour concentrations in the planet’s atmosphere to be between 0.1% and 50%.
- When compared, Earth has a water vapour concentration of 0.2% above the poles an 4% above the tropics.
- K2-18b orbits a red dwarf and is 110 light years away from earth.
- It will take 1,70,000 years to reach the planet with the fastest man-made flying object the Parker Solar Probe.
- These are planets outside the solar system and are super earths – sizes ranging between Earth and Neptune.
- They may be gas giants or planets with solid landmass.
- Exoplanets are identified using four methods – the transit method, wobble method, microlensing and direct imaging.
- Transit method – Kepler Mission, Spitzer Space Telescope and TRAnsiting Planets and Planetesimals Small Telescope uses this method. When an exoplanet passes in front of its star, the light of the start dims for a fraction of a second. This dip in starlight reveals the presence and movement of an exoplanet.
- Wobble Method – in this method Doppler Spectroscopy is used. A common centre of mass is formed when a star and an exoplanet moves around. If the mass of the exoplanet is greater than its star there occurs a wobble in the centre of mass which is detected as a shift in stat light frequency.
- Direct Imaging – This method is used on star systems that are close to the earth. It is a limited method. Using an instrument called Coronagraph, scientists take the image of the star system. It will block the light of the star and will reveal the dim light on the planets.
- Microlensing – This method will reveal exoplanets that absorbs all of its starlight and appears dark. Objects in space curve the space-time and bend the light traveling near it. This is known as microlensing.