What are different ways astromers search for habital planets and life outside of earth?

Answer 1

First order of business is to find stars with captive planets. This is done by finding a star and looking for a "wobble" caused by something orbiting it. If something we can't see is orbiting a star we can see, the orbiting body pulls the star around slightly as it orbits. That "pulling around" is what causes the "wobble."

Second order of business is to determine the size of the orbiting body. This is done by calculating the mass of the star and how much that mass is "pulled around."

In our experience (albeit limited), a very large planet (like Jupiter) probably is incapable of supporting life. The tremendous gravity makes a solid surface unlikely. Besides, that much gravity would crush any critter on the planet's surface.

If the planet is too small it is unlikely to possess the necessary requirements for life (as we know it) such as air and water.

Ok, if science finds an orbiting body "about the right size," they then try to determine its composition. Honestly how they do that is conjecture on my part, but if they can get the light from the star to shine past the object on its way to Earth (for example, when the object is between the star and Earth) they could do a spectrographic analysis of the composition of the atmosphere.

But, as has been stated, our experience with life is pretty limited. We're familiar only with carbon-based, oxygen-breathing critters that live within a very limited range of conditions... except for trees (which breathe carbon dioxide) and a few critters deep in the ocean (that live in extremely hot and totally dark environments and which are surrounded by sulfur gas). There could be critters living on planets with environments totally hostile to human life. So it's conceivable that "habitable" may not be limited to human criteria.

Answer 2

Using light gathering telescopes.
Using radio signal gathering dishes.

Then analyzing all the gathered information with powerful computers.

Answer 3

believe me they just guess and bluff. not only this there many such statements which can not be prove by other scientists are just bluffs.