What is the main difference Intrusive and Extrusive Rocks ? Why do we have it ?
The main difference is in Grain size of these rocks. Intrusive rocks have a slow rate of cooling. so, they get more time to grow their grain. In Extrusive rocks, the rate of cooling is very fast such that grain size can not grow much. We get this difference due to difference in rate of cooling.
What is the difference between Remote Sensing and GIS(Geographic Information System) ?
Remote Sensing: It is the process of observing some object or Activity from a distance with coming into direct contact with the System. GIS : It is a System of Organized, Processed data, which will provide information on-demand. This data can also be remote sensing data. Remote sensing is the process which we use to collect data. To use that data and process it, we use GIS.
Why Don't we have any typical stars with the mass lower than 0.08 Solar mass ?
Let's Start with the basics. We know that at the core of stars, Fusion reaction is going on and due to that only stars emit light/energy. This fusion reaction requires very high temperature and Pressure. Now, when the star is forming with the accretion of material around it, at the core temperature and pressure increases as more and more matter accretes. After some point, only fusion reaction will start. That point is related to mass 0.08 solar mass. That is why do observe stars with mass less than 0.08 solar mass.