Combust Planets - Now this will be some fun to explain and to understand as well.
Basic ancient definition of a "Combust Planet" is when a planet comes too near to Sun (degree wise), it starts feeling heat out of the fire of Sun. When it comes even closer then it starts burning and this burning of a planet is referred as Combustion of Planets. In Hindi, it is called as "Ast Gruha". About effects it is said that Planet thus combusted is unable to give any positive result for the simple reason that it is burnt.
Now, some recent researches have come up in which it is said that a planet is never fully combusted or burnt, as such in any situation, every planet will provide some of its impact. Best way to understand it, is to look at the chart here. In 10th house and in sign of Leo, Sun is at 9.06* , Mercury is at 27.20*, Mars is at 6.05* and Venus is at 7.28*. So, Lets see some rules regarding combustion of planets and then see which planet is combust here and which is not.
1. First of all, Mercury is only combust when it is within 1 degree distance from Sun. Like, if Sun is at 9.06* here then Mercury will only be called combust when it is between 8.06* to 10.06*, so at one degree distance from Sun. Reason? Because Mercury is always the closest planet to Sun. It is used to the heat of Sun, it is always burning. So, like in this horoscope, Sun is at 9.06* and Mercury is at 27.20*. No combustion at all. Mercury is safe and sound.
2. Then Mars is at 6.05* and Sun is at 9.06*. Now, remember the speed at which planets travel. Sun completes 1 degree per day (30 degrees in a month) and Mars completes 1.5 degrees per day (30 degrees in 45 days). So, Sun is actually moving away from Mars at a faster speed. That means, Mars is actually coming out of combustion as Sun is running away from it. Mars is getting cooled off. Hence, no combustion. Again, Mars is also one red, fiery and hot planet, just like Mercury it is used to the heat. It is more a reason for Mars not to be combusted.
3. Then Venus is at 7.28* and Sun is at 9.06*. Now, here Venus travels at faster pace (30 degrees in about 27 days), as such this Venus is marching towards Sun, feeling heated and feeling burns. So, in this horoscope, we can say that only Venus is getting combust to a very little extent.
Now the effect. Can we say that as Venus is getting combusted in this horoscope and as Venus represents convenience, wealth and relation, this person will be deprived of all these things for whole of life?? Well, not really. As I said that recent researches have shown that no planet is completely burnt away. Some good qualities will always remain. So, this person may have to work little more hard on gaining wealth and stabilising relations but through perseverance, he will get it.
Again, one more important thing is the zodiac sign and house in which combustion is taking place. Suppose, same Sun and Venus is in Pisces, where Venus becomes exalted, then Venus is more powerful than Sun. Now, no matter how close is Venus to Sun, exalted Venus will always give its impact.
As my Guru once said in one of his videos, "in astrology, nothing cancels anything. everything is in addition". So, any planet coming closer to Sun (howsoever) will somehow manage to give some good results from its position despite the combustion.
Actually, my own horoscope is best example. I am born with Mercury very close (degree wise) to Sun in 3rd house. Mercury is communication, collecting information and above all it is significator (Karaka) of Astrology, 3rd house is communication and announcements. If it is really combust or burnt off, I won't have been communicating with my audience on daily basis on the information related to Astrology.
Hope this helps. Thanks,