Question

For some given Data, Z=20 M=30 then find mean

Answer 1

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Sadly, no, Or I suppose thankfully no from the point of view of the general public :P However, I should amend that statement to say no - although I suppose there may technically be a minuscule chance of a low-mass hole located many thousands of astronomical units away, more like within interstellar space than our solar system though. Realistically however, even this is essentially impossible. The only reason I say that is because I never like to give absolute statements in science; it's extremely unlikely to be true, but "extremely unlikely" and "impossible" are two very different concepts.

So how can we know this when black holes can't even be seen?? Gravity. The great William Herschel spotted a new planet for the first time back in the mid 1800's. It was the first time in history that anyone has seen Uranus! (Snicker). This find of course triggered a massive hunt for outer solar-system objects. When data on Uranus was being collected and examined, it was eventually noticed that there were extremely subtle, tiny anomalies in its expected orbital path; somehow, it was deviating ever-so-slightly from the orbit that was expected based on the known masses and positions of other objects in our solar system. It appeared that something was tugging it away!

In a flurry of mathematical skill, tables and values were immediately produced which predicted the location another unknown planet must be, as well as it's mass - IF that object was indeed responsible for the anomaly. Mere days later, Neptune was found - almost exactly within it's expected co-ordinates.

I told this story for a reason. If a tiny, tiny, tiny speck of a planet (compared to the sheer size of the solar system) was gravitationally influencing the movement of planets dozens of astronomical units (billions of miles) away, just imagine what we might see if there were a great, big old black hole lurking around somewhere in the void. At the very least, we would have some very powerful evidence of a massive gravitational body affecting everything else around it to a great distance. Note that this refers to a mathematically predictable influence on the orbit of the other solar system bodies - black holes are NOT the "cosmic vacuum cleaners" you sometimes see on TV or in movies. Bodies can orbit them just like anything else.

So it's safe to say that we luckily have no black holes anywhere near our neighborhood - the nearest one is expected to be at least one or two dozen light-years away. Still, the sheer vastness of space means there are millions or billions of them wandering through our galaxy alone