The article was talking about asteroid sized (as in diameter), not mass. https://www.wolframalpha.com/input/?i=black+hole+horizon+radius&assumption=%7B%22F%22%

The article was talking about asteroid sized (as in diameter), not mass. https://www.wolframalpha.com/input/?i=black+hole+horizon+radius&assumption=%7B%22F%22%2C+%22EventHorizonRadius%22%2C+%22M%22%7D+-%3E%221%C3%9710%5E29+kg%22 https://www.wolframalpha.com/input/?i=black+hole+horizon+rad... shows a black hole of mass 1×10^29 kg (which is about 1/20 of one solar mass) has a radius of 148.5 meters which is asteroid size. https://www.wolframalpha.com/input/?i=gravity+of+1%C3%9710%5E29+kg https://www.wolframalpha.com/input/?i=gravity+of+1%C3%9710%5... says at one earth's radius away that it has an escape velocity of 1447.5 km/s (kilometers per second), so yeah I think that will either destroy part of Earth or completely consume it, depending on how fast it's passing though. For OP's question, whether it's detectable or not, it possibly is if it warps the light from background stars (same effect as https://en.wikipedia.org/wiki/Eddington_experiment https://en.wikipedia.org/wiki/Eddington_experiment).