According to our current understanding of physics based on Einstein's theory of relativity, an object with mass cannot reach or exceed the speed of light in a vacuum. As an object with mass accelerates towards the speed of light, its relativistic mass increases, making it harder and harder to accelerate further. The energy required to accelerate an object with mass to the speed of light would be infinite.
However, even if we were to consider a hypothetical scenario where an object somehow reached the speed of light, it would not become invisible. The concept of visibility is not directly related to an object's speed. Visibility is determined by how an object interacts with and emits or reflects light, which is governed by the object's properties and the properties of light itself.
In fact, the theory of relativity predicts that as an object with mass approaches the speed of light, its length in the direction of motion contracts, and its time dilation increases. These relativistic effects mean that an observer would perceive the object as shorter and time passing more slowly for it. However, this does not make the object invisible, but rather introduces changes in its observed properties.
It's also worth noting that the speed of light is constant for all observers, and light itself always travels at that speed. So, even if an object could somehow reach the speed of light, it would not be able to emit or reflect light, which would further affect its visibility.