Is it possible for a star to be invisible?

One of the things I’ve always been most curious about on the topic of space is: is it possible for something that emits light (like a star) to emit light such as radio or gamma waves but not visible light? If such an object existed, it would be invisible to us, although it could still be detected. But it such an object existed and happened to be traveling on a course dangerously close to our solar system, we might not know to look for it with special instruments because we can’t see it.

Stars are primarily powered by fusion – fusing hydrogen atoms into helium (sometimes other elements are involved, but these are most common). This produces a wide range of light waves, from gamma to radio. Visible light is in between those extremes, so it’s expected to be emitted as well.

Source: Brian Koberlein

The closest thing to a star that doesn’t emit visible light is a black dwarf (pictured above), which has yet to be discovered. Once a white dwarf star runs out of fuel, it theoretically will turn into a black dwarf, emitting no heat and no light. The only way to observe it would be if another object’s emitted light bounced off of it. There are no known black dwarfs; the universe (we believe) has not been around long enough for any white dwarfs to burn through all of their fuel. So, the chances of a massive, invisible object speeding through space towards us (or a similarly invisible approaching alien fleet) are essentially zero.

The Limitations of Space Travel

Let’s just imagine for a moment that humanity eventually advances in technology such that light-speed travel is attainable. The speed of light, roughly 3×10^8 m/s, is the upper limit on travel speed- If light could go any faster, it would.

With light-speed travel, humanity will likely attempt to colonize other planets, for a variety of reasons- curiosity, resource depletion, or even a sense of manifest destiny. Imagine, for a moment, that you are hoping to travel to a habitable planet in the Andromeda galaxy. Andromeda is 2 million light years away. This means that, even if a method of light-speed travel is devised, it would take 2 million years to reach a planet in one of the galaxies nearest to us. For reference, humans have been around for about two hundred thousand years.

Even with an endlessly vast universe, the chances of humans leaving the Milky Way seem to be essentially zero.

Medical News Today

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