Dark or black stars may have been the most influential celestial bodies in the universe, although no one knows for sure if they existed. They may have existed before conventional stars were able to form.
So why is there no evidence of their existence ?
Dark stars could have literally vanished into a black hole. At least that's the theory put forward by University of Michigan (USA) physicist Katherine Freese.
Freese suggests that dark stars are actually the seeds of supermassive black holes lurking at the heart of every galaxy. After all, even regions of space that bend time and absorb light have to be born of something. And that something could be a dark star.
But how does a bright, bright celestial body take such an extreme dark twist? If a dark star indeed does exist it would already have darkness literally running through its veins.
What's the difference between dark stars?
The stars we see today comply with the same general rule of nuclear fusion. The large mass of a star means that it is always in a state of collapse on itself. But that kind of constant pressure on its core also produces energy that is radiated out. The result is a perfect balance of inward attraction and outward radiation.
Our sun, for example, has reached that perfect balance, building up gravitational pressure in the giant battery that essentially powers the solar system.
Dark stars, on the other hand, make things a little different. They have hydrogen and helium but also a touch of dark matter. It's that other material that no one has seen or detected, which makes the dark star theory even more diffuse.
About 13 billion years ago, when dark stars formed, the universe was a very different and much denser place. They probably incorporated dark matter into their DNA, in the form of weakly interacting massive particles or WIMPs (hypothetical particles that could explain the dark matter problem, as we see).
Even as a microscopic ingredient in a star, dark matter could hold a celestial body for a billion years thanks to a unique process called annihilation of dark matter.
Essentially, dark matter gives a dark star its "superpowers": it could expand and radiate energy without having to rely on that delicate process known as nuclear fusion. That would also discharge the dark star from its core, allowing it to extend outward and, despite its name, shine even brighter. They could continue to grow as long as there was dark matter fuel.
There would be no limit, in principle. Later, at some point, a star with so much mass would have to collapse into a black hole.
How do we test this hypothesis?
The James Webb Space Telescope could give us the answer. Scheduled for launch in March 2021, the space eye will be "the largest and most powerful telescope ever placed in space. While astronomers are excited about the possibility of countless discoveries of new planets, Webb will also be able to glimpse the oldest and most elusive celestial body known as the dark star.