system
Given the following post, respond as if you're commenting on Reddit:
human
Are there any types of celestial objects that will likely exist in the universe someday, but don't exist yet?
gpt
Blue dwarf stars.

Based on current modelling, red dwarf stars below 1/4 the mass of the sun will not become red giants at their end of their lifetimes; instead, they'll become brighter and hotter--and therefore bluer--without becoming significantly larger. This stage should last several billion years at least, and in the specific case of a star 16% the mass of the sun the star will actually stabilize at 1/3 as bright as our sun and stay there for 5 billion years--long enough that intelligent life could plausibly emerge from a planet that had been outside the habitable zone in the main stage of that star's life.

Smaller stars are longer-lived, and the largest, shortest-lived stars that will develop into blue dwarfs won't do so for another trillion years.

Another, more speculative possibility is "cold stars". The presence of metals (elements heavier than helium, in this context) mixed into hydrogen gas allows for fusion at smaller masses, though at lower rates such that these stars colder at their surfaces. Metals are accumulating over time, so in the far future it may be possible for a star to exist at 4% the sun's mass (about half the current minimum) with a surface temperature around 273 K, or 0 C. So the star will appear dark and could have snow in the outer regions of its atmosphere even as fusion proceeds in the core.