Yes, we can directly observe stars beyond about twenty light years in distance. In fact, astronomers have been observing and studying stars that are much farther away than that for many decades. By using telescopes, both on the ground and in space, we are able to capture and study light emitted by stars located at vast distances from us.
When we observe a star, we are essentially detecting the light that has traveled from that star to our telescopes. Light travels at a finite speed, so the light we receive from distant stars has taken a certain amount of time to reach us. For example, if a star is located 100 light years away, the light we observe today was emitted from that star 100 years ago.
Therefore, when we observe stars beyond about twenty light years in distance, we are effectively looking into the past. The light we receive from these stars has traveled for many years before reaching us, allowing us to study the properties, composition, and behavior of those stars.
It's worth noting that dark matter does not directly affect our ability to observe stars. Dark matter primarily interacts gravitationally and has little impact on the emission, transmission, or detection of light. It primarily affects the motion of galaxies and galaxy clusters on a large scale.