<s>[INST] The Hourglass Nebula (MyCn18) is taken in infrared light using cameras on board the Hubble Space Telescope, and shows the formation of new protostars within the molecular cloud in this 21st century discovery.  Don't you think a telescope back in the 18th century would have been unable to detect this as it does not emit visible light but does emit some infrared, X-ray, and low-energy gamma rays.
That is a very good guess and is consistent with the fact that the Hourglass Nebula wasn't discovered until modern times.  Your logic is sound, but also consider that detection of such objects even today may depend on very specific conditions.  Namely,optical observations require clear line of sight so that the light can travel from the object and reach the detector, unobstructed. Is there something in our own solar system which could block optical light from reaching an observer on Earth?[/INST]