Complex sentence: WISE 1049-5319 appears in the sky close to the galactic plane which is densely populated by stars making it difficult to spot faint objects which explains why an object so near to the Sun was not discovered in earlier searches.
Split into simpler sentences: WISE 1049-5319 appears in the sky close to the galactic plane which is densely populated by stars making it difficult to spot faint objects. This explains why an object so near to the Sun was not discovered in earlier searches.