Dark matter and dark energy, comprising 95% of the universe, remain undetectable and their composition is unknown.
In 2006, Pluto became a non-planet, reducing the solar system to eight planets, while a possible Ninth Planet beyond Neptune is still elusive.
A vast cosmic void, 330 million light-years wide, has extremely few galaxies, raising questions about the universe's formation and structure.
Saturn's mysterious moon Peggy, observed by Cassini in 2013, is likely deteriorating and unlikely to grow.
KELT-9b survives extreme temperatures of 4,300°C, revealing insights into exoplanetary evolution and extreme environments.
KIC 8462852, or Tabby's Star, is an anomaly blocking 20% of light, investigated by NASA's James Webb Telescope.
Gavin Schmidt and Adam Frank investigate ancient non-human civilizations and future discovery implications.