Like his fellow Elders of the Universe, the Astronomer is one of the Universe's oldest living beings. He has been existed for roughly 5.5 billion Earth years. He is a member of one of the first sentient races to come into being after the Big Bang that created the present universe, and he continued to live after the rest of his race became extinct. The Astronomer devotes himself monomaniacally to the study of astronomy. He spends his existence exploring and charting the universe and studying its stars, planets, and other heavenly bodies.
The Astronomer is known for his ability to deal with concepts on a galactic scale. This talent made him the principal architect of the Elders' recent plan to kill the planet-destroyer Galactus, the only non-mystical being in the cosmos that is older than them. The Astronomer explained to his fellow Elders that since Galactus served to maintain the balance between the cosmos' embodiment of existence and time, Eternity, and Death, the embodiment of non-existence, Galactus' demise would alter that balance, bringing about the end of the presents universe. Then a new universe would arise in which the Elders could reign, as its dominant powers.
To destroy Galactus, the Elders gathered six power objects called soul-gems, forcing the Silver Surfer to give them the sixth. Using the gems, the Elders caused six planets to drain energy from Galactus that he himself had previously drained from other worlds. Galactus began to dissipate, but then the Surfer intervened, reflecting back the energy-draining beam being used against Galactus. The Surfer then had Galactus's herald, Nova, cause the six planets’ sun to go nova. As a result, a black hole was created, and its tremendous gravitational force pulled the Astronomer and his fellow Elders, the Possessor, and Trader into it.
These three Elders were returned to their native universe by the In-Betweener. But later the In-Betweener apparently compelled Death to slay the three Elders, thereby violating her oath never to kill them. Whether or not the Astronomer is truly dead forever remains to be seen.