A rich starry sky fills the view from an ancient gas-giant planet in the core of the globular star cluster M4, as imagined in this artist's concept. The 13-billion-year-old planet orbits a helium white-dwarf star and the millisecond pulsar B1620-26, seen at lower left.

While the final report is still more than five years away, NASA has effectively kicked off the next astrophysics decadal survey by asking the scientific community to evaluate ideas for the next large mission that the report may recommend NASA pursue in the 2020s.

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Jeff Foust has more than a decade of experience writing about space policy, entrepreneurial ventures and regulatory affairs. In 2001, he established spacetoday.net to aggregate and summarize the day's space-related news stories. In 2003, he started The...