excerpt adapted from Exoplanet in the Corner Pocket by Pat Brennan First, they rolled in one by one, those newly discovered planets, like billiard balls pushed across a table. Counting them was easy. Then, they came in handfuls, still quite manageable, as ground-based observatories began to pile up their discoveries of exoplanets (planets outside our solar system). In the 1990s and early 2000s, astronomers had no trouble keeping a running tally. But when discoveries of exoplanets began to flow from space-based telescopes, it was like a pool player making a big, smashing break. The billiard balls raced across the table in bunches. In just a few years, scientists were racking up an inordinate number of new planets, accumulating them by the thousands. And it wasn't just the number, but the types of planets that had to be accounted for—"hot Jupiters"; gas giants; rocky, Earth-sized worlds; and "super Earths." There were also hints of potentially frozen, scalding, lava-choked, icy, steamy, or watery planets. NASA's Exoplanet Science Institute, keepers of the NASA Exoplanet Archive, set up automated counters of exoplanet discoveries, which were always-running, online dashboards that tracked the number and variety of them. The latest totals: some 3,700 confirmed exoplanets in our galaxy, with thousands more candidate planets that remain unconfirmed. But now, after piling up two decades worth of exoplanet discoveries, NASA scientists have begun a wholesale reshuffling of their counting methods. At first, this means a drop in the number of "candidate" planets, with roughly half moving to the "confirmed" category. These planets were already confirmed but were being double counted: The previous number on the counter, 4,496, was labeled "candidates," but critically, it included the combined total of confirmed and unconfirmed exoplanets, and only from NASA's Kepler space telescope observations from 2009 to 2013. In the new counter, only "unconfirmed" planets are labeled as "candid