Question: An astrophysicist studies 7 exoplanets, 4 of which have detectable biosignatures. If 4 planets are randomly selected, what is the probability that exactly 2 have biosignatures?

Mon, 04 May 2026 18:00:52 +0000

**What’s the Most Fascinating Glimpse We Have of Life Beyond Earth?**
An astrophysicist studies 7 exoplanets, 4 of which show detectable biosignatures. If 4 planets are randomly selected, what’s the chance exactly 2 reveal signs of life? This question underscores growing public and scientific interest in finding habitable worlds—and understanding the statistical foundations behind such discovery probabilities. It reflects a broader curiosity about cosmic habitability and the search for biosignatures, driven by advances in space observation and data modeling. ### Why This Question Is Resonating Right Now
Trends in astrophysics and space exploration are fueling public fascination. With major missions like JWST refining our ability to analyze distant worlds, each new planet discovery carries implications for life’s universal potential. The specific setup of “4 biosignature-bearing planets out of 7, selecting 4” mirrors real data selection in astrobiology research. This realistic scenario appeals to users curious about how scientists assess planetary systems with precision—turning complex probability into a tangible, relatable puzzle. ### How to Understand This Statistical Question
The core problem involves hypergeometric probability — the chance of drawing exactly 2 biosignature planets when selecting 4 from a group with 4 “successes” among 7. Step-by-step, this means:
- Total planets: 7
- With biosignatures: 4
- Without: 3
- Select 4 planets at random
- What’s the chance exactly 2 are biosignature planets? Using combinatorics, the number of ways to choose 2 biosignature planets from 4 is C(4,2). The remaining 2 must come from the 3 without biosignatures, calculated as C(3,2). Dividing favorable outcomes by total combinations reveals the probability—and demonstrates how math quantifies uncertainty in scientific discovery.