ALL ANSWERS · SPACE · DAILY No. 20 · SEPTEMBER 23, 2026
Size It Up Space answer: September 23
The five Space silhouettes for September 23, with the true sizes. If you have not played yet, this page is a spoiler — play these five first, then come back to argue with the numbers.
Day 20 ran from Phobos (22.16 km) to Charon (1,212 km). The widest gap was round 3, Helene against Janus, at 5.0×; the closest call was round 2, Charon against Umbriel, only 1.0× apart — the kind of round that separates a 90 from a 60.
SPOILER · TODAY’S FIVE
You have not finished today’s puzzle on this device. The answers below are blurred so you can still play first.
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ROUND 1
Phobos (Mars’s moon · mean diameter) vs Prometheus (Saturn’s moon · mean diameter)
Prometheus · reference · 86.2 km Phobos · true diameter · 22.16 km 3.9× shorter than Prometheus
Phobos, a moon of Mars, has a mean diameter of about 22.2 km. This is the body’s size, not an orbital distance.
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ROUND 2
Charon (Pluto’s moon · mean diameter) vs Umbriel (Uranus’s moon · mean diameter)
Umbriel · reference · 1,169 km Charon · true diameter · 1,212 km 1.0× wider than Umbriel
Charon, a moon of Pluto, has a mean diameter of about 1,212 km. This is the body’s size, not an orbital distance.
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ROUND 3
Helene (Saturn’s moon · mean diameter) vs Janus (Saturn’s moon · mean diameter)
Janus · reference · 178.4 km Helene · true diameter · 36 km 5.0× shorter than Janus
Helene, a moon of Saturn, has a mean diameter of about 36 km. This is the body’s size, not an orbital distance.
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ROUND 4
Metis (Jupiter’s moon · mean diameter) vs Pandora (Saturn’s moon · mean diameter)
Pandora · reference · 81.2 km Metis · true diameter · 43 km 1.9× shorter than Pandora
Metis, a moon of Jupiter, has a mean diameter of about 43 km. This is the body’s size, not an orbital distance.
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ROUND 5
Hyperion (Saturn’s moon · mean diameter) vs Proteus (Neptune’s moon · mean diameter)
Proteus · reference · 416 km Hyperion · true diameter · 270 km 1.5× shorter than Proteus
Hyperion, a moon of Saturn, has a mean diameter of about 270 km. This is the body’s size, not an orbital distance.
Beat these tomorrow
Every round is worth up to 100 points: within 6% of the true size scores 100, half or double scores 45, five times off scores zero. The daily puzzle is the same five for everyone and refreshes at midnight in your time zone; if you want more than five, Size It Up Unlimited draws fresh pairs from the whole library for as long as you like.