{"uid":"cap_qqghAnjuCnuAqDRbTJfuq","slug":"space-objects-asteroid-diameter-from-absolute-magnitude-324112d3","name":"Space Objects – Asteroid Diameter from Absolute Magnitude","description":"Asteroid diameter from absolute magnitude H and albedo (or a dark-to-bright range), plus optional impact energy in megatons.","url":"https://space-objects.x402tookit.com/asteroid-size?utm_source=zero.xyz","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET"],"type":"string"},"queryParams":{"type":"object","required":["H"],"properties":{"H":{"type":"number","description":"Absolute magnitude H, -5 to 40"},"albedo":{"type":"number","description":"Geometric albedo 0.01 to 1; omit for the 0.05 to 0.25 range"},"densityKgM3":{"type":"number","description":"Bulk density 500 to 8000 kg/m3 (default 2600)"},"velocityKmS":{"type":"number","description":"Impact speed 5 to 72 km/s, to also get impact energy"}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object","properties":{"asOf":{"type":["null","string"]},"albedo":{"type":["null","number"]},"impact":{"type":["null","object"],"properties":{"massKg":{"type":["null","number"]},"speedKmS":{"type":["null","number"]},"densityKgM3":{"type":["null","number"]},"energyJoules":{"type":["null","number"]},"diameterKmUsed":{"type":["null","number"]},"energyMegatonsTnt":{"type":["null","number"]},"energyHiroshimaEquivalents":{"type":["null","number"]}}},"source":{"type":["null","string"]},"formula":{"type":["null","string"]},"reasons":{"type":["array","null"],"items":{"type":"string"}},"summary":{"type":["null","string"]},"verdict":{"type":["null","string"]},"degraded":{"type":["boolean","null"]},"diameterM":{"type":["null","number"]},"diameterKm":{"type":["null","number"]},"disclaimer":{"type":["null","string"]},"notChecked":{"type":["array","null"],"items":{"type":"string"}},"absoluteMagnitudeH":{"type":["null","number"]}}}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.02","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.02/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.02","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_r9jWibzmNpEffPlHAeEHk","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.02","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Calculates asteroid diameter in meters and kilometers from absolute magnitude H and albedo, with optional impact energy in megatons","exampleAgentPrompt":"What's the estimated diameter of an asteroid with absolute magnitude H=22 and albedo 0.14, and how much impact energy would it release hitting Earth at 20 km/s?","exampleUseCases":[{"title":"Planetary defense size estimate","prompt":"I need to know the diameter of the asteroid 2024 YR4 — its H magnitude is 24.9 and albedo is about 0.15. Can you also calculate the impact energy if it hit at 18 km/s?"},{"title":"Classroom asteroid size exercise","prompt":"For a school project I need to convert absolute magnitude H=18 to an asteroid diameter. Can you give me the size range using a typical dark-to-bright albedo spread?"},{"title":"Impact hazard energy comparison","prompt":"If an asteroid has H=20 and hits Earth at 25 km/s with a rocky density of 2600 kg/m3, how many megatons of energy would it release and how does that compare to the Hiroshima bomb?"}],"resultDescription":"Returns asteroid diameter in both meters and kilometers (point estimate or dark-to-bright range if albedo is omitted), along with the formula used, source notes, and optionally: impact mass, speed, density, energy in joules, megatons of TNT, and Hiroshima equivalents — plus a human-readable summary and any relevant caveats or disclaimers.","failureModes":["H magnitude outside -5 to 40 range returns validation error","albedo outside 0.01 to 1 returns validation error","velocity outside 5 to 72 km/s returns validation error","density outside 500 to 8000 kg/m3 returns validation error","missing required H parameter returns 400 error","payment not provided or insufficient returns 402 error"],"whenToPreferThis":"Use this endpoint when you need to translate an asteroid's absolute magnitude (H) into a physical size estimate — especially when albedo is known or a bracketed range is acceptable. Ideal for planetary defense analysis, impact hazard estimation, and educational or research workflows where you want both size and impact energy from a single call. Prefer over general astronomy APIs when you specifically need the diameter-from-H formula with optional impact energy output in standardized units (megatons, Hiroshima equivalents).","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-10-21T07:20:35.952Z","isFirstParty":false,"canonicalSlug":"space-objects-asteroid-diameter-from-absolute-magnitude-324112d3"}