{ "schema_version": "pointcast.observatory.guide.v1", "topic": "sun", "title": "The Sun", "description": "Follow daylight in El Segundo, understand solar energy, and read space weather without the hype.", "canonical": "https://pointcast.xyz/sun/", "report_endpoint": "/api/observatory/sun", "report_schema": "/observatory/report.schema.json", "reviewed": "2026-10-06", "public_reference": { "name": "El Segundo, California", "latitude": 33.9192, "longitude": -118.4165, "time_zone": "America/Los_Angeles" }, "intro_html": "Follow daylight in El Segundo, understand solar energy, and read space weather without the hype.", "facts": [ { "value": "1,400,000 km", "label": "Solar diameter · reference. Rounded physical diameter." }, { "value": "150,000,000 km", "label": "Mean Earth–Sun distance · reference. Rounded mean distance, not a current range measurement." }, { "value": "5,500 °C", "label": "Photosphere temperature · reference. Approximate visible-surface temperature; not core temperature." }, { "value": "15,000,000 °C", "label": "Core temperature · reference. Approximate central temperature." }, { "value": "11 Earth years", "label": "Solar activity cycle · reference. Approximate sunspot-cycle duration; not a fixed eruption schedule." } ], "sections": [ { "id": "our-daily-star-three-different-stories", "title": "Our daily star, three different stories", "paragraphs": [ "In El Segundo, the Sun can organize a morning walk, a science lesson, and a conversation about energy before breakfast. Those are connected stories, but they need different evidence. A sunrise time describes geometry. A solar-panel estimate describes a system and its assumptions. A space-weather chart describes activity measured far beyond the neighborhood. PointCast brings them together without blending them into one mysterious “solar score.” Start with the practical question you want to answer: when will daylight begin, how might a panel perform, or what is our star doing? The right question tells you which number matters." ] }, { "id": "a-star-in-ordinary-daylight", "title": "A star in ordinary daylight", "paragraphs": [ "The Sun is roughly 1.4 million kilometers across and about 150 million kilometers from Earth. Its visible photosphere is around 5,500 degrees Celsius; the core reaches roughly 15 million degrees Celsius, where fusion powers its light and heat. The familiar disk is therefore not a solid surface you could stand on. Even rotation refuses to behave like a rigid ball: the equatorial region turns faster than the polar regions. These enormous numbers become more useful when paired with scale. Sunlight takes about eight minutes to reach Earth, so even the most immediate-looking sunshine has already completed a long journey. [NASA Science: Sun facts]" ] }, { "id": "sunrise-is-a-definition-not-a-weather-promise", "title": "Sunrise is a definition, not a weather promise", "paragraphs": [ "The everyday phrase “the Sun came up” hides a precise convention: sunrise refers to the Sun's upper edge appearing at a level horizon under assumed atmospheric conditions. Civil twilight begins earlier, when the Sun's center is six degrees below the horizon. Buildings, terrain, clouds, and refraction can change what someone actually sees. A dawn planner should therefore label its times as calculated and keep visibility separate. For El Segundo, show Pacific local time using America/Los_Angeles, including seasonal clock changes. The device's time zone should never silently move a California sunrise into the wrong date for a reader traveling elsewhere. [U.S. Naval Observatory: Rise, set and twilight definitions]" ] }, { "id": "follow-daylight-through-the-year", "title": "Follow daylight through the year", "paragraphs": [ "A daylight strip is a small, useful visualization: dawn, sunrise, solar noon, sunset, and dusk laid across a local day. Compare it with the same date a month earlier. The movement is a chance to ask what the season is doing, rather than merely whether the weather feels warm. For a UES exercise, write a prediction first, then inspect the calculated times. Be careful around clock changes: subtract actual instants to measure duration instead of subtracting clock labels. A one-hour change on the clock is not a sudden one-hour jump in Earth's relationship with the Sun." ] }, { "id": "power-and-energy-are-different-questions", "title": "Power and energy are different questions", "paragraphs": [ "A watt measures a rate. A watt-hour measures an amount accumulated over time. A hypothetical device drawing 100 watts for three hours uses 300 watt-hours, or 0.3 kilowatt-hours. That arithmetic is the foundation of a useful solar-energy page. A panel's nameplate rating does not mean it produces that power every hour of daylight. Orientation, shading, temperature, clouds, equipment, and losses matter. PointCast's simplest calculator should invite users to change assumptions and watch the result move. Label every result as a scenario, not a promise about a specific roof, bill, or installation." ] }, { "id": "historical-sunlight-is-not-a-roof-sensor", "title": "Historical sunlight is not a roof sensor", "paragraphs": [ "NASA POWER offers programmatic access to solar-radiation datasets, including daily surface shortwave energy. Those values can help compare seasons and places, but a gridded environmental product is not a meter attached to your panels. Its time standard also needs attention: local solar time is different from California civil time. PVWatts is a more specialized system-production model, with inputs for capacity, tilt, azimuth, and losses; its API requires a key. Neither model turns an assumed system into a measured one. A good energy report records the dataset, units, interval, model version, and all chosen inputs so another person can reproduce it. [NASA POWER: POWER Daily API] [NASA POWER: POWER API request tutorial] [National Laboratory of the Rockies (formerly NREL): PVWatts V8 API]" ] }, { "id": "a-restless-star-does-not-follow-a-daily-schedule", "title": "A restless star does not follow a daily schedule", "paragraphs": [ "Sunspots provide one way to track the roughly eleven-year cycle of solar activity. The cycle is a broad pattern, not a timetable for tomorrow's eruption. A solar flare is an energetic burst associated with magnetic activity; a coronal mass ejection involves material and magnetic field moving into space. Those terms should not be used interchangeably, and a dramatic image alone does not establish an effect at Earth. Keep the page curious rather than alarmist. Ask what was measured, where the instrument was, when the signal was recorded, and whether the statement describes an observation, a model, or a forecast. [NASA Science: Track the solar cycle with sunspots] [NASA Science: What is a solar flare?]" ] }, { "id": "what-kp-says-and-what-it-cannot-say", "title": "What Kp says, and what it cannot say", "paragraphs": [ "The planetary Kp index summarizes disturbance in Earth's magnetic field. NOAA's estimated three-hour product is useful context for geomagnetic activity, but it is not a local aurora guarantee or an index of how sunny El Segundo feels. A recent observation and a forecast for a later interval deserve visibly different labels. Solar-wind speed and magnetic-field measurements add context, yet their spacecraft source and timestamps matter too. A successful download does not make an old measurement current. On this page, the time of the observation stays beside the value, and a delayed feed is allowed to look delayed. [NOAA Space Weather Prediction Center: Planetary K-index] [NOAA Space Weather Prediction Center: SWPC data access]" ] }, { "id": "exploration-makes-the-invisible-tangible", "title": "Exploration makes the invisible tangible", "paragraphs": [ "The story is bigger than a chart. On December 24, 2024, Parker Solar Probe made a close approach about 3.8 million miles above the Sun's surface, an accomplished event worth separating from any future mission promise. Spacecraft can sample environments that people cannot safely visit, while instruments reveal wavelengths our eyes cannot see. Try treating an image like a reporter treats a quotation: retain its context. What instrument made it? Which wavelength or processing choice produced the colors? Is it a picture, a visualization, or an artist's concept? Those questions add wonder by making the evidence more specific. [NASA Scientific Visualization Studio: Parker Solar Probe: humanity’s closest encounter with the Sun]" ] }, { "id": "make-curiosity-safe", "title": "Make curiosity safe", "paragraphs": [ "Never look directly at the Sun without proper solar-viewing protection. Ordinary sunglasses are not enough. For direct unaided viewing, use undamaged viewers meeting ISO 12312-2 from a reliable supplier and follow their instructions. Never look through binoculars, a telescope, or a camera lens while wearing eclipse glasses; concentrated sunlight can destroy the filter and seriously injure your eyes. Optical equipment requires a suitable filter fitted securely at the Sun-facing end, with expert guidance. The easiest classroom choices are a pinhole projection viewed on a surface, ordinary shadow measurements, or published observatory images. Do not look through the pinhole. [NASA Science: Eclipse viewing safety]" ] }, { "id": "save-a-solar-day-worth-remembering", "title": "Save a solar day worth remembering", "paragraphs": [ "A PointCast “Daylight Print” could turn one day's calculated daylight into original bands of color, with a separate annotation for an actual observation or a clearly labeled energy scenario. A “Space Weather Receipt” could preserve the source timestamps behind a chart. Both should work as free downloads before anyone considers a blockchain. If a future edition is minted, its metadata should say exactly what is owned: a particular digital artwork or record, not sunlight, energy credits, a scientific endorsement, or an investment return. The most valuable collection may be the simplest: a year's worth of careful questions, honest measurements, and better explanations." ] }, { "id": "practical-projects", "title": "Three practical explorations", "paragraphs": [ "A month of daylight
Compare calculated sunrise, sunset and daylight duration for four weekly dates at the same El Segundo coordinates. Keep America/Los_Angeles displayed.
Deliverable: A local daylight mini-almanac.", "Build a transparent energy scenario
Choose hypothetical capacity, equivalent full-power hours and losses. Show every input; compare the result with an alternate assumption rather than claiming a measured output.
Deliverable: A reproducible scenario card with kWh units.", "Follow one space-weather interval
Save a NOAA Kp forecast, then compare the later estimated observation for that same three-hour window. Include both timestamps and any gaps.
Deliverable: A small forecast-verification report, without an aurora guarantee." ] }, { "id": "collectible-ideas", "title": "A shelf of original collectible ideas", "paragraphs": [ "Daylight Print · Original generative SVG plus calculation metadata
Color bands encode calculated daylight duration, with location/date/time-zone printed on the reverse.
No Sun ownership, energy-credit claim, or NASA endorsement.", "Space Weather Receipt · Timestamped report and original chart
Archive one interval with observation/forecast separation and source timestamps.
Make revision history visible; no investment or aurora guarantee.", "Solar Scenario Edition · Original poster with transparent inputs
A hypothetical energy calculation visualized as a clearly labeled educational edition.
Never sell a model estimate as verified generation or carbon reduction." ] } ], "sources": [ { "id": "api_usno", "label": "U.S. Naval Observatory — Astronomical Applications API documentation", "url": "https://aa.usno.navy.mil/data/api.html", "note": "Keyless calculated daily events, noon illumination, primary phase API and parameters. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "flare", "label": "NASA Science — What is a solar flare?", "url": "https://science.nasa.gov/solar-system/what-is-a-solar-flare/", "note": "Flare and magnetic activity context. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "kp", "label": "NOAA Space Weather Prediction Center — Planetary K-index", "url": "https://www.spaceweather.gov/products/planetary-k-index", "note": "Estimated three-hour planetary geomagnetic index and limits. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "nasa_media", "label": "NASA — NASA Images and Media Usage Guidelines", "url": "https://www.nasa.gov/nasa-brand-center/images-and-media/", "note": "Educational/editorial uses, third-party rights, branding, NFT and endorsement restrictions. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "noaa_calculator", "label": "NOAA Global Monitoring Laboratory — Solar calculation details", "url": "https://gml.noaa.gov/grad/solcalc/calcdetails.html", "note": "Approximate Meeus-based geometry, atmospheric limitations, unsupported calculator notice. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "nws_rights", "label": "NOAA / National Weather Service — National Weather Service disclaimer", "url": "https://www.weather.gov/disclaimer", "note": "Public-domain information unless annotated, attribution/official-material distinction and acceptable use. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "parker", "label": "NASA Scientific Visualization Studio — Parker Solar Probe: humanity’s closest encounter with the Sun", "url": "https://svs.gsfc.nasa.gov/14741", "note": "Completed December 24, 2024 close approach, distance and speed. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "power_daily", "label": "NASA POWER — POWER Daily API", "url": "https://power.larc.nasa.gov/docs/services/api/temporal/daily/", "note": "Daily data, UTC versus local solar time and API limits. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "power_tutorial", "label": "NASA POWER — POWER API request tutorial", "url": "https://power.larc.nasa.gov/docs/tutorials/service-data-request/api/", "note": "Keyless solar-radiation query example. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "pvwatts", "label": "National Laboratory of the Rockies (formerly NREL) — PVWatts V8 API", "url": "https://developer.nlr.gov/docs/solar/pvwatts/v8/", "note": "Required API key, PV model inputs, typical-weather estimates and output units. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "rise_definitions", "label": "U.S. Naval Observatory — Rise, set and twilight definitions", "url": "https://aa.usno.navy.mil/faq/RST_defs", "note": "Level-horizon/refraction assumptions; missing rise-set cases; twilight. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "safety", "label": "NASA Science — Eclipse viewing safety", "url": "https://science.nasa.gov/eclipses/safety/", "note": "Solar filters, indirect viewing and optical-device warning. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "solar_cycle", "label": "NASA Science — Track the solar cycle with sunspots", "url": "https://science.nasa.gov/sun/track-the-solar-cycle-with-sunspots/", "note": "Sunspot counts and approximately 11-year activity cycle. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "sun_facts", "label": "NASA Science — Sun facts", "url": "https://science.nasa.gov/sun/facts/", "note": "Size, temperature, distance, fusion, differential rotation. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "swpc_access", "label": "NOAA Space Weather Prediction Center — SWPC data access", "url": "https://www.spaceweather.gov/content/data-access", "note": "Public NOAA data service. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." }, { "id": "swpc_changes", "label": "NOAA National Weather Service — Service Change Notice 26-21", "url": "https://www.weather.gov/media/notification/pdf_2026/scn26-21_Data_Format_Changes_Impacting_SWPC_Products.pdf", "note": "2026 object-array schema and RTSW endpoint/field changes. Reviewed 2026-10-06. Facts may be cited. No asset permission inferred from a page link; inspect individual credits before reuse." } ], "data_sources": [ { "name": "USNO", "location": "El Segundo public reference", "method": "Calculated sunrise, sunset and daylight", "freshness": "Requested local civil date" }, { "name": "NOAA SWPC RTSW", "location": "Active upstream spacecraft named by source", "method": "Proton speed, km/s; newest valid active-source row", "freshness": "Stale after 20 minutes (PointCast policy)" }, { "name": "NOAA SWPC one-minute Kp estimate", "location": "Planetary geomagnetic activity", "method": "estimated_kp; numeric 0–9 estimate, not local aurora probability", "freshness": "Stale after 60 minutes (PointCast policy)" } ], "learning": { "title": "Notice, model, explain", "format": "self-guided; no accreditation or credential", "exercises_html": [ "Keep a shadow clock · 30 minutes
A fixed short upright object, chalk or paper, ruler; observe shadows only.
Mark the shadow tip at several recorded local times without looking at the Sun. Measure lengths and draw a graph. Compare the shortest observed shadow with calculated solar noon; note that sparse samples may miss the minimum.
Deliverable: Time-stamped shadow sketch and uncertainty note.
Check: Clock noon and solar noon need not coincide. Do not claim an exact minimum from coarse sampling.", "Watts into watt-hours · 15 minutes
Calculator and a hypothetical device rating.
Calculate 100 W × 3 h. Convert Wh to kWh. Test a scenario of 1 kW × 4 equivalent full-power hours × 0.8 overall factor.
Deliverable: Two calculations with units and assumptions.
Check: 300 Wh = 0.3 kWh; illustrative solar scenario = 3.2 kWh, not a roof forecast.", "Observation or forecast? · 20 minutes
An archived NOAA observation and a forecast with valid intervals.
Sort each record by issue time, valid time and data kind. Compare the forecast with a later observation for the same interval. Describe the difference without declaring the entire forecast system right or wrong.
Deliverable: A short forecast-verification paragraph.
Check: Compare like intervals and units; retain revisions and unavailable data." ] }, "collectible": { "type": "original SVG study download", "data_encoding": "date + topic only; no observations", "seed": "PointCast/{topic}/{Pacific civil date}/original-study-v1", "hash": "SHA-256 of seed", "blockchain": false, "wallet": false, "nasa_media": false } }