Parker Solar Probe
NASA spacecraft on a mission to "touch the Sun" — the first to fly through the solar corona and sample the environment there directly. Referenced in solar-science and solar-wind as the primary mission investigating solar wind origin and coronal heating.
Named after Dr. Eugene N. Parker (1927–2022), who in 1958 predicted the existence of the solar-wind — a paper initially rejected by peer reviewers as "utter nonsense" before being published by Subrahmanyan Chandrasekhar. Parker became the first person to witness the launch of a spacecraft bearing his name in 2018; he died at 94 in March 2022.
Mission Profile
| Parameter | Value |
|---|---|
| Launch | Aug 12, 2018, Delta IV-Heavy, Cape Canaveral |
| Orbit | Solar orbit, 24 total orbits over ~7 years |
| Closest approach | 3.9 million miles (6.2 million km) from Sun's surface |
| Closest approach speed | ~430,000 mph (700,000 kph) — Philadelphia to Washington D.C. in one second |
| Heat shield | 4.5-inch carbon composite; withstands ~2,500°F (1,377°C) |
Historic First (December 14, 2021)
Parker Solar Probe became the first spacecraft to fly through the Sun's corona — the first time any human-made object "touched the Sun." It sampled particles and magnetic fields directly inside the Sun's outer atmosphere, crossing the Alfvén critical surface where the solar corona transitions into the solar wind.
Science Questions
Three long-standing questions Parker is designed to answer, unresolved for over 60 years:
- Why is the corona hotter than the photosphere? The Sun's surface is ~5,500°C but the corona above it reaches 1–3 million °C — a counterintuitive temperature inversion.
- How does the solar wind accelerate? Thermal pressure alone cannot explain observed solar wind speeds; an unknown mechanism (likely magnetic) adds energy.
- What are the sources of high-energy solar particles? Solar energetic particles (SEPs) that pose radiation hazards to spacecraft and astronauts.
Instruments
FIELDS — Measures electric and magnetic fields, waves, and turbulence in the inner heliosphere. Five antennas (four extending beyond the heat shield into direct sunlight, experiencing 2,500°F); made of niobium alloy. Three magnetometers: two fluxgate (large-scale field) and one search-coil (rapid changes at up to 2 million samples/second). Designed by Space Sciences Laboratory, UC Berkeley.
WISPR (Wide-Field Imager for Solar Probe) — The only imaging instrument; images large-scale coronal structures (CMEs, jets, ejecta) before the spacecraft flies through them, linking large-scale structure to in-situ measurements. Uses heat shield as a coronagraph.
IS☉IS (Integrated Science Investigation of the Sun) — Measures energetic particles (electrons, protons, heavy ions) to understand particle acceleration in the corona and inner heliosphere.
SWEAP (Solar Wind Electrons Alphas and Protons) — Counts and measures velocity, density, and temperature of solar wind electrons, protons, and helium ions directly.
Significance
Parker data has already revealed magnetic switchbacks — sudden reversals in the solar wind's magnetic field direction observed close to the Sun — a phenomenon first seen by Ulysses but dramatically better characterized by Parker's proximity. These may be a key part of the solar wind acceleration mechanism.