← INDEX — FIG. 00 — 24 DECEMBER 2024, 11:53 UTC
9.86 R☉ · 192 km/s
CORONA
PARKER SOLAR PROBE AND SOLAR ORBITER
The Sun is the hardest place in the Solar System to reach.
BEGIN — CHAPTER 01 →CH.01 / 08 — THE COSTLIEST DESTINATION
To fall into the Sun, you first have to stop
Reaching the Sun means cancelling the Earth's 29.78 km/s.
Parker used seven Venus flybys.
LOWERING THE PERIHELION FROM 1 AU
v⊕ = √(μ☉/r⊕) · vaphelion = √(μ☉ · 2rp / (r⊕(r⊕ + rp))) · Δv = v⊕ − vaphelion
Heliocentric speeds.
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CH.02 / 08 — THE RECORD THAT LASTED 42 YEARS
Helios: a third of the way to the Sun
Helios 2 reached 0.29 AU in 1976.
Going closer needed a single sunward shield.
CH.03 / 08 — PARKER SOLAR PROBE
685 kilograms, the biggest rocket, and Venus seven times
Parker launched in 2018: 685 kg, 24 orbits in seven years.
On 28 April 2021 Parker flew through the corona.
CH.04 / 08 — THE THERMAL PROTECTION SYSTEM
1,400 °C on the front, room temperature behind
The shield is 11.43 cm thick and rated to about 1,377 °C.
The temperature depends on distance and on α/ε.
EQUILIBRIUM TEMPERATURE OF A SUNLIT PLATE
S(r) = S⊕ (1 AU / r)² · α S = ε σ T⁴ ⇒ T = (α S / ε σ)1/4
Flat plate facing the Sun.
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CH.05 / 08 — THE FASTEST THING EVER BUILT
Christmas Eve 2024: 6.16 million km, 192 km/s
On 24 December 2024 Parker passed 6.17 million km from the surface at 192 km/s.
Kepler's laws explain the speed.
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CH.06 / 08 — LOOKING DOWN ON THE POLES
Solar Orbiter: not the closest, but the first to see the poles
Solar Orbiter has telescopes looking at the Sun through its shield.
Solar Orbiter saw the Sun's south pole in 2025.
CH.07 / 08 — LEGACY: FIFTY YEARS OF GETTING CLOSER
From Helios to the corona
Bring your own shadow.
CH.08 / 08 — REFERENCES