2262: Parker Solar Probe
|Parker Solar Probe|
Title text: It will get within 9 or 10 Sun-diameters of the "bottom" (the Sun's surface) which seems pretty far when you put it that way, but from up here on Earth it's practically all the way down.
This is an informative comic meant to represent the relative distances of astronomical objects relative to the Parker Solar Probe. It also shows where the probe will be in 2025 if its mission continues going according to plan. As explained by the caption at the top of the image, the distances between entities on the chart is drawn to scale; the sizes of said entities, however, are not, which is humorously showcased front-and-center by Cueball and Megan being shown as Earth-sized.
The Parker Solar Probe is a robotic spacecraft launched by NASA in 2018 with the mission of repeatedly probing and making observations of the outer corona of the Sun. It travels in an elongated orbit that passes close to the Sun and sometimes passes near Venus, arranged such that Venus nudges the orbit slightly in each pass to bring the probe's perihelion (the lower end of its orbit) closer and closer to the Sun. Two days before this comic was published the probe again passed through perihelion, establishing new records for closeness to the Sun (0.12 AU) and speed (244,225 mph). By the end of the probe's planned lifetime in 2025, it will pass within 0.046 AU (6.9 million km), or about 5 solar diameters, of the Sun's center, at a speed of 430,000 mph (690,000 km/h). The title text incorrectly states this distance to be 9 or 10 solar diameters measured from the Sun's surface.
Helios 2 was a solar probe launched in the 1976 that formerly held the records for closest man-made object to the Sun and fastest man-made object. Both records were surpassed by the Parker probe in 2018.
Cueball and Megan are standing on Earth. The way this diagram is drawn, they look like they could fall off Earth toward the Sun -- hence the comment "Careful!" -- though the joke is that in real life they would fall toward the center of the Earth, not toward the Sun. Also the surprise for many people is that it is much harder to reach the sun than Pluto. Because we already travel so fast here on Earth, and to reach the sun this speed has to be reduced, which is a larger speed difference than the one needed to escape the Sun's gravity well. If you could "fall" off Earth, you would just keep the approximately same distance to the Sun, but drifting slowly away from Earth.
The title text says the probe will get within 9 or 10 Sun-diameters of the Sun's surface. This is a bit of a mistake: it will actually get within that many Sun-radii (only 4½ or 5 Sun-diameters) of the center of the Sun, which corresponds to 4 or 4½ Sun-diameters above its surface. All the same, the title text makes the point that "Sun-diameters" (or "Sun-radii", for that matter) sounds like an astronomical distance, until you use the same scale for other distances. The distance from the Earth to the Sun is approximately 106 Sun-diameters; by that scale, 4 Sun-diameters is indeed "practically all the way down". Below is a table showing these and other distances using more common units of measurement.
|Object||Perihelion [km]||Perihelion [AU]|
|Earth||147,095,000 km||0.98 AU|
|Venus||107,477,000 km||0.72 AU|
|Mercury||46,001,200 km||0.31 AU|
|Helios 2||43,432,000 km||0.29 AU|
|PSP (now)||18,600,000 km||0.124 AU|
|PSP (2025)||6,900,000 km||0.046 AU|
|Sun Radius||696,342 km||0.0047 AU|
- [A tall, but very narrow box with Earth at the top, with Cueball and Megan standing precariously "on top" of Earth on each side of the center, trying to keep their balance. At the very bottom is shown a slice of the Sun. Between Earth and the Sun the two inner planets and two spacecraft are depicted with relation to their distance from the Sun. The spacecraft closest to the Sun is shown two times at different times, as it moves closer and closer to the sun. All 7 objects have labels close to them. The largest distance is between Venus and Mercury, with the Earth-Venus distance the second longest. The distances between the objects below Mercury are much shorter. There is a caption above the slim panel:]
Looking down toward the Sun
and the Parker Solar Probe
(Distances are to scale, sizes are not to scale)
- Cueball: Careful!
- Helios 2 (1976)
- Parker Solar Probe (today)
- Parker Solar Probe (2025)
(Not to scale)
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