Despite its almost constant, glaring presence, the Sun is one of the least understood objects in our solar system. For some unknown bizarre reason, its atmosphere or corona is hotter than its surface. The phenomenon contradicts the second law of thermodynamics, a fundamental law of the universe! Also, for some unknown bizarre reason, its magnetic field is indescribably complex: it exemplifies caprice.
We have speculated on the origin and evolution of these idiosyncrasies for almost 60 years now, but speculation will persist to be speculation, it will never materialize into a substantial fact, unless evidence is discovered. Where to best look but at the source? Weary of examining the smoke, NASA is now looking for the fire: it has finally launched a probe…. to the Sun itself!
Let me remind you that this isn’t the first time a probe has been launched towards the Sun. In the 1970s, Helios I and II were the first probes to venture towards our closest star, but while the closest Helios II came to the corona was some 27 million miles, Parker Solar Probe’s final orbit would be only 4 million miles away! This is the closest to a star we will ever be.
Naturally, being so close to the Sun, probes achieve tremendous velocities. The Parker Solar Probe was launched on the 12th of August 2018, and in its final orbit around the Sun, it will blow past it at a mind-boggling 430,000 mph, making it the fastest man-made object in history. It will travel at 200 km/s, meaning that it could travel from Washington, D.C. to Philadelphia in less than a second. The record that the Parker Solar Probe will break is currently held by, as you might have guessed, Helios II, which topped out at a velocity of 150,000 mph. The Parker Solar Probe will travel at least three times faster.
This is natural because both probes will have operated well within the Sun’s “gravity well”. A small object traveling around a massive object behaves as though it is falling into a well or valley: the deeper it is, the steeper the slope, the faster it descends, and the harder it is to climb and escape. The Sun accounts for 99.8% of the mass of our Solar System. This makes it an enormous well in which not only supermassive planets like Jupiter and Saturn helplessly fall, but even the Oort clouds 186 billion miles away, so the “slope” is as steep as it can get in its proximity.
One would then infer that, due to its unyielding pull, a journey in the Sun’s direction would offer the least resistance, so a probe would need to be launched with a small amount of energy. However, this would be a terrible mistake. In fact, sending a probe to the Sun requires 55 times more energy than sending one to Mars! To achieve its staggering acceleration, the Parker Solar Probe, launched from Cape Canaveral Air Force Station, Florida, underwent three rocket stages. But why?
Embarking on a journey to the Sun requires more impetus for the same reason that you must jump with a greater force from a moving vehicle to achieve a longer leap. The Earth is sprinting around the Sun at 67,000 mph, so to leap towards the Sun, we must negate this sideways motion first, just as you must negate a car’s linear motion to leap perpendicular to it.
This is the first mission to be named after a living person. The probe was originally called just “Solar Probe”, but was later renamed after the profound solar astrophysicist Eugene Parker, who coined the word “solar winds”. Solar winds and flares are the most powerful explosions in our solar system, which radiate in their surrounding tempestuous waves of plasma and energetic particles. These emissions not only damage our satellites, but also electronics on Earth’s surface, often causing large-scale blackouts. Parker speculated that the spouts of astronomically high energy were caused by the Sun’s capricious magnetic field. However, as mentioned, speculation is futile without evidence.
To obtain this evidence, the probe will first perform a delicate maneuver: on the 28th of September, it will gradually slow down and achieve an orbit around Venus. It will use the planet’s gravity to “slingshot” itself towards the Sun. This is called a gravity assist. It is analogous to using the kinetic energy derived from falling down a valley to accelerate, climb the other side and escape. This saves the probe a lot of precious fuel.
The probe is predicted to achieve its first close orbit around the Sun on November 1. It will then fly back towards Venus, which will slingshot it even closer to the Sun. A total of 7 assists from Venus will send it closer and closer to the Sun through each of the 24 orbits it will make until it’s so close to the star that it will be unable to escape its pull and loop around again. On December 19, 2024, at the end of its mission, the probe will achieve its closest orbit – only 3.38 million miles away from the corona. For perspective, the Earth, on average, is 93 million miles away from the star.
Close to the Sun, the probe will perform radial scans: by matching its velocity with the Sun’s rotation, it will be able to examine a particular region. This is how geosynchronous satellites work: by rotating with the same velocity at which the Earth rotates, a satellite above can carefully surveil a particular region. The probe will study the same region of the sun’s corona for 10 days.
Of course, while operating so close to the Sun, the probe will bear its full brunt: infernal temperatures of 2,500 ᵒF and an incessant bombardment of energetic particles. To prevent the delicate instruments from literally melting and frying, NASA installed a 4.5-inch-thick carbon-carbon composite shield and highly reflective aluminum plates to minimize absorption. The probe is truly a thermal engineering marvel.
The probe will burn its fuel not only to propel itself, but also to twist and turn the shield. If it didn’t, the mission, which ends mid-2025, could potentially be extended. Hopefully, during its 7-year pilgrimage, the probe will seek and find the truths we desire, unraveling the star’s mysteries, turning the frustrating unknowns into irrefutable knowns. However, why are these truths so essential to us? Why are we so adamant to seek them?
The mission cost NASA a whopping $1.5 billion, but the discoveries will be worth every penny. The probe has carried with it a panoply of scientific instruments: instruments to study magnetic fields, instruments to study the spewed plasma and particles, as well as a camera to take breathtaking images of the Sun as we have never seen before.
According to NASA, the mission is essential because, first and foremost, “the Sun is the only star we can study up close. By studying this star we live with, we learn more about stars throughout the universe.” Remember that this is the closest we will ever be to a star, so the data the probe accumulates may hold profound insights into not only the cause of winds and flares, phenomena that cost millions of dollars, since they damage and shorten the lifespan of satellites, but also the sun’s 11-year cycle – from being fanatically turbulent to gradually achieving tranquility, and then back to turbulence again. The probe will record a wide spectrum of stellar activity. We might very well find out why the corona is hotter than the Sun’s surface.
Stars are the universe’s foremost sources of energy, and the Sun is the Earth’s foremost source of energy. The Sun’s heat and light are indispensable to Earth’s flora and fauna. With that in mind, the second reason why NASA believes the discoveries are essential is that “the more we know about it, the more we can understand how life on Earth developed.” For this reason alone, the mission is revolutionary.
A fortuitous consequence of the mission is that the probe will also be able to study Venus. Astronomers agree that there has been a dearth of Venus missions, but Parker Solar Probe, during its visits, will provide astronomers with extensive data about the planet’s composition and other peculiarities. And let’s not forget, breathtaking images the like of which we have never seen before.
Eventually, the probe will run out of fuel. At this point, the shield will find itself unable to move and protect the instruments. Each and every part of the Parker Solar Probe will wither and melt away until only its carbon shield remains. During a NASA news conference, Parker Solar Probe project manager Andrew Driesman of the Johns Hopkins University Applied Physics Laboratory perfectly summarized the momentous or, perhaps, as some might argue, grim implications of the mission when he said: “In hopefully a long, long period of time — 10, 20 years [whenever the spacecraft runs out of fuel and breaks apart] — there’s going to be a carbon disk floating around the sun in its orbit…It’s anyone’s guess how long it could circle our sun as a lonely reminder that the star once fostered humans who developed the technology to reach out and touch it.”
- NASA.GOV (Link 1)
- NASA.GOV (Link 2)
- NASA.GOV (Link 3)
- Johns Hopkins University Applied Physics Laboratory