A few days ago, the internet was abuzz with the news that NASA’s Parker solar probe had successfully left Earth’s atmosphere. Costing over $1.5 billion, the Delta IV Heavy rocket carrying the probe lifted off from Cape Canaveral Air Force Station at 3:31 AM the morning of August 13th. The launch of the space probe is gaining attention as engineers proclaim it will be the first-ever mission to “touch” the sun.
The purpose of the probe is to take the most accurate measurements of the sun’s corona to date with the goal of expanding our understanding of the origins and evolution of stars. Primarily, it is thought that the probe will provide invaluable knowledge on the causes and dynamics of solar wind and the accompanying solar particles. In addition, the mission should give more information on the nature of sunspots on the surface of the sun.
A photo of the August 13th launch of the probe at Cape Canaveral Air Force Base. Source: nasa.gov
At the apex of the journey, the Parker probe will come within 3.8 million miles of the surface of the sun. From our perspective, 3.8 million miles is an enormous distance, but on a cosmological scale, it is merely a hair’s breadth away. The probes path will take it well within Mercury’s orbit and the trajectory will bring the probe 7 times closer to the sun than any previous mission. In fact, the probe is planned to go so close to the sun that it will actually spend some time inside the sun’s corona, the halo of superheated gases and ionized particles the extends outward from the surface of the sun.
How To Shoot Something Into The Sun
It seems like it would be easy to send an object directly to the sun. After all, the sun is the most massive object in the solar system and its huge gravitational influence attracts everything. Ironic as it may sound though, it is actually easier to send an object away from the center of our solar system than it is to shoot it into its center.
The reason for this is due to the concept of relative velocity. At any given moment, the earth is moving with respect to the sun at an average rate of 67,000 mph, or about 30km per second. This means that any object that is launched from Earth will also be going about 30km per second with respect to the sun. According to Newton’s first law of motion, the forward momentum of the launched probe is conserved and the probe would naturally tend to an elliptical orbit around the sun, just like the Earth and other planets.
In order to send the probe straight into the sun, after the initial launch, the team would have to find a way to slow down the launched probe so that its velocity is 0 mph with respect to the sun. Then the sun’s gravity could take over and the probe could naturally fall into the sun. Of course, slowing the Parker space probe down from 67, 000 mph to 0 mph would take a very large amount of fuel and energy, too much for NASA to feasible have access to.
So instead, the team is planning on sending the probe into a periodic orbit around the sun, with each pass taking advantage of Venus’ gravitational field to nudge the probe closer to the sun. On September 28th, the probe is scheduled to make its first maneuver to set up its intricate voyage around the sun. Then the probe is set to begin the first of its planned 24 orbits around the sun, reaching the perihelion (spot closest to the sun) of its first orbit on November 1.
Over the next seven years, the probe will continue to inch its orbit closer and closer to the sun until it reaches the target distance of ~4 million miles. During the mission, the probe is predicted to reach speeds of up to 430,000 mph.
The planned trajectory of the satellite is notable as the probe will essentially be in the equivalent of a geosynchronous orbit—the probe will always be hovering over the same spot on the sun. Repeated measurements of the same region of the sun will give us better data about the periodic and long-term behavior of regions on the sun’s surface. “We’re really able to hover and stare at it,” said Nicola Fox, a scientist on the team that launched the probe. Fox also said the probe gave the team”the ability to spend days looking at the dynamics of how one region of the sun is changing — or maybe it isn’t changing.”
In addition to information on the sun, the team is hoping that the probe will also pick up valuable readings on Venus each time the probe nears the planet. Despite being our closest celestial neighbor (apart from the moon), there is still much of Venus that we do not know, such as the reasons for its peculiar rotation and the origins of the runaway greenhouse effect of its atmosphere.
Just as the Greek myth of Icarus taught us, though, one can only get so close to the sun for so long. Eventually, the Parker solar probe will enter into an orbit where it will no longer be in a position to send data back to Earth. Then the probe will continue its dance around the sun as it runs out of fuel and slowly begins to degrade due to the intense heat and radiation. According to Andrew Driesman, Parker solar probe project manager, the probe will eventually disintegrate into a carbon disk orbiting around the sun. There it will remain indefinitely, serving as a monument for a civilization that turned its head to the skies and dared to fly close to the sun.