Shooting For The Stars

Our sun is far more complex than what we see or know about it. There is so much more to discover, to learn and know about this gigantic ball of fire. The space in which the planets orbit seems to be empty, however, it’s not. It’s full of matter from the sun. The sun generates powerful magnetic fields that rise above the surface in giant loops and when they clash it triggers a storm of superhot highly charged particles blasting out into the space known as the solar wind. Even though the solar wind is invisible, we can still see it encircling the poles as the Aurora, which is very beautiful but reveals the enormous amount of energy and particles that cascade into our atmosphere. Astronauts in space can see it but only when they close their eyes!

Image of the sun showing the hot temperature of the corona (in lighter colours) compared to cooler temperatures of the surface of the sun (in darker colours).

Disturbances in solar wind shake earth’s magnetic field and pump energy into the radiation belts, part of a set of changes in near earth-space known as Space weather. Space weather can change the orbits of satellites, shorten their lifetimes, or interfere with onboard electronics. High exposure of these radiations could kill astronauts, so scientists have been trying from decades to find out more about what causes space weather and how to predict it in order to protect the satellites that we depend upon.

Now to have a strong understanding of the mechanisms that drive that wind toward us, NASA is heading out to discover the surface of the sun from the closest distance ever achieved till today.

The Parker Solar Probe was launched with delta IV-upper stage heavy rocket from Cape Canaveral air force station, Florida on 12th August 2018 to unlock the mysteries of the sun’s atmosphere. This mission is named after renowned physicist Eugene Parker, who predicted the existence of solar winds in 1958. This is the fastest machine ever built and at the closest approach, it hurtles around the sun at 430,000 mph and that’s about twice as fast as any spaceship has ever travelled before.

Eugene. N. Parker, American Solar Astrophysicist.

Here’s a short and simple explanation on how it works:

Indeed, the satellite can travel at great speed, but its whole flight plan is actually about slowing down. The rocket carrying the solar probe will fire in the direction opposite to the earth’s orbit. That will slow down the probe so it falls towards the sun, rather than speeding out into the solar system. Throughout its journey the satellite will zoom close to sun 24 times between 2018 and 2025, gathering a plethora of information about the sun’s outer atmosphere (corona), its structure, magnetic and electric fields as well as the energetic particles cruising near and away from earth’s star.

 

NASA’s Parker Solar Probe – The fastest spacecraft ever which was launched on midnight of Aug 12, 2018

During one of its revolutions, it will reach the sun’s atmosphere as close as 3.8 million miles, which is seven times closer than any other spacecraft has ever achieved before. To perform this psychedelic operation safeguarding the spacecraft and its instruments from extreme conditions and temperature fluctuations is crucial. The key to understanding why it doesn’t melt is understanding the concept of heat versus temperature. Counterintuitively, high temperature does not always translate to actually heating another object. Temperature is the measure of how fast the particles are moving but heat measures the amount of energy that has been transferred. Particles might be moving fast (high temperature) but what if there are very fewer particles to interact with an object. It would simply mean that the temperature of the object doesn’t increase to a high extent. Think of this difference by imagining your hand in a hot oven versus in a boiling pot of water. You will find that your hand can withstand a significantly larger amount of temperature in the oven than in the boiling water (Don’t try this at home!) because there are very fewer particles interacting with your hand and thus cannot effectively transfer heat. The corona through which the Solar Parker Probe flies has an extremely high temperature but very low density, so even though the surrounding temperature across the sun would be several million degrees, the surface of the spacecraft that faces the sun will only get heated up to around 2500 0C. Additionally, to beat the heat, it’s armed with a 4.5-inch-thick carbon composite shield which keeps the surface of the satellites to pretty cool room temperature of 30 0C.

Despite the strong gravitational pull from the sun, it’s actually very hard to fly towards it. It takes almost 55 times more energy to go to the sun than it does to go to mars. To compensate for it, the probe will pass Venus seven times for “gravitational assist” a manoeuvre which is also called as “slingshot”.

Trajectory paths of 24 revolutions and 7 gravity assists made by the NASA’s Parker Solar Probe satellite

Space missions usually use this manoeuvre to accelerate toward deep-space destinations by flying in the same direction as a planet. But the parker probe uses this trick differently. It’s using Venus’s gravity to slow down by flying in front of Venus. As the probe loses momentum, the Sun will pull it closer with its gravitational force, and here’s where it becomes the fastest machine ever. The closer it gets to Sun, the faster it will go.

The parker solar probe will reach its final orbit in 2025 and then the researchers can be able to finally solve the two longstanding mysteries: how the solar wind is accelerated and why the Sun’s outer atmosphere is so much hotter than the solar surface. It’s no wonder that scientists have been working on this project for almost 2 decades because of its beautiful yet very complex trajectory followed by the satellite. This mission truly marks humanity’s first visit to a star that will have implications not just here on Earth, but how we better understand our universe.

Stay tuned as we come back soon with another great tale from space.

Shyam D R

Executive member

Amateur Astronomy Club NITK

 

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