The Sun concentrates 99.8% of all the mass of the solar system. The rest is made up of all the planets, comets and asteroids that orbit around it, so it might seem that it should be easy, almost trivial, to fall to the Sun, to fall to its surface, but this is not the case. Especially if your starting point is Earth or any of those planets, comets, and asteroids.
The Earth, in its translation movement around the Sun, that movement that gives us winters and summers and, of course, years, moves at about 30 km/s and always tangentially to the direction of the Sun or, like a crab sideways The fact that the Earth is moving at this speed means that everything on it is moving too , including all the rockets that take off from its surface. It’s exactly the same as a moving train: everything inside it moves at its speed, and if you throw a stone out of a window, it will keep moving at the speed of the train. This will mean that if we launch a rocket in the direction of the Sun, that is, towards the interior of the orbit, it will have, in addition to the speed due to its propellers, the speed and the direction in which the Earth was moving at the time of takeoff and for Therefore, it will end up passing by without reaching its objective: the surface of the Sun. To avoid this, it would be necessary to cancel this default speed of the Earth, launching that rocket in the opposite direction to the movement of the Earth’s translation and giving it that speed of 30 km/s. Doing this we would get the rocket to stay still, or at least still with respect to the Sun, and then start its free fall movement .
But, as you can imagine, accelerating a rocket until it reaches 30 km/s, a speed at which a trip between Madrid and New York would take just over three minutes, is something that requires a lot of energy, specifically 55 times more energy than needed to send that same rocket all the way to Mars and far less than needed to get out of the Solar System entirely. Specifically, it is enough to add 11 km/s to the initial speed of the Earth to take a rocket to the confines of the Solar System, that is, it is enough to give it a third of the speed necessary to take it to the center of the Solar System, which is much closer and dominated by a giant ball of gas and plasma.
It is for this very reason that we have sent more space missions to the outer solar system than to our star . The most recent of these missions, NASA’s Parker Solar Probe, is now on track to become the closest mission to the Sun, coming within 6.5 million kilometers of the Sun’s surface in 2024 or photosphere , about 7 times closer than any probe has come so far. This probe made headlines last December for having “grazed” the Sun. Before ending its days colliding with the sun, it will become the fastest human-made object in history, reaching about 192 km/s.
To achieve this, it will receive seven gravitational pushes from Venus that will decrease its tangential speed, but increase its total speed, bringing the probe closer and closer to the Sun. Normally these gravitational pushes are used for the opposite, to increase the tangential speed and lead to the corresponding probe to orbits further away from the Sun. This is what the New Horizons probe managed to do when it passed close to Jupiter on its way to Pluto.
During its approach to the surface of the Sun, the probe will study the region known as the solar corona, a region where the plasma can reach a temperature of one million degrees Celsius and which extends for millions of kilometers. The solar corona is where phenomena such as the solar wind are generated, the reason why Mars has lost a large part of its atmosphere in the last billion years and the cause of the auroras that can be observed near the poles here on Earth. The same solar wind that was detected in 2010 by the instruments aboard the Voyager 1 probe as it sailed through the void on the outskirts of the Solar System, beyond the orbit of Pluto, 17 billion kilometers from Earth and the Sun , or 116 times the distance between planet and star.
And yet, when the Parker probe ends its days wasting away on the surface of the Sun, decades after we humans learned to get out of our insignificant solar system, we will have finally managed to reach the heart of the only bit of the universe that we can, yet for centuries and perhaps millennia to call home.
