Exploring The Sun
The Sun
Basically, the Sun is a source of light and heat for life on earth. That’s the easiest explanation for it and probably the most heard. But how about more interesting information? For instance, did you know that the Sun's average distance to the Earth is about 150 million kilometers? That means 1.5 billion soccer pitches can fit in that distance. Also it holds 99.8% of the solar system's mass and is roughly 109 times the diameter of the Earth. Additionally its age is 4.5 billion years. How impressive,
right? You may have heard some of these before but let’s think about what we don’t know.
Actually, humans have always thought about what they don’t know. And the Sun has always been one of the focal points. We have always wondered about its structure. And to understand more about it, space agencies have sent more than 20 spacecraft to space. Let’s look at the recent two of these missions: Solar Orbiter and Parker Solar Probe.
Solar Orbiter
But how will this probe answer all of these? Its principle is to use Venus gravity assists to fly out of the ecliptic plane to study the Sun at high latitudes. It is gradually lifting itself out of the ecliptic plane, ultimately reaching an angle of 24 degrees above the Sun’s equator. In that way it will provide the first images of the Sun’s poles. And it will be only 42 million kilometers from the Sun. It will use its 10 instruments to observe the turbulent solar surface, its hot outer atmosphere and changes in the solar wind. Six instruments are remote sensing, which “see” the Sun and return imagery. The other four are in situ instruments, which work by “touch:” They measure the environment immediately surrounding the spacecraft, including solar wind plasma — the electrified gas streaming from the Sun — and the electric and magnetic fields embedded within it. The ten instruments work together to provide an unprecedented, comprehensive view of our star.
Solar Orbiter is an international cooperative mission between ESA (the European Space Agency) and NASA. The spacecraft was launched in February 2020 and released first images in July 2020. But still it has a lot to do. Its routine science operations are going to begin in November 2021 and they will answer some of the biggest questions in solar science. What drives the solar wind and how does space weather impact the Earth? What controls the Sun’s 11-year activity cycle? How is the magnetic field generated inside the Sun?
Parker Solar Probe
Another important Sun mission is Parker Solar Probe, performed by NASA. This probe was launched from Florida in August 2018. It travels through the Sun’s atmosphere, closer to the surface than any spacecraft before it, facing brutal heat and radiation conditions to provide humanity with the closest-ever observations of a star.
At about 1,400 pounds, Parker Solar Probe is relatively light for a spacecraft, but it launched to space aboard one of the most powerful rockets in the world, the United Launch Alliance Delta IV Heavy. That's because it takes a lot of energy to go to the Sun — in fact, 55 times more energy than it takes to go to Mars.
In order to unlock the mysteries of the Sun's atmosphere, Parker Solar Probe uses Venus’ gravity during seven flybys over nearly seven years to gradually bring its orbit closer to the Sun. The spacecraft will fly through the Sun’s atmosphere as close as 6.2 million kilometers to our star’s surface, well within the orbit of Mercury and more than seven times closer than any spacecraft has come before.
It flies into the outermost part of the Sun's atmosphere, known as the corona, for the first time. Parker Solar Probe has three detailed science objectives:
-Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind.
- Explore mechanisms that accelerate and transport energetic particles.
-Trace the flow of energy that heats and accelerates the solar corona and solar wind.
Corona and Solar Wind
Let’s take a look at the much mentioned corona and solar wind. The corona is the outermost part of the Sun's atmosphere. It extends many thousands of kilometers (miles) above the visible "surface" of the Sun, gradually transforming into the solar wind that flows outward through our solar system.
The material in the corona is an extremely hot but very tenuous plasma. It has a temperature of more than 1 million degrees. While the temperature of the Sun’s surface is around 5,500 degrees, the heat of the corona is still a mystery that couldn’t be solved by the scientists. In spite of its high temperature, the corona yields relatively little heat, because of its low density; the constituent gas molecules are so sparse that the energy content per cubic centimetre is substantially lower than that of the interior region of the Sun. The corona's temperature causes its particles to move at very high speeds. These speeds are so high that the particles can escape the Sun's gravity. This magical movement is called solar wind.
