Have you ever seen a red aurora? If you live in the northern or southern latitudes, you might be familiar with the green and pink curtains of light that sometimes dance in the night sky.
These are caused by the solar wind, a stream of charged particles from the sun, interacting with the Earth's magnetic field and atmosphere.
But what if you see a red glow that looks like an aurora, but is not caused by the sun? That is exactly what some astronomers and photographers have witnessed in recent years, and the culprit is none other than SpaceX, the private space company founded by Elon Musk.
This reduces the cost and environmental impact of space exploration, but it also has some unintended consequences. One of them is the creation of red auroras, or "SpaceX auroras" as some call them.
The red auroras are caused by the second stage of the Falcon 9 rocket, which is the part that carries the payload to its final destination.
After releasing the payload, the second stage performs a deorbit burn, which means it fires its engines to slow down and reenter the atmosphere, where it burns up and disintegrates.
This is done to avoid creating more space debris, which could pose a threat to other satellites and spacecraft.
However, as the second stage descends, it passes through a layer of the atmosphere called the ionosphere, which is a region of electrically charged gas molecules, mainly oxygen.
The ionosphere is important for radio communication, as it reflects and refracts radio waves. It is also where most auroras occur, as the solar wind excites the oxygen ions and makes them emit green and red light.
The problem is that the rocket exhaust, which contains water and carbon dioxide, provides extra electrons that can recombine with the oxygen ions, turning them back into atoms.
This process releases photons, or light particles, at the same wavelength as red auroras. The result is a bright red glow that can be seen from hundreds of miles away, especially with a camera.
Why Scientists Are Concerned About the Red Auroras
The red auroras might look beautiful and harmless, but they are a sign of a disturbance in the ionosphere.
The rocket exhaust creates a temporary hole in the ionosphere, which can affect the propagation of radio waves.
This could have implications for navigation, communication, and astronomy, as well as for the study of the ionosphere itself.
According to Jeffrey Baumgardner, a space physicist at Boston University, the red auroras are a well-studied phenomenon that occurs when rocket engines fire in the altitude range of 200-250 kilometers (124-155 miles).
He said that the effect is similar to a solar flare, which can also cause ionospheric holes and radio blackouts.
However, he added that the impact of the SpaceX rockets is not well understood and that more research is needed to assess the potential risks and benefits.
One of the challenges is that the red auroras are not easy to predict or monitor. They depend on the timing, trajectory, and altitude of the rocket launches, as well as on the atmospheric conditions and solar activity.
They are also not visible to the naked eye, and can only be detected by specialized instruments or cameras.
This makes it difficult to measure their size, shape, and duration, and to evaluate their effects on the ionosphere and the radio waves.
Another challenge is that the red auroras are not unique to SpaceX rockets. Other rockets, such as the Titan IV, have also been known to cause them in the past.
Moreover, as the demand for space launches increases, more rockets from different countries and companies could create more red auroras in the future.
This could pose a problem for the coordination and regulation of space activities, as well as for the preservation of the natural environment.
