The space rock Phaethon is not a comet, but it behaves like a comet. However, this identity crisis seems to be explainable now.
Comets consist of debris and ice. As they get closer to the sun and warm, the ice lying just below the surface evaporates. Water vapor rushes away from the comet, carrying dust and rocks with it. This creates a very distinctive comet’s tail. The comet’s brightness also increases, because everything that releases gas and dust around it reflects sunlight.
But in addition to comets, there are also asteroids. They also occasionally venture too close to the sun, but then don’t make a great show. After all, they are mainly made of stone and contain little or no ice at the most. Thus, there is not much to evaporate, no tail is created and the stone does not light up either.
It’s a logical story. But then there’s Python. A 5.8-kilometre asteroid lights up as it approaches our parent star. “Phaethon is a strange creature that becomes active as it approaches the sun,” said researcher Joseph Masiero.
how is that possible? Phaethon only takes 524 days to orbit the sun and has done so many times before. Space rocks even venture inside Mercury’s orbit and heat the surface to about 750 degrees Celsius. Any water, carbon dioxide, or carbon monoxide ice that may have been on the surface for a long time must evaporate. However, this space rock, which has little or no ice, emits something close to the sun, which increases its brightness. Masiero and his colleagues now think they know what it is: sodium.
below the surface
Sodium is very abundant in asteroids. It can easily evaporate at the temperatures that Phaethon is exposed to near the sun. It is possible that all the sodium on the surface was lost in this way long ago. But deep inside the asteroid is sodium, which heats up near the sun, evaporates and finds its way out through cracks in Phaethon’s crust.
And when this sodium rushes away from the Phaethon, it likely carries dust and debris with it. “Planetary planets like Phaethon have weak gravitational pull, so it doesn’t take much force to move debris off the surface or fractured rock,” said study researcher Bjorn Davidson. “Our models indicate that very small amounts of sodium are sufficient for this.”
from your ship
So the sodium-induced activity of Phaethon may also help explain one of the most famous meteor showers: Gemini. It has been known for some time that this meteor shower that appears every December can be traced back to Phaethon. The space rock leaves behind debris and dust in its orbit, and as the Earth moves through it, these debris particles enter the atmosphere, where they encounter great resistance, warming the air around it and igniting it. From the surface of the Earth, we see it as a lightning-fast streak of light in the night sky, which is popularly called a shooting star. The new research now suggests that these debris particles are released from the Phaethon via deeper sodium evaporation.
The suspicion that sodium is responsible for the activity in Phaethon is supported by experiments. Researchers took small pieces of a meteorite that struck Mexico in 1969 that appears to have come from an asteroid similar to Phaethon. They then exposed those meteor fragments to the temperatures Phaethon experiences near the sun. and yes; Sodium was lost, while the other elements remained. “It indicates that the same thing is happening in Phaethon,” researcher Yang Liu said.
The research puts more pressure on the classification of small objects in our solar system. Now these objects are classified as asteroids or comets depending on the amount of ice they contain. But perhaps we should look not only at ice, but also at other elements that evaporate at high temperatures. “Our latest discovery is that – if conditions are right – sodium can explain the nature of some active asteroids,” Masiero said. “And that makes the spectrum between asteroids and comets more complex than we thought.”