Interstellar object Omo Amwa, has been puzzling scientists since its surprise arrival in the solar system in 2017. Now two American astronomers think they have solved one of the long-standing mysteries of this space rock.
The origin of Omoamwa
At first it was thought that this rock was an asteroid. Later, this possibility was revised to a comet, and some even considered it an alien spaceship.
The 200-meter-long Umu’amoa approached the center of the solar system in late 2017. During its short visit, the rock traveled up to 24 million kilometers from the Earth, which is about 62 times the distance from the Earth to the Moon. A few weeks after its discovery, it disappeared again.
Observations made during this short period of time proved that Omoamoa is in an orbit that astronomers call a hyperbolic orbit. Its boomerang-shaped path indicates that the rock is not native to our solar system, but just passing through the Sun’s neighborhood and may never be seen again.
As the first interstellar object ever observed, Omu’amoa caused a lot of excitement. This passion has prompted astronomers around the world to delve into the available data to learn all there is to know about the object.
The mystery of the strange speed of Umoamwa
One of the questions scientists have been trying to answer concerns the speed of Umu’amoa, which appears to increase as the rock orbits the Sun.
Large objects, such as planets and stars, can exert a gravitational pull on smaller objects, including comets and asteroids, which increases their speed. But in the case of Umu’amoa, which was traveling at 87 kilometers per second, three times faster than a typical comet in the Solar System, these gravitational shocks could not explain the observed acceleration.
This acceleration led many scientists to conclude that Omu’amoa must be a comet rather than an asteroid. Comets in the Solar System get extra momentum from water and dust that evaporates from their icy cores and heat up as they get closer to the Sun.
However, these comets are famous for their spectacular trail, which glows as a result of the gas ejection process. But Umoamwa had no sign of a tail.
Many scientists have tried to explain the mechanism of Umuamoa’s acceleration, but all the theories presented have significant flaws. In a new study, Jennifer Bergnerassistant professor of chemistry at University of California, Berkeley and Daryl Seligmana National Science Foundation postdoctoral fellow at Cornell University, presented a new theory that they believe may finally end the mystery.
“I’ve been trying to explain the possibility of an outgassing for several years,” Seligman told Space. At first, I thought maybe too much dust during outgassing [برای ایجاد دنباله] do not exist We later thought that perhaps the trail was made of more volatile material than we see in normal comets, such as hydrogen, nitrogen, or carbon monoxide. But in each of these explanations, there were scientific problems.”
For example, hydrogen needs very cold temperatures to freeze in objects the size of Omoamoa, and scientists don’t expect such temperatures inside the dense molecular clouds where these objects form, Seligman said. He added that there is not enough nitrogen in the Milky Way to provide the expected gas for such objects in the galaxy.
Seligman and Bergner now theorize that there may not be anything extraordinary about the Omoamoa composition.
Instead, the object has been subject to extrasolar processes, and astronomers know nothing about it from their observations of inner comets.
“A plume moving through the interstellar medium is essentially heated by cosmic radiation, resulting in the formation of hydrogen,” Bergner said in a statement. We thought: If this is happening, can it really be trapped in a structure? So that when it enters the solar system and starts to heat up, it releases that trapped hydrogen?
The result of recent studies
The team’s calculations showed that, theoretically, the force from the escaping hydrogen could explain Omuamoa’s strange acceleration.
Astronomers even found experimental studies from 40 years ago that showed ice colliding with high-energy particles, such as those found in cosmic rays, could strip molecular hydrogen from water ice and trap them inside a block of ice.
“What’s beautiful about Bergner’s idea is that it explains exactly what should happen to interstellar comets,” Seligman said. We’ve had all kinds of crazy ideas to explain Omo’amoa’s acceleration, like hydrogen ice mountains and other crazy things, and this theory is just the most general explanation.
Although Umu’amoa has left our solar system forever, Seligman hopes that new interstellar visitors will soon be discovered that will help astronomers answer remaining questions and also open a new window into other star systems in our Milky Way galaxy. New telescopes that improve the results of these investigations are expected to be available within the next decade.