Astrophysicists predict origins of unexpected space objects in solar system and Alpha Centauri

Interstellar material has been discovered in our solar system, but researchers continue to hunt for where it came from and how it got here. A new study led by Western astrophysicists Cole Gregg and Paul Wiegert recommends Alpha Centauri—the next closest solar system to ours—is a great place to start, highlighting how and why it's a prime target.

The findings were published March 6 in The Planetary Science Journal.

Interstellar objects are astronomical material, like asteroids or comets, not gravitationally bound to a star. They can come from other solar systems and be thrown into interstellar space by collisions or be slingshotted by a planet or star's gravity.

Gregg, a Ph.D. candidate in physics and astronomy, developed a computer model to study our solar system, Alpha Centauri and the interstellar activity—the movement of gas, dust and other space materials—between the two, side by side within our galaxy. Using the physics governing our single-sun solar system, he simulated interstellar activity in Alpha Centauri, a solar system with three suns.

"We know from our own solar system that giant planets bring a little bit of chaos to space. They can perturb orbits and give a little bit of extra boost to the velocities of objects, which is all they need to leave the gravitational pull of the sun," said Gregg. "For this model, we assumed Alpha Centauri acts similarly to our solar system. We simulated various ejection velocity scenarios to estimate how many comets and asteroids might be leaving the Alpha Centauri system."

If Gregg and Wiegert are correct and Alpha Centauri does indeed eject material at a rate comparable to our own solar system, they estimate (charting speed and direction) about one million interstellar objects larger than 100 meters in diameter with origins from this triple-star system are currently within the Oort Cloud (the shell of icy objects, mostly comets, that surrounds our solar system).

This number will continue to climb as Alpha Centauri moves closer to our solar system, with its closest approach expected in approximately 28,000 years in the future.

"Assuming Alpha Centauri is ejecting material, which it should be, there are plenty of reasons to expect some of that material is making its way to us," said Wiegert, a physics and astronomy professor who has discovered more than 80 minor planets, including asteroids and other near-Earth objects.

Western scientist Robert Weryk discovered the first-ever confirmed interstellar object ʻOumuamua' using the Pan-STARRS telescope at Haleakalā Observatory, Hawaii, on Oct. 19, 2017.

ʻOumuamua' is a small, red interstellar object estimated to be between 100 and 1,000 meters long, with its width and thickness both estimated between 35 and 167 meters.

Cause for concern?

The new interstellar activity model also projects as many as 10 meteors originating from Alpha Centauri may be entering Earth's atmosphere every year. These hypothetical meteors would be no greater than 100 micrometers in size and would cause no concern on Earth.

"If our models are right, there is no cause for alarm, because even though these things are probably in our solar system, they're just a tiny, tiny fraction of all the asteroids and other objects that are out there," said Wiegert.

In fact, according to the model, only about one in a trillion meteors that hit Earth might be from Alpha Centauri.

"Throughout the history of astronomy, every time we look at a system, we think of it as a closed system. First, we thought Earth was the center of everything and then we found out we're part of the bigger solar system. Then we discovered we're part of the Milky Way galaxy," said Gregg. "The galaxy isn't a collection of all these individual star systems, rather they should be studied as an interconnected system, one that shares all of this interstellar material among the stars."