A space probe thinks it’s going to fly by a lone asteroid, but discovers a companion (which now turns out to be very special).

Surprisingly, the moon discovered last week around the asteroid Dinkenish does not consist of just two parts.

A few days ago, the Lucy space probe passed by asteroid 152830 Dinkenish. The flyby confirmed what astronomers had suspected for some time, which is that the space rock is accompanied by a very small moon. But not just any moon, as new images show. Dinkinesh’s natural satellite appears to consist of two parts.

Lucy’s mission
The Lucy space probe was launched more than two years ago. The goal is for the probe to visit many asteroids and so-called Trojans over the next ten years. These Trojan horses are the remains of the material from which the outer planets of our solar system were formed. In this way, researchers hope to gain more knowledge about the conditions that contributed to the formation of our solar system more than four billion years ago.

More about the mission
As Jupiter follows its orbit around the sun, it is accompanied by a large group of asteroids, known as Trojan horses, that move in front of and behind the planet. In fact, we’ve never looked at these Trojans up close. But that is starting to change now thanks to the mission of the American space probe Lucy, which launched in October 2021. A mission that, by the way, has been greatly improved over time. Initially, Lucy was supposed to reveal the secrets of six Trojans – Eurybates, Polymel, Leucus, Aurus, Patroclus and Menoetius – and an asteroid from the asteroid belt named Donald Johansson. But it was later discovered that both Eurybates and Polymele have a small moon. This led to a decision to conduct a comprehensive investigation into these satellites. Furthermore, last January, it was decided that Lucy would also treat 152,830 Dinkenish visitors. As a result, the list of space rocks to examine is getting longer and longer.

Last week, Lucy surpassed her first goal: 152,830 Dinkenish. It is an asteroid with a diameter of 790 meters and was discovered only in 1999 due to its modest size. This small space rock follows an elliptical orbit, meaning it is 180 million to 225 million miles from the sun. Dinkenish is the smallest asteroid in the asteroid belt between Mars and Jupiter ever visited by a spacecraft.

Money
The first photos returned from Lucy clearly showed Dinkenish accompanied by a young companion. But now it appears that there is more to this asteroid and its newly discovered satellite than meets the eye. New photos keep coming in all the time. These images now clearly show that the Moon is a so-called “continuous binary object.” This means that it consists of two smaller objects that are physically in contact with each other.

In one row
In short, Dinkenish’s moon consists not of one part, but of two parts. It is easy to explain why astronomers are only discovering this now. In the first images, taken from the closest point, the two parts of the Moon happen to be located directly behind each other from Lucy’s viewpoint. However, the probe took several pictures in the minutes that followed. Only then did the true nature of the moon become apparent.

Calling binary objects
The discovery that the Dinkenish Moon is made up of two parts is remarkable but not particularly unusual. “Contacting binary objects is very common in our solar system,” says researcher John Spencer. “However, we have not often had the opportunity to study these objects up close, and in fact we have never seen one orbiting another asteroid. However, during the flyby of Dinkenish, we saw unusual differences in brightness, which led us to suspect “The asteroid had a moon. But we didn’t expect something so amazing!”

Confusing
This means that dinkenish does not consist of one or two components, but at least three components. “This is puzzling, to say the least,” said lead researcher Hal Levison. “I never thought the system could look like this. What I don’t particularly understand is why the two parts of the Moon are so similar in size. This promises to be an exciting challenge for the scientific community should it be unraveled.”

a trip
Meanwhile, Lucy continues her journey. Dinkenish and its natural satellite are the starting point for the Lucy mission to explore many interesting space rocks over the course of 12 years. The probe will now first set its course for Earth again, then use the gravitational pendulum to head toward asteroid 52246 Donald Johansson. From there, Lucy heads towards her main targets: the Trojans. If all goes according to plan, Lucy will become the first spacecraft to visit these ancient remains of our solar system. The intention is to explore several Trojans between 2027 and 2033.

As Lucy heads toward her next destination, the team will continue to analyze remaining data from the brief encounter with Dinkenish. Because there is still a lot to uncover about this mysterious being. “It’s truly amazing how nature can surprise us with a new mystery,” says team member Tom Statler. “Good science encourages us to ask questions we didn’t know we had to ask.”