At first, astronomers thought it was a mistake. They had found a carbon-covered asteroid floating among countless icy bodies distant in our solar system. The newly discovered space rock, which they called 2004 EW95, was something that scientists hoped to have seen in the asteroid belt between Mars and Jupiter. Instead, I was dancing near Neptune.

The discovery, published on Wednesday, suggests that 2004 EW95 is the first of a new class of hidden space objects in the external solar system, in a vast and cold region known as the Kuiper Belt, which still contains many mysteries. The researchers believe that the asteroid was launched from the internal solar system about 4.5 billion years ago, and can provide information on the initial formation of our planets.

Using the Very Large telescope of the European Southern Observatory, Tom Seccull, a PhD student from Queen's Belfast University in Northern Ireland, and his colleagues examined the luminous signatures of the icy surfaces of the belt objects of Kuiper. They noticed something strange about an object that measured nearly 190 kilometers long and was located 2.5 billion kilometers from Earth. Their analysis showed that this object did not share the same icy past as the ice balls floating nearby.

"When we looked at this for the first time, we thought it was wrong," said Seccull, principal author of the article published in the Astrophysical Journal letters. "The rock has been altered by the presence of liquid water."

This probably meant that the asteroid resided in a warmer environment, much closer to the sun. The team also discovered that the asteroid's chemistry was dominated by compounds called ferric and phyllosilicates oxides, which had never been seen before in Kuiper belt objects.

 

The impression of an artist of 2004 EW95, a relic of the primordial solar system, which scientists believe has originated in the asteroid belt between Mars and Jupiter, but now floats beyond Neptune. Credit. Kornmesser/European Southern Observatory

This evidence led the team to conclude that the EW95 of 2004 was formed in the internal solar system and was probably launched into the external solar system when the giant gas planets, Jupiter and Saturn, migrated away from the sun.

One of the prevalent ideas in astronomy is that our solar system has formed in chaos. About 4.5 billion years ago, baby planets and dust disks collided violently for millions of years.

At some point, the gas giants went from their positions in the internal solar system to the external solar system. This has been called the "great grip" hypothesis. The researchers do not know exactly how and at what point the EW95 of 2004 was released from the inside, but they think it coincided with the migration of the gas giant.

"It is a wrong testimony of the initial history of the formation of our planetary system and the sun," said Thomas Puzia, astronomer of the Pontifical Catholic University of Chile and author of the article.

The great movement of Jupiter was crucial to our existence, said Dr. Puzia. Across the galaxy, scientists have found evidence of gaseous giants that have not travelled out, away from their stars. These "hot Jupiters" often avoided the formation of smaller exoplanets, a scenario that could have happened here if Jupiter had not come out.

By finding the 2004 EW95, astronomers now have stronger evidence that objects close to the sun, such as asteroids and gaseous giants, entered the external solar system billions of years ago.

"We are fortunate to be here, because the gaseous giants did not destroy the inner solar system," said Dr. Puzia. "Understand this–why it happened and how it happened–tells us more about our birthplace."