The Hubble space telescope has captured some interesting sights in its time throughout space. However, this image recently published from the European Space Agency and NASA is truly something most astronomers have never before seen.
In September 2016, the asteroid 288P got close enough to Earth to allow astronomers a clear shot at it using the Hubble Space Telescope. The 288P asteroid functions as a binary asteroid -- two asteroids orbiting one another. Binary asteroids can easily get confused as comets; both appear to have long tails and bright comas. And 288P is so closely related to a comet that it's the first binary asteroid that qualifies as both, according to the German-led group of astronomers who discovered the traits.
It also clued astronomers in as to what's going on in the binary system.
"We detected strong indications of the sublimation of water ice due to the increased solar heating — similar to how the tail of a comet is created," said Jessica Agarwal. Agarwal works for the Max Planck Institute for Solar System Research in Germany. She's also the team leader and main author of the research paper. The study, titled "A Binary Main-Belt Comet," can be found in the journal Nature.
For decades, researchers believed that the main-belt comets -- those asteroids between Mars and Jupiter showing comet-like activity -- were key parts in figuring out exactly how the Solar System has evolved over time. One of the questions astronomers hope 288P and other binary asteroids can answer is why/how Earth came to have water.
With so many unique behaviors, 288P is the perfect candidate for studies. Also, 288P was found entirely by chance thanks to the Hubble telescope. Astronomers can't logically expect to find a binary with similar properties in the near future.
From their study of the 288P's activity, the researchers concluded that 288P has been a binary system for roughly 5,000 years. The team also thinks that it's accumulated ice since the earliest eras of our solar system.
"Surface ice cannot survive in the asteroid belt for the age of the Solar System but can be protected for billions of years by a refractory dust mantle, only a few meters thick," Argarwal explained. "The most probable formation scenario of 288P is a breakup due to fast rotation. After that, the two fragments may have been moved further apart by sublimation torques."
But is it enough to answer one of astronomy's biggest questions: how did Earth get water? Not quite, according to the research team.
"We need more theoretical and observational work, as well as more objects similar to 288P, to find an answer to this question," said Agarwal.
For now, the team continues to concentrate its study on both the formation of water and also comparing 288P with current theories on how the Asteroid Belt came to be. There are two key theories: 1) the Asteroid Belt is filled with small bodies that failed to become planets or 2) it started out as empty space that filled with planetesimals over the course of centuries.
The animation below from the ESA gives a unique "close-up" look at the binary asteroid.