Our solar system is home to at least half a million asteroids, and almost certainly many more. Asteroids are lumps of rock too small to be regarded as full-scale planets. They were created 4.6 billion years ago at the same time as the solar system itself. So there’s nothing unusual about these home-grown asteroids. But NASA’s recent discovery of the asteroid 1I/2017 U1 has revealed something incredibly exciting and truly unique.
It seems that as a species we’ve been keen to map the stars and other celestial bodies for millennia. The earliest example of this dates back at least 32,500 years. It comes in the shape of a carved fragment of mammoth tusk that seems to show the constellation Orion. Then there are the famous Lascaux cave paintings, about 16,500 years old. They appear to show a representation of the Pleiades star grouping.
Of course today, with our high-powered telescopes and space probes, we can study the skies above in much more depth. This allows us much more detailed knowledge of our corner of the Milky Way. One major project to explore our solar system and beyond is NASA’s New Frontiers mission. The mission includes three different projects.
One of those NASA projects is New Horizons, which sent a spacecraft to the dwarf planet Pluto, a distant body in our solar system. Launched from Cape Canaveral in January 2006, the New Horizons space probe reached Pluto in 2015. It passed within 7,800 miles of the planet in July of that year.
As it passed Pluto, the space probe was able to capture some awe-inspiring images of the planet, giving us never-before-seen views of this object. And it’s worth remembering that Pluto is anywhere between 2.66 billion and 4.67 billion miles from our planet depending on its orbital position.
The second mission in the New Frontiers portfolio is Juno, a project to further explore the planet Jupiter. This involved sending a solar-powered spacecraft, the first of its kind to journey to one of the outer planets. The probe was launched in August 2011, arriving at its destination in July 2016.
The third current New Frontiers initiative is the OSIRIS-REx project. A space probe was launched in September 2016 with the ambitious goal of reaching an asteroid called 101955 Bennu. Once there in 2020, if everything goes to plan, the probe will take samples from the surface of the asteroid. It will then return to Earth with them sometime in 2023.
So, as we have seen, our ability to explore the heavens has progressed in leaps and bounds since the Russian craft Sputnik 1 was launched into orbit around Earth in 1957. That Russian mission triggered the space race between the Soviet Union and the United States. The race included the first manned flight to the Moon and has culminated in NASA’s sophisticated missions.
But what has really whipped scientists and researchers around the world into a state of almost frenzied excitement is an asteroid. Since we know that there are in excess of 500,000 of these in our solar system, such as asteroid 243 Ida pictured here, this might at first sight appear rather strange.
But this is not just any old asteroid. This is actually an interstellar asteroid, the first one ever to have been observed in our tiny part of the universe. Until now, all of the asteroids that we’ve seen, such as Eros illustrated above, are the product of our own solar system, created 4.6 billion years ago at the same time as the planets and everything else in the solar system.
Most of what you might call “our” asteroids are to be found in the main asteroid belt, a mass of rocks spinning around the sun between Mars and Jupiter. They go from an asteroid as big as Vesta, with a diameter of some 329 miles, to the very small – rocks measuring just 30 feet or less.
But this new asteroid is something completely different. It does not originate from our solar system. In fact, it has traveled from another star, and it may have been journeying through space for hundreds of millions of years. And the reason that astronomers are so stirred by this sighting is that it’s the first ever made of an object from outside the solar system.
The first thing that even the non-scientist can spot is that this object looks unlike anything we’ve ever seen in the solar system before. It is an elongated piece of rock about an estimated 1,300 feet long and 130 feet wide, giving it a unique cigar-shape. At first, astronomers thought it might be a comet, but the particular qualities of its orbit scotched that theory.
The object was first spotted on October 19, 2017, by observers using the Pan-STARRS 1 telescope at the Haleakala Observatory in Hawaii. This prompted astronomers around the world to train their instruments on the object. Because it was traveling at 85,700 mph, there was only a short window in which to observe it.
The object’s initial name was 1I/2017 U1, but it’s also been blessed with a far more romantic name, recognizing the fact that it was first observed from Hawaii. That name is ‘Oumuamua, a Hawaiian term meaning “a messenger from afar arriving first.”
In an interview on NASA’s website, Paul Chodas from the Center for Near-Earth Object Studies in Pasadena, California said, “It’s a strange visitor from a faraway star system, shaped like nothing we’ve ever seen in our own solar system neighborhood.” NASA’s Thomas Zurbuchen said, “This history-making discovery is opening a new window to study formation of solar systems beyond our own.”
Observations have shown that as ‘Oumuamua spins, it becomes 10 times brighter than its darkest moment. It turns on its own axis about every seven hours and 18 minutes. Along with its unusual, elongated shape, these properties make it unlike anything that has ever been observed from Earth.
Further describing the nature of ‘Oumuamua, Karen Meech from Hawaii’s Institute for Astronomy said, “This unusually big variation in brightness means that the object is highly elongated: about ten times as long as it is wide, with a complex, convoluted shape. We also found that it had a reddish color, similar to objects in the outer solar system, and confirmed that it is completely inert, without the faintest hint of dust around it.”
By November 20, ‘Oumuamua was rapidly receding into distant space, already about 124 million miles from Earth. However, NASA space telescopes Hubble and Spitzer were still making observations. There are hopes another interstellar asteroid might be spotted soon since an estimated one per year traverses the solar system. Only recently has equipment been sensitive enough to detect such objects.
‘Oumuamua had already sped past Mars by 2017, and it will journey by Jupiter in May 2018. Finally, it will pass Saturn before heading for deep space towards the Pegasus constellation. Then, astronomers hope, we will soon observe another object that has traveled across space from another star.