Thanks to Gaia, astronomers got to know more about stars in the galaxy, which act as a backdrop to asteroid observations. These background stars help unravel the asteroid’s positions: the better one knows where the stars are, the more precisely the orbits of asteroids can be computed.
Recently, astronomers have discovered 30 039 near-Earth asteroids in the Solar System. When an asteroid’s track puts it within 1.3 Astronomical Units (au) of the Sun, it is referred to be a near-Earth asteroid (NEA). Approximately one million asteroids have been found in the Solar System thus far, with about a third being near-Earth asteroids. Most of them are located in the asteroid belt between Jupiter and Mars.
Every week, new asteroids are found using ground-based survey telescopes like the Catalina Sky Survey in Arizona, in the United States. They are designed to seek new things moving in front of the background of “motionless” stars while scanning vast sky areas.
More focussed, large telescopes, such as the European Southern Observatory‘s Very Large Telescope (VLT), can then be used for follow-up observations, helping us better understand a ‘new’ asteroid’s path, size, and even composition. Gaia has also helped us better understand the asteroid risk.
Marco Micheli, an Astronomer at ESA’s Near-Earth Object Coordination Centre, said, “Of course, any asteroid discovered near Earth qualifies as a near-Earth asteroid, but many are found far from home. New objects are observed over time, their movements are studied, and with just a handful of data points from different nights, their future positions can be predicted. Depending on the number and quality of observations, this can extend decades, even hundreds of years into the future.”
The Near-Earth Object Coordination Centre (NEOCC), located at ESRIN, Italy, is the organization’s headquarters for asteroid specialists and risk analysts. The team turns on its global network of telescopes to gather observations of newly discovered asteroids and assess the risk of an impact while also chasing “ancient” asteroids that haven’t yet been certified safe.
They are now focusing on 1 425 asteroids with “non-zero” impact potential. These asteroids are organized in the NEOCC’s Asteroid Risk List, which is continually updated and open to the public.
Also, none of these asteroids have been the reason for concern for at least one hundred years. Some of the smaller objects will and do impact Earth – but the most common are also the smallest and have little effect except for creating trails of shooting stars as they burn up in the night sky.
The majority of the massive, dangerous asteroids larger than 1 km across and above have been found, and none are predicted to cause an impact for at least a century. We have plenty of time to research and plan a deflection mission for those that may have an effect in the future, noted astronomers.