On this year’s list of the top five asteroid hunters in the world, it’s no surprise the top four spots are filled by multimillion-dollar NASA-funded projects. But coming in at number five is a trio of amateurs, Alain Maury, Georges Attard and Daniel Parrott. Maury is a retired engineer and astronomer who moved to Chile from France to better pursue his passion for stargazing. He runs ‘star tours’ to the Atacama Desert, allowing visitors access to his high-powered telescopes and their window onto the dazzling southern skies.
Attard, also a retired engineer, stayed in France. He takes Maury’s data and runs the numbers in his spare time, calculating asteroids’ trajectories, orbits and mass.
Parrott is an American computer scientist who wrote software now used by hundreds of astronomers to catalogue and identify space objects.
Called the MAP project, from their last names, together they have discovered hundreds of asteroids, including near-Earth objects (NEOs) and a few comets besides. They have published papers in serious scientific journals and won accolades for their work and grants to continue it.
Amateur or semi-professional astronomers play a surprisingly large role in the discovery of NEOs. When a new object is spotted, it is followed up and its orbit tracked – and this is where amateurs become vital.
First, the sighting. Far from the romantic image of an astronomer looking through the eyepiece of their telescope somewhere in a dome observatory, modern survey telescopes are powerful and automated machines, using technical cameras such as CCD or CMOS, sophisticated software and machine learning to scan large portions of the sky and report the positions of anything that moves to the Minor Planet Center almost in real time. Once a new object is spotted, it draws the attention of the astronomical community both professional and amateur.
At that point, all that is known is there is something new in the sky. The object must then be observed on several subsequent nights in order to compute its orbit. Once the orbit is known, the object becomes ‘discovered’ – and it is designated and announced to the world. A good orbit calculation means the position of the object can be computed precisely decades or centuries into the future or the past.
This follow-up is often perceived as a secondary, grunt work. But it is essential; without follow-up, there is no discovery. Amateurs often have the time to observe NEO candidates and so they become valuable co-discoverers of NEOs.
The declining cost of relatively large off-the-shelf telescopes, CCD and CMOS cameras, and astronomical software have allowed amateur observers to become more professional in their hobby. In the last few years, the precision of positional measurements in the hands of some amateur astronomers has reached the precision of professional instruments. Parrott’s software is now preferred by many astronomers, even professionals.
Astronomy clubs allow enthusiasts to share equipment and knowledge, and the internet and social media have allowed observers around the world to connect, creating a network of vigilance. Amateur astronomers just need to find their niche, zeroing in on the opportunity created when government-funded surveys leave gaps.
MAP observes from Chile because the southern skies have been without any large NEO survey telescope. Another area where amateur observers excel is chasing the smallest NEOs. Meteoroids a few metres across are sometimes detected only hours before impact. In recent years, four have been discovered with dedicated surveys (Catalina Sky Survey and ATLAS). A fifth, 2022 EB5, was spotted in March this year by Hungarian astronomer Krisztián Sárneczky two hours before it crashed into Earth somewhere north of Iceland. The direct hit was confirmed by infrasonic detection and a few reports from Icelanders who saw blue flashes. With no where near the budget of NASA, Sárneczky’s discovery was enabled by dedicated time on the telescope, years of upgrades to the Hungarian observatory and bad weather at many other professional observatories.
A lot of astronomical image databases are becoming available online, allowing amateur astronomers to fetch the data and look for moving objects. The images were scrutinised by professionals 10 or 20 years ago, but back then the processing power of the best computers was pitiful compared to what an average person has today on their personal computer or tablet. Archival searches are often enabled through public outreach services, such as Galaxy Zoo/Zooniverse or IASC. Many catalogs are freely accessible to anyone. Through these files, amateur astronomers have discovered NEOs or have extended the arcs of known asteroids many years into the past and so improved the orbit calculations.
Sometimes, unexpected help comes from private industry and startups, such as Unistellar’s eVscope. This is an off-the-shelf digital telescope that doesn’t have a classical eyepiece. Instead, images are viewed through a mobile phone or tablet. Unistellar encourages thousands of its users to volunteer their telescopes for science. Home astronomers just need to put the telescope outdoors and the eVscope will be remotely overtaken for a few minutes to observe a given target, such as a nearby NEO. At a given time, data around the world is gathered from these amateur machines and submitted to the Minor Planet Center. Afterwards, eVscopes simply resume their domestic stargazing purpose.
The first NEO to be discovered was Eros. Found in 1989, it is a whopping 17 kilometres across. In 2005 NASA set a goal to discover 90 percent of NEOs with diameters larger than 140 metres within the decade. The dedicated surveys – Catalina Sky Survey, Pan-STARRS, NEOWISE and ATLAS – pushed the discovery numbers up. There are now about 10,000 known NEOs larger than 140 metres and more than 29,000 NEOs in total – and the numbers are rising daily. Yet this still only represents about 40 percent of the estimated asteroid population. Apparently, 20 years and a professional push weren’t sufficient to find them all. The upcoming Vera Rubin Observatory in Chile and NEO Surveyor, a planned space telescope, could change the game. But until then, and probably even afterwards, enthusiastic stargazers at home will continue to play a role in finding, tracking and characterising near-Earth objects.
(Peter Vereš is an astronomer at Harvard & Smithsonian Center for Astrophysics and the Minor Planet Center)