Last week, the European Space Agency released the above Image of the Week from the Hubble Asteroid Hunter project. It shows an asteroid passing in front of the Crab Nebula, M1, an image found in the ESA HST archives by citizen scientist Melina Thevenot, who created a colour image of it. 

Hubble Asteroid Hunter was created using our Zooniverse Panoptes platform by a team of researchers from the European Space Agency, and launched on International Asteroid Day (30 June 2019) with the aim of identifying serendipitous observations of asteroids in archival Hubble data. Over the almost three decades of observations, HST provided a vast wealth of images that are available in the archives. Many of these images targeting far away galaxies or clusters contain photobombing asteroids, passing in front of the intended targets (for example asteroids passing in front of Abell 370 cluster in the Hubble Frontier Fields – https://hubblesite.org/contents/media/images/2017/33/4082-Image.html?keyword=Asteroids) . Rather than being a nuisance, astronomers realised that the images can be used to better characterise the asteroids themselves and determine their orbits. 

A pipeline was set up in ESA’s discovery portal (ESA Sky – https://sky.esa.int/) that matches the asteroids’ predicted positions in both time and space from the IAU Minor Planet Center database with the European HST archival images. The predicted positions of these objects, nevertheless, have some uncertainties as the ephemerides are not always known to great precision. This is a great opportunity for citizen scientists to inspect Hubble images and mark the positions of the trails. Knowing the exact positions of the trails allows researchers to update the ephemerides of the asteroids, and better characterise their orbits. This is important, especially for Near-Earth Objects, which can be potentially hazardous for the Earth. 

So far, over 1900 citizen scientists participated in the project, providing over 300,000 classifications. The project was extended with images from the ecliptic plane to search for potentially unknown asteroids, and with other longer exposure archival images to search for possible past interstellar visitors, such as 2I/Borisov. The volunteers have the chance of exploring beautiful Hubble images of galaxies, clusters and  gravitational lenses with these new images! 

Happy asteroid hunting on www.asteroidhunter.org!