While you might think of the solar system as basically just the planets and the sun, in fact it also includes hundreds of thousands of smaller objects like asteroids, comets, meteoroids, and minor planets out beyond the orbit of Neptune called trans-Neptunian objects. Most of these objects orbit the sun (though there are occasional visitors to our solar system from elsewhere, like the famous interstellar object ‘Oumuamua), but not all of their orbits are circular. Many of them have elongated or elliptical orbits, meaning they may only come close to the inner solar system once in hundreds of years.
So if you look up into the sky and spot a faint object, it’s hard to know what it is or where it came from. To accurately track that object, multiple observations are needed to find out how it is moving, and from this you can learn about its orbit and tell if it is a new detection or an already known object. Missions like NEOWISE can observe indications of an object moving across the sky, then these are compared with data from telescopes on the ground to tell if the object is new.
“The most fun thing when I look at the data for the first time is knowing that no one has seen this before. It puts you in a unique position of doing real exploration,” said Roc Cutri, lead scientist for the NEOWISE Science Data System at Caltech’s Infrared Processing and Analysis Center.
