A tiny object on the outskirts of the solar system discovered using an amateur telescope

Astronomers discovered an object about a kilometer in diameter in the Kuiper belt on the outskirts of the solar system. It sounds incredible, but the discovery was made with an amateur telescope of diameters of only 28 centimeters.

The achievement is described in a scientific article published in the journal Nature Astronomy by a group led by Ko Arimatsu from the National Astronomical Observatory of Japan.

Experts suggest that the main population of the Kuiper belt are objects with a diameter of one to ten kilometers. Planet germs (planetesimals) had this size before entering the phase of “explosive” growth. On the outskirts of the solar system there must be many such unborn worlds.

However, it is almost impossible to discern such an object at distances ten times greater than the distance from the Earth to the Sun. They get too little sunlight to observe the light reflected by them (the classic way that asteroids, comets and other non-luminous bodies are discovered).

Fortunately, there is an alternative way. When a similar object crosses the line connecting the observer and a star, it partially obscures the luminary, and the brightness of the latter drops. Such an “eclipse” and allows you to detect an asteroid.

However, in practice, such observations are common for bodies tens of kilometers in size, such as Ultima Thule.

In 2009, the Hubble telescope discovered an asteroid with a diameter of less than a kilometer using this method. He became the smallest known object of the Kuiper belt. As for the range of 1–10 kilometers, such asteroids eluded observers.

The news came from no waiting. The long-awaited discovery to humanity was brought not by large and fabulously expensive instruments, but by a pair of amateur instruments (albeit in the hands of professional astronomers).

A team of OASES project enthusiasts installed two 28-cm telescopes on the roof of a school in Japan. For comparison: for ground professional tools, the diameters of the lenses are calculated in meters, and they are constructed in special places with particularly clean air and lack of illumination.

With the help of such a device, the group arranged monitoring of 2000 stars. In total, the observation took 60 hours. By processing the results, astronomers discovered an “eclipse.” According to their calculations, it was caused by an object with a radius of about 1.3 kilometers.
 
“This is a real victory for small projects. Our team had less than 0.3% of the budget of large international projects. We didn’t even have enough money to build a dome protecting our second telescope! And yet we managed to make a discovery that wasn’t big projects, ”says Arimatsu.

Having calculated the chances of an event that happened, the authors calculated that for every square degree of the celestial sphere there should be about 60 thousand objects of the Kuiper belt with a radius of at least 1.2 km. This estimate is consistent with modern theories of the formation of the solar system.

Therefore, we can assume that we still have many similar discoveries ahead, although this had to wait 70 years.