Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Amateur telescopes discover a kilometre-sized Kuiper belt object from
  stellar occultation   Kuiper belt objects (KBOs) are thought to be the remnant of the early solar
system, and their size distribution provides an opportunity to explore the
formation and evolution of the outer solar system. In particular, the size
distribution of kilometre-sized (radius = 1-10 km) KBO represents a signature
of initial planetesimal sizes when planets form. These kilometre-sized KBOs are
extremely faint, and it is impossible to detect them directly. Instead,
monitoring of stellar occultation events is one possible way to discover these
small KBOs. Hitherto, however, there has been no observational evidence for the
occultation events by KBOs with radii of 1-10 km. Here we report the first
detection of a single occultation event candidate by a KBO with a radius of
$\sim$1.3 km, which is simultaneously provided by two low-cost small telescopes
coupled with commercial CMOS cameras. From this detection, we conclude that a
surface number density of KBOs with radii exceeding $\sim 1.2$ km is $\sim 6
\times 10^5 \ {\rm deg^{-2}}$. This surface number density favours a
theoretical size distribution model with an excess signature at a radius of 1-2
km. If this is a true detection, this implies that planetesimals before their
runaway growth phase grow into kilometre-sized objects in the primordial outer
solar system and remain as a major population of the present-day Kuiper belt.

25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
14
The categories of this paper are: math-ph
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
10
The categories of this paper are: q-bio
23
The categories of this paper are: solv-int
31
The categories of this paper are: ao-sci
13
The categories of this paper are: quant-ph