Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Birth and early evolution of a planetary nebula   The final expulsion of gas by a star as it forms a planetary nebula --- the
ionized shell of gas often observed surrounding a young white dwarf --- is one
of the most poorly understood stages of stellar evolution. Such nebulae form
extremely rapidly (about 100 years for the ionization) and so the formation
process is inherently difficult to observe. Particularly puzzling is how a
spherical star can produce a highly asymmetric nebula with collimated outflows.
Here we report optical observations of the Stingray Nebula which has become an
ionized planetary nebula within the past few decades. We find that the
collimated outflows are already evident, and we have identified the nebular
structure that focuses the outflows. We have also found a companion star,
reinforcing previous suspicions that binary companions play an important role
in shaping planetary nebulae and changing the direction of successive outflows.

28
The categories of this paper are: alg-geom
8
The categories of this paper are: hep-ex
20
The categories of this paper are: acc-phys
24
The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
23
The categories of this paper are: solv-int
22
The categories of this paper are: chao-dyn
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
26
The categories of this paper are: bayes-an
31
The categories of this paper are: ao-sci
27
The categories of this paper are: comp-gas
13
The categories of this paper are: quant-ph