Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Deciphering the 3-D Orion Nebula-I: Expanding Shells in the Huygens
  Region   Based on imaging and spectroscopic data, we develop a 3-D model for the
Huygens Region of the Orion Nebula. Theta1OriC , the hottest star in the
Trapezium, is surrounded by a wind-blown Central Bubble that opens SW into the
Extended Orion Nebula. Outside of this feature lies a layer of ionized gas at
about 0.4 pc from Theta1OriC. Both of these features are moving rapidly away
from Theta1OriC with an expansion age for the Central Bubble of only 15,000
yrs.

15
The categories of this paper are: nucl-ex
1
The categories of this paper are: cs
8
The categories of this paper are: hep-ex
24
The categories of this paper are: dg-ga
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
9
The categories of this paper are: nlin
3
The categories of this paper are: physics
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
34
The categories of this paper are: chem-ph
28
The categories of this paper are: alg-geom
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat