NGC_1333
NGC 1333
Reflection nebula in the constellation Perseus
NGC 1333 is a reflection nebula located in the northern constellation Perseus, positioned next to the southern constellation border with Taurus and Aries.[3] It was first discovered by German astronomer Eduard Schönfeld in 1855.[4] The nebula is visible as a hazy patch in a small telescope, while a larger aperture will show a pair of dark nebulae designated Barnard 1 and Barnard 2.[5] It is associated with a dark cloud L1450 (Barnard 205). Estimates of the distance to this nebula range from 980–1,140 ly (300–350 pc).[4]
This nebula is in the western part[4] of the Perseus molecular cloud and is a young region of very active star formation,[6] being one of the best-studied objects of its type.[4] It contains a fairly typical hierarchy of star clusters that are still embedded in the molecular cloud in which they formed,[7] which are split into two main sub-groups to the north and south. Most of the infrared emission is happening in the southern part of the nebula. A significant portion of the stars seen in the infrared are in the pre-main sequence stage of their evolution.[6]
The nebula region has a combined mass of approximately 450 M☉,[4] while the cluster contains around 150 stars with a median age of a million years and a combined mass of 100 M☉. The average star formation rate is 1×10−4 M☉ yr–1.[4] Within the nebula are 20 young stellar objects producing outflows, including Herbig–Haro objects, and a total of 95 X-ray sources that are associated with known members of embedded star clusters.[6] In 2011 researchers reported finding 30 to 40 brown dwarf objects in the cloud and in the Rho Ophiuchi cloud complex.[8]
15 objects with a spectral type of M9 or later were discovered in NGC 1333. This spectral type corresponds to a mass of a planetar-mass object (PMO) at the age of NGC 1333. About 42% of the PMO are surrounded by a circumstellar disk, but only one out of six objects with a spectral type of L0 (about 10 MJ) or later has a disk. Scholz et al. argues that this indicates that very low mass PMOs form like planets (aka ejected planets) and not like stars (also called sub-brown dwarfs).[9] Parker & Alves de Oliveira on the other hand argue that the distribution of PMOs in NGC 1333 follows N-body simulations of objects that form like stars and that none of the PMOs has a peculiar motion, which is predicted for ejected planets. They also note that ejected planets are hiding in this and star-forming regions.[10]
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