* Astronomy

Members Login
Post Info TOPIC: NGC7009


L

Posts: 131433
Date:
The Saturn Nebula
Permalink  
 


NGC 7009 (also The Saturn Nebula, Struve 8, Caldwell 55 and HD 200516) is a magnitude +8.0 planetary nebula located between 3,900 and 2,400 light-years away in the constellation Aquarius.

The planetary nebula was discovered by William Herschel, using a "small 20ft" 30.48 cm (12-inch) speculum reflector at his home in Datchet, England, on September 7, 1782. This was Herschels first discovery.
The nebula as observed by William Parsons, 3rd Earl of Rosse in 1850 at Birr Castle in Ireland.

Right Ascension 21h 04m 10.877s, Declination -11° 21' 48.25"

The nebula can be spotted 1 degree west of the star Nu Aquarii. The central portion measures 25" x 17", while the outer shell extends to 41" x 35". It is a beautiful object with a high surface brightness.
Read more



__________________


L

Posts: 131433
Date:
NGC 7009
Permalink  
 


Title: Very deep spectroscopy of the bright Saturn Nebula NGC 7009 -- I. Observations and plasma diagnostics
Authors: X. Fang, X.-W. Liu

We present very deep CCD spectrum of the bright, medium-excitation planetary nebula NGC 7009, with a wavelength coverage from 3040 to 11000 A. Traditional emission line identification is carried out to identify all the emission features in the spectra, based on the available laboratory atomic transition data. Since the spectra are of medium resolution, we use multi-Gaussian line profile fitting to deblend faint blended lines, most of which are optical recombination lines (ORLs) emitted by singly ionized ions of abundant second-row elements such as C, N, O and Ne. Computer-aided emission-line identification, using the code EMILI developed by Sharpee et al., is then employed to further identify all the emission lines thus obtained. In total about 1200 emission features are identified, with the faintest ones down to fluxes 10^{-4} of H_beta. The flux errors for all emission lines, estimated from multi-Gaussian fitting, are presented. Plots of the whole optical spectrum, identified emission lines labelled, are presented along with the results of multi-Gaussian fits. Plasma diagnostics using optical forbidden line ratios are carried out. Also derived are electron temperatures and densities from the H I, He I and He II recombination spectrum.

Read more  (733kb, PDF)



__________________


L

Posts: 131433
Date:
NGC7009
Permalink  
 


Title: Proper Motions of the Ansae in the Planetary Nebula NGC 7009
Authors: Luis F. Rodriguez, Yolanda Gomez

For the planetary nebula NGC 7009, we present a comparison of two unpublished Very Large Array archive data sets taken with a time separation of 8.09 years to confirm the proper motions of its ansae observed in the optical. We determine values of 23±6 and 34±10 mas yr^{-1} for the eastern and western ansae, respectively. There is marginal evidence suggesting that the flux densities of the jets that connect the ansae with the main body of the nebula diminished in about 30% over the period between the two observations. We also set an upper limit to the expansion of the main body of the planetary nebula, setting a lower limit of ~700 pc for its distance.

Read more (304kb, PDF)

__________________
Page 1 of 1  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard