On the Spectrum of the New Star in Auriga, as compared with the spectra of planetary nebula. By Eugen von Gothard.

In the new star, which appeared in February, a catastrophe took place before our eyes, which is perhaps destined to afford us a glimpse into the origin and the disappearance of celestial bodies. My spectrographic studies seem to show me the direction in which to look for the origin and the dissolution of stars.

In February I examined the spectrum of the new star several times directly by the eye, and six times by means of photography.

The spectrum consisted of many bright and several dark lines, the latter mostly corresponding with the former. My photographs show 40-43 bright lines and 12-13 dark ones.

It appeared to me, therefore, as if it consisted of two bodies, of which the one produced the emission, the other the absorption spectrum, and which had rushed against each other with enormous rapidity in the line of sight.

I will refrain on this occasion from entering into a minute description of the beautiful spectrum. The following remarks treat merely of its present aspect.

The new star rapidly decreased in brilliancy. After the middle of March I could not observe it with my modest 10-inch reflector. In the autumn, when it was again in a favourable position for observation, I observed it with a beautiful 10-inch objective prism, which my friend Dr. Nicholas von Konkoly had placed at my disposal for my spectrographic studies. The valuable prism had been ground by a very skilful amateur, Herr Fabriksdirector Dr. Max Pauly in Mühlberg.

The spectrum appeared amongst the numerous spectra of the neighbouring stars like a star of the 10th mag. It was therefore monochromatic.

I obtained a photograph of it on September 15. As I did not find it on the plate I took another on the 19th. This time six spots could be distinguished.

In the meantime I had photographed with the prism several interesting but seldom accessible objects, so that a comparison with the nebula G.C. No. 4447, 4964, and with the Wolf-Rayet stars in Cygnus, became possible. My surprise was very great to find that the spectrum of the Nova bore a great resemblance to the two first-mentioned nebulæ. Since then I have taken the photographs of several planetary nebulæ, not only with the objective prism, but also with my quartz iceland spar spectrograph, so that I could determine the wave-lengths of the spots. Each new photograph increased the probability, which may be considered as a proved fact, that the spectrum not only resembles, but that the aspect and the position of the lines show it to be identical with the spectra of the planetary nebulæ. In other words, the new star has changed into a planetary nebula.

The following table will demonstrate my assertion in the most striking manner :

The correspondence of the wave-lengths is so close that one. could not expect it to be closer, considering the uncertainty of the measurement of the diffused spots, and the shortness of the entire spectrum, the whole lengths, from 1500 to A372, being only 2'4 mm.

The resemblance between the spectra becomes most apparent and convincing when the plates are superposed and both spectra examined together side by side. Nobody could possibly distinguish one from the other.

Before entering into the details of the spectra I will note the estimated intensities:

I must now communicate the results I arrived at with the quartz spectrograph, by means of which the identification of the lines and the computation of their wave-lengths became possible. No direct estimation is practicable with the objectiveprism, since it is impossible to take with it simultaneously the photographs of the spectrum and of the comparison spectrum. But it would be quite as impossible to take with the spectroscope most of the above-mentioned nebulæ, on account of the great feebleness of their lights.

In the photograph of the Orion nebula, I. is missing, as an ordinary plate was used, and not, as for all the others, an orthochromatic one.

From these results the following final conclusions may be drawn :-

1. The spectra of the planetary nebulæ are very like each other; they only differ somewhat in the relative intensities of the lines, which, however, do not alter their typical character.

2. The lines of hydrogen play so important a part that they are represented in all the spectra by several lines.

3. Besides the hydrogen lines, two characteristic nebular lines, λ=5008 and 386 7μμ. are found in all the nebula which I have so far examined; the third line, λ=372'4, occurs frequently, but another line, λ=464–470μμ, appears but seldom.

4. The new star must, at present, be in a state which chemically and physically resembles that of the planetary nebulæ.

5. In the spectra of all planetary nebule there exists a more or less distinct continuous spectrum, which seems to form the nucleus of the nebula. The spectrum gives the impression that this nucleus is surrounded by an extensive gaseous atmosphere.

I will not draw any further conclusions at present, but will continue my studies, and shall especially endeavour, by means of long exposures, to obtain with greater certainty such details as are not sufficiently distinct as yet.

I shall pursue the history of the new star further by photographing its spectrum from time to time, and hope that I may take the liberty of giving another account of my results.

Herény Astrophysical Observatory,

1892 November 4.