Scientific NewsThe Illustrated London News, vol. 47, no. 1340, p. 415.
October 28, 1865
...Mr. Jacob Ennis has transmitted to the Academy of Sciences at Philadelphia the continuation of his observations on the colours of stars and their changes of colour at different times. For instance, within the last few years the colour of Sirius has changed from red to white, violet, full green, yellowish green, and bluish green; and that of Arcturus has varied from red to yellow and orange. Mr. Ennis is not inclined to attribute these changes of colour to the influence of the earth's atmosphere, to the optical instruments employed, or to peculiarities of vision in the observer. He selected as test-stars Vega and Capella, stars of the first magnitude, the former green and the latter blue, but failed to observe in them the action of the atmospheric medium upon their colour, as mentioned by Humboldt. Mr. Ennis suggests the recording of the colours of all the stars as frequently as possible, as they appear to the aided and unaided vision, due attention being paid to the state of the atmosphere and the influence of the sun and moon.