5. SS 433: This is one of the strangest objects in the sky. SS433 was discovered in 1978 by Bruce Margon, an astronomer from the University of Washington. He recognized that its spectrum had strong emission lines at unusual wavelengths, and after taking repeated spectra he saw that the wavelengths of the emission lines shifted to the red and blue with a 164-day period. After a while, astronomers realized that these emission lines were the Balmer lines of hydrogen, and that the wavelength shifts were caused by a changing Doppler shift. These changing Doppler shifts could be understood if the source was squirting out twin jets of hydrogen at a speed of 0.26 times the speed of light! Moreover, the jets were precessing, as if the nozzle is moving in a conical pattern every 164 days. After carefully analyzing his observations, Margon found that the source of the jets was orbiting a massive star with a period of 13 days. Afterwards, radio astronomers and X-ray astronomers were able to obtain images of the SS433 jets.

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