«For B0355 +54, a jet points nearly at us so we detect the bright radio pulses while most of the gamma - ray emission is directed in the plane of the sky and misses the Earth,» said Kargaltsev. (sciencedaily.com)
However, measuring the movement in the plane of the sky, what is known as the proper motion, is much more difficult. (sciencedaily.com)
Those measurements, however, were not accurate enough to obtain parallax, and relied instead on tracking the star - forming region's so - called «proper motion» across the plane of the sky. (scientificamerican.com)