Quasar Q0975+561 is a remarkable extragalactic object located in the constellation Ursa Major, approximately 10 arcminutes north of the galaxy NGC 3079. It was discovered in 1979 and has since become a significant object of study in observational cosmology. With a redshift of z=1.41 the object is incredible 9 billion light-years away from us.
This quasar is gravitationally lensed, meaning that its light is bent and magnified by the gravitational field of an intervening massive object along the line of sight. As a result, Q0975+561 appears as a double image, one of the early direct observational proofs of Einstein’s General Theory of Relativity, which predicts the curvature of spacetime due to gravity.
The gravitational lens responsible for this effect is believed to be a massive elliptical galaxy or a galaxy cluster positioned between the quasar and Earth. The intense gravitational field of this lensing object bends the quasar’s light, creating the multiple images observed from Earth. Notably, the light paths differ in length, causing a time delay between the two images. Studies have determined that the image known as A precedes image B by approximately 417 days, meaning events observed in image A are seen in image B about 14 months later.
This phenomenon not only confirms the warping of spacetime but also provides astronomers with a natural cosmic magnification tool to study distant quasars and the large-scale structure of the universe.
A detail with the faintest stars
Checking SDSS for the magnitudes
The Sloan Digital Sky Survey, or SDSS, is an international collaboration of scientists gathering data from two telescopes in North and South America to build the most detailed Three-Dimensional Imagery of the Universe ever made. The SDSS has produced deep multi-color images of one third of the sky, and created spectra of more than three million astronomical objects. The survey captures images across five different wavelengths and conducts follow-up spectroscopy on selected celestial objects. Through its extensive observations, SDSS has cataloged the positions and brightness of about 470 million celestial objects, including galaxies, quasars, and stars.
For my observation, limiting magnitudes of nearly 23 mag were resolved under Bortle 4 skies. Absolutely crazy …
