Peas Through a Lens

This week’s OOTW features today’s OOTD by Budgieye.

SDSS view of SDSS J001340.21+152312.0

This yellow fuzzy galaxy is a Quasar 1.59 billion light years away from Earth in the constellation Pegasus; it’s just above to the left of the star Gamma Pegasi.

When you zoom in with the Keck observatory you’re treated to this beauty:

Credit: F. Courbin, G. Meylan, S. G. Djorgovski, et al., EPFL/ Caltech/WMKO

Now what the Keck telescope can see and the Sloan telescope can’t are the two red smudges in the blue glow of the Quasar. These smudges are in fact one Pea gravitationally lensed by the QSO sitting in front of it! This is the first ever example of a Quasar strongly lensing an object. This is where a galaxy or a cluster of galaxies are so massive that they bend space-time so much that it visibly bends light around them. So the light emitted by an object sitting behind a cluster of galaxies gets bent around the cluster, creating multiple images of one object.

So how can we tell they are multiple images of the same object?

A quote from Budieye’s OOTD:

To ensure that the two red objects on each side of the quasar is actually the same object, each object must have their spectrum taken separately.
Both blobs of red light had identical spectra, indicating that both blobs are the same object, and that the quasar is bending the light from the distant galaxy into two blobs.