Rare supernova discovery ushers in new era for cosmology

With the help of an automated supernova-hunting pipeline and a galaxy sitting 2 bil-lion light years away from Earth that’s acting as a “magnifying glass,’‘ astronomers have captured multiple images of a Type Ia supernova—the brilliant explosion of a star—appearing in four different locations on the sky. So far this is the only Type Ia discovered that has exhibited this effect.

Read more at: https://phys.org/news/2017-04-rare-supernova-discovery-ushers-era.html#jCp

Tau.Neutrino said:

Rare supernova discovery ushers in new era for cosmology

With the help of an automated supernova-hunting pipeline and a galaxy sitting 2 bil-lion light years away from Earth that’s acting as a “magnifying glass,’‘ astronomers have captured multiple images of a Type Ia supernova—the brilliant explosion of a star—appearing in four different locations on the sky. So far this is the only Type Ia discovered that has exhibited this effect.

Read more at: https://phys.org/news/2017-04-rare-supernova-discovery-ushers-era.html#jCp

Oh nice. Very nice. Unique. Astronomers ought to be able to gather a huge amount of highly useful information from this one.

This is not the same as gravitational lensing of a quasar, because a quasar’s output is intrinsically unpredictable. But the output from a Type 1a supernova is extremely predictable.

“nearby Universe, about 1 billion light years away”

I like that definition of “near”. You may think it’s a long way to the corner shop …

I find it rather startling that Hubble was moved to look at such a faint supernova. Let’s see how it happened.

“The process of identifying transient events, like supernovae, begins every night at the Palomar Observatory in Southern California, where a wide-field camera mounted on the robotic Samuel Oschin Telescope scans the sky. 400 miles away at NERSC, machine learning algorithms running on the facility’s supercomputers sift through the data in real-time and identify transients for researchers to follow up on.

“On September 5, 2016, the pipeline identified iPTF16geu as a supernova candidate. At first glance, the event didn’t look particularly out of the ordinary.
Like most supernovae that are discovered relatively early on, this event got brighter with time. Shortly after it reached peak brightness (19th magnitude) Stockholm University Professor in Experimental Particle Astrophysics Ariel Goobar decided to take a spectrum of the object. The results confirmed that the object was indeed a Type Ia supernova, but they also showed that, surprisingly, it was located 4 billion light years away. A second spectrum taken with the OSIRIS instrument on the Keck telescope on Mauna Kea, Hawaii, showed without a doubt that the supernova was 4 billion light years away, and also revealed its host galaxy and another galaxy located about 2 billion light years away that was acting as a gravitational lens, which amplified the brightness of the supernova and caused it to appear in four different places on the sky.”

The Keck spectrum was sensitive enough to identify the four locations? That seems unlikely, perhaps it’s standard practice to take an image at the same location as the spectrum. Glad to see that Keck is still doing groundbreaking work. What’s four billion light years as a redshift (checks web) z=0.3. Not particularly far away, supernovae have been found at more than five times that distance, so delightfully surprising that there was follow-up.

“I’ve been looking for a lensed supernova for about 15 years. I looked in every possible survey, I’ve tried a variety of techniques to do this and essentially gave up, so this result came as a huge surprise,” says Goobar

I still haven’t successfully understood why the Einstein’s cross is so much more common for gravitational-lensed objects than other shapes such as the ring.