Rare supernova discovery ushers in new era for cosmology

April 20, 2017, Lawrence Berkeley National Laboratory
This composite image shows the gravitationally lensed type Ia supernova iPTF16geu, as seen with different telescopes. The background image shows a wide-field view of the night sky as seen with the Palomar Observatory located on Palomar Mountain, California. Far Left Image: Captured by the Sloan Digital Sky Survey, this optical light observation shows the lens galaxy and its surrounding environment in the sky. Center Left Image: Captured by the Hubble Space Telescope, this is a 20x zoom infrared image of the lens galaxy. Center Right Image: Captured by the Hubble Space Telescope, this 5x optical light zoom reveals the four gravitationally lensed images of iPTF16geu. Far Right Image: Captured by the Keck Telescope, this infrared observation features the four gravitationally lensed images of iPTF16geu and the gravitational "arc" of its host galaxy. Credit: Joel Johansson, Stockholm University

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.

This phenomenon called 'gravitational lensing' is an effect of Einstein's Theory of Relativity—mass bends light. This means that the gravitational field of a massive object—like a galaxy—can bend light rays that pass nearby and refocus them somewhere else, causing background objects to appear brighter and sometimes in multiple locations. Astrophysicists believe that if they can find more of these magni-fied Type Ia's, they may be able to measure the rate of the Universe's expansion to unprecedented accuracy and shed some light on the distribution of matter in the cosmos.

Fortunately, by taking a closer look at the properties of this rare event, two Law-rence Berkeley National Laboratory (Berkeley Lab) researchers have come up with a method—a pipeline— for identifying more of these so-called "strongly lensed Type Ia supernovae" in existing and future wide-field surveys. A paper describing their approach was recently published in the Astrophysical Journal Letters. Mean-while, a paper detailing the discovery and observations of the 4 billion year old Type Ia , iPTF16geu, was published in Science on April 21.

"It is extremely difficult to find a gravitationally lensed supernova, let alone a lensed Type Ia. Statistically, we suspect that there may be approximately one of these in every 50,000 supernovae that we identify," says Peter Nugent, an astrophysicist in Berkeley Lab's Computational Research Division (CRD) and an author on both pa-pers. "But since the discovery of iPTF16geu, we now have some thoughts on how to improve our pipeline to identify more of these events."

The light from the supernova iPTF16geu and of its host galaxy is warped and amplified by the curvature of space mass of a foreground galaxy. In the case of the point-like supernova, the light is split into four images. These have been resolved with the Hubble SpaceTelescope. Credit: Original image by ALMA (ESO/NRAO/NAOJ), L. Calçada (ESO), Y. Hezaveh et al, edited and modified by Joel Johansson

Cosmic Surprise Sheds New Light on Cosmology

For many years, the transient nature of supernovae made them extremely difficult to detect. Thirty years ago, the discovery rate was about two per month. But thanks to the Intermediate Palomar Transient Factory (iPTF), a new survey with an innova-tive pipeline, these events are being detected daily, some within hours of when their initial explosions appear.

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. As soon as observa-tions are taken, the data travel more than 400 miles to the Department of Energy's (DOE's) National Energy Research Scientific Computing Center (NERSC), which is located at Berkeley Lab. At NERSC, machine learning algorithms running on the fa-cility'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. Nugent notes that many astronomers thought it was just a typical Type Ia supernova sitting about 1 billion light years away from Earth.

Like most supernovae that are discovered relatively early on, this event got brighter with time. Shortly after it reached peak brightness (19th magnitude) Stockholm Uni-versity Professor in Experimental Particle Astrophysics Ariel Goobar decided to take a spectrum—or detailed light study—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 in-strument 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 gravita-tional lens, which amplified the brightness of the supernova and caused it to appear in four different places on the sky.

This animation shows the phenomenon of strong gravitational lensing. This effect caused the supernova iPTF16geu to appear 50 times brighter than under normal circumstances and to be visible on the sky four times. Credit: Credit:ESA/Hubble, L. Calçada

"I've been looking for a lensed supernova for about 15 years. I looked in every pos-sible 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, who is lead author of the Science paper. "One of the reasons I'm interested in studying gravitational lensing is that it allows you to measure the structure of matter—both visible and dark matter—at scales that are very hard to get."

According to Goobar, the survey at Palomar was set up to look at objects in the nearby Universe, about 1 billion light years away. But finding a distant Type Ia su-pernova in this survey allowed researchers to follow up with even more powerful telescopes that resolved small-scale structures in the supernova host galaxy, as well as the lens galaxy that is magnifying it.

"There are billions of galaxies in the observable universe and it takes a tremendous effort to look in a very small patch of the sky to find these kind of events. It would be impossible to find an event like this without a magnified supernova directing you where to look," says Goobar. "We got very lucky with this discovery because we can see the small scale structures in these galaxies, but we won't know how lucky we are until we find more of these events and confirm that what we are seeing isn't an anomaly."

Another benefit of finding more of these events is that they can be used as tools to precisely measure the expansion rate of the Universe. One of the keys to this is gravitational lensing. When a strong gravitational lens produces multiple images of a background object, each image's light travels a slightly different path around the lens on its way to Earth. The paths have different lengths, so light from each image takes a different amount of time to arrive at Earth.

"If you measure the arrival times of the different images, that turns out to be a good way to measure the expansion rate of the Universe," says Goobar. "When people measure the expansion rate of the Universe now locally using supernovae or Cepheid stars they get a different number from those looking at early universe ob-servations and the cosmic microwave background. There is tension out there and it would be neat if we could contribute to resolving that quest."

This is an image of the gravitationally lensed iPTF16geu Type Ia supernova taken in near-infrared with the W.M. Keck Observatory. The lensing galaxy visible in the center has distorted and bent the light from iPTF16geu, which is behind it, to produce multiple images of the same supernova (seen around the central galaxy). The position, size and brightness of these images help astronomers infer the properties of the lensing galaxy. Credit: W. M. Keck Observatory

New Methods Sniff Out Lensed Supernovae

According to Danny Goldstein, a UC Berkeley astronomy graduate student and an author of the Astrophysical Journal letter, there have only been a few gravitationally lensed supernovae of any type ever discovered, including iPTF16geu, and they've all been discovered by chance.

"By figuring out how to systematically find strongly lensed Type Ia supernovae like iPTF16geu, we hope to pave the way for large-scale lensed supernova searches, which will unlock the potential of these objects as tools for precision cosmology," says Goldstein, who worked with Nugent to devise a method of for finding them in existing and upcoming wide-field surveys.

The key idea of their technique is to use the fact that Type Ia supernovae are "stan-dard candles"—objects with the same intrinsic brightness—to identify ones that are magnified by lensing. They suggest starting with supernovae that appear to go off in red galaxies that have stopped forming stars. These galaxies only host Type Ia su-pernovae and make up the bulk of gravitational lenses. If a supernova candidate that appears to be hosted in such a galaxy is brighter than the "standard" brightness of a Type Ia supernova, Goldstein and Nugent argue that there is a strong chance the su-pernova does not actually reside in the galaxy, but is instead a background super-nova lensed by the apparent host.

"One of the innovations of this method is that we don't have to detect multiple im-ages to infer that a supernova is lensed," says Goldstein. "This is a huge advantage that should enable us to find more of these events than previously thought possi-ble."

Using this method, Nugent and Goldstein predict that the upcoming Large Synoptic Survey Telescope should be able to detect about 500 strongly lensed Type Ia super-novae over the course of 10 years—about 10 times more than previous estimates. Meanwhile, the Zwicky Transient Facility, which begins taking data in August 2017 at Palomar, should find approximately 10 of these events in a three-year search. On-going studies show that each lensed Type Ia supernova image has the potential to make a four percent, or better, measurement of the of the universe. If realized, this could add a very powerful tool to probe and measure the cosmological parameters.

"We are just now getting to the point where our transient surveys are big enough, our pipelines are efficient enough, and our external data sets are rich enough that we can weave through the data and get at these rare events," adds Goldstein. "It's an exciting time to be working in this field."

iPTF is a scientific collaboration between Caltech; Los Alamos National Laboratory; the University of Wisconsin, Milwaukee; the Oskar Klein Centre in Sweden; the Weizmann Institute of Science in Israel; the TANGO Program of the University Sys-tem of Taiwan; and the Kavli Institute for the Physics and Mathematics of the Uni-verse in Japan. NERSC is a DOE Office of Science User Facility.

Explore further: Cosmic illusion revealed: Gravitational lens magnifies supernova

More information: "iPTF16 geu: A multiply imaged, gravitationally lensed type Ia supernova," Science (2017). science.sciencemag.org/cgi/doi … 1126/science.aal2729

Daniel A. Goldstein et al. HOW TO FIND GRAVITATIONALLY LENSED TYPE Ia SUPERNOVAE, The Astrophysical Journal (2016). DOI: 10.3847/2041-8213/834/1/L5

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Chris_Reeve
Apr 20, 2017
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Chris_Reeve
Apr 20, 2017
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Chris_Reeve
Apr 20, 2017
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Chris_Reeve
Apr 20, 2017
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Chris_Reeve
Apr 20, 2017
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Chris_Reeve
Apr 20, 2017
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IMP-9
4.7 / 5 (12) Apr 20, 2017
What the spectrum had confirmed was that this indeed was a low density, excited hydrogen filament connecting the two objects of vastly different redshift.


Which is funny because the authors who actually did the work Arp is talking credit for there don't agree. Yee & De Robertis 1991 conclude that a clump of narrow Lya seen near the plane of the lensing galaxy is likely a star forming region in the lens QSO host of a satellite galaxy. This is just one example of how Arp systematically ignored other conclusions when presenting his evidence. After all there is no evidence of a physical connection between the narrow component and the lensing galaxy, if it were a connecting filament perhaps you would expect it to span the velocity space between the quasar and the lensing galaxy, but no. It's offset from the broad component by just 255 km/s while the lensing galaxy is offset by over 200,000 km/s. The spectroscopy also doesn't indicate it's a filament at all. Please stop spamming.
cantdrive85
1 / 5 (8) Apr 20, 2017
gimp-0 must be a cal-tech alum.
Chris_Reeve
Apr 20, 2017
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Chris_Reeve
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Chris_Reeve
Apr 21, 2017
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barakn
4.6 / 5 (10) Apr 21, 2017
The point was, of course, that a line between quasar A and B passed directly between the nucleus of the galaxy and quasar D. On the face of it high redshift gas was indicated near the nucleus of the low redshift galaxy.
Gravitational lensing theory had established that elliptical distributions of mass could lead to quadrupolar images of quasars with a 5th image, dim and non-magnified, near the center, often lost in the glare of the lensing mass. See for example. Elliptic Mass Distributions versus Elliptic Potentials in Gravitational Lenses. Kassiola, A. & Kovner, I : Astrophysical Journal v.417, p.450. http://adsabs.har...17..450K That was published in 1993, 5 years before Arp's book, so Arp was merely observing and confirming something, the 5th image, that had been predicted (not post-dicted) by Gravitational lensing theory.
IMP-9
4.6 / 5 (11) Apr 21, 2017
if you extrapolate the luminosity required for an elliptical to have this M/L ratio it comes out MB = -25 mag.


What an interesting claim. However without any way to scrutinise the calculation this no one should take him at his word.

On the topic of the Einstein Cross you can measure the delay between the quasar images. Quasars fluctuate in brightness and gravitational lensing says that the images will have slight time delays with respect to each other due to the Einstein and Shaprio delays. For Q2237+030, the delays are on the order of 3, 6 and 35 hours [Vakulik 2006]. Yes, hours. And yet if these were separate objects near the lensed galaxy they would be separated by about 4800 light years, and yet they are in almost perfect synchronicity from our unique viewing angle. So either this galaxy is the size of a solar system or it is a gravitational lens.
IMP-9
5 / 5 (11) Apr 21, 2017
M.B. Bell and D. McDiarmid of the National Research Council of Canada published an analysis of 46,400 (that's right -- forty six thousand!) quasar redshifts from the Sloan Digital Sky Survey.


Which Bell himself later retracted.

"It is shown here that a periodicity of Delta(z)~0.6 is imprinted on the redshift-number distribution by this selection effect. Because this effect cannot be rigorously corrected for, astronomers need to be aware of it in any investigation that uses the SDSS N(z) distribution. Its presence also means that the SDSS quasar data cannot be used either to confirm or to rule out the Delta(z)~0.6 redshift period reported previously in other, unrelated quasar data."

Bell & Comeau 2009, arxiv:0911.5700


Hartnett (another periodicity nut) also reached the same conclusion in 2009. Both you and Ratcliffe are guilty of extreme cherrypicking.
HannesAlfven
1.4 / 5 (11) Apr 21, 2017
What I think many of you guys do not realize is that when somebody publishes one of these papers, it is oftentimes their last. You guys keep on treating everything which is going on as though there is no pressure being applied. Actually, in case after case, papers are rejected -- sometimes without even sending them off for review, on the basis of the claim alone (!) -- and the authors have to shop them around.

There are also examples of younger astronomers not fully understanding the implications, and suddenly finding themselves unable to publish anything at all.

The number of associations between objects of differing redshifts that has been published over the past few decades is in the hundreds by now.

Think about your approach to this controversy: You're refusing to learn it, and jumping at the first straw you can grab that confirms your case.

Instead of learning everything you can about the controversy, you're here convincing others to copy your lazy approach.
HannesAlfven
1.4 / 5 (11) Apr 21, 2017
This really comes down to your false narratives about what you imagine a big change in theory to look like. You have this false notion that it would be an orderly affair.

I am not your enemy. That's not how you will remember me.

People need to grow up, and realize that politics happens in science too.

Take the time to learn the arguments on BOTH sides. If you are too short on time to read Quasars, Redshifts and Controversies or Seeing Red, then spend an hour watching this Arp lecture here:

https://www.youtu...BfKPAGNM

To fully appreciate the argument that has been put forward, you need learn all of the fronts on which it is happening so that as new press releases come out, you can evaluate for yourself whether or not Arp is vindicated -- and whether or not you believe the claims being made in the press release.

There are no shortcuts to this process of forming your own opinion.
HannesAlfven
1.5 / 5 (8) Apr 21, 2017
And, btw, all of these people who take the time to announce on phys.org that they are filtering out arguments which they don't agree with, realize that those sorts of behaviors will of course happen in the event of ANY big upheaval in the space sciences - legitimate or not.

These people who do this will be the last to know of any big change happening, and they will of course fall in line in the event that the experts publicly change their positions.

Their announcement is that they are thought followers -- not thought leaders who have the courage to question their own beliefs in the light of ongoing controversies.

It means so little.
barakn
4.6 / 5 (9) Apr 21, 2017
And, btw, all of these people who take the time to announce on phys.org that they are filtering out arguments which they don't agree with, realize that those sorts of behaviors will of course happen in the event of ANY big upheaval in the space sciences - legitimate or not.
In your case, they are ignoring a blowhard who leaves dozens of posts worth of gish-gallop/verbal diarrhea on a single article and who responds to challenges to his statement mainly going off on tangents. In short, they're not filtering out arguments, they are filtering out an asshole.
HannesAlfven
1 / 5 (6) Apr 21, 2017
"Any discussion of something new requires dialogue between hypothesis and criticism. If animated and vigorous this is controversy. It is supposed to uncover what is wrong and illuminate what is correct, or possibly correct. The more energetically this process goes on, the more progress can be made, particularly if further testing is stimulated. Controversy can be extremely valuable. But some people on the other side of the present controversy have denied that there was a legitimate controversy. They insist that the issues were all resolved long ago, that no valid evidence of new effects exists, and that further discussion or testing is a waste of time."

- Halton Arp in Quasars, Redshifts and Controversies
HannesAlfven
1 / 5 (5) Apr 21, 2017
The Golem: What You Should Know About Science
Collins / Pinch

"citizens as citizens need understand only controversial science. One reviewer argues: 'it is quite easy to think of political decisions with a scientific side to them where the science is noncontroversial' and offers as an example the effect on medical institutions of the development of a predictive test for Huntington's disease. But if the science is non-controversial, why do those running the medical institutions need to understand the deep nature of the science that gave rise to the results? If the test is uncontroversially valid they can make their decisions without understanding how agreement about the test was reached. Thus ... we stand by our claim that 'For citizens who want to take part in the democratic processes of a technological society, all the science they need to know about is controversial.'"
SlartiBartfast
4.3 / 5 (6) Apr 21, 2017
Seeing Red: Redshifts, Cosmology and Academic Science
Halton Arp


This has already been addressed...see for example: https://youtu.be/...P3Y?t=67
HannesAlfven
1 / 5 (6) Apr 21, 2017
From yesterday ...

https://www.times...y-answer

Nobel laureates condemn 'unimaginative' research funding models
Peer review process punishes academics who 'challenge the dogma' of their field, scientists claim

April 20, 2017

"Research funding bodies do not like researchers who 'challenge the dogma' of their field, and hence give the impression that 'innovation is not valued', a Nobel laureate has warned ..."
HannesAlfven
1.5 / 5 (8) Apr 21, 2017
A short list of vindications for Arp:

(1) Alignment of quasar minor axes

(2) Numerous apparent interactions of objects of wildly different redshifts

(3) Numerous instances where high-redshift quasars appear aligned with the axes of low-redshift "foreground" galaxies

(4) Intervening galaxies are 4 times more prevalent along lines of sight to GRB's than quasars

(5) Quasars seemingly observed in front of foreground galaxies

(6) A quasar that exhibits 10x superluminal motions at inferred distance

(7) A quasar group so large that it spans 5% of the known universe at inferred distance

(8) No observation of time dilation in quasar variations

(9) Quasars have been shown to exhibit proper motion (!), which should not be possible at inferred distances

(10) Quasar clustering (not expected from Big Bang theory)
SlartiBartfast
4.5 / 5 (8) Apr 21, 2017
A short list of vindications for Arp:


It's all a conspiracehhh to hide the troof!
HannesAlfven
1 / 5 (7) Apr 21, 2017
No, it's called saving the theory. You already know the game. You're playing it.
Chris_Reeve
Apr 22, 2017
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