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Deja vu supernova refused, or back to the future
To make the lens of the traditional telescope, a glass lens or concave mirror can be necessary that can reject and focus the light. But is it necessary to make a telescope from some material? No, if you use the refractive properties of gravity. Gravity is also capable of bending light rays, so it is not surprising that massive objects show themselves as unusual lenses that deflect, and sometimes focusing the radiation of more distant sources. There are already many examples of how a relatively close galaxy (or accumulation of galaxies) so enhances the radiation of a much more distant galaxy that it becomes available for observation by an object.
The gravitational lens in this case acts as a kind of prefix to the earthly telescope. True, nature did not care about ensuring the correct device of this lens, so the images “enlarged” it are often very distorted or even break up into several separate images. Famous examples of such propagated images are the quasars of the Cross of Einstein and a leaf of clover.
Gravitational lenses not only allows us to observe distant objects that would be too dull for modern telescopes without it, but also helps to independently determine the cosmological parameters. Analyzing lensized images, you can also learn more about the lens itself, for example, find out how the substance is distributed in it.
In 1964, the Norwegian Astrophysicist Sur Refsdal published a short job in which he predicted that the observation of lensized supernovae is a particularly convenient tool for solving such problems. The light in different images of the lensed object goes to the observer in different ways that have different lengths. Accordingly, if something happened in the facility, for example, an outbreak of supernova occurred, in different images we will see this event at different times.
The refsal in his work demonstrated how to determine the mass of the lens and the constant Hubble by the difference in the time of registration of the same event in different images. In principle, for this purpose, you can use not only supernovae, but also any other objects with variable shine, such as quasars. But to determine the delay time by shine curves (that is, on the dependence of the radiation flow on time) of different lensed images of one quasar, rather long observations are required - this is necessary to reliably compare the brilliance curves with each other. It is much more convenient to work with one -time brightness amplifiers, as with supernova flashes.
In March 2015, Patrick Kelly with the co-authors said in the journal Science that in November 2014 they managed to open the first lensed supernovae using the Khabble space telescope. The star flared up in a spiral galaxy with a red shift of 1.49.
On the way to the earthly observer, its light passes near the Elliptic Galaxy from the Macs J1149.6+2223 cluster at a red displacement of 0.54 and experiences gravitational lenses on it. As a result, we see more than one image of supernova, but four (artlessly designated S1, S2, S3 and S4), almost symmetrically arranged around the Elliptical-Linze Galaxy. Since this is the first case of detecting a configuration, predicted by the reference, the authors of the article in Science proposed to name the supernatal name. Then the most interesting begins: the image of the parent galaxy of the supernova refsdal is led not only to a specific elliptic galaxy, but to all the accumulation of Macs J1149.6+2223.
And if the elliptical galaxy builds several images of supernova in one image of the parental galaxy, then the accumulation as a whole multiplies the images of the already parental galaxy. Supernova was visible only in one of them (it is designated as 1.1). This means that the authors decided, in the rest of the images, supernova either has already faded or flashed yet.
Since the release of the article by Kelly with the co -authors, several works have been published, the authors of which tried to reproduce the distribution of mass in the cluster of the Macs J1149.6+2223 according to the observations of the lensized supernova. This is a very difficult task, so the conclusions of different works were quite significantly different from each other. In particular, everyone agreed that in four images of a supernova, a temporary delay is several days, but the specific values of the delay and even the “sequence” of the S1 - S4 images in different models were different.
Having analyzed other images of the parent galaxy (designated 1.2 and 1.3), the authors of all work agreed that in image 1.3 the outbreak appeared for a long time - according to various estimates, from 9 to 17 years ago. Moreover, she was too dull so that she could be found in archival pictures. Another thing is image 1.2. In it, all the presented models predicted an outbreak of supernova in the very near future (and some of the predicted dates have already passed).
The latest grades [1–2], based on a detailed study of the Macs J1149.6+2223 accumulation structure using VLT telescopes, predicted the peak of the next outbreak in March - June 2016, and the beginning of brightness growth was completely at the end of 2015.
And the expectations were justified! Since the end of October last year, the Hubble Telescope from time to time looked in the direction of image 1.2, and the observations carried out on December 11, 2015 showed that the expected star appeared in it! She arose exactly where she was supposed, although she turned out to be slightly dull than predicted. It is interesting to note the highest speed of preparation of the article: it was posted in ARXIV four days after observation [3].
Four original images did not remain forgotten. All year, the Hubble telescope followed them, which allowed them to build crooked shine for them, significantly clarifying the values of the delay time. The first (as all previous models predicted) is the image S1. It is followed by images S3 late at about one or two days and S2 late for 4-7 days. Later, with a delay of more than three weeks, the S4 image is manifested, the most dim of all [4].
The possibility of predicting the outbreak of supernova long before her real beginning attracted significant attention as a “classical” scientific prediction that has come true, and not in heavenly mechanics, where you will not surprise anyone with accurate predictions, but in the much less studied area. Observations of Supernova Refsdal, in fact, indicate that we reach a new level of predictive accuracy in such a difficult problem as gravitational lenses.
Sur Refsdal ( Sjur Refsdal ) - Norwegian astrophysicist. Born in Oslo on December 30, 1935 (in 2015 he would have turned 80 years old). From 1967 to 1970 he held the position of the adj-professor at the University of Nepobraska (USA). There he met Alfred Weigert from the Hamburg Observatory (Germany), which began their fruitful cooperation in the evolution of stars, which lasted until the 1980s. In 1970, the refsdal received Ph.D. At the Institute of Theoretical Astrophysics of the University of Oslo. In the same year, he became a professor at the Hamburg Observatory and remained in this position until retirement in 2001. After that, he returned to his hometown, where he took the position of Honored Professor University Oslo.
From 1964 to 1970, the Refsdal published six articles, in which he largely laid the foundations of a very significant area of astrophysics related to the study of gravitational lenses. The time written by him was far ahead of time, and then his articles were quoted very little. Only after the opening of the first gravitational lens in 1979, the articles of the Refsdal attracted the attention of colleagues. Already in 1964, he showed how lenslation can serve as an instrument for measuring the speed of expansion of the Universe (constant habbla) and a mass of galaxies. This method was named the Refsdal method.
In the mid-1960s, along with a group of colleagues, Refsdal conducted several studies on the development of cosmological models, which also became pioneer. Since the late 1960s, Refsdal took up models of the internal structure of stars and their evolution. His articles about the late stages of the evolution of stars are widely quoted. In 1979, his graduate student Kyongae Chang published a pioneering work on the effect of microlysising in Nature , in which individual stars and even planets play the role of a gravitational lens. This effect can be used to solve a wide variety of tasks: from the opening of extra-headed planets to the learning of the detailed structure of the quasars.
Sur Refsdal was a member of the Norwegian Academy of Sciences and Literature. In 2001, for outstanding research, he was awarded the Nansen Prize, and in February 2005 he was awarded the Norwegian royal medal "For Merit". Refsal died after a long illness on January 29, 2009. He had two adult sons, Thomas and Gunnar Refsdals.
Based on the materials of Wikipedia, the Hamburg Observatory [5] and the Institute of Astrophysics in Oslo [6].
Photo from the site www.mn.uio.no
1. Http://arxiv.org/abs/1510.05750
2. Http://arxiv.org/abs/1511.04093
3. Http://arxiv.org/abs/1512.04654
4. Http://arxiv.org/abs/1512.05734
5. Www.hs.uni-hamburg.de/oef/stw/sjur_refsdal.html
6. Www.mn.uio.no/astro/forskning/aktuelt/aktuelle-saker/astronytt/2009/02/2009-02-02.html