Awesome! A four-times lensed view of Refsdal, the first exploding star we can see through a supermassive lens.

Hubble image

The four yellow dots indicated with arrows are the one exploding star, lensed and mirrored by the gravity of the galaxy between us and that exploded star.

Apparently this is relatively common, the lensing and mirroring of distant objects by closer masses. However, this is apparently the first super nova we have observed.

Note, we are observing a star explode today. The star is 9.3 billion light years away.

One light year equals 5.87849981 × 10^12 miles. One light year distance is nearly 6 trillion miles. Thus, the light from the exploded star has travelled 54,670,048,233,000,000,000,000 miles, 54.67 x 10^21 miles, or over 54 sextillion miles. (Trillion, quadrillion, quintillion, sextillion, septillion…) Since the speed of light is constant at 186,000 miles per second, for us to observe it right now, it has to have been travelling for 293,924,990,500,000,000 seconds, which, of course, works out as about 9.3 billion years. (Thus the convenience of the light-year as a unit of distance that gives us a natural measure of how long the light took to travel that far.)

In other words, we are observing today something that happened billions of years ago.

Now, this article,, talks a little about the star and the galaxy (and the galactic cluster in the vicinity) that is lensing it, and it tries to explain simply. It does a good job.

I’m writing to point out the use of models in their work.

We see the exploding star today. We are observing it. We can measure the spectrum of the four yellow spots and determine they are, in fact, four images of the same thing, the same exploding star. There aren’t four, just one.

We need cosmological models that include real-world mathematical constructs to make sense of four images of the same thing around a galaxy roughly halfway between us and the exploding star. We need very good and precise mathematical models to be able to explain the four images positioned as we see them. We can use the mathematical models as predictive tools. These astronomers are using these tools to predict that the images will change in certain ways, given our understanding of the intervening galaxies and space, and if our models are correct, the images will change as predicted.

Probably, however, what we see will change slightly different from predicted, and the astronomers, physicists, cosmologists, and mathematicians will get busy and improve the models to make them fit what we actually observe.

Observational science.

Look at it. Figure it out. Test what you figured. Change what you figured. Do it again.

When the real world behaves as you expect all the time, every try, then your model works and you can have some confidence that you are not fooling yourself. We do this all the time when playing catch. We instinctively construct a physics-and-mathematics (calculus) based model in our head, and if our bodily-coordination is good, we throw and catch and have some fun. Mathematical models are good things.

The caution is that we must not fool ourselves, and we must keep in mind that we are the easiest to fool.

Test, check, recalculate, have others check the work, the tests, and the calculations, and do it again. Then we are observing the world and interacting effectively with it and learning.

In cosmology and astronomy we learn all the time. Lots of things change as we figure better ways to test and better ways to watch and observe. We keep looking, and there’s so much to see that we cannot help but learn and improve our models.

For me, the fascination of the article, of knowing that the lensing is going on and the event is dynamic, the fascination is watching to see how the scientists change their model of dark matter. Dark matter is scary stuff. Not because we cannot see it, but because it is so hard to figure out. It has the stench of magic about it. The more we figure it out, the more we wash away the magic, but until we can routinely model it accurately, and until we can observe it and test it, it is difficult. Science observes. Dark matter is really hard to observe. Wind is something that at first glance is hard to observe, but we know how to observe it. We model the matter and energy involved, we can compute it in detail. Then we watch what the wind does. We watch the trees sway, we watch the leaves blow, we feel the breeze on our faces and blowing through our hair. (Nice, isn’t it.)

Once we have dark matter down like wind, no problem. Until then, it is intriguing to watch and see what we have been getting wrong and how we are correcting.

Journal Reference:

Patrick L. Kelly et al. Multiple Images of a Highly Magnified Supernova Formed by an Early-Type Cluster Galaxy Lens. Submitted to arXiv, 2015 [link]

You can download the 17 page paper here:

Cite as: arXiv:1411.6009 [astro-ph.CO]
(or arXiv:1411.6009v3 [astro-ph.CO] for this version)

Space Telescope Science Institute (STScI). “Hubble sees supernova split into four images by cosmic lens.” ScienceDaily. ScienceDaily, 5 March 2015. .

Again, awesome.