Supernova Requiem: Reruns From a Gravity Lens

Nothing in this universe lasts forever, including stars.

Massive stars live fast and die young: exploding as supernovae.

One of these, AT2016jka, nicknamed “Requiem,” was first spotted in 2016. It showed up again in 2019.

Scientists figure they’ll get another look in 2037, give or take a few years

But the supernova only exploded once. We’re getting reruns of the event, thanks to gravitational lensing. I’ll be taking about stars, including supernovae, gravitational lensing, and whatever else comes to mind.

Stars and the Cosmos

Names and Designations

Adriaen van de Venne's illustration of a 'Dutch telescope' in Johan de Brune's 'Emblemata of zinne-werck.' (1624)Astronomers use designations like AT2016jka and MRG-M0138 for reasons I’ll discuss in “A Star by Any Other Name.”

“…Any Other Name” is currently on my back burner. The current pandemic distracted me, so I’ve got several works-in-progress. And that’s another topic.

Now, about stars, names and alphanumeric gibberish. Basically, we can see maybe 10,000 stars. That’s under ideal conditions. And, since folks occasionally discuss stars, they need ways to let other astronomers know which one they’re talking about.

We’ve named the brighter ones. Several times. Sirius, for example, has been called Aschere, Canicula, Al Shira, Mrgavyadha and Lubdhaka.

Now multiply the hassle of deciding whether everyone should call it Aschere, Al Shira or Lubdhaka by 10,000.1

Bottom line? Designations like AT2016jka make discussing stars easier. And slightly less likely to trigger arguments over which nation’s, culture’s, or language’s name is the “right” one. Even so, astronomers still use nicknames like “requiem.”

Common Origin, Different Results

NASA's 'Stellar Evolution' infographic. (Posted July 9, 2012, image created October 13, 2009)
(From NASA, used w/o permission.)
(Stellar evolution, from brown dwarfs to blue supergiants.)

All stars are not created equal, although they all begin the same way.

The star we call the Sun, for example, began as part of a stellar nursery: a molecular cloud that started collapsing and forming stars.

Our Sun and all its stellar siblings have been on their own for 4,600,000,000 years now. Astronomers think maybe HD 162826 and HD 186302 come from the same cloud, but that’s debatable: and debated.

At any rate, our sun is still turning hydrogen into helium and energy; and will continue doing so for billions of years.

Then, when it runs short on hydrogen, it will pulse a few times, balloon outward until its surface is about where Earth’s orbit is now, and then collapse.

Arcturus is a solar-mass star that’s at this stage in its life.

Six billion years from now, our star will be a white dwarf.

A star with considerably less mass than ours won’t become nearly as hot or bright: but will last a whole lot longer.2


NASA Space Place's illustration: 'What holds stars together?' (2017)The most massive stars become blue supergiants, burn through their hydrogen in a few million years and then collapse: compressing and heating their core to a point where heavier elements fuse, releasing energy and a whacking great quantity of neutrinos.

Stars like Betelgeuse aren’t quite as massive, but will eventually explode in about the same way.

I gather that a fair number of scientists expect Antares and Betelgeuse to become a supernovae soon.

Soon on a cosmic scale, that is: maybe 10,000 years from now for Antares and 100,000 years for Betelgeuse. Roughly. We’d have to know a great deal more about those stars and how exactly how supernovae work to get more exact forecasts.

Scientists have pegged Antares, Betelgeuse and four other nearby stars as supernovae that haven’t exploded yet. Nearby, again, on a cosmic scale.

The closest, IK Pegasi, is about 154 light-years out, in the general direction of Rotanev: a star almost nobody has heard of.

IK Pegasi isn’t a super-massive star. It’s two stars, one of them a white dwarf, and that brings me to supernovae types I, II, III, IV, and V. Light from each type looks different, depending on which parts of the spectrum are brightest and which elements are there.

Very massive stars become supernovae, but not all supernovae start as supermassive stars.

For example, if a mid-size star that’s running out of hydrogen balloons out far enough to start leaking onto a white dwarf companion, the white dwarf may get overloaded. Then it will collapse, triggering carbon fusion, which sets off fusion of heavier elements.

As with so much else in this universe, it’s complicated. And it’s only in the last century that scientists realized that supernovae weren’t the same as novae, and started figuring out how they work.3

Light and Gravity

Krishnavedala's diagram: optical geometry of a gravitational lens. (July 16, 2012)
(From Krishnavedala, via Wikimedia Commons, used w/o permission.)
(How gravitational lensing works: massive object “b” bends light, forming two images.)

Light from the Requiem supernova reached Earth in 2016, and again in 2019. We’re expecting another Requiem rerun in 2037, give or take a few years.

If light always travels at the same speed, then how come we’re getting Requiem reruns?

Short answer, the supernova’s light has been taking different paths on its way here, because a very massive galaxy cluster is in the way.

Einstein’s general theory of relativity said that gravity fields should bend light. So does classical physics, but only about half as much.

All that was theoretical until 1979, when scientists said Twin Quasar SBS 0957+561 was actually two images of the same quasar: and backed the claim up with data and analysis.4

Supernova Requiem: More Data, Greater Precision

(From Joseph DePasquale (STScI), via NASA, used w/o permission.)
(“Requiem” supernova images: 2016 and 2019.
(Near-infrared images from Hubble’s Wide Field Camera.))

Rerun of Supernova Blast Expected to Appear in 2037
Claire Andreoli, Goddard Space Flight Center, NASA (September 13, 2021)

“…The light that Hubble captured from the cluster, MACS J0138.0-2155, took about four billion years to reach Earth. The light from Supernova Requiem needed an estimated 10 billion years for its journey, based on the distance of its host galaxy….
“…The lensed supernova images were discovered in 2019 by Gabe Brammer…. Brammer spotted the mirrored supernova images while analyzing distant galaxies magnified by massive foreground galaxy clusters as part of an ongoing Hubble program called REsolved QUIEscent Magnified Galaxies (REQUIEM).
“He was comparing new REQUIEM data from 2019 with archival images taken in 2016 from a different Hubble science program. A tiny red object in the 2016 data caught his eye, which he initially thought was a far-flung galaxy. But it had disappeared in the 2019 images….
“…This time-delay method is valuable because it’s a more direct way of measuring the universe’s expansion rate, Rodney explained. ‘These long time delays are particularly valuable because you can get a good, precise measurement of that time delay if you are just patient and wait years, in this case more than a decade, for the final image to return … The real value in the future will be using a larger sample of these to improve the precision.’…”

A key phrase for me in this Goddard Space Flight Center/NASA article is “…larger sample…to improve the precision….”

Knowledge, Wisdom and Living Amidst Greatness and Beauty

NASA, ESA and the Hubble Heritage Team's image of the Westerlund 2 star cluster. (2015)A great deal of what we know about about this universe — its size, age and expansion rate — comes from data that’s been collected during my lifetime. Much of it from analysis of observations made at the edge of what our instruments can detect.

Very little of our new knowledge matches, in a literal and metaphor-free way, to the Old Testament’s mythic images.

I could let that bother me, or decide that — since Abraham, Moses and all lived before the days of space telescopes — everything we’ve learned since 1650 is Satanic.5

Or that religion in general and Christianity in particular is unscientific: and therefore stupid and old-fashioned.

I could, but I won’t. And, since I’m a Catholic, ignoring this wonder-packed cosmos and what we’re learning about it isn’t required.

“Now if out of joy in their beauty they thought them gods,
let them know how far more excellent is the Lord than these;
for the original source of beauty fashioned them.
“Or if they were struck by their might and energy,
let them realize from these things how much more powerful is the one who made them.
“For from the greatness and the beauty of created things
their original author, by analogy, is seen.
(Wisdom 13:35)

I’ve talked about that, and why I don’t see a point in denouncing weather forecasts, before. Often:

1 Names, designations and a galaxy:

2 Stars, mostly:

3 Supernovae:

4 Bending light:

5 Cosmologies, a chronology and distant stars:

About Brian H. Gill

I was born in 1951. I'm a husband, father and grandfather. One of the kids graduated from college in December, 2008, and is helping her husband run businesses and raise my granddaughter; another is a cartoonist and artist; #3 daughter is a writer; my son is developing a digital game with #3 and #1 daughters. I'm also a writer and artist.
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2 Responses to Supernova Requiem: Reruns From a Gravity Lens

  1. irishbrigid says:

    Missing comma: “over which nation’s culture’s or language’s name”

    The Friendly Neighborhood Proofreader

Thanks for taking time to comment!