Insight Into Dark Energy From Spectacular Ultraviolet Flash – May Finally Explain How White Dwarfs Explode and the Creation of Iron

Exploding Star

For just the second time ever, astrophysicists have spotted a spectacular flash of ultraviolet (UV) light accompanying a white dwarf explosion.

An extremely rare type of supernova, the event is poised to offer insights into several long-standing mysteries, including what causes white dwarfs to explode, how dark energy accelerates the cosmos and how the universe creates heavy metals, such as iron.

“The UV flash is telling us something very specific about how this white dwarf exploded,” said Northwestern University astrophysicist Adam Miller, who led the research. “As time passes, the exploded material moves farther away from the source. As that material thins, we can see deeper and deeper. After a year, the material will be so thin that we will see all the way into the center of the explosion.”

At that point, Miller said, his team will know more about how this white dwarf — and all white dwarfs, which are dense remnants of dead stars — explode.

The paper will be published today (July 23, 2020) in the Astrophysical Journal.

SN2019yvq Supernova

The blue dot marks the approximate location of the supernova event, dubbed SN2019yvq, which occurred in a relatively nearby galaxy 140 million light-years from Earth, very close to tail of the dragon-shaped Draco constellation. Credit: Northwestern University

Miller is a fellow in Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and director of the Legacy Survey of Space and Time Corporation Data Science Fellowship Program.

Common event with a rare twist

Using the Zwicky Transient Facility in California, researchers first spotted the peculiar supernova in December 2019 — just a day after it exploded. The event, dubbed SN2019yvq, occurred in a relatively nearby galaxy located 140 million light-years from Earth, very close to tail of the dragon-shaped Draco constellation.

Within hours, astrophysicists used NASA’s Neil Gehrels Swift Observatory to study the phenomenon in ultraviolet and X-ray wavelengths. They immediately classified SN2019yvq as a type Ia (pronounced “one-A”) supernova, a fairly frequent event that occurs when a white dwarf explodes.

G299 Type Ia Supernova

A previous type Ia supernova. Credit: NASA/CXC/U.Texas

“These are some of the most common explosions in the universe,” Miller said. “But what’s special is this UV flash. Astronomers have searched for this for years and never found it. To our knowledge, this is actually only the second time a UV flash has been seen with a type Ia supernova.”

Heated mystery

The rare flash, which lasted for a couple days, indicates that something inside or nearby the white dwarf was incredibly hot. Because white dwarfs become cooler and cooler as they age, the influx of heat puzzled astronomers.

“The simplest way to create UV light is to have something that’s very, very hot,” Miller said. “We need something that is much hotter than our sun — a factor of three or four times hotter. Most supernovae are not that hot, so you don’t get the very intense UV radiation. Something unusual happened with this supernova to create a very hot phenomenon.”

Miller and his team believe this is an important clue to understanding why white dwarfs explode, which has been a long-standing mystery in the field. Currently, there are multiple competing hypotheses. Miller is particularly interested in exploring four different hypotheses, which match his team’s data analysis from SN2019yvq.

  1. Potential scenarios that could cause a white dwarf to explode with a UV flash are:A white dwarf consumes its companion star and becomes so large and unstable that it explodes. The white dwarf’s and companion star’s materials collide, causing a flash of UV emission;
  2. Extremely hot radioactive material in the white dwarf’s core mixes with its outer layers, causing the outer shell to reach higher temperatures than usual;
  3. An outer layer of helium ignites carbon within the white dwarf, causing an extremely hot double explosion and a UV flash;
  4. Two white dwarfs merge, triggering an explosion with colliding ejecta that emit UV radiation.

“Within a year,” Miller said, “we’ll be able to figure out which one of these four is the most likely explanation.”

Earth-shattering insights

Once the researchers know what caused the explosion, they will apply those findings to learn more about planet formation and dark energy.

Because most of the iron in the universe is created by type Ia supernovae, better understanding of this phenomenon could tell us more about our own planet. Iron from exploded stars, for example, formed the core of all rocky planets, including Earth.

“If you want to understand how the Earth formed, you need to understand where iron came from and how much iron was needed,” Miller said. “Understanding the ways in which a white dwarf explodes gives us a more precise understanding of how iron is created and distributed throughout the universe.”

Illuminating dark energy

White dwarfs already play an enormous role in physicists’ current understanding of dark energy as well. Physicists predict that white dwarfs all have the same brightness when they explode. So type Ia supernovae are considered “standard candles,” allowing astronomers to calculate exactly how far the explosions lie from Earth. Using supernovae to measure distances led to the discovery of dark energy, a finding recognized with the 2011 Nobel Prize in Physics.

“We don’t have a direct way to measure the distance to other galaxies,” Miller explained. “Most galaxies are actually moving away from us. If there is a type Ia supernova in a distant galaxy, we can use it to measure a combination of distance and velocity that allows us to determine the acceleration of the universe. Dark energy remains a mystery. But these supernovae are the best way to probe dark energy and understand what it is.”

And by better understanding white dwarfs, Miller believes we potentially could better understand dark energy and how fast it causes the universe to accelerate.

“At the moment, when measuring distances, we treat all of these explosions as the same, yet we have good reason to believe that there are multiple explosion mechanisms,” he said. “If we can determine the exact explosion mechanism, we think we can better separate the supernovae and make more precise distance measurements.”


Reference: “The spectacular ultraviolet flash from the peculiar type Ia supernova 2019yvq” by A. A. Miller, M. R. Magee, A. Polin, K. Maguire, E. Zimmerman, Y. Yao, J. Sollerman, S. Schulze, D. A. Perley, M. Kromer, S. Dhawan, M. Bulla, I. Andreoni, E. C. Bellm, K. De, R. Dekany, A. Delacroix, C. Fremling, A. Gal-Yam, D. A. Goldstein, V. Z. Golkhou, A. Goobar, M. J. Graham, I. Irani, M. M. Kasliwal, S. Kaye, Y.-L. Kim, R. R. Laher, A. A. Mahabal, F. J. Masci, P. E. Nugent, E. Ofek, E. S. Phinney, S. J. Prentice, R. Riddle, M. Rigault, B. Rusholme, T. Schweyer, D. L. Shupe, M. T. Soumagnac, G. Terreran, R. Walters, L. Yan, J. Zolkower and S. R. Kulkarni, 23 July 2020, Astrophysical Journal.
DOI: 10.3847/1538-4357/ab9e05

The paper was partially supported by the Large Synoptic Survey Telescope Corporation, the Brinson Foundation and the Moore Foundation.

12 Comments on "Insight Into Dark Energy From Spectacular Ultraviolet Flash – May Finally Explain How White Dwarfs Explode and the Creation of Iron"

  1. John Campbell | July 23, 2020 at 8:53 am | Reply

    Another nail in the coffin of the Big Bang theory and the idea of a 13Bn year old universe.

    Since it takes many Billions of years to create a star capable of collapsing into a white dwarf, it begs the question as to the abundance of iron in the 4.5 Bn year old planet Earth. That iron didn’t get there by any other means than the very ancient remnants of a very ancient star… certainly one considerably older than 8Bn years.

    • Torbjörn Larsson | July 25, 2020 at 7:13 am | Reply

      You keep trolling that – which to the rest of us is another nail in the coffin to your line of trolling. Obviously the science makes progress, and you make little.

      I would have said no progress, but for once you raise a question within a problematic claim. Larger stars live quicker and throw out more material, with the largest stars believed to be the earlier generation precisely due to have lesser heavier elements. By the time Sun was born, there had been many generations of massive stars, and Fe/H ratio is IIRC three orders of magnitude larger than after the first generation of Fe free Pop III stars.

      I haven’t looked into the details, but it isn’t considered a principle problem [ ]. “The entire variety of the elements and isotopes found in today’s universe were created by Big Bang nucleosynthesis, stellar nucleosynthesis, supernova nucleosynthesis, and by nucleosynthesis in exotic events such as neutron star collisions.” The shoe is actually on the other foot, Fe is quite common but then there is a drop in the abundance graph.

      So your claim doesn’t stand up, but the question is interesting.

  2. Or the most logical: in the beginning, God created the heavens (universe) and the earth.

    • Real hypotheses only, thanks.

    • Torbjörn Larsson | July 25, 2020 at 7:17 am | Reply

      Superstition against evidence. We now know the universe happens to be thermodynamically closed and energy sums to zero – flat space over sufficiently large volumes – so 1) it is entirely a natural (closed system) and especially here 2) it isn’t a product of any agency “action” (zero work was done).

      The Planck collaboration 2018 happened to kill cultural ‘gods’. It was beyond time to place modern religion alongside yesterday’s astrology since the two were married at the hip for millenniums.

      • Torbjörn Larsson | July 25, 2020 at 7:21 am | Reply

        ” a natural (closed system)” = a natural (closed) system.

        I should perhaps also add that apologists for religious superstition used to make another evidence free claim, that we could never test their brand of magic. Evidently that fantasy idea too happened to be not describing the fact of the matter.

  3. Torbjörn Larsson | July 25, 2020 at 7:01 am | Reply

    It strikes me as a bit odd to see a stock sequence from an unphysical “movie explosion” (equatorial expanding ring) as an illustration to a supernova article. A hook, but not helpful when reading for understanding.

    On the science, it has been slow going to separate the different white dwarf supernova classes. But observatories are more and better now.

  4. They don’t understand why the universe is slowing but now at a different speed so they call it dark energy.

    • Torbjörn Larsson | July 26, 2020 at 1:24 pm | Reply

      In what sense is the universe “slowing”?

      If we look at the expansion it goes towards an exponential increase in volume, so it is often described as an “accelerated” expansion. But the inner state of the universe is changing from being matter dominated after the hot big bang towards being vacuum energy (“dark energy”) dominated, and is currently at a 70/30 proportion dark energy – which constant energy density is what drives the expansion towards an exponential – and the rest. So the exponent that it approaches is in fact decreasing [ ]. “Current evidence suggests that the expansion rate of the universe is accelerating, which means that the second derivative of the scale factor {\displaystyle {\ddot {a}}(t)}{\ddot {a}}(t) is positive, or equivalently that the first derivative {\displaystyle {\dot {a}}(t)}{\dot {a}}(t) is increasing over time.[5] This also implies that any given galaxy recedes from us with increasing speed over time, i.e. for that galaxy {\displaystyle {\dot {d}}(t)}{\dot {d}}(t) is increasing with time. In contrast, the Hubble parameter seems to be decreasing with time, meaning that if we were to look at some fixed distance d and watch a series of different galaxies pass that distance, later galaxies would pass that distance at a smaller velocity than earlier ones.”

      We know there is dark energy from various independent observations, say the cosmic background radiation spectra IIRC shows it. The recent BOSS release of a galxy sample over 80 % of the universe history – with the cosmic background spectra covering in the history after hot big bang – test that it exist (given space flatness from the spectra) at 6 sigma quality (or ~ 10^-5 uncertainty).

      What we don’t have is an agreed on understanding on why there is a constant energy density of the vacuum, but it is expected from quantum field energy – it fits the “vacuum energy of the universe” with all its fields. The BOSS result is compatible with just a few explanations for its value, so it is exciting progress!

      • Torbjörn Larsson | July 26, 2020 at 1:34 pm | Reply

        “galxy sample” = galaxy sample
        “6 sigma quality (or ~ 10^-5 uncertainty).” = 8 sigma quality (or ~ 10^-5 uncertainty).

        Time to get more coffee…

  5. Regarding “white dwarfs” (stars) and UV flashes. Our star the Sun emits UV radiation regularly. Spectrographs are used to match wavelengths of light with elements in stars. What elements emit UV light?

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