Astronomers spot the same supernova three times -- and predict a fourth sighting in 16 years

Date:
September 13, 2021
Source:
University of Copenhagen - Faculty of Science
Summary:
An enormous amount of gravity from a cluster of distant galaxies
causes space to curve so much that light from them is bent and
emanated our way from numerous directions. This 'gravitational
lensing' effect has allowed astronomers to observe the same
exploding star in three different places in the heavens. They
predict that a fourth image of the same explosion will appear in
the sky by 2037. The study provides a unique opportunity to explore
not just the supernova itself, but the expansion of our universe.



FULL STORY ==========================================================================
An enormous amount of gravity from a cluster of distant galaxies causes
space to curve so much that light from them is bent and emanated our way
from numerous directions. This "gravitational lensing" effect has allowed University of Copenhagen astronomers to observe the same exploding star
in three different places in the heavens. They predict that a fourth
image of the same explosion will appear in the sky by 2037. The study,
which has just been published in the journal Nature Astronomy, provides
a unique opportunity to explore not just the supernova itself, but the expansion of our universe.


==========================================================================
One of the most fascinating aspects of Einstein's famed theory of
relativity is that gravity is no longer described as a force, but as a "curvature" of space itself. The curvature of space caused by heavy
objects does not just cause planets to spin around stars, but can also
bend the orbit of light beams.

The heaviest of all structures in the universe -- galaxy clusters made
up of hundreds or thousands of galaxies -- can bend light from distant
galaxies behind them so much that they appear to be in a completely
different place than they actually are.

But that's not it: light can take several paths around a galaxy cluster,
making it possible for us to get lucky and make two or more sightings of
the same galaxy in different places in the sky using a powerful telescope.

Supernova de'ja`-vu Some routes around a galaxy cluster are longer than
others, and therefore take more time. The slower the route, the stronger
the gravity; yet another astonishing consequence of relativity. This
staggers the amount of time needed for light to reach us, and thereby
the different images that we see.



==========================================================================
This wondrous effect has allowed a team of astronomers at the Cosmic Dawn Center -- a basic research center run by the Niels Bohr Institute at
the University of Copenhagen and DTU Space at the Technical University
of Denmark - - along with their international partners, to observe a
single galaxy in no less than four different places in the sky.

The observations were made using the infrared wavelength range of the
Hubble Space Telescope.

By analyzing the Hubble data, researchers noted three bright light
sources in a background galaxy that were evident in a previous set of observations from 2016, which disappeared when Hubble revisited the area
in 2019. These three sources turned out to be several images of a single
star whose life ended in a colossal explosion known as a supernova.

"A single star exploded 10 billion years ago, long before our own sun
was formed. The flash of light from that explosion has just reached us," explains Associate Professor Gabriel Brammer of the Cosmic Dawn Center,
who led the study with Professor Steven Rodney of the University of
South Carolina.

The supernova, nicknamed "SN-Requiem," can be seen in three of the four "mirrored images" of the galaxy. Each image presents a different view of
the explosive supernova's development. In the final two images, it has
not yet exploded. But, by examining how galaxies are distributed within
the galaxy cluster and how these images are distorted by curved space,
it is actually possible to calculate how "delayed" these images are.



==========================================================================
This has allowed astronomers to make a remarkable prediction: "The fourth
image of the galaxy is roughly 21 years behind, which should allow
us to see the supernova explode one more time, sometime around 2037,"
explains Gabriel Brammer.

Can teach us more about the universe Should we get to witness the
SN-Requiem explosion again in 2037, it will not only confirm our
understanding of gravity, but also help to shed light on another
cosmological riddle that has emerged in the last few years, namely the expansion of our universe.

We know that the universe is expanding, and that different methods
allow us to measure by how fast. The problem is that the various
measurement methods do not all produce the same result, even when
measurement uncertainties are taken into account. Could our observational techniques be flawed, or -- more interestingly -- will we need to revise
our understandings of fundamental physics and cosmology? "Understanding
the structure of the universe is going to be a top priority for the main earth-based observatories and international space organizations over the
next decade.Studies planned for the future will cover much of the sky
and are expected to reveal dozens or even hundreds of rare gravitational
lenses with supernovae like SN Requiem," Brammer elaborates: "Accurate measurements of delays from such sources provide unique and reliable determinations of cosmic expansion and can even help reveal the properties
of dark matter and dark energy." Dark matter and dark energy are the mysterious matter believed to make up 95% of our universe, whereas we
can only see 5%. The perspectives of gravitational lenses are promising! ========================================================================== Story Source: Materials provided by University_of_Copenhagen_-_Faculty_of_Science. Note: Content may be
edited for style and length.


========================================================================== Journal Reference:
1. Steven A. Rodney, Gabriel B. Brammer, Justin D. R. Pierel,
Johan Richard,
Sune Toft, Kyle F. O'Connor, Mohammad Akhshik, Katherine
E. Whitaker. A gravitationally lensed supernova with an
observable two-decade time delay. Nature Astronomy, 2021; DOI:
10.1038/s41550-021-01450-9 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/09/210913135608.htm

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