clocks'
Radio telescope observations of Milky Way pulsars reveal spacetime
distortions likely caused by enormous gravitational waves rolling through everything in existence

Date:
June 29, 2023
Source:
National Science Foundation
Summary:
You can't see or feel it, but everything around you -- including
your own body -- is slowly shrinking and expanding. It's the weird,
spacetime- warping effect of gravitational waves passing through
our galaxy. New results are the first evidence of the gravitational
wave background -- a sort of soup of spacetime distortions pervading
the entire universe and long predicted to exist by scientists.


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==========================================================================
FULL STORY ==========================================================================
You can't see or feel it, but everything around you -- including
your own body -- is slowly shrinking and expanding. It's the weird, spacetime-warping effect of gravitational waves passing through our
galaxy, according to a new study by a team of researchers with the
U.S. National Science Foundation's NANOGrav Physics Frontiers Center.

The findings published today in The Astrophysical Journal Letters are
from the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), a collaborative team of researchers from more than 50
institutions in the U.S.

and abroad. The team conducted an analysis of burned-out stars known as millisecond pulsars, which rotate hundreds of times per second and emit
radio pulses like ticks from highly accurate cosmic clocks. The team
discovered what appeared to be variations in the "ticking rate" of such
pulsars by comparing observations of more than 60 pulsars within radio telescope data spanning 15 years. Their analysis provides evidence that
the variations are caused by low- frequency gravitational waves which
are distorting the fabric of physical reality known as spacetime.

According to the NANOGrav team's findings, the spatial distortion
from the gravitational waves creates the appearance that the pulsars' radio-signal ticking rates are changing. But really, it's the stretching
and squeezing of space between Earth and the pulsars which causes their
radio pulses to arrive at Earth billionths of seconds earlier or later
than expected. The results are the first evidence of the gravitational
wave background -- a sort of soup of spacetime distortions pervading
the entire universe and long predicted to exist by scientists.

"The NSF NANOGrav team created, in essence, a galaxy-wide detector
revealing the gravitational waves that permeate our universe," said NSF Director Sethuraman Panchanathan. "The collaboration involving research institutions across the U.S. shows that world-class scientific innovation
can, should and does reach every part of our nation." Gravitational
waves were first predicted by Albert Einstein in 1916. They would not be confirmed until 2015, when the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected spacetime ripples passing through the Earth.

Although the source of those gravitational ripples was a collision of
two far- off black holes, the resulting spatial distortion that LIGO
detected was smaller than the nucleus of an atom.

By comparison, the apparent pulsar time shift measured by the NANOGrav
team is a few hundred billionths of a second and represents a flexing of spacetime between Earth and the pulsars about the length of a football
field. Those spacetime distortions were caused by gravitational waves
so immense that the distance between two crests is 2-10 light-years,
or about 9-90 trillion kilometers.

"These are by far the most powerful gravitational waves known to exist,"
said West Virginia University astrophysicist Maura McLaughlin, co-director
of the NANOgrav Physics Frontiers Center. "Detecting such gargantuan gravitational waves requires a similarly massive detector, and patience."
Using 15 years of astronomical data recorded by radio telescopes at NSF- supported observatories -- including Green Bank Observatory in West
Virginia, the Very Large Array in Socorro, New Mexico, and Arecibo
Observatory in Puerto Rico -- the NANOGrav team created a "detector"
of 67 pulsars distributed all across the sky and compared the ticking
rate of pairs of those pulsars. Through a sophisticated data analysis,
they deduced the presence of the gravitational wave background causing
the distortion of space, and thus explained the apparent timing changes
of the pulsars.

This is the first evidence for gravitational waves at these low
frequencies," said Vanderbilt University astrophysicist Stephen
Taylor, chair of the NANOGrav collaboration and co-leader of the
research effort. "The likely source of these waves are distant pairs of close-orbiting, ultra-massive black holes." "There is so much we have
yet to understand about the physical nature of the universe and that's
why the National Science Foundation supports daring team efforts like
NANOGrav -- to expand our knowledge for the benefit of society," said
NSF Assistant Director for Mathematical and Physical Sciences Sean L.

Jones.

The team's results are providing new insights into how galaxies evolve
and how supermassive black holes grow and merge. The widespread spacetime distortion revealed in their findings implies that extremely massive pairs
of black holes may be similarly widespread across the universe, numbering perhaps in the hundreds of thousands or even millions. Eventually, the
NANOGrav team expects to be able to identify specific supermassive black
hole pairs by tracing the gravitational waves they emit. They may even
uncover traces of gravitational waves from the very early universe.

"While our early data told us that we were hearing something, we now
know that it's the music of the gravitational universe," said NANOGrav co-director and Oregon State University astrophysicist Xavier Siemens. "As
we keep listening, individual instruments will come to the fore in this
cosmic orchestra."
* RELATED_TOPICS
o Space_&_Time
# Black_Holes # Space_Telescopes # Cosmology #
Astrophysics # Astronomy # Galaxies # Space_Exploration
# Big_Bang
* RELATED_TERMS
o Gravitational_wave o General_relativity o
Dark_matter o Big_Bang o Holographic_Universe o
Cosmic_microwave_background_radiation o Shape_of_the_Universe
o Extraterrestrial_life

========================================================================== Story Source: Materials provided by National_Science_Foundation. Original written by Jason Stoughton. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. Gabriella Agazie, Akash Anumarlapudi, Anne M. Archibald, Zaven
Arzoumanian, Paul T. Baker, Bence Be'csy, Laura Blecha, Adam
Brazier, Paul R. Brook, Sarah Burke-Spolaor, Rand Burnette, Robin
Case, Maria Charisi, Shami Chatterjee, Katerina Chatziioannou,
Belinda D. Cheeseboro, Siyuan Chen, Tyler Cohen, James M. Cordes,
Neil J. Cornish, Fronefield Crawford, H. Thankful Cromartie,
Kathryn Crowter, Curt J. Cutler, Megan E. DeCesar, Dallas DeGan,
Paul B. Demorest, Heling Deng, Timothy Dolch, Brendan Drachler,
Justin A. Ellis, Elizabeth C. Ferrara, William Fiore, Emmanuel
Fonseca, Gabriel E. Freedman, Nate Garver-Daniels, Peter A.

Gentile, Kyle A. Gersbach, Joseph Glaser, Deborah C. Good, Kayhan
Gu"ltekin, Jeffrey S. Hazboun, Sophie Hourihane, Kristina Islo,
Ross J.

Jennings, Aaron D. Johnson, Megan L. Jones, Andrew R. Kaiser,
David L.

Kaplan, Luke Zoltan Kelley, Matthew Kerr, Joey S. Key, Tonia
C. Klein, Nima Laal, Michael T. Lam, William G. Lamb, T. Joseph
W. Lazio, Natalia Lewandowska, Tyson B. Littenberg, Tingting Liu,
Andrea Lommen, Duncan R.

Lorimer, Jing Luo, Ryan S. Lynch, Chung-Pei Ma, Dustin R. Madison,
Margaret A. Mattson, Alexander McEwen, James W. McKee, Maura A.

McLaughlin, Natasha McMann, Bradley W. Meyers, Patrick M. Meyers,
Chiara M. F. Mingarelli, Andrea Mitridate, Priyamvada Natarajan,
Cherry Ng, David J. Nice, Stella Koch Ocker, Ken D. Olum, Timothy
T. Pennucci, Benetge B. P. Perera, Polina Petrov, Nihan S. Pol,
Henri A. Radovan, Scott M. Ransom, Paul S. Ray, Joseph D. Romano,
Shashwat C. Sardesai, Ann Schmiedekamp, Carl Schmiedekamp, Kai
Schmitz, Levi Schult, Brent J.

Shapiro-Albert, Xavier Siemens, Joseph Simon, Magdalena S. Siwek,
Ingrid H. Stairs, Daniel R. Stinebring, Kevin Stovall, Jerry
P. Sun, Abhimanyu Susobhanan, Joseph K. Swiggum, Jacob Taylor,
Stephen R. Taylor, Jacob E.

Turner, Caner Unal, Michele Vallisneri, Rutger van Haasteren,
Sarah J.

Vigeland, Haley M. Wahl, Qiaohong Wang, Caitlin A. Witt, Olivia
Young.

The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave
Background. The Astrophysical Journal Letters, 2023; 951 (1):
L8 DOI: 10.3847/2041-8213/acdac6 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2023/06/230629125650.htm

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