To find giant black holes, start with Jupiter

Date:
June 30, 2020
Source:
Vanderbilt University
Summary:
On a quest to find the Universe's largest black holes, researchers
identify the center of the solar system within 100 meters.



FULL STORY ========================================================================== [Illustration of black | Credit: (c) vchalup / stock.adobe.com]
Illustration of black hole, warped spacetime (stock image).

Credit: (c) vchalup / stock.adobe.com [Illustration of black | Credit: (c) vchalup / stock.adobe.com] Illustration of black hole, warped spacetime
(stock image).

Credit: (c) vchalup / stock.adobe.com Close The revolution in our
understanding of the night sky and our place in the universe began when
we transitioned from using the naked eye to a telescope in 1609. Four
centuries later, scientists are experiencing a similar transition in
their knowledge of black holes by searching for gravitational waves.


==========================================================================
In the search for previously undetected black holes that are billions
of times more massive than the sun, Stephen Taylor, assistant professor
of physics and astronomy and former astronomer at NASA's Jet Propulsion Laboratory (JPL) together with the North American Nanohertz Observatory
for Gravitational Waves (NANOGrav) collaboration has moved the field
of research forward by finding the precise location -- the center of
gravity of our solar system -- with which to measure the gravitational
waves that signal the existence of these black holes.

The potential presented by this advancement, co-authored by Taylor,
was published in the journal the Astrophysical Journal in April 2020.

Black holes are regions of pure gravity formed from extremely warped
spacetime.

Finding the most titanic black holes in the Universe that lurk at the
heart of galaxies will help us understand how such galaxies (including
our own) have grown and evolved over the billions of years since their formation. These black holes are also unrivaled laboratories for testing fundamental assumptions about physics.

Gravitational waves are ripples in spacetime predicted by Einstein's
general theory of relativity. When black holes orbit each other in pairs,
they radiate gravitational waves that deform spacetime, stretching and squeezing space.

Gravitational waves were first detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2015, opening new vistas on the
most extreme objects in the universe. Whereas LIGO observes relatively
short gravitational waves by looking for changes in the shape of a 4-km
long detector, NANOGrav, a National Science Foundation (NSF) Physics
Frontiers Center, looks for changes in the shape of our entire galaxy.

Taylor and his team are searching for changes to the arrival rate of
regular flashes of radio waves from pulsars. These pulsars are rapidly
spinning neutron stars, some going as fast as a kitchen blender. They also
send out beams of radio waves, appearing like interstellar lighthouses
when these beams sweep over Earth. Over 15 years of data have shown
that these pulsars are extremely reliable in their pulse arrival rates,
acting as outstanding galactic clocks.

Any timing deviations that are correlated across lots of these pulsars
could signal the influence of gravitational waves warping our galaxy.



========================================================================== "Using the pulsars we observe across the Milky Way galaxy, we are trying
to be like a spider sitting in stillness in the middle of her web,"
explains Taylor.

"How well we understand the solar system barycenter is critical as we
attempt to sense even the smallest tingle to the web." The solar system barycenter, its center of gravity, is the location where the masses of
all planets, moons, and asteroids balance out.

Where is the center of our web, the location of absolute stillness in
our solar system? Not in the center of the sun as many might assume,
rather it is closer to the surface of the star. This is due to Jupiter's
mass and our imperfect knowledge of its orbit. It takes 12 years for
Jupiter to orbit the sun, just shy of the 15 years that NANOGrav has
been collecting data. JPL's Galileo probe (named for the famed scientist
that used a telescope to observe the moons of Jupiter) studied Jupiter
between 1995 and 2003, but experienced technical maladies that impacted
the quality of the measurements taken during the mission.

Identifying the center of the solar system's gravity has long been
calculated with data from Doppler tracking to get an estimate of the
location and trajectories of bodies orbiting the sun. "The catch is
that errors in the masses and orbits will translate to pulsar-timing
artifacts that may well look like gravitational waves," explains JPL
astronomer and co-author Joe Simon.

Taylor and his collaborators were finding that working with existing solar system models to analyze NANOGrav data gave inconsistent results. "We
weren't detecting anything significant in our gravitational wave searches between solar system models, but we were getting large systematic
differences in our calculations," notes JPL astronomer and the paper's
lead author Michele Vallisneri. "Typically, more data delivers a more
precise result, but there was always an offset in our calculations."
The group decided to search for the center of gravity of the solar system
at the same time as sleuthing for gravitational waves. The researchers
got more robust answers to finding gravitational waves and were able to
more accurately localize the center of the solar system's gravity to
within 100 meters. To understand that scale, if the sun were the size
of a football field, 100 meters would be the diameter of a strand of
hair. "Our precise observation of pulsars scattered across the galaxy
has localized ourselves in the cosmos better than we ever could before,"
said Taylor. "By finding gravitational waves this way, in addition to
other experiments, we gain a more holistic overview of all different kinds
of black holes in the Universe." As NANOGrav continues to collect ever
more abundant and precise pulsar timing data, astronomers are confident
that massive black holes will show up soon and unequivocally in the data.

Taylor was partially supported by an appointment to the NASA Postdoctoral Program at JPL. The NANOGrav project receives support from the NSF Physics Frontier Center award #1430284 and this work was supported in part by
NSF Grant PHYS-1066293 and by the hospitality of the Aspen Center for
Physics. Data for this project were collected using the facilities of
the Green Bank Observatory and the Arecibo Observatory.


========================================================================== Story Source: Materials provided by Vanderbilt_University. Original
written by Marissa Shapiro. Note: Content may be edited for style
and length.


========================================================================== Journal Reference:
1. M. Vallisneri, S. R. Taylor, J. Simon, W. M. Folkner, R. S. Park, C.

Cutler, J. A. Ellis, T. J. W. Lazio, S. J. Vigeland, K. Aggarwal, Z.

Arzoumanian, P. T. Baker, A. Brazier, P. R. Brook, S. Burke-Spolaor,
S.

Chatterjee, J. M. Cordes, N. J. Cornish, F. Crawford,
H. T. Cromartie, K.

Crowter, M. DeCesar, P. B. Demorest, T. Dolch, R. D. Ferdman, E. C.

Ferrara, E. Fonseca, N. Garver-Daniels, P. Gentile, D. Good, J. S.

Hazboun, A. M. Holgado, E. A. Huerta, K. Islo, R. Jennings,
G. Jones, M.

L. Jones, D. L. Kaplan, L. Z. Kelley, J. S. Key, M. T. Lam,
L. Levin, D.

R. Lorimer, J. Luo, R. S. Lynch, D. R. Madison, M. A. McLaughlin,
S. T.

McWilliams, C. M. F. Mingarelli, C. Ng, D. J. Nice, T. T. Pennucci,
N. S.

Pol, S. M. Ransom, P. S. Ray, X. Siemens, R. Spiewak, I. H. Stairs,
D. R.

Stinebring, K. Stovall, J. K. Swiggum, R. van Haasteren,
C. A. Witt, W.

W. Zhu. Modeling the Uncertainties of Solar System Ephemerides
for Robust Gravitational-wave Searches with Pulsar-timing
Arrays. The Astrophysical Journal, 2020; 893 (2): 112 DOI:
10.3847/1538-4357/ab7b67 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200630125136.htm

--- up 23 weeks, 2 hours, 39 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1337:3/111)