Path to Detecting All Blackholes in the Universe All the Time

Gravity Wave detections are rapidly increasing. The first gravity wave was detected in 2015. The science needed to accomplish this is described in the Veratasium videos below. They needed to create single wavelength lasers and use one-megawatt of power to detect differences of one trillionth of a wavelength.

Gravitational-wave astronomy is a completely new way to observe the universe. The breakthroughs made by the National Science Foundation’s Advanced LIGO, and its partner observatory Advanced Virgo are only the beginning of our exploration of the gravitational-wave sky. A white paper describes the research and development that will be needed over the next decade to realize “Cosmic Explorer”. This will be a detection system for blackholes across the Universe.

Cosmic Explorer together with a network of planned and proposed observatories spanning the gravitational-wave spectrum, including LISA and the Einstein Telescope will be able to determine the nature of the densest matter in the universe; reveal the universe’s binary black hole population throughout cosmic time; provide an independent probe of the history of the expanding universe; explore warped spacetime with unprecedented fidelity; and expand our knowledge of how massive stars live, die, and create the matter we see today.

Upgrades to the existing gravity detectors have already enabled one to two detections per week of blackhole and neutron star collisions to be made. The more sensitive gravity wave detectors are then more collisions across a larger the volume of space will be possible. This means the frequency of detections increases.

There will be more regular and more frequent detections. Future improvements to sensitivity will mean black hole and neutron star mergers from more of the universe will be detected. This will mean in about ten years that detections will occur multiple times per day.

The next A+ design incorporates many of the elements identified in the first DAWN white paper to produce a design with strain sensitivity corresponding to a BNS/BBH range of ∼ 350/2240 Mpc. This would lead to an increase in range of 1.6X and 1.8X respectively for BNS and 20Msun BBH mergers, or alternatively a detection rate increase of 6.4X (BNS) and 4.4X (BBH) with respect to Advanced LIGO. They will use frequency-dependent squeezing and improved test mass coatings for the improvements over the next six years.

Researchers envisage potentially three detector epochs post Advanced LIGO baseline over the next 25 years with working titles A+, LIGO Voyager and LIGO Cosmic Explorer.

After the Advanced Plus detector will be LIGO Voyager. LIGO Voyager would have three times the detection range to a BNS range (to 1100 Mpc). This would have a low-frequency cutoff down to 10 Hz.

The existing LIGO and Virgo instruments have opened a new window on the universe, but they are, like Galileo’s first telescope, just sensitive enough to observe the brightest sources. Today the Advanced LIGO detectors now see signals roughly weekly; when the recently funded “A+” upgrade comes online in 2024, it will deliver roughly ten detections per week (1-2 detections per day). This may be the most sensitive detector to be installed in the present LIGO infrastructure, and may exhaust the lifetime of the LIGO vacuum systems. The above science goals are only achievable by making observations of these bright sources with significantly higher fidelity and over a wider frequency band, as well as by observing much more distant sources. This requires a new generation of observatories with an order of magnitude greater sensitivity in the audio frequency band than current observatories allow. Researchers envision the U.S. contribution to the global third-generation ground-based gravitational-wave detector network to be Cosmic Explorer, a 40 km L-shaped observatory designed to greatly deepen and clarify humanity’s gravitational-wave view of the cosmos.

Cosmic Explorer will be able to detect merging stellar-mass black holes at redshifts of up to z ∼ 20. This immense reach will reveal for the first time the complete population of stellar-mass black holes, starting from an epoch when the universe was still assembling its first stars.

From 50 Gravity Wave Detections Per Year to Millions Per Year

The first stage (CE1) scales up Advanced LIGO technologies to create an L-shaped interferometric detector with arms that are closer to the wavelength of the gravitational waves targeted by ground-based detectors. A facility with 40 km long arms is the baseline for achieving Cosmic Explorer’s science goals. The second stage (CE2) upgrades the 40 km detector’s core optics using cryogenic technologies and new mirror substrates to realize a full order of magnitude sensitivity improvement beyond Advanced LIGO.

With its spectacular sensitivity, Cosmic Explorer will see gravitational-wave sources across the history of the universe. Sources that are barely detectable by Advanced LIGO will be resolved with incredible precision. The explosion in the number of detected sources — up to millions per year — and the fidelity of observations will have wide-ranging impact in physics and astronomy.

A series of 2020 Decadal Survey White Papers describes the science case for a third-generation gravitational-wave detector network. To achieve these science goals, Cosmic Explorer must push the low-frequency sensitivity limit of the detector down by a factor of two, from 10 Hz to 5 Hz, and push the detector sensitivity well beyond the limits of the LIGO facilities. The leap in sensitivity between
second- and third-generation detectors will take the scientific community from first detections to seeing and characterizing every stellar-mass black hole merger in the universe.

Deci-Hertz Gravity Wave Observatory

The Deci-Hertz Interferometer Gravitational wave Observatory (or DECIGO) is a proposed Japanese, space-based, gravitational wave observatory. The laser interferometric gravitational wave detector is so named because it is to be most sensitive in the frequency band between 0.1 and 10 Hz,filling in the gap between the sensitive bands of LIGO and LISA. If funding can be found, its designers hope to launch it in 2027.

The design is similar to LISA, with three zero-drag satellites in a triangular arrangement, but using a smaller separation of only 1000 km. The precursor mission B-DECIGO with 100 km long arms is planned to be launched in the late 2020s, target is an Earth orbit with an average altitude of 2000 km.

The DECIGO pre-conceptual design consists of three drag-free spacecraft, whose relative displacements are measured by a differential Fabry–Perot (FP) Michelson interferometer. The arm length of 1,000 km was determined to realize a finesse of 10 with a 1 m diameter mirror and 0.5 μm laser light.

The mass of the mirror is 100 kg and the laser power is 10 W. Three sets of such interferometers sharing the mirrors as arm cavities comprise one cluster of DECIGO. The constellation of DECIGO is composed of four clusters of DECIGO located separately in a heliocentric orbit.

Cosmic Explorer

Arxiv – Astro2020 Ground-Based Technology Development White Paper – Cosmic Explorer: The U.S. Contribution to Gravitational-Wave Astronomy beyond LIGO

The Cosmic Explorer facility baseline requirements are two 40 km ultrahigh-vacuum beam tubes, roughly 1 meter in diameter, built in an L-shape on the surface of flat and seismically quiet land in the United States. The longer arm length will increase the amplitude of the observed signals with effectively no increase in the noise. Although there are areas of detector technology where improvements would lead to incremental increases in the sensitivity and bandwidth of the instruments, the dominant improvement will come from significantly increasing the arm length.

Cosmic Explorer will be realized in two phases. The initial phase, “Cosmic Explorer Stage 1,” is expected to use the technology developed for the “A+” upgrade to Advanced LIGO, scaled up to a 40 km detector with correspondingly better sensitivity. This provides a straightforward approach to significant improvement, as seen in the last rows of Table 1. The second stage, “Cosmic Explorer Stage 2,” improves on the Stage 1 sensitivity with a new set of technologies to reduce the quantum and thermal noises of the detector.

Achieving the mid- and high-frequency performance of Cosmic Explorer requires high-quality optical materials, high-power lasers, and careful control of optical losses in the detector. Achieving the low-frequency performance requires eliminating scattered laser light, mechanically isolating the detector test masses from the environment using high-quality multi-stage suspensions and active seismic isolation, and measuring and subtracting local gravity fluctuations induced by the ground and atmosphere.

For the Cosmic Explorer detectors, technology development is required to extend existing LIGO technology to the scale required for Cosmic Explorer Stage 1, principally to develop larger mirrors and to handle the longer arm lengths; most technologies remain unchanged. Parallel development is required to realize the 2 µm cryogenic silicon technologies for Cosmic Explorer Stage 2. Therefore, throughout the 2020s we will undertake a series of laboratory upgrades for large suspensions, cryogenic silicon, and tabletop prototypes. This R and D effort will identify the most promising approaches for Cosmic Explorer Stage 2, but will not provide a cost estimate for the detector.

The Einstein Telescope, the European vision for a third-generation gravitational-wave detector, would consist of three interferometers formed into a triangle, with 10-kilometer-long arms. To minimize noise, it would be underground and cooled to around 10 K.

Future detectors would allow scientists to differentiate between black holes and speculative objects like wormholes and gravastars.

The technology does not reach its limit with third-generation detectors. There can be further improvements to sensitivity. Detectors with longer arm beyond 40 kilometers are possible.

Detecting Supernovae

Physical Review D – Detection prospects of core-collapse supernovae with supernova-optimized third-generation gravitational-wave detectors

Researchers discuss how to optimize the third-generation gravitational-wave detector to maximize the range to detect core-collapse supernovae. Based on three-dimensional simulations for core-collapse and the corresponding gravitational-wave waveform emitted, the corresponding detection range for these waveforms is limited to within our Galaxy even in the era of third-generation detectors. The corresponding event rate is two per century. Researcher find from the waveforms that to detect core-collapse supernovae with an event rate of one per year. The gravitational-wave detectors need a high strain sensitivity in a frequency range from 100 to 1500 Hz. They also explore detector configurations technologically beyond the scope of third-generation detectors. They find with these improvements, the event rate for gravitational-wave observations from core-collapse supernovae is still low, but is improved to one in twenty years.

Lectures on the Future of Gravity Wave Detectors and Gravity Wave Science

An entirely new window into our universe has opened up. We will be able to increase sensitivity to detect the cosmic neutrino background. This will let us look not just at microwaves from the dawn of time but neutrinos.

We will be able explore and understand the activity that has been happening our universe. We will be able to see and understand big collisions and explosions. This will tell us a lot about physics and the universe.

Leading experts (including Nobel Prize Winner Rai Weiss) discuss the future and far future of gravitational wave astronomy from upgrading LIGO to larger ground based detectors such as The Einstein telescope and The Cosmic Explorer to spaced missions such as LISA, DECIGO and the Big Bang Observer. For a timeline of content see below:
RW =Rainer Weiss – MIT
BS =Bangalore Sathyaprakash – Penn State
SR = Shelia Rowan – Glasgow University
GG= Gabriela González Louisiana State
BFS = Bernard F Shutz – Cardiff University
JB = John F Beacom – Ohio State
MAM = Miguel Alejandro Mostafá – Penn State
00:00 SR on invisible messengers
00:30 narration on gravitational waves
1:21 RW on the first discovery
4:47 BS on first discovery
5:10 RW on the colliding black holes
5:30 BS on the mystery of the black hole masses and spins
6:41 GG on discoveries to date
7:46 narration on improving LIGO
8:10 SR on new technologies for imprivng ground based detectors
10:03 BS on upgrading LIGO
10:25 SR on new ground based detectors
11:38 narration on the Hubble tension
12:24 BFS on standard sirens and solving the Hubble tension
13:35 GG on larger ground based detectors beyond LIGO
15:19 RW on the above topic
15:44 BFS on the above topic
16:08 narration on LISA
16:23 SR on the need for a space based mission
17:39 RW on LISA
19:13 BFS on LISA
20:35 SR on LISA
20:48 RW on LISA
21:01 GG on LISA
22:26 RW on LISA
22:54 BS on surprises
23:17 RW on LISA
24:26 BS on pulsar timing arrays
25:39 narration on the mysteries that gravitational waves can unlock
25:55 BS on dark matter
27:26 narration on modified gravity
27:29 SR on modified gravity
29:14 BFS on dark matter
29:48 BS on dark energy
30:32 GG on dark energy
30:49 BFS on dark energy
32:27 BS on quantum gravity
33:49 BFS on quantum gravity
36:18 narration on multi messenger astronomy
36:42 JB on above topic
37:06 MAM on neutron star collisions
38:02 JB on neutrinos
38:27 MAM on AMON
40:39 narration on how do black hole and black binaries form
40:49 RW on above topic
41:12 JB on neutrinos and above topic
42:27 JB on the CNB cosmic neutrino background
44:26 MAM on cosmic rays
45:47 BFS on missions to look for primordial gravitational waves
48:07 RW on the Big Bang Observer

SOURCES- Arxiv, Physical Review D, Cosmic Explorer, Veritasium Youtube, Kip Thorne,
Written By Brian Wang, Nextbigfuture.com

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