LIGO and Virgo

The two large gravitational-wave observatories in the US and Italy, respectively, which were used to detect the first gravitational waves in 2015.

Introduction to Gravitational Waves: An overview of what gravitational waves are, how they are produced, and the importance of studying their properties.

General Relativity: The theory of gravity and its mathematical foundation.

Einstein Field Equations: The mathematical representation of gravity, which predicts the existence of gravitational waves.

Black Holes: The concept of a black hole, their properties, and how they produce gravitational waves.

Neutron Stars: The densest stars in the universe, and how they also produce gravitational waves.

LIGO and Virgo: The two observatories dedicated to detecting gravitational waves, their history, and their capabilities.

Interferometric Detection: The technique used by LIGO and Virgo to detect gravitational waves.

Noise Sources: Sources of disturbance that can mask or mimic gravitational wave signals, and how they are minimized.

Data Analysis: Processing the raw data from gravitational wave signals to extract meaningful information.

Compact Binary Coalescence: The most common source of gravitational waves, and how they can be studied using LIGO and Virgo.

Signal Classification: Identifying and characterizing different types of gravitational wave signals.

Astrophysics: The study of the properties and behavior of astronomical objects, including those that produce gravitational waves.

Multi-Messenger Astronomy: The study of cosmic events using a variety of different types of signals, including gravitational waves.

Future Directions: The ongoing development of LIGO and Virgo, and the potential for new observatories and technologies to enhance our understanding of gravitational waves.

Gravitational Wave Astrophysics: The study of the astrophysical properties of the sources producing the gravitational waves.

Black Hole Astrophysics: The study of the properties and behavior of black holes.

Neutron Star Astrophysics: The study of the properties and behavior of neutron stars.

Numerical Relativity: The use of computer simulations to study the behavior of objects in strong gravity regimes.

Cosmology: The study of the properties and evolution of the universe as a whole, including the role of gravitational waves.

Quantum Gravity: The theoretical framework that aims to unify quantum mechanics and general relativity, and which may have implications for the study of gravitational waves.

LIGO Hanford: LIGO Hanford is an observatory located in Washington State, USA. It has two 4-kilometer-long arms and is designed to detect gravitational waves in the frequency range of 10 Hz to 10 kHz.

LIGO Livingston: LIGO Livingston is an observatory located in Livingston Parish, Louisiana, USA. It also has two 4-kilometer-long arms and is designed to detect gravitational waves in the same frequency range as LIGO Hanford.

Virgo: Virgo is an observatory located near Pisa, Italy. It has three 3-kilometer-long arms and is designed to detect gravitational waves in the frequency range of 10 Hz to 10 kHz. It works in collaboration with LIGO to detect gravitational waves.

KAGRA: KAGRA is an observatory located in Japan. It has two 3-kilometer-long arms and is designed to detect gravitational waves in the frequency range of 10 Hz to 10 kHz. It became operational in February 2020.

GEO600: GEO600 is an observatory located in Germany. It has two 600-meter-long arms and is designed to detect gravitational waves in the frequency range of 10 Hz to 10 kHz. It works in collaboration with LIGO and Virgo.

INDIGO: The Indian Initiative in Gravitational-wave Observations or INDIGO is a proposed gravitational-wave observatory that is under development in India. It aims to have a sensitivity that is similar to that of LIGO and Virgo.

LISA: The Laser Interferometer Space Antenna or LISA is a proposed gravitational-wave observatory that will be located in space. It will have three spacecraft that will be arranged in an equilateral triangle with arms that are 2.5 million kilometers long. It will be designed to detect gravitational waves in the frequency range of 0.1 mHz to 100 mHz.

What is the purpose of the Laser Interferometer Gravitational-Wave Observatory (LIGO)?

Quote: "designed to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool."

How are the LIGO observatories designed to detect gravitational waves?

Quote: "observatories use mirrors spaced four kilometers apart which are capable of detecting a change of less than one ten-thousandth the charge diameter of a proton."

Who funded and operates the initial LIGO observatories?

Quote: "funded by the United States National Science Foundation (NSF) and were conceived, built and are operated by Caltech and MIT."

When did the initial LIGO observatories collect data, and what was the outcome?

Quote: "collected data from 2002 to 2010 but no gravitational waves were detected."

What improvements were made through the Advanced LIGO project?

Quote: "The Advanced LIGO Project to enhance the original LIGO detectors began in 2008 and continues to be supported by the NSF."

Which organizations contributed to the Advanced LIGO project?

Quote: "with important contributions from the United Kingdom's Science and Technology Facilities Council, the Max Planck Society of Germany, and the Australian Research Council."

When was the detection of gravitational waves reported?

Quote: "The detection of gravitational waves was reported in 2016 by the LIGO Scientific Collaboration (LSC) and the Virgo Collaboration."

How many scientists are involved in the LSC, and how many active users are there for Einstein@Home?

Quote: "more than 1000 scientists worldwide, as well as 440,000 active Einstein@Home users as of December 2016."

What was the significant recognition received for the LIGO detector and gravitational wave observation?

Quote: "In 2017, the Nobel Prize in Physics was awarded to Rainer Weiss, Kip Thorne and Barry C. Barish "for decisive contributions to the LIGO detector and the observation of gravitational waves"."

How many runs has LIGO conducted, and how many gravitational wave detections have been made?

Quote: "LIGO has made three runs... and made 90 detections of gravitational waves."

What were the outcomes of the first three runs (O1, O2, O3) in terms of detections?

Quote: "The first run, O1... made the first three detections, all black hole mergers. The second run, O2... made eight detections, seven black hole mergers, and the first neutron star merger. The third run, O3... made the first detection of a merger of a neutron star with a black hole."

When did the third run (O3) begin, and why was it suspended?

Quote: "The third run, O3, began on 1 April 2019; it was divided into O3a, from 1 April to 30 September 2019, and O3b, from 1 November 2019 until it was suspended on 27 March 2020 due to COVID-19."

What is the current status of observations after the COVID-caused stop?

Quote: "The gravitational wave observatories LIGO, Virgo, and KAGRA are coordinating to continue observations after the COVID-caused stop."

When did LIGO's O4 observing run start?

Quote: "LIGO's O4 observing run started on 24 May 2023."

What is the sensitivity goal of LIGO for binary neutron star mergers?

Quote: "LIGO projects a sensitivity goal of 160–190 Mpc for binary neutron star mergers."

What sensitivities do Virgo and KAGRA achieve for binary neutron star mergers?

Quote: "Virgo 80–115 Mpc, KAGRA greater than 1 Mpc."