The universe’s hum and an opportunity to explore

Source: The post is based on the article “The universe’s hum and an opportunity to explore” published in “The Indian Express” on 6th July 2023.

Syllabus: GS 3 – Awareness in the field of space

News: Recently, astronomers from various initiatives have reported the detection of ultra-low frequency gravitational waves, allowing to probe previously unseen parts of the universe.

What are gravitational waves?

Read here: What is LIGO-India, the Indian node in the global network of labs to probe the universe

How are scientists trying to detect gravitational waves?

Scientists are using a network of millisecond pulsars distributed across our galaxy as a giant detector of gravitational waves. Millisecond pulsars are very dense stars that rotate rapidly, emitting extremely regular pulses of radio waves. Scientists record the timing of these pulses over many years. If a gravitational wave passes through the space between the Earth and a pulsar, it will slightly change the time it takes for the pulses to reach us. By analyzing changes in these timing patterns, scientists hope to detect the presence of gravitational waves.

What is LISA and how does it work?

LISA, short for Laser Interferometer Space Antenna, is a future project (scheduled to be launched in the early 2030s) by the European Space Agency. It’s designed to detect gravitational waves from space.

LISA will work using three spacecraft. They will be arranged in a triangle, millions of kilometers apart. Each spacecraft will shoot a laser beam at the other two, forming three ‘arms’ of laser light.

If a gravitational wave comes through, the distances between the spacecraft change slightly. This makes the laser beams take a little longer or shorter to reach each other.

Scientists can measure these changes in time to detect the gravitational waves. LISA’s large size will help it in finding lower-frequency waves, possibly revealing new space events.

What is the significance and origin of “Nanohertz Waves”?

Nanohertz waves are ultra-low frequency gravitational waves. They are believed to originate from supermassive black holes orbiting each other, typically found at the center of galaxies. When these galaxies collide or merge, the black holes could pair off and produce these waves.

These waves could also come from other exotic events like cosmic strings or early universal expansion, known as inflation.

The detection of nanohertz waves, often referred to as the “hum” of the universe, could give us a way to study the earliest events in the universe and uncover mysteries of its formation and evolution.

What are the Challenges with Detecting Low Frequency Waves, like nanohertz waves?

Detecting low frequency gravitational waves like nanohertz waves presents unique challenges:

Need for larger detectors: Low frequency waves require larger detectors to be detected. For instance, to pick up nanohertz waves, a detector as big as a galaxy would be needed, which is practically impossible to build.

Complex data analysis: It is not easy to identify the tiny signal from the background noise. It involves collecting data over several years and performing intricate statistical analyses to confidently confirm the detection of a gravitational wave.

Compensation for variables: Other factors, like varying pulsar timings, have to be accounted for, making the detection process more complex.

Requirement of long-term observations: Patience is key. It takes meticulous long-term observations and massive collaborative efforts to confidently detect these elusive waves.