{"id":294330,"date":"2025-10-01T12:22:25","date_gmt":"2025-10-01T02:22:25","guid":{"rendered":"https:\/\/science.nasa.gov\/solar-system\/skywatching\/night-sky-network\/octobers-night-sky-notes-lets-go-ligo\/"},"modified":"2025-10-01T12:22:25","modified_gmt":"2025-10-01T02:22:25","slug":"octobers-night-sky-notes-lets-go-ligo","status":"publish","type":"post","link":"https:\/\/www.vibewire.com.au\/?p=294330","title":{"rendered":"October\u2019s Night Sky Notes: Let\u2019s Go, LIGO!"},"content":{"rendered":"
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4 Min Read<\/div>\n

\n\t\t\t\t\t\t\t\tOctober\u2019s Night Sky Notes: Let\u2019s Go, LIGO!\t\t\t\t\t\t\t<\/h1>\n<\/p>\n<\/div>\n<\/div>\n
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\"An<\/figure>\n<\/p>\n<\/div>\n<\/div>\n<\/div>\n
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An artist\u2019s impression of gravitational waves generated by binary neutron stars.<\/figcaption><\/div>\n<\/p>\n<\/div>\n
\n\t\t\t\t\t\t\tCredits: <\/span>
\n\t\t\t\t\t\t\tR. Hurt\/Caltech-JPL<\/span>\n\t\t\t\t\t\t<\/div>\n<\/figcaption><\/div>\n<\/p>\n<\/div>\n<\/div>\n

by Kat Troche of the Astronomical Society of the Pacific<\/em><\/p>\n<\/p>\n

September 2025 marks ten years since the first direct detection of gravitational waves as predicted by Albert Einstein\u2019s 1916 theory of General Relativity. These invisible ripples in space were first directly detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO). Traveling at the speed of light (~186,000 miles per second), these waves stretch and squeeze the fabric of space itself, changing the distance between objects as they pass.<\/p>\n<\/p>\n

Waves In Space<\/h3>\n

Gravitational waves are created when massive objects accelerate in space, especially in violent events. LIGO detected the first gravitational waves<\/a> when two black holes, orbiting one another, finally merged, creating ripples in space-time. But these waves are not exclusive to black holes<\/a>. If a star were to go supernova, it could produce the same effect. Neutron stars can also create these waves for various reasons. While these waves are invisible to the human eye, this animation from NASA\u2019s Science Visualization Studio shows the merger of two black holes and the waves they create in the process.<\/p>\n

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\"Two<\/a><\/figure>
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Two black holes orbit each other, generating space-time ripples called gravitational waves in this animation. As the black holes get closer, the waves increase in until they merge completely.<\/div>\n
NASA\u2019s Goddard Space Flight Center Conceptual Image Lab<\/div>\n<\/figcaption><\/div>\n<\/div>\n<\/div>\n

How It Works<\/h3>\n

A gravitational wave observatory, like LIGO, is built with two tunnels, each approximately 2.5 miles long, arranged in an \u201cL\u201d shape. At the end of each tunnel, a highly polished 40 kg mirror (about 16 inches across) is mounted; this will reflect the laser beam that is sent from the observatory. A laser beam is sent from the observatory room and split into two, with equal parts traveling down each tunnel, bouncing off the mirrors at the end. When the beams return, they are recombined. If the arm lengths are perfectly equal, the light waves cancel out in just the right way, producing darkness at the detector. But if a gravitational wave passes, it slightly stretches one arm while squeezing the other, so the returning beams no longer cancel perfectly, creating a flicker of light that reveals the wave\u2019s presence.<\/p>\n

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\"Animation<\/a><\/figure>
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When a gravitational wave passes by Earth, it squeezes and stretches space. LIGO can detect this squeezing and stretching. Each LIGO observatory has two \u201carms\u201d that are each more than 2 miles (4 kilometers) long. A passing gravitational wave causes the length of the arms to change slightly. The observatory uses lasers, mirrors, and extremely sensitive instruments to detect these tiny changes.<\/div>\n
NASA<\/div>\n<\/figcaption><\/div>\n<\/div>\n<\/div>\n

The actual detection happens at the point of recombination, when even a minuscule stretching of one arm and squeezing of the other changes how long it takes the laser beams to return. This difference produces a measurable shift in the interference pattern. To be certain that the signal is real and not local noise, both LIGO observatories \u2014 one in Washington State (LIGO Hanford) and the other in Louisiana (LIGO Livingston) \u2014 must record the same pattern within milliseconds. When they do, it\u2019s confirmation of a gravitational wave rippling through Earth. We don\u2019t feel these waves as they pass through our planet, but we now have a method of detecting them!<\/p>\n<\/p>\n

Get Involved<\/h3>\n

With the help of two additional gravitational-wave observatories, VIRGO<\/a> and KAGRA<\/a>, there have been 300 black hole mergers detected in the past decade<\/a>; some of which are confirmed, while others await further study.<\/p>\n

While the average person may not have a laser interferometer lying around in the backyard, you can help with two projects geared toward detecting gravitational waves and the black holes that contribute to them:<\/p>\n