A team of astronomers led by researchers from the University of Birmingham, University College London and Queen’s University Belfast have discovered one of the most dramatic ‘switches on’ of a black hole ever seen. They will present their findings on Tuesday 4 July at the 2023 National Astronomy Meeting in Cardiff. The work will also be published in Monthly Notices of the Royal Astronomical Society.

J221951-484240, known as J221951, is one of the most luminous transients—astrophysical objects that change their brightness over a short period of time—ever recorded. It was discovered by Dr. Samantha Oates, an astronomer at the University of Birmingham, and her team, in September 2019 while searching for the electromagnetic light from a gravitational wave event. The team were using the Ultra-Violet and Optical Telescope on board the Neil Gehrels Swift Observatory to look for a kilonova, the sign of a neutron star merging with another neutron star or a black hole. A kilonova typically appears blue, then fades and turns more red in color over a timescale of days. What they found instead something even more unusual: J221951. The transient appeared blue, but didn’t change color or fade rapidly as a kilonova would.

Multiple telescopes were used to follow-up J221951 and determine its nature, including NASA’s Swift/UVOT and Hubble Space Telescope, the South African Large Telescope, and ESO facilities such as the Very Large Telescope and the GROND instrument on the MPG/ESO 2.2-meter telescope at the La Silla Observatory.

Scientists have for the first time observed the early universe running in extreme slow motion, unlocking one of the mysteries of Einstein’s expanding universe. The research is published in Nature Astronomy.

Einstein’s general theory of relativity means that we should observe the distant—and hence ancient— universe running much slower than the present day. However, peering back that far in time has proven elusive. Scientists have now cracked that mystery by using quasars as “clocks.”

“Looking back to a time when the universe was just over a billion years old, we see time appearing to flow five times slower,” said lead author of the study, Professor Geraint Lewis from the School of Physics and Sydney Institute for Astronomy at the University of Sydney.

This thrum of gravitational waves is constantly pulsing through the universe. It opens a window into the earliest moments after the Big Bang.

Albert Einstein proposed in 1916 that the universe was constantly being pushed and stretched by space-time waves undulating throughout the universe. A group of scientists won the Nobel Prize for finding proof of these waves in 2016, using a laser interferometer to detect a high-frequency gravitational wave emanating from the collision of two black holes or neutron stars less than 100 times the mass of the sun.

Geoff Bennett:

Let’s expand our horizons a bit wider and look at important findings that are literally about space-time and the cosmos as we know it.

You might remember that Albert Einstein theorized that as heavy objects move through time and space, they create ripple effects in the fabric of our universe. Now an international team of scientists have detected new evidence of that. Researchers found new signs of gravitational waves, waves that are affected by huge movements, such as the collision of black holes.

Since the discovery of gravitational waves, scientists have been trying to understand the origin of merging black holes, and POSYDON may be the way to do it.

Black holes are some of the most fascinating celestial bodies in the universe. Their gravitational fields are so strong that even light cannot escape them. One of the ways in which they are formed is when a massive star collapses, resulting in a stellar-mass black hole.

In 2015, the Laser Interferometer Gravitational-wave Observatory (LIGO) discovered gravitational waves (ripples through spacetime) from two colliding black holes. This groundbreaking discovery has prompted astrophysicists to study their origin and formation.

For the first time, researchers using pulsar timing arrays have found evidence for the long-sought-after gravitational wave background. Though the exact source of this low-frequency gravitational wave hum is not yet known, further observations may reveal it to be from pairs of supermassive black holes orbiting one another or from entirely new physics at work in our universe.

A New Window onto Gravitational Waves

In 2016, researchers reported the first detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO), opening a new window onto a universe’s worth of collisions between extreme objects like black holes and neutron stars. Though this discovery marked the beginning of a new observational era, many sources of gravitational waves remained beyond the reach of our current detectors on Earth.