Sagittarius A* Archives

July 23, 2024July 23, 2024 by Mark Thompson

Next Generation Event Horizon Telescope To Unlock Mysteries of Black Holes

Impact of scattering on the observed polarimetric spiral phase from one 345 GHz frame of the GRMHD simulation of Sgr A*

The prospect of actually resolving the event horizon of black holes feels like the stuff of science fiction yet it is a reality. Already the Event Horizon Telescope (EHT) has resolved the horizon of the black holes at the centre of the Milky Way and M87. A team of astronomers are now looking to the next generation of the EHT which will work at multiple frequencies with more telescopes than EHT. A new paper suggests it may even be possible to capture the ring where light goes into orbit around the black hole at the centre of the Milky Way.

March 27, 2024March 27, 2024 by Alan Boyle

New View Reveals Magnetic Fields Around Our Galaxy’s Giant Black Hole

An image from the Event Horizon Telescope shows lines of polarization, a signature of magnetic fields, around the shadow of the Milky Way's central supermassive black hole. Astronomers want to know how massive black holes like this one formed early in cosmic history. (Credit: EHT Collaboration)

Fresh imagery from the Event Horizon Telescope traces the lines of powerful magnetic fields spiraling out from the edge of the supermassive black hole at the center of our Milky Way galaxy, and suggests that strong magnetism may be common to all supermassive black holes.

December 9, 2023December 9, 2023 by Mark Thompson

What Could a Next Generation Event Horizon Telescope Do?

Image of the M87 black hole by EHT and a CGI image photon ring. Image credit: EHT, Center for Astrophysics | Harvard & Smithsonian

Telescopes have come a long way in a little over four hundred years! It was 1608 that Dutch spectacle maker Hans Lippershey who was said to be working with a case of myopia and, in working with lenses discovered the magnifying powers if arranged in certain configurations. Now, centuries on and we have many different telescope designs and even telescopes in orbit but none are more incredible than the Event Horizon Telescope (EHT). Images las year revealed the supermassive black hole at the centre of our Galaxy and around M87 but now a team of astronomers have explored the potential of an even more powerful system the Next Generation EHT (ngEHT).

September 2, 2023September 2, 2023 by Brian Koberlein

Astronomers are Hoping the Event Horizon Telescope saw Pulsars Near the Milky Way's Supermassive Black Hole

Visualization of a fast-rotating pulsar. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab

Millisecond pulsars are amazing astronomical tools. They are fast-rotating neutron stars that sweep beams of radio energy from their magnetic poles, and when they are aligned just right we see them as rapidly flashing radio beacons. They flash with such regularity that we can treat them as cosmic clocks. Any change in their motion can be measured with extreme precision. Astronomers have used millisecond pulsars to measure their orbital decay due to gravitational waves and to observe the background gravitational rumblings of the universe. They have even been proposed as a method of celestial navigation. They may soon also be able to test the most fundamental nature of gravity.

August 3, 2023August 3, 2023 by Brian Koberlein

Does the Milky Way's Supermassive Black Hole Have a Companion?

Sag A* compared to M87* and the orbit of Mercury. Credit: EHT collaboration

At the heart of our galaxy, there is a monster black hole. Known as Sagittarius A*, it has a mass of 4.2 million Suns, and it’s only about 27,000 light-years from Earth. Sag A* is the closest supermassive black hole, and one of only two that we’ve observed directly. It is so close that we can even see stars closely orbiting it. Some of those stars we’ve been observing for more than 20 years, which means we have a very good handle on their orbits. We’ve used those orbits to determine the mass of Sag A*, but a new study looks at a different question: does our galaxy’s black hole have a companion?

March 23, 2023March 23, 2023 by Matt Williams

Hypervelocity Stars Teach us About Black Holes and Supernovae

An artist's conception of a hypervelocity star that has escaped the Milky Way. Credit: NASA

Hypervelocity stars (HVS) certainly live up to their name, traveling thousands of kilometers per second or a fraction of the speed of light (relativistic speeds). These speed demons are thought to be the result of galactic or black hole mergers, globular clusters kicking out members, or binary pairs where one star is kicked out when the other goes supernova. Occasionally, these stars are fast enough to escape our galaxy and (in some cases) take their planetary systems along for the ride. This could have drastic implications for our theories of how life could be distributed throughout the cosmos (aka. panspermia theory).

There are thousands of these stars in our galaxy, and tracking them has become the task of cutting-edge astrometry missions (like the ESA’s Gaia Observatory). In previous research, astronomers suggested that these stars could be used to determine the mass of the Milky Way. In a recent study from Leiden University in the Netherlands, Ph.D. candidate Fraser Evans showed how data on HVS could be used to probe the mysteries of the most extreme objects in our Universe – supermassive black holes (SMBHs) and the violent supernovae of massive stars.

March 7, 2023March 7, 2023 by Matt Williams

A Tadpole-Shaped Cloud of Gas is Whirling Around a Black Hole

Artist’s Impression of the “Tadpole” Molecular Cloud and the black hole at the gravitational center of its orbit. Credit: Keio University

In the 1930s, astrophysicists theorized that at the end of their life cycle, particularly massive stars would collapse, leaving behind remnants of infinite mass and density. As a proposed resolution to Einstein’s field equations (for his Theory of General Relativity), these objects came to be known as “black holes” because nothing (even light) could escape them. By the 1960s, astronomers began to infer the existence of these objects based on the observable effects they have on neighboring objects and their surrounding environment.

Despite improvements in instruments and interferometry (which led to the first images of M87 and Sagittarius A*), the study of black holes still relies on indirect methods. In a recent study, a team of Japanese researchers identified an unusual cloud of gas that appears to have been elongated by a massive, compact object that it orbits. Since there are no massive stars in its vicinity, they theorize that the cloud (nicknamed the “Tadpole” because of its shape) orbits a black hole roughly 27,000 light-years away in the constellation Sagittarius.

March 2, 2023March 2, 2023 by Matt Williams

A Very Young Star is Forming Near the Milky Way's Supermassive Black Hole

Artist's impression of a young, massive star orbiting Sagittarius A*. Credit: University of Cologne

Since the 1930s, physicists and radio engineer Karl Jansky reported discovering a persistent radio source coming from the center of our galaxy. This source came to be known as Sagittarius A* (Sgr A*), and by the 1970s, astronomers determined that it was a supermassive black hole (SMBH) roughly four million times the mass of our Sun. Since then, astronomers have used increasingly-advanced radio telescopes to study Sgr A* and its surrounding environment. This has led to many exotic discoveries, such as the many “Stars stars” and gaseous “G objects” that orbit it.

The study of these objects and how the powerful gravity of Sgr A* has allowed scientists to test the laws of physics under the most extreme conditions. In a recent study, an international team of researchers led by the University of Cologne made a startling discovery. Based on data collected by multiple observatories, they observed what appears to be a newly-formed star (X3a) in the vicinity of Sgr A*. This discovery raises significant questions about how young stellar objects (YSOs) can form and survive so close to an SMBH, where they should be torn apart by violent gravitational forces.

March 2, 2023March 2, 2023 by Matt Williams

A Mysterious Blob Near the Milky Way’s Supermassive Black Hole Might Finally Have an Explanation

Orbits of stars near Sagittarius A*. Credit: ESO/M. Parsa/L. Calçada

At the center of the Milky Way, there is a massive persistent radio source known as Sagittarius A*. Since the 1970s, astronomers have known that this source is a supermassive black hole (SMBH) roughly 4 million times the mass of our Sun. Thanks to advancements in optics, spectrometers, and interferometry, astronomers have been able to peer into Galactic Center. In addition, thanks to the international consortium known as the Event Horizon Telescope (EHT), the world got to see the first image of Sagittarius A* (Sgr A*) in May 2022.

These efforts have allowed astronomers and astrophysicists to characterize the environment at the center of our galaxy and see how the laws of physics work under the most extreme conditions. For instance, scientists have been observing a mysterious elongated object around the Sgr A* (named X7) and wondered what it was. In a new study based on two decades’ worth of data, an international team of astronomers with the UCLA Galactic Center Group (GCG) and the Keck Observatory have proposed that it could be a debris cloud created by a stellar collision.

February 20, 2022February 20, 2022 by Matthew Cimone

Imaging the Galaxy’s Centre in Unprecedented Detail Reveals More Mysterious Filaments

Milky Way centre by the MeerKAT array of 65 radio dishes in South Africa. Credit: SAROA

The inner 600 light years of our galaxy is a maelstrom of cosmic radiation, turbulent swirling gas clouds, intense star formation, supernovae, huge bubbles of radio energy, and of course a giant supermassive black hole. This bustling downtown of the Milky Way is a potential treasure trove of discovery but has been difficult to study as the galaxy’s central regions are obscured by dust and glaring radiation. But a new image of this region with unprecedented detail reveals more than we’ve ever seen before. We find some familiar objects like supernovae but also some mysterious structures – gaseous filaments dozens of light years long channeling electrons at near light speed.

Behold, the galaxy’s centre as never seen before: