What Could a Next Generation Event Horizon Telescope Do?

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).

There is no doubt that our understanding of the processes within our Universe have come on leaps and bounds since the invention of the telescope. The resolution of these space piercing instruments is dictated by the telescope’s aperture. The technique known as interferometry hooks individual telescopes together and combines their signal so they act as one BIG telescope, boosting the resolution. 

Telescopes like the EHT have been using interferometry to great advantage to study black holes. These enigmatic and mysterious stellar corpses defy our probing; we do not fully understand their origins and processes and indeed our laws of physics break down if you get too close to the point source in the centre, the singularity. Due to their interaction with space and time, understanding the full nature of black holes will – hopefully – unlock our understanding of the Universe. 

Previously, observations have only revealed the movement of stars around galactic centre suggesting an object was lurking there weighing in at around 4 million times the mass of the Sun. Data from the EHT collected during 2022, finally revealed an image of the object at the centre – SgrA* – a super massive black hole and the matter in the immediate vicinity of the event horizon. Whilst this image did not reveal the black hole itself – another article required to explain that – it certainly revealed the telltale signs. 

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

A recently published paper explores the possibilities of the ngEHT and how they might be able to unpick some of the physics around black holes. The ngEHT will increase the geographical footprint of EHT by 10 further instruments that span across the Earth.  Making use of the significant improvement in resolution, the ngEHT will also improve image dynamics range, provide a multi-wavelength capability and facilitate long term monitoring. 

The team conclude that future enhancements in measurement sensitivity and data analysis techniques in ngEHT will substantially advance our understanding of black holes and the immediate environments surrounding them with particular focus on the photon ring, mass and spin analysis, binary supermassive black holes and more besides. 

Source : Fundamental Physics Opportunities with the Next-Generation Event Horizon Telescope

One Reply to “What Could a Next Generation Event Horizon Telescope Do?”

  1. There is a lot of other physics that they hope ngEHT will probe. But regarding the photon rings, this seems central:

    “Actual observables are likely, by virtue of being luminous, the low-order images, i.e., primary, secondary, and
    tertiary images, corresponding to the n = 0, 1, and 2 photon rings in Broderick et al. (2022) and Johnson et al. (2020). The relative locations of the lensed images at different orders depend on mass and spin, enabling a measurement of both. Because this remains true even for polar observers, observing the secondary presents a unique pathway to measuring spins in M87* and Sgr A*.”

    “Thus, N × SNR ? 140 is needed to eventually achieve the sub-1 µas precision needed to resolve the n = 1 photon ring width in a single observation.

    A single measurement of the diameter of the n = 1 photon ring alone would provide a mass measurement that has a bounded systematic uncertainty. For equatorial emission seen by a polar observer, the diameter of the n = 1 photon ring ranges from 4.30 M/D to 6.17 M/D as the radius of the peak emission moves from the horizon to infinity (Broderick et al., 2022), where D is the source distance. Thus, the conclusive detection of a photon ring necessarily eliminates the current dominant systematic uncertainty for mass estimates of M87*.

    The differing behavior of the primary and secondary image dependence on the emission location provides a means to probe spin.”

Comments are closed.