ETH captures image of a quasar 7.5 billion light-years from Earth
A team of scientists created images of the NRAO 530 quasar using data from the Event Horizon Telescope (EHT), according to Phys.org.
The EHT, a worldwide network of radio telescopes whose images are combined to make groundbreaking observations, was famously used to capture the first-ever image of a black hole.
Now, the project has shed new light on quasars, which are believed to be powered by black holes. They are some of the most mysterious objects in the universe and provide a window into the ancient universe.
A new image of a quasar 7.5 billion light-years away
Quasars are a type of galactic nuclei that typically has a mass of millions or even billions of solar masses. Scientists believe they are powered by supermassive black holes, and they are detected due to the heat they emit as the cosmic giants interact with their surroundings.
In a new study, a team of astronomers and astrophysicists outline how they studied data from ETH. They specifically compiled data collected by other researchers on the ETH program dating back to 2017.
Some of that data was originally used to calibrate the ETH program's observations of Sagittarius A*, the black hole at the center of the Milky Way galaxy. The NRAO 530 quasar images were particularly challenging due to the space giant's distance from Earth — NRAO 530 is located approximately 7.5 billion light-years away.
Capturing a quasar
According to the scientists, the new image shows that the NRAO 530 quasar is optically violent, and it is also a blazar — a type of quasar that emits powerful high-speed plasma jets almost exactly in the direction of Earth.
The researchers combined data from multiple telescopes to create two images. Both of these show brightness at the southern end of one of these jets, which the scientists believe to be a radio core.
The ETH data allowed for very high-enough images, meaning the scientists were able to detect two different components of that radio core in the images. They were also able to calculate the polarization of the light — the preferred orientation of the light waves — from different sections of the quasar. Finally, they were also able to map the magnetic fields in the powerful jets emitted by the colossal space giant.
Quasars are high on the list of the oldest, brightest, and most distant objects astronomers have ever observed. The reason we can observe them over such massive distances is due to the fact they can outshine the galaxies they exist in or even burn brighter than one trillion stars combined. There is a lot we don't understand about quasars, but images such as the new capture from the ETH data could help to shed new light on the role they play in the cosmos.
The study was published in The Astrophysical Journal.
We report on the observations of the quasar NRAO 530 with the Event Horizon Telescope (EHT) on 2017 April 5−7, when NRAO 530 was used as a calibrator for the EHT observations of Sagittarius A*. At z = 0.902, this is the most distant object imaged by the EHT so far. We reconstruct the first images of the source at 230 GHz, at an unprecedented angular resolution of ∼20 μas, both in total intensity and in linear polarization (LP). We do not detect source variability, allowing us to represent the whole data set with static images. The images reveal a bright feature located on the southern end of the jet, which we associate with the core. The feature is linearly polarized, with a fractional polarization of ∼5%–8%, and it has a substructure consisting of two components. Their observed brightness temperature suggests that the energy density of the jet is dominated by the magnetic field. The jet extends over 60 μas along a position angle ∼ −28°. It includes two features with orthogonal directions of polarization (electric vector position angle), parallel and perpendicular to the jet axis, consistent with a helical structure of the magnetic field in the jet. The outermost feature has a particularly high degree of LP, suggestive of a nearly uniform magnetic field. Future EHT observations will probe the variability of the jet structure on microarcsecond scales, while simultaneous multiwavelength monitoring will provide insight into the high-energy emission origin.
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