Observing the sky – Valerii Larionov on today’s projects in astrophysics

Valerii Larionov, a chief research associate at the Department of Astrophysics, describes the research projects in astrophysics that are under way at the University and why having the University’s own observatory is crucial.

In 2019, our scientists, as part of the Event Horizon Telescope collaboration, were behind a project to capture the first ever image of a black hole. What are the projects underway in your laboratory now?

The supermassive black hole, as we know today, will be somewhere at any galaxy’s centre. Some of the galaxies – quasars and blazars – are the most powerful sources of emission across the electromagnetic spectrum, from γ-ray to radio wavelengths. A colossal jet of excited gas, or plasma, screams away from the centre of the black hole at nearly the speed of light. The power of the jet is larger than the luminosity of all the stars in a galaxy. For the last fifty years, we improved our research methods, developed a series of models to delve into the active galactic nuclei in different bands. Yet few models, if any, can help us better understand the physics that drives the behaviour of these objects. Little is known about what part of the jet is associated with the optical outburst or gamma-ray outburst. Outburst patterns, often rapid and dramatic fluctuations in brightness on short timescales, are far from being understood.

Our laboratory has long been monitoring active galactic nuclei in different bands of the optical spectrum and in polarimetry mode. Photometry and polarimetry variability, as we see, is in large part due to the spiral structure of the jet or magnetic field. We have held a number of international campaigns to observe blazars and published our results in the world’s leading journals.

Does the University have a long-term programme for observation?

We have a list of the priority objects we regularly monitor regardless whether they are bright or weak. There is a number of reasons behind why we have chosen these objects. First, some of them have been observed and monitored at the University for over 50 years. Now we have enough evidence to track their evolution over a long period of time. Second, some objects are important as they are active from γ-rays to radio wavelengths.

You can find an up-to-date list of the objects on the web-site of the Virtual Observatory of the University. It provides detailed information about names, links to NASA database, galactic coordinate systems, and curves of luminosity changes after each observation session. This information is essential for us as well. We can see whether there are some changes that are well worth our attention and we should observe it more precisely. The data is also useful for our fellow scientists across the globe, including those who investigate these objects in gamma-rays. It is not easy to identify the most ‘interesting’ objects as they are likely to change at any time.

In September and October 2020, BL Lac showed luminous emissions and rapid, high amplitude variability. For the last 20 years, there has been an unprecedented brightening of blazar accompanied by quasi-periodic oscillations in the light curves depending on the time of day. It is in the optical spectrum.  What happens in other parts of the spectrum is unknown.

In 2016, after several years of quiescence, the blazar CTA 102 underwent an exceptional optical and high-energy outburst. There are a number of different opinions that explain the event. Some of the scientists attribute this to changes in the Doppler factor. The spectrum may move to higher frequencies owing to an increased Doppler shift as the viewing angle decreases during the outburst stage. Perhaps, its gravity shredded a star that got too close.

Are optical observations important nowadays? What is the object of such observations?

The optical spectrum is the portion of the electromagnetic spectrum that is visible to the human eye. Therefore, optical receivers had become highly sensitive long before we could analyse quantum phenomena in astrophysics: gamma-rays, x-rays, infrared radiation, and radio waves. Yet observations in these wavelengths are as important as in others.

There might be a feeling of unrest due to vagueness and ambiguity in our terminology. The words ‘optical’ and ‘visible’ were used as synonyms. The situation is different now. The concept ‘optical’ is associated with the portion of the electromagnetic spectrum that is visible to the human eye, while the concept ‘visible’ is about what we can see with binoculars, telescopes, spyglasses. Therefore, all quantitative assessment is rough, and the method of visual observation is outdated. Now we have plates, photoelectric amplifiers, electronic image converters... The most popular device to detect light in the optical spectrum is a charge-coupled device. The technology is widely used in CCD video cameras.

What equipment and resources are available to you now?  Is this infrastructure available to students?

The University has only one telescope which is equipped with the photometer-polarimeter which was developed in our Laboratory. We teach our students how to use the telescope and analyse obtained data. Some of them, who are majoring in observational astrophysics, use the obtained data in preparing their term and graduation projects. There is, and I hope there will be, a number of dissertations based on the telescopic observations.

Do you have access to the research facilities and resources abroad?

We regularly collaborate with observatories in Russia and across the globe. In some cases, we work under long-term agreements on collaboration, for example, with the Crimea Astrophysical Observatory. More often than not, our collaboration is about observing specific objects. Due to the rotation of the Earth, the objects move across the sky in different parts of our globe at a certain time. What we observe at a certain period of time is then investigated by our colleagues in Italy, Spain, the Canary Islands, Japan, Taiwan, China, Uzbekistan… We also work with the space telescopes in x-rays and gamma-rays. It is normal practice in astronomy today.

What encourages students to apply to study astronomy and engage in research?

The question is both difficult and easy to answer. Most of our students are astronomy enthusiasts and those who took part in the Olympiads. Few will become experts. Yet they are truly persistent in their urge to delve into the Universe.

The Department of Astronomy was opened in 1819. Yet the University’s Observatory was built only in 1888. Before, scientists and students worked in the Academic Observatory in the Kunstkamera.  Why is having its own Observatory important for the University?

It is obvious. Take any university abroad. There is a telescope in each of them. It enables students to engage in observations. Astronomy is good not only for mathematicians and physicists, but also for students in humanities to get a rough idea of how the Universe works.

The University’s Observatory was initially located in the First Pavlov Military School, while the Observatory of the Bestuzhev Courses was opened in the 10^th Line in 1896. Today, observing the sky within the city is difficult due to light pollution. Do you expect a new Observatory to be built in the new campus of the University? What will it be like?

You can find a chronicle of the University’s astronomy here.

Light pollution is a curse of our day for astronomy. Few students have seen the Milky Way with a naked eye. Before the 1990s, the University used to have its own observatory in Byurokan, Armenia. There was no sign of light pollution due to the efforts of academician Viktor Ambartsumian, who was the Director of the Observatory and founded the Department of Astrophysics at the University. Night lighting was minimal.

Today, telescopes might be repeatedly neglected in research, even by scientific administrators as we have ample access to the Internet resources. Yet who is supposed to upload this information on the Internet? Can you achieve outstanding results in astronomy without being able to obtain, process and analyse collected data? Astronomy is a science of how you see the world. Any university should have at least a 1-metre telescope that would be available to both academic experts and students, including in humanities. It should be located in a place where light pollution is minimal. It is rather costly as you need to have state-of-the-art receivers. It should be installed in a separate building to minimise the effect of vibration. The building should have a rotating dome to move synchronously with a telescope.  A new observatory is expected to be built in the new campus. If this happens, we stand every chance of keeping alive our century-long traditions in astronomy.