Scientific Horizons of Karazin University: A Dialogue with Astronomer Ivan Sliusarev on the Present of Space Exploration

Astronomy as a science not only opens infinite horizons of space but also allows us to understand our place in the Universe more deeply. Despite challenging circumstances, Ukrainian scientists, including Ivan Sliusarev, continue working on significant projects that contribute to the development of both national science and global astronomy.

Observing incredible cosmic phenomena, we increasingly realize that space is not only an object of study but also an inexhaustible source of inspiration.

Under clear night skies, astronomers can observe not only stars but also grand cosmic events. We share insights on upcoming astronomical events, new missions, and scientific achievements in an interview with Ivan Sliusarev, Associate Professor at the Department of Astronomy and Space Informatics at V. N. Karazin Kharkiv National University and a Ph.D. in Physics and Mathematics. What surprises await us in the starry skies this year? Where and when can extraordinary astronomical phenomena, particularly in Ukraine, be observed?

In October, comet Atlas was briefly visible to the naked eye. It could be seen in the western part of the sky shortly after sunset. In fact, the comet was visible to the naked eye in the last week of September in the southern hemisphere in the mornings and for about a week and a half after October 10 in the northern hemisphere in the evenings. In urban areas with street lighting, the visibility was even shorter.

As for solar activity, we are currently at the peak of the solar cycle and have been observing auroras for a year and a half, which have not been visible at our latitudes since the early 2000s during the previous peak. On the night of October 11, from Friday to Saturday, there was an extraordinarily bright aurora. It was the brightest and longest aurora observed here so far, covering almost half of the sky at its peak brightness. However, unfortunately, clear nights in late autumn and winter are rare, so we may not see all the auroras predicted for the future. According to forecasts, solar activity will begin to decline in the first half of 2026, so we still have chances to see auroras multiple times.

Auroras result from Earth's magnetosphere disturbances caused by the solar wind. These disturbances are primarily triggered by a sharp increase in solar wind speed from coronal holes on the Sun or direct plasma ejections from the Sun. Plasma particles, mainly electrons and protons, reach the upper atmosphere near the magnetic poles. As atoms in the atmosphere become ionized and excited, they emit light of various colors.

Red: At the highest altitudes, atomic oxygen excited by charged particles emits at a wavelength of 630 nm. Due to the low concentration of atoms and the human eye's lesser sensitivity at this wavelength, red auroras are visible only during intense solar activity, like the current one. Interestingly, phone CCD cameras are much more sensitive to red than the human eye, making auroras easier to photograph than to observe directly. The human eye often perceives auroras only as colorless glows in the north, and many might not even notice them without prior knowledge of what they are. Only during very bright events are colors visible.

Green: At lower altitudes, more frequent collisions suppress 630 nm emissions, as excited atoms release excess energy upon collision. Emission at 558 nm (green) becomes dominant. A higher concentration of atomic oxygen and the human eye's greater sensitivity to green make green auroras the most common. Excited molecular nitrogen also plays a role, transferring energy via collisions to oxygen atoms, which then emit it at the green wavelength. Red and green can mix to form pink or yellow hues. The rapid decrease in atomic oxygen concentration below approximately 100 km creates the sharp appearance of the auroras' lower edges, often forming structures called "curtains," the most common aurora form.

Tell us about the launch of two major missions to Jupiter's moon Europa and their prospects.

Two major spacecraft are currently en route to Jupiter's moons. The first is NASA's Europa Clipper mission, aimed at exploring the ocean beneath Europa's icy crust. This spacecraft will not only conduct detailed surface mapping but also investigate the atmosphere's composition and search for signs of life. Each scientific mission addresses a vast array of questions. The Europa Clipper is expected to reach its destination in 2030, with two gravitational maneuvers planned en route. It's worth noting that the mission is not orbital; the spacecraft will not orbit Europa directly but rather Jupiter. Its orbit is designed for over 40 close flybys of Europa to conduct its studies.

Additionally, the European JUICE mission to Jupiter's system was launched last year. While it started earlier, it will arrive later, around 2031. Planetologists eagerly await the results of both missions. Another intriguing mission, LUCY, is focused on studying Jupiter's Trojan asteroids. This mission will help us better understand the early stages of our Solar System's formation. These bodies may hold clues to how planets formed and migrated to their current orbits. According to current theories, the Trojans were captured from the outer regions of the protoplanetary disk, making them more similar to Kuiper Belt objects than typical silicate asteroids from the main belt.

What global issues and space research are Karazin astronomers focused on? What unites them?

Our Department of Asteroid Physics at the Research Institute of Astronomy is a scientific school for asteroid studies with a legacy of over four decades. I am part of the third generation raised in this department. We actively involve young researchers.

For instance, my Ph.D. student Valeriia Rychahova, now in her third year, works on processing data from space missions to the asteroids Ceres and Vesta. Another Ph.D. student, Ihor Kyrylenko, under the guidance of lead researcher Yurii Kruglyi, studies asteroid pairs. These are asteroids with close orbits and likely common origins. In recent years, Ihor has discovered several dozen new asteroid pairs, approximately 15% of all known such systems.

Our team also conducts extensive research on near-Earth asteroids, focusing on their photometric observations, led by Yurii Kruglyi. Iryna Belskaya, head of the department, and Vasyl Shevchenko have significant expertise in studying the phase dependencies of asteroid polarization and brightness, correlating these parameters with other physical properties. Our department has been a global leader in this field for over 30 years, conducting these studies continuously. Iryna has also extensively researched Trans-Neptunian Objects (TNOs), exploring their polarimetry, spectrophotometry, and spectral-polarimetry.

Oleksii Holubov, a young Doctor of Science, has advanced the theory of the YORP effect, discovering an additional component of this non-gravitational effect that accelerates or decelerates asteroid axial rotation.

What are your current projects, and how are they tied to pre-war research? What publications are you preparing?

Before the war, we were actively working on a grant from the National Research Foundation of Ukraine, focused on identifying metallic asteroids. However, funding ceased at the war's onset. This year, we managed to recover part of the funds and are now completing the project under tighter budgets and deadlines. Currently, we are in the final stages of writing a monograph summarizing the project's findings and our team's collective work. Dedicated to the physical properties and dynamic evolution of asteroids, this monograph will be presented to the University Academic Council this month. It compiles modern knowledge about asteroids, our research findings, and results from the National Research Foundation project. This will be the first contemporary Ukrainian-language book dedicated exclusively to asteroids. We hope it finds its audience among students, future colleagues, astronomy enthusiasts, and anyone interested in astronomy. Thankfully, astronomy is still taught in schools.