“The main property of the telescope is to enchant the world. The first time you will put your eyes and see a celestial object, it is a very different feeling, which cannot be compared with anything similar.” A night with a clear sky at the Aristotle University of Thessaloniki Observatory and the distance of 1.4 billion kilometers is annihilated. As Saturn with its rings approaches, the pupil of the eye dilates, trying to capture the unimaginable, and the childish question “but is it real?” it comes effortlessly from the lips of people of all ages. Next to Saturn, the moon of Titan, a small dot. A little later, the star Vega appears, which looks like a disco ball. And after an anxious wait Jupiter rises.

As the telescope moves to aim at a planet as it rises, the impressive iron dome also rotates, producing a noise reminiscent of surround sound technology in the night. Stories of collisions of US and Russian satellites in space, of avalanches of space “junk”, of asteroids that could fall on the head, give the evening elements of a science fiction film, where the participants in the stargazing become its protagonists.

The recently renovated AUTH Observatory organizes stargazing evenings open to the public, while welcoming schools every week where students can observe the Sun through a solar telescope with special filters. The professor of the Department of Astrophysics, Astronomy and Engineering of the Physics Department of AUTH, Nikos Stergioulasthe assistant professor of the same field Ioannis Golias and the Ph.D. candidate Alexander Siakas opened the dome of the Observatory at the Athens-Macedonian News Agency, to introduce the public to the fascinating world of planetary observation.

Ioannis-Hiou Seiradakis: The man who taught generations of astrophysicists

Guided tours of the AUTH Observatory are a tradition cultivated by the great astrophysicist Ioannis Seiradakiswho taught generations of astrophysicists – many of whom today excel in very important positions around the world – turning their research interest to astronomy. As a minimal sign of recognition of the contribution of the professor, who passed away in 2020 at the age of 72, at the entrance of the hall there is the inscription “THOLOS IOANNI-CHIOU SEIRADAKIS”.

“It is a tradition started by Mr. Seiradakis that students – undergraduates, postgraduates, PhDs – are trained to give guided tours. Essentially we try to create a flow, that is, the older students train the new ones with the same passion, do the tours and so there is always a small group, which is coordinated by the professors and our secretary, who does the planning of the tours and 2-3 schools come a week and visit us in the morning,” explained Mr. Siakas.

The tour usually begins by introducing the site and the historical elements of the telescope and dome. The building of the AUTH Observatory was completed in 1961, according to the plans of the architect Patroklos Karatinos. “The Observatory building is considered one of the architectural jewels of the university and the city. The telescope – dioptric, 20 cm – came from Paris in the 1950s and has been in operation ever since. Generations and generations of astronomers have been through this. Today we use it mainly for educational purposes”, said Mr. Stergioulas.

He noted that in recent years improvements have been made and a new wheel has been added to the telescope, which drives a motor, connecting the telescope to a computer, where there are programs to map the sky and the positions of the planets and it becomes possible to select a planet to observe. “If we want e.g. to see Saturn or Venus, we choose from the program and the telescope automatically rotates, finds the target. The automatic mechanism has been added and it is guided and not only finds the target, but also locks on there if we want to observe for a long time,” explained Mr. Stergioulas.

“The telescope is used in the astronomy course, in the fourth year, there are laboratory exercises. There is an evening workshop for the basic operation of the telescope and in a smaller solar telescope we have next to us we can observe the Sun during the day with the appropriate filters. There have been three graduate theses since the telescope was rebuilt, one of them had to do with asteroid observation, and seven asteroids were successfully recorded,” added Mr. Golias.

The field’s research activity spans the fields of Gravitational Wave Astronomy, Relativistic Astrophysics, Observational Cosmology, Theoretical Cosmology, Alternative Theories of Gravity, Optical Astronomy, Radio Astronomy, Astrochemistry and Exoplanet Atmospheres, as well as Exoplanetary Systems, of Asteroids, Space Mission Planning, Satellite Tracking and Communication, and Chaotic Dynamics.

Traffic in space and space “trash” threaten to take the form of an avalanche!

One of the important missions with which the AUTH team has been charged, concerns its participation in the space security program Space Situational Awareness (SSA). The network of AUTH astronomical stations currently consists of 3 wide-field telescopes (20 and 25 cm in diameter), 2 reflecting telescopes (25 and 35 cm in diameter), high-precision robotic supports, state-of-the-art astronomical cameras, weather stations, ceiling control systems, remote control systems and within 2025 the new 80cm diameter telescope in Holomontas of Halkidiki is expected to be fully operational (with funding from ESA and the Recovery Fund).

“Our stations mainly deal with problems of the near space environment. In other words, we are dealing with objects in the nearby solar system and not too far from Earth, which may create a problem”, said Mr. Golias, explaining that one parameter concerns asteroids and the possibility that “something will fall on our head”. while the other concerns space debris.

“Now with the traffic that exists in space, we have managed to pollute it quite a bit. There are currently close to 30,000 cataloged objects larger than 10 centimeters in orbit and entering the atmosphere. The problem is that the models we have for space debris populations show that the population will grow and may grow exponentially at some point. For what reason? Because if small 10 cm objects hit a large object, they can completely destroy a large satellite and create many thousands of other smaller objects, which in turn will hit something bigger. And let this continue like an avalanche phenomenon”, noted Mr. Golias. He also clarified that “space debris does not have a propulsion system, as from the moment a satellite completes its mission, it cleans its tanks, closes anything that can explode, batteries, etc. and stays there” and thus “active satellites maneuver systematically to avoid space debris”.

The maneuvers of the International Space Station and Elon Musk’s 2,000 satellites

The largest satellite today is International Space Station. It looks like a very bright star to the naked eye and is essentially a laboratory in space, the size of a football field and weighing 8,000 tons. Based on data from the last decade, the International Space Station is forced to make one or two maneuvers per year to avoid space debris.

“Consequently, the need for space surveillance, space debris cataloging has arisen, and this is the work our astronomical stations do […] When we are in low orbits – up to 2,000 kilometers from the Earth’s surface – the atmosphere helps and little by little the space debris loses altitude, until it finally burns up in the upper layers. This is the ultimate fate of all space debris in low orbit. Higher up there is no such possibility and that is where there is a research interest in what we are going to do, we need a design of various strategies that we can use for satellites in high orbits, which are at a distance of 20,000-36,000 kilometers from the surface of the Earth “, explained Mr. Golias.

Regarding the unfavorable scenario of triggering an avalanche from the collision of a large satellite with debris, Mr. Stergioulas clarified that the risk is “to destroy a large number of satellites and to essentially fill or surround the Earth with a cloud of “small debris” that to be dangerous to penetrate and that would not allow us to send a mission and stop the exploration of space.’ A scenario, which, as the three researchers agreed, is not only real, but at the moment seems inevitable, if appropriate measures are not taken.

The significant increase in the population of satellites has also contributed to space “traffic confusion” and the proliferation of space “junk”. “For a while we were stabilized a little near 2,500-3,000 thousand active satellites, but in the last 3-4 years, in the count of active satellites we see the explosion with the various large clusters of satellites that are going to carry satellite internet. Elon Musk currently has 2,000 satellites alone. The inactive are around 23,000-24,000. Usually the lifetime of satellites is in the order of 10-15 years”, noted the professor, while adding that in the direction of a more sustainable space policy, investments are already being made in satellites that use ion engines.

The US-Russia crash and the Chinese anti-satellite test

In the two years 2010-12 there were two major events, which created thousands of space debris. The first came from an anti-satellite test conducted by China to test its ability to destroy a satellite. “They sent a missile to destroy one of their own satellites. The problem is that they created …a lot of garbage. Close to 3,000 were the space debris created by this experiment and all of them are recorded with great precision. All of these have fallen, burned in the atmosphere after a decade,” noted Mr. Golias.

The second major event was a “crash” in space of the American Iridium telecommunications satellite and the decommissioned Russian Cosmos satellite. “At that time the inventory of space debris was not accurate enough. This is essentially part of the work we are doing now, that is to give measurements every night so that the orbits of the satellites are known with very high precision”, concluded Mr. Golias.