Total lunar eclipse

by Florentina Pîslan, PhD student

12.09.2025

On the night of September 7–8, 2025, the longest total lunar eclipse in recent decades took place. More precisely, the phenomenon lasted 82 minutes and could be observed by about 85% of the world’s population, including from Romania!

Credit imagine: Maximilian Teodorescu, cercetător la Institutul de Științe Spațiale - filiala INFLPR

A total lunar eclipse occurs when, during its orbit around Earth, the Moon passes behind the planet, causing Earth to completely shadow it. The only light that still reaches the Moon is that which first passes through Earth’s atmosphere, which filters the wavelengths of sunlight. As a result, only the longer wavelengths, such as red and orange, reach the Moon’s surface, while the shorter wavelengths, such as blue and violet, scatter more easily and do not reach it. Consequently, during a total eclipse, the Moon appears reddish, which is why it is often called a ‘Blood Moon.’

Sursă imagine: NASA Goddard Space Flight Center/Scientific Visualization Studio

The RAMSES Mission brings a possible collaboration between ESA and JAXA

29.08.2025

by Florin-Ioan Constantin, Ph.D. student

source: https://www.esa.int/Space_Safety/Planetary_Defence/Ramses_ESA_s_mission_to_asteroid_Apophis

This week, the European Space Agency (ESA) announced the intention of the Japanese Space Agency (JAXA) to collaborate with ESA on the RAMSES mission (Rapid Apophis Mission for Space Safety).

The asteroid Apophis has a diameter of approximately 375 meters and was discovered in 2004. On April 13, 2029, it will pass close to our planet at a distance of about 32,000 kilometers, allowing us to see it with the naked eye for a short time from Europe, Africa, and parts of Asia during its passage.

The RAMSES mission aims to intercept asteroid Apophis during its 2029 flyby of Earth in order to study its properties as it comes under the influence of our planet’s gravitational pull. The proposal for this mission is scheduled to be reviewed by ESA in November 2025, and if approved, it will launch in 2028 to rendezvous with the asteroid before it enters Earth’s gravitational field. Scientists expect our planet’s gravity to alter the way the asteroid spins as it travels, which could in turn trigger quakes and landslides on its surface. Thus, RAMSES will provide critical information about the asteroid’s condition before these additional gravitational influences, about their direct effects, and about the final outcome and long-term consequences that may result.

This mission also builds on and refines part of the technology and scientific developments that led to the adoption and launch of another similar mission, HERA, which was launched in 2024 and is currently en route to the asteroid Dimorphos, part of the Didymos binary asteroid system.

Sources and further reading:

https://www.esa.int/Space_Safety/Planetary_Defence/ESA_and_JAXA_advance_potential_Apophis_mission_collaboration

https://www.esa.int/Space_Safety/Planetary_Defence/Ramses_ESA_s_mission_to_asteroid_Apophis

https://www.reuters.com/business/aerospace-defense/japan-provide-h3-rocket-europes-mission-observe-apophis-asteroid-2025-08-22/

Ultramassive Black Hole pushes the boundaries of Physics

26.08.2025

by George Cristache, PhD student

Horseshoe galaxy

Ultramassive black holes are true cosmic giants, with masses on the order of tens of billions of solar masses. Like any self-respecting supermassive black hole, they reside at the centers of galaxies (far more massive than the Milky Way) and act both as a galactic anchor and as a “cosmic furnace.” Through the dynamics of the accretion disk, they regulate the pace, rate, and number of stars that will form within the host galaxy.

But why should we study ultramassive black holes? Aren’t they simply heavier versions of supermassive black holes? In fact, the transition from “supermassive” to “ultramassive” challenges our current models of black hole formation, with profound implications for galaxy dynamics and evolution. A striking example was recently identified in the binary galaxy system known as the Cosmic Horseshoe, investigated by Carlos Melo-Carneiro and collaborators. The massive galaxy at the center of the image warps the fabric of spacetime, bending the light of its lighter companion galaxy and producing an optical illusion in which the latter appears shaped like a horseshoe. This gravitational lensing effect provides an indirect method of estimating the mass of a black hole, though it typically allows for significant uncertainties. To improve precision, Melo-Carneiro and his team complemented this method with spectroscopic measurements obtained using images from the Hubble Space Telescope, ultimately arriving at a remarkable mass determination: 36 billion solar masses.

Current theoretical estimates suggest that the upper limit for a black hole’s mass is around 50 billion solar masses. This limit arises because, as a black hole accretes matter, the infalling material forms a gaseous envelope in the form of an accretion disk. When accretion occurs rapidly, particles within the disk are heated and emit radiation. The resulting radiation pressure counteracts the intense gravitational pull, thereby imposing a limit on how quickly and how much matter a black hole can absorb.

Of course, the quasar TON 618 was initially estimated to harbor a black hole of 66 billion solar masses, but more refined measurements of stellar dynamics around it have reduced that estimate to less than 40 billion solar masses.

On one hand, the extreme mass of the black hole in the Cosmic Horseshoe system can be explained by the fact that it is a “fossil galaxy”, formed through the successive mergers of galaxies within a cluster, and therefore through the merging of their central black holes. On the other hand, the ratio between the black hole’s mass and that of its host galaxy is about 1.5 times higher than the average expected for such binary systems. A conventional explanation is that, during the parent cluster’s black hole mergers, the high-energy interactions ejected a large amount of matter from the system. Yet researchers do not rule out the possibility that the evolution of ultramassive black holes involves still-unknown mechanisms.

Thus, by studying these ultramassive black holes, we may be able to shed light on the mysteries surrounding the origin and evolution of these extraordinary cosmic entities.

Source:   https://doi.org/10.1093/mnras/staf1036 

Interstellar Visitors

01.08.2025

by dr. Ana Caramete, PhD

Interstellar Comet 3I/ATLAS captured by the Gemini North telescope, funded by the NSF. The image shows the comet’s compact coma, a cloud of gas and dust surrounding its icy nucleus

For only the third time in the history of modern astronomy, a celestial object originating from outside our solar system has been observed. The newly identified object, officially designated 3I/ATLAS, was discovered on July 1, 2025, by the Asteroid Terrestrial-impact Last Alert System (ATLAS) telescope network. It was recorded traveling towards the Sun at a velocity exceeding 210,000 km/h. Its trajectory is highly hyperbolic (open), indicating that it is not gravitationally bound to the Sun. This orbital characteristic confirms that the object is of interstellar origin. Prior to this discovery, only two interstellar visitors had been confirmed: the object 1I/2017 U1 (‘Oumuamua) in 2017 and 2I/Borisov in 2019. However, many others may have passed through the solar system undetected. With an estimated diameter of approximately 11 km, 3I/ATLAS is by far the largest interstellar object ever observed.

The first known interstellar traveller, ‘Oumuamua, posed a significant mystery. Discovered in October 2017 as a faint point of light (after it had already passed perihelion) it proved difficult to characterize. It was relatively small (a few hundred meters across) and did not exhibit a typical cometary tail or detectable gas emissions. Nonetheless, it displayed non-gravitational acceleration, suggesting that it was being pushed by an unknown force. Because it was only detected during its outbound trajectory, limited observational data were available, leading to exotic hypotheses about its nature, including speculation that it might be an extra-terrestrial probe or spacecraft. While this idea remains highly controversial, the scientific consensus is that ‘Oumuamua was most likely a peculiar natural object, possibly a thin, icy fragment undergoing unusual mass loss or a low-activity comet with undetectable outgassing.

In contrast, the second interstellar object, 2I/Borisov, observed in 2019, exhibited behaviour and morphology consistent with that of a typical comet. Shortly after being discovered by amateur astronomer Gennady Borisov from Crimea, the object was observed with a distinct coma and tail, similar to comets from our own solar system. The solid nucleus was estimated to be about 1 km in diameter and was surrounded by gas and dust, confirming its cometary nature. 2I/Borisov provided the first robust evidence that not all interstellar objects are anomalous, some being just ordinary bodies, likely ejected from other stellar systems.

The third interstellar visitor, comet 3I/ATLAS, is significantly larger and faster, with a glacial nucleus of approximately 11 km in diameter and a current speed of 245,000 km/h, making it the fastest object ever detected in our solar system. Unlike ‘Oumuamua, 3I/ATLAS was detected during its inbound trajectory toward the inner solar system, allowing astronomers a longer observational window. Within days of discovery, multiple observatories reported the presence of a growing coma and a short tail, confirming that 3I/ATLAS is an active comet. Consequently, it was also designated C/2025 N1, in accordance with standard cometary nomenclature.

Each time an interstellar object is identified, a recurring question arises: could it be artificial? Specifically, could such an object be a spacecraft or artifact created by an extra-terrestrial civilization? In the case of ‘Oumuamua, its unusual properties prompted some scientists to hypothesize about a potential artificial origin. Although 3I/ATLAS exhibits far more familiar features, it has nonetheless inspired similar speculation. Arguments include its unusual brightness for an object of its size and its atypical trajectory. These anomalies led Harvard astrophysicist Avi Loeb and colleagues to suggest, in a recent publication, that 3I/ATLAS might represent an extra-terrestrial probe. However, it is critical to emphasize that such ideas are highly speculative, and there is no direct evidence that 3I/ATLAS (or any other interstellar object) is of artificial origin. In fact, spectral analyses of 3I/ATLAS have shown emissions of dust and water vapor consistent with natural cometary activity, strongly supporting a natural origin. The probability that an interstellar object is an alien construct is extremely low, yet scientists continue to monitor 3I/ATLAS for any unusual signals or deviations from its predicted path, such as unexplained radio emissions or anomalous manoeuvres, to comprehensively explore all possibilities.

Ultimately, the scientific significance of comet 3I/ATLAS, and of interstellar objects in general, lies in what they can teach us. These bodies are literally fragments of other star systems, offering a rare opportunity to study extrastellar material without leaving Earth. 3I/ATLAS, for instance, may be billions of years older than Earth, possibly making it the oldest comet ever observed. It could contain primordial material from the early history of a distant stellar system. By analyzing the chemical composition of the gas and dust released (using telescopes such as the Hubble Space Telescope and the James Webb Space Telescope), scientists can compare these data with those from native solar system comets. Such comparisons yield valuable insights into planetary formation, cometary evolution, and the potential universality of the building blocks of life.

The study of interstellar objects is still in its infancy. However, the likelihood of detecting more such visitors is expected to increase significantly with the deployment of next-generation sky survey projects, such as the Vera C. Rubin Observatory, which is anticipated to discover dozens of interstellar objects in the coming decade. Consequently, a larger statistical sample will enable astronomers to better understand the diversity and origin of these cosmic nomads. Discussions are even underway regarding intercept missions. The European Space Agency (ESA) is planning to launch a mission named Comet Interceptor in 2029, which will remain in standby orbit awaiting a suitable target (potentially even an interstellar comet) for close-range study. Each newly discovered interstellar object represents a unique opportunity to learn more about planet formation, the chemical diversity of stellar systems, or, most speculatively, evidence of alien technologies.

References:

•    https://science.nasa.gov/solar-system/comets/oumuamua/

•    https://www.livescience.com/space/comets/3i-atlas-is-7-miles-wide-the-largest-interstellar-object-ever-seen-new-photos-from-vera-c-rubin-observatory-reveal

•    https://science.nasa.gov/solar-system/comets/2i-borisov/

•    https://www.space.com/astronomy/comets/new-interstellar-object-3i-atlas-everything-we-know-about-the-rare-cosmic-visitor

•    https://www.space.com/interstellar-comet-first-color-photo.html

•    https://earthsky.org/space/3i-atlas-3rd-interstellar-visitor-alien-probe/#:~:text=Loeb%20is%20a%20controversial%20figure,have%20been%20an%20alien%20craft

•    https://arxiv.org/pdf/2507.12213

https://www.esa.int/Science_Exploration/Space_Science/Comet_Interceptor