The Mystery of HD 139139: The âRandom Transiterâ Star
Discovery and Characteristics
HD 139139, also known by the nickname âRandom Transiterâ, is a star that was observed during K2 Campaign 15 of the Kepler Extended Mission. The star is located about 351 light-years away and is a binary system consisting of a yellow and an orange star.
The star is of special interest because of a very unusual pattern of brightness variations that was discovered in 2019. The Kepler space telescope captured 28 irregular decreases in the brightness of HD 139139, which resembled a typical planetary transit but was highly unusual in that it lacked periodicity.
The Nature of the Mystery
Scientists noted that HD 139139âs irregular brightness decreases exhibited characteristics similar to the transits of Earth-type planets: each decrease lasted about 0.2 days (about 5 hours) and followed a pattern of decreasing the starâs brightness by about 0.2%. But the biggest mystery was that the decreases didnât follow a regular pattern at all.
To explain this phenomenon, scientists initially suggested the possibility of at least 14 and as many as 28 planets around HD 139139, which was astronomically astounding. But the possibility of such a large number of planets in one system was difficult to explain with our current understanding of planetary system formation theory.
Recent Research Trends
In 2023, a follow-up observational study was conducted using the CHEOPS (CHaracterising ExOPlanet Satellite) space telescope. The aim of the study was to confirm with independent measurements the previously discovered shallow aperiodic transits in HD 139139.
The results of this study were published under the title âNo random transits in CHEOPS observations of HD 139139â, suggesting that no random transits like those previously observed by K2 were found during CHEOPS observations. This suggests that the phenomenon originally observed may have been transient, or only occurring under certain conditions.
Alien Civilization Hypothesis and Alternative Explanations
Some scientists have put forward an intriguing hypothesis that the unusual phenomena in HD 139139 may be related to the construction of megastructures by a highly advanced alien civilization. This suggests the possible existence of megastructures to capture stellar energy, such as âDyson spheresâ.
In July 2024, a new concept called âNuclear Lifeâ was proposed to explain the strange brightness decrease of HD 139139. According to this theory, there is a possibility that there is some kind of life inside the star that uses some of the starâs nuclear fusion energy to sustain itself.
However, scientists are also suggesting a more realistic explanation. It could be that celestial objects such as dust clouds, asteroids, or comets orbiting the star are irregularly blocking the starâs light. Alternatively, errors in the observing equipment or data processing cannot be ruled out.
Scientific Implications and Future Research Directions
HD 139139, along with Tabbyâs Star (KIC 8462852), is one of a group of stars with unusual brightness variations that have become important targets of research in the search for extraterrestrial life (SETI). The study of these stars is contributing to the development of new methodologies to search for technosignatures of alien civilizations.
Currently, scientists are continuing their efforts to collect more observational data and test various hypotheses. Future observations of HD 139139 with high-performance instruments such as the James Webb Space Telescope are expected to provide important clues to solve this mystery.
More Observational Data and Explanatory Hypotheses
To provide more details about the brightness dip in HD 139139, the star was observed by NASAâs K2 mission over a period of 80 days, with each measurement having a very precise error of about 30 ppm (0.003%). Most of the brightness decreases were around 200 ppm, which is similar in magnitude to the transit of an object about 50% larger than Earth. Interestingly, only one of these showed a decrease about twice as deep.
Various Alternative Hypotheses
There are additional hypotheses that scientists have proposed to explain the enigma of HD 139139:
- The disintegrating planet theory: A small planet ejecting a cloud of dust in the process of being vaporized by its parent star could be the culprit. But even in this case, there would have to be some degree of periodicity, which HD 139139 hasnât shown.
- Dust-emitting asteroids: Planetesimals in the process of evaporation could be responsible for the irregular decline. This has been observed in the young star RZ Psc and the aging white dwarf WD-1145. However, in the case of HD 139139, all transits show roughly the same depth, which is inconsistent with this theory.
- Planets in binary systems: In a binary system, the periodicity of the planet could disappear. However, for this hypothesis to hold, both the planet and the binary system would have to have very short periods, and the team did not find any stable systems that match the observational data.
- Young âdipperâ stars: Young stars can show irregular brightness decreases due to clumps of dust from their disks blocking the line of sight. However, the HD 139139 system appears to be older and has no infrared excess emission, which also doesnât fit this hypothesis.
- Short-lived starspots: On the Sun, starspots last for weeks, but in HD 139139, it is hypothesized that there may be a rare process that causes them to appear for only a few hours and then disappear completely.
Statistical Implications of CHEOPS Observations
No transits were detected during CHEOPSâ two observing campaigns in 2021 and 2022. The team estimated the probability of missing any transits to be 4.8%, assuming that the frequency of transits during the 2017 Kepler observations remained unchanged. This means that the transits detected by Kepler were likely present but deactivated during the CHEOPS observations. However, the team noted that the possibility that the transits were due to rare observational instrument errors cannot be completely ruled out.
Contributions from Citizen Scientists
The unusual phenomenon in HD 139139 was first discovered by two independent groups of citizen scientists working with professional astronomers - a good example of the importance of citizen participatory science in astronomy. They used the power of the human brain to discover a complex pattern in the Kepler catalog that is difficult to identify with computer algorithms.
What it Means in the Context of Space Exploration
Interestingly, HD 139139 is one of the 0.5% of stars in the sky from which Earthâs transit will be visible. This information, according to Andrew Vanderburg, means that its transit impact parameter is close to 0.9, which means that alien civilizations would barely be able to see us. From this position, Earthâs transit duration would appear about 40% shorter than a perfect edge-on transit.