Ever since the Apollo missions examined the lunar surface, scientists have known that the moon's craters are the outcome of a deep history of meteor and asteroid contacts. But it has only been in the past few decades that we have come to know how regular these are. In case, every few hours, an impact on the lunar surface is shown by a bright flash. These impact flashes are generated as a "transient lunar phenomena" because they are temporary. Ever since the Apollo missions searched the lunar surface, scientists have known that the moon's craters are the outcome of a long history of meteor and asteroid contacts. But it has only been in the past few decades that we have come to learn how regular these are. In case, every few hours, an impact on the lunar surface is indicated by a bright flash. These impact flashes are created as a "transient lunar phenomena" because they are fleeting. To be fair, this miracles is not new to astronomers, as flashes have been reportedly seen lighting up dark sections of the moon for at least a thousand years. It has only been recently, however, that scientists have had powerful telescopes and cameras sophisticated enough to observe these events and characterize them (i.e. size, speed, and frequency).
Discovering how often such events take place, and what they can teach us about our near-Earth environment is the reason the ESA built NELIOTA. In February of 2017, this project launched a 22-month-long campaign to observe the moon using the 1.2-meter telescope at the Kryoneri Observatory located in Greece.
The larger mirror of the Kryoneri telescope provides the NELIOTA scientists to identify flashes two magnitudes fainter than other lunar monitoring programs. But even with the proper instruments, identifying these flashes is no easy task. In addition to lasting for only a fraction of a second, it is also difficult to spot them on the bright side of the since the sunlight reflected from the surface is much brighter. For this reason, these events can only be seen on the "dark surface" — i.e. between a New Moon and First Quarter and mid Quarter and New Moon.
The moon must also be above the horizon at the time and observations must be handled by using a fast-frame camera. Because of these necessary situations, the NELIOTA project has only been able to obtain 90 hours of observation time over a 22-month period, during which time 55 lunar impact events were recognized. From this data, scientists were able to extrapolate that an average of about eight flashes occurs every hour on the surface of the moon.
Another feature that sets the NELIOTA project apart is its two fast-frame cameras that permit lunar monitoring in the visible and near-infrared bands of the spectrum. This enabled the project scientists to conduct the first study ever where the temperatures of lunar impacts were calculated. Of the first ten they detected, they obtained temperature estimates ranging from about 1,300 to 2,800 degrees Celsius ( 2,372 to 5,072 degrees Fahrenheit).
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| Kryoneri telescope |
