Astronomical event of the year: the Transit of planet Mercury over the Sun’s disk as seen from the Institute of Space Science

Sequence showing the Mercury transit's advance over the Sun's disk observed in H-alfa, on November 11th, 2019. (Foto: M. Teodorescu)
Sequence showing the Mercury transit’s advance over the Sun’s disk observed in H-alfa, on November 11th, 2019. (Foto: M. Teodorescu)

Transits of the inner planets over the disk of the Sun occur periodically, being observed for several centuries now. The interest in such events was mainly a scientific one, focused on a problem that remained unresolved in celestial mechanics for some time. The problem was the advancement of the perihelion of Mercury (a point where a planet, in its movement around the Sun, is closest to it) with a value greater than that calculated by Newton’s law of gravitation. Eventually, the problem was solved at the beginning of the 20th century, with the emergence of the general theory of relativity.

At the headquarters of the Institute of Space Science, a team of researchers from the Space Plasma and Magnetometry Laboratory (Maximilian Teodorescu, Gabriel Voitcu, Costel Munteanu, Eliza Teodorescu and Cătălin Negrea) observed the event from the building’s rooftop. The observation conditions, although not perfect due to the low altitude of the Sun above the horizon, allowed the acquisition of images in two wavelengths (in “white light” at 540 nm for the observation of the solar photosphere, and in the light of ionized hydrogen “H-alpha” at 656.28 nm for the observation of the chromosphere).

In addition to the actual observations, the team had the pleasure of engaging in solar observations with other researchers of the institute. Also, a few children viewed the event through the instrument’s eyepiece, and were fascinated by the appearance of the small dark disk of Mercury with the Sun’s chromosphere in the background.

The current transit showed a major interest from the astronomical community worldwide. The next such event will occur in November 2032.

Below are some photos from the event as well as some astronomical images resulted from the observation session.

This movie  shows the transit of Mercury over the disk of the Sun. Observations are done in the wavelength of ionized hydrogen (H-alpha).

Contact person: Dr. Maximilian Teodorescu <tmaxim[at]>

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