An occultation of a star by Mars.
The ancient Chinese made extensive observations of the night sky during the last 4,000 years. Since the 1950s western astronomers have been able to research those records. Their observations tell us that on July 28th 705, 1310 years ago Mars occulted the star we now refer to as 1 Libra.
An occultation occurs when one body passes in front of another. Therefore a planet can pass in front of or occult a star or even another planet. This means that the star would appear to disappear for a period of time.
|Saturn about to be occulted by the Moon as seen through a telescope|
This observation is one of 59 well determined occultations or very close to occultations that were recorded by the Chinese. At this time there were no telescopes, certainly none that we were aware of, so in some cases the two objects may have been so close together that they could not be separated by the eye alone and were therefore recorded as an occultation, but a telescope would have shown that an occultation did not occur.
An eclipse of the Sun by the Moon is also an example of an occultation.