It's Venus. This sight it also said to be the origin of Islamic flags.From:....http://www.fotw.net/flags/islam.html
Origin of the Crescent and Star: a conjunction seen by Mohammed?
A commonly used symbol of Islam, the crescent and star, may represent a "conjunction of the moon and Venus [that] took place in the dawn sky of July 23, 610" according to Gerald S. Hawkins, author of Stonehenge Decoded (Ahmad 1992). Some believe this night exactly coincides with the night in which the Prophet [Muhammad] received his initial revelation from God. While it is true that this night is very close to the actual night of the first revelation, it is not certain that it is the exact one (Ahmad 1992). (Aggour 1995).
Aggour, Kareem S.1995 Creation, Cosmogony, and Astronomy in Islam.
Ahmad, I.D. 1992 Signs in the Heavens: A Muslim Astronomer's Perspective on Religion and Science. Write's Inc. - International, Maryland.
Kareem S Aggour 19 July 1995
This cannot be so. If you check the lunar calendar thoroughly, you will see that the conjunction happened on June 10 of the year 609. However, the influence of that was not related to the beginning of revelations. Muslims all around the world started using crescent after 1453. However, Ottomans were using the crescent even before that (Thomas W. Arnold, History of Islam, Sarajevo, 1989), simply because it was the symbol they inherited from previous tribal life in the early medieval period (1000-1100). The Byzantines started using the crescent around 610 on Tzar Heraklie's birthday. They saw the conjunction of Venus and Moon (Charles Dille, Pictures of Byzant, Sarajevo, 1927)...
Velidaga Jerlagic, 24 September 1998
From an article at a website called "At The Edge" is an article on The Black Stone, by Bob Trubshaw and he makes references to the possible origins of the Crescent moon and stars on many Muslim flag.
"Returning to the geometric significance of the Ka'bah, Professor Hawkins has argued that it is exceedingly accurately aligned on two heavenly phenomena. These are the cycles of the moon and the rising of Canopus, the brightest star after Sirius. In a thirteenth-century Arabic manuscript by Mohammed ibn Abi Bakr Al Farisi it is stated that the alignment is set up for the setting crescent moon - an ancient symbol of the virgin-goddess which still appears in the national flags of many Islamic nations. In some flags - Algeria, Mauritania, Tunisia and Turkey - the crescent is accompanied by a star, perhaps representing Canopus."
T Funari, 12 May 1997