Various legends mention that Siva removed the 5th head of Brahma. (Each quotes a different reason). "The acquiring of Brahma's heads makes for an interesting legend. When Brahma was creating the universe, he made a female deity known as Shatarupa (one with a hundred beautiful forms). Brahma was immediately infatuated. Shatarupa moved in various directions to avoid the gaze of Brahma. But wherever she went, Brahma developed a head. Thus, Brahma developed five heads, one on each side and one above the others. In order to control Brahma, Shiva cut off the top head. Also, Shiva felt that Shatarupa was Brahma's daughter, being created by him. Therefore, Shiva determined, it was wrong for Brahma to become obsessed with her. He directed that there be no proper worship in India for the "unholy" Brahma. Thus, only Vishnu and Shiva continue to be worshipped, while Brahma is almost totally ignored. Ever since the incident, Brahma has been reciting the four Vedas in his attempt at repentance." "Originally, Brahma is said to have five heads. The Matsya Purana explains the reason for this. It states that Brahma created a woman, known by different names: Satarupa, Sarasvati, Sandhya or Brahmi. Because of her beauty, he fell in love with her and stared at her longingly. To avoid his gaze, she moved to his left, then behind him, and then to his right. But a head sprang up wherever she moved to enable Brahma to continue looking at her. In desperation, she jumped into the air, but a fifth head appeared on top. Brahma then asked her to help him create the universe. He lived with her for 100 divine years, at the end of which Manu was born." "There are different explanations for why Brahma only has four heads now, as opposed to his original five. According to the Puranas, Brahma and Vishnu were once arguing over who was superior of the two. They discovered from the Vedas that Shiva was the Supreme Being. Brahma however, spoke disparagingly about Shiva. In anger, Shiva cut off the head which had spoken, and therefore Brahma was left with four heads." "The Visvakarmas of Karnataka consider themselves to be the descendants of the Rg Vedic Lord Visvakarman. The descent of the Visvakarmas from Parabrahma is a theme in their oral tradition, as well as in their printed stories. The five functions of the five-headed Parabrahma or Visvabrahma is made explicit. The first Brahma, Manu, produced a knife necessary to separate the child born in the womb from his mother, the sword for protecting the world and the edge of the plough to obtain grain. His descendants are the ironsmiths. The second Brahma, Maya, gave protection and his descendants are the carpenters. The third Brahma, Tvashtri, began the creation of metallic vessels and other implements needed for the yajnashala and his descendants are the coppersmiths. The fourth Brahma, Silpi, was a sculpture. The fifth Brahma, Visvajna, made gold ornaments and his descendants are the goldsmiths." "Shiva as Kapalin usually carries a human skull in his hand to confront the world with its mortality. Sometimes he uses the skull-cap as a drinking bowl. He wears a garland of skulls. The skull is said to be the fifth head of Brahma, cut off by Shiva who resented Brahma's pride and cupidity." But background of these stories there are greater views hidden. These are symbolic in nature. Astronomical Significance: Pandit Bapu Deva Sastri who translated the Surya Siddhantam, mentions that Brahma refers to the Auriga Constellation. Auriga is a 5 starred pentagon. So we have a 5 faced Brahma. Arudra is the nakshatram for which Siva is the deity. This has commonly been identified as Betelguese by many sources. In this post the sky-maps will help us identifythe various nakshatras : Identifying Nakshatras – Betelguese, Arudra in Orion; Aldeberan, Rohini in Taurus; Mrigasira and Krutika; Punarvasu, Pollux in Gemini ; Brahma, Auriga Identifying Betelguese or Arudra. (Siva / Rudra) Identifying Auriga – Five Faced Brahma : In the picture, Take the limb of Taurus that does not have Rohini (Aldeberan) in it. The star “beta”, common to Auriga and Taurus in the drawing below, is the one called El Nath. Arudra, El Nath and Capella are on a line. That will point you to the 5 sided pentagon, the Auriga. Auriga has been identified as Brahma by Bapu Dev Sastri who translated the Surya Siddhantam. Do you remember the story where Siva knocked of the 5th head of Brahma which was on the top? That story is connected to this constellation. Capella sounds like Kapala (Skull in Sanskrit) does it not? Now, in the figure below visualize a line that connects Betelguese, El Nath and Capella of Auriga. If Capella is removed from Auriga, you have a 4 faced Brahma (4 starred constellation). All Puranas were overlaid with astronomical information, which made the astronomy easy to remember and pass on. So while Vyasa preserved the information in the Vedas, in one way., he again made sure that the knowledge was retained for posterity in another way too. source: ancientindians