The Merging of Two Planets
A conjunction (0°) is formed when two planets occupy the same or very close degree of the zodiac. It is the most powerful of all aspects the energies of both planets merge completely, operating as a single combined force. Conjunctions are neither harmonious nor challenging by default: their nature depends on the planets involved. Sun conjunct Jupiter is expansive and fortunate; Sun conjunct Saturn is serious and demanding; Sun conjunct Pluto is intensely transformative.
Orb and Intensity
Most astrologers allow an orb of 8–10° for conjunctions involving the Sun or Moon, and 6–8° for other planets. The closer the orb, the more powerful the conjunction. A conjunction within 1° (partile) is exceptionally potent. Planets within 17' of the Sun are considered cazimi (in the heart of the Sun) a special condition of extreme solar empowerment. Planets within 8° of the Sun are under the beams and considered weakened.
Reading Conjunctions in Your Chart
When you find a conjunction in your natal chart, treat those two planets as a fused unit. Their house, sign, and any other aspects to them all apply to this combined energy. A person with Venus conjunct Mars experiences their drives toward love and desire as inseparable. Moon conjunct Pluto experiences emotional life as intensely transformative. Transiting conjunctions to natal planets time periods of new beginnings and fresh initiation in those areas.