In astrology, synastry compares two birth charts to explore how people connect with each other. One of the most important parts of synastry is the relationship between planetary aspects. These are the angles formed between planets in two different charts, and they can show attraction, compatibility, tension, emotional understanding, or long term stability.
Synastry works by comparing the positions of planets, signs, houses, and aspects between two people. The way these parts combine is part of the wider structure of astrology, where different layers of the chart work together to create meaning:
How Planets, Signs, and Houses Work Together in a Birth Chart »
No single aspect guarantees a perfect relationship, but certain combinations appear repeatedly in strong personal connections. Some create immediate attraction, while others build emotional depth, loyalty, or long term growth.
Here are ten of the most commonly recognised synastry aspects in relationship astrology. A broader introduction to relationship chart comparison can also be found here:
What Is Synastry in Astrology? A Simple Explanation of Relationship Charts »
1. Sun Conjunct Moon
This is often considered one of the strongest emotional compatibility aspects in synastry.
The Sun person tends to support the identity and direction of the Moon person, while the Moon person provides emotional understanding and instinctive support.
This aspect can create:
- emotional familiarity
- natural understanding
- strong long term compatibility
Relationships with this aspect often feel comfortable very quickly.
2. Venus Conjunct Mars
This is one of the classic attraction aspects.
Venus represents affection and attraction, while Mars represents desire and physical energy. When they connect strongly between two charts, there is often noticeable chemistry between two people.
This aspect can create:
- physical attraction
- romantic intensity
- excitement and passion
It is commonly found in romantic relationships with strong initial attraction.
3. Moon Trine Moon
(One Person’s Moon Trine the Other Person’s Moon: This aspect occurs when the Moon placement in one birth chart forms a trine angle to the Moon placement in the other chart.)
This aspect creates emotional ease between two people.
Both individuals tend to process feelings in compatible ways, making emotional communication feel natural and comfortable.
This aspect often supports:
- emotional trust
- domestic harmony
- long term emotional stability
4. Sun Trine Sun
When two Suns form a harmonious aspect between two charts, both people often feel naturally aligned in personality and direction.
They may:
- understand each other’s goals
- respect each other’s identity
- share similar approaches to life
This aspect supports mutual understanding without requiring constant adjustment.
5. Venus Trine Venus
This aspect creates shared values and similar relationship styles.
Both people often enjoy:
- similar tastes
- compatible affection styles
- agreement around romance and connection
This can make relationships feel smoother and easier to maintain.
6. Moon Conjunct Venus
This is a soft and emotionally affectionate aspect.
The Moon person often feels emotionally supported by the Venus person, while the Venus person feels appreciated and emotionally connected.
This aspect can create:
- warmth
- emotional closeness
- nurturing behaviour
It is often associated with emotional comfort and kindness.
7. Mercury Trine Mercury
Communication is one of the most important parts of any relationship, and this aspect helps conversation flow naturally.
Both people often:
- understand each other easily
- communicate in compatible ways
- enjoy similar thinking styles
This aspect helps reduce misunderstandings and supports long term communication.
8. Saturn Trine Sun
Saturn aspects are often overlooked, but they can create stability and long term commitment.
The Saturn person may provide structure and support, while the Sun person helps give direction and purpose to the relationship.
This aspect often supports:
- reliability
- loyalty
- long term development
Although less dramatic than attraction aspects, it can be extremely important over time.
9. Jupiter Conjunct Sun
This aspect often creates optimism and encouragement within the relationship.
The Jupiter person tends to support the confidence and growth of the Sun person.
This can create:
- positivity
- shared growth
- encouragement and expansion
Relationships with this aspect often feel uplifting and motivating.
10. Ascendant Conjunct Ascendant
When two people share similar rising signs or closely aligned ascendants, they often approach life in compatible ways.
This can create:
- immediate familiarity
- similar outward behaviour
- shared social style
People with this aspect often feel comfortable around each other very quickly.
Why Synastry Is More Complex Than One Aspect
No relationship can be understood through one aspect alone. A full synastry comparison includes:
- multiple planetary connections
- house overlays
- elements and modalities
- supportive and challenging aspects together
Even difficult aspects can be valuable if both people understand how to work with them.
A Practical Way to Think About Synastry
A simple way to understand synastry is to see it as a comparison between two systems.
Some planetary combinations create ease and attraction naturally. Others create tension that requires adjustment and growth.
Most strong relationships contain a mixture of both.
The zodiac signs, planetary positions, and aspect patterns used in synastry are all part of the broader astrological framework used throughout chart interpretation:
What Is the Zodiac? A Simple Explanation of How It Works »
More technical terminology related to relationship astrology and chart comparison can also be found in the:
Synastry Astrology Glossary »
Aries
Taurus
Gemini
Cancer
Leo
Virgo
Libra
Scorpio
Sagittarius
Capricorn
Aquarius
Pisces