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Sun trine Sun is a powerful indicator of compatibility between two people.
Most people learn about astrology through Sun Signs, and their first exposure to synastry is through Sun Sign compatibility.
The Sun is far from the only factor in determining compatibility, but it does play an important role.
The Sun represents who we are on a deep level. It is our ego and our identity. The Sun is who we are when we are just ourselves and not trying to perform any particular function.
The Sun also represents our pride, which can interfere with our ability to truly connect to others.
The trine is the most harmonious aspect in synastry. It eases connections between people, and it forges strong bonds.
Sun Trine Sun in Synastry
In Sun Sign compatibility, signs that are trine to each other are almost always listed as among the most compatible. The reason for this is that Sun trine Sun is a really good aspect to have between two people.
The most obvious reason that this aspect is so good is that two people will have a lot in common.
Another, perhaps even more important, reason is that their egos will rarely clash. This will limit the number of pointless arguments based on pride.
In interpreting aspects between the Sun in the charts of two people, it is also important to consider the aspects that involve Mercury and Venus. Mercury and Venus are never far from the Sun, and the interplay between these planets will give a lot of information as to how the two will interact with each other.
Mercury governs communication, and Venus governs relationships overall. If the aspects involving these planets are harmonious and pleasant, it will greatly increase their compatibility.
If there are hard aspects or no aspects involving Mercury and/or Venus, this will lower their compatibility. This will impair their ability to communicate (Mercury) or make them less attractive to each other (Venus).
There are a couple of sign combinations that color the meaning of this aspect.
Aries and Leo
This is the best combination for Sun trine Sun in synastry. The Sun shines brightly at full strength in both of these signs, as it rules Leo and is exalted in Aries.
It is an especially good aspect if one or both of them were born during the day.
Not only will they find harmony with each other, but they will also revel in each other’s powerful Solar nature.
Both of these signs are characterized by pride and a healthy ego, which can make it hard for them in relationships. When they are together, however, they will instinctively understand each other and will be able to support and encourage each other.
Libra and Aquarius
One of the pitfalls to learning astrology through Sun Signs is that the Sun is not a blank slate. It has a meaning and a character all its own.
This means that with Sun Signs, we are looking at how the Sun behaves when it is in each of the signs, which is different from how other planets might behave in the same sign.
This is especially important when considering Libra and Aquarius, which are the signs that have problems with the Sun. With Libra, in particular, Sun Sign articles tend to emphasize some of its more negative traits. Many of these negative traits are specific to the Sun in Libra and do not apply to other planets in this sign.
In synastry, both Libra and Aquarius are uncomfortable with the Solar nature of others as well as that within themselves. This makes this aspect a little less harmonious than it would be between other signs, especially if one or both of them were born at night.
House Position
The house position of the Sun in each other’s charts will give more information about the specifics as to how this aspect will operate. This will indicates areas of life in which they are able to achieve the greatest harmony.
For more information, see:
Sun in Houses Synastry Meanings: 1st through 12th House
Man’s Sun Trine Woman’s Sun Relationship
Sun trine Sun is a great aspect to have in a romantic relationship. It will bring people together and keep them together.
This aspect will make people feel like they belong together. They will understand each other on a very deep level. They will like similar things, and they will instinctively know how the other ticks.
In and of itself, this aspect is powerful. It can also enhance other positive aspects and smooth over the difficulties caused by negative ones.
It will still be important to look at the other aspects between the two charts, especially between the main relationship forming planets, Mercury, Venus, and Mars.
Even if there are tense aspects between those planets, however, Sun trine Sun will help. The reason for this is that conflicts will not be made worse by matters of ego and pride.
This means that they will have an easier time working through the substance of any problems that they may have.
Sun Trine Sun in Friendship
Sun trine Sun is also a wonderful aspect to have between friends. They will have a natural affinity for one another.
This is an easy, comfortable friendship. They will be able to be themselves with one another and will instinctively understand how the other feels.
They will tend to bring out the best in each other.
If the two are of the right gender and sexual orientation, this is a friendship that could turn into something more. This will only happen in circumstances in which a romance would be appropriate, however.
The connection created by Sun trine Sun is a gentle one. It does not have the urgency that would make friends cross boundaries that they should not cross.
How to Tell if the Sun is Trine the Sun in Synastry
Signs that are trine belong to the same element, Fire, Earth, Air, or Water. Below are the trines by element:

The elemental affinity is a large part of what makes trines so harmonious and pleasant. This affinity will be present if both people have the Sun in the proper signs.
The Sun has a wide orb, which is the allowable margin of error. This orb is seventeen degrees. The closer the aspect is to exact, the better it is.
A trine by degree from the wrong signs does not have the same impact. In this case, the Sun of each of them will be in signs that have difficulty with each other. The cross-sign trine will not trump the whole sign aspect, but it will smooth it out a little.
The two will get along better than they otherwise might.
Conclusion
Sun trine Sun is an excellent aspect in synastry, regardless of the type of relationship involved.
It will help people to feel comfortable with each other and like they have a lot in common. It will also smooth over rough edges that might be caused by other, more difficult aspects.
This aspect is strong testimony that the two are highly compatible.