Oath of the Guiding Stars.

Knights who swear an oath to the stars above aid and guide travellers along their way. They take after the stars themselves, reliable and steadfast in even the darkest of times.

Level 1 Features:

Tenants of the Guiding Stars.

A paladin who takes this oath swears on a star in the sky on a clear night.
Show the Way. It is your duty to guide the lost back onto the righteous path. Otherwise, those who are lost will never find their way.
Stand Strong. Do not waver or break formation. Many rely on you, and for them you must stand strong.
Shine in the Night. Without the light above, the night would be dark. Shine bright and defend against the darkness.

Level 3 Feature:

Oath Spells.

Each oath has a list of associated spells. You gain access to these spells at the levels specified in the oath description. Once you gain access to an oath spell, you always have it prepared. Oath spells don't count against the number of spells you can prepare each day.
If you gain an oath spell that doesn't appear on the paladin spell list, the spell is nonetheless a paladin spell for you.

Channel Divinity: Soothing Light.

You can use your Channel Divinity to call out to your allies, reassuring and bolstering them. As a bonus action, choose a number of creatures up to your Charisma modifier (minimum one creature) within 60 feet of you that can see or hear you. Each target gains a number of temporary hit points equal to your paladin level and is immediately freed from the frightened or charmed conditions.

Channel Divinity: Stellar Glow.

As a bonus action, you can use your Channel Divinity to surround yourself in stardust. You emit dim light in a 5-foot radius for one minute. Attacks made at creatures within this dim light (including you) are at advantage. You can end this effect as a bonus action on your turn.

Level 7 Feature:

Aura of Stardust.

Starting at 7th level, you emit an aura of starlight around you while you're not incapacitated, casting dim light in a 10-foot radius around you. You can activate or suppress this aura as a bonus action.
When an invisible creature moves within 10 feet of you for the first time on a turn or starts its turn there, it must succeed a Dexterity saving throw against your paladin spell save DC or become coated in tiny motes of stardust. While coated in this way, the affected creature can't benefit from being invisible. These motes of stardust disappear once the affected creature moves out of the range of your aura.
At 18th level, the range of this aura increases to 30 feet.

Level 15 Feature:

Polaris.

At 15th level, you are an immovable bastion on the battlefield. While you are conscious, you cannot be pushed or moved involuntarily. Additionally, you have advantage on ability checks and saving throws against being knocked prone.

Level 20 Feature:

Supernova.

At 20th level, you gain the ability become the realization of the end of a star's life. As an action, you can magically infuse yourself with starlight, gaining the following benefits for 1 minutes:
-You emit bright light in a 60-foot radius and dim light for an additional 60 feet.
-Your weapon attacks deal an additional 3d8 radiant damage on a hit.
-When you use your Divine Smite feature, double the number of dice rolled for the radiant damage.
Once you use this feature, you can't use it again until you finish a long rest.