NOTE: There is a lot of dispirit information on Steam and on the web about the comets in this game. It is possible that either the comets changed location during developement or they are randomized when a new game is created. The information listed here is where I found the comets in my game.

If you can't find the comets in your game in the same locations then I will have a section following this that shows you how to open your save file which should have all the comet locations for your game.

LIST:
Orange Comet 42, -22
White Comet 37, 16
Brilliant Comet -8, -56
Rainbow Comet -9, -55
Red Comet -2, 4
Yellow Comet 17, -53
Green Comet -12, 30

Brilliant Comet (dupe?) -22, 0
Blue Comet (Rho?) -40, -19

You only need 7 comets to get the achievement.
Rainbow Comet my appear as Prismatic Comet in game (its says Rainbow in the save file).
My save file has 2 Brilliant Comets. When I went to the second location, I did indeed see the second comet, but, I was unable to interact with it, probably because I had already discovered the other one.

The Blue Comet listed in my save file was associated with "Universe Rho" while the others were associated with "Universe Xeno". I have no idea what or where "Rho" is but I was unable to find the Blue Comet in my game.

Starcom Nexus save files are located here on Win 11 machines:
C:\Users\<username>\AppData\LocalLow\Wx3 Labs, LLC\Starcom Nexus\saves

Each save file comes in two pairs:
QUICKSAVE_1710161455.json
QUICKSAVE_1710161455_info.json

Find the save that is the most recent and Open With Word Pad. The file should be human readable.

Do a CTRL+F search for Orange Comet (or whatever one you need)
You should find sections that look like the below.
You are looking for uX: and uZ: these are the coordinates on the in game map that the comet is revolving around. There should also be a star in that area. You will still need to track it down when you get there.
{
"$type": "CometData, Assembly-CSharp",
"majorAxis": 2304.73779,
"minorAxisRatio": 0.274639547,
"theta": 3.02729535,
"persistentId": "Orange_Comet::sector_xeno_42_-22::666313630",
"name": "Orange Comet",
"prefabName": "Orange Comet",
"baseVisibility": -0.7,
"lastVisibility": -0.7,
"x": 567.3674,
"y": 0.0,
"z": -1714.27869,
"rotation": 111.918022,
"coordinates": {
"universe": "xeno",
"uX": 42,
"uZ": -22,
"localX": 567.3674,
"localZ": -1714.27869
},
"playerDiscovered": false,
"permanent": false,
"isLandmark": false,
"firstUpdate": true,
"flags": null,
"componentData": [
{
"componentType": "Owner",
"data": {
"$type": "OwnerData, Assembly-CSharp",
"teamId": 100
}
}
]
},

The Lost Colony can be found at -6.24 x 10.67.
There are clues that lead you toward this location as you go, or you can follow other guides for details. When you find the Lost Colony you need to send down crew to help the colony. you will lose 2 crew temporarily. Then wait 3 in game days. Come back to the colony and regain your crew and say Yes to allowing the aliens access to Kite Station.

When you return to Kite Station, if everything worked correctly, Dr. Pilman should acknowledge the alien lab assistants. Then wait 2-3 more days and return to the station. Dr. Pilman will award you with extra research points and the achievement should pop.

IF THIS DOES NOT HAPPEN...

Then you probably met with the Phage and started on the Phage questline. The Phage are in the same region of space as the Lost Colony so its highly likely if you are on your first playthrough. If you get back to Kite station and the Phage are surrounding it then you must complete that questline before Dr. Pilman will acknowledge the Nyctian scientists. After the phage are dealt with, you should get a series of responses from Dr. Pilman, the last of which should be the Nyctian achievement.

If you are having troubles with this one, you can reload an earlier save before you met the Phage and just speedrun to the Lost Colony and do that quest for the achievement.

It is mostly unknown what leads to the in game promotion. Most people report getting at least one promotion but many people miss the second.

some specualtion about how to get promoted are the following:
Don't lose crew - use shields when you get them (requires a side quest then research). Don't take undue risks on planets.
Follow Starcom Law - when actions come available your crew might mention what Starcom law has to say about the situation. Follow directives when you can.
Complete Objectives - Finishing side quests and finding interesting things and just being an overall explorer and diplomat.

I managed to get my second promotion near the very end of the game so it could take a while. As long as you play a "good guy" you should get it.

This may be the hardest one to get, but, it only took me two tries.
In the very beginning of the game before you are sucked into the glowing ribbon vortex thing you have to pass through an asteroid field. Your crew will mention that its a good opportunity for target practice and acts as a combat tutorial.

If you can clear all asteroids before getting sucked in you get the achievement.

The Nexus is triggered by location, if you travel too far Southwest you get sucked in so sweep from Northwest to SouthEast slowly. Also, zoom out as far as you can to see if there are any stray asteroids. Just be very careful when you get to the end of the field and shoot the asteroids from maximum range.

While this is happening, your crew will mention how bored they are. eventually, when you get the last one the achievement will pop. if it doesn't pop before you get sucked in you need to restart. You might be able to save scum as you go,

There are lots of trading guides out there, but, I wanted to share my tips.
Materials can be harvested from asteroid fields. Asteroids do respawn for farming potential. Mark asteroid fields on your map when you find them. Also, derelict ships with space debris can be a great source of rare materials. When you unlock the Havok Point Defense module it can auto attack asteroids making farming easier (but its a late game tech).

Saurid, Citadel, Ulooquo and Vanderi are met fairly early but require some kind of quest or exchange to deal with them.

The Vanderi require an exchange of technology in order to initiate trade. Don't worry they won't use it against you. If you trade a lot with them you will run out of technologies to trade and be unable to communicate with them further. Trade with them rarely.

The Citadel also sells various artifacts for Titanium. Buy all of them when you have the chance.

The Ulooquo trade information for Platinum. Check back with them frequently for new information if you are stuck on a quest.

Araona are met in the mid game. At first they wont speak to you until you find their original "Nest World". Then you can only trade with the capital city, random ships aren't "authorized" to conduct trade.

Tynoceden are a late game race. They are pretty chill unless you murder their people (harvest trees on planets).

Following the list below you should easily make tons of profit on all things and have plenty left over for building new ship parts and buying rare items from Zoar Station with Adamantine.

• Araona: Reserve Chiralite
  
  • Sell: Adamantine, Gold, Titanium
    
  • Buy: Cobalt, Neutronium, Platinum
• Citadel: Reserve Titanium
  
  • Sell: Cobalt
    
  • Buy: Chiralite, Gold, Neutronium, Platinum
• Saurid: Reserve Gold
  
  • Sell: Neutronium
    
  • Buy: Adamantine, Cobalt-60, Titanium, Platinum, Yttrium
• Tynoceden: Reserve Neutronium
  
  • Sell: Cobalt, Platinum
    
  • Buy: Adamantine, Chiralite, Yttrium
• Ulooquo: Reserve Platinum
  
  • Sell: Yttrium
    
  • Buy: Adamantine, Chiralite, Cobalt-60, Gold, Titanium, Neutronium
• Vanderi: Reserve Cobalt-60
  
  • Sell: Chiralite
    
  • Buy: Gold, Platinum, Neutronium