# An old thick-disc body, older than the Sun

> Still possible: 3I/ATLAS formed around a star of the Galaxy's old thick disc, roughly 8 to 14 billion years ago, and is older than the Solar System.

Source: https://mysteriesdept.com/mysteries/3i-atlas/answers/ANS0DFQ30WEZNY9/an-old-thick-disc-body-older-than-the-sun  
Publisher: Mysteries Department  
Licence: CC BY 4.0 (credit Mysteries Department and link the page)  

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[Questions](https://mysteriesdept.com/questions)[3I/ATLAS](https://mysteriesdept.com/mysteries/3i-atlas)[Where in the Galaxy, and how long ago, did 3I/ATLAS form?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0MTPD0FX/where-in-the-galaxy-and-how-long-ago-did-3i-atlas-form)Answer

Answer · 3I/ATLAS

# An old thick-disc body, older than the Sun

3I/ATLAS formed around a star of the Galaxy's old thick disc, roughly 8 to 14 billion years ago, and is older than the Solar System.

**Still possible** Answers **1** question0

## Where it stands

**Still possible** Two pieces of evidence for, none against. It needs two reviews to be accepted.

## What it predicts

- Composition models point to a metal-poor host
- Better kinematic modelling keeps an age above about 7 billion years

## What would rule it out

- A kinematic analysis that excludes thick-disc membership and an old age

## Evidence 2 for · none against

[Carbon isotopes date the ices to 10 to 12 billion years ago](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ52T02NDX/carbon-isotopes-date-the-ices-to-10-to-12-billion-years-ago)

Suggestive

FOR

[Population model: older than 7.6 billion years](https://mysteriesdept.com/mysteries/3i-atlas/evidence/EVD0DFQ52C3MMCJ/population-model-older-than-7-6-billion-years)

Suggestive

FOR

## The questions it answers

[Where in the Galaxy, and how long ago, did 3I/ATLAS form?](https://mysteriesdept.com/mysteries/3i-atlas/questions/QST0DFQ0MTPD0FX/where-in-the-galaxy-and-how-long-ago-did-3i-atlas-form)

Open2 answers, none ahead

## Cite it

```
Mysteries Department. (2026). An old thick-disc body, older than the Sun [Answer ANS0DFQ30WEZNY9]. https://mysteriesdept.com/r/ANS0DFQ30WEZNY9
```

Key

**ANS** 0DFQ30WEZNY9

Kind

Answer · hypothesis

Proposed

[Session 1](https://mysteriesdept.com/mysteries/3i-atlas/sessions/SES0DFQC03S98K5/session-1-3i-atlas-opened-the-literature-to-november-2026) · 2 Nov 2026

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