<p>Of the order 10000–100000 years.  As an example of an old Supernova remnant, you can see the <a href="https://apod.nasa.gov/apod/ap100910.html" rel="nofollow noreferrer">Vela SNR</a>, estimated at 11,000–12,300 years old.</p>
<p>Nasa describes the <a href="https://heasarc.gsfc.nasa.gov/docs/objects/snrs/snrstext.html" rel="nofollow noreferrer">evolution of a remnant</a></p>
<p>Initially, the shock wave expands freely, As it grows it sweeps up material from the interstellar medium which slows its expansion. Expansion causes adiabatic cooling (or the Sedov-Taylor phase) until the point that electrons start to recombine with nuclei. This then allows for more effective thermal emission of UV radiation, which cools the remnant further, and it &quot;disperses into the surrounding medium over the course of the next 10000 years.&quot;</p>
<p><a href="https://arxiv.org/pdf/1605.04923.pdf" rel="nofollow noreferrer">A paper</a> (mentioned by Rob in comments) describes this in greater detail, and offers this graph of the radio luminosity of a supernova remnant.</p>
<p><a href="https://i.sstatic.net/mCKwU.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/mCKwU.png" alt="enter image description here" /></a></p>
<blockquote>
<p><sub> Illustration of a model radio light curve for Type Ia and CC
SNR, evolving through the ejecta-dominated and Sedov-Taylor phases. The
dashed line marks the transition to the radiative phase, where we assume the
synchrotron emission becomes inefficient, </sub></p>
</blockquote>

CC BY-SA 4.0
2021-04-17T11:21:22.937Z
This paper https://arxiv.org/pdf/1605.04923.pdf agrees with that timescale, in terms of radio visibility of supernova remnants.
ProfRob
CC BY-SA 4.0
2021-04-17T09:48:44.577Z
2021-04-17T19:41:29.250Z
2021-04-17T19:41:29.250Z
James K
<p>We cannot see the supernova remnant of the star that triggered the formation of the Sun and the Solar System, as the remnant dispersed and became mixed into the interstellar medium. So I am wondering, what is the maximum size/age of a supernova remnant/planetary nebula can reach before it can no longer be distinguished?</p>

CC BY-SA 4.0
2021-04-17T14:21:32.437Z
As a side comment: while it's possible that the Sun's formation was triggered by a nearby supernova, that's not a requirement for initiating star formation. So in addition to the issues explained in James K's answer, "there was no such supernova remnant" is also a plausible answer.
Peter Erwin
<star><supernova><nebula><size><age>
Long-lived supernova remnants?
WarpPrime
# Long-lived supernova remnants?

(Asked by: username_0 on 2021-04-16)

We cannot see the supernova remnant of the star that triggered the formation of the Sun and the Solar System, as the remnant dispersed and became mixed into the interstellar medium. So I am wondering, what is the maximum size/age of a supernova remnant/planetary nebula can reach before it can no longer be distinguished?

**Tags:** star, supernova, nebula, size, age

> **Comments:**
> **username_1**: As a side comment: while it's possible that the Sun's formation was triggered by a nearby supernova, that's not a requirement for initiating star formation. So in addition to the issues explained in username_2's answer, "there was no such supernova remnant" is also a plausible answer.  

---

## 1 answers

### Answer by username_2 on 2021-04-17. Score: 4 | Accepted answer

Of the order 10000–100000 years. As an example of an old Supernova remnant, you can see the [Vela SNR](https://apod.nasa.gov/apod/ap100910.html), estimated at 11,000–12,300 years old.

Nasa describes the [evolution of a remnant](https://heasarc.gsfc.nasa.gov/docs/objects/snrs/snrstext.html)

Initially, the shock wave expands freely, As it grows it sweeps up material from the interstellar medium which slows its expansion. Expansion causes adiabatic cooling (or the Sedov-Taylor phase) until the point that electrons start to recombine with nuclei. This then allows for more effective thermal emission of UV radiation, which cools the remnant further, and it "disperses into the surrounding medium over the course of the next 10000 years."

[A paper](https://arxiv.org/pdf/1605.04923.pdf) (mentioned by Rob in comments) describes this in greater detail, and offers this graph of the radio luminosity of a supernova remnant.

[![enter image description here](https://i.sstatic.net/mCKwU.png)](https://i.sstatic.net/mCKwU.png)

> Illustration of a model radio light curve for Type Ia and CC
> SNR, evolving through the ejecta-dominated and Sedov-Taylor phases. The
> dashed line marks the transition to the radiative phase, where we assume the
> synchrotron emission becomes inefficient,

> **Comments:**
> **username_3**: This paper https://arxiv.org/pdf/1605.04923.pdf agrees with that timescale, in terms of radio visibility of supernova remnants.  

---

