<h3>The light echo of <a href="https://en.wikipedia.org/wiki/V838_Monocerotis" rel="nofollow noreferrer">V838 Monocerotis (Nova Monocerotis 2002)</a></h3>
<p>has a radius of at least 4.5 light years. First images were circa April of 2002 and the two below are from December 17 2002 and September 9, 2006.</p>
<p>I don't know if this is the largest biggest, but I'll mention it to get things started and because it's so darn cool to look at.</p>
<p><a href="https://i.sstatic.net/Q1fK3.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Q1fK3.jpg" alt="enter image description here" /></a></p>
<p>Sources <strong>above:</strong> <a href="https://commons.wikimedia.org/wiki/File:V838_Mon_HST.jpg" rel="nofollow noreferrer">V838 Mon HST</a>, <strong>below:</strong> <a href="https://commons.wikimedia.org/wiki/File:V838_Monocerotis_light_echo_(HST,_September_2006).jpg" rel="nofollow noreferrer">V838 Monocerotis light echo (HST, September 2006)</a></p>
<p><a href="https://i.sstatic.net/yAEK6.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/yAEK6.jpg" alt="enter image description here" /></a></p>
<ul>
<li><a href="https://astronomy.stackexchange.com/q/28239/7982">How does V838 Monocerotis look today? Any subsequent light echo images, or is the party over?</a></li>
<li><a href="https://astronomy.stackexchange.com/q/14781/7982">Why weren&#39;t the Hubble light-echo images of V838 Monocerotis supplemented by ground telescopes?</a></li>
<li><a href="https://astronomy.stackexchange.com/q/14660/7982">V838 Monocerotis &quot;light-echo&quot; images morphed into nice video, but why so few original images?</a></li>
</ul>
<p><a href="https://i.sstatic.net/xU4aE.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/xU4aE.png" alt="Nature Cover" /></a><a href="https://i.sstatic.net/TSrZZ.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/TSrZZ.png" alt="enter image description here" /></a></p>
<p><a href="http://www.nature.com/nature/journal/v422/n6930/fig_tab/nature01508_F2.html#figure-title" rel="nofollow noreferrer">Figure 2</a> of the Nature paper describes the preservation of the actual light curve (history) within the structure of the light-echo shell:</p>
<p><a href="https://i.sstatic.net/YztnU.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/YztnU.jpg" alt="enter image description here" /></a></p>
<blockquote>
<p>&quot;<strong>FIGURE 2. HST images of the light echoes</strong>
The apparently superluminal expansion of the echoes as light from the outburst propagates outward into surrounding dust is shown dramatically. Images were taken in 2002 on 30 April (a), 20 May (b), 2 September (c) and 28 October (d). Each frame is 83&quot; times 83&quot;; north is up and east to the left. Imaging on 30 April was obtained only in the B filter, but B, V and I were used on the other three dates, allowing us to make full-colour renditions. The time evolution of the stellar outburst (Fig. 1) is reflected by structures visible in these colour images. In b, for example, note the series of rings and filamentary structures, especially in the upper right quadrant. <strong>Close examination shows that each set of rings has a sharp, blue outer edge, a dip in intensity nearer the star, and then a rebrightening to a redder plateau. Similar replicas of the outburst light curve are seen propagating outwards throughout all of the colour images</strong>.&quot;</p>
</blockquote>
<p>From <a href="http://iopscience.iop.org/article/10.1088/0004-6256/135/2/605" rel="nofollow noreferrer">Astronom. J. <strong>135</strong>, 2, 2008</a> or <a href="http://arxiv.org/abs/0711.1495" rel="nofollow noreferrer">ArXiv</a></p>
<p><a href="https://i.sstatic.net/yT35t.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/yT35t.gif" alt="enter image description here" /></a></p>

CC BY-SA 4.0
2021-08-01T09:10:40.123Z
2021-08-01T09:10:40.123Z
uhoh
<p><a href="https://i.sstatic.net/bqnO7.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/bqnO7.jpg" alt="HBC 672" /></a>
Serpens Nebula around the star HBC 672 (source: <a href="https://esahubble.org/images/heic1819b/" rel="nofollow noreferrer">heic1819b</a>)</p>
<p>Which are the largest observed images projected onto interstellar bodies (such as nebulae) by means of electromagnetic radiation? By “largest” I assume their own size, not angular size for the observer.<br />
These should not necessarily be shadows (as shown above). They may be, for example, beams from directional sources or scattering from transient sources (light echo), but trivial spherically symmetric “images” (such as H II bubbles around hot stars) don’t qualify.</p>

<interstellar-medium><size>
Largest projected images (such as shadows) observed
Incnis Mrsi
# Largest projected images (such as shadows) observed

(Asked by: username_0 on 2021-08-01)

[![HBC 672](https://i.sstatic.net/bqnO7.jpg)](https://i.sstatic.net/bqnO7.jpg)
Serpens Nebula around the star HBC 672 (source: [heic1819b](https://esahubble.org/images/heic1819b/))

Which are the largest observed images projected onto interstellar bodies (such as nebulae) by means of electromagnetic radiation? By “largest” I assume their own size, not angular size for the observer.  
These should not necessarily be shadows (as shown above). They may be, for example, beams from directional sources or scattering from transient sources (light echo), but trivial spherically symmetric “images” (such as H II bubbles around hot stars) don’t qualify.

**Tags:** interstellar-medium, size


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## 1 answers

### Answer by username_1 on 2021-08-01. Score: 2

### The light echo of [V838 Monocerotis (Nova Monocerotis 2002)](https://en.wikipedia.org/wiki/V838_Monocerotis)

has a radius of at least 4.5 light years. First images were circa April of 2002 and the two below are from December 17 2002 and September 9, 2006.

I don't know if this is the largest biggest, but I'll mention it to get things started and because it's so darn cool to look at.

[![enter image description here](https://i.sstatic.net/Q1fK3.jpg)](https://i.sstatic.net/Q1fK3.jpg)

Sources **above:** [V838 Mon HST](https://commons.wikimedia.org/wiki/File:V838_Mon_HST.jpg), **below:** [V838 Monocerotis light echo (HST, September 2006)](https://commons.wikimedia.org/wiki/File:V838_Monocerotis_light_echo_(HST,_September_2006).jpg)

[![enter image description here](https://i.sstatic.net/yAEK6.jpg)](https://i.sstatic.net/yAEK6.jpg)

* [How does V838 Monocerotis look today? Any subsequent light echo images, or is the party over?](https://astronomy.stackexchange.com/q/28239/7982)
* [Why weren't the Hubble light-echo images of V838 Monocerotis supplemented by ground telescopes?](https://astronomy.stackexchange.com/q/14781/7982)
* [V838 Monocerotis "light-echo" images morphed into nice video, but why so few original images?](https://astronomy.stackexchange.com/q/14660/7982)

[![Nature Cover](https://i.sstatic.net/xU4aE.png)](https://i.sstatic.net/xU4aE.png)[![enter image description here](https://i.sstatic.net/TSrZZ.png)](https://i.sstatic.net/TSrZZ.png)

[Figure 2](http://www.nature.com/nature/journal/v422/n6930/fig_tab/nature01508_F2.html#figure-title) of the Nature paper describes the preservation of the actual light curve (history) within the structure of the light-echo shell:

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

> "**FIGURE 2. HST images of the light echoes**
> The apparently superluminal expansion of the echoes as light from the outburst propagates outward into surrounding dust is shown dramatically. Images were taken in 2002 on 30 April (a), 20 May (b), 2 September (c) and 28 October (d). Each frame is 83" times 83"; north is up and east to the left. Imaging on 30 April was obtained only in the B filter, but B, V and I were used on the other three dates, allowing us to make full-colour renditions. The time evolution of the stellar outburst (Fig. 1) is reflected by structures visible in these colour images. In b, for example, note the series of rings and filamentary structures, especially in the upper right quadrant. **Close examination shows that each set of rings has a sharp, blue outer edge, a dip in intensity nearer the star, and then a rebrightening to a redder plateau. Similar replicas of the outburst light curve are seen propagating outwards throughout all of the colour images**."

From [Astronom. J. **135**, 2, 2008](http://iopscience.iop.org/article/10.1088/0004-6256/135/2/605) or [ArXiv](http://arxiv.org/abs/0711.1495)

[![enter image description here](https://i.sstatic.net/yT35t.gif)](https://i.sstatic.net/yT35t.gif)


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