<p>The coordinate system in this image is RA and Dec. It is a coordinate system which uses the Earth's equator (projected onto the sky) as its midline.</p>

<p>The inverted U is the Milky Way. The Milky Way is full of dust and gas, and blocks our view of galaxies (and supernovae) behind it. There is enough dust in the plane of the galaxy to block our view in that direction. For example the galaxy <a href="http://apod.nasa.gov/apod/ap160129.html">IC 342</a> is one of the nearest galaxies, and would be brilliant if it were not close to the galactic plane. There may be other galaxies that are completely hidden.</p>

<p>Our galaxy's bulk not only hides supernovæ that are in other galaxies, it also hides most of the supernovæ that occur in the Milky Way</p>

CC BY-SA 3.0
2016-06-05T06:53:58.717Z
I found a [Hammer projection](https://en.wikipedia.org/wiki/Hammer_projection) of the [Milky Way](http://i.imgur.com/dNbz9Gc.png) in [this blog](http://armchairastronautics.blogspot.tw/2014_06_01_archive.html) - there may be better ones, it might add "aha!" value. (I learned about Hammer projection 5 minutes ago in the [python script](https://en.wikipedia.org/wiki/File:Sn_discoveries.gif) attached to the image in the original question).
uhoh
CC BY-SA 3.0
2016-06-06T21:31:12.920Z
The gap is known as the Zone of Avoidance: https://en.wikipedia.org/wiki/Zone_of_Avoidance
James K
CC BY-SA 3.0
2016-06-04T18:32:42.270Z
2016-06-05T18:16:48.200Z
2016-06-05T18:16:48.200Z
James K
<p>I came across <a href="https://en.wikipedia.org/wiki/File:Sn_discoveries.gif" rel="noreferrer">this gif</a> showing supernova discoveries from the late 19th century to 2010. Here's the data in 2010:</p>

<p><img src="https://i.sstatic.net/nxri2.png" alt=""></p>

<p>Notice that there's a prominent region shaped like an inverted U in which there are few detection points, which I have crudely enclosed:</p>

<p><img src="https://i.sstatic.net/SIOkM.png" alt=""></p>

<p>Why is this? Is it an artifact of detectors simple not observing that part of the sky, or is there some underlying astronomical reason?</p>

<supernova><observational-astronomy>
Why is there a gap in this image of supernova discoveries?
HDE 226868
# Why is there a gap in this image of supernova discoveries?

(Asked by: username_0 on 2016-06-04)

I came across [this gif](https://en.wikipedia.org/wiki/File:Sn_discoveries.gif) showing supernova discoveries from the late 19th century to 2010. Here's the data in 2010:

![](https://i.sstatic.net/nxri2.png)

Notice that there's a prominent region shaped like an inverted U in which there are few detection points, which I have crudely enclosed:

![](https://i.sstatic.net/SIOkM.png)

Why is this? Is it an artifact of detectors simple not observing that part of the sky, or is there some underlying astronomical reason?

**Tags:** supernova, observational-astronomy

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## 1 answers

### Answer by username_1 on 2016-06-04. Score: 54 | Accepted answer

The coordinate system in this image is RA and Dec. It is a coordinate system which uses the Earth's equator (projected onto the sky) as its midline.

The inverted U is the Milky Way. The Milky Way is full of dust and gas, and blocks our view of galaxies (and supernovae) behind it. There is enough dust in the plane of the galaxy to block our view in that direction. For example the galaxy [IC 342](http://apod.nasa.gov/apod/ap160129.html) is one of the nearest galaxies, and would be brilliant if it were not close to the galactic plane. There may be other galaxies that are completely hidden.

Our galaxy's bulk not only hides supernovæ that are in other galaxies, it also hides most of the supernovæ that occur in the Milky Way

> **Comments:**
> **username_2**: I found a [Hammer projection](https://en.wikipedia.org/wiki/Hammer_projection) of the [Milky Way](http://i.imgur.com/dNbz9Gc.png) in [this blog](http://armchairastronautics.blogspot.tw/2014_06_01_archive.html) - there may be better ones, it might add "aha!" value. (I learned about Hammer projection 5 minutes ago in the [python script](https://en.wikipedia.org/wiki/File:Sn_discoveries.gif) attached to the image in the original question).  
> **username_1**: The gap is known as the Zone of Avoidance: https://en.wikipedia.org/wiki/Zone_of_Avoidance  

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