<p>Supernovae of type Ia can be used as standard candles to determine extra-galactic distances. But these event only occur (roughly) <a href="https://astronomy.stackexchange.com/a/34778/9527">once every 200 years in any given galaxy</a> and rapidly fade away. So to actually see a supernova in another galaxy, you have to be observing a lot of galaxies for a long time. This makes it seem like this isn't a very practical method to determine extra-galactic distances. To how many galaxies has the distance been determined using type Ia supernovae?</p>

CC BY-SA 4.0
2020-01-22T14:52:45.473Z
"standard candle" is the keyword :-) Note, in the last 50 years, we could have seen supernova in 25% of the galaxies.
peterh
CC BY-SA 4.0
2020-01-22T14:53:57.213Z
...of the galaxies that we have been looking at non stop.
usernumber
CC BY-SA 4.0
2020-01-22T14:55:13.180Z
Enough if we make a single photo about it in the $\approx$ 1 month until the SN is visible.
peterh
CC BY-SA 4.0
2020-01-23T00:46:40.197Z
This paper mentions using  740 spectroscopically conﬁrmed type Ia supernovae with high quality light curves https://arxiv.org/abs/1401.4064
D. Halsey
CC BY-SA 4.0
2020-01-29T11:06:47.927Z
No, it isn't a good way of determing distances if your aim is to determine the distance to every galaxy. But thast isn't what they are used for.
ProfRob
<galaxy><distances><supernova><standard-candle>
How many galaxies have had their distance determined using SNIa?
usernumber
# How many galaxies have had their distance determined using SNIa?

(Asked by: username_0 on 2020-01-22)

Supernovae of type Ia can be used as standard candles to determine extra-galactic distances. But these event only occur (roughly) [once every 200 years in any given galaxy](https://astronomy.stackexchange.com/a/34778/9527) and rapidly fade away. So to actually see a supernova in another galaxy, you have to be observing a lot of galaxies for a long time. This makes it seem like this isn't a very practical method to determine extra-galactic distances. To how many galaxies has the distance been determined using type Ia supernovae?

**Tags:** galaxy, distances, supernova, standard-candle

> **Comments:**
> **username_1**: "standard candle" is the keyword :-) Note, in the last 50 years, we could have seen supernova in 25% of the galaxies.  
> **username_0**: ...of the galaxies that we have been looking at non stop.  
> **username_1**: Enough if we make a single photo about it in the $\approx$ 1 month until the SN is visible.  
> **username_2**: This paper mentions using  740 spectroscopically conﬁrmed type Ia supernovae with high quality light curves https://arxiv.org/abs/1401.4064  
> **username_3**: No, it isn't a good way of determing distances if your aim is to determine the distance to every galaxy. But thast isn't what they are used for.  

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## 0 answers

