<p>tl;dr, she might be talking about sunspots (or in this case, Betelgeuse-spots)</p>
<p>There are two things that come to mind, although one of them definitely seems more likely than the other as far as the context.</p>
<p>The first is Zeeman broadening. This is a broadening mechanism for spectral lines brought on by magnetic fields, and the broadening of spectral lines can make resolving certain spectral lines rather difficult, especially if they are close together. I personally haven’t ever done much hands-on work with spectra, but I could see how this could be frustrating. That being said, every time I’ve heard of Zeeman broadening, it’s been as a footnote in a discussion of more dominant broadening mechanisms.</p>
<p>The second is magnetohydrodynamics. This might be the more relevant, seeing as we’re talking about Betelgeuse, and <a href="https://www.space.com/betelgeuse-dimming-star-spots-temperature-changes" rel="nofollow noreferrer">recent speculation</a> has brought up the fact that the temperature changes observed in it might be from sunspots.</p>
<p>Sunspots are the results of magnetic field lines coming out of the star, and this along with other stellar behaviors resulting from magnetohydrodynamics are notoriously difficult to model, and to do so one must often take simplifying assumptions that compromise models in certain limits.</p>
<p>All of that being said, it’s difficult to know exactly what she was talking about, but these situations were the first that came to my mind. I could’ve expounded upon some of these terms a bit more, so if this was a bit too esoteric, let me know which terms were confusing and I’ll put forth a bit more explanation.</p>

CC BY-SA 4.0
2022-08-16T07:43:37.047Z
[ObXKCD](https://xkcd.com/1851/)
PM 2Ring
CC BY-SA 4.0
2022-08-17T21:31:14.377Z
The statement doesn't really have anything in particular to do with neither Betelgeuse nor other specific objects or fields of astrophysics. The reason is that dust and (arguably even more so) magnetic fields are *notoriously* hard to model in many branches of physics, and hence often simply neglected.
pela
CC BY-SA 4.0
2022-08-18T04:18:38.950Z
@pela While that’s true, and I could be wrong here, but my thought was that she wouldn’t have mentioned it unless it was relevant to the subject matter
Justin T
CC BY-SA 4.0
2022-08-18T14:14:01.300Z
That makes sense, but magnetic fields (and dust) are a standing joke among astronomers :)
pela
CC BY-SA 4.0
2022-08-16T05:56:06.720Z
2022-08-16T05:56:06.720Z
Justin T
<p>On the theory side magnetic fields are one of those things we know are important to the structure and evolution of a star, but find hard to include in our models. Internal to the star, they can transport angular momentum from the core to the envelope changing its spin rate and spin profile. But depending on your model this, they can either be not very efficient at this or very efficient at this. So trying to predict how a star evolves with magnetic fields (and rotation in general) is tricky, and quite often is lumped into the &quot;future work&quot; (that never actually gets done) part of research.</p>

CC BY-SA 4.0
2022-08-17T15:41:55.760Z
2022-08-17T15:41:55.760Z
Rob
<p>On cosmological scales (i. e., past the Milky Way and Local Group) visible-light photons are not just blocked outright, but reradiated by dust. The source information has, in some dust-rich areas of the sky, been scrambled. Visible-band observing is the most common and cheapest way, so this is a major setback. Astronomers must turn to infrared, sub-mm, radio, and to an extent X-ray instruments, at higher cost.</p>
<p>Magnetic fields are a second-order problem. Visible-band photons are not much of an issue, though dust grains can be aligned by magnetic fields causing effects like polarization. We would like to try studying the cosmic rays which would be information carriers. But galactic fields bend the paths of these ions, and they are once again scrambled, versus a linear path back to their source.</p>
<p>There are also local sources, like new stars that haven’t cleared their areas of gas and dust, or old stars that are often actively shedding (or just shed). Many large, old stars are also mega-magnetic sources. It’s hard to measure these objects, despite the fact that they’re different and interesting, relative to the unobscured and ‘boring’ stars that are clear and directly observable and well-sampled.</p>

CC BY-SA 4.0
2022-08-16T16:43:25.060Z
2022-08-16T16:43:25.060Z
caInstrument
<p>Does anyone else watch 'Dr. Becky' on YouTube?</p>
<p>Her March 'Night Sky News' video, subtitled 'The biggest black hole burp, a wobbly Milky Way &amp; Betelgeuse is brighter' says that...</p>
<blockquote>
<p>Obviously lots of theories that have been thrown around this by various different people in the academic community, the amateur astronomy community, and also just people commenting on line as well.</p>
<p>But a paper that caught my eye this month was by (Emily M.) Levesque and (Philip) Massey (2020)<sup>1</sup> who pose the explanation... <em>dust</em>... which <strong>if you know anything about astrophysics in general, you know magnetic fields and dust are just the bane of astronomers' lives.</strong></p>
<p><sup>1</sup><a href="https://arxiv.org/abs/2002.10463" rel="nofollow noreferrer">Betelgeuse Just Isn't That Cool: Effective Temperature Alone Cannot Explain the Recent Dimming of Betelgeuse</a></p>
</blockquote>
<p>Why exactly are magnetic fields &quot;just the bane of astronomers' lives&quot;?  How do magnetic fields mess with astronomers' observations?</p>
<hr />
<p>Cued at <code>09:16</code> for the quote, but the topic of Betelgeuse (and Dr. Becky's &quot;I told you so&quot; begins after <code>07:32</code></p>
<p><div class="youtube-embed"><div>
                <iframe width="640px" height="395px" src="https://www.youtube.com/embed/1cw2jJv3Wr8?start=556"></iframe>
            </div></div></p>

CC BY-SA 4.0
2020-08-18T01:24:45.103Z
https://www.youtube.com/watch?v=1cw2jJv3Wr8 at 9:30
Keith McClary
CC BY-SA 4.0
2020-08-18T23:22:45.240Z
related question about the plot shown in the video: [Why does titanium oxide around Betelgeuse produce this particular sawtooth-shaped absorption spectrum?](https://astronomy.stackexchange.com/q/35451/7982)
uhoh
CC BY-SA 4.0
2022-08-17T16:17:49.437Z
Top tip if ever chairing an astrophysics conference session and there are a lack of questions from the floor - you can use "have you considered the effects of magnetic fields?" in almost all circumstances!
ProfRob
CC BY-SA 4.0
2022-08-17T21:24:10.253Z
@ProfRob I did this as a student, now knowing about the history of such a question. Took me a while to figure out why everybody was laughing at me 
pela
CC BY-SA 4.0
2022-08-20T23:26:21.723Z
@ProfRob let's hope someone doesn't start such a habit here in SE :-)
uhoh
<observational-astronomy><astrophysics><magnetic-field>
How do magnetic fields mess with astronomers' observations?
Kurt Hikes
# How do magnetic fields mess with astronomers' observations?

(Asked by: username_0 on 2020-08-18)

Does anyone else watch 'Dr. Becky' on YouTube?

Her March 'Night Sky News' video, subtitled 'The biggest black hole burp, a wobbly Milky Way & Betelgeuse is brighter' says that...

> Obviously lots of theories that have been thrown around this by various different people in the academic community, the amateur astronomy community, and also just people commenting on line as well.
>
> But a paper that caught my eye this month was by (Emily M.) Levesque and (Philip) Massey (2020)1 who pose the explanation... *dust*... which **if you know anything about astrophysics in general, you know magnetic fields and dust are just the bane of astronomers' lives.**
>
> 1[Betelgeuse Just Isn't That Cool: Effective Temperature Alone Cannot Explain the Recent Dimming of Betelgeuse](https://arxiv.org/abs/2002.10463)

Why exactly are magnetic fields "just the bane of astronomers' lives"? How do magnetic fields mess with astronomers' observations?

---

Cued at `09:16` for the quote, but the topic of Betelgeuse (and Dr. Becky's "I told you so" begins after `07:32`

**Tags:** observational-astronomy, astrophysics, magnetic-field
> **Comments:**
> **username_1**: https://www.youtube.com/watch?v=1cw2jJv3Wr8 at 9:30  
> **username_2**: related question about the plot shown in the video: [Why does titanium oxide around Betelgeuse produce this particular sawtooth-shaped absorption spectrum?](https://astronomy.stackexchange.com/q/35451/7982)  
> **username_3**: Top tip if ever chairing an astrophysics conference session and there are a lack of questions from the floor - you can use "have you considered the effects of magnetic fields?" in almost all circumstances!  
> **username_4**: @ProfRob I did this as a student, now knowing about the history of such a question. Took me a while to figure out why everybody was laughing at me   
> **username_2**: @ProfRob let's hope someone doesn't start such a habit here in SE :-)  

---

## 3 answers

### Answer by username_5 on 2022-08-16. Score: 3

tl;dr, she might be talking about sunspots (or in this case, Betelgeuse-spots)

There are two things that come to mind, although one of them definitely seems more likely than the other as far as the context.

The first is Zeeman broadening. This is a broadening mechanism for spectral lines brought on by magnetic fields, and the broadening of spectral lines can make resolving certain spectral lines rather difficult, especially if they are close together. I personally haven’t ever done much hands-on work with spectra, but I could see how this could be frustrating. That being said, every time I’ve heard of Zeeman broadening, it’s been as a footnote in a discussion of more dominant broadening mechanisms.

The second is magnetohydrodynamics. This might be the more relevant, seeing as we’re talking about Betelgeuse, and [recent speculation](https://www.space.com/betelgeuse-dimming-star-spots-temperature-changes) has brought up the fact that the temperature changes observed in it might be from sunspots.

Sunspots are the results of magnetic field lines coming out of the star, and this along with other stellar behaviors resulting from magnetohydrodynamics are notoriously difficult to model, and to do so one must often take simplifying assumptions that compromise models in certain limits.

All of that being said, it’s difficult to know exactly what she was talking about, but these situations were the first that came to my mind. I could’ve expounded upon some of these terms a bit more, so if this was a bit too esoteric, let me know which terms were confusing and I’ll put forth a bit more explanation.

> **Comments:**
> **username_6**: [ObXKCD](https://xkcd.com/1851/)  
> **username_4**: The statement doesn't really have anything in particular to do with neither Betelgeuse nor other specific objects or fields of astrophysics. The reason is that dust and (arguably even more so) magnetic fields are *notoriously* hard to model in many branches of physics, and hence often simply neglected.  
> **username_5**: @pela While that’s true, and I could be wrong here, but my thought was that she wouldn’t have mentioned it unless it was relevant to the subject matter  
> **username_4**: That makes sense, but magnetic fields (and dust) are a standing joke among astronomers :)  

---

### Answer by username_7 on 2022-08-17. Score: 2

On the theory side magnetic fields are one of those things we know are important to the structure and evolution of a star, but find hard to include in our models. Internal to the star, they can transport angular momentum from the core to the envelope changing its spin rate and spin profile. But depending on your model this, they can either be not very efficient at this or very efficient at this. So trying to predict how a star evolves with magnetic fields (and rotation in general) is tricky, and quite often is lumped into the "future work" (that never actually gets done) part of research.


---

### Answer by username_8 on 2022-08-16. Score: 2

On cosmological scales (i. e., past the Milky Way and Local Group) visible-light photons are not just blocked outright, but reradiated by dust. The source information has, in some dust-rich areas of the sky, been scrambled. Visible-band observing is the most common and cheapest way, so this is a major setback. Astronomers must turn to infrared, sub-mm, radio, and to an extent X-ray instruments, at higher cost.

Magnetic fields are a second-order problem. Visible-band photons are not much of an issue, though dust grains can be aligned by magnetic fields causing effects like polarization. We would like to try studying the cosmic rays which would be information carriers. But galactic fields bend the paths of these ions, and they are once again scrambled, versus a linear path back to their source.

There are also local sources, like new stars that haven’t cleared their areas of gas and dust, or old stars that are often actively shedding (or just shed). Many large, old stars are also mega-magnetic sources. It’s hard to measure these objects, despite the fact that they’re different and interesting, relative to the unobscured and ‘boring’ stars that are clear and directly observable and well-sampled.


---

