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ScienceIamA female astrophysicist who just published on the famous star Betelgeuse and found it may have swallowed another star. AMA!

Dec 26th 2016 by starstrickenSF • 48 Questions • 5194 Points

I am a female astrophysicist who has studied Betelgeuse for the past 5 years. My team, under the mentorship of Dr. J. Craig Wheeler (University of Texas at Austin), found that Betelgeuse may have gobbled up another star the size of our sun--which may explain why it's spinning at its current rotational velocity. Our next step is to use asteroseismology--studying stellar pulsations--to figure out when Betelgeuse will explode.

Here are some press releases covering our work: http://www.iflscience.com/space/betelgeuse-spinning-faster-than-expected-because-it-ate-a-sun-like-star/

http://www.space.com/35084-betelgeuse-red-giant-star-cannibal.html

http://phys.org/news/2016-12-famous-red-star-betelgeuse-faster.html

And here's our paper: https://arxiv.org/pdf/1611.08031.pdf

Proof (a photo of me talking about Betelgeuse at our local Astronomy on Tap): http://i.imgur.com/eMt0WHs.jpg

EDIT 1: Back online answering while I can! AMA!

EDIT 2: I'm getting some feedback/questions asking why I mentioned I'm a female in my title. I included it because it's an accomplishment to participate- and make an impact- in a male-dominated field. About 20% of physicists are female (https://www.aps.org/programs/education/statistics/womenphysics.cfm). Astronomy is higher, about 35% women, but still more heavily weighted towards men. I include it to help prompt discussions about being a female in science, because there are systematic gender inequalities in the field. I include it to potentially inspire other young women interested in science- and to let them know that they can succeed.

Q:

Will Betelgeuse go supernova? Or is it massive enough to become a black hole?

A:

Yes, it will go supernova! Though we don't think it will form a black hole, it potentially could. Stellar deaths are dependent on the mass of the star, and how much material is left after the explosion. If there's less than 3 solar masses of material left over, it'll probably become a neutron star (and that's what I'm betting on). If there's more than 3 solar masses, it could form a black hole. That's one of the reasons why it's important to try and gauge how massive Betelgeuse is--it will ultimately determine its fate.


Q:

Ok follow up. It's relatively close to us. If it goes supernova are we in any danger? Or will we just get the light show of the century?

A:

No, not in danger! And yes, definitely the light show of the century. We'll be able to see it at night and during the day--we'll have shadows at night, and it'll be brighter than the moon. But we won't be in danger of any debris, or x-rays, or gamma rays. We'll just see something beautiful in the night sky.


Q:

When it does happen, how long will it stay bright?

A:

EDIT: it'll probably will be bright for around 3 months--just confirmed with my advisor.


Q:

Why will it emit only visible light, is this some effect of the processes involved in the explosion? Or it emits everything, and Earth's atmosphere filters out some parts of spectrum more than others?

A:

Stars emit all types of light on the EM spectrum! We'll be able to visibly see it due to visible light, but we can also observe various parts of Betelgeuse (e.g. it's shell) using various parts of the EM spectrum.


Q:

To add on to this answer, not even just EM radiation! IIRC about 99% of the energy released in a typical supernova is in the form of neutrinos. Because the neutrinos only interact weakly, they can actually escape the star before the visible light, since the photons get bogged down scattering off charged particles. There are many neutrino detectors around the world which have a secondary purpose of serving as a supernova early warning system.

A:

Yes!! You're absolutely right--an influx neutrinos would be the first thing we notice. Thanks, @TheNTSocial for pointing that out!


Q:

/u/TheNTSocial FYI, that will notify the user they have been mentioned

A:

Oh hey thanks!! I'm a reddit noob.


Q:

If this thing goes supernova, would it be really fast, like an hour or would the light show last for days? (sorry, I don't really know that much about stars and such.)

A:

It'd be visible for about 3 months!


Q:

If I understand the press release correctly, the stellar evolution code your team used is one dimensional, in that it only models radial variations within the star and assumes spherical symmetry.

On the other hand, it says that one of the main things about Betelgeuse that is unusual is that it's spinning pretty rapidly for a giant star.

But stellar rotation is inherently at least a two-dimensional problem, because the star has a rotation axis and is no longer spherically symmetric. How can you model this with a one-dimensional simulation? More generally, how can you model other physics that might be important (convection, magnetic fields, etc) that are inherently 3d?

A:

Yeah, you hit the nail on the head. This is definitely a problem. 3D hydrodynamic simulations are beginning to become more widely used, but they still require a lot more computer power and time. When we started this investigation 5 years ago, I don't even think 3D simulations were an option. But, to be fair, we don't even understand how to accurately model convection and magnetohydrodynamics in a 3D simulation. Sure, it's probably more accurate than a 1D problem, but how much more? Convection is something MESA has developed pretty robustly over the past few years, but magnetic fields are certainly an issue that would need a 3D code. Bottom line, we'll need further investigation. We found that it's extremely difficult to match the observed parameters (radius, temp, rotational velocity) with the models that MESA produced--and if that's the case, maybe we're not treating rotational velocity (or convection) correctly.


Q:

Hope I'm not too late to the party.

Are you into science fiction at all? How do most scientists feel about it?

I tend to find that my favorite sci fi comes from people who have more than a layman's understanding of science, physics especially. All of my curiosity about the universe starts with theory. Math is fascinating, but I never had the head for it or the motivation to dedicate the energy to make myself learn it at a high level.

A:

I LOVE SCIENCE FICTION!!! My advisor actually wrote a couple of sci fi books and teaches a popular science sci fi course. All about it. I think most people I know in the field love it as well!


Q:

Thanks so much for answering me. I've wondered about this for years. I wonder what the relationship is like between scientists and science fiction authors/creators. What are your favorite sci fi things?

A:

I think some part of the time scientists end up being authors themselves! I love battlestar galactica, Star Wars, Star Trek, and twilight zone. Favorite sci fi books include ender's game, stranger in a strange land, and do androids dream of electric sheep! Most of my colleagues are huge Star Wars/Star Trek fans as well.


Q:

Im very much interested in anything astro- (apart from astrology), and I always thought there is a bit of sadness behind studies in that department. We are advanced enough to assume that someday we will be able to actual visit other planets, other starts, but it wont be us

Like if you were a zoologist and you were neve be able to actually come close to animals. Only look at them via binoculars.

Do you get that sentiment sometimes?

A:

Yup. Absolutely. I would give anything to be able to visit Mars, or travel to other stars. That's ultimately what got me interested in studying space--not the math or the technical aspects, but looking up at the night sky and thinking about what's out there. On one hand, we are very lucky to live during a time with the technology to model stars and view distant galaxies. But it's definitely bittersweet.


Q:

What models do we have to understand how stars can envelop each other? What ways does this merging change the physics of the larger sun?

A:

So, when two stars are close enough that they gravitationally interact, one star can accrete matter, or be stripped of its outer layers, onto the other star. We can model this using tools like MESA, or other hydrodynamic simulations. Basically, we just ad hoc add matter from one star and throw it onto the other. This is important because it changes the rotational velocity of the star--think of the quintessential ice skater who rotates faster when her arms are pulled in, rather than stretched out--potentially hastening the end of its life.


Q:

My name is Emma and I'm 7 ( moms is helping me type Btw )and I want to be an astrophysicist when I grow up. How many galaxies have you found ? And how good in math do you have to be to become an astrophysicist?

A:

Hey Emma! It's fantastic to hear you want to pursue astrophysics! I do theoretical astrophysics (rather than observation) so I actually haven't found any galaxies- but I do get to model supernova explosions! I was actually horrible at math until the middle of high school, when I started getting tutored and spending loads of time on it. Don't get too bogged down in the math-- enjoy star gazing and staring at the sky and I promise the math will fall into place! Feel free to PM me if you'd like to chat more :).


Q:

Is it Beetle juice or Baytle guice?

A:

TBH I oscillate between the two


Q:

Thx! So I'm good either way then :) Is it satisfying to focus on such a small portion of the sky or do you wish there were time for more?

A:

I have to hone in my research questions or else I'd be lost being overwhelmed at how cool everything is! But I'm excited to study something else (whatever that may be) in the future!


Q:

What techniques do you use to study something so far away? And along those same lines, since Betelgeuse is so far away, if it goes Supernova, how long will it take us to find out?

A:

Great question. Betelgeuse is about 640 light years away, so there's a chance (albeit a small one) that it's already exploded. However, what that really means is that it'll take about 640 for the light to reach us once it has exploded. It's also huge, which means it's very easy to see in our night sky--and you would think that would mean it's easily studied. However, it has a massive envelope around it, which actually obscures our observations. We want to see what's happening inside the star, and that envelope makes it difficult to probe.

So, we took a theoretical approach--we ran stellar evolutionary models using a code called MESA to try to match what we were seeing with what our models produced.


Q:

What will yo do to verify your model-based claim?

A:

The next step is to use asteroseismology to probe the stellar core. That basically means trying to predict pulsation frequencies in each of our models, and then observing those stellar pulsations in Betelgeuse itself!


Q:

this is so cool, recently been looking at it since it became visible in my part of the night sky, its just mind boggling for my simple brain to grasp all that could possibly be happening out there but all I see down here is a big star, twinkling away.

A:

It's mind boggling for me too :)


Q:

Cooooool. Drop by /r/Astronomy to say "Hello," on your way out?

Main question: I wanted to be an astrophysicist, when I was 15. But then a Discovery Channel program touched on the politics of research science, with good theoretical physicists losing grad students en mass because the physicists' work had gone out of vogue and the students were worried it'd affect their job hunt. How bad is that aspect of academia, really? Humans like fads, of course, but science can look much worse than you'd expect.

Thanks!

A:

Would love to :) thanks for the invite! I'd be lying if I said I didn't see politics in research science. People are highly competitive, and publishing is the name of the game. However, I honestly don't think I've seen grad students leaving because their advisor's science wasn't 'cool' anymore. While I was looking for grad schools, I had one professor tell me to start my thesis on an unpopular and uncool topic, because that's where I'd be able to make the most potential impact. To be fair, I'm not sold on that idea either. Ultimately, I've mainly seen grad students/post docs leave the field because the possibility of getting a job in astro is so low--one professor told me that when he first started grad school, he calculated the probability of getting a tenured job in academia to be 10-3. That's daunting and tbh kind of insane.


Q:

What could you do if you suddenly had 10x your current compute resources?

A:

Sweet question--I've never gotten this before. Probably investigate 3D hydrodynamic models so I could model things like magnetohydrodynamics, convection, turbulence, etc. We can replicate it somewhat, but a 3D code is really the key--and is outside our current capabilities.


Q:

ever play Kerbal Space Program?

A:

Nope, but my boyfriend has mentioned how cool it is about 5 billion times


Q:

I am studying to be a mathematician, specialising in quantum mechanics. Is there any advice you could give me starting out? I love astrophysics, it was going to be my degree but I ended up going for quantum mechanics on a 50/50!

A:

I love that! Advice: find a mentor (advisor) and use them as a resource. Physics is a really difficult field, and it really helps when someone advocates for you. Also, when it gets really hard, have a sheet of paper with stuff written on it on why you got into it, or a photo that captures something cool in QM, or set your homepage to be a popular science homepage. It's easy to get caught up in the difficult technical aspects that make physics hard, and I found it was really important to maintain perspective. Best of luck!!


Q:

How did you keep motivated during schooling? The thought of tackling this mountain of knowledge makes me a little apprehensive.

A:

It's tough. It's really tough. But finding people who are studying similar stuff, and just as excited as I am about space, helped a lot. The classes were interesting, but what I was REALLY interested in was learning about current questions in the field. Whenever I remembered that, it made balancing classes and research a lot easier.


Q:

How did you become interested in this field? would you say your parents influenced you? what inspired you?

A:

Corny, but true- I've always loved looking at the sky. My parents encouraged my curiosity, but they didn't tell me what I could and couldn't study- rather, they just helped support what I chose to do. That was hugely helpful. I also had a variety of mentors (both female and male) who were really excited about space. That excitement got me excited, and encouraged me to continue my studies.


Q:

Do you believe there is life out there?

A:

I do! I think it's virtually impossible that we're the only life anywhere in the Universe. I don't know if I believe that it's sentient, but I do believe there's life other than on Earth.


Q:

Current Student at The University of Hawaii wondering how Betelgeuse has actually "gobbled up" another star? Have the two stars collided and betelgeuse was the larger of the two and gained its size or what? Amazing discovery I love this! Thank you so much!

A:

Yeah, good question! Hope hawaii's treating you well- I'm hoping to take a trip to Keck soon. So you're basically right on the money- we're thinking that the two stars gravitationally interacted, and Betelgeuse (the larger star) stripped the smaller star of its matter and "absorbed" it onto its outer layers!


Q:

Is it possible that betelgeuse has already exploded and we don't know it yet? If not, what means do we have of knowing that it hasn't exploded?

A:

It's possible, but unlikely--Betelgeuse is about 10 million years old, and only 640 light years away (which means it takes light 640 years to reach us). The likelihood that it already happened, but the light hasn't reached us yet (in other words, exploded in the past 640 years) is pretty small compared to how old it is.


Q:

What happens when Betelgeuse explodes?

A:

We'll be able to see it at night and during the day--we'll have shadows at night, and it'll be brighter than the moon. But we won't be in danger of any debris, or x-rays, or gamma rays. We'll just see something beautiful in the night sky.


Q:

How long do you think this effect would last? Damn, that would be amazing!

A:

Probably around 3 months!


Q:

I also run MESA. Any chance that your inlist files are available? Granted I run 8845...which I'd recommend you check out because of the modified hydrocode.

I ask because I'm finding that some of MESA's results might depend on the &controls min_dt settings.

I didn't see any of MESA's astero data in your paper. Do you have predictions based on MESA that you are looking for?

A:

AWESOME. Yes, would love to collaborate. The min_dt does affect results- were you at the MESA workshop this summer? I definitely need to update mine..

As for astero data, that's the current paper we're working on. We didn't actually use GYRE for it, but manually calculated the damping and convective frequencies for various convective regions in the star. Would be great to get your info- can you PM me?


Q:

Two questions!

  1. Did the studies show that the star was slowly stripped of it's mass over time? Or was it literally gobbled up quickly? I read somewhere about the "Roche Limit" I think where a smaller object breaks apart due to tidal forces once it gets too close to the larger object.

  2. As someone who loves reading and learning about astronomy as a past time and hobby, part of me wants to pursue some form of higher education in astronomy (I just started uni). However I really disliked physics in high school. How much physics do you apply in your field and do you ever find it gets dry?

A:

Thanks for the questions! Here's what I think... 1. You're right on the Roche limit! Basically, once a star gets within the Roche limit, gravity becomes the 'important' force and matter gets stripped from one star and placed on the other. However, there's another wind that comes from rotation. We ran rotating and non-rotating models to study the effect of mass loss on stars. This is something still not totally understood by astronomers--is there episodic mass loss (aka really crazy events that strip the mass quickly) or is it a slow and steady effect over time? We're still not sure. 2. That's amazing that you're curious about astronomy--I'd absolutely recommend continuing to learn about and pursue it! I actually got a dual degree in physics and in astronomy, because the astronomy degree was so similar to the physics degree. There's a lot of physics, but in my opinion it truly depends on your teacher, how comfortable you are in math, and how passionate you are. Personally, I'm still not very comfortable with physics, but I love astronomy so I pushed through it. The cool thing about astrophysics is that you use basic physics concepts (as well as advanced ones) to describe some pretty extraordinary aspects in our universe.


Q:

Thanks for the reply! That's nice to see that you still pushed through it. I'm gonna keep an open mind on pursuing it further. And it turns out that my uni offers electives in astronomy so I'm definitely gonna look into that. Thanks again :)

A:

Awesome! Best of luck, and if you ever have any questions about studying astronomy don't be afraid to reach out!


Q:

I have a question about gamma ray bursts. I read that betelgeuse is bound to go super nova within the next hundred thousand years or so. What would the chances of its GRB reaching and disrupting life on earth? If it's not a concern, why not?

Thanks!

A:

Yes! You're right, we're thinking it'll explode in the next 100,000 years or so. It'll certainly release gamma rays and x-rays, but because we're 640 light years away, we won't be affected. We'll just see a beautiful object in the sky!


Q:

What do we currently think the range of GRBs are? I know they travel in two concentrated jets but I also heard we have detected GRBs from thousands of light years away and many we have detected originated outside our own galaxy. How close would a supernova need to be to be a concern?

Thanks again, I find GRBs fascinating.

A:

Love the curiosity! So, GRBs occur about once every few hundred thousand years in a galaxy like the Milky Way--and only a small sliver of them are close enough to impact life on Earth. I think the current calculations place a dangerous GRB at around 50 light years from Earth--way closer than Betelgeuse!


Q:

I'm a freshman in high school and hoping to become an astrophysicist. Is there anything I can do to help me prepare now for college and grad school? Also, what exactly do you do on a daily basis as an astrophysicist? Thanks :)

A:

Absolutely! I'd suggest finding a mentor at your school or a local university who you can meet up with to ask questions about things you're curious about regarding space. Feel free to email profs at universities you're interested in. Try to take calculus your senior year, and take as many AP tests as you can! But for now, just read about popular science stories regarding space and honestly just get excited about it. That's the best part.

As for my day to day, I stare at my computer a lot of the time (lol). I run models, and then meet with my advisor to discuss. It depends on the advisor in terms of how frequently you meet. I also try to read relevant papers on the arXiv to keep up to date! The rest of the time is spent commiserating with fellow students and attending colloquia!


Q:

What made you enter a traditionally male field (science) and how can I foster that in my daughter?

A:

Thanks for asking! I was lucky to grow up with parents who prioritized education and curiosity. They didn't emphasize science as much as they emphasized intellectual curiosity--whatever form that took. I was never allowed to answer a question with 'I don't know'; rather, I was prompted to answer 'I'll try and find out'. Working in a traditional male field is intimidating, but there are some fantastic mentors out there who want to see young women succeed. I think finding mentors who supported me was 3/4 of the battle. I'd suggest urging your daughter to ask questions, surround her with books and a supportive environment, and take her places (like the outdoors!) to see science (the night sky, plants, whatever!) rather than getting bogged down in the technical aspects. Also urge her to seek out mentors who will advocate for her--and for the science she's curious about.


Q:

How did you modelled overshooting?

A:

MESA treats it as an exponential decay coefficient, which specifies the mixing length and which the user specifies. Read more here in section 4.1! https://arxiv.org/pdf/1301.0319v2.pdf


Q:

are we all going to die soon thanks to this?

A:

Nope! It won't impact us (the debris, x-rays, and gamma rays won't reach us) but we'll be able to see it in the night/day sky!


Q:

Will you continue to study Betelgeuse only? Or is this a temporary project at this moment?

A:

I plan to continue studying it for now! I'm planning on expanding my research on supernovae once we wrap up our project on the asteroseismology of Betelgeuse


Q:

As a child, how did you develop your passion for astrophysics and how did your parents help nurture this passion?

A:

To be perfectly honest, I've always loved stargazing. As I briefly previously mentioned, I was lucky to grow up with parents who prioritized education and curiosity. They didn't emphasize science as much as they emphasized intellectual curiosity--whatever form that took. I was never allowed to answer a question with 'I don't know'; rather, I was prompted to answer 'I'll try and find out'. I was extremely lucky to have parents who surrounded me with resources- be it books or mentors- who encouraged me to continue studying space, even when it's really, really, really hard. I went to several nature camps, where we'd spend the nights star gazing--that was big for me. Being able to visualize and put into context why I studying/going to study space.


Q:

I've got one additional question before I go to bed, do you ever feel sad, because of your study? I mean it's safe to say the average Joe focusses the majority of their life on social status and consumerism, but the kind of stuff you deal with and I will deal with in the future, understanding the vastness of our universe, the insignificance of ourselves and such. Do you ever just find that overwhelming? I've always put it down to my understanding more about the universe and what it's made of than others do. That may be confusing to read, I never did too well at English in school XD always maths and physics/Chem.

A:

Makes sense to me! I find it overwhelming, but more often than not I find it liberating. It's freeing to know that a mistake I made six hours ago doesn't really matter in the grand scheme of things. It gives me perspective, and I find that very beautiful and liberating.


Q:

Hey! I've been interested in theoretical astrophysics since the beginning of my high school career, but in my research on it, I found that jobs were few and far between, and they don't pay very well. How true is this? Thanks for the AMA!

A:

Hi there! I think tenured jobs in academia are extremely hard to get- but I don't think that should dissuade you from studying astro. For those who are tenured, however, I think they are actually paid reasonably well. Grad student/post docs obviously don't get paid much, but the hope is that they'll make up that deficit once attaining a masters/PhD. The great part is that most schools fund you to study in grad school, and there certainly are grants to help fund your studies. I've been daunted by non-academic jobs after studying astro, but I've been happy to find that there are a lot of technical jobs (you develop comp sci skills when doing astro research) that value a physics/astro background. I think there are actually plenty of roles that value analytical backgrounds, regardless of if its astro, physics, finance, or something else.


Q:

Thanks so much for doing this AMA :D Betelgeuse was one of the first stars I could identify by name so I've always been a bit obsessed by it.

If and when Betelgeuse went Supernova what do you think you could potentially learn from the event? Would you be aiming to answer specific questions?

A:

Absolutely! Very excited people are excited and asking questions. The cool thing about Betelgeuse exploding is that it'll be extremely close, so we can study the post-explosion physics (e.g. the dissipating material, the potential neutron star) to a pretty high accuracy. It could confirm or deny theoretical models, which will hone our understanding of the mechanisms behind the explosion (i.e. convective overshoot, rotation, etc.) I'm sure there will be more specific questions, but the major benefit is that it'll provide a high energy event really close to us that will allow for a very unique area of observation.


Q:

One thing that I've noticed about star masses and sizes is that a star's density decreases as a function of its mass, with larger stars such as Betelgeuse being particularly notable for being so much less dense than the Sun. This would appear surprising on first glance because more mass means a higher gravitational attraction within the star.

Would your models predict that Betelgeuse would get even larger as a result of absorbing additional matter from another star, or would the added mass and gravitational pull cause it to contract?

A:

Interesting question! Density is dependent on mass and radius, but the radius of a star is a pretty complicated result of the star's other properties and is dependent on which part of the HR diagram the star falls. If it's on the main sequence, it has one particular relationship between the mass and radius, whereas if it's on the red giant branch (RGB) it has another. A lot of that is due to the extended stellar envelope. My main point is that trying to derive a relationship for stellar density and mass may depend on what stage of stellar evolution the star resides in. As for Betelgeuse, I do think the other star would have added matter to the outer portions--making it balloon outward, rather than contract! That would explain the extra angular momentum and higher observed rotational velocity.


Q:

Hey, I've always been interested in becoming an astrophysicist or something along those lines, what's the process of becoming one like?

A:

That's awesome to hear! Depending on the program, it's essentially a physics degree, with a few additional astronomy classes tacked on. I interned at an observatory and participated in an NSF REU program (https://www.nsf.gov/crssprgm/reu/list_result.jsp?unitid=5045) over the summers, and participated in research all four years. I highly suggest doing research to supplement your studies--that's why you're going into the field, after all! After that, there's grad school for somewhere between 4-7 years, and then typically 1-2 post docs.


Q:

I thought Betlegeuse was a red giant with very low density, basically a glowing vacuum. How can that swallow another star?

A:

Well, it has a really big radius (1,000 solar radii), so it has a "low" density. But because it basically burped out its outer layers, the extended outer shell accounts for most of that radius-- the rest of the mass is in the core. It swallows the other star because it gravitationally interacts and ends up stripping the smaller star of its mass!


Q:

What is your opinion on dogs?

A:

I love them they're perfect humans don't deserve them


Q:

Where do you see yourself in 10 and 20 years? Also, this "Betelgeuse is about 15 to 25 times the mass of our Sun, but it is an astonishing 1,000 times the size!" taken from the iflscience article you posted, is an incredible statement that I cant fathom!

A:

It's pretty incredible! It's huge, but there are some even bigger stars--sometimes up to 200 times the mass of our sun. If Betelgeuse replaced our Sun, it'd engulf Mercury, Venus, Earth, AND Mars. As for where I'd see myself in 10-20 years, I'm still trying to figure that out. I'm heading to grad school in the Fall to pursue my PhD in Astrophysics, which will account for the next 4 - (probably) 7 years of my life. After that, I'd love to continue in academia while also making discoveries accessible to the wider public. I'm not sure what that role looks like, but it's definitely something I'm very interested in.