In this series of posts, we sit down with a few of the keynote speakers of the 238th AAS meeting to learn more about them and their research. You can see a full schedule of their talks here, and read our other interviews here!
Imagine you’re an aspiring actor and want to know how Maryl Streep made it. Or an aspiring soccer player, wanting to get tips and tricks from David Beckham. It’s probably going to be very hard to reach out to them. Fortunately, when you’re a young astronomer at the beginning of your career, there are a lot of senior scientists who just love talking about their experience and their research non-stop. This is especially true if you’re a stellar astronomer, because you’re lucky enough to have Dr. Roberta Humphreys speaking at the 238th AAS meeting!
Dr. Roberta Humphreys is very well-known for her contribution to the field of massive stars. Did you know that massive stars have an upper limit to their luminosities? It is called the Humphreys-Davidson limit! Yup, you guessed it right, Dr. Humphreys is a part of the Humphreys-Davidson limit. As Dr. Humphreys describes this to me: “[the Humphreys-Davidson limit] definitely influenced all of our thoughts about stellar evolution, massive stars, etc. […] I found that the same upper luminosity boundary is held in not just the Milky Way but the Magellanic clouds and then extending it to M31 and M33, which when you see that happening, you begin to realize this is something fundamental.”
In the last couple of years, Dr. Humphreys has been mostly interested, as she tells me, in red supergiants, the coolest (meaning both the temperature and the “cool-factor”) supergiants. You can find them on the right upper edge of the H-R diagram. “I got interested in the most luminous red supergiants. Many of them have extensive circumstellar ejecta but some of them reveal the history of their mass-loss episode just simply in their images. One of the most famous is VY Canis Majoris, and I recently had a press release on that.” So, VY Canis Majoris is VERY big…like VERY! Do you remember everyone’s favorite supergiant, Betelgeuse? “Betelgeuse was making headlines because it got faint and everybody was wondering what the heck is going on.” Apparently, according to Dr. Humphreys, in Betelgeuse, we’re seeing the same phenomenon that we’re witnessing in VY Canis Majoris – large-scale surface activity.
Humphreys is no threat to Earth!
Dr. Humphreys can talk about her research for hours – no surprise that she’s good at teaching! One of her former graduate students, Dr. Jeff Larsen, even decided to name an asteroid after her! “He’d always been fascinated by the search for the asteroid that’s going to destroy the earth. He joined the program called SpaceWatch at Arizona. As a consequence, he was finding comets and asteroids. So he decided to honor his experience at Minnesota by naming it for me […] and they did a little blurb about that in the local media here in the newspaper, and the headline on the article was ‘Humphreys Is No Threat to Earth!’” she laughs.
Old times, old times
Nowadays, astronomers create new software and Python packages almost every day. While talking to me, Dr. Humphreys was reminiscing about old times when she used “a pencil and paper” to make plots. “You wrote a little software program that you’re going to use and you punched up these cards and put them in a box with some control cards and you sent it over to a big mainframe computer” she recalls laughing “then you submitted this box of cards and waited a few hours and then if you’re lucky, your program ran and had some data. That’s the 1970s. Fast forward to now, everything is digital, and even what I did on the big mainframe we can do on my little laptop now and do it a lot faster. Yeah, that’s a big change.” However, now she genuinely believes that having everything digitally, we don’t feel the same connection with the data as she used to feel when she used pencil and paper. “[This] kind of influenced the way people think about the data. To me, the data was always very personal. And I always liked having these large columns of numbers that I could manipulate and look at and plot in different ways. […] I look at stellar spectra. For me, the spectra have always been very personal. […] I look at the spectrum, I look at the emission lines, absorption lines […], and that way you connect personally to the star. When you have a spectrum, it’s like you’re looking at a picture of its face, you know?”
“As Vera Rubin once said ‘It only takes three.”
One of the aspects of Dr. Humphreys’ career path that was particularly interesting to me is being a woman in science. She acknowledges the fact that astronomy is a male-dominated field, and in her career she has done some work to change that, serving for several years as an associate dean for which she was awarded a prize from undergraduate students. One of her programs was to come up with ideas that would not just recruit more women into the faculty, but also retain them. As Dr. Humphreys tells me, she did experience some form of discrimination herself during her career: “In a few cases there are always a few guys who make snide remarks and say hostile things. But, you know, most of the time it wasn’t really overt. It was kind of under the table. Also, lower salary raises, delayed promotions, and all that kind of extended through the mid-70s up until about the early 90s or so.”
Nevertheless, nothing stopped her from becoming a successful woman in science. What really warmed my heart was the fact that Dr. Humphreys was noticed not only by her own department at Minnesota but also by other institutions. “I got many inquiries, including from Minnesota, to move upwards in administration places; [from] colleges, universities, elsewhere in the country, looking for a dean.” However, she decided administrative work is not for her, and she’s happier doing research, or as she describes it: “I still have all my favorite stars, I didn’t want to leave them.”
Don’t let someone else define you.
Being a woman in science myself in my early career stage, I couldn’t resist asking for a piece of advice from a woman who has done so much. “Don’t let someone else define you. Be true to yourself and your own goals. Sometimes it may mean making a difficult decision, and I certainly had to make them more than once and often defending myself and speaking up when I had to. […] Always be sure to know, where your principles are, your goals, and stick to them. That’s my advice.”
To hear more about massive stars, mass-loss, and the luminosity limit, be sure to attend Dr. Humphreys’ Plenary Lecture at 3:10 PM ET on Wednesday, June 9 at #AAS238!
Astrobite edited by Luna Zagorac
Featured image credit: AAS