Red Dwarfs: A Planet’s Favorite Host

NASA/JPL-Caltech/ From the NASA Art Gallery "Planets Under a Red Sun" depicts 3 planets orbiting around a red dwarf star. 

By Paola Salazar

For about as long as civilizations have existed, mankind has wondered one question: are we alone? Is there something out there in the stars that’s like us?

While we can’t really speak on the existence of any alien civilizations or lack thereof, we can now, at the very least, safely say that planet formation around stars in and of itself is not uncommon. In fact, there are now over 2,000 confirmed planets, and around 5,000 candidate planets.

Prof. Andrew West/bu.edu

Boston University’s Andrew West, an associate professor in the Department of Astronomy who focuses his research on the stars that most commonly form these planets. These stars are known as red dwarfs or M-dwarf stars. Prof. West teaches a course on these exoplanets, called “Alien Worlds,” and has participated with other organizations to bring the science of stars and planets to the forefront of public attention. For example, his “Alien Worlds” course was brought online so that 11,000 people around the world could take it (so far anyway, with only two sessions having been complete), running an “Ask Me Anything” session on Reddit, where he answered dozens upon dozens of questions that the public had related to science, astronomy, and his particular research within it.

On Monday, Professor West and his amazing crew of past and current graduate students appeared before an audience of about 120 people at The Burren, a bar in Somerville. The talk was part of a series of discussions programmed by Science in the News, a student group coming out of Harvard University and fellow science aficionados from other universities. SITN organizes events at the Burren with local researchers, giving scientists and the public a unique opportunity to learn about science in a relaxed, fun and less structured venue (find out more here). They also run other events throughout the city with the overarching aim of getting people more involved in STEM-related issues.

As you might be able to guess, this particular session was focused on red dwarf stars, some of the smallest, low-mass stars in the universe. Prof. West, with his background, was one of the prime people in the area for getting the public to better understand these stars and the environments that host exoplanets, particularly, ones like ours.

“About 20 years ago, we might be having a conversation about the eight planets that we knew of at the time,” he said, “But at this point, there’s been a giant revolution, really within the last few years, and we now know of over 2,000 confirmed planets...with at least one planet per star.”

West noted that this is a huge statement, because in our galaxy alone, there are around 100 to 200 billion stars! Knowing that there are other planets, we are beginning to find ones that are in what astronomers dubbed the “habitable space,” or Goldilocks zone. This is referring to the planets location around the star that it relates to. If a planet is too close to its sun, its temperature and environment are too extreme and volatile for life as we know it to exist, whereas if it’s too far from the sun, then it’s too cold for life to exist, because everything is frozen over.

Astronomers are starting to zoom in on such planets, to look for the tell-tale signs of life as we know it on earth—they look for some of the most basic elements necessary for our brand of life, such as nitrogen and oxygen. One thing they noticed when they began finding more and more planets, is that a lot of the smaller planets tend to form around smaller stars, which is why some astronomers then focused on researching these stars themselves.

There are different kinds of stars, but of them all, about 70% of them are these smaller, cooler stars that are the red dwarfs. There are about 70-150 billion of them, and for each of them found there are about 2.5 earth-sized planets, with a quarter of them being within that habitable zone.

Because of their makeup and size, red dwarf stars also have a ridiculously long lifespan in comparison to more massive stars, because they’re less volatile, so any habitable planets around them have some time to actually at some point, perhaps hold life.

“For example, fast cars are like the most massive stars in the galaxy. They have an enormous gas tank, they go really fast, but they have really bad gas mileage and you have to refill all of the time,” West explained, because massive stars tend to explode in shorter time frames than less massive stars.

A slower car that may struggle to speed up, will have a tiny gas tank, but have great mileage, meaning you can go longer without having to refill. Keeping in mind that the universe itself is about 14 billion years old, red dwarf stars can be seen as sort of an extreme version of this sturdy car—they have life times that range from hundreds of billions of years up to trillions of years, so every single one of them that’s ever been born is still alive! So really, it’s no wonder that planets seem to preferentially form around these kinds of stars.

Prof. West said that the surge in planetary discoveries over the last few years is likely to continue as technology keeps advancing. He expects that within the next decade, we’ll be able to actually probe these planets and see if life, as it is here, is at all common out there on other planets.

Will you play a part in finding out? If you’d like to, Prof. West has some very important advice.

To anyone now struck with the desire to study these stars or really anything else in STEM-related fields, Prof. West said that the most important quality to have outside of the obvious qualities involved in the field you want to pursue, is writing. Why writing?

Oftentimes, communication can be what gets in the way of great research. Whether it’s for grant writing (how most scientists get their funding for their projects), for publications or for communicating with your own team, if you can’t write well and organize your thoughts in a way that’s easily understood, it ultimately gets in the way of your productivity as a scientist.

If it’s because of his communicative abilities that Prof. West is capable of getting his audience to be passionate and inquisitive about the stars and planets in our Milky Way, then we’re all for encouraging aspiring scientists to improve their skills.

And his advice isn’t just for show. “He was great at literally bringing galactic topics down to earth,” said guest Joseph Diaz, who didn’t seem at all surprised by this, noting Prof. West’s success both in the classroom at BU and online via EdX, Reddit and other media. Joseph also happens to be a volunteer with both SITN and the Cambridge Science Festival.

So, what say you? Ready to take off?

Paola is a Boston-based science journalist with a background in social and life sciences.