After 14 years of studying wobbling stars, physics associate professor David Mitchell and his research team have discovered seven new planets.
The two most recent ones are called “t Gem b” and “91 Aqr b.” “T Gem b” is the largest and farthest of the two; it is 319 light years away and is at least 21 times the mass of Jupiter, while “91 Aqr b” is 149 light years away and three times the mass of Jupiter.
For comparison, Pluto is a few light hours away, Mitchell said. Both of the new planets are in our galaxy.
“These are stars that, if you went to a nice dark place, you could see them with your eye,” Mitchell said. “So in the grand scheme of things, that’s very close.”
While most astronomers look at planets orbiting our sun, Mitchell and his research team decided to look beyond the solar system, to planets that orbit stars known as red giants — stars at the end of their lifetime.
These stars are not clustered all in the same place; they are scattered across the universe. Mitchell and his team — Sabine Reffert and Andres Quirrenbach, who live in Germany — chose 400 red giants to study based on brightness and size.
“We wanted to see if the stars were really massive, if they ended up with really massive planets as well,” he said.
But Mitchell cannot get a physical image of either planet — at least not as of now, he said. This is because the star is big and bright, and the planet is tiny and simply reflects light, rather than emitting it.
Mitchell can confirm that the dot he is observing is an actual planet is by measuring the wobble of the star itself. As the planet goes around the star, the planet’s gravity pulls on the star, so the star wobbles back and forth, he said.
“It’s the motion of the star as the gravity of the planet pulls it back and forth,” Mitchell said.
Mitchell knows there are more planets out there, he just has to prove it. But this can be a long process, because he must eliminate all other possibilities, such as whether the star’s wobble is simply the star pulsating. The team uses a telescope that looks at infrared light to determine whether it’s pulsating.
“So even though we’re confident there’s more planets, and we see this data that looks like more planets, the process of eliminating other possibilities takes a long time,” he said. “So, seven now. But in the future, there will be more.”
However, Mitchell does know they are gas planets. Likely they resemble Jupiter, he said, meaning they probably don’t contain liquid water needed for life.
Finding life is really what astronomers (and other people) are interested in, even though that’s not what they talk about, Mitchell said. He said if they find a planet that’s in the right place for life, they would mark it for further study.
However, astronomers need better equipment before they can see the planet and what’s on it, as well as what the planet and its atmosphere are made out of, before they can determine if it’s in the right place for life, Mitchell said. But he thinks this can happen within our lifetimes.
“And I’m totally psyched to do that,” he said. “I think that’d be awesome.”
While the idea of life on another planet is interesting to nutrition senior Christina Pschorr, she estimated it would take humans another 100 years or so to even reach a planet so far away, let alone figure out how to communicate with potential aliens. That’s assuming humans could even survive in an extraterrestrial environment, she said.
“I just think it’d be so cool in the future if we had ‘out of planet’ students instead of the ‘out of country’ or ‘international’ students now,” Pschorr, who is enrolled in Mitchell’s Introduction to the Solar System (ASTR 101) class, said. “But the likelihood of that is way in the future.”