From : It鈥檚 a warm afternoon on top of Mount Locke in Far West Texas, but inside and under the dome of the oldest telescope here, astronomer Stephen Odewahn shivers, 鈥淚t is cold. Yeah, we鈥檙e in the dome of the 82-inch telescope, the first observatory out here. And it鈥檚 cold, because usually all of the domes, we try to condition them through the day, to have the temperature that it鈥檚 going to be at night, when you open up.鈥�
The discovery of a new planet is cause for celebration, says Odewahn. 鈥淲hen I was a graduate student, in fact, there were no planets around other stars. We didn鈥檛 know of any such thing. We only knew of planets in our solar system. And in the past 15 years, now, we know of a couple thousand planets around other stars."
Andrew Mann, who made the discovery, has a motto. 鈥淭here鈥檚 sort of the saying, 鈥榊ou only know the planets as well as you know the star.鈥欌�� And this relationship has been key to his work. 鈥淪o, my main area research is trying to study small stars. Stars smaller than the sun, which we call M-dwarfs. And in particular, I鈥檓 interested in the planets around them. In particular, small Earth-like planets.鈥�
At the controls of the telescope, Odewahn puts it in perspective: 鈥淢aybe not an uncommon discovery, but it was fairly unique in that it鈥檚 a planet around a low-mass star鈥攎uch, much lower mass than our sun. The type of planet you can find around a lower-mass star is generally a lower-mass planet. And that鈥檚 what鈥檚 exciting about this one. It鈥檚 about four times the mass of our Earth.鈥�
It鈥檚 also important because it鈥檚 nearby. 鈥淚t鈥檚 the closest cluster that we have to our system, to our solar system. And it鈥檚 very young. It鈥檚 about half a billion years old, about 600 million years. And that鈥檚 pretty young for a star.鈥� That鈥檚 about one-eighth the age of our sun.
The discovery began with publicly available data from the Kepler space telescope. According to Odewahn, 鈥淎 couple of amateur astronomers, actually, went online and were going through all of the what-are-called light curves, and possibly showing evidence of the occurrence of a planet. And that鈥檚 what these guys found. And so they actually were the discoverers of the planet. They contacted someone at the University of Texas, Andrew Mann. And he did the important follow-up work to confirm that, yes, it鈥檚 a planet.鈥�
McDonald Observatory was instrumental 鈥� literally 鈥� in making that confirmation. Says Odewahn, 鈥淗e used a relatively new spectrograph we鈥檝e had up-and-running here for about a year. It鈥檚 called the Igrin Spectrograph. It鈥檚 like many spectrographs here at McDonald, except it works way out in the infrared part of the spectrum.鈥�
The spectrograph is kept in the neighboring telescope, and there鈥檚 a waiting list for it, explains Odewahn. 鈥淚 got time on it to do a project to look at galaxies, certain types of galaxies. But unfortunately, it鈥檚 a highly oversubscribed instrument. We worked weeks and weeks on the proposal. We got one night, and it rained almost all night. So we didn鈥檛 get any real data.鈥�
But the data on K2-25B is useful, says Odewahn, because observing a young planet like this helps astronomers better understand how planets form and evolve.
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