Even amid a federal budgetary crisis that has brought an end to the US space shuttle program, American astronomers continue making astonishing discoveries. The latest and perhaps greatest of those — revealing that there are at least three, and possibly hundreds, of previously unnoticed planets perhaps capable of sustaining life as we know it — was made by a team of astronomers led by Caltech researchers in Pasadena. 
The newly discovered celestial bodies are the three smallest confirmed planets ever detected outside Earth’s solar system and orbit a single star that is smaller than Earth, yet they appear to be rocky with a solid surface. Previously, astronomers had found only four other rocky — aka terrestrial — planets around other stars. But this time, it is believed there may be hundreds of similar planets awaiting discovery. 
The reason for that hope lies in the fact that the three new planets orbit a red dwarf star called KOI-961. Therefore, other red dwarfs might also have planets orbiting them, and since red dwarfs are the most common kind of star in the Milky Way, the likelihood that hundreds of other such planets might exist is considered a strong one. 
Since KOI-961 was first flagged as a potential planetary system by NASA’s Kepler mission — a space telescope that looks for planets around sun-like stars by scanning the sky for stars that periodically dip in brightness — the discovery is a doubly strong one for Pasadena-based scientists. That’s a fact that makes John Johnson, an assistant professor of astronomy at Caltech who was on the planet-discovering team, especially happy.
“Two months ago was when we realized that we would end up with a Mars-sized planet, and it was a bit of an emotional rollercoaster, as we made sure we were absolutely right, but that’s the way science goes,” says Johnson, who had just finished with a press conference about the discovery at the American Astronomical Society meeting in Austin, Texas, on Thursday. “But we’ve moved on to the next exciting thing, and that’s what gets me out of the bed in the morning. Looking back, it’s an amazing thing to discover a Mars-sized planet. We’ll just keep going! They often say the sky’s the limit, but there’s no sky here and no limit.”
The new report, which was fast-tracked for analysis and publishing in The Astrophysical Journal to coincide with the AAS meeting, comes just a few weeks after the Kepler team announced it had detected two rocky planets around the sun-like stars Kepler-20e and Kepler-20f. These were the first Earth-sized planets ever found, and followed the January 2011 discovery of the first unequivocally rocky planet around another star, Kepler-10b. 
While the flurry of planet discoveries is exciting, Johnson cautioned that just because the newly discovered planets could possibly sustain life, that is not definitive. For one thing, the planets are about 100 times closer to KOI-961 than Earth is to the sun, thus causing the surface temperatures to be about 200 degrees Celsius (400 degrees Fahrenheit) for the outermost planet and 500 degrees Celsius (more than 900 degrees Fahrenheit) for the innermost one. 
And since NASA continues to aim for an eventual Mars landing that could still be decades in the making, earthlings shouldn’t count on visiting the new planets anytime soon, if ever. 
“Not a single one of these is habitable, but the hope is for the future discovery of habitable ones,” says Johnson. “I wouldn’t say never, but you can’t do it tomorrow. If you were traveling at the speed of light, it would take 120 years to get to those, versus just 10 to 12 light minutes to Mars, but astronomically speaking, it’s extremely close. This is basically a nearby neighbor to the sun. Mars is 10 to 12 light minutes away. We’re not going to do it tomorrow, or 10 years, but I would never say never.”
Amazingly, Johnson and the rest of the Caltech astronomers had to rely on photos taken by a 60-year-old telescope — Palomar Observatory’s 48-inch Samuel Oschin Telescope, built in 1961 — to make the cutting-edge discoveries. The researchers had to confirm that dips in light, which they hoped were caused by undiscovered planets, were not in fact something else, such as a pair of background stars in orbit. 
Because KOI-961 is relatively close at about 130 light-years away, it appears to drift across the sky quickly. By comparing pictures of the star over the years, astronomers were able to see there were no stars behind it that could produce the light dips they saw. They found none, leading to the conclusion that the light dips from KOI-961 are produced by three small, terrestrial planets.
Meanwhile, the cutting-edge Kepler’s initial measurements actually underestimated the size of KOI-961 and any planets it might have had. It took amateur astronomer Kevin Apps, who eventually co-authored the paper amid a large group headed by Caltech postdoctoral scholar Philip Muirhead, to notice that KOI-961 bore a remarkable resemblance to a red dwarf called Barnard’s Star. 
“That’s what blew the case wide open,” Johnson recalls. “It allowed us to infer that KOI-961 had many of the same properties as Barnard’s Star.” 
 As with most endeavors, one big success often fuels the drive for more. And so it is that Johnson and the rest of the Caltech and NASA team members have amped up their excitement and strive to keep furthering mankind’s understanding of the universe. 
“The ancients have wondered are we alone?” says Johnson. “Is the Earth a unique place, the center of the entire universe, the only place that can harbor life? Or can we place it in a broader galactic perspective, one of many places that can harbor life? There is no endgame. 
“The universe is so complex and amazing,” Johnson continues. “This is the most noble pursuit you can do in all of science — to ascertain if there are other places that harbor life. If we find one, we’ll find hundreds and thousands and then understand our own planet better as a result.”