A NASA space telescope’s harvesting of new planets is continuing apace with 26 new worlds confirmed in 11 new solar systems. It seems to confirm that the Milky Way must be packed with planets galore. 

An artist’s impression of a new planetary system. Credit: NASA/JPL-Caltech

The latest big haul was made by the Kepler mission and nearly doubles the number of verified planets found by this telescope as it constantly watches a small area of the sky.

It also triples the number of stars that are known to have more than one planet making transits across their disks. It is from the tiny dips in brightness that these transits cause that the planets give away their presence.

The new discoveries announced by NASA’s Jet Propulsion Laboratory in California today range in size from 1.5 times the radius of the Earth to bigger than Jupiter. But more work will be required to tell which are rocky worlds like Earth and which have thick gaseous atmospheres.

The planets, which all lie closer to their parent stars than Venus does to the Sun, have “years” or orbital periods of between six and 143 days. Each of the newly confirmed planetary systems contains between two and five closely packed worlds.

Kepler scientists Doug Hudgins, of NASA HQ in Washington, said: “Prior to the Kepler mission, we knew of perhaps 500 exoplanets across the whole sky. Now, in just two years staring at a patch of sky not much bigger than your fist, Kepler has discovered more than 60 planets and more than 2,300 planet candidates. This tells us that our galaxy is positively loaded with planets of all sizes and orbits.”

Previously, astronomers have had to use ground telescopes to confirm provisional discoveries by Kepler which was launched into space in March, 2009. But astronomers have developed a new technique to speed the process up by detecting how each star’s planets interact with each other.

Eric Ford, associate professor of astronomy at the University of Florida and lead author of the paper confirming Kepler-23 and Kepler-24, said: “We verified these planets using new techniques that dramatically accelerated their discovery.”

In tightly packed planetary systems, the gravitational pull of the worlds on each other causes some planets to accelerate and some to decelerate along their orbits. The acceleration causes the orbital period of each planet to change. Kepler detects this effect by measuring the changes, or so-called Transit Timing Variations.

Planetary systems with Transit Timing Variations can be verified without requiring extensive ground-based observations, accelerating confirmation of planet candidates. This detection technique also increases Kepler’s ability to confirm planetary systems around fainter and more distant stars.

“By precisely timing when each planet transits its star, Kepler detected the gravitational tug of the planets on each other, clinching the case for 10 of the newly announced planetary systems,” said Dan Fabrycky, Hubble Fellow at the University of California, and lead author for a paper confirming Kepler-29, 30, 31 and 32.

Five of the systems (Kepler-25, Kepler-27, Kepler-30, Kepler-31 and Kepler-33) contain a pair of planets where the inner planet orbits the star twice during each orbit of the outer planet. Four of the systems (Kepler-23, Kepler-24, Kepler-28 and Kepler-32) contain a pairing where the outer planet circles the star twice for every three times the inner planet orbits its star.

“These configurations help to amplify the gravitational interactions between the planets, similar to how my sons kick their legs on a swing at the right time to go higher,” said Jason Steffen, of the Fermilab Center for Particle Astrophysics in Batavia, Illinois, and lead author of a paper confirming Kepler-25, 26, 27 and 28.

Kepler-33, a star that is older and more massive than our sun, had the most planets. The system hosts five planets, ranging in size from 1.5 to 5 times that of Earth. All of its planets lie closer to their star than any planet is to our Sun.

These discoveries are announced in four different papers in the Astrophysical Journal and the Monthly Notices of the Royal Astronomical Society.