Astronomers have discovered two new, unfamiliar alien worlds that are much larger than the planet Earth. The newly minted exoplanets, known as the cosmic bodies HD 7924c and HD 7924d, are "super-earths" with masses about 7, 9 and 6, 4 times the weight of our home planet, as the researchers argue. The above planets revolve around their star called HD 7924, which, according to preliminary calculations, is about fifty-four light years from the Sun — a very short distance, given the length of the Milky Way, which is approximately 100,000 light years.
This discovery extends to three a number of known planets in the HD 7924 system (another super-earth, called HD 7924b, was seen there in the not-so-long 2009). It is known that HD 7924b, HD 7924c, and HD 7924d are closer to their star than Mercury to our Sun. They complete one orbit in five, fifteen, and twenty-four days, respectively, as the researchers say. "These three planets are different from everything in our solar system, with masses seven to eight times the mass of Earth and orbits, and which are located very close to their star," said Lauren Weiss, co-author and graduate student of the University of California, Berkeley, in a statement .
The research team discovered HD 7924c and HD 7924d using three different ground objects — Automated Planet Finder (APF) —the Lick Observatory telescope in California, the Keck Observatory in Hawaii, and the Automated Photometric Telescope (APT) at Fireborn Observatory in Arizona (HD 7924b was discovered by the Keck Observatory in 2009).
The research team, led by BJ Fulton, a graduate student at the University of Hawaii, used combined observations from three telescopes to detect small vibrations in HD 7924 caused by the gravitational pull of these two new-found planets, and then to check for life.
"Star spots, like spots on the Sun, can instantly imitate the signatures of minor planets," says co-author Evan Sinyukov, also a UH graduate student. "Repeated observations over the years have allowed us to separate the spot signals from the signatures of these new planets." The APF telescope was recently updated and fully robotic, and now it can easily search for exoplanets in the sky without human supervision — this fact is a key milestone in the ongoing exoplanet hunt, the researchers said.
"This level of automation has changed the rules of the game in astronomy," said co-author Andrew Howard, an astronomer at UH. "It’s a bit like owning a car without a driver who is self-employed on planetary shopping."
In 1992, astronomers first discovered planets orbiting another star, and the number of exoplanets increased to nearly 2000. More than half of these unfamiliar alien worlds were discovered by the Kepler telescope, the NASA space telescope launched in March 2009.
