A star much older than the Sun but similar in mass has been found to have a planetary system unlike any we have yet seen: It has at least six gas giant planets, with two in the habitable zone. To the best of our knowledge, life can't exist on planets like these, as their solid core is so deep inside that atmospheric pressures are phenomenal. However, moons could be a different matter, and we've found yet another configuration in which planetary systems can exist.
HD 34445 is a G0 star, just 7 percent heavier than the Sun and slightly richer in metals. However, at almost twice the age (8.5 billion years), it is more evolved, emitting twice as much light and puffing up on route to becoming a red giant.
Such a familiar-looking star 150 light-years away, which is close on galactic scales, inevitably attracted the interest of planet hunters. Observations have been made for 18 years, enough time to detect the wobble caused by the orbit of planets further out than Jupiter in our own system. The discovery of one planet in 2010 inspired further interest, and now a different team have announced five more on arXiv.
The paper revealing the discoveries notes: “The HD 34445 planetary system... is fundamentally unlike either our own solar system... or the Kepler multiple-transiting systems.” Only Jupiter and Saturn have enough gravitational effect on the Sun as to produce wobbles of the size we see from HD34445's six planets. The systems Kepler has revealed are made up of planets far more closely packed around the star.
The first of HD 34445's planets to be discovered had an orbit lasting almost three years, marking a significant breakthrough in finding planets at distances approaching those of the gas giants in our own Solar System, rather than the “hot Jupiters” that dominated early discoveries.
The new discoveries include planets with orbits similar to Venus, Mars, and Mercury, as well as one closer in and another well past Jupiter's. There's a gap about where the Earth would be, but even if it contained a rocky planet, HD34445's extra light makes this region too hot to support liquid water.