Astronomers know our solar system better than anyone else, but they still learn new ways in which it does not seem particularly common.
Such a lashing, in patterns of planet sizes, was the subject of a press conference held yesterday (January 8) at the American Astronomical Society's annual meeting. The results can lead to researchers re-examining a leading theory of how planets form.
And that in turn can have serious consequences for the search for life beyond our solar system. "Planetary theory is quite important even if you are only interested in habitable planets because it is not just enough to have a planet in the habitable zone, you must have chemicals that are compatible with life and a story that is in line with life's development, says David Bennett, an astronomer at the University of Maryland, at a press conference held during the meeting, "The better we can understand planet formation, the better we can predict which planets can be habitable." [7 Ways to Discover Alien Planets]
Right now, the leading theory of planetary formation, called the "core connection model", tailor-made to explain what we see in our solar system ̵
Take, for example, the dizzying size between Neptune and Saturn. un is about 17 times the Earth's mass, while Saturn is much larger at 95 times the Earth's mass, according to NASA. In between nothing The core application model explains that the gap with a mechanism called "runaway gas accretion".
Here's how the core connection model describes a gigantic birth. First, rock and ice clumps together and build up what becomes a core – maybe about 10 times the earth's mass. This core has sufficient gravity to slowly intervene on hydrogen and helium gas.
But during an evacuation gas model, once a development plan has slowly pulled together another 10 soil masses or so gas, something slightly changed. The process becomes overwhelming, with the planet faster in what other gases are nearby until the source expires.
If this idea is correct, it explains the gulf between Neptune and Saturn – Uranus and Neptune never hit the decisive size to trigger the ongoing gas rise, while Saturn and Jupiter made and bulked up to huge masses.
There is only one problem: Astronomers have realized that other solar systems host many planets with sizes between these extremes, the nickname sub-Saturner. A paper published in December in The Astrophysical Journal Letters and presented at the meeting compared 30 different planets identified with a specific technology with what researchers would expect to see based on the core application model. In that survey, they found that the model does not match very well with reality.
It gives our solar system a new weird look – its lacking sub-Saturns. "The lack of such planets in our own solar system is more likely to be due to random chance or an accident," says Bennett.
And the overall lack of such planets is that they are very difficult to detect. There is only one technique that is powerful enough to identify planets circling beyond what astronomers call the "snow line" where loose materials in an early solar system are far enough from their sun as bright materials that water can freeze – what kind of neighborhood you need to look for to find sub-saturns.
The technique, called gravity micro-purification, is dependent on a trick in the universe. When a very solid object passes exactly between an observer and a light source, gravity removes the light so that it appears to be enlarged. If the massive object is a solar system, scientists can fit on planets by looking for small anomalies in the observations. [Exoplanet Discovery: The 7 Earth-Sized Planets of TRAPPIST-1 in Pictures]
But usually they do not know much about the planet – just a feeling of how many times it is less than its sun. This is not the case for a sub-Saturn planet studied by many of the same researchers behind the survey. In that case, they could clean down just such a planet by relying on some patience and sharing their results in a second paper published in December in The Astronomical Journal.
The team returned a planet that had been identified by gravitational microlensing in 2012. Since the first observations, the celestial geometry has been distorted, with the planet's system and the light source enlarged from the alignment. The team could make an incredibly accurate measurement of how much the objects are shifted over the years since the planet identification, which they can then use to calculate a real mass for the planet, called OGLE-2012-BLG-0950.  That mass is located in prime sub-Saturn territory, at about 39 soil masses. That measurement points to a planet that cannot look like anything in our solar system. It is also an achievement in itself, that is, finding a dime from nearly 70 miles (110 kilometers) away. "It's a very difficult thing to do," said author Aparna Bhattacharya, an astronaut at NASA's Goddard Space Flight Center, during the press conference.
But it's not supposed to be a one-off, thanks to the planned Wide Field Infrared Survey Telescope, or WFIRST, which NASA will launch in the mid-2020s. That instrument will be able to use the same microlensing technique to identify and measure planets – and it will do so for hundreds of distant worlds. These measurements, in turn, can also reveal other weak points in our understanding of how planets form.