What’s the excitement about? Do we have a replacement for Pluto?
Earlier this week, astronomers Konstantin Batygin and Mike Brown of the California Institute of Technology (Caltech) in Pasadena, U.S., reported in the peer-reviewed Astronomical Journal that a body as big as Neptune — but as yet unseen — orbits the Sun every 15,000 years. Mr. Brown was among those who played a pivotal role in downgrading Pluto from ‘planet’ to a mere ‘dwarf planet’ and so his championing for Planet Nine is being taken quite seriously by the astronomer community. Then again, unless there’s visual confirmation, we don’t have a new planet.
How big is it?
The object, which the researchers have nicknamed Planet Nine, has a mass about 10 times that of Earth and orbits about 20 times farther from the Sun on average than does Neptune (which orbits the Sun at an average distance of 2.8 billion miles). In fact, it would take this new planet between 10,000 and 20,000 years to make just one full orbit around the Sun.
How long has the search for such planets been on?
The search for planets beyond Uranus has an over 150-year-old history. Based on the peculiar movements in the orbit of that planet, astronomers felt there had to be a heavy body that was causing these skewed movements and presto, Neptune was found in the mid 19th century. But that still wasn’t enough. Among the several objects found beyond Neptune — in a region that is now known as the Kuiper belt — the most prominent was Pluto, discovered by Clyde Tombaugh, in 1928. But decades of data later suggested that Pluto was too small to be a proper planet and there were bigger objects that could be better contenders.
Why is the Batygin-Brown duo so confident about their potential discovery?
According to a news report in Science, the duo inferred Planet Nine’s presence from the way six Kuiper objects orbit. They say there’s only a 0.007 per cent chance, or about one in 15,000, that the clustering could be a coincidence. Instead, they say, a planet with the mass of 10 Earths has forced the six objects into their strange elliptical orbits, tilted out of the plane of the solar system.
The orbit of the inferred planet is similarly tilted, as well as stretched to distances that will explode previous conceptions of the solar system. Its closest approach to the Sun is seven times farther than Neptune, or 200 astronomical units (AUs). (An AU is the distance between Earth and the Sun, about 150 million kilometres.)
Can we ever see Planet Nine?
Icy and cold definitely but over at Wired, Rhett Allain has made some back-of-the-envelope calculations to suggest that if Nine were to be at its closest to our Sun, it would take 63 years for a spacecraft like New Horizons (that flew past Pluto last year) to fly past it. That’s the best shot and at worst, it could be around 300 years.
