The hunt is on for a gas giant up to four times the mass of Jupiter thought to be lurking in the outer Oort Cloud, the most remote region of the solar system. The orbit of Tyche (pronounced ty-kee), would be 15,000 times farther from the Sun than the Earth’s, and 375 times farther than Pluto’s, which is why it hasn’t been seen so far.
A recording of the ambient and oddly rhythmic sounds generated by the solar system’s largest planet Jupiter, made during the Voyager space probe fly-bys of the late 1970s… this would make for eerily great music while driving along a lonely road late at night, but also isn’t half bad to work to either.
Following the recent argument over what constitutes a planet – which famously saw Pluto downgraded in status a few years ago – debate is now raging over whether groups of stars should be considered galaxies when they may in-fact be star clusters instead.
Star clusters and galaxies both contain stars bound together by gravity, but while the members of a star cluster are thought to form simultaneously from a collapsing ball of gas, galaxies have richer histories. In the most popular cosmological model, they form along swathes of dark matter and contain enough gas to form many generations of stars. Yet the distinction is not always clear-cut. Take Omega Centauri, a round swarm of stars that orbits the Milky Way and is visible to the naked eye. It has long been classified as a star cluster, but there is now evidence that it contains multiple generations of stars, suggesting it is actually the remnant of a galaxy.
I hobbled back from the rocky beach up to the house. I woke Diane and told her that when the press called tomorrow I was going to have to tell them why the new proposed definition of planet was no good and why, in the end, it made sense all along for there to be just eight planets. I told her that I was going to have to kill Pluto and that Xena would go down as necessary and important collateral damage. All along, Diane had been more practical than I was. “Just let it be a planet,” she would say. “Try not to worry about it so much,” she had told me all year. “Relax” was her usual advice.
Following recent observations, doubt has been cast over the size of Eris, a dwarf planet orbiting the Sun at a (massive) distance of up to 14,510,993,390 kilometres, and previously thought to be bigger than Pluto, a finding that eventually resulted in Pluto being classed as a dwarf planet in 2006, after being regarded as a planet since its discovery in 1930.
Occultation measurements are by their nature very accurate, and although more precision is needed before we get a definitive answer, Eris is certainly a lot smaller than it was thought to be. “Almost certainly Eris has a radius smaller than 1,170 km [727 miles],” Bruno Sicardy, of the Paris Observatory, said in an email to Sky and Telescope Magazine. Pluto has a radius of approximately 1,172 kilometers (728 miles). Pluto therefore has an average density of 2.03 grams/cm3 and Eris has an average density of 2.5 grams/cm3.
While the new figures don’t show a great deal of variance in the size of either object, they could re-open the discussion over whether Pluto should continue to be regarded as a dwarf planet.
I want people to understand that this discovery is being touted as the first direct image of a planet around another star. It isn’t. Nor is it the first direct image of a planet orbiting a sun-like star. What this is is the first direct image of a planet orbiting a sun-like star taken using a ground-based telescope. While that may sound overly picky, it’s actually a significant achievement, and worth noting.
In the spring of 2009 the Kepler Mission conducted high precision photometry on nearly 156,000 stars to detect the frequency and characteristics of small exoplanets. Kepler studied an area in the constellation Cygnus, looking for the small changes in light that would signal a planet passing in front of its star.
While it is expected about half of these “candidate planets” will turn out to be other objects of some sort, given the relatively small area of the sky that Kepler scanned, it is likely the galaxy is teeming with such bodies.
It all made sense, except for one tiny problem: this same model also suggested that a little world like Earth shouldn’t exist at all; it (or more precisely, the Moon-size proto-planets that eventually assembled into the Earth) should have spiraled into the Sun more than 4 billion years ago. A star might not gobble a Jupiter whole when it moved close enough, but it could surely swallow a canapé like the proto-Earth.