New research hints at the presence of super-Earth planets beyond the orbit of Neptune.
The Last Mile
Using data from the Cassini spacecraft, we’ve now measured the position of Saturn accurate to within a mile.
The Martian Chronicles
Throughout history, determining the size of the solar system was a long-standing problem. Nearly two millennia ago Aristarchus measured the angle between the Moon and the Sun when the Moon was in its quarter phase (when half of it is illuminated from the Sun), and used trigonometry to determine that the Sun was about 20 times further away than the Moon. Some time later, Hipparchus used the parallax of the Moon to determine the Moon was about 60 times the radius of the Earth. These results weren’t particularly accurate, but they were the best to be had until at least the 1400s.
It’s Only a Model
When Johannes Kepler proposed a new model of the solar system in the early 1600s, it was a revolutionary idea. The model addressed many of the problems with earlier circular-orbit models, and greatly simplified the calculation of planetary motions. Still, the model was so radical that it wasn’t fully accepted until Newton was able to derive the model from his law of universal gravitation. What made Kepler’s model so powerful is that is required only three simple rules, which we now call Kepler’s laws.
Near and Far
Today marks the point in Earth’s orbit where it is closest to the Sun, known as perihelion. It might seem odd for those in the northern hemisphere for this to occur in the middle of winter, but that’s because the seasons are due largely to the tilt of Earth’s axis relative to its orbital plane. The variation in Earth’s distance from the Sun is minor in comparison, because Earth’s orbit is almost (but not quite) a perfect circle.
Close Encounters of the Stellar Kind
A star known as HIP 85605 is on a collision course with our solar system. Not a collision course as in Armageddon, or When Worlds Collide, but rather on a path to come within 0.04 parsecs of the Sun. That might seem close, but that would make it more than 8,000 times more distant than Earth at its closest approach (8,000 AU). Distant Eris is only 100 AU by comparison. Given that stellar distances are typically measured in light years, and this encounter would be only 50 light days away, that’s remarkably close by astronomical standards. This close encounter won’t occur for another 400,000 years or so. Currently HIP 85605 is about 16 light years away, so we have time to plan for its visit. But it does raise an interesting question as to how such a close encounter could affect our solar system.
Tis the Season
Today marks the Winter Solstice for those of us in the northern hemisphere, and Summer Solstice for those in the southern hemisphere. While the solstice is often assumed to be the shortest (or longest) day of the year, though the complexity of planetary motion means that isn’t quite the case. It does, however, mark the lowest (or highest) transit of …
Past Pluto
New Horizons is a small spacecraft on its way to Pluto. It will make its closest approach next Summer. To get to Pluto in a reasonable time, the spacecraft is heading there at high speed. This means it will zip past Pluto and head out into the Kuiper belt. While Pluto is a worthy goal, it would be nice if New Horizons could observe other objects in the outer solar system. But given the high speed of the spacecraft, and the low mass of Pluto, there isn’t a good way to use the planet’s gravity to change direction towards a particular Kuiper belt object (KBO). Basically, New Horizons is on a straight trajectory out of the solar system. So instead astronomers have been searching for KBOs that are along the path of New Horizons, and they’ve found some candidates.
Magnetic Meteorites
Recently a paper in Science looked at the magnetic properties of a primitive meteorite known as Semarkona, and discovered a surprising fact about the early solar system.