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.
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.
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.
Delta-V
Of all the inner planets, only Mercury hasn’t had a probe land on it. It likely won’t for quite some time. The reason isn’t because of lack of desire, or worthy science to be done, but because of a simple thing known as delta-v.
Touchdown
This week the Rosetta probe will release Philae to land on the comet 67P/Churyumov-Gerasimenko. It will be the first soft landing on a comet, but not the first probe to land on another world. Besides our homeworld, humans have walked on the surface of one other body and landed probes on five. If successful Philae will mark the 6th solar system object we’ve landed upon.
Approximate Pluto
Just how big is Pluto? The answer is we aren’t entirely sure. We know the diameter is between 2,300 and 2,400 kilometers, but it’s hard to pin down beyond that.