Categorizing objects in the universe can be difficult. The fiasco with Pluto over the last decade is more than proof of that. We generally look to location and then to size as the two main methods for classifying the stuff that permeates the cosmos. Galaxies contain stars, which host orbiting planets, which host orbiting moons; While asteroids fly in between planets and icy comets are wander through the outskirts of star systems. But what about the in-between objects? Often we find strange things in strange places. There are moons in our solar system that are larger than planets. What would...
Since the Dawn spacecraft arrived at Ceres in March of this year, it has slowly been taking high resolution maps of the surface from several different altitudes. After each successive mapping run it moves into a closer orbit of the icy world for a higher resolution glimpse. After two successful mapping runs, we finally have a full high resolution topographic map of Ceres, revealing its cratered surface in unprecedented detail. With a quick look at the map, a couple of things become apparent immediately. For one, the surface craters are quite deep, and consistent with an icy crust. The size...
In the last few days, we have watched the intricate dance of Venus and Jupiter in the Western sky after sunset. They have tangoed and passed by one another and the world has watched as the best conjunction of the year has come and gone. Don’t forget that even though they appear close in the sky, Venus is actually closer to the Earth than it is to Jupiter. Jupiter is hundreds of millions of kilometers further away than Venus. Today’s APOD is a beautiful shot by Letian Wang combining the proximity of the two planets with the (much further East...
For the last few months, Venus and Jupiter have been visible in the night sky. Venus makes it’s usual 584 day cycle, becoming an ‘evening star’ once again, reaching far from the Sun in the West, while still following our central star. Jupiter has slowly worked its way westward over the past few months, due more in part to Earth’s orbit than Jupiter’s. Finally, the long-awaited conjunction of the planets is nigh, and it offers the best views and photographic opportunities of the year for professional and amateur astronomers alike. What is the brightest object in the sky? The Sun...
I presume that you know what a leap year is. A year is the amount of time the Earth takes to orbit the Sun, and is measured as 365 days, or 365 rotations of Earth. It is, in reality, a little bit longer. Each orbit of the Sun takes 365.25 days, or 365 days and six hours. So what do we do with that six hours? We ignore it for 3 years. On the fourth year we add up those extra hours and we get 24 hours, an extra day! So we add in February 29th every four years. This...
What is the brightest object in the sky? Why the Sun of course. Second brightest? The Moon. Most people are able to answer this question quite easily, but what is the third brightest? The fourth? Many people will confidently say Sirius, the brightest star in the sky, or Polaris the north star. The answer is that the planet Venus is third and the planet Jupiter is fourth. It shouldn’t be that surprising that planets hold these positions. They are much closer than the distant background of stars, and the human species has been observing them since the dawn of recorded...
As we are approaching the New Horizons bypass of Pluto just over a month from now, there is a lot of focus on the Plutonian system, from its strange Moons to its enigmatic surface. As we wait for the first ever high resolution images of the surface of Pluto, we can look to Hubble data to give us our fix. The best image of Pluto taken up to today, by Hubble, is blurry and at best can lead us to speculation about what we are seeing. But Hubble, as always, produces valuable science, and has given new insights into the...
A couple of days ago, the still-active Cassini spacecraft orbiting around Saturn performed a flyby of the small Moon Hyperion, taking high resolution photos of the surface, and showing the sponge-like surface of the moon in a different light. Hyperion is a moderate 250 kilometers wide, yet it doesn’t tug very hard on Cassini. Performing measurements of its surface gravity, Cassini has shown that the moon is mostly empty space, similar to a pumice stone on Earth. The odd shapes of the craters are thought to be a result of this. When an impactor hits Hyperion, it blows the material...
The Moon has clearly seen some stuff. It’s visibly heavily cratered across it’s surface, which has remained unchanged since it’s surface solidified 4.2 Billion years ago. Think about that – the Moon has been the same, with the exception of cratering, for 4 Billion years. This is a stark contrast to the Earth, whose erosion and tectonic activity cause the crust to change on scales of a few hundred million years. Astronomers have worked hard to learn about the early solar system by looking at the Moon and its cratering patterns. Most of the visible craters on the Moon are...
A long time ago in a galaxy far, far away…. Not just the star wars intro, but a true statement if you’re an astronomer. You see, once we start to look deep in space at the more distant objects in the universe, we are actually looking deep in time as well. It all begins with a light year. A light year is not a measure of time, it’s a measure of distance. When you turn on the light in a dark room, the light appears to fill the room instantly. But it actually takes a small amount of time, as light has...
