October has always been my favorite month for observing, as the month usually offers the best observing weather of the year. The longer, cooler nights also allow for almost an entire year’s worth of sky to be seen in one night—if you can stay awake!
Archive for the 'Astronomy' Category
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Many apologies for being about a week late on this article. Hard to believe that a week of September has already passed us by…
Hilarious Photoshop contest over at Worth1000: “Promote and advertise the ninth planet.”
**UPDATED**: A previous version of this post contained inaccurate information (thank you, BBC and NPR). What follows is straight from the horse’s mouth – the IAU.)
We have 12 planets now.
As I wrote a couple of months ago, the International Astronomical Union met this summer to finally define what a “planet” is. At issue is the quandary that many astronomers find themselves in today. Objects bigger than Pluto have been found, but to date, they’ve been assigned identifiers that classify them with asteroids, comets, and the like.
This created a problem for astronomers: If there are objects bigger than Pluto that are not considered planets, then why is Pluto still considered one?
The IAU has proposed a resolution that will be refined and voted on during the meeting of 24 August. Here are a few relevant snips from that resolution:
The IAU therefore resolves that planets and other Solar System bodies be defined in the following way:
- A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet.
- We distinguish between the eight classical planets discovered before 1900, which move in nearly circular orbits close to the ecliptic plane, and other planetary objects in orbit around the Sun. All of these other objects are smaller than Mercury. We recognize that Ceres is a planet by the above scientific definition. For historical reasons, one may choose to distinguish Ceres from the classical planets by referring to it as a “dwarf planet.”
- We recognize Pluto to be a planet by the above scientific definition, as are one or more recently discovered large Trans-Neptunian Objects. In contrast to the classical planets, these objects typically have highly inclined orbits with large eccentricities and orbital periods in excess of 200 years. We designate this category of planetary objects, of which Pluto is the prototype, as a new class that we call “plutons”.
- All non-planet objects orbiting the Sun shall be referred to collectively as “Small Solar System Bodies”.
What this means is that we now have the following 12 planets:
- Classical planets – Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune
- Plutons – Pluto, Charon, and 2003 UB313 (proposed name: Xena)
- Dwarf planets – Ceres
Our new solar system, courtesy the IAU. Click to embiggenate.
I used to be split on this one. I never felt that it was appropriate to classify an object incorrectly just because it was sentimental to do so. Otherwise, what is the purpose of classifying objects at all?
But I am pleasantly surprised that, instead of wasting time arguing over whether or not certain objects should be ‘promoted’ or ‘demoted,’ the IAU addressed the root of the problem by coming up with a proper definition for a planet, and creating new sub-classes that define its members. It’s an opportunity to be more precise, and specific.
And that’s cool.
Image credit & copyright: “Artist’s Representation of Xena,” BBC News. Original caption: “At 3,000km (1,860 miles), the object is significantly bigger than Pluto.”
Do methane lakes exist on Titan? The Cassini spacecraft orbiting Saturn has returned data and imagery indicating that it is a possibility.
I found myself imagining what a methane lake would look like from the shoreline… frigid, viscous liquid; hissing a drizzly mist as Titan’s strong winds rolled over it; with Titan’s yellow mist blurring the sky and scattering sunlight everywhere:
If you want the image for desktop wallpaper, choose your size and download:
Note: to find out which version to use, right-click on your desktop and select Properties. Click the Settings tab, and note the setting in the Screen Resolution box.
If you are using Internet Explorer, once the image appears, you must mouse off of the image. When you mouse back over the image, an Expand box will appear in the lower-right corner of the screen. Click it. After the image returns to 100%, right-click the image, and select Set as Background.
Ahhh… the dog days of summer have arrived. Ever wonder where the term “dog days” comes from?
Over the course of a year, the Sun makes one complete circuit against the background of constellations (from our vantage point on Earth). Imagine it this way: Say you place a lamp in the center of a room, and walk around it. The walls of the room are covered in pictures. Now, if you keep your eyes fixed on the walls around and beyond the lamp as you go around it, at one point or another, you will see the lamp in the same field of view as every picture in the room.
In this context, you are the Earth “orbiting” the lamp, or Sun. The “pictures” are the constellations in our sky. Therefore, over the course of the year, the Sun appears to make a complete circuit against the background of constellations.
So, what does this have to do with the “dog days” of summer? Well, one of the “pictures” in our sky is the constellation Canis Major, the Big Dog. It’s primary member is the star Sirius, which is the brightest star (other than the Sun) in our sky. Sirius is so bright, in fact, that ancients believed that it wasn’t a coincidence that the hottest days of the year happened when the Sun and Sirius rose and set together. They felt that Sirius “added” to the heat from the Sun, and nicknamed the days when that occurred after Sirius – the Dog’s Star.
In this era of space telescopes, satellites, and Photoshop, it’s easy to forget that only a few decades ago, we had no idea of what space actually looked like. The task of communicating the wonders of space was left to the dreamers and artists, and we depended on them to stir our imaginations and passion for the universe.
Men like Chesley Bonestell and Jack Coggins took paint to canvas and created worlds and vistas that existed at the limits of imagination. Some of their art was eerily prescient, some of it was dead wrong, and some of it seemed to make no sense whatsover. Occasionally space was presented as a terrifying place. Occasionally, it was presented with whimsy. Nevertheless, these artists were the first space explorers, and they don’t get enough credit for it. Their work influenced a generation of young children to grow up and become scientists, engineers, explorers, and dreamers.
This wonderful collection of pre-space age art was gleaned from children’s books going all the way back to the late 19th century. Take a look and see if any of these look familiar to you. Even I was able to find a bunch that I owned as a young spaceMonkey.