blog post photo
On this day in 2006, the International Astronomical Union decided that Pluto no longer should be considered a bona fide planet—a distinction it had held since 1930, when it was discovered by 23-year-old newbie astronomer Clyde Tombaugh.

Back then, Tombaugh’s discovery, made by analyzing photographic plates, confirmed a suspicion that astronomers had since the late 19th century, when they had calculated that the orbit of Uranus was being disturbed by the gravitational influence of another object besides Neptune. The hypothetical “planet X” turned out to be a rocky, icy orb 3,647,240,000 miles from the Sun, and only about a fifth of the size of the Earth’s Moon. Despire its unimpressive size, Pluto was installed as a full-fledged planet in the map of the solar system. (Its discovery also inspired Walt Disney to rename Mickey Mouse’s dog, who originally was called Rover, as Pluto, to take advantage of the hoopla.

Pluto remained a full-fledged planet for the next 76 years, and in 1978, astronomers even discovered that it had its own small moon, Charon. They later discovered two other satellites, Hydra and Nix, both just 100 miles across.

The advent of more powerful telescopes in the 1990s and 2000s, however, made astronomers change their view of Pluto. They realized that it was one of many small objects in a region called the Kuiper Belt at the edge of the solar system. In 2005, Caltech astronomer Mike Brown discovered another distant object, Eris, that was larger than Pluto—which raised the question of whether it should be named as a 10th planet.

Instead, in 2006, the IAU voted to change the definition of what a planet was. They decreed that a bona-fide planet had to orbit the Sun, have enough mass to pull itself into a spherical shape, and that it needed to have powerful enough gravity to either consume or repel smaller objects in its path. Pluto filled the first two requirements but flunked the third one, because it had too little mass. They decided to downgrade Pluto to the status called “dwarf planet,” the astronomical equivalent of the jayvee basketball team in high school. If it’s any consolation to Pluto lovers, scientists remain interested in the planet..er..dwarf, and the New horizons space probe is scheduled to visit it in 2015 and take the first close-up pictures of its surface. And while you’re speculating about what those images will look like, here are the science stories of the day.

Federal judge blocks Obama executive order allowing federal funding for embryonic stem cell research. However, as stem cell research opponents eventually will discover to their frustration, that train already has left the station. States such as California and big biotech firms are stepping in to fund the research.

Pulsar flashes help astronomers weigh planets. It’s a whole lot easier than sending a space probe.

Geoengineering schemes won’t be able to stop seas from rising, according to study.
 Too bad, too. Some of those crazy plans sounded kind of fun.

Potential HIV drug keeps virus out of cells. 
Which, in turn, would prevent it from hurting infected people.

Promiscuous bird species aren’t as cooperative. 
Turns out, avian Playaz are real deadbeats.

Chronic fatigue linked to moose virus. 
No wonder Rocky is keeping his distance from Bulwinkle these days.