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Explanation: There it goes. That small spot moving in front of background stars in the above video is a potentially dangerous asteroid passing above the Earth's atmosphere. This past Friday, the 50-meter wide asteroid 2012 DA14 just missed the Earth, passing not only inside the orbit of the Moon, which is unusually close for an asteroid of this size, but also inside the orbit of geosynchronous satellites. Unfortunately, asteroids this big or bigger strike the Earth every 1000 years or so. Were 2012 DA14 to have hit the Earth, it could have devastated a city-sized landscape, or stuck an ocean...

Current and planned efforts focus on larger objects Scientists have begun piecing together the characteristics of the meteor that exploded over Russia on the morning of February 15, using data from seismic instruments that track earthquakes and microphones designed to detect sonic booms from nuclear explosions. Unlike the asteroid DA14, which narrowly but predictably missed Earth later that day, the meteor was too small to detect before its contrail appeared in the dawn skies over the Russian city of Chelyabinsk. Yet even an object too small to detect can produce an impressive amount of destruction. The meteor was 15 meters...

Explanation: For now, Comet Lemmon (C/2012 F6a), and Comet PanSTARRS (C/2011 L4) are sweeping through southern skies. Lemmon's lime green coma and thin tail are near the left edge of this telephoto scene, a single frame from a timelapse video (vimeo here) recorded on February 12, tracking its motion against the background stars. Comet Lemmon's path brought it close to the line-of-sight to prominent southern sky treasures the Small Magellanic Cloud and globular cluster 47 Tucanae (right). Sporting a broader, whitish tail, Comet PanSTARRS appears in later video frames moving through the faint constellation Microscopium. Visible in binoculars and small...

Explanation: Two dark shadows loom across the banded and mottled cloud tops of Jupiter in this sharp telescopic view. In fact, captured on January 3rd, about a month after the ruling gas giant appeared at opposition in planet Earth's sky, the scene includes the shadow casters. Visible in remarkable detail at the left are the large Galilean moons Ganymede (top) and Io. With the two moon shadows still in transit, Jupiter's rapid rotation has almost carried its famous Great Red Spot (GRS) around the planet's limb from the right. The pale GRS was preceded by the smaller but similar hued...

A series of explosions in the skies of Russia’s Urals region, reportedly caused by a meteorite shower, has sparked panic in three major cities. Witnesses said that houses shuddered, windows were blown out and cellphones have stopped working. According to unconfirmed reports, the meteorite was intercepted by an air defense unit at the Urzhumka settlement near Chelyabinsk. A missile salvo reportedly blew the meteorite to pieces at an altitude of 20 kilometers.

Explanation: On another Valentine's Day (February 14, 1990), cruising four billion miles from the Sun, the Voyager 1 spacecraft looked back to make this first ever family portrait of our Solar System. The complete portrait is a 60 frame mosaic made from a vantage point 32 degrees above the ecliptic plane. In it, Voyager's wide angle camera frames sweep through the inner Solar System at the left, linking up with gas giant Neptune, at the time the Solar System's outermost planet, at the far right. Positions for Venus, Earth, Jupiter, Saturn, Uranus, and Neptune are indicated by letters, while the...

Explanation: The Great Nebula in Orion is a intriguing place. Visible to the unaided eye, it appears as a small fuzzy patch in the constellation of Orion. But this image, an illusory-color composite of four colors of infrared light taken with the Earth orbiting WISE observatory, shows the Orion Nebula to be a bustling neighborhood or recently formed stars, hot gas, and dark dust. The power behind much of the Orion Nebula (M42) is the stars of the Trapezium star cluster, seen near the center of the above wide field image. The eerie green glow surrounding the bright stars pictured...

Astronomers using the Hubble Space Telescope discovered a fourth moon orbiting the icy dwarf planet Pluto. The tiny, new satellite -- temporarily designated P4 -- was uncovered in a Hubble survey searching for rings around the dwarf planet. The new moon is the smallest discovered around Pluto. It has an estimated diameter of 8 to 21 miles (13 to 34 km). By comparison, Charon, Pluto's largest moon, is 648 miles (1,043 km) across, and the other moons, Nix and Hydra, are in the range of 20 to 70 miles in diameter (32 to 113 km). "I find it remarkable that...

Three years ago, the IAU decided to draw up the first scientific definition of the term planet. After days of stormy arguments at its general assembly in Prague, the delegates voted for a definition that excluded Pluto, downgrading it to the new category of dwarf planet. The decision caused outrage among many members of the public who had grown up with nine planets, and among some astronomers who pointed out that only 4 per cent of the IAU's 10,000 members took part in the vote. The governors of Illinois saw the decision as a snub to Pluto's discoverer, Clyde Tombaugh,...

According to a strict interpretation of the IAU definition of a planet we're stuck with eight major planets in the entire galaxy. No, wait, the entire freaking universe! No more, no less. Not ever, not never. Why? Because the IAU definition ignores the over 400 planets to date that have been found orbiting other stars. This month alone 25 new exoplanets were announced at the meeting of the American Astronomical Society in Washington D.C. The dirty little secret is that the Pluto-antagonists needed the vote of the exoplanet research community to pass their Pluto-is-not-a-planet resolution. Therefore they steered clear of...

The International Astronomical Union has decided on the term "plutoid" as a name for Pluto and other objects that just two years ago were redefined as "dwarf planets."

Pluto has suffered yet another blow to its status. Not only has it been demoted from planet to "dwarf planet", research now shows that it cannot even lay claim to being the biggest of these. A study has confirmed that the dwarf planet Eris - whose discovery prompted Pluto's relegation from planet to dwarf - outranks it in mass. snip

"IAU presented the resolution to its General Assembly on August 16, giving the roughly 2500 attendees more than a week to discuss it. But the committee expected clear sailing...Instead, the '12-planet proposal' went down in flames. Critics objected that planets should also be defined by their orbital dynamics, not just by their size and shape. All eight 'major' planets, they pointed out, were massive enough to sweep up, fling away, or gravitationally control all the debris in their parts of the early solar sys[t]em, but Ceres and Pluto [and other candidate 'planets' among Kuiper Belt Objects] were not... the absurdity...

I understood his travail. When I was a kid, I had a favorite planet. It seemed that all my friends did. Mine, for a reason I can no longer put my finger on, was Venus. I still recall a schoolyard fray in which I faced off against a kid who was ballyhooing the case for Jupiter as the "best" planet. The volume of recriminations rose to the point where a crowd gathered and one of the teachers had to separate us. Who knew that astronomy could stoke such passions? ...The thing is, like that long-ago schoolyard standoff pitting Venus against...

Last month, Catherine Cesarsky became the president of the International Astronomical Union (IAU). Cesarsky, the first woman to hold this prestigious position, started her presidency at a time when many scientists are questioning IAU's recent decision to strip Pluto of its planetary status based on a vote of just 424 members at a meeting in Prague. Cesarsky served as the director general of the European Southern Observatory since 1999 and is famed for her research work in central areas of modern astrophysics. She also led the design and construction of the ISOCAM camera onboard the Infrared Space Observatory (ISO) of...

News leaks about the planet definition began to spout late this week, as the authors prepared to present a draft resolution to the IAU's executive committee Sunday in Prague. The IAU is the official arbiter of all issues related to astronomical nomenclature. In a story that aired Thursday, unnamed sources told National Public Radio the proposed definition would include Pluto in a new class of small planets. A source also told the Rocky Mountain News on Thursday that a member of the seven-person definition panel said Pluto will remain a planet. IAU Vice President Bob Williams described the reports as...

Earlier this year, the BBC interviewed Mrs Venetia (Burney) Phair, the only living person to have named a planet... The IAU decision was political. Scientists voted to demote Pluto to the status of "dwarf planet." ...In California, of course, the real politicians found a reason for action in Pluto's demotion. While there are many more serious problems--over crowded schools and universities, decayed freeways, and the health care crisis, just to name a few—fifty-four of our esteemed elected officials found the time and energy for a Resolution that supports Pluto's status as a full-fledged planet. They call the IAU "mean-spirited" for...

LOS ANGELES - Scientists say they have confirmed that a so-called 10th planet discovered last year is bigger than Pluto, but that likely won't quell the debate over what makes a planet. The astronomers who spotted the icy, rocky body — informally called UB313 — had reported only a rough estimate of its size based on its brightness. But another group of researchers has come up with what is believed to be the first calculation of UB313's diameter. By measuring how much heat it radiates, German scientists led by Frank Bertoldi of the University of Bonn estimated that UB313 was...

Having Pups Over Pluto And The Planetary Misfits Of The Kuipers Ask any kid how many planets are in our solar system, and you'll get a firm answer: nine. But knock on a few doors in Berkeley's astronomy department, and you'll hear, amid the hemming and hawing, a whole range of numbers. Professor Gibor Basri, who plans soon to propose a formal definition of a planet to the international body that names astronomical objects, argues that there are at least 14 planets, and perhaps as many as 20. To the well-known list of nine he adds several large asteroids and...

Add a 10th planet to the solar system - or possibly subtract one. Astronomers announced today that they have found a lump of rock and ice that is larger than Pluto and the farthest known object in the solar system. The discovery will likely rekindle debate over the definition of "planet" and whether Pluto should still be regarded as one. The new object - as yet unnamed - is currently 9 billion miles away from the Sun, or about three times Pluto's current distance from the Sun. But its 560-year orbit also brings it as close as 3.3 billion miles....