Six Planets Now Aligned in the Dawn Sky

If you get up any morning for the next few weeks, you’ll be treated to the sight of all the planets except Saturn arrayed along the ecliptic, the path of the sun through the sky. For the last two months, almost all the planets have been hiding behind the sun, but this week they all emerge and are arrayed in a grand line above the rising sun. Mercury, Venus, Mars, and Jupiter are visible, and you can add Uranus and Neptune to your count if you have binoculars or a small telescope.

This sky map of the six planets shows how they should appear at dawn to observers with clear weather and an unobstructed view. Astrologers have always been fascinated by planetary alignments, and the doomsayers of 2012 have been prophesying a mystical alignment on Dec. 21, 2012. The modern tools of astronomers, such as planetarium software, show otherwise: absolutely no alignment at any time in 2012. But they also reveal a beautiful alignment visible during the month of May this year.

Pluto Atmosphere Has Toxic Carbon Monoxide

As if being distant and frigid weren't enough, Pluto is cloaked in a puffy atmosphere that contains highly toxic carbon monoxide, new data confirms. Observations of the dwarf planet made more than a decade ago offered inconclusive evidence of carbon monoxide in Pluto's atmosphere. The new study—based on data from the James Clerk Maxwell Telescope in Hawaii—not only confirms the gas is there, it shows that the amount of carbon monoxide has doubled since 2000.

In general, Pluto's atmosphere is very thin—about a millionth the atmospheric pressure of Earth's—but it extends relatively far into space. The solid part of the planet is just 1,430 miles wide. The new study shows that Pluto's atmosphere has grown over the past decade from a height of about 62 miles to more than 1,864 miles—a quarter of the distance to Pluto's largest moon, Charon. The astronomers think the increase may be due to Pluto's extreme seasons.

Who Ate All the Planets? Blame the "Bloatars"

No one has ever seen anything quite like the nine stars spotted by the Hubble Space Telescope in a young cluster called NGC 3603. They are too cool to be ordinary stars, with analysis of their infrared light emissions indicating surface temperatures between 1700 and 2200 kelvin. By this measure, they are more like brown dwarfs, objects intermediate in mass between planets and fully fledged stars. Yet brown dwarfs are dim objects that should be too faint to detect at the cluster's distance from Earth - 20,000 light years.

They think the enigmatic objects are part of stellar systems that spawned planets - then hastily devoured them. Some planets are thought to spiral in towards their stars. That would explain why so many alien worlds have been found in star-hugging orbits. The team says that some may spiral so close that the star "eats" them - the star's gravity rips the planet apart and captures its debris. This captured debris would form a temporary outer atmosphere for the star, which would be cooler than the star's normal light-emitting surface. These bloated stars, or "bloatars", would also be bigger and brighter than brown dwarfs, explaining how they could be seen at such a great distance.

How to Sort the Dwarfs from the Planets

What's the difference between a planet and a brown dwarf? That can be a tricky question, because some objects straddle the conventional boundary between the two categories. Now the discovery that there is a dearth of cosmic bodies whose mass lies within a particular range could provide a clean dividing line between planets and brown dwarfs, which are heavier than planets but lighter than stars.

Objects are traditionally classed as planets if they have less than about 13 times the mass of Jupiter, and as brown dwarfs if they are heavier. Uncertainties in the measurement of mass make it hard to classify borderline objects this way. But when Johannes Sahlmann of the Geneva Observatory in Switzerland and colleagues surveyed brown dwarfs and planets orbiting stars, they found a dearth of objects between 25 and 45 times Jupiter's mass, but plenty of objects outside this range.