Back in 2011, comet Lovejoy boldly went where no spacecraft has gone before — straight through the Sun’s solar corona. Remarkably, it survived the close encounter and continued along its way to the outer solar system. Now, scientists have used the event to turn the comet into a veritable space probe.
Top image: A visualization of the coronal magnetic field through which comet Lovejoy passed in 2011. The thin magenta arc indicates Lovejoy's path, which travelled through open (orange) and closed (blue) magnetic field lines. Credit: Cooper Downs.
Known as a sungrazer comet, Lovejoy violated the Sun’s violent outer atmosphere on December 15, 2011. Scientists knew in advance that this flyby would happen, so they had their measuring equipment ready, including NASA’s Solar Dynamics Observatory and twin Stereo orbiters, as well as Japan’s Hinode spacecraft.
By watching a foreign object go through it, the scientists were hoping to glean information about the sun’s intense magnetic field. Needless to say, it was an unprecedented opportunity; no space probe would ever survive a journey that close. And in fact, most scientists suspected that Lovejoy wouldn’t survive either, but it did.
As Comet Lovejoy approached the sun, it moved at a blistering pace — about 400 miles (600 km) per second. It appeared as a bright speck with a long, glowing tail. As it got nearer to the sun, it got progressively brighter, reaching areas where the temperature exceeded millions of degrees Celsius.
But then something interesting happened: The comet’s tail began to swirl and wiggle. For a brief time, the tail did not follow the comet’s head as normally expected. Scientists say it got locked onto the sun’s magnetic field, and then it flicked back and forth. These movements were exactly the kind of thing the researchers were hoping for.
Scientists have since taken this information and applied it to computer models. They concluded that, in order to survive the encounter, Lovejoy had to be at least 1,600 feet in diameter. The research team, which included Cooper Downs, discovered that charged particles in the comet’s tail rippled while passing through the corona as it was affected by the area’s inhomogenous magnetic field. In turn, Downs’ team created a model, and a map, that explained the particles’ movements.
Read the entire study at Science: “Probing the Solar Magnetic Field with a Sun-Grazing Comet.”