C/2007 N3 (Lulin)

Lore & Background

The comet was first photographed by astronomer Lin Chi-Sheng with a 0.41-metre telescope at the Lulin Observatory in Nantou, Taiwan on July 11, 2007. However, it was the 19-year-old Ye Quanzhi from Sun Yat-sen University in China who identified the new object from three of the photographs taken by Lin. Initially thought to be a magnitude 18.9 asteroid, images taken a week later with a larger 0.61-metre telescope revealed the presence of a faint coma. The discovery occurred as part of the Lulin Sky Survey project to identify small objects in the Solar System, particularly Near-Earth Objects. The comet was named after the observatory.

The comet became visible to the naked eye from dark-sky sites around February 7. It figured near the double star Zubenelgenubi on February 6, near Spica on February 15–16, near Gamma Virginis on February 19, and near the star cluster M44 on March 5 and 6. It also figured near the planetary nebula NGC 2392 on March 14, and near the double star Wasat around March 17. The comet was near conjunction with Saturn on February 23, and outward-first headed towards its aphelion in the direction of Regulus in the constellation of Leo, as noted on February 26–27, 2009. It passed near Comet Cardinal on May 12, 2009.

According to NASA, Comet Lulin's green color comes from a combination of gases that make up its local atmosphere, primarily diatomic carbon, which appears as a green glow when illuminated by sunlight in the vacuum of space. When SWIFT observed comet Lulin on January 28, 2009, the comet was shedding nearly 3,000 litres of water each second. Comet Lulin was methanol-rich. On February 4, 2009, a team of Italian astronomers witnessed a disconnection event in which part of the comet's plasma tail was torn away, believed caused by a magnetic disturbance in the solar wind hitting the comet.

Reader's Guide

Comet Lulin's significance lies in its combination of notable characteristics: it was a naked-eye comet with a distinctive green hue, it exhibited a rare disconnected tail event, and it was discovered by a young amateur astronomer in collaboration with a professional. The comet's green color, attributed to diatomic carbon, made it visually striking to observers. The disconnection event on February 4, 2009, where part of its plasma tail was torn away by a magnetic disturbance in the solar wind, provided a dramatic demonstration of comet-solar wind interactions, similar to an event observed with Comet Encke in 2007. Its orbit, calculated by astronomer Brian Marsden, is very nearly a parabola, with an eccentricity of 0.999986 at epoch 2009 and 0.999998 at epoch 2010, moving in a retrograde orbit at a low inclination of 1.6° from the ecliptic. The barycentric orbital elements for epoch 2014-Jan-01 give a semi-major axis of about 1,200 AU and a period of about 42,000 years. The comet's methanol-rich composition and high water output (nearly 3,000 litres per second as observed by SWIFT) added to scientific interest. Its legacy includes being a well-observed object that contributed to understanding of cometary composition and dynamics, and it remains a memorable example of a green, two-tailed comet that passed relatively close to Earth.

Did You Know?

• Comet Lulin was discovered by 19-year-old Ye Quanzhi from Sun Yat-sen University, who identified it from photographs taken by Lin Chi-Sheng.
• Its green color comes primarily from diatomic carbon illuminated by sunlight in the vacuum of space.
• The comet's orbit is very nearly parabolic, with an eccentricity of 0.999986 at epoch 2009, and it has a barycentric orbital period of about 42,000 years.