Discovery of Comet PANSTARRS (C/2011 L4)

Comet Panstarrs 2013


Credit: Panoramic Survey Telescope and Rapid Response System

Comet PANSTARRS (C/2011 L4) was discovered by the Panoramic Survey Telescope and Rapid Response System (“Pan-STARRS” or “PANSTARRS”) on June 6, 2011. How a comet gets its informal and formal name?


Comet PANSTARRS (C/2011 L4) was one of several comets in 2013 that reach perihelion - a list which included Comet ISON (C/2012 S1).


C/2011 L4 is one of many comets discovered by Pan-STARRS. Its mission on inception was to automatically detect Near Earth Objects (NEOs). The system has been wildly successful.


Pan-STARRS and other systems that automatically map the sky undoubtedly represent the future of comet discovery. LINEAR, Pan-STARRS, CSS and Spacewatch, which are all automated systems, were responsible for discovering over 98% of all Near Earth Objects detected in 2012.










Size of Comet PANSTARRS (C/2011 l4)


Studies of the gas and dust expelled from Comet PANSTARRS suggested the size of the nucleus was around 0.62 miles (1 kilometer) in diameter.



Observations of Comet PANSTARRS (C/2011 L4) by STEREO-B

The STEREO (A and B) spacecrafts were launched in the 2006 by NASA to study coronal mass ejections and the solar wind. They gradually fell into orbits around the Sun, which put them further from Earth than our Sun. Both satellites occasionally capture stunning comets which pass through their field of view. In mid-March of 2013, comet PANSTARRS put on a spectacular show for the SECCHI Heliospheric Imager-1 (HI-1) camera on the STEREO-B spacecraft.



Comet Panstarrs Stereo B


(on left) Positions of STEREO, A and B, relative to Earth and the Sun.

(on right) Image of Comet PANSTARRS (C/2011 L4) captured by STEREO B on March 13, 2013.




Comet PANSTARRS Orbital Path

Comet PANSTARRS (C/2011 L4) is orbiting the Sun with an inclination of 84.19° in relation to the ecliptic. C/2011 L4 was seen in the southern hemisphere in January and February of 2013.

As Comet PANSTARRS (C/2011 L4) moved north, from Earth perspective, it became visible in the northern hemisphere. It reached perihelion on March 10, 2013. Its "close" approach to the Sun took C/2011 L4 within 28,000,000 miles (45,061,632 km) of the Sun. At perihelion, Comet PANSTARRS reached an estimated apparent magnitude of 1, making it easily visible to naked eye. For comparison, Sirius is the brightest star in the night sky. It has an apparent magnitude of -1.4. So if Comet PanSTARRS (C/2011 L4) lives up to its potential it will be one of the brightest objects in the night sky.

After perihelion, Comet PANSTARRS began to fade, but the show was far from over. On March 12, 2013, the comet was roughly 5° removed from of a day-old crescent Moon. It traveled through the constellation Pisces, and then rose above the horizon with each passing night until, by mid-April, the comet no longer set on the western horizon (see movie above). Comet PANSTARRS (C/2011 L4) continued to move north and west, until it could no longer be seen with the naked eye in May of 2013. It disappeared from sight around the north star, Polaris.



Comet Panstarrs Orbit - 2 POVs


(on left) Orbit of Comet PANSTARRS (C/2011 L4) if solar system was seen top-down

(on right) Obrit of Comet PANSTARRS (C/2011 L4) compared to the ecliptic

Credit: Osamu Ajiki (AstroArts) modified by Ron Baalke (JPL)



Comet PANSTARRS' Orbital Period

Orbital path of Comet PANSTARRS (C/2011 L4) from 3/11/13-4/29/13. Point of view from Los Angeles. Click on icon in lower right corner to view full screen. Credit: Adapted from Stellarium

Some astronomers believe Comet PANSTARRS (C/2011 L4) will not be seen again, with the naked eye, for approximately 106,000 years.


Other astronomers believe Comet PANSTARRS has a parabolic orbit, and that it will never return be seen by people on Earth again.


What's a parabolic orbit? Most comets have an elliptical orbit, which means these comets orbit the Sun or, in rares cases, a planet repeatedly. However, a small number of comets have a parabolic or hyperbolic orbit. Where do comets come from? Basically some force, like a passing star, pushes comets from the Oort Cloud and Kuiper Belt into our inner solar system (i.e. inside Neptune).


In our inner solar system, a comet with a parabolic or hyperbolic orbit slingshots around our Sun only once. In other words, the gravity of our Sun cannot capture these comets and force them into an elliptical orbit. They are merely one-time visitors to our inner solar system, and will never to be seen again.


Hopefully, the had a chance to enjoy the show.