Comet Lulin
Encyclopedia
Comet Lulin is a non-periodic comet. It was discovered by Ye Quanzhi and Lin Chi-Sheng from Lulin Observatory
. It peaked in brightness and arrived at perigee
for observers on Earth
on February 24, 2009, at magnitude
+5, and at 0.411 AU
from Earth. The comet was near conjunction with Saturn
on February 23, and passed near Regulus
in the constellation
of Leo
on February 26 and 27, 2009. It was expected to pass near Comet Cardinal on May 12, 2009. The comet became visible to the naked eye from dark-sky sites around February 7. It passed near the double star
Zubenelgenubi on February 6, near Spica
on February 15 and 16, near Gamma Virginis
on February 19 and near the star cluster
M44 on March 5 and 6. It also passed near the planetary nebula
NGC 2392 on March 14, and near the double star
Wasat
around March 17. 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.
Lin Chi-Sheng (林啟生) with a 0.41 metres (16.1 in) telescope at the Lulin Observatory in Nantou
, Taiwan
on July 11, 2007. However, it was the 19-year old Ye Quanzhi (葉泉志) from Sun Yat-sen University
in China who identified the new object from three of the photographs taken by Lin.
Initially, the object was thought to be a magnitude 18.9 asteroid
, but images taken a week after the discovery with a larger 0.61 metres (24 in) 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 Object
s. The comet was named "Comet Lulin" after the observatory, and its official designation is Comet C/2007 N3.
of the Smithsonian Astrophysical Observatory
calculated that Comet Lulin reached its perihelion on January 10, 2009, at a distance of 113 million miles (182 million kilometers) from the Sun
.
The orbit of Comet Lulin is very nearly a parabola
(parabolic trajectory
), according to Marsden. The comet had an epoch
2009 eccentricity of 0.999986, and has an epoch 2010 eccentricity of 0.999998. It is moving in a retrograde orbit
at a very low inclination of just 1.6° from the ecliptic
.
Given the extreme orbital eccentricity
of this object, different epochs
can generate quite different heliocentric unperturbed two-body
best-fit
solutions to the aphelion distance (maximum distance) of this object. For objects at such high eccentricity, the Suns barycentric coordinates
are more stable than heliocentric coordinates. Using JPL Horizons, the barycentric orbital elements for epoch 2014-Jan-01 generate a semi-major axis of about 1200 AU and a period of about 42,000 years.
Guido and colleagues believe the event was caused by a magnetic disturbance in the solar wind
hitting the comet. Magnetic mini-storms in comet tails have been observed before—most famously in 2007 when NASA's STEREO
spacecraft watched a coronal mass ejection
crash into Comet Encke
. Encke lost its tail in dramatic fashion, much as Comet Lulin did on February 4.
Lulin Observatory
Lulin Observatory is an astronomical observatory operated by the Institute of Astronomy, National Central University in Taiwan.It is located at the summit of Mount Lulin, on the border of Chiayi County and Nantou County, near Yushan National Park...
. It peaked in brightness and arrived at perigee
Perigee
Perigee is the point at which an object makes its closest approach to the Earth.. Often the term is used in a broader sense to define the point in an orbit where the orbiting body is closest to the body it orbits. The opposite is the apogee, the farthest or highest point.The Greek prefix "peri"...
for observers on Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
on February 24, 2009, at magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
+5, and at 0.411 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
from Earth. The comet was near conjunction with Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
on February 23, and passed near Regulus
Regulus
Regulus is the brightest star in the constellation Leo and one of the brightest stars in the night sky, lying approximately 77.5 light years from Earth. Regulus is a multiple star system composed of four stars which are organized into two pairs...
in the constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
of Leo
Leo (constellation)
Leo is one of the constellations of the zodiac. Its name is Latin for lion. Its symbol is . Leo lies between dim Cancer to the west and Virgo to the east.-Stars:...
on February 26 and 27, 2009. It was expected to pass near Comet Cardinal on May 12, 2009. The comet became visible to the naked eye from dark-sky sites around February 7. It passed near the double star
Double star
In observational astronomy, a double star is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope. This can happen either because the pair forms a binary star, i.e...
Zubenelgenubi on February 6, near Spica
Spica
Spica is the brightest star in the constellation Virgo, and the 15th brightest star in the nighttime sky. It is 260 light years distant from Earth...
on February 15 and 16, near Gamma Virginis
Gamma Virginis
Gamma Virginis is a star in the constellation Virgo. It has the traditional names Porrima, Postvarta and Arich....
on February 19 and near the star cluster
Star cluster
Star clusters or star clouds are groups of stars. Two types of star clusters can be distinguished: globular clusters are tight groups of hundreds of thousands of very old stars which are gravitationally bound, while open clusters, more loosely clustered groups of stars, generally contain less than...
M44 on March 5 and 6. It also passed near the planetary nebula
Planetary nebula
A planetary nebula is an emission nebula consisting of an expanding glowing shell of ionized gas ejected during the asymptotic giant branch phase of certain types of stars late in their life...
NGC 2392 on March 14, and near the double star
Double star
In observational astronomy, a double star is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope. This can happen either because the pair forms a binary star, i.e...
Wasat
Delta Geminorum
Delta Geminorum is a star in the constellation Gemini. It has the traditional name Wasat. The traditional name comes from the Arabic word for "middle"....
around March 17. According to NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
, Comet Lulin's green
Green
Green is a color, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 520–570 nanometres. In the subtractive color system, it is not a primary color, but is created out of a mixture of yellow and blue, or yellow and cyan; it is considered...
color comes from a combination of gases that make up its local atmosphere, primarily diatomic carbon
Diatomic carbon
Diatomic carbon is a diatomic molecule of carbon , which occurs in electric arcs; in comets, stellar atmospheres and the interstellar medium; and in blue hydrocarbon flames.-Chemistry:...
, which appears as a green glow when illuminated by sunlight
Sunlight
Sunlight, in the broad sense, is the total frequency spectrum of electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the Earth's atmosphere, and solar radiation is obvious as daylight when the Sun is above the horizon.When the direct solar radiation is not blocked...
in the vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...
of space.
Discovery
The comet was first photographed by astronomerAstronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using...
Lin Chi-Sheng (林啟生) with a 0.41 metres (16.1 in) telescope at the Lulin Observatory in Nantou
Nantou County
Nantou County is the second largest county of Taiwan. It is also the only landlocked county in Taiwan. Its name derives from the Hoanya Taiwanese aboriginal word Ramtau. Nantou County is officially administered as a county of Taiwan....
, Taiwan
Taiwan
Taiwan , also known, especially in the past, as Formosa , is the largest island of the same-named island group of East Asia in the western Pacific Ocean and located off the southeastern coast of mainland China. The island forms over 99% of the current territory of the Republic of China following...
on July 11, 2007. However, it was the 19-year old Ye Quanzhi (葉泉志) from Sun Yat-sen University
Sun Yat-sen University
Sun Yat-sen University, also unofficially referred to as Zhongshan University , is a prominent university located mainly in Guangzhou, China. The University is named after Dr...
in China who identified the new object from three of the photographs taken by Lin.
Initially, the object was thought to be a magnitude 18.9 asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
, but images taken a week after the discovery with a larger 0.61 metres (24 in) 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
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
, particularly Near-Earth Object
Near-Earth object
A near-Earth object is a Solar System object whose orbit brings it into close proximity with the Earth. All NEOs have a perihelion distance less than 1.3 AU. They include a few thousand near-Earth asteroids , near-Earth comets, a number of solar-orbiting spacecraft, and meteoroids large enough to...
s. The comet was named "Comet Lulin" after the observatory, and its official designation is Comet C/2007 N3.
Orbit
Astronomer Brian MarsdenBrian G. Marsden
Brian Geoffrey Marsden was a British astronomer born in Cambridge, England, and educated at The Perse School in Cambridge, New College, Oxford and Yale University. Dr...
of the Smithsonian Astrophysical Observatory
Smithsonian Astrophysical Observatory
The Smithsonian Astrophysical Observatory is a research institute of the Smithsonian Institution headquartered in Cambridge, Massachusetts, where it is joined with the Harvard College Observatory to form the Harvard-Smithsonian Center for Astrophysics .-History:The SAO was founded in 1890 by...
calculated that Comet Lulin reached its perihelion on January 10, 2009, at a distance of 113 million miles (182 million kilometers) from the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
.
The orbit of Comet Lulin is very nearly a parabola
Parabola
In mathematics, the parabola is a conic section, the intersection of a right circular conical surface and a plane parallel to a generating straight line of that surface...
(parabolic trajectory
Parabolic trajectory
In astrodynamics or celestial mechanics a parabolic trajectory is a Kepler orbit with the eccentricity equal to 1. When moving away from the source it is called an escape orbit, otherwise a capture orbit...
), according to Marsden. The comet had an epoch
Epoch (astronomy)
In astronomy, an epoch is a moment in time used as a reference point for some time-varying astronomical quantity, such as celestial coordinates, or elliptical orbital elements of a celestial body, where these are subject to perturbations and vary with time...
2009 eccentricity of 0.999986, and has an epoch 2010 eccentricity of 0.999998. It is moving in a retrograde orbit
Retrograde motion
Retrograde motion is motion in the direction opposite to the movement of something else, and is the contrary of direct or prograde motion. This motion can be the orbit of one body about another body or about some other point, or the rotation of a single body about its axis, or other phenomena such...
at a very low inclination of just 1.6° from the ecliptic
Ecliptic
The ecliptic is the plane of the earth's orbit around the sun. In more accurate terms, it is the intersection of the celestial sphere with the ecliptic plane, which is the geometric plane containing the mean orbit of the Earth around the Sun...
.
Given the extreme orbital eccentricity
Orbital eccentricity
The orbital eccentricity of an astronomical body is the amount by which its orbit deviates from a perfect circle, where 0 is perfectly circular, and 1.0 is a parabola, and no longer a closed orbit...
of this object, different epochs
Epoch (astronomy)
In astronomy, an epoch is a moment in time used as a reference point for some time-varying astronomical quantity, such as celestial coordinates, or elliptical orbital elements of a celestial body, where these are subject to perturbations and vary with time...
can generate quite different heliocentric unperturbed two-body
Two-body problem
In classical mechanics, the two-body problem is to determine the motion of two point particles that interact only with each other. Common examples include a satellite orbiting a planet, a planet orbiting a star, two stars orbiting each other , and a classical electron orbiting an atomic nucleus In...
best-fit
Curve fitting
Curve fitting is the process of constructing a curve, or mathematical function, that has the best fit to a series of data points, possibly subject to constraints. Curve fitting can involve either interpolation, where an exact fit to the data is required, or smoothing, in which a "smooth" function...
solutions to the aphelion distance (maximum distance) of this object. For objects at such high eccentricity, the Suns barycentric coordinates
Barycentric coordinates (astronomy)
In astronomy, barycentric coordinates are non-rotating coordinates with origin at the center of mass of two or more bodies.The barycenter is the point between two objects where they balance each other. For example, it is the center of mass where two or more celestial bodies orbit each other...
are more stable than heliocentric coordinates. Using JPL Horizons, the barycentric orbital elements for epoch 2014-Jan-01 generate a semi-major axis of about 1200 AU and a period of about 42,000 years.
Disconnected tail
On February 4, 2009, a team of Italian astronomers witnessed "an intriguing phenomenon in Comet Lulin's tail". Team leader Ernesto Guido explains: "We photographed the comet using a remotely-controlled telescope in New Mexico, and our images clearly showed a disconnection event. While we were looking, part of the comet's plasma tail was torn away."Guido and colleagues believe the event was caused by a magnetic disturbance in the solar wind
Solar wind
The solar wind is a stream of charged particles ejected from the upper atmosphere of the Sun. It mostly consists of electrons and protons with energies usually between 1.5 and 10 keV. The stream of particles varies in temperature and speed over time...
hitting the comet. Magnetic mini-storms in comet tails have been observed before—most famously in 2007 when NASA's STEREO
STEREO
STEREO is a solar observation mission. Two nearly identical spacecraft were launched into orbits that cause them to respectively pull farther ahead of and fall gradually behind the Earth...
spacecraft watched a coronal mass ejection
Coronal mass ejection
A coronal mass ejection is a massive burst of solar wind, other light isotope plasma, and magnetic fields rising above the solar corona or being released into space....
crash into Comet Encke
Comet Encke
Comet Encke or Encke's Comet is a periodic comet that completes an orbit of the Sun once every three years — the shortest period of any known comet...
. Encke lost its tail in dramatic fashion, much as Comet Lulin did on February 4.
External links
- APOD: February 27, 2009, Lulin and Saturn
- APOD: February 25, 2009, Two Tails of Comet Lulin
- 8 hour time sequence, from the live web cast
- Green Comet Approaches Earth, February 4, 2009
- C/2007 N3 (Lulin) Orbital elements
- Comet Lulin full-page finder charts
- Comet Lulin photo gallery
- Comet Lulin Comes Calling
- Sky Show Tonight: Green "Two-Tailed" Comet Arrives
- Time-Lapse Movie of Comet Lulin moving in the night sky, with stars steady
- Time-Lapse Movie of Comet Lulin moving in the night sky, with comet steady
- Drawing of Lulin's antitail structure
- Orbital simulation from JPL (Java) / Horizons Ephemeris