☄ Lovejoy C/2014 Q2

How to follow comet Lovejoy live

The panel above recomputes the position of Lovejoy every second in your browser: its distance from the Sun and from Earth, its position in the sky (right ascension and declination). It runs on the same kind of engine observatories use, a Kepler solver applied to the JPL osculating orbital elements, so the numbers are not a static snapshot, they keep ticking.

Just below, the top-down map of the Solar System shows exactly where Lovejoy is right now among the planets. You can fast-forward time with the day slider, zoom and pan, compare its distance to another body with a click, and press "Next event" to jump straight to perihelion. It is the most direct way to grasp the orbit of Lovejoy with no math at all.

Comet fact sheet

About Lovejoy

C/2014 Q2, the fifth comet discovered by Australian amateur astronomer Terry Lovejoy, passed perihelion on 30 January 2015 at 1.29 astronomical units from the Sun, comfortably outside Earth's orbit. It still reached magnitude 4.0, visible to the naked eye under dark skies as an emerald-green fuzzy dot, and magnitude 3 under exceptional conditions. The green colour, unusual for naked-eye comets, made it a visual and photographic phenomenon through January and February 2015.

The importance of C/2014 Q2 goes well beyond the visual spectacle. Observations with the IRAM 30-metre radio telescope in the Pyrenees and the APEX submillimetre telescope in the Atacama revealed 21 different organic molecules in the coma, including ethanol and glycolaldehyde (a simple sugar), making it the comet with the greatest diversity of complex organic molecules detected at the time of those observations.

History and discovery

Terry Lovejoy, a software engineer and amateur astrophotographer from Queensland, Australia, discovered the comet on 17 August 2014 using an 8-inch (20 cm) reflector telescope fitted with an APS-C format CCD camera. It was his fifth comet discovery, making him one of the most prolific amateur comet finders of the digital era.

Lovejoy's comet list spans very different objects: C/2007 E2 (Lovejoy), C/2007 K5 (Lovejoy), C/2011 W3 (Lovejoy, the sungrazer that survived the solar corona in 2011), C/2013 R1 (Lovejoy), and this C/2014 Q2. The discovery of C/2014 Q2 came while Lovejoy was conducting a systematic wide-field survey of the southern sky, following methodology he had developed and refined over more than a decade of observing.

At discovery, the comet was 1.94 AU from the Sun at about magnitude 14, nothing exceptional. The orbit soon revealed a modest perihelion at 1.29 AU, with no extreme solar proximity, but with geometry favourable for observation from both hemispheres through the 2014-2015 season.

Orbit and nature

C/2014 Q2 has a long-period orbit with an original period estimated at about 11,000 years before entering the planetary region. After the passage, gravitational perturbations from Jupiter and Saturn modified the outbound orbit to a period of approximately 8,000 years, with aphelion around 800 AU from the Sun.

The nucleus radius was estimated at approximately 6 km from gas production rate analysis and coma morphology, placing C/2014 Q2 among the largest well-observed long-period comets of the modern era. The water production rate exceeding 20 tonnes per second at perihelion, measured by radio interferometry, is extraordinarily high for a comet that passed more than 1 AU from the Sun.

Nucleus, coma and tail

The intense green colour of C/2014 Q2's coma comes primarily from emission by diatomic carbon (C2) molecules excited by solar ultraviolet radiation, with contributions from cyanogen (CN) and other species. This fluorescence mechanism is known in comets but rarely produces a colour as saturated as Lovejoy displayed, owing to the high molecular production rate combined with favourable viewing geometry.

Observations with the IRAM 30-metre radio telescope between 13 and 25 January 2015, published in 2015 in Science Advances by Nicolas Biver and colleagues, detected 21 different organic molecules in C/2014 Q2. Among them:

• Ethanol (C2H5OH): abundance ~5% relative to methanol (0.12% relative to water)
• Glycolaldehyde (HOCH2CHO): simple sugar, ~0.8% relative to methanol
• Methanol, acetaldehyde, ethylene glycol, formamide and other organic molecules

The ethanol evaporation rate was equivalent to roughly 500 to 2,000 litres of wine per second, a figurative comparison that circulated widely in the science press. The simultaneous detection of alcohols, aldehydes and simple sugars sparked intense debate about the role of comets as carriers of prebiotic molecules to young planets.

The bluish ion tail developed distinctly from the green coma, creating a striking visual contrast in long-exposure images. The more discreet dust tail pointed in a slightly different direction from the ion tail, as it is dominated by radiation pressure rather than the solar wind.

The spectacle in the sky

In late December 2014 and January 2015, C/2014 Q2 moved through the sky near the Pleiades (M45) and Perseus, providing exceptional photographic fields with the green coma contrasting against the stellar background. Wide-field photographs with 50-to-135 mm lenses captured the comet alongside the Pleiades on 11 January 2015, producing some of the most widely shared comet images of the decade.

At peak brightness around 20 January 2015, the comet reached magnitude 4.0 and was easily identifiable as a greenish fuzzy object from any sky away from light pollution sources. Through 7x50 or 10x50 binoculars, the coma showed internal structure with a brightness gradient and jets of material visible in long-exposure photographs.

The geometry favoured the northern hemisphere: the comet was at high northern declination between December and February, moving through Columba, Puppis, Monoceros and then Cancer before fading. Southern-hemisphere observers had a narrower window of good conditions, in contrast to Lovejoy's C/2011 W3.

Science and observations

The detection of 21 organic molecules in C/2014 Q2, published in Science Advances in 2015, was one of the most significant cometary chemistry results of the decade. The simultaneous presence of ethanol, glycolaldehyde and formamide in the same comet strengthened the hypothesis that comets carry molecules that may have been delivered to young planets during the Late Heavy Bombardment, about 4.1 to 3.8 billion years ago.

Complementary observations with the Nancay radio telescope (France) and APEX in the Atacama Desert (Chile) mapped HCN, HNC and CH3OH emissions as a function of distance from the nucleus, revealing photodissociation gradients that allowed coma chemistry models to be calibrated.

Precision astrometry of the comet, published in 2016, helped refine models of gravitational perturbations from Jupiter and Saturn on long-period comets crossing the planetary region, data useful for predicting trajectories of similar outer Solar System objects.

Key facts

• The 21 organic molecules detected in the comet include ethanol and glycolaldehyde, making C/2014 Q2 the comet with the greatest diversity of complex organic molecules detected at the time of the 2015 observations.
• The ethanol evaporation rate was estimated at 500 to 2,000 litres per second, a comparison the science press popularised as "the comet that produces wine."
• The comet moved from southern to high northern declination between December and February, reversing the situation of Lovejoy's C/2011 W3, which had been more favourable for the southern hemisphere.
• Terry Lovejoy discovered all five of his comets using exclusively amateur equipment: 8-inch reflector telescopes with moderately priced CCD cameras, without access to professional facilities.
• The nucleus rotation period of 17.89 hours was determined from periodic brightness variations in the coma caused by gas jets emitted from the active regions of the nucleus as it spins.
• The detection of glycolaldehyde, a simple 2-carbon sugar that can participate in the synthesis of ribose (an RNA component), reinforced discussion about chemical panspermia and the role of comets in delivering organic precursors to young rocky planets.

Other comets

See the full comet catalogue.