☄ Lovejoy (sungrazer) C/2011 W3

How to follow comet Lovejoy (sungrazer) live

The panel above recomputes the position of Lovejoy (sungrazer) 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 (sungrazer) 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 (sungrazer) with no math at all.

Comet fact sheet

About Lovejoy (sungrazer)

C/2011 W3 is the comet that was not supposed to survive. On the night of 15-16 December 2011, it passed perihelion at 0.0055 astronomical units from the centre of the Sun, equivalent to about 1.2 solar radii, immersed in the corona at temperatures exceeding one million degrees Celsius. Theoretical models predicted near-certain disintegration. Instead, the nucleus survived and emerged on the far side, captured in high-definition by NASA's Solar Dynamics Observatory (SDO), producing one of the most dramatic astronomical sequences of the 2010s.

Beyond the spectacular survival, C/2011 W3 was the first comet detected by the X-ray camera aboard the Hinode satellite and the brightest sungrazing comet ever observed by SOHO, reaching magnitude -3 to -4 after perihelion. In the southern terrestrial hemisphere it was naked-eye visible before dawn for several days, with a tail spanning dozens of degrees.

History and discovery

Terry Lovejoy, the same Australian amateur astrophotographer from Queensland who discovered four other comets bearing his name, found C/2011 W3 on 27 November 2011, just eighteen days before perihelion, using an 8-inch reflector with a CCD camera. The very short gap between discovery and perihelion left little time for detailed pre-perihelion analysis.

The orbit immediately revealed it as a member of the Kreutz family, a set of comets with extremely close solar perihelia that share a common ancestral orbit. All Kreutz comets are believed to be fragments of a giant comet that split apart at least two millennia ago. The most cited candidate for the original comet is the Great Comet of 371 BC, mentioned by Aristotle in his writings and by Timaeus of Tauromenium.

The Kreutz family is named for German astronomer Heinrich Kreutz (1854-1907), who mathematically demonstrated in the nineteenth century that several major historical comets (the Great Comets of 1843, 1880, 1882 and others) shared the same ancestral orbit, concluding they were fragments of a single original object.

Orbit and the Kreutz family

Kreutz comets typically have perihelia between 0.004 and 0.009 AU from the Sun, placing them inside the solar corona at closest approach. Their orbital inclination is high and most have retrograde orbits, moving in the opposite direction to most of the planets.

Most of the thousands of Kreutz objects catalogued by SOHO's LASCO instrument are small fragments just a few to a few hundred metres across, which evaporate completely before leaving the corona. C/2011 W3 was unusual in having a nucleus estimated at about 600 metres in diameter before perihelion, which may partly explain the temporary survival. Even so, the comet survived for only about 1.6 days after perihelion before the nucleus disintegrated definitively.

Nucleus, coma and tail

Inside the solar corona, C/2011 W3's nucleus was subjected to an extreme environment: temperatures exceeding one million degrees Celsius, but corona density extremely low, meaning heat transfer to the nucleus occurs mainly by radiation rather than conduction. The nucleus, composed of ice and dust, evaporated material at a very high rate, generating a gas-and-dust envelope that in turn interacted with the corona.

NASA's SDO, operating in extreme ultraviolet (EUV) and X-rays, recorded the entry into and exit from the corona in high-resolution imagery, creating a dramatic sequence widely shared around the world. SDO data allowed study of how cometary plasma interacts with coronal magnetic structures, disturbing coronal loops and possibly locally altering the solar magnetic field structure.

After perihelion, the comet's tail became naked-eye visible in the southern hemisphere spanning dozens of degrees. The plasma tail showed dynamic structure with disconnection events caused by interaction with the variable solar magnetic field, a scientifically rich phenomenon documented by the STEREO-A and STEREO-B satellites.

The spectacle in the sky

Because it was so close to the Sun, C/2011 W3 was observed mainly by solar satellites during perihelion. SDO recorded the corona entry and exit in high spatial and temporal resolution ultraviolet imagery, and the video compiled from those images was among the most viral in solar astronomy at the time.

From Earth, the comet became naked-eye visible in the southern hemisphere after perihelion, emerging from solar glare in the pre-dawn sky of December 2011. Observers in Australia, New Zealand, South Africa and South America reported a long, bright tail sweeping an arc of 30 degrees or more across the dark sky before dawn.

Between 17 and 25 December 2011, images of the comet's tail in the southern sky went viral on astronomy social networks and science portals. The tail was narrow and well-defined, unlike the broad fan-shaped tail typical of great comets like McNaught. The magnitude of -3 to -4 at peak was comparable to planet Venus, making C/2011 W3 the brightest sungrazer ever observed by SOHO in more than a decade of operation.

Science and observations

C/2011 W3 was the most significant comet for solar physics since the launch of SDO and the first detected by the X-ray Telescope (XRT) aboard the Hinode satellite. The X-ray observations showed high-energy emission produced by the interaction between cometary plasma and coronal electrons, a physical regime never before documented so clearly.

A paper published in Science in 2013 (Downs et al.) modelled the interaction between the comet and the corona using magnetohydrodynamic simulations and demonstrated that the disturbances in coronal structures observed by SDO were directly caused by the nucleus passage, not by coincident solar activity. It was the first direct demonstration that a comet can perturb the magnetic structure of the solar corona.

Analysis of the post-perihelion tail by the STEREO satellites revealed multiple plasma disconnection events, in which segments of the ion tail separate from the main body and are carried away by the solar wind. Each event coincided with a change in the interplanetary magnetic field, confirming that cometary tail disconnections are caused by reversals in the solar wind magnetic field polarity.

Key facts

• While the comet was inside the solar corona, SDO detected visible disturbances in coronal magnetic structures caused by the nucleus passage, the first direct physical interaction between a comet and the solar atmosphere documented at that level of detail.
• The Kreutz family likely originated from a single giant comet that fragmented about 2,000 years ago. SOHO has detected more than 4,000 Kreutz fragments since 1996, most of them just metres to tens of metres across, evaporating in the corona without leaving a trace visible from Earth.
• After perihelion, the comet's tail briefly pointed back toward the Sun for a few hours, a phenomenon called an antitail, caused by the viewing angle when the observer is in the comet's orbital plane.
• C/2011 W3 is the largest confirmed Kreutz comet to temporarily survive perihelion in decades, comparable only to the Great Comet of 1882, another Kreutz member that also survived and was visible in daylight at an estimated magnitude between -10 and -17.
• C/2011 W3's nucleus survived for only about 1.6 days after perihelion before finally disintegrating, based on analysis of SOHO and STEREO images from December 2011.
• Terry Lovejoy, its discoverer, learned that his comet had survived perihelion via social media notifications while he slept, since the passage occurred during the Australian middle of the night.

Other comets

See the full comet catalogue.