16 April 2014 - Mission Day: 6711 - DOY: 106

SOHO Comet 100

Explanatory note: In this and all subsequent coronagraph images, the shaded disk is a mask in the instrument that blots out direct sunlight. The white circle added within the disk shows the size and position of the visible Sun.

Caption: Calculations confirm that a comet spotted by Kazimieris Cernis of Vilnius, Lithuania, on 4 February is a previously unknown object, making it the 100th comet discovered with the SOHO spacecraft. Launched four years ago as a project of international cooperation between the European Space Agency and NASA, the Solar and Heliospheric Observatory has revolutionized the science of the Sun. It has also revealed an amazing number of kamikaze comets plunging into the solar atmosphere, which help to make SOHO the most prolific comet finder in the history of astronomy. But SOHO-100 is an ordinary comet, and so are two others that have appeared in the past few days.

More information available in the ESA Press Release

Instrument: LASCO (Large Angle and Spectrometric Coronagraph) Taken: 4 February 2000

Sungrazing Comets Discovered by SOHO

The 1996 Christmas Comet (SOHO-6)

SOHO Christmas Comet Caption:LASCO C2 image of the solar corona on 23 December 1996 at 04:44 UT showing the inner streamer belt along the Sun's equator, where the low latitude solar wind originates and is accelerated. Over the polar regions, one sees the polar plumes all the way out to the edge of the field of view. The field of view of this coronagraph encompasses 8.4 million kilometers (5.25 million miles) of the inner heliosphere. The frame features Comet SOHO-6 with its tail curving towards the lower left side of the image.
Full Resolution image.
Movies:MPEG, QuickTime

Twin Comets (SOHO-54 & 55)

Twin Comets In a rare celestial spectacle, two comets were observed plunging into the Sun's atmosphere in close succession, on June 1 and 2, 1998. This unusual event on Earth's own star was followed on June 2 by a likely unrelated but also dramatic ejection of solar gas and magnetic fields on the southwest (or lower right) limb of the Sun.
Full C2 field of view
Movies: MPEG: C2, C3, QuickTime: C2, C3.

SOHO Comet 48

SOHO Comet 48 This Kreutz sungrazing comet from April 30, 1998 was observed in the LASCO C2 telescope. The comet is seen to fade rapidly as it approaches the Sun over a period of just 5 hours. The comet's nucleus is overexposed in the first few frames, resulting in the visible diffraction spikes.
Movies: MPEG, QuickTime, Animated GIF.

Other Comets Observed* with SOHO

*Not necessarily discovered by SOHO.
For an exhaustive list of all comets discovered by SOHO, go to the Sungrazer site.

Comet Hyakutake

Discovered by Yuji Hyakutake in Japan on 30 January 1996, this conspicuous comet passed grandly through LASCO C3's field of view at the beginning of May 1996. Even bright comets are not normally visible so close to the Sun in the sky, without the benefit of the artificial eclipse in a coronagraph such as LASCO.
Movies: MPEG: small, full size, QuickTime.

SOHO Comet 49

Copyright (c) 1998 Michael Horn
Movies: MPEG, Animated GIF.
This sequence shows C/1998 J1 as it skirts the edge of the LASCO C2 field of view. This comet, the 49th discovered by SOHO, is not a Kreutz sungrazer. Shortly after SOHO-49 was discovered, it was realized that it could eventually be observed from the ground. Also visible are several explosions of material, 'mass ejections' from the solar corona.
A ground-based image of SOHO-49, courtesy of Michael Horn of Brisbane, Australia. He kindly agrees to the use of this image by the media and other third parties in connection with the ESA and NASA news releases about SOHO-100. For any other usage, permission from Michael Horn will be required first. Click on the image for a larger version. For more ground-based images of this comet, go to this site

A Flyby (SOHO-46)

This dramatic movie shows comet C/1998 G3 (SOHO-46). This comet, while not a Kreutz sungrazer, approaches to within 7 solar radii (4.5 million kilometers) of the Sun. The comet is seen to `whip' around the Sun and then fade from view. This comet fades not because it has burned up, but because it is receding from the Sun. Note, at the beginning of the sequence, a faint Kreutz sungrazer (SOHO-47) can be seen, quickly moving towards the Sun from the bottom of the picture. It takes sharp eyes to find the Kreutz comet, as there is no visible tail.
Movie: MPEG, QuickTime.

Comet Hale-Bopp Observed by the SWAN Instrument

A huge cloud of hydrogen surrounded Comet Hale-Bopp when it neared the Sun in the spring of 1997. Ultraviolet light, charted by the SWAN instrument on the SOHO spacecraft, revealed a cloud 100 million kilometres wide and diminishing in intensity outwards (contour lines). It far exceeded the great comet's visible tail (inset photograph). Although generated by a comet nucleus perhaps 40 kilometres in diameter, the hydrogen cloud was 70 times wider than the Sun itself (yellow circle to scale) and ten times wider than the hydrogen cloud of Comet Hyakutake observed by SWAN on SOHO in 1996. Solar rays broke up water vapour released from the comet by the warmth of the Sun. The resulting hydrogen atoms shone by ultraviolet light invisible from the Earth's surface. Even a satellite's view of the Hale- Bopp cloud would be spoiled by hydrogen around the Earth. Stationed 1.5 million kilometres out in space, SOHO had a clear view. SWAN is the brainchild of Jean-Loup Bertaux and colleagues at the Service d'A[e/]ronomie du CNRS (France) and the Finnish Meteorological Institute. Tuned to see hydrogen, SWAN scans the sky and studies the solar wind's effect on hydrogen atoms coming from interstellar space. Comets reveal themselves as local sources of hydrogen. With SWAN's maps, Michael Combi of the University of Michigan studies gas outflow from comets. He also uses the Hubble Space Telescope, but that instrument cannot safely look at comets near the Sun. The unique SWAN observations of Comet Hale-Bopp imply that the outflow of water vapour peaked at almost 50 million tonnes a day. Credits: Main image: SOHO (ESA & NASA) and SWAN Consortium Inset photo of comet: Dennis di Cicco and Sky & Telescope
Movie: MPEG

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