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SOHO/LASCO COMET OBSERVATIONS




Composite picture of sungrazer comet approaching the Sun, observed from
the SOHO satellite

For a larger image, click on picture


INTRODUCTION

The composite image above was created using three different instruments on the Solar and Heliospheric Observatory (SOHO). The solar disk image was taken by the Extreme Ultraviolet Imaging Telescope (EIT) in the Fe XV line at 284 Angstroms. This has an approximate temperature of 2-2.5 million Kelvin. The sun's lower corona was imaged in the O VI line by the Ultraviolet Coronagraph Spectrometer (UVCS). The outermost image of the corona, shown in white light, was taken by SOHO's Large Angle Spectrometric Coronagraph (LASCO) on December 23, 1996 with the C3 coronagraph. Visible in the corona are several prominent streamers, one on the left (East) side of the sun and two on the right (West). The image shows comet SOHO-6 (C/1996 Y1) located at the bottom left of the sun. Also visible is the Milky Way, which stretches from the top to the bottom in the image.

SOHO is a cooperative mission between the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA). SOHO studies the sun from deep down in its core out to 32 solar radii. The spacecraft orbits the L1 Lagrangian point. From this orbit, SOHO is able to observe the sun 24 hours a day. It carries twelve state-of-the-art instruments expected to meet the mission's three principal scientific objectives. These objectives are: to study the solar interior, to study the heating mechanisms of the solar corona, and to investigate the solar wind and its acceleration processes.

Even though SOHO's primary objectives relate to solar and heliospheric physics, the onboard LASCO instrument has become the most prolific comet discoverer in history! LASCO is a three-coronagraph package (C1, C2, & C3) with nested field of views of 1.1-3, 2.5-6, and 4-32 solar radii, respectively. The C1 instrument was designed to observe hot coronal emission and, therefore, has not observed any comets. However, since LASCO began taking observations in January of 1996, the C2 and C3 coronagraphs have observed over 1100 new comets and several known comets. In addition, the SWAN instrument onboard SOHO has discovered 4 new comets and observed many known objects. The UVCS instrument has also observed a handful of known comets.

Image from SWAN instrument LASCO C3 images of comet NEAT UVCS images of comet
Soho6
SWAN image of comets Kudo-Fujikawa, NEAT, & Juels-Holvorcem (path not shown). LASCO C3 image of comet NEAT (C/2002 V1). UVCS image of SOHO6 (C/1996 Y1).
Mpeg (2.2 MB) Mpeg (1.9 MB)


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