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Comet Comments — The Return of Machholz 1

Jane Houston Jones


Don Machholz discovered 96P/Machholz 1, a magnitude 11.0 comet, on May 12, 1986 from the Santa Cruz Mountains, RA 0h 40.8, Dec +38 36m (1950.0) through 29x130 binoculars. Don's Comet Comments column appeared on this page of the Ephemeris for many years.

This unusual comet, reputed to flare up a lot, was only 22 million kilometers from the Sun in January 2002. This is its closest approach on an orbit that brings it back to the solar vicinity every 63 months. The best and perhaps the only view of it at this time comes from the ESA-NASA sunwatching spacecraft SOHO. As an added bonus, Venus appears in the lower right part of the images.

The LASCO image was obtained by the LASCO instrument, on the SOHO satellite. The LASCO instrument was built and is operated by the LASCO consortium of the Naval Research Laboratory (Washington D.C.), The Laboratory for Space Astronomy, Marseilles (France), The Max Plank Institute for Aeronomy, Lindau (Germany) and the Department of Space Research, Birmingham (UK). The UVCS images are courtesy of SOHO/UVCS (ESA&NASA)

For more information, check out the SOHO website:

Comet Machholz 1 sighted by the SOHO (Solar Heliospheric Observatory) Ultraviolet Coronagraph Spectrometer (UVCS). UVCS is composed of three reflecting telescopes, two spectrometers and a polarimeter. Observing through a narrow slit, the comet drifted by the field of view, enabling the reconstruction of an image, shown superimposed on a LASCO C3 (Large Angle Spectrometric Coronograph C3) image.

This image was obtained by the LASCO instrument on the SOHO satellite. The instrument is a set of three coronagraphs that image the solar corona from 1.1 to 32 solar radii. One solar radius is 700,000 km, 435,000 miles, or 16 arcminutes. A coronagraph is a telesocpe that is designed to block light coming from the solar disk, in order to see the extremely faint emission from around the sun, called the corona.

Note the striking difference between the previous image which shows the visible light of the sun from the LASCO instrument and this UV light of Lyman alpha from the UVCS (Ultraviolet Coronagraph Spectrometer). These observations can be analyzed to give an estimate of the density of the impinging solar wind at the position of the comet.


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