Two views of a sunlit comet: A small, bright surprise:


A bright little surprise was awaiting them as scientists downloaded data from the sixth orbit of the Parker Solar Probe: the spacecraft’s first observation of a comet orbiting the Sun.

Just a few weeks ago, this particular comet was discovered using data from the ESA (European Space Agency) and the NASA Solar and Heliospheric Observatory (SOHO).

Spectacular images of comet NEOWISE were taken by Parker Solar Probe in July 2020, but this is the first time that the spacecraft has seen a sungrazer, a rare class of comets moving very close to the Sun and usually so small and faint that it is difficult to see them from Earth or from observatories other than SOHO.

This sighting confirms the expectation of the Parker Solar Probe team that the WISPR instrument of the probe, designed to picture the outer atmosphere of the Sun and solar wind, will provide fresh insights into these celestial stellar bodies.

As almost all sungrazers, this comet was killed when it passed through the Sun, called SOHO-4063 after the observatory that first found it, disintegrating as it was heated by intense sunlight.

With future observations of sungracers by the Parker Solar Probe, it is this destruction mechanism that scientists hope to learn more about – a prospect that seems more probable after these first pictures.

In Parker Solar Probe’s data, the comet appeared brighter than in SOHO’s, indicating that Parker Solar Probe’s WISPR instrument is especially sensitive to comets and could provide new information about sungrazers crossing the field of view of the probe. The near solar orbit of the Parker Solar Probe also takes the spacecraft closer than other observatories to these Sungrazer comets – about 40 million miles away, less than half the distance from which SOHO sees Sungrazer.

These pictures from September 13-15, 2020, as seen by the ESA (European Space Agency) and NASA’s Solar and Heliospheric Observatory, show comet SOHO-4063 as it approaches the Earth.

Comet SOHO-4063 was later found in NASA’s Parker Solar Probe data.

Credit: Brendan Gallagher/Naval Science Lab/ESA/NASA/SOHO.
Comet SOHO-4063 was originally discovered by citizen scientist Worachate Boonplod with the Sungrazer project on Sept. 13, 2020, and the comet appeared later in data from Parker Solar Probe. At particular points in its orbit, Parker Solar Probe sends its science data back to Earth in batches, ensuring that scientists do not check for the comet in the data from Parker Solar Probe until weeks after its detection in the SOHO data.

Even with such weeks-or months-long delays, the proximity of the Parker Solar Probe to sungrazers and the high sensitivity of the WISPR instrument to comets means that new sungrazer comets can be discovered by the Parker Solar Probe that avoid even SOHO.


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