Astronomy

Check Out This Great View of Comet 96P Machholz, Courtesy of SOHO

Now’s the time to catch periodic Comet 96P Machholz on its encore dawn performance, before it slides out of view.

So, have you been following the touted ‘green comet,’ E3 ZTF? To be sure, it’s nothing more than a fuzzy patch, a binocular comet sliding through the constellation Auriga looking like a globular cluster that refuses to resolve into focus. Though E3 ZTF may not live up to the hype, it does have one thing going for it: it is currently well-placed for northern hemisphere viewers. It also put on a great show for astrophotographers as it recently completed an orbital plane-crossing, as seen from our Earthly vantage point.

Meanwhile, another comet has also put on a show, mostly hidden from view: Comet 96P Machholz.

The comet reached perihelion on January 31st at 0.124 Astronomical Units (AU)/18.5 million kilometers from the Sun (three times closer to the Sun than Mercury at its closest). The comet put on a fine performance, sliding through the field of view of the joint NASA/ESA SOHO (the Solar and Heliospheric Observatory) LASCO C3 imager view. Though SOHO’s primary mission is to monitor solar activity, it does pick up sungrazing and even doomed comets from time to time, mainly using its LASCO C2 and C3 imagers, which are equipped with occulting disks to block out the Sun. Since arriving at the sunward Lagrange 1 point in late 1995, SOHO has detected an amazing 4,551 sungrazing comets and counting, most of which were found thanks to the efforts of dedicated online volunteers. And to think, only less than a dozen sungrazing comets were known of, prior to the launch of SOHO. It’ll be sad to see this amazing resource coming to a scheduled end in 2025.

An animation of 96P’s recent passage through SOHO’s LASCO C2 field of view. Credit: NASA/ESA.

Comet 96P displayed a fine fantail as it swept through the view. But what’s truly amazing is that the comet seems to have retained some of that brightness as it emerges into the dawn sky in early February. astrophotographer Michael Jaeger managed to nab the comet on the morning of February 5th from Martinsberg, Austria. The comet was just 15 degrees west of the Sun at the time, sporting a one degree long tail, about twice the diameter of the Full Moon.

Comet 96P at dawn from February 5th. Credit: Michael Jaeger.

Though low to the horizon targets are always difficult, the comet seems to be holding steady at magnitude 0, about as bright as the star Vega. Keep in mind, however, that—like extended deep sky objects—all of that precious magnitude gets ‘smeared out’ over an apparent surface area, making the comet look visually fainter than a star of equal magnitude.

Comet 96P as seen from the view of NASA’s STEREO-A spacecraft in 2007. Credit: NASA

The Comet in February

This week, the comet is hanging low to the east, higher than Mercury but lower than the bright star Altair, which both serve as good markers to find the comet. The comet is moving roughly away from us from our Earthly perspective, which means it will stay about 10 to 15 degrees above the eastern horizon for most of February 2023.

The position of the comet low in the dawn sky on the morning of February 9th. Credit: Starry Night.

On a 5.29 year orbit, Comet 96P Machholz has the shortest perihelion distance of any known short period comet. The comet also exhibits a strange carbon- and cyanogen- depletion that suggests that it may actually be a captured extra-solar comet.

The orbital path of Comet 96P. Credit: NASA/JPL Horizons.

Comet 96P was discovered by prolific comet hunter Don Machholz on the night of May 12, 1986. Don discovered 12 comets during his sky-watching career. Sadly, we lost Don last year to COVID-19. He was 69, and one of the last of an era of visual comet-hunters.

Don Machholz. Credit: Michelle Machholz/Wikimedia Commons.

If skies are clear, be sure to brave the early February morning, for a chance to spy Comet 96P Machholz.

David Dickinson

David Dickinson is an Earth science teacher, freelance science writer, retired USAF veteran & backyard astronomer. He currently writes and ponders the universe as he travels the world with his wife.

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