Tag Archives: 96P/Machholz

Lightning under the stars, a moon show and Comet Machholz at dusk

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Lightning illuminates a thundercloud in northern Minnesota last night. The stars near the storm belong to the constellation Perseus the Hero. Photo: Bob King

Came back from Colorado last night to a line of thunderheads along the northern horizon. I would have gone out earlier to shoot more lightning photos, but my dog Sammy decided to punish me for my weekend absence by running away during her walk. After a fruitless search and knowing she’d find her way back home, I sped off to a wide open horizon to watch the distant storm.

The sky facing southwest ah hour or so after sunset tonight July 23. The moon will be near Mars tomorrow night and Saturn and Spica the next. Created with Stellarium

I’d hoped to see some sprites, those energetic bursts of pink light that shoot upward from thunderstorm cloud tops into the ionosphere. No luck on that, but the jagged strokes against starlight were pleasure enough.

Tonight the crescent moon returns for easy viewing in the southwestern sky during twilight. If you wait at least an hour after sunset, you can see a nice lineup of moon, planets and Spica in a darker sky.

Comet 96P/Machholz zips through Leo and Leo Minor in the coming days. The map depicts the sky facing west about 90 minutes after sunset or around 10:15 p.m. (CDT). Tick marks show where the comet is each evening now through August 1. Stars are plotted to 8th magnitude. Created with Chris Marriott’s SkyMap software

For amateur astronomers with 6-inch scopes and larger who like a challenge, returning comet 96P/Machholz is now making an appearance in evening twilight in the western sky. It’s currently a small, condensed blob of light shining at 7.8 magnitude.

If it were in a dark sky well above the horizon, you’d see the fuzzy fellow with ease even in a 3-inch telescope. Instead, Machholz is only about 5 – 10 degrees high (one fist held at arm’s length equals about 10 degrees) during mid to late twilight. A sky with little haze and a wide open view to the west is essential if you want to grab a view.

And yes, Sammy came back. She was waiting for me at the front door.

Comet Machholz sizzles as we await the aurora

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A quiet, petite auroral oval from this earlier this morning. Credit: NOAA

No impact yet from the hoped-for cloud of solar plasma after Thursday’s big solar flare. All’s quiet on the magnetospheric front, but that could change at any moment. For now the Kp index, a measure of potential auroras, sits at “1″, its lowest level, and the auroral oval has shrunk to a mini-donut. During auroral storms, the oval expands southward over northern Europe, Canada and the U.S.

Don’t be lulled by this inactivity – my gut tells me it’s only the calm before the storm.

96P/Comet Machholz showed up this morning around 8 a.m. (CDT) in the narrower field of view of SOHO’s C2 coronagraph. Machholz reaches perihelion today (closest to the sun). In about a week, we’ll see it in the evening sky. Credit: NASA/ESA

Utterly invisible to telescopes on Earth, 96P/Comet Machholz passes only 11.2 million miles from the sun today, well within the orbit of Mercury. The space-based Solar and Heliospheric Observatory (SOHO) sees the small comet clearly using a specialized coronagraph to block the sun’s brilliant disk. The comet shines brightest now at 2nd magnitude and will fade as it speeds away from both the sun and Earth.

96P/Machholz photographed by STEREO-A during its last go-around in 2007. Credit: NASA

Comet Machholz was discovered by American amateur astronomer Don Machholz in 1986 and returns to Earth’s vicinity every 5.2 years. Since it has an orbital period of less than 200 years, astronomers classify it as a short-period comet.

There are about 265 numbered, short-period comets and nearly as many unnumbered ones. Periodic comets get an official number after they’ve been observed through two perihelion passages.

Machholz stands out from many of its brethren in two ways: it has the closest perihelion distance of known, regularly-returning comets and it’s depleted in carbon.

Comets glow green from fluorescing carbon molecules when near the sun. Astronomers suspect Machholz’s lack of this otherwise common element could mean it got baked out during repeated close swings by the sun. Another hypothesis posits an interstellar origin for the comet to explain its singularity.

Comet Machholz will rapidly fade from 7.5 magnitude on July 22 to 10th magnitude on August 1. Time Created with Chris Marriott’s SkyMap software

Machholz’s orbit is related to the Arietid, Southern Delta Aquarid , Quadrantid meteor showers and that of asteroid 2003 EH1, so it’s possible all of them trace their origin to a larger body that was disrupted long ago. You can read more about this comet’s curious connections on Karl Battam’s Sungrazing Comets page.

In about a week, 96P will grace evening twilight in the western sky. You’ll need at least a small telescope to see it. The map above shows its path through Leo Minor, Leo and Coma Berenices as you face west around 10:15 p.m. local time.

UPDATE 10:35 p.m. (CDT): The blast arrived this afternoon when the Kp index hit “5″ and remained through the early evening. At 10 p.m. the index slipped downward to “4″. The present extent of the auroral oval indicates minor aurora for the northern U.S. and southern Canada. This can change at any time overnight. Don’t forget tomorrow morning’s lovely conjunction of the thin crescent moon with Venus and Jupiter. Face east at dawn to see it!