Comet NEOWISE Grows Another Tail

While the dust tail is bright and obvious with the naked eye, the comet’s blue ion tail is more subtle. You can see it here to the left of the dust tail pointing almost straight up. Dust tails like their names implies are made of dust while ion or “gas” tails are composed of carbon monoxide that fluoresces in the sun’s ultraviolet (UV) light. Ion tails always point directly away from the sun; dust tails curve. Bob King

This comet just keeps on getting better. I was out again at 3:30 this morning and found Comet NEOWISE without even trying. Early on its head appears faint because of low altitude, but the tail is growing. I could easily see 3°-4°of it with the naked eye. Binoculars and photos doubled that. By 4 a.m., when the comet’s head was high enough to see clearly, it looked exactly like a star. I was also able to photograph the comet’s ion tail for the first time. Although I don’t know the length of this delicate appendage, the dust tail is at least 10 million miles (16 million km) long. Dust deposited in the orbit of the comet gives the tail a curved shape.

Dust-laden ice boiled from the comet’s nucleus by the sun forms a head or coma and typically two tails, one of dust, which lags somewhat behind the comet, and one of fluorescing gases called the gas or ion tail, shaped by the solar wind. ESO / E. Slawik

Ultraviolet light from the sun strips electrons from the gases released from vaporizing comet ice turning them into ions. If an atom or molecule gains or loses electrons it’s no longer “neutral” but said to be ionized. Ionized gases are strongly affected by magnetic fields bundled in the solar wind, the steady “breeze” of minute, subatomic particles blowing from the sun. By the way, these are the same specks that spark auroras. Comet ions are directed by the solar wind into a tail directly behind the comet.

The comet’s nucleus — hidden by dust — is located within the bright head. Recent infrared observations by the NASA’s NEOWISE spacecraft indicate that the nucleus is on the large side at 3.1 miles (5 km) across. Its size helped it survive a fairly close passage of the sun back on July 3. Sometimes bigger really is better! Details: 600mm telephoto at f/6.3, 15-seconds at ISO 800 on a tracking mount. Bob King

As of July 10 NEOWISE is now magnitude 2, so it’s faded a little, but that’s been more than offset by the comet’s increasing altitude and the waning of the moon. If you have a telescope be sure to look at the comet for a powerful eyeful. Then, as dawn gets too bright to see NEOWISE well, swing your scope over to the waning moon for a look at some of the most incredible crater fields you’d ever want to see. After the moon, visit Mars. The moon passes to the lower right of the planet on July 11 and to the lower left on the 12th. Use high magnification and you’ll see the coolest feature Mars has to offer — its stunning south polar cap.

Venus in the V-shaped Hyades star cluster on July 10 at dawn. The “V” is tipped on its side with the bright star Aldebaran shining below below the planet. Bob King

Richard Mitchell, one of our readers, reminds us that Venus is also at maximum brilliancy, another reason to get out at dawn. Coincidentally, it’s crossing the Hyades star cluster in Taurus, making for a pretty binocular sight.

Comet NEOWISE joins Venus (right) and the bright star Capella (top) around 4:15 a.m. this morning, July 10. Bob King

I normally wake up around 8 in the morning but thanks to NEOWISE I’ve been rising around around 10 … with a ferocious appetite after being out all morning! Let the comet change your life a little. If nothing else it’ll take your mind off COVID-19 for a little while. Clear skies!

If you have a telescope and a cell phone try taking a picture of the comet in the brightening dawn sky. I took this photo through my 10-inch scope with a basic cellphone this morning (July 10). Bob King




5 Responses

  1. Edward M Boll

    The morning sky the clouds finally cleared enough for me to see the comet. And what a comet! I think that this may perhaps be the best one I have ever seen next to 2007 McNaught. For instance take the so called super comet Hyaktake. I could never see it’s tail without binoculars. But Neowise. I packed it up 70 minutes before sunrise and headed home. A comet only 20 degrees from the Sun, this had to be about it. But surprise back to my small town just an hour before sunrise there was Neowise just as plain as could be. And even in twilight I could see with my own eyes a hint of a tail. Rain tonight. I am satisfied now for now. But I will be out again Sunday morning
    If the forecast is right we will see it again, still holding onto magnitude 2 we hope. I did see Venus and Aldebaran. The comet nearly rivaled in brightness the star this morning, mag 1.5.

  2. Edward M Boll

    Morn couldn’t be greater. Jupiter near Saturn. The Moon near Mars, Venus near Aldebaran. A 1.3 magnitude comet, nice broad tail in binoculars and below the comet clouds and lightning. What a morn, 2 in a row now. Tomorrow third base, a home run if Monday is clear!

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