Fireworks, Planets, Comets, a Nova — July’s Got it All!

July's a busy month for skywatching. Not only are five bright planets in view, but three comets and a newly-discovered nova are also observable. And it all starts with a bang on Independence Day.

One explosion begets another

Fireworks light up the sky over Duluth, Minnesota, on Independence Day, July 4th.
Bob King

Many of us will be watching the fireworks on July 4th. The fact that most of the elements in the materials used to make these colorful explosions originated in the violent and explosive deaths of massive stars proves the universe has a wicked sense of humor.

Think about it. The sulfur, oxygen, and carbon in the fuel, and the iron, strontium, barium, and copper that gives the sparks their gold, red, green, and blue colors, were created and set free when massive stars self-annihilated. What goes around comes around!

I have fond memories of fireworks as a kid and still enjoy the shows. On a clear 4th-of-July night with so many people out, it's a great time to introduce friends and family to the sky. There's often time before the big blast to look about during twilight and again later at night after arriving home. Everyone's awake and wired.

Planets, quiet fireworks

Each panel shows the bright planets and stars visible at dusk on July 4th. Look low in the northwest to see Venus and Mercury and to the south for bright Jupiter and Saturn.
Stellarium

This season, there's much to see at dusk, including Venus and Mercury in the western sky and Jupiter and Saturn in the south. The Summer Triangle shines in the east with campfire-colored Arcturus twinkling high in the southwestern sky. Show the kids how to connect Jupiter, Arcturus, and Spica into the giant "Jupiter Triangle."

Don't forget Antares! Located not quite midway between Saturn and Jupiter, this red supergiant star is the summer version of winter's famous giant, Betelgeuse. Both are likely to explode as supernovae in the not-too-distant future, returning freshly forged elements to the interstellar medium that might be come in handy for another special occasion in a far off time.

Disappearance by dust

Astrophotographer Damian Peach created this animation using a Mars Global Surveyor reference image and his own photo of Mars taken on June 28th to highlight how dust has transformed the planet's appearance.
NASA / Damian Peach

Once the kids are in bed, point a scope at the next planet in the parade, Mars. The recent planet-swallowing dust storm continues to transform the appearance of surface features on the Red Planet. The club of Sinus Meridiani, the Solis Lacus "eye", and even mighty Syrtis Major have been so altered they're nearly impossible to recognize. Only parts and pieces remain in view under expansive clouds of obscuring dust. Debris even covers much of the south polar cap, which otherwise would gleam snowy white.

Comet closing in

Comet 21P/Giacobini-Zinner is getting closer and brighter! This photo, taken July 1st, shows a compact coma and short tail pointing southwest. North is up. Comet 21P is a small comet with a 2-km-wide nucleus.
Alfons Diepvens

Turning from planets to deep-sky objects, amateurs can also get their first look at returning comet 21P/Giacobini-Zinner as it tracks north across Cygnus into Cepheus this month. Though still only magnitude 11-11.5, it's brightening rapidly and expected to reach magnitude 7 by late August. Am I wrong or does it feel like forever since we had a binocular comet? I found the little fuzzy on July 2.16 UT in my 15-inch reflector. With a magnification of 64× I saw a 1′-diameter, moderately condensed coma with a faint, star-like false nucleus and a 2′-long tail pointing southwest.

Returning comet

Comet 21P/Giacobini-Zinner travels from Cygnus to Cassiopeia this month, brightening the whole time. Stars in this and the chart below are shown to magnitude 9.5 with positions marked at 0h UT every three days starting July 4th. Click to enlarge and print.
Chris Marriott's SkyMap with additions by the author

Discovered in 1900, 21P/G-Z became the first comet to be visited by a spacecraft. On September 11, 1985, NASA's International Sun-Earth Explorer 3 — renamed and repurposed as the International Cometary Explorer (ICE) — passed directly through its tail and gathered data on the comet's interaction with the solar wind. Perihelion occurs on September 10th, within a day of its closest approach to Earth (0.39 a.u. / 58.4 million km).

Hurrying sunward

Comet PanSTARRS (C/2017 S3) quickly picks up speed this month, moving from Cassiopeia to Auriga. It's best visible just before the start of dawn.
Chris Marriott with additions by the author

That's not all the comet news this month. Comet PanSTARRS (C/2017 S3), which had been chillin' at magnitude 12.5, experienced an outburst some time on June 30th, rocketing to magnitude ~9.5 overnight. Located in Camelopardalis northeast of the Double Cluster, it was super obvious in the 15-inch at low power on July 2.18 UT, appearing as a dense, tailless cotton ball about 3′ across. It looked suspiciously "gassy," so I applied the Swan Band filter and both the brightness and size of the coma increased, a sure sign of a gas blast from the outburst.

Ka-boom!

Comet PanSTARRS (C/2017 S3) on July 2nd showed a bright, greenish coma. Two nights earlier it was three magnitudes fainter.
Michael Mattiazzo

Comet C/2017 S3 may reach magnitude 3 or 4 as it speeds sun-ward in the morning sky en route to an August 16th perihelion. Keep an eye on it with the included chart and expect the unexpected. The outburst could continue or even trigger the comet's disintegration. For more information and an additional map through August 11th, click here.

A comet for southern eyes

Southern observers can look for Comet PanSTARRS (C/2016 M1) in 4.5-inch and larger telescopes as it plunges south. Stars are shown to magnitude 8.
Chris Marriott's SkyMap with additions by the author

While observers in the southern U.S. and points south won't get a good look at that particular Comet PanSTARRS because of its northerly declination, they'll have their own PanSTARRS comet, C/2016 M1. It's currently at its brightest, a small, condensed ball glowing at magnitude 9 in the constellation Ara below the tail of Scorpius.

We end where we began — with an explosion. On June 29th, Yukio Sakurai of Japan discovered a new nova, shining in Scutum at magnitude 10.3. Although it's since faded a touch to ~11.0, this "guest star" is easy to find just a few arc minutes northeast of the 4.6-magnitude star Gamma (γ) Scuti. You can star-hop there from Saturn and then use this AAVSO chart to suss out the nova and estimate its brightness. A 6-inch telescope should suffice.

Warmly welcomed guest

Use this map to help you find Gamma (γ) Scuti then click and download the AAVSO chart at the link above (or just click the map).
Stellarium

Novae occur in close binary stars where one of the members is a white dwarf. The dwarf siphons gas from the companion into a whirling accretion disk and ultimately down to its surface. There it's heated and compressed until burns in a runaway thermonuclear blast. Novae explosions can shine with a luminosity up to 100,000 times that of the Sun. Enough fireworks for anyone!

8 thoughts on “Fireworks, Planets, Comets, a Nova — July’s Got it All!

  1. Tom-Reiland

    Bob, I was able to observe Nova Scuti on Saturday and Sunday nights at Wagman Observatory. I made a rough estimate of 11 mag on both nights. Being that close to Gamma Scuti makes it very easy to spot. The AAVSO chart is a very good aid for locating it. It was nice to find so soon after it was discovered. Too bad it was not on the rise to a much brighter magnitude.

    1. Bob KingBob King Post author

      Hi Tom,
      Glad you grabbed early views. I caught it between clouds last night at 11.3. It’s about as easy as anything to find. A pity it’s not on the rise as many more people would find and see it with ease.

  2. Anthony BarreiroAnthony Barreiro

    Hi Bob. I don’t even try to see small faint comets from the city. But last week we had a couple of very clear (although windy) nights here in San Francisco. And no planets are currently hidden behind the Sun. So I scored a solar system bingo two nights in a row! Between sunset and dawn I observed Mercury, Venus, Jupiter and the Galilean moons, Vesta, Saturn and Titan, Earth’s Moon, Mars, Neptune, and Uranus, with naked eye, binoculars, and a small refractor. This was the first time I’ve seen Neptune and Uranus during their current apparitions, and it took a bit of work to find them the first morning, but the second time was easier.

  3. SNH

    First of all, I’m at 36.1 degrees North, and I last looked at comet M1 as it was on the border of Sagittarius and Corona Australis. I picked it up in my 8×56 binoculars and placed it at +9.5. Too bad its now heading deep south because it was a bright little dude!
    Didn’t know about the outburst of PanSTARRS (C/2017 S3), so will take a look in my binoculars! Nor did I know about the nova, so thanks for that. Looked at Mars last night (08UTC) and was sadly only able to see its North Polar Hood and South Pole Ice Cap in my 10-inch SCT since the rest is covered in dust! Darn!! It’s so large and yet has so little detail visible!!!!

    Great article, and nice fireworks image, Bob!
    Scott

  4. Tom-Reiland

    Bob, thanks to your charts I was able to locate Comet G-Z and PanSTARRS C/2017 S3. This was at least the 4th apparition that I’ve observed G-Z. It was fan-shaped and I estimated it at 9.5 mag. Comet PanSTARRS was round with a gradually brighter center. I put it at about 10 Mag. Nova Scuti has brightened to 11mag. Vesta is still easy to find and I observed all of the planets starting with Venus, Mercury, Jupiter and Saturn in the evening and finishing with Mars, Neptune (with Triton) and Uranus in the morning. I should be able to get a few more nights in a row with this fair weather disaster moving into Western Pa. It was a great way to celebrate 72 years on this planet as the clock reached Midnight.

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