5 Sky Events This Week: Comet Buzzes Mars, False Dawn, Green Giant

While comet ISON will be making a flyby of Mars this week, this may be just a dress rehearsal for a much closer encounter with another comet late next year, as portrayed in this illustration. Credit: Courtesy of NASA

As the calendar turns to a new month, sky-watchers get a chance to see not only a sprinkling of shooting stars and some ghostly glows, but also a distant gas giant in its best appearance of 2013.

Comet buzzes Mars. In the predawn skies on Tuesday, October 1, famed Comet ISON (C/2012 S1) will be barnstorming the red planet, appearing only 2 degrees apart from the planet—just a little more than the width of your thumb at an arm’s length. Their proximity is no illusion, however, as a mere 6.7 million miles (10.8 million kilometers) will separate the comet from the planet during today’s close encounter.

This illustration shows comet ISON making a very close swing by of Mars on October 1, 2013. Credit: NASA
This illustration shows comet ISON closely passing Mars on October 1, 2013. Credit: NASA

With the comet still being about 12th magnitude, you will need at least a 6- to 8-inch mirrored telescope to glimpse it in the eastern sky before dawn. Already backyard astronomers are reporting that the distant, puffy comet has formed a small, greenish-glowing tail. That is a sign that the sun’s heat has begun to have its effects, making the comet active by vaporizing the ice on its surface and forming a hazy cloud around its nucleus. Check out spaceweather.com’s growing ISON photo gallery from contributing backyard sky-hounds.

Here is a wide-angle shot of the eastern sky before dawn Sept.29 showing the placement of ISON in relation to Mars and other familiar celestial landmarks.  Credit: Malcolm Park @ Oak Heights, Ontario
This wide-angle shot of the eastern sky before dawn September 29 shows the placement of comet ISON in relation to Mars and other familiar celestial landmarks. Credit: Malcolm Park @ Oak Heights, Ontario

Along with keen astronomers on the ground,  NASA and the European Space Agency are set to snag some of their own picture postcards of the Mars flyby with spacecrafts such as the Mars Curiosity and Opportunity rovers on the planet’s surface, and the Mars Reconnaissance Orbiter and Mars Express spacecraft circling the planet.

This Mars event, though, as cool as it is, is just a warm-up for another, much closer encounter with comet Siding-Springs slated to occur in late 2014. (See also “Monster Comet May Have Mars in Its Crosshairs.”)

As an added bonus skywatching event easily seen with nothing more than your unaided eyes, watch Mars , Moon and Regulus triangle in the east on Tuesday at least 30 minutes before sunrise.

Orionids kick-off. Starting on the night of Wednesday, October 2, the annual Orionid meteor shower begins, peaking nearly three weeks later on October 21 and ending on November 7. Since the waning gibbous moon will be in the sky at peak time, washing out all but the brightest shooting stars, it’s best to look for the shower before then.

Orionids appear to radiate out from their namesake constellation Orion, which rises in the northeast just before local midnight this time of the year. Orion is one of the easiest star patterns to recognize, thanks to the three bright stars that line up in a perfect row, marking the mythical figure’s belt.

Rates at peak time generally hover around 20 meteors per hour, so expect much more modest rates of no more than 10 per hour over the next couple of weeks. (Related: “New Meteor Shower Discovered; May Uncover New Comet.”)

Uranus opposition. On Thursday, October 3, the seventh planet in the solar system, Uranus, will be at official opposition—meaning that the outer planet will be at its biggest and brightest in the sky for 2013. The green ice giant will appear opposite in the sky from the sun, rising in the east after sunset in the constellation Pisces, to the far lower left of the Circlet asterism.

At magnitude 5.7, Uranus can be spied with the naked eye in the dark countryside, but you may find it easier to pick out its tiny green-blue disk with binoculars or a small telescope.

The Sky and Telescope website offers this handy finder’s starchart to help locate both ice giants, Uranus and Neptune, in the sky.

Zodiacal light. At about an hour before sunrise on Thursday, October 3, and for the next two weeks, keen sky-watchers in the Northern Hemisphere can view one of the most elusive astronomical phenomena visible in the sky—the Zodiacal light.

This pyramid-shaped beam of light is easily mistaken for the lights of a far-off city just over the dark horizon, and has also been called the false dawn. But this light is more ethereal; it is caused by sunlight reflecting off cosmic dust between the planets.

It is amazing to think about the billions of dust-sized particles that were left behind after the planets formed about 5 billion years ago.

Worlds form triangle. After sunset on Sunday, October 6, look toward the very low southwestern horizon for a razor-thin crescent moon sandwiched between Saturn above and Mercury below. To catch the cosmic trio, it is best to find a location with an unobstructed view of the southwest horizon and use binoculars to scan the sky.

This illustration show how the crescent moon will appear sandwiched between Saturn and Mercury after sunset from Miami, Florida. Nearby Venus acts as a convenient guidepost for finding this pretty conjunction of worlds. Credit: Starry Night Software/ A.Fazekas
This illustration depicts how the crescent moon will look sandwiched between Saturn and Mercury after sunset, as they will appear from Miami, Florida. Nearby Venus acts as a convenient guidepost for finding this pretty conjunction of worlds. Credit: Starry Night Software/A. Fazekas

The more southerly your location, the higher in the sky this event will appear. Sky-watchers in the Southern Hemisphere get a better view of the same event on October 7, with the crescent moon perched above the planetary pair much higher in the western sky after sunset.

Tell us—what amazing sky phenomena have you seen lately?

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Meet the Author
Andrew Fazekas, aka The Night Sky Guy, is a science writer, broadcaster, and lecturer who loves to share his passion for the wonders of the universe through all media. He is a regular contributor to National Geographic News and is the national cosmic correspondent for Canada’s Weather Network TV channel, space columnist for CBC Radio network, and a consultant for the Canadian Space Agency. As a member of the Royal Astronomical Society of Canada, Andrew has been observing the heavens from Montreal for over a quarter century and has never met a clear night sky he didn’t like.