Tales (Tails?) Of Three Comets

As the Chinese proverb says, “May you live in interesting times,” and while the promise of Comet ISON dazzling observers didn’t exactly pan out as hoped for in early 2014, we now have a bevy of binocular comets set to grace evening skies for northern hemisphere observers. Comet 2012 K1 PanSTARRS has put on a fine show, and comet C/2014 E2 Jacques has emerged from behind the Sun and its close 0.085 AU passage near Venus and has already proven to be a fine target for astro-imagers. And we’ve got another icy visitor to the inner solar system beating tracks northward in the form of Comet C/2013 V5 Oukaimeden, and a grand cometary finale as comet A1 Siding Spring brushes past the planet Mars. That is, IF a spectacular naked eye comet doesn’t come by and steal the show, as happens every decade or so…

Comet E2 Jacques crossing Cassiopeia as seen from the island of Malta. Credit: Leonard Mercer.

Anyhow, here’s a rapid fire run down on what you can expect from three of these binocular comets that continue to grace the twilight skies this Fall.

(Note that mentions of comets “passing near” a given object denote conjunctions of less than an angular degree of arc unless otherwise stated).

C/2014 E2 Jacques:

Discovered by amateur astronomer Cristovao Jacques on March 13th of this year from the SONEAR Observatory in Brazil, Comet E2 Jacques has been dazzling observers as it passed 35 degrees from the north celestial pole and posed near several deep sky wonders as it transited the constellation of Cassiopeia.

Comet E2 Jacques on August 28th as seen from the MVAS dark sky site in Yellow Springs, Ohio. Credit: John Chumack.

Mid-September finds Jacques 55 degrees above the NE horizon at dusk for northern hemisphere viewers in the constellation Cygnus. It then races southward parallel to the galactic equator, keeping in the +7th to +8th magnitude range before dropping down below +10th magnitude in late October. After this current passage through the inner solar system, Comet Jacques will be on a shortened 12,000 year orbit.

-Brightest: Mid-August at +6th magnitude.

-Perihelion: July 2nd, 2014 (0.66 AU).

-Closest to Earth: August 28, 2014 (0.56 AU).

Some key upcoming dates:

Sep 10: Passes the +3.9 magnitude star Eta Cygni.

Sep 14: Passes near the famous optical double star Albireo and crosses into the constellation of Vulpecula.

Sep 16: Passes in front of the +4.4 magnitude star Alpha Vulpeculae.

Sep 20: Crosses the Coathanger asterism.

Sep 21: Crosses into the constellation Sagitta.

Sep 24: Crosses into Aquila.

The celestial path of Comet Jacques from September 12th thru November 1st.
The celestial path of Comet Jacques from September 12th through November 1st. (All simulations created using Starry Night Education software.

Oct 5: Crosses the galactic plane.

Oct 14: passes near the +7.5 magnitude open cluster NGC 6755.

Oct 15: Drops back below +10th magnitude?

C/2013 V5 Oukaïmeden

Pronounced Ow-KAY-E-Me-dah, (yes, it’s a French name, with a very metal umlaut over the “ï”!) comet C/2013 V5 Oukaïmeden was discovered by the Moroccan Oukaïmeden Sky Survey (MOSS) located in the Atlas Mountains in Morocco. After completing a brief dawn appearance in early September, the comet moves into the dusk sky and starts the month of October located 38 degrees east of the Sun at about 14 degrees above the southwestern horizon as seen from latitude 30 degrees north at sunset. Southern hemisphere observers will continue to have splendid dawn views of the comet through mid-September at its expected peak. Comet Oukaïmeden is currently at +8th magnitude “with a bullet” and is expected to top out +6th magnitude in late September shortly before perihelion and perhaps remain a binocular object as it crosses the constellation Libra in October.

An early image of Comet C/2013 V5 Oukaimeden taken in February of this year. Credit: Efrain Morales Rivera.

And its also worth noting that as comet A1 Siding Spring (see below) makes a close physical pass by Mars on October 19th, Comet Oukaïmeden makes a close apparent pass by Saturn as seen from our Earthly vantage point the evening before! To be sure, the dusk apparition of Comet Oukaïmeden will be a tough one, but if you can track down these bright guidepost objects listed below, you’ll have a chance at spying it.

-Brightest: Mid-September.

-Perihelion: September 28th, 2014 (0.63 AU from the Sun).

-Closest to Earth: September 16th, 2014 (0.48 AU).

Some key upcoming dates:

Sep 10 through Oct 4: Threads across the borders of the constellations Hydra, Pyxis, Antlia and Centaurus.

Sep 18: Passes near the +3.5 magnitude star Xi Hydrae.

Sep 19: Passes near the +4.3 magnitude star Beta Hydrae.

Sep 25: Passes 1.5 degrees from the +8th magnitude Southern Pinwheel Galaxy M83.

Oct 1: Passes in front of the +10.2 globular cluster NGC 5694.

The path of Comet ... the Sun position is shown for the final date.
The path of Comet Oukaimeden through the month of October: The Sun position is shown for the final date.

Oct 3: Passes into Libra.

Oct 11: Passes near the +8.5 magnitude globular cluster NGC 5897.

Oct 16: Crosses the ecliptic plane northward.

Oct 18: Passes less than two degrees from Saturn.

Oct 25: Passes less than a degree from the 2 day old Moon and the +3.9 magnitude star Gamma Librae.

Light curve
The projected light curve for Comet Oukaimeden with observational measurements (black dots). Credit:  Seiichi Yoshida.

C/2013 A1 Siding Spring

This comet was discovered on January 3rd, 2013 from the Siding Spring observatory in Australia, and soon caught the eye of astronomers when it was discovered that it would make a nominal pass just 139,000 kilometres from Mars on October 19th.

Comet A1 Siding Spring as seen from NEOWISE early this year. Credit: NASA/JPL.
Comet A1 Siding Spring as seen from NEOWISE early this year. Credit: NASA/JPL.

As seen from the Earth, Comet A1 Siding Spring has just broken 10th magnitude and vaults up towards the planet Mars low to the southwest at dusk this Fall for northern hemisphere observers. A1 Siding Spring is expected to top out at +8th magnitude this month before its Mars encounter, and is on a one million year plus orbit.

-Brightest: Early to Mid-September.

-Perihelion: October 25th, 2014.

-Closest to Earth: October 28th, 2014 (1.4 AU).

Some key upcoming dates:

Sep 17: Passes into the constellation Telescopium.

Sep 20: Passes near the +8.5 magnitude globular NGC 6524.

Sep 21: Passes into the constellation Ara.

Sep 22: Passes the +3.6 magnitude star Beta Arae.

Sep 25: Crosses into Scorpius.

Sep 30: Passes the +3 magnitude star Iota Scorpii.

Mars and Comet A1 Siding Springs crossing paths through the month of October.
Mars and Comet A1 Siding Springs crossing paths through the month of October.

Oct 3: Passes near the +7.2 magnitude globular NGC 6441.

Oct 5: Passes 2 degrees from Ptolemy’s cluster M7.

Oct 8: Passes in front of the Butterfly cluster M6.

Oct 10: Crosses the galactic plane.

Oct 11: Crosses into Ophiuchus.

Oct 19: Passes just 2’ arc minutes from Mars as seen from Earth.

Oct 22: Passes north of the ecliptic.

Oct 30: Drops back below +10th magnitude?

Key moonless windows for evening comet viewing as reckoned from when the Moon wanes from Full to New are: September 9th to September 24th and October 8th to the 23rd.

Looking for resources to find out just what these comets and others  are up to? The COBS Comet Observers database is a great resource for recent observations, as is Seiichi Yoshida’s Weekly Comet page. For history and current info, Gary Kronk’s Cometography is also a great treasure trove to delve into, as are the Yahoo! Comet and Comet Observer mailing lists.

Be sure to check out these fine icy visitors to the inner solar system coming to a sky near you. We fully expect to see more outstanding images of these comets and more filling up the Universe Today Flickr forum!


NEOWISE Spots Mars-Crossing Comet

One of the big ticket astronomical events of 2014 will be the close passage of Comet C/2013 A1 Siding Spring past the planet Mars in October 2014. Discovered just over a year ago from the Australian-based Siding Spring Observatory, this comet generated a surge of excitement in the astronomical community when it was discovered that it was going to pass very close to the planet Mars in late 2014.

Now, a fleet of spacecraft are poised to study the comet in unprecedented detail. Some of the first space-based observations of the comet have been conducted by NASA’s Hubble Space Telescope and the recently reactivated NEOWISE mission. And although the comet may not look like much yet in the infrared eyes of NEOWISE, its estimated 4 kilometre in diameter nucleus is already active and shedding about 100 kilograms of dust per second.

And although an impact has been since ruled out, it’s that dust that may present a hazard for Mars orbiting spacecraft, as well as a unique scientific observing opportunity.

“Our plans for using spacecraft at Mars to observe Comet A1 Siding Spring will be coordinated with plans for how the orbiters will duck and cover, if we need to do so that,” said NASA/JPL Mars Exploration Program chief scientist Rich Zurek.

The 2014 passage of Comet A1 Siding Spring through the inner solar system. Credit: NASA/JPL-Caltech
The 2014 passage of Comet A1 Siding Spring through the inner solar system. Credit: NASA/JPL-Caltech

Comet A1 Siding Spring is projected to pass within just 138,000 kilometres of Mars on October 19th, 2014. This is one-third the Earth-Moon distance, and 10 times closer than the closest recorded passage of a comet by the Earth, which was Comet D/1770 Lexell in the late 18th century. The comet will also miss the Martian moons of Phobos and Deimos, which have the closest orbits of any moons in the solar system at just 5,989 and 20,063 kilometres above the surface of Mars, respectively.

Assets in orbit around the Red Planet are also slated to observe the close approach and passage of Comet A1 Siding Spring, as well as any extraterrestrial meteor shower that its dust may generate.

“We could learn about the nucleus – its shape, its rotation, whether some areas on its surface are darker than others,” Zurek said in a recent NASA/JPL press release.

The rovers Curiosity and Opportunity are currently active on the surface of Mars. Above in orbit, we’ve got the European Space Agency’s Mars Express, and NASA’s Mars Odyssey and the Mars Reconnaissance Orbiter (MRO).  These will be joined by India’s Mars Orbiter Mission and NASA’s Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft just weeks prior to the comet’s passage.

“A third aspect for investigation could be what effect the infalling particles have on the upper atmosphere of Mars,” Zurek said. “They might heat it and expand it, not unlike the effect of a global dust storm.”

Just last year, Mars based spacecraft caught sight of the ill-fated sungrazer Comet C/2012 S1 ISON as it passed Mars. But that dim passage yielded a scant pixel-sized view in the eyes of MRO’s HiRISE camera; Comet A1 Siding Spring will pass 80 times closer than Comet ISON and could yield a view of its nucleus dozens of pixels across.

Though the tenuous Martian atmosphere will shield to surface rovers from any micro-meteoroid impacts, they may also be witness to a surreptitious meteor shower from the debris shed by the comet, a first seen from the surface of another world.

But engineers will also be assessing the potential hazards that said particles may posed to spacecraft orbiting Mars as well.

“It’s way too early for us to know how much of a threat Siding Spring will be to our orbiters,” said JPL’s Mars Exploration Program chief engineer Soren Madsen recently. “It could go either way. It could be a huge deal or it could be nothing – or anything in between.”

In a worst case scenario, Mars orbiting spacecraft would be shuttered and oriented to “shelter in place” as the dust from the comet passes. There’s precedent for this in Earth orbit, as precious assets such as the Hubble Space Telescope were closed for business during the Leonid meteor storm of 1998.

“How active will Siding Spring be in April and May? We’ll be watching that,” Madsen continued. “But if the red alarm starts sounding in May, it would be too late to start planning how to respond. That’s why we’re doing what we’re doing right now.”

Comet A1 Siding Spring was the first comet discovered in 2013 at 7.2 Astronomical Units (AUs) distant. From our Earth based perspective, the comet will reach opposition on August 25th at 0.96 AU from the Earth, and approach 7’ from Mars on October 19th in the constellation Ophiuchus in evening skies. The comet reaches perihelion just 4 days later, and is slated to be a binocular comet around that time shining at magnitude +8.

The comet nucleus itself is moving in a retrograde orbit relative to Mars. Particles from A1 Siding Spring will slam into the atmosphere of Mars — and any spacecraft that happens to be in their way — at a velocity of 56 kilometres per second. For context, the recent January Quadrantids have a more sedate atmospheric impact velocity of 41 kilometres a second.

The unfolding 2014 drama of “Mars versus the Comet” will definitely be worth keeping an eye on… more to come!