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Comets in the morning sky
BY MARK ARMSTRONG
ASTRONOMY NOW

Posted: 13 November 2013


Comet enthusiasts are currently enjoying the spectacle of four bright comets visible in the morning sky. All the talk and speculation for months now has been, and still is, on 2012 S1 (ISON) and how bright it may get, or whether it will survive its perilous encounter with the Sun. But ISON, despite a recent surge in activity and brightness, is currently being upstaged by 2013 R1 (Lovejoy).


Comet 2013 R1 (Lovejoy) is a great looking comet and the brightest in the morning sky at the moment. This marvellous image of Lovejoy's encounter with the Beehive open cluster (M44) in Cancer was taken by Damian Peach on 7 November.
 
Lovejoy is at least two magnitudes brighter and much brighter than predicted, four magnitudes, in fact, according the the ephemeris at the Minor Planet Center. Also on show is 2P/Encke, the comet with the shortest period, returning every 3.3 years and the outbursting 2012 X1 (LINEAR).

Lovejoy looking great

The brightest comet of the four and the first that can be observed is 2013 R1 (Lovejoy), the fourth comet discovered by Australian observer Terry Lovejoy. It was he who discovered the marvellous sungrazing comet 2011 W3 (Lovejoy) and bagged 2013 R1 in September. It has a 7000-year period and is in a highly inclined orbit, 64 degrees to the ecliptic (the mean plane of the Earth's orbit and the apparent path of the Sun on the celestial sphere). Lovejoy passes 61 million kilometres from Earth (0.4 AU) on 19 November and is a perihelion (closest to the Sun) on 22 December at 0.8 AU.

The latest observations and images show Lovejoy at around magnitude +5.5 with a coma some 15 to 18 arcminutes in diameter and a two-degree diffuse tail. It is an easy binocular object in good skies but from moderately light-polluted sites a small telescope, say a 100-mm, might be a better option to track it down.


Lovejoy is a great looking comet visible around midnight. This is its path for the rest of November. AN graphic by Greg Smye-Rumsby
 
Comet Lovejoy is making a fleeting visit to northern Leo tonight (Nov 13/14) and will be 20 degrees up in the east-north-east at midnight GMT from London. By the end of the astronomical night at 5.15am (Sun less than 18 degrees below the horizon), Lovejoy will have climbed to a very favourable altitude of 65 degrees. As the month progresses, the comet steams north through Leo Minor, Ursa Major, Canes Venatici and Bootes. Its observing window from the UK will diminish a bit; on 28/9 November it moves into northern Bootes but won't get 20 degrees up until 2am and is 50 degrees up at 5.40am, the end of the astronomical night. It should peak at magnitude +4 around this time.

Seeing Lovejoy in the USA

Comet 2013 R1 (Lovejoy) is superbly placed across North America for the whole of November, although, like in the UK, its observing window closes as the month progresses but as a compensation it will brighten. On the night of 14/15 November from New York, Lovejoy rises at 10pm EST, climbs to 20 degrees by 12.30am and culminates at 5.30am a whopping 75 degrees up. From Miami it rises an hour later and gets to 20 degrees altitude at 1.30am. By the end of the night at 5.45 it's 75 degrees up, too. Over in the west in Los Angeles, Lovejoy rises at 10.40pm, is above 20 degrees altitude two hours later and is nearly 80 degrees up by the time the morning twilight starts to interfere too much with observations.

By the end of November, the comet should be at its brightest, but from Miami there's only a 75-minute observing window up to 6am EST. Things are better across in LA, with a 1 hour, 50 minute observing time up to 5.40am and best of all in New York, where Lovejoy is above 20 degrees for two-and-a-half hours up to 6am.

Lovejoy down under

There are only a few days to see the comet before it heads too far north. On 15 November at the end of the night (4.45am AEDT in Sydney and 4.10am AWST in Perth) the comet is just short of 20 degrees up in the north-eastern morning sky.

2012 X1 (LINEAR) in outburst

Comet 2012 X1 (LINEAR) was a run-of-the-mill 14th magnitude comet until an outburst last month transformed it into a comet Holmes-like object, glowing at mag. +8.5 with an expanding coma. The very latest observations have it at mag. +7.5 with a very diffuse coma, which some visual observers report as large as 15 arcminutes. The latest images show the coma is distinctly oval in shape and there is no obvious tail. 2012 X1 is not easy to observe, especially in suburban skies, as it is so diffuse.


Comet 2012 X1 (LINEAR) is still in outburst and well placed in the morning sky. Image by Damian Peach on 6 November.
 
A plus point at the moment is it's very easy to find lying two degrees north west of Arcturus. It rises around 2.30am and hauls itself 20 degrees above the eastern horizon by 5am. 2012 X1 has climbed to 33 degrees up before the morning twilight kills the night around 6.30am. The comet will track eastwards through Bootes, coming within a degree of Arcturus on 17/18 and 18/19 November and will be at perihelion next February.

LINEAR in America

Comet 2012 X1 (LINEAR) is a morning object visible for a while low down in the pre-dawn eastern sky. On 14/15 November from New York and Los Angeles it climbs to an altitude of 25 degrees at 5.30am local time, five degrees less from Miami at 5.45am. By the end of November, it's a few degrees better off across the whole of the USA. Unfortunately, the comet is not visible from Australia and New Zealand at this time.

ISON; comet of the century?

To everybody's delight comet 2012 S1 (ISON) is finally shaping up, in the last week brightening to mag. +7.7 to +8, depending on whose estimate you take; it's definitely visible as a soft glow in 10 x 50 binoculars. The comet's tail has lengthened to at least half a degree, the width of the full Moon, and the coma is around five to seven arcminutes across. Astronomers report that the rate of ISON's gas production has increased rapidly over the last several days which, according to one scientist, could indicate melting of deeper layers of ice. ISON was reported to be intact still last month, so this enhanced activity does not appear to be the result of any disruption or breaking up of the comet, astronomers added.


ISON's track across the sky. AN graphic by Greg Smye-Rumsby
 
ISON is currently guesting among the stars of Virgo lying 4.5 degrees south of Porrima (gamma), rising at 3.40am GMT from London and reaching the crucial 20 degree altitude mark around 6am. Take any opportunity you get to observe it over the next few nights, as soon after mid-month it becomes too low over the horizon to observe as it zooms east through Virgo. Making predictions where comets are concerned can be a fruitless exercise, but ISON should brighten by a couple of magnitudes before it disappears into the Sun's realm, maybe even becoming a naked-eye object at dark sites. Hopefully ISON will be unscathed after its close encounter with the Sun and will emerge into bright morning skies in early December.

Viewing ISON across the pond

ISON is visible at the moment in the USA, with more northerly states favoured. In Miami, the comet is only 11 degrees up at when the twilight kills the night at 5.45am EDT. By the time the comet is close to the end of its pre-perihelion apparition on 22 November that altitude has decreased to eight degrees. In New York, ISON gets 22 degrees up by 5.30am but plummets to a lowly five degrees by 22 November. Observers in LA gain a few degrees over New York.

ISON in Australia

ISON can be seen as long as your observing site has a clear horizon, although it will be painfully low. On November 15, the comet is only 12 to 13 degrees up at the end of the observing night in eastern Australia (Sydney and Brisbane), with similar circumstances over in the west in Perth. A week later the comet has sunk to five degrees at the end of the night, less than a week before perihelion on 28 November.

Reliable Encke grows a tail

Comet 2P/Encke will be the poorest placed of the four, only getting 13 degrees up by 6.30am on the morning of 14 November from London. Like ISON, it is resident in Virgo, only seven degrees east of Spica and 4.5 degrees north-west of the planet Mercury (mag. -0.2). It's as bright as mag. +7 at the moment so large binoculars or a small telescope at low power should bag it if you can get access to an observing site with an unobstructed east-south-east horizon.


Comet 2P/Encke is a very good looking comet with a nice tail. Observe it now before perihelion. Image by Damian Peach on 30 October
 
Images last month by prolific UK imager Damian Peach showed the comet sprouted a narrow ion tail in late October. Encke is at perihelion on 21 November and is lost to the twilight then; after perihelion, it's a Southern Hemisphere object.

Encke in America

2P/Encke is poorly placed now across America as it barely rises 10 degrees in New York, Miami and Los Angeles before the morning twilight puts an end to things. Encke is not visible in Australia and New Zealand this side of perihelion.

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