Comets in the morning sky
BY MARK ARMSTRONG
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).
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.
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.
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.
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.
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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