Follow Comet Wirtanen


Comet Wirtanen / 46P on December 6, 2018

A well-known comet is making its closest approach to Earth in many years and promises a good show. 

Comet Wirtanen is now climbing up the late autumn and winter sky for northern hemisphere viewers, and is already a fine binocular comet. By mid-December it might be bright enough to be visible to the naked eye, but only from a dark rural site.

Discovered in 1948 by Carl Wirtanen at the Lick Observatory, his namesake comet orbits the Sun every 5.4 years. So unlike other recent bright comets that have visited us for the first time, Comet Wirtanen (aka 46P) is well known. It is one of many “Jupiter-family” comets whose orbits have been shaped by the gravity of Jupiter and orbit the Sun about every 6 years.

So since it was discovered, Comet 46P (the 46th comet in the catalog of periodic comets) has been well observed. It isn’t better known because at most returns it never gets bright, and that’s because it never gets closer to the Sun than a little more than the distance from the Earth to the Sun. (Its perihelion distance is 1.06 AU, with 1 AU, or Astronomical Unit, being the average distance from Earth to the Sun.)

However, despite this, we’re expecting – indeed already enjoying – a good show at this return.

Due to the quirk of orbital clockwork, on this return the comet reaches its closest point to the Sun just before it is also closest to Earth.

That puts the comet “just” 11,680,000 kilometres from us at its closest approach to Earth on December 16, four days after perihelion, the point when the comet is closest to the Sun.

Comet Wirtanen from Space
The relative position of the Sun, Earth and Comet Wirtanen on December 16, 2018.

Comet Wirtanen will be relatively bright simply by virtue of its proximity.

But it is also an active comet, emitting a lot of gas and dust into a large “coma,” and that’s what we see, not the 1-kilometre-wide icy nucleus itself which is too small and shrouded by the coma. (As a footnote, Comet Wirtanen was to have been the comet that the European Rosetta probe was to visit, but launch delays forced ESA to switch cometary targets.)

Comet Wirtanen is glowing at magnitude 5 to 6, technically making it visible to the naked eye. However, because it is large and diffuse, in practice you need binoculars to see it – now.

But as it approaches Earth and the Sun, Wirtanen will brighten, perhaps to magnitude 3 (the brightest stars are magnitude 0 to 1), making it easier to see with the unaided eye from a dark site.

The one catch is that as it heads toward its brightest in mid-December the waxing Moon also begins to enter the sky and wash out the comet with moonlight.


The first two weeks of December will be prime time for Wirtanen


Comet Wirtanen Path
The path of Comet Wirtanen across the sky in December 2018. The yellow dots mark the position of the comet at nightly intervals for late evening (10 p.m.) for North America. While comet will be in the sky most of the night, it will be highest in late evening about 10 p.m. local time when the sky will look as depicted, with the comet high in the south to southeast. Click or tap to download a full-sized version.

The first two weeks of December will be prime time for Wirtanen, with a particularly good opportunity coming on the evenings of December 15 and 16 when it shines below the Pleiades star cluster. The gibbous Moon will set about 1 to 2 a.m. with the comet still high enough for a dark sky view and photos.

Those will be great nights to shoot the comet and the cluster with a telephoto lens, provided the camera is on a tracker for untrailed exposures of 1 to 4 minutes. A 135mm to 300mm lens will frame the pair well.

Winter Green Comet with Orion
Comet Wirtanen as a green glow at upper right here in Eridanus. and well to the west of Orion, rising here at left, on the evening of December 6, 2018. I shot this with a wide-angle 35mm lens in a blend of tracked and untracked 1-minute exposures.

After that, through late December, the bright Moon will interfere with  the view. For example, a close approach of the comet near the star Capella on December 23 happens with the nearly Full Moon not far away.

Comet Wirtanen / 46P on December 6, 2018
Comet Wirtanen in a close-up through a telescope on December 6, 2018 in a stack of short and long exposures.

I took the above close-up photo of Comet Wirtanen on December 6. It is a long-exposure telescopic view, but the comet is easy to see with binoculars. It appears visually and photographically as a diffuse fuzzball, with the camera recording a vivid cyan colour from glowing cyanogen and diatomic carbon molecules. You won’t see that colour with your eyes, even in a telescope.

Comet Wirtanen Path Dec 8 to 16
The path of Comet Wirtanen Dec 8 to 16 superimposed on an actual sky image with the comet taken December 8. The circle indicates the field of view of typical binoculars. On Dec 15 and 16 the comet will be in the same binocular field as the Pleiades star cluster. The positions are for about 10 pm Mountain Standard Time for each of those dates.

Even at the comet’s best in mid-December any tail might be hard to see and even photograph (it appears faintly above) as it will be both faint and pointed directly away from us because, as comet tails do, it will also be pointed away from the Sun.

Look for a large glow which will be grey to the eye but green to the camera.

While you can just take pictures for yourself, astronomers are asking amateur astrophotographers to participate in a worldwide observing campaign to monitor Comet Wirtanen. More details are available here at wirtanen.astro.umd.edu and at http://aop.astro.umd.edu/

Clear skies and happy comet hunting!

— Alan, November 30, 2018 (Revised December 6) / © 2018 Alan Dyer / AmazingSky.com 

My 2019 Amazing Sky Calendar


2019 Amazing Sky Calendar Cover

My annual Amazing Sky Calendar is out!

My 2019 Amazing Sky Calendar is now out and available for FREE download as a PDF from my website page.

Once you’re on that page, scroll down for the link to the PDF.

Each month includes many dates and diagrams for celestial sights and space exploration events and anniversaries.

You can then print the PDF locally if you wish.

Do share the web page URL or this blog post. However, the PDF itself is for your personal use only. Enjoy!

— Alan, October 1, 2018 / © 2018 Alan Dyer / www.amazingsky.com

 

 

Mars and Jupiter in the Morning


Jupiter and Mars at Dawn

Mars and Jupiter are meeting up in the morning sky. Soon they’ll be joined by the Moon.

Here’s a heads up for one of the best planet conjunctions of the year. Mars and Jupiter are now close together in the dawn sky to the south, and getting closer!

Above is the actual view on the morning of January 4, with Jupiter the brightest of a trio of objects. Mars is reddish and in the middle. The object at right is the star Alpha Librae, also known as Zubenelgenubi in Libra.

Jan 6 Morning Sky
Looking south-southeast on January 6

As shown in the simulation above, on the morning of January 6 Mars and Jupiter will be only 1/3rd of a degree apart (20 arc minutes), so close that dimmer Mars might not be obvious to the naked eye next to bright Jupiter. But use binoculars to show the planet pair.

The next morning, on January 7, they will appear almost as close, as Jupiter climbs higher past Mars.

Jan 11 Morning Sky
Looking south-southeast on January 11

As shown here, on the morning of January 11 the waning crescent Moon will sit only 4 degrees from the planet pair, with all three worlds gathered close enough for binoculars to frame the scene.

With sunrise coming late on winter mornings, it doesn’t take an early rise to take in the dawn scene. Make a note to take a look about 6:30 to 7:00 a.m. over the next week.


POSTSCRIPT added January 6:

Here’s the real scene from the morning of January 6, with Mars and Jupiter just 16 arc minutes apart, very close but still easy to distinguish  with the naked eye. Jupiter did not overwhelm Mars.

Jupiter and Mars in Conjunction at Dawn

Thanks and Clear skies!

— Alan, January 4, 2018 / © 2018 Alan Dyer / amazingsky.com

Chasing Meteors


Geminid Meteor Radiant in Gemini

Meteors were raining down the sky on the peak night of the Geminid meteor shower.

Back in August, when I wrote my column for the November-December issue of our Canadian magazine SkyNews, I noticed how good the circumstances were this year for the annual Geminid meteor shower. Normally one of the best showers of the year, if not the best, the Geminids were really going to perform in 2017.

The Moon was near new so its light would not interfere. For western North America, the peak of the shower was also timed for midnight on the night of December 13/14, just when the radiant of the shower was high in the sky.

Raining Geminid Meteors
The Geminids rain down the sky from the radiant in Gemini high overhead on peak night.

So in August when I saw the favourable combination of circumstances, I decided a meteor chase was in order. While the shower would be visible from home, Geminid peak night in December is often bitterly cold or cloudy at home in Alberta.

So I planned a trek to Arizona, for the shower and the winter sky.

While skies at home proved decent after all, it was still a chase worth making, with the shower visible under the perfectly clear and dry skies of southeast Arizona.

My chosen site was the Quailway Cottage near the Arizona Sky Village, the chosen dark sky site for many amateur astronomers, and at the foot of the Chiricahua Mountains. Skies are dark!

Sky Dust - Interplanetary and Interstellar
The Zodiacal Light (left) and Milky Way over the Chiricahuas.

The Zodiacal Light was brilliant in the southwest sky for several hours after sunset. A tough sighting at this time of year from most sites, this glow was obvious in the Arizona sky. It is sunlight reflecting off cometary dust particles in the inner solar system.

Geminid Meteor Shower in the Winter Milky Way
Geminids streaking from Gemini as the winter sky rises.

On the peak night, the visual impression was of meteors appearing at a rate of at least one a minute, if not more frequently.

Geminid Meteor Radiant in Gemini
A tracked composite looking up toward Orion and Gemini.

The images here are all composites of dozens of exposures taken over 2 to 5 hours, stacking many meteors on one frame. So they do provide an exaggerated record of the shower. Meteors weren’t filling the sky! But you certainly did not have to wait long for one to appear, making this one of the best meteor showers in many years.

Geminid Meteors over the Chiricahuas
Geminids falling over the Chiricahuas as Orion sets at the end of the peak night.

Most of the Geminids were of average brightness. I didn’t see, nor did the camera catch many very bright “bolides,” the really brilliant meteors that light up the ground.

Bright Geminid Meteor Descending
A bright Geminid pierces Ursa Major.

Nevertheless, this was a night to remember, and a fine way to end what has been a superlative year of stargazing, with a total solar eclipse, great auroras, and for me, a wonderful stay under southern skies on an April trip to Australia.

All the best of the season to you and your family and friends. Clear skies!

Here’s to 2018, which begins with a total eclipse of the Moon on January 31.

— Alan, December 23, 2017 / © 2017 Alan Dyer / AmazingSky.com

 

Conjunctions, Satellites & Auroras, Oh My!


Friday the 13th Aurora Title

October has brought clear skies and some fine celestial sights. Here’s a potpourri of what was up from home. 

We’ve enjoyed some lovely early autumn weather here in southern Alberta, providing great opportunities to see and shoot a series of astronomical events.


Conjunctions

Venus & Mars in Close Conjunction #2 (Oct 5, 2017)
Venus and Mars in close conjunction in the dawn sky on October 5, 2017. Venus is the brightest object; Mars is below it; while the star above Venus is 4th magnitude Sigma Leonis. The foreground is illuminated by light from the setting Full Moon in the west. This is a single 1-second exposure with the 135mm lens at f/2 and Canon 60Da at ISO 800. 

On October 5, Venus and Mars appeared a fraction of a degree apart in the dawn twilight. Venus is the brightest object, just above dimmer but red Mars. This was one of the closest planet conjunctions of 2017. Mars will appear much brighter in July and August 2018 when it makes its closest approach to Earth since 2003.


Satellites: The Space Station

Overhead Pass of the Space Station in Moonlight
An overhead pass of the ISS on October 5, 2017, with the Full Moon rising in the east at left. The ISS is moving from west (at right) to east (at left), passing nearly overhead at the zenith at centre. North is at the top, south at bottom in this fish-eye lens image with an 8mm Sigma fish-eye lens on the Canon 6D MkII camera. This is a stack of 56 exposures, each 4 seconds long at an interval of 1 second. 

The Space Station made a series of ideal evening passes in early October, flying right overhead from my site at latitude 51° N. I captured it in a series of stacked still images, so it appears as a dashed line across the sky. In reality it looks like a very bright star, outshining any other natural star. Here, it appears to fly toward the rising Moon.


Satellites: Iridiums

Twin Iridium Satellite Flares (October 9, 2017)
A pair of nearly simultaneous and parallel Iridium satellite flares, on October 9, 2017, as they descended into the north. The left or westerly flare was much brighter and with a sharp rise and fall in brightness. While it was predicted to be mag. -4.4 I think it got much brighter, perhaps mag -7, but very briefly. These are Iridium 90 (left) and Iridium 50 (right). This is a stack of 40+ exposures each, 2 seconds at 1-second intervals, with the Sigma 24mm lens at f/1.4 and Nikon D750 at ISO 6400.

Often appearing brighter than even the ISS, Iridium satellite flares can blaze brighter than even Venus at its best. One did so here, above, in another time-lapse of a pair of Iridium satellites that traveled in parallel and flared at almost the same time. But the orientation of the reflective antennas that create these flares must have been better on the left Iridium as it really shot up in brilliance for a few seconds.


Auroras

Aurora and Circumpolar Star Trails (Oct, 13, 2017)
A circumpolar star trail composite with Northern Lights, on October 13, 2017, shot from home in southern Alberta. The Big Dipper is at bottom centre; Polaris is at top centre at the axis of the rotation. The bottom edge of the curtains are rimmed with a pink fringe from nitrogen. This is a stack of 200 frames taken mostly when the aurora was a quiescent arc across the north before the substorm hit. An additional single exposure is layered in taken about 1 minute after the main star trail set to add the final end point stars after a gap in the trails. Stacking was with the Advanced Stacker Plus actions using the Ultrastreaks mode to add the direction of motion from the tapering trails. Each frame is 3 seconds at f/2 and ISO 6400 wth the Sigma 14mm lens and Nikon D750.

Little in the sky beats a fine aurora display and we’ve had several of late, despite the Sun being spotless and nearing a low ebb in its activity. The above shot is a composite stack of 200 images, showing the stars circling the celestial pole above the main auroral arc, and taken on Friday the 13th.

Aurora from October 13, 2013
A decent aurora across the north from home in southern Alberta, on Friday the 13th, October, 2017, though these frames were taken after midnight MDT. 3 seconds at f/2 and ISO 6400 wth the Sigma 14mm lens and Nikon D750.

This frame, from some 1300 I shot this night, October 13, captures the main auroral arc and a diffuse patch of green above that pulsed on and off.

You can see the time-lapse here in my short music video on Vimeo.

Friday the 13th Aurora from Alan Dyer on Vimeo.

It’s in 4K if your monitor and computer are capable. It nicely shows the development of the aurora this night, from a quiescent arc, through a brief sub-storm outburst, then into pulsing and flickering patches. Enjoy!


What all these scenes have in common is that they were all shot from home, in my backyard. It is wonderful to live in a rural area and to be able to step outside and see these sites easily by just looking up!

— Alan, October 16, 2017 / © 2017 Alan Dyer / AmazingSky.com 

 

Dawn Sky Delights


Aldebaran About to be Occulted by the Moon

It was one of those mornings when the sky was full of wonder.

After days and nights of smoke from unfortunate fires burning not far away, including in my favourite national park of Waterton Lakes, the sky cleared enough this morning, September 12, to reveal some fine sights.

At 6 a.m. the waning gibbous Moon passed in front of the star Aldebaran in Taurus. It is performing many such occultations of Aldebaran this year, but most aren’t well seen from any one location. This one was ideal, right from my backyard.

The lead image is a “high dynamic range” stack of several exposures showing the waning Moon and star set in some high haze adding the sky colours.

The star winked out behind the Moon’s bright limb as the Moon advanced from right to left (west to east) against the background sky.

Occultation of Aldebaran
Aldebaran nearing the limb of the Moon.
This shows a composite sequence, with images of the star taken every four minutes blended with a single image of the Moon. While it looks like the star is moving, it is really the Moon that is edging closer to Aldebaran.

The star reappeared from behind the dark limb of the Moon, but five minutes after sunrise, with the Moon in a bright blue sky. Still, the star stood out nicely in binoculars and in the telescope for this view.

Aldebaran Near the Moon in Day Sky
Aldebaran off the dark limb of the Moon.
Aldebaran is the point of light at right, just off the invisible edge of the Moon.

I shot stills and video, and compiled them into this short video.

Enlarge it to full screen to view it properly.

Meanwhile, over to the east the twilight sky was awash in planets.

Rocky Planets at Dawn with Labels (Sept. 12, 2017)
The line of dawn planets, with labels.
All the three inner terrestrial worlds were there: Venus, at top, Mercury below Regulus, and Mars lowest of the trio. Of course, a fourth terrestrial world is in the photo, too – Earth!

Mercury was at its greatest western elongation this morning, placing it as far from the Sun and as high in the sky as it gets, with this autumn appearance the best of 2017 for a morning showing for Mercury. Even so, you can see how Mercury is always low and easy to miss. However, this morning it was obvious to the naked eye.

Mars and Mercury will be in close conjunction at dawn on the morning of September 16.

Rocky Planets at Dawn (Sept. 12, 2017)

It was a fine morning to be up early and enjoy the solar system show.

— Alan, September 12, 2017 / © 2017 Alan Dyer / amazingsky.com

 

End of Year Skies


New Moon for a New Year

The crescent Moon rises into the western evening sky as 2016 ends, while Venus shines bright, and Orion rises into the east.

Getting clear skies is a rare treat of late, but these are images from two such nights this week. On December 30, the thin waxing Moon appeared in the colourful twilight of a winter night. Despite the clouds and the Moon’s low altitude, the dark side of the Moon is plainly visible illuminated by Earthshine.

Venus in Twilight over Pioneer Grain Elevators

Venus is now brilliant as an evening star in the southwest. Here is it over the old wood grain elevators at Mossleigh, Alberta, some of the few of these landmarks left standing on the prairies.

Fainter Mars shines above Venus and over the month of January, Venus will climb up to meet Mars by month’s end for a fine conjunction with the crescent Moon as well. Watch through January as Venus and Mars converge.

Orion and Pioneer Grain Elevators

As the planets set into the southwest, Orion the Hunter rises into the east. Here it is over the Mossleigh elevators, illuminated by local lights.

Enjoy the winter skies as clouds permit!

Clear skies and Happy New Year!

— Alan, December 31, 2016 / © 2016 Alan Dyer / www.amazingsky.com