Christmas Comet? Maybe


A Comet for Christmas?
by John Hlynialuk

While there has been no lack of planetary activity to enjoy in the night sky (Venus, Jupiter and Mars!), one celestial spectacle has been missing for a long time. We have not had a bright comet for a dozen years or so and any that have shown up have required telescopes or binoculars to see. The most recent one was Comet 26P/Giacobini-Zinner and it was captured nicely on camera by Frank W. See the
HOME page.

We are long overdue for a really bright comet and although I would like to report otherwise, the comet predicted for Christmas will be a good comet, but not likely a spectacular one. However, as one famous comet hunter, David H. Levy commented, “Comets are like cats: they have tails and do precisely what they want.”

Of all celestial objects, comets are the most elusive and most unpredictable. Astronomers know many of their orbits with high precision, but their behaviour when these chunks of frozen ice and gas get near the Sun is much less certain. Many do not brighten on schedule, some break up or get destroyed by a close pass to the Sun and others burst forth in spectacular fashion. The most famous example of a much-ballyhooed comet that flopped was Comet Kohoutek in 1973. I tried more than once to catch a glimpse of Kohoutek and failed, and my better half notes (with glee) that she spotted it casually during a snowmobile ride on a frozen lake in the Peterborough area. (That was in our pre-courting days, so it does not really count.)

As in the case of Comet Kohoutek, comets can be a complete fizzle, or they can totally defy predictions and be easily seen even from our brightly-lit cities. The last such comet was Comet Hale-Bopp in 1997 with a spectacular show for over a year remaining visible to the naked eye for 18 months. But who remembers Comet Hyakatake? This one appeared a year before Hale-Bopp, had a larger tail, and came closer to Earth (a close shave of only 15 million km) than the 200 million km wide pass of Hale-Bopp.
23HyakApr:96Hale-Bopp-comet-1997_edited-1
Image left: Comet Hyakatake imaged from April 1996 Image right: Comet Hale-Bopp at its best in March 1997 Both images by John H.

Unfortunately Hyakatake only appeared for 3 months in 1996 during typically cloudy spring weather, and you had to be dedicated to spot it. I had learned a lesson with Kohoutek, and thankfully, the weather cooperated, so I did observe and photograph it on several occasions.

This Christmas, Comet 46/P Wirtanen is expected to appear in our skies, and away from city lights (and moonlight), it may be an interesting sight. Due to be brightest during the later part of 2018 and early January 2019, predictions (for what those are worth) are that it may get to be visible to the naked eye, -but don’t expect another Hale-Bopp.

Comet 46/P Wirtanen was preceded by another, a summer comet, Comet Giacobini-Zinner, and if predictions are borne out, Comet 46/P will be better than Comet G-Z and should peak late in the year. The best times to view will be during Moon-free periods in the first two weeks of December and again in the first part of January 2019. Full Moon occurs Dec 22 and Wirtanen will not likely be seen over the bright moonlight. But if you can dodge the moon by waiting for it to set, Wirtanen will be above the horizon all night long from mid-December into the new year. For a chart showing the path of 46/P from Dec 1 to Christmas Day see below:
Wirtanen-Dec-1-to-25

Additional information about Comet 46P/ can be found on the VIS.COMETS page. Click on the map to download a copy. Good luck with your comet viewing!

A Demon Star for Halloween

by John Hlynialuk
A traditional depiction in mythology of Perseus is shown below. This is
plate 6 in Urania's Mirror by Jehoshaphat Aspin, London, 1824. One of 32 hand-coloured constellation cards, the set depicts most of the familiar constellations as works of art rather than what is seen in modern atlases which strive for accuracy in star position, brightness, type, etc. and provide no fanciful artwork at all. Pity.

Perseus_800K

There are many interesting stars in Perseus but at this time of year when the ghouls are out, we pick on Algol the Demon Star. Modern astronomers have dug deep and revealed an extra-ordinary story.

The second brightest star in Perseus, Algol, has a name which translates from Arabic as “head of the ogre”, original: “ra’s al ghul”, a creature who stalked graveyards and consumed human flesh. There is also the obvious connection to our word “ghoul.” So from ancient times, Algol has been called the Demon Star.

In the myth associated with the Demon Star, innocent Andromeda is on the verge of being dismembered for being beautiful (it was her mother’s boast that got her into trouble, actually). Our hero, Perseus is returning with the severed blood-soaked head of Medusa (she had a bad hair day) and saves Andromeda from Cetus the Sea Monster by turning the monster into stone. There are (unconfirmed) reports that more than one of the Greek islands are the site of the monstrous body, -check the tourist literature.

By the end of the mythological saga, Perseus, Andromeda, her boastful mother -Queen Cassiopeia and her father, King Cepheus become constellations in the sky, -even Cetus is there a bit further off. The classical depiction of Perseus (in the image above) shows Algol, the Demon Star, as one of Medusa’s eyes. But like only a few other stars in the heavens, Algol actually changes its light output visibly! It’s as if Algol, the Demon Eye of the Medusa, is winking at us. It is certainly a relief that she is 98.2 light years away, well beyond turning-to-stone range.

It is not definitively known if ancient myth-makers noticed Algol’s variation and built it into their stories, but by 1783, English astronomer John Goodricke showed that the variable Algol had a very regular period indeed. This unique discovery gained Goodricke the Royal Society’s Copley Medal, a prize first awarded in 1731 and still presented annually today. Algol’s precise clock-like variations occur over 2 days, 20 hours and 48.9 minutes. During that time, it fades for exactly 10 hours and then brightens back to normal. Repeat 2.86730 days later.

The variability of Algol lies in the fact that it is actually three stars and two orbit each other so that they pass directly in front of each other from our perspective. The combined light output drops during the 10 hour eclipse which gives these stars their type name: eclipsing binaries. Algol was the first variable recognized as such and is one of only a few that can be noticed by the naked eye. It’s like Medusa is continually trying to change us to stone, -with a 10 hour wink- thank goodness the “petrification energy” gets totally diluted over the vast distance.


An ordinary star chart is provided below (Credit IAU and Sky&Tel) to help you locate Algol in Perseus. It is usually easy because it spends most if its time as the second brightest star in Perseus after Mirfak. Algol is usually a magnitude 2.1 star and only drops to magnitude 3.3 every 2.86736 days for about 10 hours. So you need a schedule to tell you when the eclipse will happen during a time when Algol is in the night sky. There are four good chances in October and these are given at the end of this article.

IAU Perseus


The light curve diagram provided here for Algol shows the two dips in its brightness as each of the two stars eclipse each other. The primary eclipse occurs when the larger, cooler, dimmer Algol B partially hides the smaller, hotter, brighter, more massive Algol A. The secondary eclipse is when Algol A hides Algol B.

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The times when an eclipse occurs are provided in various publications or online. Google “Algol minima” for some of those. In any case, the next good opportunities to see Algol blink at us are Oct 18 at 2:09 am when Perseus is high in the sky. Then on Oct 21, at 22:58 EDT (about 11 pm) with Perseus still high in the east, and Oct 23 with an eclipse starting at 19:47 EDT (7:47 pm Perseus above NE horizon). The last opportunity in October is Oct 26 with an eclipse starting at 4:36 pm EDT. By mid-eclipse Perseus should be high enough above the NE horizon for Algol to be seen. You can watch the star come back out of eclipse in the wee hours of the morning, around 2:30 am or so.

Miulky Way/Summer Triangle last hurrah

Summer Triangle: Best in Autumn
by John Hlynialuk
Bluewater Astronomical Society

In October, we are officially into fall but the night sky is still in summer mode. The two summer astronomical objects on prominent display are the summer Milky Way and the Summer Triangle, and it will be well into winter before both disappear below the western horizon. So let’s say a proper goodbye to the summertime night sky.


Sum-Tri-MW


For the next few months, when clouds part long enough at night for you to see anything, the Milky Way stands vertically over the SW horizon and stretches overhead and behind you. At a dark sky location, you can follow the glow of our home galaxy right to the northeastern horizon. Star charts are available on the BAS website www.bluewaterastronomy.com under the CHARTS/FORMS tab and also at www.skymaps.com and an all-sky chart is included here. Start by looking southwards and locate the most obvious patch of Milky Way just above the southwestern horizon. The constellation there is Sagittarius, looking like a teapot tipped somewhat to the right. Say a hello in passing to Saturn just off the lid of the teapot. Now follow the Milky Way glow up to Aquila and overhead to Cygnus. Then turn around, face north and continue down past Cassiopeia to Perseus low above the northeastern horizon. At a dark site you should be able to trace the glow of the millions of stars that make up the Milky Way from horizon to horizon. The glow is more obvious in Sagittarius because you are looking itoward the centre of the galaxy where more stars are concentrated. In the opposite direction, looking past Perseus, you are gazing out into the less starry regions beyond the edge of our home in the Universe.

To locate the Summer Triangle, find the bright “alpha” stars of Cygnus, Lyra and Aquila. This is not hard as these constellations are straight up at the zenith right now. Look for the three brightest stars that together form a large right-angled triangle. Those stars are Deneb, Vega and Altair, -hints are on the chart.

It will be several months before this asterism disappears completely and even at years-end, Deneb will still be visible before midnight above the NW horizon. In December, of course, no one will be thinking about summer and the only “Milky Way” will probably be steam rising from mugs of hot chocolate as hardy stargazers check out our winter constellations.

As for other sky objects, there are only two bright planets left in the night sky, Mars and Saturn. Venus is lost in solar glare low in the west and Jupiter is close behind. Both drop quickly into the western sunset glow and by 9 pm, the time of the included chart, both have disappeared. The remaining planets, Saturn and Mars, are not labelled on the chart but they are not hard to find, -both are bright enough to be the first “stars” you see at night.

Let’s hope for a few nice, not too frosty, autumn nights to catch the last of the offerings of the summer sky. And if it is too cloudy, do some armchair astronomy by reading my weblog on the BAS website.

Clear skies!

Dust Storm Starting to Subside

Evidence Martian Dust Stom is Subsiding:
by John Hlynialuk



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A frame from the animation created by astrophotographer Damian Peach showing a global dust storm on Mars.
Credit:
Damian Peach
More on this animation here: Damian Peach animation



Recent reports (July 27) indicate that the worst is over for the Martian dust storm and the dust seems to be subsiding. We are not out of the woods yet, however, as it can take several months for the atmosphere to clear to pre-storm levels. The worst possible scenario is for another storm to start up, as it is dust storm season in the southern hemisphere on Mars.

Hopefully, the atmosphere will clear up and viewing of surface features will get back to “normal” very soon, perhaps by the end of August.

The article quoted here from www.space.com gives the current status of the dust storm and its effect on ground resources like Opportunity, for example. Also make sure you have a look at the link in the Damian Peach image above which shows the before and after views of Mars.



Martian Dust Storm is Starting to Die Down
from www.space.com July 27, 2018

The dust is finally beginning to clear on Mars, but it'll probably still be a while before NASA's sidelined Opportunity rover can phone home.
A
global dust storm has enshrouded Mars for more than a month, plunging the planet's surface into perpetual darkness. That's complicated life significantly for the solar-powered Opportunity, which has apparently put itself into a sort of hibernation; the rover hasn't contacted its controllers since June 10.

A long-awaited dawn seems to be on the horizon, however. [
Mars Dust Storm 2018: How It Grew & What It Means for the Opportunity Rover]

"It's the beginning of the end for the planet-encircling dust storm on Mars," NASA officials wrote in an
Opportunity mission update yesterday (July 26).

Scientists studying the storm "say that, as of Monday, July 23, more dust is falling out than is being raised into the planet's thin air," agency officials added. "That means the event has reached its decay phase, when dust-raising occurs in ever smaller areas, while others stop raising dust altogether.”

Other data points support this conclusion. For example, measurements by NASA's Mars Reconnaissance Orbiter show that temperatures in the middle atmosphere have stopped rising, indicating less absorption of solar heat by dust particles.

In addition, NASA's Curiosity rover — which is nuclear-powered and can therefore work through the storm — has observed a decline in overhead dust at its location, the 96-mile-wide (154 kilometers) Gale Crater, agency officials said.

Some Martian landforms previously hidden beneath the dust can now be spotted from orbit again, they added, and may even be visible using Earth-based telescopes by early next week, when Mars will make its
closest approach to our planet since 2003

But don't hold your breath waiting to hear from Opportunity, which has been exploring Mars since 2004. According to yesterday's mission update, "it could still be weeks, or even months, before skies are clear enough" for Opportunity to recharge its batteries and ping its handlers.
The storm is a serious threat to the six-wheeled robot, but mission team members have expressed
cautious optimism that Opportunity will survive. Their calculations suggest that temperatures at Opportunity's location — the rim of the 14-mile-wide (22 km) Endeavour Crater — won't get cold enough to freeze the rover to death.

That fate befell Opportunity's twin, Spirit, after it got bogged down in sand in 2010 and couldn't reorient itself to catch the sun.

Originally published on Space.com.


Mars is Back! but playing hide and seek.

by John Hlynialuk

7834_hubble-mars-opposition-2016-full2_95K

Image above is a Hubble Space Telescope image and shows much more than you can see with a telescope.


Mars in 2018 -closest since record close approach of 2003

The close approach of Mars to Earth in 2003 is being repeated this year. The orbit of Mars is an ellipse and only every 15 to 17 years or so do the distances line up so that we get a better than average separation from the Red Planet . From 2018 onwards, oppositions of Mars gradually get farther and farther (until Sep 2035) so this year is the time to get out and pay some serious attention to the planet.

One or two viewing occasions are not going to do it, however. The planet is not as high in the sky as it has been at other oppositions so our atmosphere will play a significant role in your not seeing Mars at its best. You need to be persistent and get out often as you pursue Mars. You need a combination of dark, clear skies, good seeing and maximum altitude above the horizon to be rewarded with better than average views.

The map/diagram below from Sky&Telescope shows the main features of the planet. But there are other sources of detailed information as well.

Mars viewing guides can be found here:
SkyNews Mars Guide and here from Cosmic Pursuits: Cosmic Pursuits Mars Guide as well as here: Sky&Telescope Mars viewing There is also a Mars app that shows which face of Mars is visible at your observing time. Called Mars Profiler the link is here: S&T Mars Profiler

MARTIAN DUST STORM
On the down side a big dust storm started up in mid-May and continues to shroud the entire planet. Features of the surface have been pretty much obliterated and will remain so until the dust settles. Details of the storm’s development can be found here:
Martian Dust Storm and here: Dust Storm Update but a quick synopsis follows.

The storm started in the opposite (northern) hemisphere from where they normally occur and then expanded into southern regions so by June 19, the entire planet was shrouded. NASA’s Rover Opportunity which went into a hunkered-down mode has not been heard from since June 10.


Amateur observers have been chewing their nails waiting for a break in the storm but the only things noticeable are an overall fifth of a magnitude increase in brightness and a subtle change in the colour of the planet from its usual reddish-orange (or pink) to a pumpkin orange hue. Few telescopic observers have noticed even a polar cap glowing feebly through the haze.

Scott Guzewich, atmospheric scientist at NASA’s Goddard Space Flight Center, struck a note of optimism, writing in a July 5th blog that "the amount of dust over Gale Crater has been slowly declining over the last two weeks, and it’s possible the dust storm has reached its ‘peak”’. Once storms like this peak, it still takes several months for the atmosphere to clear to pre-storm transparency. This puts us into late August/September before things settle down. By that time, Mars will be well past its July 27 opposition. All is not lost however, since in late August, Mars crosses the meridian (its highest point above the southern horizon) around 11 pm and in late September that occurs around 9:30 pm. So if anything, Mars viewing will still be going on into the fall. The down side is that it shrinks from its 24 arc-second diameter on July 27 to 16 arc-seconds in late September.

The chart below shows Mars features as they will (eventually) be visible. Sky&Telescope has a great app called
Mars Profiler that will keep track of the visible face for you. Click on the link provided. And keep your fingers, toes etc, crossed for a quick clearing of the dust!



CC_Mar14_Marsglobes