Friday, August 30, 2019

Incoming comet



A couple of weeks ago, I took a picture through the remote Slooh.com telescope of a comet coming in from the outer reaches of the solar system, an area called the Oort cloud. This is a theoretical cloud, thought to extend from about 2,000 AU (Astronomical unit - the distance Earth to Sun - about 150,000,000 km) to 200,000 AU. It supposedly contains icy planetesimals (Wikipedia contains some detailed information).

Because its outer reaches are so far from the Sun, the planetesimals can be affected by the gravitational influences of other objects in our galaxy, and occasionally my be deflected towards our Sun. There is a reasonable chance that this comet is one such object. Here's the picture:


The name of the comet is Comet C 2018 W2 Africano. It's the fuzzy spot to the right of the dashed line. At the time of writing, the comet is moving at 50 km/sec towards the Sun and will be at Perihelion (closest to the Sun) on Sep.5 and closest to Earth on Sep 27. It may become visible in common telescopes and possibly even binoculars. Africano is currently in the constellation Camelopardalis. Look for more current positions in TheSkylive.com as time progresses


Africano will be closest to Earth on Sept 27 at around 75 million km from Earth.


Thursday, June 20, 2019

King of the sky



Right now, the planet Jupiter is visible in the sky fairly low in the south in the evening. That's a comfortable and convenient time to observe it.

Jupiter is the most massive, and the largest planet in the solar system. All the other planets would easily fit into it's volume, with room to spare for a second set of solar system planets. We have not detected a solid surface on Jupiter yet; it is one of the two gas giant planets orbiting the sun (which one is the other?). It has the mass of over 300 Earths and around 1200 times the volume. with a diameter about 11 times that of Earth. It is a gas ball with a diameter of 143,000 km and consists of Hydrogen (about 90% and 9+% Helium, with traces of Methane and other elements). That's somewhat reminiscent of the Sun's composition; some people are calling Jupiter a "failed star".  However, in order to start the necessary nuclear fusion, Jupiter would have to have about ten times more mass. None-the-less, internal pressures are huge, enough to transmute Hydrogen and Helium into a liquid metallic state. At the centre, there may be an ice/rock core.

At opposition (i.e. now, August/September 2019) it is close to Earth, since Sun, Earth, and Jupiter are positioned almost in a straight line. That means that Jupiter is somewhat more than 4 Astronomical Units away from us (1 AU = 150 million km). Therefore, the light coming to us from Jupiter takes around 35 minutes to get here. Add to that the distance of Jupiter to the sun, and you get about 45 more minutes. Since all solar planets shine by reflected sunlight, we see Jupiter illuminated by sunlight which left the sun around 80 minutes (1 hour and 20 minutes) earlier.

Even though Jupiter is 5 times as far from the sun as Earth, and receives only 1/25th (square of distance law) of Earth's sunlight,  it is, after the Sun, the Moon, Venus, and the space station in orbit around Earth, the brightest object in the sky. That is due to its large diameter and relatively high reflectivity (albedo). It appears large enough from Earth to show some details in even a small telescope, as well as the Galilean moons. Even binoculars will show the dance of the moons around Jupiter. Larger telescopes, i.e. 4", 5", 8" and larger will show many always changing details on Jupiter, including the great red spot, a local storm as large as our Earth, undergoing quite drastic changes at this time. Jupiter turns once in just under 10 hours; constantly showing new features on its surface. The prominent cloud bands (mostly methane, some ammonia, water ice, traces of hydrogen sulfide) move at hundreds of kilometers/hr., they are far more energetic than the worst storms on Earth.

The Galilean moons orbiting Jupiter show relatively fast changes in relative positions. These are easily followed even in binoculars. The moons themselves are very different from each other. In order of increasing distance from Jupiter they are Io, Europa, Ganymede, and Callisto. Io is the most volcanically active of any planets or moons in the solar system, Europa has a very smooth, icy surface, possibly about 50km thick, with a vast layer of liquid water suspected underneath; Ganymede is the largest moon in our solar system, and has a quite complex composition; Callisto is the third largest of the moons around any of the solar system planets, after Ganymede, and Saturn's moon Titan. It has a heavily cratered surface. Only the largest of Jupiter's moons' features are visible through earth-based telescopes, and a large telescope is needed even for that purpose.

Look up The RASC's Observer's Handbook; Wikipedia and other astronomical on-line sources to contain more details for Jupiter-related phenomena.

People have spent a lifetime exploring Jupiter's system, and now the latest orbiting probes have sent back very detailed data.

Jupiter is truly the King of the Solar System planets.








Wednesday, April 10, 2019

An easy target

While our winter nights in our area are cloudy for the most part, aside from the famous objects observable (the Orion nebula, say) we have some other beautiful, easily accessible star clusters available to be observed when the sky clears. One of these, an open cluster M35, in Gemini, can be seen through binoculars, and is almost overhead during that time of year, and can be found lower in the sky well into the spring, too. There is another star cluster located close to M 35, New General Catalogue (NGC) # 2158, much fainter.

M 35 is estimated to be about 2800 light years away, while NGC 2158 is about 5 times farther away. These two clusters are not related, their proximity is just a matter of perspective from our location in our galaxy. NGC 2158 can be observed through telescopes, while 10x50 binoculars resolve the brighter stars in M 35. This cluster is roughly 110 Million years old, pretty young, if we consider the age of the Universe (about 13.7 billion years). M 35 has a diameter of about 23 light years. We're getting closer to it at a speed of about 5 km/sec.



M35 (upper left hand quadrant) and NGC 2158 (lower right). I took this picture through a remote-control Slooh.com telescope


 Below is a map of M 35's location, a screen capture from Starry Night Pro by Simulation Curriculum:


You can also see the location of a few more objects, by no means all, which are easy to find in binoculars, and are really nice in 3 to 6 inch telescopes, at low power.

There are a number of "easy targets" in the sky at this time of year; I picked just one.






Friday, March 29, 2019

Visual aid



Many times, during our public astronomy nights, people have asked about buying a telescope. If this request comes from someone who has just looked through a telescope for the first time, I recommended to start with binoculars. This is the second step after having acquired at least a little familiarity with "naked eye" constellation, location of some of the major "targets", and the their seasonal visibility. I also explain the reason for the timing on the orbital position of the Earth in its orbit around the sun.

Having used telescopes for most of my life, I always use binoculars as helpers to locate objects I want to look at. I am talking here about finding them "manually", not using computerized telescopes. In many cases, people already own some binoculars, they've just never thought of using them to look at the sky. Most of these "found" binoculars are quite suitable for this kind of use.

For astronomical purposes, binoculars with larger front lenses are better. Astronomical objects, other than the Moon and the bright planets, tend to be quite faint; the larger the front lens, the more light you gather, that makes these faint targets easier to see. Personally, I use two pairs of binoculars with the magnifying power (power equals magnification) of 10 and one stabilized pair with the power of 15 (see fig. 1, left to right).

The OLYMPUS binoculars on the left, above, have 10 power and a front lens diameter of 42 mm (fig. 2), the Bushnell and stabilized Canon (fig. 3 and 4) have 50 mm diameter front lenses. Power and front lens diameter (in millimetres [mm]) are displayed somewhere on each pair of binoculars in the form of POWER x DIAMETER, i.e. 15x50 for the Canon binoculars. In addition, the field of view in degrees is also shown.


fig. 1

fig. 2

fig. 3

fig. 4


Generally, the larger binoculars become, the heavier they are. In this group of binoculars, above, the OLYMPUS pair is the lightest, while the Canon pair is the heaviest - it contains the stabilizing electronics, as well as a battery, in addition the internal prisms which make the image appear upright. All commonly available binoculars shown are, in a basic sense, refractor type telescopes, which will normally show an upside down image. Additional optical components are needed to turn the image around once more; that delivers an "upside down upside down" image. Galileo would have given his eye-teeth to have a telescope of the quality in today's refractors and their derivatives, i.e. binoculars.

I should also mention the effect of what is called the "exit pupil" of any optical telescope, including binoculars. The exit pupil can be seen by looking at the eyepiece (the lenses where you place your eye(s) to look through a telescope). Exit pupil diameter, usually stated in mm, should match the diameter of your eyes' pupils when you use binoculars. Exit pupils are the front lenses projected by the eyepieces, and therefore contain all the light entering the front lenses (see fig. 5). If your own eye pupils, which vary their diameter depending on the brightness at which you are looking is high, your pupils contract (become smaller). If your eye pupil is smaller than the exit pupils of your binoculars, you automatically discard some of the light which is contained in the binocular's exit pupils. This is no problem when you use your binoculars during the day, but for Astronomy, you usually look at very faint objects and you want to get all the light that you can catch in the objective lenses.

There is a simple way to calculate the diameter of telescope or binocular exit pupil diameter:

DIAMETER divided by POWER i.e.    50 divided by 10 = 5mm
      42 divided by 10 = 4.2mm
      50 divided by 15 = 3.3mm

fig. 5


When you are young, your eye pupils can expand to about 7mm in deep darkness. That's why 7 x 50 binoculars are used in the navy. Most sailors tend to be young, and can make use of all the light coming into the binoculars at night. As you get older, the maximum "dark adapted" pupil diameter tends to get smaller. For instance, at age 50 you may only have a 5mm "dark adapted" pupil diameter. I'm way past that age, so my pupil diameter may possibly expand to less than that. Again, if your pupils match the diameter of exit pupil, you see all the light that your telescope or binoculars can catch. Any pair of binoculars worth their salt will also show you the larger craters on the Moon, the Galilean moons of Jupiter, brighter open and globular star clusters, movements of the planets and other interesting astronomical wonders. Much of this information is found in the RASC's Observers Handbook (free if you are a member).

As a couple of examples, there are detailed descriptions of the technical aspects of binoculars by Dr. Roy Bishop contained in the RASC's Observers Handbook, starting on page 60 in the 2019 edition. Wikipedia also contains information about binoculars.

Think of how much more light the objective lenses of telescopes and binoculars can intercept than your own pupils (50mm versus 5mm, say). It is the ratio of the disk area of a 50mm objective lens and 5 mm exit pupil you need to consider.

You can see what a great visual aid binoculars can be when using them to look at the sky at night.


Thursday, January 24, 2019

Serendipitous Eclipse

It happens very seldom that the weather gives us a break exactly when we astronomical observers want one. Usually it's the reverse: the weather is reasonable just before an interesting event. Then,  just a few hours before event time the weather clouds up, or rain starts, or snow, or any other condition which prevents us from observing is going to occur.

This time, we got a lucky break. The weather cleared up just a few hours before the recent total lunar eclipse. Our granddaughters, who are also members of the RASC (as I am), took some nice pictures of the eclipse (I set up a telescope on the rear porch at home and just observed by eye, binoculars, and the telescope). I downloaded only one image from Slooh. com the remotely-accessed organization.

Here is my only image, taken with a remote-control telescope at Slooh.com:



I'm always fascinated by the media's statements when they are hyping a completely normal astronomical event which repeats itself often with descriptions like "Blue Moon, Harvest Moon, Wolf Moon, Super Moon", and other mystical names.

We will have no more total lunar eclipses this year. A partial lunar eclipse this year will occur on July 16. The next total lunar eclipse will occur on May 26, 2021. On November 19, 1921 will be a partial lunar eclipse. Another total lunar eclipse occurs on May 16, 2022. In between occur several penumbral lunar eclipses, on Jan 10, 2020, June 05, 2020, July 05, 2020, Nov 30, 2020 all usually almost invisible, because the brightness of the full moon varies very little. Penumbral lunar eclipses are caused by the Moon just missing the Earth's shadow.

The Moon's orbital plane differs from the Earth's orbital plane around the Sun by about 5 degrees. There are two crossover points, the ascending and descending nodes. Both solar and lunar eclipses (partial and total) can occur only when these nodes are "in line" with the Sun, and the Moon is very near, or at one of them. That also means the both types of eclipses occur at either "new Moon" (solar) or "full" Moon (lunar). These nodes slowly move around the plane of the Earth's orbit, giving rise to various series of "eclipse cycles" which repeat over hundreds of years.

You can let your imagination play by thinking about what these various types of eclipses would look like if you found yourself on the Moon...

The total lunar eclipse on January 20 was indeed serendipitous.


Tuesday, November 6, 2018

Space does not look like that


J. Karl Miller wrote: please note,

Our son Derek K. Miller, along with a degree in marine biology, a diploma in non-fiction writing, had an eclectic mind, and interests in many things ranging from writing for several magazines, the Vancouver Sun, and other publications, and editing books. He also had extensive knowledge of and involvement with science, music, photography, computer technology, web page programming and administration, astronomy, and several other fields. He was among the first to make use of on-line communications, well before the internet existed in its current form.

This post is a copy of what Derek wrote in his blog about two and a half months before he died of metastatic colorectal cancer at age 41.

By Derek on February 17, 2011 6:40 PM 

Remember the end of The Empire Strikes Back, where Leia and Luke, convalescing from surgery to replace his severed hand, gaze out of the window of a Rebel spaceship at the departing Millennium Falcon, with the Galaxy (the far, far away one) spinning slowly in the background? It looked something like this:

Hubble image

That's a real galaxy, though, called NGC 2841, about 45 million light years away from our own. And neither it nor its Star Wars companion would look anything like that if we were seeing them with our own eyes.

First of all, forget the spinning: it takes our solar system about 225 million years to make one rotation around the core of the Milky Way, so even if you were able to see the whole disk, it would take many human lifetimes to perceive any motion at all. Put another way, the last time we were at this spot in our rotation, Earth was in the middle of the Triassic period, the time of the earliest dinosaurs.

Maybe more importantly, I don't think we could see a galaxy in all its beauty that way at all, because it would probably be too dim for our eyes. Consider that all photos of other galaxies require pretty long exposures, even for sensitive equipment. The Andromeda Galaxy, which you can see in a dark sky with your naked eye as a faint smudge, doesn't show its full shape in a telescope until you collect light for at least a few minutes.

Consider the fact that we're right inside a galaxy, and for most of us living in cities, the Milky Way, which is the view through the thickness of our closest spiral arm, is entirely washed out by light pollution. I don't think my daughters have ever seen it, in fact. You need a pretty dark sky, preferably on a moonless night, to see it properly.


If you were far enough away from a galaxy to see the whole thing, it would be even dimmer, so no matter how dark the sky, to your naked eye it would be much more a large, galaxy-shaped smudge of light (an impressive smudge indeed, but still smudgy) than the crisp, defined, and detailed colourful disks we see in photos. You might be able to determine its shape, and see the core, but it wouldn't be what Luke, Leia, R2-D2, and C-3PO were gazing at.

People are sometimes disappointed when they look through a telescope at celestial objects. Jupiter, Saturn, the Moon, and the Sun are certainly impressive, but nebulae lack the fantastic colours and flaming tendrils we've come to expect after decades of Hubble Space Telescope images. But those pictures are long exposures, often with artificial colours displaying wavelengths humans can't even see.


While those images are real, they're not what our eyes see when we look at the light directly.

Still, think about how amazing it is to do anyway: away from city lights, on a dark clear night, preferably at high altitude, you can peer up near the constellations Pegasus and Cassiopeia to find the Andromeda Galaxy, no binoculars or telescope necessary (though they'll make it yet a better experience). When you see it, you know that the light hitting your eyes started its journey two million years ago, before modern humans evolved. 


Wednesday, October 3, 2018

Getting to know the sky


At our public star parties a number of people have never seen the impressive objects we usually show through a telescope ask about how, and at what cost they could acquire a telescope to look at the stars, planets, the Moon, and other objects in the sky.

My long-time come-back to this question for people who are new to looking at the sky through one of our members' or SFU's Trottier observatory's telescopes are questions of my own. I ask whether they own a pair of binoculars. If the answer is yes, then the my next question is: have you ever looked at stars through them? Many people have never even thought of doing this. To those people who have done it, I put this question: would you know where to look for the Andromeda galaxy (or some other object in the sky)? The answer many times is "no".

With the apps available on computers, tablets, smartphones, etc., many people compare the sky portrayed on these devices with the sky visible at the time. That's a legitimate approach, but, in my opinion, if one comes to rely on these devices, one usually does not "learn" the sky.

I grew up at a time when these devices were "science fiction". Having had an interest in astronomy since I was eight years old, knowing the sky is an "innate" feeling for me, at least as far as the northern hemisphere is concerned. I've not much time closer to the equator, therefore I don't have the same familiarity with the southern sky.

In my younger years I did some serious astronomy, for instance submitting observations to the AAVSO (American Association of Variable Star Observers) regarding variable stars, Zürich sunspot numbers, occultation timing, and other things. These activities, and many others are now done by both amateur and professional astronomers (the two categories really overlap nowadays, since the technologies available are now highly sophisticated and not very expensive), and generate very precise and detailed results.

At this time in my life, my greatest enjoyment comes from our public star parties. I get a kick out of comments like "wow", "cool", "amazing" when people are looking through one of my telescopes at the sky. In particular, I feel very happy when a young person comes up with these comments.

Adults who are "newly exposed" are equally amazed. The objects which usually are the source of this are the "jewels" of the sky: Venus and its phases, Jupiter and its moons, Saturn's rings, our Moon's craters, open and globular star clusters, etc.

Here are the recommendations I usually make:

(1) When outdoors, preferably under a dark sky, use only your eyes to get to know the sky and constellations using one of the star finders we hand out freely on various occasions, or find a printed or on-line star atlas. Familiarize yourself with the constellations and their annual positions at various times of the year. Dig deeper, and become knowledgeable about the Earth's orbit and how that relates to these times of visibility. Try to find objects which our unaided eyes can readily perceive (Pleiades, Hyades, Milky Way, compact constellations, etc.). If you feel that you'd like to see these targets in more detail, then

(2) use your binoculars to find these objects. If you are a young person, 7x50 binoculars are ideal. Your age and personal preferences have an effect on what may be your perfect binoculars. Almost all binoculars will show far more detail in the night sky than the "naked" human eye. Using binoculars will "train" you to find sky objects. At first you may spend some time to succeed, but you quite quickly become better at it.

Many very descriptive dissertations have been written about the use of binoculars in astronomy. Even advanced astronomers, at least those who are involved in the visual observing, have their favorite binoculars on hand when observing. Personally, when I'm setting up one of my telescopes, I always have binoculars with me. They are very helpful in locating objects for which I want to use the telescope. Once you have become familiar with their use and characteristics, and if you are looking for even more detail, a telescope may be your next "step up".

(3) Before you buy a telescope, understand the basic requirements. Beside the size of your contemplated purchase, understand differences between the various types. This is a much-discussed and written-about subject. The best way to find out is to attend star parties, such as the ones run by the RASC, or SFU's Trottier Observatory, because you will usually meet people who are using different types of telescopes. You will also become aware of the fact that purchasing a telescope entails having to buy a sturdy, and accurately manufactured telescope mount. The best telescope is next to useless unless it can be held steady, and does not shake with every little breeze. The matching of telescope to its support is another important topic.

Computerized telescopes are a helpful addition to the range of telescopes available. Again, unless you have learned how to find objects in the sky as described in (1), (2), and (3), you likely won't get to know the sky in the detail necessary. Getting to know the sky "in depth" is best done by learning to point a telescope "manually".

If you become a member of the RASC, you'll have access to many benefits. As a member, you can borrow one of the RASC's library books, and/or a loaner telescope for a limited time. You also receive several publications, chief of which is the RASC's annually published Observers' Handbook. It contains a wealth of data, among which you'll find detailed information about binoculars, telescopes, human eyes, and upcoming monthly events (eclipses, occultations, planetary positions - a plethora of facts and discoveries). The Handbook is used by professional and amateur astronomers world-wide. The RASC also owns the magazine "Skynews", and publishes the RASC Bulletin and local RASC centre newsletters. All these are included in the membership.

Try it - I think you'll like it.


Monday, August 13, 2018

Deja vu (Perseids wiped out again)

As is a tradition by now, our local centre of the Royal Astronomical Society of Canada helps out at
Aldergrove Lake Park for viewing the Perseids every year. It is a big event for the Parks Board and the public, and matches the Royal Astronomical Society of Canada's mandate to promote an interest in astronomy and associated sciences to the public.

I wrote this last year in my post about viewing the Perseid meteor shower (August 13, 2017, in italics):

Aldergrove Park near Abbotsford is used for public viewing when the Perseid meteor shower peaks annually on August 12. The park administration sets up a tent for us (the RASC), and reserves some space nearby to set up telescopes. Some of our members, and sometimes invited speakers, give several talks regarding astronomical events (past, present, and future). It's a rain-or-shine occasion. If it rains, telescopes are not set up outside, but may serve as exhibits inside the tent.

The Aldergrove Park administration promotes this event. This is the only time in the year at which overnight camping is allowed in the park. Many people usually attend.

This year, an unfortunate fire on a barge carrying old, recycled cars, docked in the Fraser river on the day before this event created a lot of smoke. This affected much of the Lower Mainland, both on the day before, when we were involved with the "Starry Night" event at Simon Fraser University's Trottier Observatory, and at Aldergrove Park. "Perseid" day itself was cloudy, with local rain showers. Toward evening, the smoke had cleared, and some large, blue stretches appeared in the southwestern sky and drifted east to where Jupiter, Saturn, and Mars would be located at dusk. I made my way to Aldergrove Park, found our assigned area (same as last year), decided that chances were reasonable for viewing, and set up my telescope.

Our RASC Vancouver centre librarian William happened to spot Venus with his binoculars well before sunset, so he and I trained our telescopes on that brightest of our planetary siblings. I got a couple of minutes view of it, a couple of members and the public had a chance to view it as well, and then a cloud covered Venus. That was the last view I had of it for the evening.

Well, as the weather gods would have it, it turned more cloudy just as the evening approached and eventually some rain began to fall. I packed up my telescope. There was another break in the clouds about 45 minutes later and a number of people had a chance to see both Jupiter and Saturn through a couple of our other members' telescopes. Clouds then turned really heavy, and it started raining seriously towards 11pm.

After the a number of days of wildfire smoke, which covered our area during all the preceding, sunny days, and which was finally cleared out by wind from the south-west, this was a disappointment.  We are told by the park administration that fewer people than last year showed up. During the short periods when the view was worthwhile, several dozen of them came to visit our telescopes. Attendance at the talks in the tent was fortunately much higher.

Our activities ended just before midnight; had it been clear, we would have stayed all night for the public to have a look at interesting astronomical objects - the Perseid meteors especially, of course. Well, we hope that next year's Perseid meteor date will have a clear night sky. This is the same sentiment I expressed last year.

As I write this, the smoky sky has returned. The cause appears to be some fairly large forest fires on Vancouver Island. So the night from August 12 to 13 (which was when the actual maximum of Perseids was expected) turned out to be a bummer, too.

Maybe "deja vu" of smoky skies is turning out to be the new normal.

Monday, July 23, 2018

Smartphone Moon

On July 21, I set up my trusty 3" refractor (f16), which I bought 54 years ago, and used a Meade 20mm eyepiece (which I've had for close to 40 years) to look at the Moon, Jupiter, etc. I invited my neighbour, Trevor, to have a look. It seems that he had never seen the Moon close up. He was very impressed and wondered if a smartphone could be used to take a picture.

I told him that it would be possible, but challenging to manually align the smartphone camera lens with the eyepiece.  Well, he tried anyway, I helped him to line up the lens. During the short moments that a good image appeared on the smartphone screen, a couple of pictures were taken. Here's an image of "Trevor's Moon", taken with his Samsung smartphone. Quite acceptable, although the dynamic range seems a bit narrow. I have added "enhanced" pictures (modified from the original) to show more cratered area detail. The highly overexposed bright areas did not contain enough detail to recover.



"Trevor's Moon" (original image, downloaded from his smartphone)




Cropped from the original image.



Image enhanced to show more details in cratered area.





Southern, cratered section of the Moon enlarged.




Enhanced to show more detail.




The prominent craters Tycho and Clavius show up well, including the craters inside Clavius. I was surprised that this makeshift arrangement had such a good result. Amazing what one can do with today's smartphones and graphics programs.

I'm thinking of buying one of the available smartphone camera attachments (I have an iPhone 6s) and, on our public nights, have people activate the camera button. That way, they could  photograph the craters of the Moon themselves (I'd email the image to them). It might be popular for SFU's Starry Nights, and our "side walk" RASC events.



Friday, July 20, 2018

The Moon and Venus and other goodies

Monday, June 25, 2018

Hoo, hoo, hoo...




The Owl Nebula (M97) - unprocessed original image
(remotely photographed through a Slooh.com telescope)


The Owl Nebula (M97) in Ursa Major
cropped from original and processed with Apple Preview

I've been away for the better part of the last two months, and, being back home, decided to pursue my astronomical activities by using one of Slooh.com's remotely-controlled telescopes.

About 2030 light years distant, in the constellation Ursa Major, you can find the Owl Nebula (M97). In 1781, the French astronomer Pierre Méchain discovered this planetary nebula. At a time when there no photographic technology, some observers drew the nebula image resembling an owl's head. That appears to be the source of the name. Here is a description found in Wikipedia:

The nebula is approximately 8,000 years old. It is approximately circular in cross-section with a little visible internal structure. It was formed from the outflow of material from the stellar wind of the central star as it evolved along the asymptotic giant branch. The nebula is arranged in three concentric shells, with the outermost shell being about 20–30% larger than the inner shell. The owl-like appearance of the nebula is the result of an inner shell that is not circularly symmetric, but instead forms a barrel-like structure aligned at an angle of 45° to the line of sight.
The nebula holds about 0.13 solar masses of matter, including hydrogen, helium, nitrogen, oxygen, and sulfur; all with a density of less than 100 particles per cubic centimeter. Its outer radius is around 0.91 ly (0.28 pc) and it is expanding with velocities in the range of 27–39 km/s into the surrounding interstellar medium.

The 14th magnitude central star has since reached the turning point of its evolution where it condenses to form a white dwarf. It has 55–60% of the Sun's mass, 41–148 times the brightness of the Sun, and an effective temperature of 123,000 K. The star has been successfully resolved by the Spitzer Space Telescope as a point source that does not show the infrared excess characteristic of a circumstellar disk.

In terms of the age of the universe, this nebula is like a newborn owl. 

hoo, hoo, hoo...









Monday, April 16, 2018

Southern Belle


 Rain, rain, rain... my astronomical activities are certainly taking a bath right now. Fortunately, in this age of the internet, I can hook up with some remote-control telescopes, located in areas which are much more likely to have clear skies. One such telescope is located in Chile and is made available to members of Slooh.com, an organization oriented to the world-wide astronomical community.

Some of the most impressive astronomical objects are located in the southern sky, visible at night only from areas close to, and south of the Earth's equator. One of those objects is Eta Carina.

Here is a quote from Wikipedia, the free encyclopedia:

The Carina Nebula (catalogued as NGC 3372; also known as the Grand Nebula, Great Nebula in Carina, or Eta Carinae Nebula) is a large, complex area of bright and dark nebulosity in the constellation Carina, and is located in the Carina–Sagittarius Arm of our galaxy (Milky Way). It has an estimated distance between 6,500 and 10,000 light-years (2,000 and 3,100 parsec) from Earth.

The nebula is contains many other objects, from the intrinsically brightest star in our galaxy to several star clusters, gaseous star-forming regions, and other interesting sights.  It is one of the largest diffuse nebulae in our skies. Although it is some four times as large and even brighter than the famous Orion Nebula, the Carina Nebula is much less well known due to its location in the southern sky. It was discovered by Nicolas-Louis de Lacaille in 1752 from the Cape of Good Hope.



a wide-field view of (η) Eta Carina

Here's a larger image of Eta Carina Nebula's core.


At this time, we have no plans to travel south; from a narrow point of view, to take a photo of this nebula/star assembly remotely saves the money. None-the-less, it would be nice to see this southern belle directly, it is a beauty even in binoculars, though you won't see the colours seen in the two images.

Saturday, April 7, 2018

Astronomical gems



Something which is unfortunately not seen from our latitude is one of the oldest and likely the largest concentrated accumulation of stars in our galaxy. It is a globular cluster, of which there are about 200 or so associated with "us". These clusters are very old, they have been around for about 10 to 12 billion years. Our own universe is calculated to be about 13.7 billion years old, so they have existed for most of that time.

This particular one is best seen from the night sky close to, and at latitudes below Earth's equator. It can be seen by the naked eye as a fuzzy star in the constellation Centaurus, and is accordingly named like a star: "Omega Centauri" (a mix of a Greek letter and Latin constellation name). It turns into an amazing view when seen through a pair of reasonably large binoculars or wide-field telescopes. As a photographic object, it truly "shines", much like a box of diamonds.

Since it is unobservable from our area, and since the current weather prevents any outdoor observing of the sky, I decided to resort to "old trusty", and acquired an image of Omega Centauri via a remote-controlled Slooh.com telescope, located in Chile. This is a favorite object for many astrophotographers and has been recorded thousands of times. Robert Conrad, the Observing Director in our Vancouver centre of the RASC posted his excellent photo in NOVA (March/April edition), our bimonthly news letter.

Here is my wide-field image of Omega, cropped to centre it in the frame:


Omega Centauri

This globular cluster contains about four million stars. That is about 10 times the number contained in M13, the most impressive globular in our sky (but not visible with my unaided eye, at least). Some estimates say that the average distance between the stars in Omega Centauri is less than one light year. Can you image the blazing night sky you would see on a planet that orbits one of those stars?

The orbits of planets around any of these stars would likely be perturbed by the other close near-by stars to make them unstable, with local climate subject to large swings from hot to cold. That would make an evolution of life as we know it unlikely. Well, it's nice to speculate.