Discovery Space: What's Up?

Top 10 Sky Events for 2009

Alan Dyer — Mon, 29 Dec 2008 22:44:16 -0500

Here’s my take on the best predictable celestial events for 2009, the International Year of Astronomy, when we celebrate the 400th anniversary of Galileo’s use of the telescope to explore the sky. Among the highlights of 2009: Saturn without prominent rings; a binocular comet (or two); the Moon covering up Venus; possibly a good display of Leonid meteors; and the longest total eclipse of the Sun in the 21st century.

January (all month)
Saturn’s Rings at Minimum Tilt — As I explained on my blog for December 19, Saturn’s rings are now tipped at their minimum angle, nearly edge on, this month. You won’t see them this razor thin for another 30 years. So this is a great time to “not” see the rings of Saturn. While Saturn can be seen with unaided eyes, you’ll need a telescope to view the rings, such as they are — my earlier blog provides a chart for finding the planet.

February 23-24
Comet Lulin at its Best — Astronomers expect that a comet found in 2007 at the Lulin Observatory in China may be easily visible in late February. Comet Lulin isn’t expected to be a bright naked eye comet but should be decent in binoculars. On February 23 it passes just below Saturn (the two will be in the same binocular field) while the next night is when the comet is closest to Earth and at its brightest. In March and April, Comet Cardinal may also become bright enough to see in binoculars.

February 27
Moon Near Venus — Here’s a sight that is sure to please — the crescent Moon sitting close to the brightest planet in the sky. This is probably the best Moon-planet conjunction of the year. On Friday, February 27 the waxing Moon sits just three Moon diameters from Venus for a beautiful pairing in the evening sky. Enjoy it with unaided eyes, binoculars or a telescope at low power.

March 27
Venus at Inferior Conjunction — At the end of March Venus passes from the evening sky into the morning sky, ending several months as an “evening star” and beginning several months as a “morning star.” In doing so, it passes between us and the Sun, coming as close to Earth as any planet can. This “inferior conjunction” happens every 580 days or so, but this year it takes place as Venus passes about 8 degrees above the Sun (the diagram shows the scene at midday). A cautiously-aimed telescope will be able to pick out Venus in the daytime as an ultra-thin crescent sitting just above the Sun, a rare and memorable telescopic sight.

April 22
Occultation of Venus — A month later the waning crescent Moon passes in front of Venus, now well placed in the morning sky well away from the Sun. This sort of “occultation” of a planet by the Moon is rare. Eastern North America misses it, but from most of central and western North America the Moon covers Venus after sunrise in the morning sky. But, as shown here, from California, Arizona, and Mexico, the disappearance of Venus behind the edge of the Moon occurs before sunrise in a darkened sky. That will be a spectacular sight. From the tip of Baja California and from Mazatlan, Venus just grazes along the southern edge of the Moon, an even more amazing sight.

April 26
The Moon and Mercury — Here’s an event most people would miss, but for avid stargazers, spring always brings the best time for sighting Mercury in the evening sky. On April 26, just as Mercury reaches its greatest angle away from the Sun and its peak in visibility, the waxing crescent Moon joins the scene. On April 26 look for the thin Moon just above Mercury, as the two worlds flank the Pleiades star cluster. The grouping should be visible to unaided eyes but use binoculars for the best view.

June 19
Moon with Venus and Mars — Here’s another nice conjunction, with the Moon and Venus involved, as they were back in February, but now with Mars also joining in. Look east in the pre-dawn sky for a trio of the waning crescent Moon just above the close pairing of bright Venus and dimmer Mars. Not far away (but just out of sight in this diagram) below and to the left, sits Mercury, then visible as a morning star. You’ll need to get up early to see this neat gathering of worlds, but the view should be worth it.

July 22
Total Eclipse of the Sun — You’ll have to travel halfway around the world to see this event, but the view will definitely be worth it! Nothing, but nothing, compares to the sight of the Moon covering the Sun during a total eclipse. It does so this year on July 22, but only along a narrow path across Asia and the South Pacific. This eclipse holds the distinction of having the longest duration of totality of any total eclipse of the 21st century, with eclipse chasers able to bask in as much as a whopping 6 minutes and 39 seconds of totality.

October 8 - 16
Mercury-Venus-Saturn Gathering — Attention turns again to the pre-dawn sky, where in October, Mercury, Venus and Saturn appear close together, dancing in the dawn sky. Saturn passes very close to Mercury on October 8 and then passes Venus on October 13. By October 16 (shown here) the waning crescent Moon sits just to the south of the trio of morning planets.

November 17
Leonid Meteors — Word is getting around that we might see an unusual outburst of the annual Leonid meteor shower this year. Normally a pretty mild and sparse shower, the Leonids are known for spectacular outbursts every 33 years or so. Back in 1998 to 2001 the world was treated to several superb Leonid displays as Earth passed through denser parts of the dust streams left by Comet Tempel-Tuttle. These were the first times astronomers had been able to accurately predict such outbursts, and new predictions now suggest another good display on November 17, 2009. However, the timing is such that Asia is favored — in North America only the west may see much meteor activity, and only in the pre-dawn hours.

BONUS:
May, July and December
Jupiter and Neptune — OK, here’s a bonus track! Throughout 2009 Jupiter will be passing back and forth close to Neptune. In late May (dawn sky), mid-July (midnight sky), and again in the third week of December (evening sky, shown here) both planets will be so close to each other they will visible in the same field of a telescope. This is pretty rare. Fittingly, Galileo saw a similar meeting of Jupiter and Neptune, back in 1612. He noted an unusual star that moved near Jupiter but failed to realize it was another planet. Galileo missed discovering Neptune, a planet that remained unknown until 1846.

Now, these are just the predictable events. There’s no telling if and when a comet might be discovered that will become very bright, or that long-awaited supernova will explode in our night sky.

As a final note: I wish I could say: Return to my blog throughout 2009 for more details of these and other sky events. But alas, this is my last “What’s Up” blog for Discovery Channel. However, I should be back now and then with some special news and stories. It’s been fun! Have a great 2009. Happy Year of Astronomy!

Sky charts courtesy TheSkyX™/Software Bisque
Eclipse map courtesy Fred Espenak/NASA Goddard Space Flight Center

Seeing the World at Night

Alan Dyer — Mon, 29 Dec 2008 11:17:12 -0500

I want to point you to a remarkable gallery of images unlike any you might have seen. It’s called The World at Night, and it brings photographers from around the world together in a global celebration of the beauty of the night sky.

The creation of Iranian photographer Babak Tafreshi and American astronomer Mike Simmons, The World At Night features stunning time-exposure stills and time-lapse movies of familiar landscapes but all shot at night, with the stars wheeling overhead.

The philosophy of the site’s authors and contributors is simple: “…the night sky above us – a view that is accessible to everyone on the planet – has no visible borders. This common view is a bridge that connects us, creating understanding and friendship. When borders vanish, political and cultural differences become irrelevant.”

If you love the beauty of the night sky, you owe it to yourself to explore The World at Night, one of the cornerstone projects of the International Year of Astronomy. You will be amazed.

Conjunctions to Ring in the New Year

Alan Dyer — Sun, 28 Dec 2008 16:37:45 -0500

Heading out for an evening of revelry on Wednesday night? Be sure to look up for a celestial show to ring in the New Year, as the western sky presents not one but two conjunctions for your celebratory pleasure.

On December 31 here’s what we have:

1. In the early evening (the chart is for about 5:30 pm), high in the southwest, look for the waxing crescent Moon close to Venus, in a beautiful meeting of the night sky’s two brightest objects. This is an encore of the great conjunction we had on December 1, but without Jupiter.

2. Actually, Jupiter is there, but much lower in the sky, and joined by Mercury. To see this conjunction look early in the evening just after sunset. Low in the twilight you should see another bright star — that’s Jupiter. Now look beside it (binoculars will help) look for dimmer Mercury, partaking in a close 2-planet conjunction with Jupiter.

Jupiter and Mercury are near each other for the couple of days leading up to and then after December 31. But New Year’s Eve is when they appear closest together. Both planets will drop quickly out of the evening sky in early 2009.

The Moon will pass by Venus twice more at monthly intervals before Venus, too, disappears from view in the evening sky. Look for two more Moon-Venus conjunctions, on Thursday, January 29 and Friday, February 27. The last is a good one – be sure to mark it on your calendar. From North America, Venus and the Moon will be just 1.5 degrees apart that night, twice as close as they appear on New Year’s Eve.

Sky chart courtesy TheSkyX™/Software Bisque

Countdown to the International Year of Astronomy

Alan Dyer — Thu, 25 Dec 2008 02:23:48 -0500

What if you could marshal every astronomer on Earth to one cause — providing as many people as possible an opportunity to explore the wonders of the sky? Well, it’s happening. Starting next week. Get ready for the International Year of Astronomy.

Four hundred years ago, in 1609, Galileo first looked through a telescope aimed at the night sky. What he saw changed science — some say it started modern science. It certainly changed the world.

So on its 400th anniversary, it is fitting we have a year to celebrate the telescope. Yes, there have been a lot of “international years of …” lately. Remember 2005? That was the International Year of Physics. No one noticed.

The difference this time is that no other science has such an army of promoters, enthusiasts, PR people, ambassadors — call them what you will. But I call them amateur astronomers. They number in the hundreds of thousands around the world. Add to their legion the many professional astronomers who endorse a culture where science PR is welcomed and encouraged. Space agencies devote a sizable portion of their budgets to public outreach. Every week TV channels like Discovery feature astronomy programs.

What this means is that IYA 09 will be noticed. At the international level. By national media. But most of all, at the local grass roots level. Everywhere you go, astronomy clubs, planetariums, observatories, science centres — all will be staging special events in honor of Galileo and his telescope. Many will be nighttime affairs, with telescopes the main attraction. The goal is to provide everyone with their own “Galileo moment,” their own opportunity to discover the sky.

To learn more about the Year of Astronomy and events that are being staged in 140 countries around the world, check out:

The main IYA website hosted by the European Southern Observatory. Be sure to download the “IYA Trailer.”

And check out “Eyes on the Skies” for a superb series of documentary videos from ESO. And …

… The U.S. IYA website for news of American plans.

… The Canadian IYA website for what’s happening north of the border.

… The Mexican IYA site for what’s happening south of the border.

… And the list goes on… Chances are, organizations in your home town have set up their own websites to keep your community in touch with local Year of Astronomy events.

While so much other news might have us looking down in the new year, the Year of Astronomy will give us all a good reason to look up!

Happy holidays! And clear skies to all.

Solstice Time is Here — 4 Years Until End of World!

Alan Dyer — Sat, 20 Dec 2008 21:05:59 -0500

Sunday, December 21 marks the annual date of solstice, one of the turning points of the year. It is also the date when we are precisely four years away from the end of the world! Yah, right.

Here’s what is really going on. On December 21, at 7:04 a.m. EST, the Sun reaches its most southerly point on an imaginary line called the ecliptic. Well, it’s not really imaginary — you just can’t see it drawn in the sky. But if you could, you would see it as a line passing through 12 constellations (well, 13 really, but that’s another story). It is the path the Sun appears to move along as Earth revolves around the Sun.

Because Earth is tipped over on its axis, the ecliptic line also changes height throughout the year. On summer days the ecliptic is high in the sky; on winter days it passes low across the sky. And so does the Sun.

Now, I have to be careful not to be too hemisphere-centric — because if you live in Australia, December 21 is the summer solstice. But for us in the northern hemisphere December 21 is when the Sun is as low in the sky as we’ll see it for the year — giving us a winter solstice. At midday, as the diagram shows, the Sun sits due south but isn’t very high. The Sun is in the sky for the least amount of time, giving us the “shortest day of the year.” It’s still 24 hours long, like any other day, but it has the least amount of daylight.

After December 21, for us northerners, the Sun begins to travel north along the ecliptic, and climbs a little higher and higher each day at its noonday position. Days get longer.

If you could see the elements of the sky drawn out for you on December 21, you’d see the Sun sitting in the constellation of Sagittarius the archer, at the bottom of the ecliptic (its most southerly point). By coincidence, the Sun has also just crossed the mid-plane of the Milky Way, the galactic equator. This image taken on December 20 by the SOHO satellite shows the Sun (hidden behind the dark disk) sitting amid the starfields of the Milky Way, something only a satellite orbiting in the blackness of space can show us.

Now, the Sun reaches those milestone points every year on the same date (give or take a few hours due to leap years). But the fringe element has taken that solstice configuration of the sky (and the Sun’s crossing of the galactic equator) as one of the signs of the end of the world. Yes, in 2012, all manner of catastrophe will ensue. If Sara Palin becomes president that will certainly be the case, but …!

… You can read a rational explanation of the 2012 “prophecy” at Fraser Cain’s Universe Today. My point here is that on December 21, 2012 the Sun will be in exactly the same configuration as it is on December 21, 2008. In fact, because both are leap years, the match is very close. To say that December 21, 2012 is the first time such a configuration has happened in 26,000 years, or some such hyperbole, is utterly and completely wrong. But the gullible, and Mel Gibson, will lap it up. Snake-oil salesmen will make lots of money selling the idea. Hollywood included.

OK, back to non-ranting reality — In the northern hemisphere, we call December 21 the first day of winter, but in fact it is the date when days actually begin to get longer. As the Sun climbs higher each day, it begins to give us a little more light and energy. Unfortunately, it takes Earth’s atmosphere another couple of months to respond to the Sun’s generosity, so January and February are usually the coldest months of the year for the northern hemisphere, despite the longer days. For those “down under,” it’s just the opposite — days are getting shorter but January and February are hot as blazes. With it going down to -30° C tonight where I am, I wish I was there!

Sky chart courtesy TheSkyX™/Software Bisque
SOHO image courtesy ESA & NASA

Saturn On-Edge for the Holidays

Alan Dyer — Fri, 19 Dec 2008 15:25:33 -0500

Between now and early into the New Year, Saturn’s rings appear as thin as we’ll see them for another 30 years. So get out your telescope and have a look — celebrate the once-a-generation passage of Earth through the plane of Saturn’s rings.

Now to be precise, Saturn’s rings go exactly edge-on in September 2009. That’s when Saturn will experience one of its twice-a-year equinoxes, just like Earth. But on Saturn a year is nearly 30 Earth years long and equinoxes come 15 years apart. At an equinox, just as happens on Earth, Saturn's poles aren’t tipped toward or away from the Sun. Instead, sunlight falls equally on both hemispheres, as it does in spring and autumn on our planet.

The complication with Saturn is that it has rings — rings that lie in the equatorial plane of the planet. So the rings, too, tip toward the Sun (and toward us on Earth), then tip away from us as Saturn revolves around the Sun. For 15 years we see the south face of the rings angled toward us, followed by 15 years of the north face visible, as the collage of Saturn over 30 years shows.

In between those seasons we get a year when Saturn’s rings appear edge-on to us. Because the rings are so thin — no thicker than a city-block by some accounts — they can disappear completely from view.

That isn’t quite happening this time. At least we don’t see it. When the rings go precisely edge-on in September Saturn is too close to the Sun in our sky for us to see it. Instead, it is now — the next few weeks — that Saturn’s rings look their thinnest, tipped at just 0.8 degrees. Through a telescope you’ll still see the rings, but as thin slivers of light jutting out from the sides of the planet, as in the simulated eyepiece view.

Minimum tilt is a week from now, on December 27. The rings then open up again, exceeding a 1 degree tilt in mid-January. Maximum tilt (as wide as we’ll see the rings in the coming year) is 4.1 degrees in mid-May. Then the rings close up again, heading for their edge-on passage in September with Saturn hidden by the Sun.

By the time Saturn comes out from behind the Sun in late 2009 so we can see it again, its rings will have already opened up wider than they are now. So right now — this week — is the best time to “not see!” Saturn’s rings. We won’t see them as thin as this until the ring plane crossings of 2039.

Unfortunately, seeing Saturn means staying up late — Saturn doesn’t rise until about midnight. For the best view wait until 2 or 3 a.m. (the time the sky chart depicts) and look east for a moderately bright star below the pattern of Leo the lion. The Pointer Stars in bowl of the Big Dipper point down to the area. While you can see Saturn with the naked eye, you’ll need a telescope to see its rings, but 100 power is all the magnification you’ll need. And just about any telescope will do. Happy Saturn season!

Ring diagram courtesy Tom Ruen/Wikipedia
Eyepiece view courtesy NASA Solar System Simulator
Sky chart courtesy TheSkyX™/Software Bisque

The Wide Angle: The Dark Energy Doubters

Alan Dyer — Tue, 16 Dec 2008 13:01:00 -0500

This post is part of our in-depth look at how astronomers have caught dark energy in the act of slowing down the universe's development. For much, much more of our series The Wide Angle, click around in the box at the end of this post.

Any news story, like the current Chandra announcement, claiming to present evidence for dark energy — or that other conundrum, dark matter — is guaranteed to provoke response from a community of skeptics. Call them doubters or deniers, they just don’t “believe” all this dark stuff exists. And anyone who does is part of a conservative conspiracy that refuses to see the truth about the universe that only a select few have understood.

I have to say that in attending conventions of amateur astronomers I run into the dark energy deniers all the time. The “alternative cosmology” school is a cottage industry, largely populated by amateur astronomers and armchair cosmologists who get their science from the internet and a host of fringe pop-science books about the Big Bang and why astronomers have it all wrong. Amateur astronomy gatherings are sometimes the only venues maverick authors and scientists have for promoting their radical ideas, and amateurs lap it up.

Now at worse, some of the deniers are outright quacks, among a legion of odd individuals whose avowed purpose in life is to prove Einstein wrong (good luck!), usually by means of hand-written papers filled with geometric diagrams and concocted jargon. They are paranoid that the rest of the world is conspiring to silence their truth.

But quacks aside, there are legitimate, well-respected scientists who propose other explanations for the observations that “prove” the existence of dark energy and dark matter. Most involve an hypothesis that somehow the strength of gravity changes with distance or perhaps with time, in just such a way as to mimic the appearance of the “dark side” of the universe. It is an idea that deserves — and has received — due consideration.

Science should always welcome the wild ideas, ones that counter the accepted paradigm. As physicist Neils Bohr once said, “Your theory is crazy, but it's not crazy enough to be true.”

Truth can be crazy — and heaven knows, dark energy is a crazy idea — but a scientific theory also has to be verifiable. It has to provide a consistent explanation of the observations, no matter how crazy that explanation might sound, and make verifiable predictions. Alternative theories of the universe that do away with dark energy and dark matter have to meet those criteria to be taken seriously.

So far, the reality of dark matter and dark energy is supported by strong evidence, the new Chandra results being the latest. The evidence convinces most astronomers.

More of the Wide Angle

News: Dark Energy Revealed

Top 10: Things You Didn't Know About Dark Energy

Video: Study Sheds Light On Dark Energy

IM Interview: How To Hunt For Dark Energy

My Take: Exciting Times Ahead for Dark Energy Search

Blog: The Dark Energy Doubters

Blog: Far Future Forecast: Deep Darkness

Blog: The Big Yawn

HowStuffWorks: How The Fate Of The Universe Works

However, the “alt-universe” camp will continue to claim that dark energy is an invention akin to tacking on more epicycles onto epicycles, just to save the theory.

But I wonder if the opposite isn’t true. I wonder if the discovery that the “stuff” of which we are made comprises just 4% of the universe isn’t the ultimate Copernican revolution; that denying dark energy is like refusing to accept that Earth isn’t the center of creation. Backyard stargazing makes you begin to understand just how vast the universe is — results like the Chandra observations drive home that it is far bigger and stranger than we could possibly imagine...

As Bohr said, “How wonderful that we have met with a paradox. Now we have some hope of making progress!”

Geminid Meteor Shower This Weekend

Alan Dyer — Fri, 12 Dec 2008 14:57:21 -0500

Saturday night brings the peak of the annual Geminid meteor shower, the best meteor display of the year. That’s the good news. The bad news is that wonderfully bright and extra big Full Moon is going to spoil the meteor show.

On roughly the same dates each year Earth passes through streams of dust left by passing comets. The result is a calendar of annual meteor showers, the most famous being the Perseids of August. But the Geminids of December (around December 13) are equally as good, if not better, at least as far as number of meteors per hour are concerned. But the poor old Geminids tend to get ignored because, for many of us, it's just too darned cold to lie outside gazing up at meteors.

Still, I usually try to make the effort each year, as the Geminids can produce a lot of meteors and they can be bright. But this year, only the less frequent bright ones will show up, like the one I managed to capture during the 2004 Geminids, shooting past Sirius in Canis Major. This year, the Full Moon will wash out the rest — the more numerous fainter meteors won’t show up.

All the meteors will appear to radiate from the constellation of Gemini, exactly where the Moon sits on Saturday night, wouldn't you know. My previous blog provides a star map of that area of sky as it appears in the early evening. So if you have clear skies, and time away from holiday preparations, lie back and look up any time during the night. Saturday night will be best. Despite the Moon, you might be rewarded with the sight of some Geminids shooting across the sky.

Me? I’m bringing in the firewood and hunkering down to endure what is forecast to be a major winter snow storm, followed by plunging temperatures to -30° C. Welcome to winter on the Prairies.

The Big, Bright Full Moon

Alan Dyer — Fri, 12 Dec 2008 03:09:48 -0500

If the Moon seems a little bigger and brighter than usual tonight, it’s no illusion. The Full Moon on Friday is the closest of the year, making it just a little larger and brighter than other Full Moons in 2008.

But how much bigger? About 14 percent. And how much brighter? About 30 percent. Both compared to when the Moon is at the other extreme, when it is farthest away and at its smallest.

Here’s what’s going on: the Moon’s orbit is not a circle (few orbits are) but an ellipse. Once every month the Moon is at its closest point to Earth (perigee) and then two weeks later at its farther point from Earth (apogee). The distance to the Moon at perigee and apogee also varies slightly from month to month — some perigees are closer than others.

Now add in a third variable: the Moon doesn’t necessarily reach perigee when it is Full.

But this month the lunar cycles synchronize to give us a Full Moon just 5 hours before it reaches perigee, and that perigee happens to be the closest perigee of the year. On Friday the Moon is 356,566 kilometres away, a couple of thousand km closer than it was last month at perigee, and some 50,000 km closer than it will be two weeks from now when it is at apogee on the other side of its orbit.

While its proximity makes the Moon appear a little larger — and you might even be fooled into thinking it really looks bigger than usual — in reality the difference in size is pretty hard to detect. It shows up in my photos, comparing a Full Moon at apogee (left) with a Full Moon at perigee (right). Sure, it’s obvious in a side-by-side comparison, but we don’t have two extreme Moons in the sky at once to reveal the difference. Nevertheless, most people will swear the Moon this weekend really does look HUGE!, more because they’ve been told it should look that way.

Ditto on the brightness. The quoted 30 percent jump in brightness is compared to a minimum-sized apogee Full Moon. Compared to most Full Moons the difference is much less. And even 30 percent still amounts to just a third of an f-stop as measured by a camera or light meter. Your eye might have a tough time detecting the difference.

But … any December Full Moon, at least for those of us in the northern hemisphere, is the highest Full Moon of the year, putting it up above haze that can dim the Moon. (The chart shows how the Moon moves from Orion into Gemini from Friday to Saturday night, along the part of its path that takes it as far north as it can get.) So any winter Full Moon is usually a little brighter, as it shines through less atmosphere.

Now add snow to the scene, to reflect the moonlight, and you have a bright night indeed. Last night (Thursday) I grabbed a shot of the Moon, here overexposed, surrounded by a ring of light — a halo — caused by moonlight refracting through ice crystals. A bright Moon helps bring out subtle sky phenomena like that, so look up this weekend. Enjoy the bright big Moon of 2008.

Chart courtesy TheSkyX™/Software Bisque

Take a Trip to Orion

Alan Dyer — Wed, 10 Dec 2008 03:13:00 -0500

For me, raised on the Canadian prairies, this is how Orion should look, rising above a snow-covered landscape, lit by the light of the Moon. It’s the very picture of winter around here, where winter arrived this week with the first real snowfall of the season.

I took the moonlight image just a few minutes before posting this blog, on Tuesday night. I’ll use it as the starting point for my guided tour of Orion, which you can take on your next clear night. The next few will be beautifully moonlit and inviting — while you might not have snow, you can certainly see Orion and company wherever you are on the planet.

OK, prepare for take-off — next stop, Orion.

Right now, Orion rises in the early evening but by 11 p.m. stands high in the southeast for observers in mid-northern latitudes, just as the moonlit photo above shows him. For the tour map, I’ll use another photo (at right) that I took last week, on a snowless but very frosty night when the Moon was out of the way. A moonless night is a dark night, so that’s why the sky now looks star-filled and painted with the Milky Way running down the frame.

There’s little need to learn any trick to find Orion. His three Belt stars give him away — look south to see them late at night now. They’re surrounded by a bright rectangle of stars that outline the hunter’s body — among them, bluish Rigel at lower right, and reddish Betelgeuse at upper left, two of the most familiar of star names.

A couple of fast star facts:
☑ Rigel is a hot blue supergiant star 775 light years away and some 50,000 times more luminous than our Sun, making it one of the brightest stars in the sky.
☑ Betelgeuse is a red giant big enough to swallow the solar system out past the orbit of Mars — if it replaced the Sun.

Now, here are some handy tricks for learning the current sky:
1 Use the Belt stars as pointers — draw a line from them up and you come across Aldebaran, another red giant star that marks the eye of Taurus the bull.

2 Continue the line farther and you encounter the Pleiades, an unmistakable cluster of stars — well, sometimes mistakable: many people think it’s the Little Dipper. Nope, it’s a star cluster, not a constellation. And it’s a great sight through any optical aid. Binoculars show it well or any telescope at low power. You’ll see dozens of blue-white diamonds. My long exposure photo shows the cluster stars embedded in hazy nebulosity — a dusty cloud that the Pleiades happens to be lighting up as it passes through the nebula.

3 Now head back to the Belt. Draw a line down from the Belt and you arrive at Sirius, the brightest star in our night sky. By absolute measures, Rigel is brighter — but Sirius appears brighter in our sky because it is much closer to us, only 9 light years away, putting it in our galactic neighborhood. A couple of other fasts facts about Sirius:

☑ It’s called the Dog Star because it lies in the constellation of Canis Major, the large Hunting Dog of Orion.
☑ The first appearance of Sirius each year in the pre-dawn sky marked the start of the calendar to the ancient Egyptians.
☑ Sirius is 26 times brighter than our Sun and 1.75 times as big.

4 Return to the Belt again. Now drop straight down from the left star of the Belt, into the “Sword of Orion.” Use binoculars to scan for a fuzzy star. Better yet, use a telescope to find that fuzzy glow. Magnify it 50 times or so, and you’ll see it as a greenish cloud with wings arcing out to either side of the bright core. That’s the Orion Nebula, the most famous star-forming nebula in the sky. It is bright enough to show up even in the moonlight or from urban skies, at least through a telescope.

The long-exposure photo (above) that I took last week shows the area swimming in nebulosity. But you won’t see nearly as much as that through the eyepiece, even on a dark moonless night. The visual appearance of the nebula even to the “aided eye” is something much more subdued, and monochrome, perhaps with a touch of green, such as in the simulated eyepiece view here, at right. Your eye simply isn’t sensitive enough to pick up the brilliant colors and outlying wisps of nebulosity that a camera can record. Even so, the Orion Nebula is a wonderful sight, and well worth tracking down in Orion’s Sword.

Hope you enjoyed our brief tour of Orion and vicinity. Please be careful when opening the overhead compartments. Some of the contents may have shifted in flight. Bye-bye!

Next: The big and bright Moon of December

But in the meantime, be sure to check out Dave Mosher's excellent video version of the Carnival of Space for a tour of the week's best blogs from the sky.