What would the sky look like if Arcturus, Sirius or Alpha Centauri were our sun?

If Arcturus were put in place of the Sun it might look something like this at sunset, which would last an unusually long time given the vast dimensions of the star, some 25 times larger than our Sun. Credit: Roscosmos

I was out walking the other night around 11 o’clock when I noticed a new bright star poking through the trees low in the northeastern sky. For a moment I couldn’t figure it out, and then it came to me. Arcturus.

Arcturus, an orange giant star some 21 million miles in diameter, compared to the sun, Jupiter and other familiar stars.

Arcturus is a traditional spring-early summer star as that’s when it’s highest in the sky. But winter’s the time it first appears in the east as the midnight hour approaches. Arcturus is an orange-giant star 25 times larger than the Sun 36 light years from Earth.

If you’ve ever wondered how it might look in our sky, Russia’s Federal Space Agency or Roscosmos, has created a series of fun and instructive simulations of several familiar stars,including Arcturus, in place of the Sun.

While the Sun takes about two minutes to set once it touches the horizon, Arcturus’ massive disk would extend some13° across and require 52 minutes. Watching an Arcturian sunset would be a major time commitment reserved for weekends only.

Here are several other new stellar perspectives. In all, except perhaps Alpha Centauri, the Earth would roasted in the stars’ blazing heat and radiation. Keep that in mind as you take in the sights.

White-hot Sirius would blaze in our daytime sky. 1.75 times the size of the Sun and 26 times as luminous, we’d all be fried if Sirius stood where the Sun is. Credit: Roscosmos

How about a familiar triple star? This is Alpha Centauri, comprised of two stars slightly more massive and luminous than the Sun located 4.47 light years away. The third star (to the left) is Proxima Centauri, a dim red dwarf and third member of the system. Credit: Roscosmos

Vega in the constellation Lyra is our sit-in sun in this simulation. The star, 25 light years from Earth, rotates so rapidly it’s oval shaped instead of spherical. Vega measures 2.7 times the Sun’s diameter along its equator and is 36 times brighter than the Sun. The sight would make you go blind quickly. Earth would also be roasted in the heat. Credit: Roscosmos

Polaris or the North Star is a yellow supergiant 2,500 more luminous than the Sun and 45 times its size. What an eyeful we Earthlings would have if Polaris were our sun. Credit: Roscosmos

Here’s the whole works and more in a video in Russian. Enjoy! Tomorrow the fun continues when we’ll take a look at substituting planets and moons for the Sun.

Mercurial delights / Supernova in spiral galaxy M61 / Jupiter spots

Mercury shines brightly in the east-southeast more than an hour before sunrise this morning November 1. The planet remains well-placed for viewing for the coming 10 days. Credit: Bob King

Scattered thin clouds took nothing away from this morning’s otherwise clear sky. With the Moon waxing from quarter to gibbous phase, the slab of darkness between moonset and dawn gets sliced thinner every day. Starting November 4th the Moon will light the sky all night and not give back the darkness till next weekend. I took advantage of a moonless morning to set up the telescope to view two comets, a brand new supernova in the bright Virgo galaxy M61 and the planet Mercury at dawn.

Around 7 a.m. CDT (6 a.m. CDT) in bright twilight, Spica cleared the treetops about 5 degrees to the lower left of Mercury. Watch in the coming mornings as Spica slides up higher in the sky and Mercury slowly drops horizon-ward. Credit: Bob King

Normally I suggest looking for Mercury around 45 minutes before sunrise when it’s high enough for a good view, but if you have an wide open eastern horizon, go for it earlier. The planet is very bright right now at magnitude -0.6 — brighter than it’s nearest rival, Arcturus (0.0) located three outstretched fists to the upper left of Mercury. I was surprised at how bright and easy it was to see it more than an hour before sunrise.

In the next few mornings, Virgo’s brightest star Spica rises near the planet. Watch them do a do-si-do in the coming days as Spica passes Mercury.

Facing east about 50 minutes before sunrise tomorrow and Monday Nov. 2-3. Mercury will be near Spica and about three outstretched fists to the right and below Arcturus. Source: Stellarium

Gianluca Masi captured this view of the supernova 2014dt (tick marks) in the 9th magnitude barred spiral galaxy M61 in Virgo on Halloween. The galaxy is some 55 million light years from Earth. Credit: Gianluca Masi

Virgo brings more than a bright morning planet. Tucked with the broad “Y” or cup-shaped northern half of the constellation, the bright galaxy M61 glows with a brand new supernova visible in amateur telescopes.

Japanese amateur astronomer Koichi Itagaki discovered the new star on October 29 at magnitude +13.6. A little on the faint side, yes, but it has been slowly brightening. This isn’t the first time we’ve witnessed a supernova explosion in the galaxy. At least two others – 2006in and 2008ov – have been observed. Quite the hotbed!

View looking east just before the start of morning twilight. M61 is located in the big Virgo “Y” about three outstretched fists to the right and above brilliant Arcturus. Source: Stellarium

Enlarged view of Virgo to help you better track down M61. When you find it, the supernova will look like a star inside the galaxy east of the core. Click for a large version. Source: Stellarium

Right now, you’ll need an 8-inch or larger telescope and dark sky to see it. The best time is just before dawn when Virgo is highest in the eastern sky. Through the eyepiece of my 15-inch (37-cm) scope this morning the galaxy glowed big and round with a bright core. Supernova 2014dt was a dim “star” 40 arc seconds east and 7 seconds south of the nucleus. Use the maps above to help you find the galaxy.

This morning’s shadow transit of Jupiter’s largest moon Ganymede (left) and a future transit that will occur on November 8 between 3:35 – 7:12 a.m. CST. The Great Red Spot will also be nicely placed for viewing. Add 1 hour for EST, subtract 1 hour for MST and 2 hours for PST. Source: Meridian

I always save the bright planets for last not only because they provide a refreshingly bright treat after hunting comets and supernovae but also because I don’t want to destroy my night vision. But I got a great surprise when pointing the scope at Jupiter. Plain as could be, there was the shadow of the planet’s largest moon Ganymede silhouetted against the white clouds of the equatorial zone and next to it, Ganymede itself. For a minute it looked like two moons casting shadows on the planet. Compared to its shadow, Ganymede was smaller and gray-toned.

You can catch the next Ganymede shadow transit visible in the western hemisphere on the morning of November 8 from 3:35 to 7:12 a.m. CST. A 3-inch or larger telescope is all it takes to view it.

The sun rises just before 8 a.m. over the Wisconsin shoreline of Lake Superior this morning November 1. Credit: Bob King

What better way to top off a morning of sky watching than with a sunrise? Now maybe I’ll take a nap.

Hold my hand as we peer into the Bootes Void

The Big Dipper, the brightest part of the constellation Ursa Major the Great Bear, is followed down into the northwestern sky by twinkling orange Arcturus and the constellation Bootes, the Bear Guard. Stellarium

Most of us would consider Bootes the Bear Guard a spring constellation. That’s when it first appears in the eastern sky, following the tail of Ursa Major the Great Bear as the snow drifts recede. Come fall, Bootes (Boh-OH-tease) and its bright luminary Arcturus recline in the west within spitting distance of the Dipper.

Every evening I look up to check on the condition of the sky. Arcturus is either flashing happily or gone missing, hidden by clouds. Gazing up from Arcturus, it’s easy to trace out the remaining points of starlight that form the kite-like figure of Bootes. Like a kite let go, Bootes drifts away to the west as the night deepens.

The next clear night, follow the arc of the Dipper’s Handle to Arcturus and then work your way up and around to pick out the constellation’s fainter stars. If you now direct your gaze to a blank spot between Bootes and the end of the Dipper’s handle, you’ll be staring at the center of a remarkable nothingness, the Bootes Void.

Map of the Bootes Void showing it alongside other dense superclusters of galaxies. Credit: Richard Powell

Normally we talk about the presence of something in the sky in this blog, but today we’ll focus on absence. The Void, a roughly spherical realm of space 250 million light years in diameter, is virtually empty. Space is already empty enough. If the sun were shrunk down to the size of a grapefruit, the nearest star system, Alpha Centauri, would be 2,000 miles away. From there, it’s another 1,000 miles to the next closest, Barnard’s Star.

American astronomer Robert Kirschner discovered the void in 1981 as part of a survey to measure how fast distant galaxies were fleeing from one another as the fabric of space expands in the ever-widening wake of the Big Bang. Six years later, Kirschner and team turned up 8 galaxies in this vast volume of space centered 700 million light years from Earth. By the late ’90s only 60 galaxies were known, making the Void not as devoid of galaxies as originally thought.

Still, the wind blows through it like a ghost town. Considering that the average distance between galaxies in typically a few million light years, the Void should contain some 10,000 inhabitants. Where have they fled?

The Millenium Simulation will give you a feel for the large-scale structure of the universe. Enjoy the ride!

Galaxies are vast assemblages of stars, clusters, gas clouds and planets thousands of light years across. Their mass gives them considerable gravitational might, so they’re attracted to one another. Over the lifetime of the universe, galaxies congregate into strands, clumps and clusters. The surrounding space empties out like a parking lot at closing time and becomes a void.

The Bootes Void is no ordinary emptiness. It’s HUGE. Too big to have formed with the current lifetime of the universe say astronomers. That’s why it’s thought to have agglomerated from smaller voids that merged together to form one of the largest voids in the known universe, a so-called supervoid.

Millenium Simulation of the large-scale structure of the universe shows a sponge-like texture of filaments of galaxies threading empty voids of space. The galaxies – each too tiny to see individually at this huge scale – clump around invisible dark matter and each other. Credit: Millenium Simulation

Galaxy clumping has amazing consequences for the large-scale structure of the universe. Astronomers think the visible matter of the universe clustered around clumps of dark matter, which makes up 73% of all the ‘stuff’ out there, shortly after the Big Bang. Once galaxies formed, they continued their clustering ways up to the present day. Instead of a random distribution of matter across space, the universe looks like a sponge where hundreds of billions of galaxies swirl in filaments and nodes around the comparatively empty voids.

Funny how the biggest things in the universe can be so surprisingly close to home. Look up toward the Big Dipper and Arcturus in the western sky after sundown and think of where you are.

Magnificent Mars and a celestial lightsaber

Face southeast around 10:30 p.m. local time and you’ll be pleasantly surprised at the line of bright “stars” there. The brightest is the planet Mars. Photo taken March 24, 2014 at 10:30 p.m. Credit: Bob King

Last night Mars blazed in the treetops. I’m still amazed at how bright the planet’s become in the past few weeks. Paired up with the bright, blue-white star Spica in Virgo, it’s unmistakable. The two clear the southeastern horizon together around 9:30 and become very obvious an hour later.

The magnitude scale. Negative magnitudes are brighter than positive ones. Credit: Univ. Nebraska-Lincoln

Reach your arm toward Mars and move “two fists” to its upper left and you’ll spot Arcturus, the brightest star in the constellation Bootes the Herdsman. Together the three form a striking “lightsaber” of luminaries.

Looking more closely, you’ll notice that each is a different brightness. Thanks to fortunate circumstance, they differ from each other by almost exactly one magnitude, the standard unit of measurement astronomers use to measure star brightness.

First magnitude stars are 2.5 times brighter than second magnitude stars, which are 2.5 times brighter than stars of third magnitude and so on.

Mars rules the roost at magnitude -1.2, Arcturus is next at 0 and Spica at 1.0. If you’ve ever wondered what a magnitude of difference between celestial objects looks like, check this convenient live demonstration the next clear evening.

Arcturus and Spica will remain fixed in their brightness – at least for thousands of years – but the light of Mars and the other planets vary depending on their distance from Earth. In astronomy, there’s a simple rule: when close, objects appear brighter than when farther away. Mars’ magnitude varies more than most of the planets with extremes of -3.0 when nearest to 1.6 when most distant. That’s a difference of nearly 100 times.

Because Mars’ orbit is more elliptical than Earth’s, distances between the two planets are vary significantly, causing the planet to vary greatly in brightness. Credit: Wikipedia with additions Bob King

These large variations directly relate to Mars’ more elliptical (oval) orbit. When the Red Planet is on the far end of its elliptical orbit at the same time Earth’s on the opposite side of the sun, it’s farthest and faintest. When on the far end of its orbit on the same side of the sun as our planet, it handily outshines every star and planet in the sky except Venus.

Mars on March 19, 2014 with some of its more prominent features marked. Hellas and Syrtis Major are relatively easy to see. The north polar cap is quite small now. Credit: Damian Peach

Even if you don’t give two shakes about magnitudes, make sure you take in a view of all three of these night sky gems. If you have a telescope and are observing from the western hemisphere, this is the best week to see the bright false south polar cap.

The “cap” is really Hellas, the largest crater on Mars, covered in frost and bedecked with clouds during southern hemisphere winter.

Look for a bright lens-shaped spot on the planet’s south end around midnight early this week and closer to 1-2 a.m. next weekend. It’ quite obvious in 6-inch and larger telescopes in steady air.

Don’t miss this Saturday’s Saturn-moon conjunction

The big picture in the southern sky this Saturday morning at dawn shows the moon just a degree below Saturn with Mars at upper right in the south and Venus very low in the southeastern sky. Stellarium

A very nice, close pairing of Saturn and the waning 3rd quarter moon will happen Saturday morning at dawn. With late sunrises still the rule, this should be a very easy event to catch even through a parted window shade.

At closest, the two will be just two moon widths or 1 degree apart. Saturn’s in Libra the Scales, a dim constellation that precedes the brighter, more picturesque Scorpius the Scorpion. You can see part of the scorpion to the lower left of the duo. In particular, look for the bright red supergiant star Antares.

Both Libra and Scorpius are late spring-early summer constellations, visible at nightfall in May when the butterflies fly. It’s thoughts like these that lift our spirits on cold winter nights. I had the same feeling two nights ago when I happened to be out observing around 11:30 p.m. and caught sight of a “new” star flashing in the northeastern sky – Arcturus. If there were ever a vanguard of spring, this star is it. Arcturus creeps higher every frigid night until the snow is gone, the leaves turn out and jackets are shed.

Mobile phone shot of Venus in twilight Monday morning. Credit: Sean Cassidy

While you’re out enjoying Saturday’s conjunction (by the way, Saturday’s named for the Roman god Saturn) stay out a little longer to enjoy the reappearance of Venus low in the southeastern sky about 40 minutes before sunrise. Sean’s photo will help you know what to expect.

Think pink for spring – Arcturus is back!

This map shows the sky around 10 p.m. local time in facing east tonight Feb. 24. Arcturus, the brightest star in the constellation Bootes the Herdsman, is well below the Big Dipper. The nearly full moon joins the scene a short distance from Leo’s brightest star Regulus. Maps created with Stellarium

I was startled two nights ago when I turned down the road and spied pink Arcturus scintillating low in the eastern sky. With snow all around and more on the way, my psyche was steeped in winter. So what was this big, bright spring star doing staring me in the face?

Find Arcturus using the old adage “Arc to Arcturus” by sliding down the arc of the Big Dipper’s handle.

After the sun, Arcturus is the 4th brightest star in the sky. It pokes up around 10 o’clock in late February. You’ll find it with ease simply by following the curve of the Big Dipper’s handle downward toward the eastern horizon. Its name comes from the ancient Greek word “arktos” for bear and means “Guardian of the Bear”. Appropriate considering it rides herd on Ursa Major the Great Bear, the brightest part of which is the Big Dipper.

The calendar notwithstanding, Arcturus is a true “spring star”. Come May, when the first mosquitos begin to whine, you’ll find it perched high in the southern sky lording over the landscape much as Orion does now during the early evening hours.

Right now the Bear Watcher is hunkered down in the east, sparking through tree branches and over neighborhood rooftops. Twinkling, most obvious in the brighter stars, is caused by shifting air currents that are more pronounced at lower altitudes.

Arcturus, an orange giant star some 21 million miles in diameter, compared to the sun, Jupiter and other familiar stars.

Funny that the atmosphere can jiggle the light of such a massive star about as if it were as flighty a thing as a dandelion seed. Arcturus is an orange giant star 25 times larger than the sun, but all that girth is reduced to a trembling point of light 36 light years (216 trillion miles) from Earth. Its true brilliance is likewise masked by distance. Put in place of the sun, Arcturus would dazzle 113 times brighter and cover an area of sky half as big as the Big Dipper. As for color, it looks pinkish to my eye. Others see it as red-orange.

Watch this flush-faced star loft higher and higher in the east in the coming weeks with the return of the spring season. There’s a special bonus if you go out tonight. The moon, on its way to becoming the Full Snow Moon tomorrow night, will shine near Leo the Lion’s brightest star Regulus.

Vega’s asteroid belts hint at hidden planets

This conceptual illustration depicts an asteroid belt around the bright star Vega. Evidence for the ring of debris comes from NASA and ESA space telescopes. Credit: NASA/JPL-Caltech

Look low in the northwestern sky at dusk in mid-January and you’ll spy a bright, sparkling star. That’s Vega, Lyra the Harp’s most luminous star and the fifth brightest in the sky … after the sun, of course. We’ve known since 1983 that Vega is surrounded by a dusty disk of debris, the first star discovered to have one. Warmed by the star, dust radiates a feeble heat that was detected by the NASA’s orbiting Infrared Astronomical Satellite (IRAS).

Look for Vega above the trees during the early evening. This map shows the sky facing northwest around 6:30 p.m. local time. Maps created with Stellarium

Earlier this week NASA announced evidence for two separate asteroid belts and potential planets around the star. Sound familiar? Our solar system has both an inner, warm asteroid belt located between Mars and Jupiter and a cold, outer belt of “ice”-teroids beyond Neptune. Using NASA’s Spitzer Space Telescope and the European Space Agency Herschel Space Telescope, both of which are optimized to detect infrared (heat) light, astronomers detected two bands of dust created and replenished by collisions of comets and rocky asteroids around Vega.

The amount of dust indicates that Vega’s belts have far more material than our own asteroid belts, no surprise given that our solar system is far older – about 5 billion years – and has had a much longer time to “clean house” through planet-asteroid interactions. Vega, a star with twice the sun’s mass and 36 times more luminous, is thought to be a youthful 600 million years old.

The Vega system, with its own set of asteroid-comet belts, is compared to our solar system in this illustration. The relative size of our system compared to Vega is illustrated by the small drawing in the middle. On the right, our solar system is scaled up four times. Both inner and outer belts have similar proportions. Credit: NASA/JPL-Caltech

Check out the layout of Vega’s belts. Back at home, the main asteroid belt is kept in place by the interplay of gravity between Jupiter and the inner planets, while the outer Kuiper Belt was fashioned by the giant outer planets. Although we can’t see them yet, there are almost certainly planets at play in maintaining Vega’s belts, too. Ain’t gravity fun?

Arcturus, auger of spring, comes up around midnight below the handle of the Big Dipper.

Last night while out checking on a supernova in a galaxy in Leo, a bright spark of ruby light caught my eye low in the northeastern sky. I almost didn’t recognize it, but a second later it hit me –  Arcturus. The time was midnight and already the sky offered this taste of spring.

Arcturus is a brilliant ruddy star that stands high in the south come May. Because of its prominence in late spring and early summer, it’s imbued with memories of warm nights and green grass. In January, Arcturus still slumbers below the eastern horizon until shortly before midnight. Seeing it poke between the trees warmed me up … just a little.

The sun at 10:30 a.m. CST Jan. 10, 2013 photographed by the Solar Dynamics Observatory. The pair of sunspots at left, region 1654, is big enough to see with the naked eye using a safe solar filter. This group harbors the potential for significant solar flares. Credit: NASA

Nicer yet was the sun, which burned away in a blue sky this morning. Lots of sunspot groups, including two large new spots that have recently rounded the sun’s eastern limb, have increased the chance for solar flares in the coming days.

I don’t know about you but I miss the aurora. The last one good show in northern Minnesota happened in November. Let’s hope we won’t have to wait much longer.

Solar blowout and a wicked star-planet alignment

Sunspot group 1476 "blemishes" the sun this morning as it rose over Lake Superior in Duluth, Minn. Photo: Bob King

It’s always worth getting up to see a sunrise. Sure, you can’t concentrate and your eyes weigh a pound a piece by afternoon, but it’s worth the lift you feel watching a star rise out of a lake. I saw the sun slowly ease out of Lake Superior in Duluth this morning, and for a few minutes it was safe enough to take pictures with a telephoto lens.

I enjoy imperfections. Matter of fact, I’m built on flaws both inherited and accumulated over the years. Once the solar disk freed itself from the horizon, I could see it also had a blemish, a piece of crud that wouldn’t wipe off. A monster sunspot!

That spot group was plainly visible in the camera once the sun was up. An hour later I easily saw it from home with the naked eye from behind a pair of eclipse glasses.

The sun photograhed this morning through a 3-inch refractor with solar filter later this morning. The big group is 1476; smaller 1477 is at bottom. Photo: Bob King

Now spanning more than 12 Earths, the group is magnificent to view in a small telescope. The main spot has a long string of followers and reminds me of mother goose and her goslings.  Exquisitely small black umbral spots contrasted with the pale, encircling penumbra around the main or lead spot in the group. The photo only hints at the beauty and complexity of the group.

Because the sun rotates on its axis about once every four weeks, we can watch the evolution of this group with each passing day.

In active sunspot groups like 1476, new spots form and evolve quickly. Some expand rapidly and last days or weeks. Others appear and disappear in just a day. Day to day changes are obvious through a small telescope and show us just how dynamic a star can be. As always, you’ll need a safe filter to look directly at the sun. Here’s a link to a recent blog listing good sources.

Must-see video of last night’s M5.7 flare from Region 1476. The best part is the audio. Crank it up!

At 11:18 p.m. Central time last night, sunspot region 1476 blasted off a significant M5-class flare. Though large, it’s not directed toward Earth. For the moment, none of the more powerful X-class flares have made an appearance.

All the activity with more to come is because 1476 is a delta group, where positive and negative magnetic fields (north and south poles) are packed so close together, there’s great potential for instability and the release of energy in the form of solar flares. While there’s only a small chance of auroras for the far north this evening from effects not related to these spots, let’s cross our fingers for possible weekend auroras related to the big group.

From top to bottom: Arcturus, Saturn and Spica form a straight line in the sky last night. Photo: Bob King

Last night when members of our local astronomy club departed the planetarium after the monthly meeting, we instinctively all looked up. Aha! The sky was clear. High up in the southeast was a most striking arrangement: Arcturus, Saturn and Spica all lay in a straight line.

Being humans, we can’t help but be drawn to patterns, and this one you couldn’t miss. Try spying it yourself the next clear night. Go out from 9:30 p.m. on and look well up in the southeastern sky. Arcturus is the bright, orange-red star; below it you’ll find the duo of Saturn and Spica. It’s just cool.

The line will remain straight for about the next several nights. After that, Saturn’s motion to the right (west) will break the pattern. When will you first notice this?

Arc to Mars-turus

Jupiiter pokes out from between "cloud streets" high in the southern sky around 6:30 p.m. on a recent evening. Photo: Bob King

Amazing how quickly the stars and planets slide by. A few months ago you had to stay up late to get a good look at Jupiter. Now it’s front and center (due south) at dinnertime. Everything celestial moves up from the east, peaks at maximum elevation in the southern sky and then eases down into the west. And it’s all because we live on an unstoppable planet traveling 18.5 miles a second around the sun.

You wouldn’t expect the landscape to remain unchanged while looking out the window of a car traveling at 65 mph. Scenes shift by the minute. It’s the same with Earth. As we gaze out into the night sky, starscapes change over days, week and months as we speed ever onward in our orbit. The Summer Triangle’s replaced by the Great Square of Pegasus, which is replaced by Orion, which is replaced by Leo and on and on it goes. The one difference between a fast car and Earth is that the same starry scenes repeat year after year because we travel in a closed loop around the sun, not a straight line.

With night after night of clear skies, January’s Full Wolf Moon got a lot of lookers in the Duluth region earlier this week. Last night through clouds, I could still see enough of the moon to tell it had changed shape. It’s beyond full now and in waning gibbous phase. Looked like an egg to me. And since the angle between the moon, Earth and sun is narrowing, less and less of the moon is illuminated by sunlight with each passing night. We’ll be watching it wane from gibbous to 3rd quarter and finally morning crescent in the next 10 days. The moon also rises later and later as its orbital motion carries it ever eastward.

A grand arc connect the moon-Regulus pair, Mars, Saturn-Spica and Antares in Scorpius tomorrow morning just before dawn. Created with Stellarium

For those of you up around 6 a.m. tomorrow morning (Jan. 12), take a look across the full breadth of the southern sky. The moon will be in conjunction with and directly below Leo’s brightest star Regulus. Now let your gaze slide eastward and you’ll soon bump into fiery orange Mars. Continuing down and left, you’ll soon arrive at the attractive pair of “eyes” formed by Spica and Saturn and finally ruddy Antares low above the southeastern horizon.

Above this grand arc, high in the south, shines the brilliant orange-hued Arcturus. Mars and Arcturus are a near perfect match in color and brightness at the moment. Do their colors look the same to your eye or are they different? Mars is officially at magnitude 0.0 and Arcturus is listed at -0.04, ever so slightly brighter. Can you see this tiny difference? There’s at least one way they should stand apart from one another. I’ll give you a hint: it has to do with our atmosphere. Go out for a look and let us know what you see.

The ghost of Comet Elenin haunts the morning sky

Comet Elenin is a very faint, elongated streak as photographed through a 4-inch refracting telescope early this morning from the GRAS network in New Mexico. The picture covers about 2 degrees from side to side. Credit: Rolando Ligustri

For those of you who checked yesterday’s blog, you already know that the German ROSAT (Roentgen X-ray satellite) burned up in the atmosphere last night between 8:45 and 9:15 p.m. CDT. To the best of my knowledge, after digging around various websites, it appears to have come down over the Indian Ocean north of the coral atoll Diego Garcia. Too bad there’s so much water on this planet otherwise we’d have lots more satellite parts and meteorites in our collections.

I wanted to share the most recent pictures of Comet Elenin with you. Amateur astronomers have been busy the past few mornings losing sleep photographing and trying to see the comet through their telescopes. The moon is out of the way and Elenin is presently high up in a dark sky after about 3 a.m. These are the conditions we’ve been waiting for for months! And finally, enough pictures have been taken to confirm that the comet is really there.

Another view of Comet Elenin taken this morning with a 10-inch wide-field telescope in Austria. Credit: Michael Jäger

The photos show a faint, elongated cloud of spreading comet dust, the last gasp of what was to be fall’s best bet for a bright comet. Its ghostly appearance hints at how difficult it’s been to see with one’s own eyes in a telescope. To date, only one observer – Juan Jose Gonzalez – has spotted this wispy remnant from his mountaintop observing site in northern Spain using an 8-inch telescope. Jacob Cerny of the Czech Republic is the second person to observe it, but it was so challenging, he listed his observation as “uncertain”.

Take a look at Elenin’s morphology or form. It reminds me of the Headless Horseman from The Legend of Sleepy Hollow. Indeed, the head of the comet is no longer a separate entity as it was before the August breakup. All is one galloping streak of light.

Comet Elenin will continue along its orbit as it slowly moves farther from Earth with each passing day, fading and expanding as it does and likely to never return. Even though this demure object has been wrongly credited with causing earthquakes and other mayhem, the bright side has been a lively discussion of comets and other topics astronomical. These are good things.

Several readers have mentioned or made reference to Arcturus in recent days. I thought it would be an opportune time to give the star – the 4th brightest in the sky after Sirius, Canopus and Alpha Centauri – one last evening farewell before we get up 11 hours later at dawn to welcome it back. What?

Use the handle of the Dipper to "arc" your way to Arcturus during the early evening. This map shows the sky facing northwest around 7:30 p.m. local time. Maps created with Stellarium

Arcturus, an orange giant star with a distinctive warm tint, hovers low in the northwestern sky off the handle of the Big Dipper on late October evenings. It’s best to catch it an hour or so after sunset during evening twilight when the star is high enough to see relatively easily. As dusk melts into darkness, try looking two outstretched “fists” directly above Arcturus for the little horseshoe-shaped constellation Corona Borealis the Northern Crown.

If you have an open view to the northeast during early dawn, you can watch Arcturus return to view - truly, a star for all seasons! This map shows the sky facing northeast around 6:15 a.m. tomorrow morning.

Arcturus makes its first evening appearance in late winter in the northeastern sky. By May and June, it’s high in the south at twilight’s end; its warm light has come to be associated with warming temperatures and the arrival of summer. In fall, the star drops off into the northwest and finally sets, but because nights are better than 12 hours long in late October, Earth’s rotation carries it back into view for observers in mid-northern latitudes. Watch for its winking red light in the northeast at dawn. In a sense, we never lose Arcturus.

The star’s northern location on the celestial sphere is also responsible for its continuous visibility. The closer a star is to the North Star – the pivot-point star due north that remains in one spot in the sky – the longer it remains visible. All stars within a circle with a radius the same as your latitude never set at all. They’re called circumpolar stars because they circle around the North Star day and night without ever touching the horizon. While Arcturus is not quite circumpolar for Duluth, Minn., the fortuitous combination of northerly location and long nights allow it to be seen every month of the year.