I'm a long-time amateur astronomer and member of the American Association of Variable Star Observers (AAVSO). My observing passions include everything from auroras to Z Cam stars. I also write a daily astronomy blog called Astro Bob. My new book, "Wonders of the Night Sky You Must See Before You Die", a bucket list of essential sky sights, will publish in April. It's currently available for pre-order at Amazon and BN.
Starting Friday the moon will be your guide to Venus' return to the evening sky. This map shows the sky facing west-northwest about 30 minutes after sunset across the middle of the U.S., but it's useful from 30-50 degrees north. Venus will be 4 degrees high at the time. Friday's moon is very thin! Stellarium
Has Venus finally come out of hiding? For the past couple months it’s kept close to the sun, hidden in its glare, but come Friday, sky watchers in mid-northern latitudes may get their first shot at seeing the planet’s return to the evening sky.
It won’t be easy, but you’ll have help from the knife-edged crescent moon. Like a spring bloom raising its head from the dark earth, Venus will poke just 4 degrees above the western horizon a half hour after sunset. The moon will be about 2 degrees to the lower left of the planet. Seeing both requires a wide open view to the west and a clean, cloudless sky. It also helps to know when the sun sets for your location – easily found by clicking HERE.
Most any binoculars will prove useful for seeing Venus in twilight this week. One of my (inexpensive) favorites is a pair of Nikon Action 8x40s. Once you spot the planet in binoculars, try to see it with your naked eye. Credit: Bob King
Take along a pair of binoculars. They’ll help fish out both moon and planet in the bright twilight sky. It’s also advantageous to arrive at your viewing spot a little early. Enjoy the sunset, and then take a minute to make sure you’re binoculars are focused at infinity. If you don’t, Venus will be a blur and much harder to find. I usually focus mine on a cloud or the very farthest thing out along the horizon.
Once you’re all set, point your binoculars in the sunset direction and slowly sweep back and forth. Venus will be a short distance to the left or south of the brightest glow remaining along the horizon. Since most binoculars have a field of view of 4 or 5 degrees, when you place the horizon at the bottom of the view, the moon should appear in the middle of the field and Venus up near the top. Look higher and lower and farther left and right to be thorough. Once spotted in binoculars, take the visual challenge and see if you can find it without optical aid.
Venus punctuates a colorful sky low in the west at dusk in August 2008. Credit: Bob King
If you succeed, you’ll be rewarded with an elegant eyeful. Swamped in skylight, Venus will appear unusually meek but still possess its classic fiery brilliance. The newborn crescent will float just a degree and a half (three full moon diameters) away. From the U.S. east coast, the moon will be just 24 hours old; from the west coast 27 hours. Seeing such a young moon is a rarity in itself, but in the company of Venus that much finer.
Let’s say conditions aren’t ideal and you miss the pair on Friday. Well, try again on Saturday. The moon will be higher and much easier to see. Use it as a bow to shoot an imaginary arrow horizon-ward to Venus. And did I mention Jupiter? The planet that cheerily lit up our winter nights is now departing in the west. Watch for it to have a close encounter with Venus on the nights of May 27-28.
With its perpetual clouds, Venus would be a most distressing planet to any skywatcher unfortunate enough to live there. Yet it’s those same clouds that make it the most brilliant planet in the solar system seen from Earth. Clouds reflect sunlight splendidly. Combined with Venus’ proximity to Earth, it’s no wonder the planet earned the title of goddess of love and beauty.
As Venus and Earth revolve around the sun at different speeds, we see Venus from a constantly changing perspective. In May, the planet is slightly to the left or east of the sun and looks like a miniature full moon at dusk. Come Halloween it resembles a half-moon and a crescent at Christmas. Credit: Bob King
In the first 3 months of this year, Venus remained close to the sun in the morning sky and difficult to see. Then on March 28, it passed behind the sun on the opposite side of Earth’s orbit; astronomers call the lineup superior conjunction. Seen from Earth, Venus looked like a tiny full moon. We’re now about 6 weeks past conjunction and the planet has begun to peek out into the evening sky. At 98% illuminated, it still looks nearly full through a telescope, but that will change in the coming months as Venus approaches Earth in its speedier orbit. Watch for the goddess to grow larger in apparent size while at the same time slimming down her phase from full to half to crescent. Good luck getting re-acquainted this weekend!
The Very Large Array, one of the world's premier astronomical radio observatories, consists of 27 radio antennas in a Y-shaped configuration 50 miles west of Socorro, New Mexico. Each antenna is 82 feet (25 m) in diameter. The data from the antennas is combined electronically to give the resolution of an antenna 22 miles (36 km) across. Image courtesy of NRAO/AUI and NRAO
Thanks to Channel 37, radio astronomers keep tabs on everything from the Sun to pulsars to the lonely spaces between the stars. This particular frequency, squarely in the middle of the UHF TVbroadcast band, has been reserved for radio astronomy since 1963, when astronomers successfully lobbied the FCC to keep it TV-free.
Back then UHF TV stations were few and far between. Now there are hundreds, and I’m sure a few would love to soak up that last sliver of spectrum. Sorry Charley, the moratorium is still in effect to this day. Not only that, but it’s observed in most countries across the world.
Channel 37, a slice of the radio spectrum from 608 and 614 Megahertz (MHz) reserved for radio astronomy, sits in the middle of the UHF TV band. Click to see the full spectrum. Credit: US Dept. of Commerce
So what’s so important about Channel 37? Well, it’s smack in the middle of two other important bands already allocated to radio astronomy – 410 Megahertz (MHz) and 1.4 Gigahertz (Gz). Without it, radio astronomers would lose a key window in an otherwise continuous radio view of the sky. Imagine a 3-panel bay window with the middle pane painted black. Who wants THAT?
The visible colors, infrared, radio, X-rays and gamma rays are all forms of light and comprise the electromagnetic spectrum. Here you can compare their wavelengths with familiar objects and see how their frequencies (bottom numbers) increase with decreasing wavelength. Credit: ESA
Channel 37 occupies a band spanning from 608-614 MHz. A word about Hertz. Radio waves are a form of light just like the colors we see in the rainbow or the X-rays doctors use to probe our bones. Only difference is, our eyes aren’t sensitive to them. But we can build instruments like X-ray machines and radio telescopes to “see” them for us.
Diagram showing what how Earth’s atmosphere allows visible light, a portion of infrared and radio light to reach the ground from outer space but filters shorter-wavelength, more dangerous forms of light like X-rays and gamma rays. To study the cosmos in these varieties of light, orbiting telescopes are required.
Every color of light has a characteristic wavelength and frequency. Wavelength is the distance between successive crests in a light wave which you can visualize as a wave moving across a pond. Waves of visible light range from one-millionth to one-billionth of a meter, comparable to the size of a virus or DNA molecule.
X-rays crests are jammed together even more tightly – one X-ray is only as big as an small atom. Radio waves fill out the opposite end of the spectrum with wavelengths ranging from baseball-sized to more than 600 miles (1000 km) long.
The frequency of a light wave is measured by how many crests pass a given point over a given time. If only one crest passes that point every second, the light beam has a frequency of 1 cycle per second or 1Hertz. Blue light has a wavelength of 462 billionths of a meter and frequency of 645 trillion Hertz (645 Terahertz).
If our eyes could see radio light, this is what the sky would look like. What appear to be stars are actually distant galaxies glowing brightly with energy radiated as matter gets sucked down black holes in the cores. The wispy arcs and shells are the remnants of exploding supernovae. Since air molecules don’t scatter radio waves like they do visible light to create a blue sky, the sky would be dark even on a sunny day. Credit: National Science Foundation
The higher the frequency, the greater the energy the light carries. X-rays have frequencies starting around 30 quadrillion Hertz (30 petahertz or 30 PHz), enough juice to damage body cells if you get too much exposure. Even ultraviolet light has power to burn skin as many of us who’ve spent time outdoors in summer without sunscreen are aware.
Radio waves are the gentle giants of the electromagnetic spectrum. Their enormous wavelengths mean low frequencies. Channel 37 radio waves have more modest frequencies of around 600 million Hertz (MHz), while the longest radio waves deliver crests almost twice the width of Lake Superior at a rate of 3 to 300 Hertz.
The sun as it would look in the radio portion of the spectrum at a frequency of 1.4 gigahertz (GHz). Image courtesy of the National Radio Astronomy Observatory (NRAO/AUI)
If Channel 37 were ever lost to TV, the gap would mean a loss of information about the distribution of cosmic rays in the Milky Way galaxy and rapidly rotating stars called pulsars created in the wake of supernovae. Closer to home, observations in the 608-614 MHz band allow astronomers track bursts of radio energy produced by particles blasted out by solar flares traveling through the sun’s outer atmosphere. Some of these can have powerful effects on Earth. No wonder astronomers want to keep this slice of the electromagnetic spectrum quiet. For more details on how useful this sliver is to radio astronomy, click HERE.
Just as optical astronomers seek the darkest sites for their telescopes to probe the most remote corners of the universe, so too does radio astronomy need slices of silence to listen to the faintest whispers of the cosmos.
On May 6 a beautiful thin moon will be near Comet Lemmon at dawn. This map shows the sky about 1 1/4 hours before sunrise. Stellarium
If you honed your observing chops on Comet PANSTARRS this spring, consider dropping in on Comet Lemmon, now returning to the dawn sky. Southern hemisphere observers saw this comet at its brightest in March when it briefly became dimly visible with the naked eye. It’s now faded to around magnitude 6, the same as the faintest stars you can see under a rural sky.
Because it’s been “vacationing” in the southern constellations, northerners have had to wait until now to see it.
Comet Lemmon with gas (left) and dust tails on April 24. Click to see a short movie showing rapid changes in the comet’s tail in 25 minutes. Credit: Gerald Rhemann
Like PANSTARRS, C/2012 F6 Lemmon is visible in modest-sized binoculars (7x35s, 10x50s) as a small, fuzzy ball of light with perhaps a faint tail. Watch for it to slowly track along the eastern side of the Great Square of Pegasus for the remainder of April and May. It competes with twilight low in the eastern sky this week but gradually becomes better placed for viewing as May unfolds. The best time to look is about an hour and a half before sunrise now and 2 hours before sunrise by mid-May.
The waning moon interferes some until around May 5. On the 6th, watch for the thin lunar crescent moon to pass 8 degrees below the comet. Around that time, we’ll finally get a good view of Lemmon in a dark, moonles sky just before the start of dawn.
On May 6 a beautiful thin moon will be near Comet Lemmon at dawn. This map shows the sky about 1 1/4 hours before sunrise. Stellarium
Comet Lemmon will fade from naked eye limit to a dim binocular smudge of 7.5 magnitude by mid-May. If you have a telescope, look for a pair of tails – a short, diffuse one of dust particles and the straight, streak-like gas tail fluorescing in the sun’s ultraviolet light. The tails point approximately to the south-southwest. Catch this comet while you can!
While no elements have been found in space that aren't also present on Earth, there are chemical compounds that are unique to other planets, meteorites and found in the space between the stars. Credit: NASA
I’m often asked by students in my community education astronomy classes whether any new elements have been found in outer space unknown on Earth. The answer to the question is no – nature uses the same 98 natural elements to fashion everything from the familiar stars and planets to those in the farthest galaxies we can see. Outside of an occasional compound or mineral, Earth is the place where you’ll find more exotic elements than anywhere else in the universe.
An element is a pure substance made of just one type of atom. What sets one element apart from another is the number of protons in the nuclei of its atoms. Any atom with six protons will always be carbon, 79 protons gold, 94 protons plutonium and 1 proton hydrogen. The proton number is also the element’s atomic number on the periodic table of elements. Elements in the table are arranged according to their atomic number.
Atoms are made of protons, neutrons and orbiting electrons. The number of protons in atom’s nucleus makes it unique from all the others. Hydrogen, the simplest element, has one; carbon has six.
The two most common elements are hydrogen and helium, numbers 1 and 2 in the periodic table; together they make up 98% of all the visible matter in the universe. The remaining 2% includes everything else from lightweight lithium (number 3) all the way up to californium (98), the heaviest natural element found on Earth and in the stars. Californium is unstable and “decays” into simpler elements. Although scientists make it in the lab by bombarding berkelium (97) with neutrons, trace amounts of this very rare element are found naturally in rich uranium deposits.
When I was in high school studying chemistry, the periodic table of elements ended at Lawrencium (103). At present there are 118 elements, the most recent one created in the lab being ununoctium (you-nah-NOC-tee-um). Matter of fact, all the elements beyond 98 are artificial, brought to life in nuclear reactors or in particle accelerator experiments. They live very short lives. With so many positively-charged protons pushing against one another in their nuclei, these elements quickly break apart into simpler ones in a process called radioactive decay.
Artist’s concept of the first stars in the Universe turning on some 200 million years after the Big Bang. These first suns were made of almost pure hydrogen and helium. They and later generations cooked up heavier elements that were later incorporated into the sun and us. Credit: NASA/WMAP Science Team
Back at the time of the Big Bang, when the universe sprang into existence, only the simplest elements – hydrogen, helium and trace amounts of lithium – were cooked up. You can’t build a planet from such fluffy stuff. It took the first generation of stars, which formed from these basic building blocks, to synthesize more complicated elements like carbon, oxygen, sulfur and the like via nuclear fusion in their cores.
When the stars exploded as supernovae, not only were these brand new elements blasted into space, but the enormous heat and pressure during the blast built even heavier elements like gold, copper, mercury and lead. All became incorporated in a second generation of stars. And a third.
The 2% of star-made elements, which include carbon, oxygen, nitrogen and silicon among others, went to build the planets and later became essential for life. We’re made of highly processed material you and I. The atoms of our beings have been in and out of the cores of several generations of stars. Think about this good and hard and you might just get in touch with your own “inner star”.
Common table salt is formed of tight-fitting atoms of sodium and chlorine. Each elements has its own individual character – one’s a flammable metal (sodium), the other a dangerous gas. Put them together and out comes a safe, tasty seasoning. Credit: Wikipedia
Let’s reframe the question about exotic materials in space not present on Earth. Instead of elements, if we look at compounds, we hit paydirt. A compound is also a pure substance but consists of two or more chemical elements joined together. Familiar compounds include water (two hydrogens joined to one oxygen) and salt (one sodium and one chlorine).
A selection of molecules (chemical compounds) including water found in the Orion Nebula detected by the Herschel Space Telescope. Credit: ESA, HEXOS and the HIFI Consortium E. Bergin
Astronomers have found about 220 compounds or molecules in outer space many of them with siblings on Earth but some alien. We don’t have to look far to find them since a few have been delivered right to our doorstep as rocky packages called meteorites. Here’s a short list of new minerals that formed within asteroids (where meteorites originate) under conditions very different from those found on Earth:
* Barringerite – a metallic compound made of iron, nickel and phosphorus
* Oldhamite – brown mineral made of calcium, magnesium and sulfur
* Kosmochlor – green mineral containing calcium, chromium, silicon and oxygen
How about new stuff on planets and comets? Astronomers have discovered compounds in the atmospheres of the giant planets Jupiter, Saturn, Uranus and Neptune like silane (silicon-hydrogen), arsine (arsenic-hydrogen) and phosphine (phosphorus-hydrogen) that don’t exist naturally on Earth. Humans have created all three in the lab and put them to good use in various industries including the manufacture of semi-conductors.
Helium, the gas that floats our balloons, was first discovered in the spectrum of the sun by French astronomer Pierre Janssen in during a solar eclipse in 1868. Scientists finally found it on Earth in 1895. Click to learn the helium story. Credit: Bob King
And then there’s Brownleeite, a manganese silicide found in 2003 in a dust particle shed by comet 26P/Grigg-Skjellerup. Moving beyond the solar system, astronomers see unusual long-chained carbon molecules in space that couldn’t form on Earth because oxygen would tear them apart. Space is their safe haven.
So, Earth is the location in the Universe where you’ll find more exotic elements than anywhere else. Thanks to human activity and the complicated molecules that wound together to form life, Earth’s the most exotic place in the universe.
Lyrid meteors will appear to radiate (red circle) from a point near the bright star Vega in the constellation Lyra. This map shows the sky facing southeast around 3:30 a.m. April 22 - around the time of maximum. Stellarium
Feeling a little meteor-starved lately? Me too. It’s been a meteor shower desert since the Quadrantids of early January. That’s about to change. This weekend brings the celestial version of April showers with the annual appearance of the Lyrids.
The Lyrids ding the bell at maximum strength this weekend April 21-22 (Sunday night-Monday morning in the Americas) hurtling meteors at the modest rate of 10-20 per hour from a point in the sky not far from bright Vega in the constellation Lyra. While some showers spread their meteor crumbs over several days, the Lyrids’ peak activity lasts less than a day. The western hemisphere – particularly the western half of North America – is favored this year.
A Lyrid meteor captured by NASA astronaut Don Pettit out the window of the International Space Station on April 21, 2012. The lights of Florida are visible to the right of the meteor. Click to enlarge. Credit: NASA
There will be a small price to pay for the show. The Lyrid radiant, the point in the sky from which the showers members radiate, rises in the east rather late – around 10:30 p.m. local time. Then there’s the bright gibbous moon, which has a habit of drowning out fainter stars and meteors alike. That makes the best time for viewing the shower after moonset or around 4 a.m. Monday morning. Since dawn begins about 5, you’ll have one good hour. That’s plenty of time to snag at least a few flaming motes of Comet Thatcher.
A bright fireball meteor in twilight. The Lyrids, like all meteor showers, offer up the occasional fireball among a mix of fainter meteors. Credit: John Chumack
Like most meteor showers, the Lyrids have a parent and single parents are the rule. For the Lyrids, it’s Comet Thatcher, discovered on April 5, 1861, a week before the start of the Civil War, by amateur astronomer A.E. Thatcher observing from New York City. Later it was found to be linked to the Lyrid meteor shower.
Each year in late April, Earth passes through centuries of dust shed by the comet’s tail. When bits of Thatcher flotsam strike the air some 60-70 miles high, they burn up in flashes of meteoric light. Comet tears.
The delicate, rarefied dust tail of Comer C/2012 K5 in Dec. 2012. If Earth happens to intersects a comet’s dusty orbit – as we do with Comet Thatcher every April – we witness a meteor shower. Credit: Michael Jaeger
All meteors are worthy of keeping an eye on, but bear in mind that the Lyrids are no Perseids, the famed summertime shower offering up to 60 meteors per hour under dark skies. But what they lack in numbers, they make up in reliability and surprise.
Records indicate that people have been watching the Lyrids for at least 2,600 years, the longest of any shower. Our oldest descriptions come from the Chinese who penned that “stars fell like rain” on March 16, 687 BC. Apparently the shower was more active in the past and has since evolved into a minor display. But there have been occasional surprises, and that’s what keeps the Lyrids interesting.
Comet Thatcher circles the sun once every approxiimately 415 years. Each time it does, the comet leaves dust and small bits of ice and rock in a trail behind it. Sometimes it sheds more dust than others, creating denser filaments that can make for unexpectedly high numbers of Lyrid meteors when the Earth passes through. Not to scale. Illustration: Bob King
On April 20, 1803 a fire bell roused Richmond, Virginia residents from their beds to witness a similar rain of stars when up to 700 meteors per hour were seen. Other Lyrid outbursts occurred in 1922 (100 per hour), 1945 (100/hr), 1982 (90/hour). Last year’s peak hit 37 per hour from a dark sky site. Now and then, Earth encounters a thicker band of comet debris left behind by Comet Thatcher, suddenly increasing the meteor count by many times and just as suddenly dropping back to the usual 10-20 per hour.
So here’s the bottom line. Don’t expect a big blast, but do avail yourself of the leisurely pleasure of meteor watching and the possibility of seeing pieces of a comet that rounds the sun only every 415 years. Find a spot where artificial lights is at a minimum, dress warmly and head out around 3:30 a.m. Monday. Set up a comfortable lawn chair and have tea or coffee and a blanket at the ready. You’ll do well to face south or east. Now recline back to allow a fulsome view of the sky above and wait for a few well-deserved ooohs and aaahs.
Comet C/2011 L4 PANSTARRS on the evening of April 9, 2013 from Austria. Dust released when the sun vaporizes the comet's ice is pushed back by the pressure of sunlight to form the tail. Click to enlarge. Credit: Michael Jaeger
It’s falling out of the news but Comet PANSTARRS still lives! You can still see it in a clear sky near you with nothing more than a pair of binoculars. And thanks to guidance from the bright zigzag of Cassiopeia, it’s easier than ever to find. Would that we had had this star group to point up comet-ward in March when PANSTARRS was brightest!
The comet marches along through Cassiopeia the Queen in April. The map shows the evening sky facing northwest about 90 minutes after sunset. Comet positions are shown every 5 nights. Stellarium
Start looking about 75-90 minutes after sunset or the same amount of time before sunrise. Yes, the comet is visible now at both dusk and dawn. Currently it shines at about 4.5-5 magnitude and might still be faintly visible with the naked from a very dark sky location. In 35-50mm binoculars it will look like a faint, fuzzy streak of light with a brighter head. Telescopes still give a wonderful view of the bright nucleus and shapely tail.
While the northern U.S., Canada and Europe have good views of PANSTARRS at both dusk and dawn, sky watchers in the southern U.S. have their best views at dawn. This map shows the sky at the start of dawn facing northeast about 90 minutes before sunrise. Stellarium
The other night a student who helps run our local planetarium described it as looking like a “real comet” through the telescope, the way textbook and online photos had led him to anticipate. Binoculars or telescope will show a misty, plume-like tail, but wide-field, time-exposure photography reveals the comet’s unbelievably broad fan of dust.
Comet PANSTARRS moves along a steeply tilted orbit that takes it far above and below the plane of the planets. Right now it’s high above Earth’s north pole and we see its tail broadside. The comet takes about 106,000 years to complete an orbit around the sun. Credit: NASA/JPL/Bob King
The reason for this unusual appearance has much to do with perspective. PANSTARRS is sailing back into deep space directly above the plane of the planets. With the tail blown back by the pressure of sunlight, we look up and across a distance of more than 125 million miles (201 million km) to see it spread like a deck of cards across the constellation Cassiopeia.
Comet PANSTARRS a week ago when it passed near the Andromeda Galaxy (at left). Details: 300mm f/2.8, ISO 800 and 90-second exposure. Credit: Bob King
In the northern U.S., Cassiopeia is higher up in both morning and evening skies and easy to spot. Once you’ve found its familiar shape, focus your binoculars on the brightest star nearest the comet, and slowly work your way in its direction. Skywatchers in the northern U.S., Canada and Europe are favored because Cassiopeia is a northern constellation and higher up in the sky at both dusk and dawn. Observers in the southern U.S. will get their best views around the start of dawn.
Comet C/2011 L4 Panstarrs, taken from New Mexico Skies between on March 25, 2013 using an FSQ 10.6 and STL11K camera. 65 frames over 18 min each with an exposure time of 2.0 sec. The stars have been enhanced for effect. Credit and copyright: Joseph Brimacombe.
Get ready for an comet encounter of the extragalactic kind. In less than a week, Comet PANSTARRS will slide by the Andromeda Galaxy, the brightest galaxy visible in northern hemisphere skies. On and around that date, you’ll be able to see them both glowing softly together in late evening and early morning twilight.
The Andromeda Galaxy is the closest large galaxy to our Milky Way. It’s easily visible in binoculars in the constellation Andromeda. Credit: Adam Evans
Their apparent proximity if of course pure sleight of hand; the comet will be a mere 121 million miles (195 million km) from Earth on that date compared to Andromeda’s 2.5 billion light years. For what it’s worth, 121 million miles (195 million km) equates to 0.00002 light years. Let’s just say they’re WAY far apart in reality. Their juxtaposition will make for enjoyable binocular viewing as well as offer astrophotographers an opportunity to create a classic image.
Comet PANSTARRS on March 22 photographed with a 200mm lens at dusk on a motorized tracking platform. Credit: Bob King
Last night under the clearest of skies I easily found Comet C/2011 L4 PANSTARRS in the constellation Andromeda about 15 degrees above the horizon an hour after sunset. Twilight was still a factor as was the rising full moon. That’s probably why the comet remained at the very limit of naked eye vision. Binoculars – I use 10x50s – clearly showed the comet’s bright parabolic head and two degrees (four full diameters) of tail streaming up and to the right.
Comet PANSTARRS shown every three days as it moves across Andromeda, passing near the Andromeda Galaxy around April 3. You can use Cassiopeia to point you to Beta Andromedae and from there to the comet. The map shows the sky facing northwest about one hour after sunset. Comet and galaxy brightness are exaggerated for the sake of illustration. Stellarium
The comet has faded considerably since it first emerged into the evening twilight three weeks ago. Its head now shines around magnitude 3.5 and is noticeably fainter than the stars of the Big Dipper. As compensation, PANSTARRS is now easier to find, since it’s both higher up in the sky and near a string of moderately bright stars in the constellation Andromeda.
PANSTARRS treks northward through Andromeda en route to the W of Cassiopeia in the next two weeks. It won’t be long before the comet becomes circumpolar and remains visible all night long. The term refers to celestial objects that circle around the pole star without setting. The Big Dipper is the most familiar circumpolar constellation for much of the U.S. and Canada.
Comet PANSTARRS in the early dawn sky during the first part of April. Once again, you can use Cassiopeia to help get you there. Don’t forget binoculars! They’re now essential to seeing the comet. The map shows the sky facing northeast about 75 minutes before sunrise. Stellarium
On its journey to all-night visibility, PANSTARRS started pulling a double-shift this week. You can now see it both at dusk and at dawn. Although a bright moon will compromise the dawn view for a few days, you can watch for the comet low in the northeastern sky starting about hour and 15 minutes before sunrise. For the moment, it’s about the same altitude above the horizon during both morning and evening hours. Evening is still preferred only because the bright moon has finally departed the sky during the hour or so the comet is visible.
Jose Chambo’s photo of Comet C/2011 L4 PANSTARRS from Spain on March 15 reveals a broad dust tail and narrower red-tinted tail. The red tail may be from sodium atoms released by materials colliding with each other as they jet off the comet’s nucleus. Click image to see more photos. Credit: José J. Chambó
Through my 15-inch telescope last night, PANSTARRS’ head held a brilliant topaz gem – the false nucleus. This tiny ball of bright, fuzzy light contains the icy comet itself, hidden behind a fury of its own dust and vapor boiled off by the sun’s heat.
Here’s some additional images and videos of PANSTARRS that Universe Today has received from readers:
Zlatan Merakov created this timelapse from images he took on March 20 from Smolyan, Bulgaria.
The view of Comet PANSTARRS L4 on 03-22-2013 over Warrenton, Virginia. Modified Canon Rebel Xsi DSLR 30 second exposure, ISO 1600, University Optics 80mm F6 Refractor (600mm). Credit and copyright: John Chumack.Comet C/2011 Pan-STARRS over Gradara Castle in Italy. Credit and copyright: Niki Giada.
Multiple exposures of Comet PANSTARRS taken on March 19 were stacked to create this amazing image. The field of view is about 6 by 4 degrees. Details: Leica-Apo180mm lens at f/4. Click to enlarge. Credit: Michael Jaeger
Wow – what an image! Michael Jaeger’s photo of Comet C/2011 L4 PANSTARRS on March 19 resembles those taken by the orbiting Stereo-B spacecraft. Check out this video (and the one below) to see what I mean. Most observers using binoculars and telescopes are seeing the comet’s head, bright false nucleus and a single plume-like tail.
Michael Jaeger of Stixendorf, Austria has been shooting beautiful comet images since 1982. Credit: Michael Jaeger
Careful photography like Jaeger’s reveals so much more – two bright, broad dust tails and three shorter spikes. One of the dust tails peels off to the left of the comet’s head, the other extends upward feather-like before splitting into two separate streamers. There are also several narrow, spike-like tails due to various excited elements and gas emissions from the comet’s icy nucleus.
Video of Comet PANSTARRS made from pictures taken by NASA’s STEREO-B spacecraft on March 13, one of two spacecraft that orbit ahead and behind Earth monitoring solar activity on the sun’s farside.
Michael Jaeger of Austria has been shooting pictures of comets since 1982. His images always reveal details that entice visual observers to go out and look for more than what first meets the eye. Last night I got my first look at the comet through a telescope and was delighted at the sight of its smooth, luminous tail and brilliant yellow false-nucleus. The false nucleus is the bright spot visible in the center of the PANSTARRS’ head; in 10×50 binoculars it looks like a star. Through a telescope it’s a fuzzy, yellow pea. Buried deep within the false nucleus is the icy comet nucleus itself, vaporizing in the sun’s heat and shrouded by its own dust.
Comet PANSTARRS last night March 19, 2013 in the company of white pines. Details: 300mm lens, f/2.8, ISO 800 and 3-second exposure. Credit: Bob King
The comet has faded in the past week or two from 1st magnitude – equal to some of the brightest stars – to about magnitude 2.5 or somewhat fainter than the stars of the Big Dipper. In very clear skies, it was still dimly visible with the naked eye about 40 minutes after sunset low in the northwestern sky. I only knew where to look after first finding the comet in 10×50 binoculars. The tail points straight up and stretches nearly 2 degrees in length once the sky gets dark enough to increase contrast and before PANSTARRS sinks too low. I kept it in view for nearly an hour from a wind-whipped location north of Duluth, Minn.
The comet at 64x through a 15-inch (37cm) telescope on March 19, 2013. The pale yellow false nucleus highlights the smooth, curved tail. Illustration: Bob King
Through the telescope the nucleus blazed yellow from sunlit dust. Set inside the comet’s sleek, smooth head it reminded me of a lighthouse beacon shining through the mist. Gorgeous! The tail trailed bent back to the northeast with a slight arc. I highly recommend setting up your telescope for a look at PANSTARRS, if for no other reason than to see the beauty of the false-nucleus within the finger-like tail.
Use this map to find Comet PANSTARRS now through March 31. It depicts the sky facing west-northwest 30-40 minutes after sunset. The comet’s height remains fairly steady at about 10-14 degrees but it moves steadily northward (to the right). The yellow circles represent the sun’s position every 3 days. It also moves northward but more slowly. One fist equals about 10 degrees of sky. Created with Chris Marriott’s SkyMap software
You can use the chart to help you find the comet for the remainder of the month. It shows the comet’s position every 3 days now through March 31 from mid-northern latitudes, specially 42 degrees north (Chicago, Ill.). If you live in the northern U.S., the comet will be in approximately the same positions but slightly higher in the sky; in the southern U.S. it will be a little lower. Notice the “15 degree” altitude line. If you set the bottom of your fist flat on the horizon, the 15 degree line is a fist and a half above that level.
Time lapse video made by Patrick Cullis showing Comet PANSTARRS setting behind the Flatirons of Boulder, Col. on March 19. As you watch, notice how the comet appears against the sky background and the direction it moves toward the horizon – both clues to help you find it.
The map compensates for the sun rising later each night and shows the comet’s height above the horizon when the sun is 7.5 degrees below the horizon. 7.5 degrees corresponds to about 30 minutes after sunset. Notice that the sun moves northward (to the right) just like the comet does over the next couple weeks but more slowly.
A compass has two sets of markings. One shows the basic directions N, S, etc. Those directions are subdivided into degrees of azimuth seen in the outer ring. Credit: Wikipedia
See those yellow numbers along the map’s horizon? Those are compass bearings called azimuths. If you have a compass, dig it out and give it a look. Every compass is marked in degrees of azimuth. 270 degrees is due west, 285 degrees is a fist and a half to the right of due west, 315 degrees is exactly halfway between due west and due north. North can be either 360 degrees or 0 degrees. Azimuths are simple way to subdivide directions to make them more precise.
Comet PANSTARRS very low in the northwestern sky shortly before setting last night March 19. Details: 300mm lens, f2.8, ISO 3200 and about 4 seconds exposure. Credit: Bob King
The next time it’s clear, bring your binoculars and a compass (if needed) and find a location with a great view of the western sky preferably down to the horizon. Use the map along with the compass bearings to guide your eyes in the right direction. You can also use the sun’s position below the horizon to point you to the comet by angling up from the lingering glow at the sunset point. Remember to first focus your binoculars on the moon, cloud bank or star before attempting to find PANSTARRS. There’s nothing more frustrating than sweeping for a fuzzy comet with an out-of-focus instrument.
Find Arcturus easily by using the handle of the Big Dipper. This map shows the sky facing northeast around 9:30-10 p.m. local time in late March. Stellarium
Every star has a story but some are more curious than others. The star Arcturus has an electrifying story with a mysterious twist involving the 1933 World’s Fair.
If you step out on a clear night in mid-March and follow the curve of the Big Dipper’s handle toward the eastern horizon, you’ll come face to face with Arcturus, the 4th brightest star in the sky. Pale orange and fluttering in the low air like a candle in the breeze, Arcturus is a bellwether of spring. By late May it shines high in the south at the onset of night. For the moment, the star hunkers down in the east, sparking through tree branches and over neighborhood rooftops.
The name Arcturus comes from the ancient Greek word “arktos” for bear and means “Bear Watcher”. That’s easy to remember because he follows Ursa Major the Great Bear, the brightest part of which is the Big Dipper, across the spring sky.
Arcturus is 37 light years from Earth and classified as an orange giant star. It spans 25 times the sun’s diameter and shines 113 times more brightly.
It was another spring 80 years ago on May 27,1933, that the city of Chicago opened its Century of Progress Exposition as part of the World’s Fair highlighting progress in science and industry. 40 years prior in 1893 the city had hosted its first big fair, the World’s Columbian Exposition.
In the early 1930s astronomers estimated Arcturus’ distance at 40 light years. Edwin Frost, retired director of the Yerkes Observatory in Williams Bay, Wis., home to the world’s largest refracting telescope, hit upon the idea of using Arcturus to symbolically link both great fairs which were separated by a span of 40 years.
Poster from the Century of Progress Exposition also called the Chicago World’s Fair. Its theme was the significance of science and how it had bettered mankind. The event was celebrated on Chicago’s 100th anniversary. Credit: Wikipedia
At the time, the photocell, a device that produces an electric current when exposed to light, was all the rage. Clever entrepreneurs had figured out how to take advantage of light’s ability to knock electrons loose from atoms to open doors and count shoppers automatically. They’re still in wide use today from burglar alarms to toilets that magically flush when you step away.
Edwin Frost around the time he was director of Yerkes Observatory in Williams Bay, Wis. Credit: National Academy of Sciences
Technological innovation through scientific progress was the theme of the 1933 fair. What better way, thought Frost, to highlight the benefits of science and link both great events than by focusing the light of Arcturus onto a photocell and using the electric current generated to flip a switch that would turn on the lights at the fair’s opening.
Though we now know Arcturus is 37 light years away, at the time it was thought to be about 40. The light that left the star during the first world’s fair in 1893 would arrive just in time 40 years later to open the next. Arcturus was not only at the right distance but bright and easy to see during May at the fair’s opening. Could a more perfect marriage of poetry and science ever be arranged?
From left: Edwin B. Frost, Christian T. Elvey, staff, and Otto Struve, Yerkes director, examine a General Electric photoelectric relay and the photocell tube that will help activate the lights of the “Century of Progress,” thus opening the Chicago world fair of 1933. Courtesy Yerkes Observatory
On May 27, 1933 shortly before the appointed time, Century of Progress Fair president Rufus C. Dawes spoke to a crowd of some 30,000 people assembled in the courtyard at the Hall of Science:
“We recall the great Columbian Exposition of 1893. Never will its beauty be surpassed.
Never will there be held an exposition of more lasting value to this city. It was for Chicago a great triumph.”
Visitors throng the Hall of Science at the Chicago World’s Fair in 1933, site of the Arcturus lighting ceremony. Click to enlarge Credit: Century of Progress Records, 1927-1952, University of Illinois at Chicago Library (COP_17_0002_00023_027)
“We remind ourselves of that triumph tonight by taking rays of light that left the star Arcturus during the period of that exposition and which have traveled at the rate of 186,000 miles a second until at last they have reached us. We shall use these rays to put into operation the mysterious forces of electricity which will make light our grounds, decorate our buildings with brilliant colors, and move the machinery of the exposition.”
Above the speaker’s platform hung a large illuminated panel, the bottom half of which displayed a map of the eastern U.S. with the locations of the four observatories. The top half contained the instruments that completed the circuit from Arcturus to a searchlight in the Hall of Science.
When light beams from the star Arcturus were picked up by photoelectric tubes at four observatories, signals flashed on this display board on the rostrum of the Hall of Science to the show the audience. Click to enlarge. Credit: Century of Progress Records, 1927-1952, University of Illinois at Chicago Library (COP_17_0002_00023_016)
At 9:15 p.m. each of the four observatories borrowed bits of Arcturus’ light, focused them onto their respective photocells and sent the electric current by Western Union telegraph lines to the Chicago fairgrounds.
In the book Fair Management – The Story of a Century of Progress, author Lenox Lohr described what happened next. One of the speakers, probably Philip Fox, director of Chicago’s Adler Planetarium, stepped to the podium to issue the final instructions :
“Harvard, are you ready?”
“Yes.”
A red glow ran across the map from Cambridge to Chicago.
“Is Allegheny ready?”
“Ready.”
“Illinois ready?”
“Yes.”
“Yerkes?”
“Let’s go.”
The switch was thrown, and a searchlight at the top of the Hall of Science shot a great white beam across the sky.”
The crowd went bananas. It was such a huge hit, nearby Elgin Observatory was pressed into operation to light the fair in similar fashion every night for the remainder of the season.
The Hall of Science area at the fair along with the Arcturus sign (far left) and a group of people creating a large star shape on a stage. Click for large version. Credit: Century of Progress Records, 1927-1952, University of Illinois at Chicago Library (COP_17_0002_00023_017)
Harnessing a distant star for mankind’s benefit. We marvel at the 1933 fair promoters and astronomers for conceiving of this most ingenious way of linking past and present.
That would be the end of a wonderful story if it wasn’t for one Ralph Mansfield. Mansfield, a student at the time at the University of Chicago, worked as a guide at Chicago’s Alder Planetarium, which was also involved in the lighting ceremony. Before passing away in 2007, Mansfield shared the story of how he was the one to point the telescope at Arcturus and fire up the fairground lights.
The Adler Planetarium on Chicago’s Lake Michigan lakefront. Credit:Fritz Geller-Grimm
I learned this while reading an article by Nathan B. Myron, PhD on the topic in which Mansfield sought to set the record straight. In his version, then-director of the Adler Planetarium, Philip Fox. was apprehensive about cloudy skies, so he arranged for Mansfield to set up a telescope in the balcony of the Hall of Science. As Fox delivered opening remarks, Mansfield used the Dipper’s Handle to find Arcturus in a lucky break in the clouds, and at the key moment, fed its light to the photocell. The spotlight fired up and the day was saved.
So which is the true story?
“It’s a bit of a mystery,” said Richard Dreiser, public information officer for Yerkes Observatory. “No one really knows absolutely.”
His sentiments were echoed by Bruce Stephenson, current curator at the Adler Planetarium: “The truth as far as we can ascertain it today is not really known. These things happened long ago.”
Most historical accounts indicate that four observatories participated, but Mansfield’s story remains. Will the real version please stand up?
These radar images of asteroid 2013 ET were obtained when the asteroid was about 693,000 miles from Earth. The images span 1.3 hours or about 1/3 or the asteroid's rotation rate. Click to enlarge. Credit: NASA/JPL-Caltech/GSSR
Another space rock sat pretty for NASA’s big dish photographer. The 70-meter (230-feet) Goldstone antenna zinged radio waves at 2013 ET on March 10 when the asteroid flew by Earth at 2.9 lunar distances or about 693,000 miles (1.1 million km).
By studying the returned echoes, astronomers pieced together 18 images of a rugged, irregular-shaped object about 130 feet (40 m) across. Radar measurements of an asteroid’s distance and speed nail down its orbit with great accuracy, enabling scientists to predict whether or not it might become a danger to the planet at a future date.
The Goldstone dish dish, based in the Mojave Desert near Barstow, Cal. is used for radar mapping of planets, comets, asteroids and the moon. Credit: NASA
It’s also the only way outside of a sending a spacecraft to the object of seeing a small asteroid’s shape and surface features. Most optical telescopes cannot resolve asteroids as anything more than points of light.
By convention, radar images appear “lit” from above. That’s the side closest to the antenna. As you examine a radar image from top to bottom, distance from the antenna increases and the asteroid fades. If the equator of the asteroid faces the antenna, it will appear brightly illuminated at the top of the image. If the antenna faces one of the poles, the pole will be on top and lit up. It takes a bit of getting used to.
Nine radar images of near-Earth asteroid 2007 PA8 obtained between by NASA’s 230-foot-wide (70-meter) Deep Space Network antenna. The part of the asteroid closest to the antenna is at top. Credit: NASA/JPL-Caltech
The asteroid’s width in the images depends on the asteroid’s rotation rate and the antenna’s perspective. If the antenna stares directly down over the equator and the asteroid rotates rapidly, the images will be stretched from Doppler-shifting of the returned radar echo.
Radio waves are a form of light just like the familiar colors of the rainbow. If radio light is moving toward you, its waves bunch together more tightly and appear slightly bluer than if they were at rest. Astronomers call this a Doppler shift or blueshift. If they’re moving away, the light waves get stretched and become “redshifted”.
Three views of asteroid 4179 Toutatis made in early Dec. 2012 by Goldstone. In all three, distance from the antenna increases from top to bottom and Doppler frequency increases toward the right, indicating Toutatis rotates from right to left, since that’s the side of the asteroid approaching the observer. Credit: NASA/JPL-Caltech
A slow-rotating asteroid will appear narrower to radar eyes, and if it doesn’t rotate at all, will show up as a “spike” of light. When the antenna happens to be point directly at a pole, the asteroid will appear to be rotating neither toward nor away from the observer and also look like a spike.
Most asteroids fall somewhere in between, and their radar portraits are close to their true shapes. Radar images show us surface textures, shape, size, rotation rate and surface features like craters. 2013 ET joins the ranks of numerous asteroids probed by radio waves from Earth as we try to grasp the complexity of our planetary neighborhood while hoping for we don’t stare down cosmic disaster anytime soon.
