Not many people get excited about a penumbral eclipse, but when it’s a deep one and the only lunar eclipse visible in North America this year, it’s worth a closer look. What’s more, this Friday’s eclipse happens during convenient, early-evening viewing hours. No getting up in the raw hours before dawn.
During a partial or total lunar eclipse, the full moon passes first through the Earth’s outer shadow, called the penumbra, before entering the dark, interior shadow or umbra. The penumbra is nowhere near as dark as the inner shadow because varying amounts of direct sunlight filter into it, diluting its duskiness.
To better understand this, picture yourself watching the eclipse from the center of the Moon’s disk (latitude 0°, longitude 0°). As you look past the Earth toward the Sun, you would see the Sun gradually covered or eclipsed by the Earth. Less sunlight would be available to illuminate the Moon, so your friends back on Earth would notice a gradual dimming of the Moon, very subtle at first but becoming more noticeable as the eclipse progressed.
As the Moon’s leading edge approached the penumbra-umbra border, the Sun would narrow to a glaring sliver along Earth’s limb for our lucky lunar observer. Back on Earth, we’d notice that the part of the Moon closest to the umbra looked strangely gray and dusky, but the entire lunar disk would still be plainly visible. That’s what we’ll see during Friday’s eclipse. The Moon will slide right up to the umbra and then roll by, never dipping its toes in its dark waters.
During a partial eclipse, the Moon keeps going into the umbra, where the Sun is completely blocked from view save for dash of red light refracted by the Earth’s atmosphere into what would otherwise be an inky black shadow. This eclipse, the Moon only flirts with the umbra.
Because the moon’s orbit is tilted about 5° from the plane of Earth’s orbit, it rarely lines up for a perfect bullseye total eclipse: Sun – Earth – Moon in a straight line in that order. Instead, the moon typically passes a little above or below (north or south) of the small, circle-shaped shadow cast by our planet, and no eclipse occurs. Or it clips the outer edge of the shadow and we see — you guessed it — a penumbral eclipse.
Earth’s shadow varies in size depending where you are in it. Standing on the ground during twilight, it can grow to cover the entire sky, but at the moon’s distance of 239,000 miles, the combined penumbra and umbra span just 2.5° of sky or about the width of your thumb held at arm’s length.
Because the Moon travels right up to the umbra during Friday’s eclipse, it will be well worth watching.The lower left or eastern half of the moon will appear obviously gray and blunted especially around maximum eclipse as it rises in the eastern sky that Friday evening over North and South America. I should mention here that the event is also visible from Europe, Africa, S. America and much of Asia.
For the U.S., the eastern half of the country gets the best views. Here are CSTand UTtimes for the different stages. To convert from CST, add an hour for Eastern, subtract one hour for Mountain and two hours for Pacific times. UT stands for Universal Time, which is essentially the same as Greenwich or “London” Time except when Daylight Saving Time is in effect:
Eclipse begins: 4:34 p.m. (22:34 p.m. UT) Maximum eclipse (moon deepest in shadow): 6:44 p.m. (00:43 UT Feb. 11) Eclipse ends: 8:53 p.m. (2:53 UT Feb. 11)
You can see that the eclipse plays out over more than 4 hours, though I don’t expect most of us will either be able or would want to devote that much time. Instead, give it an hour or so when the Moon is maximally in shadow from 6 to 7:30 p.m. CST; 7-8:30 EST; 5-6:30 p.m. MST and around moonrise Pacific time.
This should be a fine and obvious eclipse because around the time of maximum, the darkest part of the penumbra shades the dark, mare-rich northern hemisphere of the Moon. Dark plus dark equals extra dark! Good luck and clear skies!
Devious humans have given green lasers a bad name. Aiming a laser at an aircraft or the flight path of an aircraft is illegal according to a 2012 U.S. federal law. Jail time awaits offenders. Don’t point at a police officer either. To get a taste of the dark side of green lasers, check out these rap sheets.
But if you mind your manners, a green laser is one of the best tools available to amateur astronomers eager to share the wonders of the night sky with the public. There’s simply nothing better to point out constellations, comets, individual stars and satellites in the night sky. Amateurs love ’em! So does the public. Go to a star party and pop out the laser, and you’ll get everyone’s attention. There’s magic in being able to point out our favorite points of light with a beam of light.
First, let’s look at laser etiquette to ensure the safety of our fellow stargazers:
*Always gather the group around you first, raise the laser above the crowd and ask everyone to look up. Then turn on the beam and aim. That way no one will accidentally face into the light. This is crucial when aiming low above the horizon, where the beam, nearly horizontal, has a better chance of striking someone in the eye. Take extra precaution to make sure the group is close. The closer the gathering, the brighter and easier the beam will be to see. Viewers too far off to one side or another will see a weaker, less intense light.
*Green lasers often use AAA batteries and draw a good amount of power especially on chilly nights. You’ll only get a few minutes of operation if you leave it out in the cold. Store your laser in an inside pocket to keep it warm until you need it. Tuck it back in between pointing sessions. Have a fresh pair of batteries around and keep those in your pocket, too!
*If you see an airplane headed in your direction, avoid using the laser light for a couple minutes just to be on the safe side.
*Never give your laser to someone in the dark to “try out.” Especially a child! They won’t be familiar with its safe use.
* Store your laser in a safe place when not in use, so kids can’t accidentally find it.
The most common green laser available is rated at 5 milliwatts (mW), just adequate for night sky pointing. That said, be aware that brightness from one manufacturer to another can vary. Some 5mW pointers produce nearly as much light as a 30 mW model, practically a light saber! Others, like my first green laser, did the job on moonless nights, but proved too weak by first quarter phase. 30mW and 50mW are much better and significantly amp up the wow factor when you’re out with the crowd. They’re also much easier to see for larger groups and remain visible even in bright moonlight.
Back in olden days, 5 mW red and green lasers were as bright as they came, and the green ones were pricey. But nowadays, you can get powerful pointers in green, red, blue and violet. All will trace a visible beam across the night sky with green the brightest by far because our eyes are most sensitive to green light.
I should add that yellow lasers have also recently become available. Like green, they’re superb for long-distance applications, but prices — oh, my — will burn a hole in your wallet. How about 300 bucks! You can get a 5 mW green laser for $5-10 that’s similarly bright. No matter what kind of laser pen you buy, they all operate on the same principle: a laser diode, related to an LED (light-emitting diode), powered by AA batteries emits a narrow, coherent beam of light when switched on.
Coherent light is light of a single wavelength where all the crests and troughs (remember, light is a wave) are in lockstep with one another. Each crest precisely overlaps the next; each trough snugly fits within the other. Regular light contains a garden salad mix of every wavelength each vibrating out of stop, to its own drummer as it were. Because laser light is coherent, it stays focused over great distances, forming a narrow beam ideal for pointing.
Lasers are not only rated by power (milliwatts) but also the specific wavelength they emit. Green lasers beam light at 532 nanometers (nm), blue at 445 nm, violet at 405 nm, red at 650 nm and yellow at 589 nm. Green laser pointers generate their light from an infrared laser beam within the pen’s housing. Normally, any infrared light should be filtered from the final beam but in the majority of inexpensive laser pointers, it beams out right along with the green. We can’t see it, but concentrated infrared laser light poses an additional hazard when directed into the eyes. When you hear of lasers being used to pop balloons or light a match, it’s the leaky infrared that’s doing the popping. Yet another reason to use your laser with care!
Lower-powered laser pointers use AAA batteries. For instance, both my 5 mW and 55 mW green lasers use AAA batteries. Higher-powered pointers in the 5-watt range use a single #18650 (or 16340) 3.7 volt lithium ion rechargeable battery. You can either purchase these online (Orbitronics makes an excellent one for $12.99) or at your local Batteries Plus store. You’ll need a charger, too, which runs anywhere from about $8 for a single battery model to around $30 for a multiple battery version with different charging speeds. Be sure you get one with an LED light that will alert you when the batteries are done charging.
Whether sold in the U.S. or elsewhere, nearly every laser comes from China. We’ll talk about that in a minute, but if you purchase a laser that uses rechargeable batteries, beware of no-name chargers and off-brand batteries that lack safeguards. Some of these inexpensive batteries have been known to explode!
What to buy? I can’t speak to every firm that offers laser pointers, and there are many, but some of the more popular ones include:
I’ve bought from Optotronics, based in Colorado and the LED Shoppe, out of Hong Kong. I took a chance on the LED Shoppe’s lasers and have been pleasantly surprised at the low cost, free shipping and good customer service. While power ratings can vary from what the label reads, I’ve been especially pleased with both the 55 mW from Optotronics and the 5-watt (yes, FIVE WATTS) green and red pointers from the LED Shoppe. Their 50 mW green version does a great job, too. Just a disclaimer — I don’t work for and am not associated with either company.
Bottom line: If you’re looking for a effective pointer for public star parties, I recommend a 50 mW or higher green pointer. Anything in that range will provide a lovely bright beam you can use to literally dazzle your audience when sharing the beauty of the night. Before you make your decision, check your country or state’s laser use laws where for the U.S.orworldwide. If buying in the U.S., speak to the business owner if you have any questions.
Have a Merry Green, Red, Blue and Violet Christmas!
Don’t know much about history? How about the future? A new infographic by graphic designer Martin Vargic portrays both past and forthcoming events in our Universe, from the Big Bang to the death of our Sun. The graphic is color-coded and shows “significant events in cosmic and natural history.” It also illustrates how briefly humanity has been part of the scene.
Fun future events are when Earth’s day will become 25 hours long (Earth’s rotation is slowing down), and the amazingly distant time when the Solar System finally completes one orbit around the galactic core.
There are many ways to enjoy tomorrow night’s total lunar eclipse. First and foremost is to sit back and take in the slow splendor of the Moon entering and exiting Earth’s colorful shadow. You can also make pictures, observe it in a telescope or participate in a fun science project by eyeballing the Moon’s brightness and color. French astronomer Andre Danjon came up with a five-point scale back in the 1920s to characterize the appearance of the Moon during totality. The Danjon Scale couldn’t be simpler with just five “L values” from 0 to 4:
L=0: Very dark eclipse. Moon almost invisible, especially at mid-totality.
L=1: Dark Eclipse, gray or brownish in coloration. Details distinguishable only with difficulty.
L=2: Deep red or rust-colored eclipse. Very dark central shadow, while outer edge of umbra is relatively bright.
L=3: Brick-red eclipse. Umbral shadow usually has a bright or yellow rim.
L=4: Very bright copper-red or orange eclipse. Umbral shadow has a bluish, very bright rim.
The last few lunar eclipses have been bright with L values of 2 and 3. We won’t know how bright totality will be during the September 27-28 eclipse until we get there, but chances are it will be on the bright side. That’s where you come in. Brazilian amateur astronomers Alexandre Amorim and Helio Carvalho have worked together to create a downloadable Danjonmeterto make your own estimate. Just click the link with your cellphone or other device and it will instantly pop up on your screen.
On the night of the eclipse, hold the phone right up next to the moon during mid-eclipse and estimate its “L” value with your naked eye. Send that number and time of observation to Dr. Richard Keen at [email protected] For the sake of consistency with Danjon estimates made before mobile phones took over the planet, also compare the moon’s color with the written descriptions above before sending your final estimate.
Keen, an emeritus professor at the University of Colorado-Boulder Department of Atmospheric and Oceanic Sciences, has long studied how volcanic eruptions affect both the color of the eclipsed moon and the rate of global warming. Every eclipse presents another opportunity to gauge the current state of the atmosphere and in particular the dustiness of the stratosphere, the layer of air immediately above the ground-hugging troposphere. Much of the sunlight bent into Earth’s shadow cone (umbra) gets filtered through the stratosphere.
Volcanoes pump sulfur compounds and ash high into the atmosphere and sully the otherwise clean stratosphere with volcanic aerosols. These absorb both light and solar energy, a major reason why eclipses occurring after a major volcanic eruption can be exceptionally dark with L values of “0” and “1”.
One of the darkest in recent times occurred on December 30, 1982 after the spectacular spring eruption of Mexico’s El Chichon that hurled some 7 to 10 million tons of ash into the atmosphere. Sulfurous soot circulated the globe for weeks, absorbing sunlight and warming the stratosphere by 7°F (4°C).
Meanwhile, less sunlight reaching the Earth’s surface caused the northern hemisphere to cool by 0.4-0.6°C. The moon grew so ashen-black during totality that if you didn’t know where to look, you’d miss it.
Keen’s research focuses on how the clean, relatively dust-free stratosphere of recent years may be related to a rise in the rate of global warming compared to volcano-induced declines prior to 1996. Your simple observation will provide one more data point toward a better understanding of atmospheric processes and how they relate to climate change.
If you’d like to do a little more science during the eclipse, Keen suggests examining the moon’s color just after the beginning and before the end of totality to determine an ‘L’ value for the outer umbra. You can also determine the moon’s overall brightness or magnitude at mid-eclipse by comparing it to stars of known magnitude. The best way to do that is to reduce the moon down to approximately star-size by looking at it through the wrong end of a pair of 7-10x binoculars and compare it to the unreduced naked eye stars. Use this link for details on how it’s done along with the map I’ve created that has key stars and their magnitudes.
The table below includes eclipse events for four different time zones with emphasis on mid-eclipse, the time to make your observation. Good luck on Sunday’s science project and thanks for your participation!
Venus is HUGE right now but oh-so-skinny as it approaches inferior conjunction on August 15. Like crescents? You’ll never see a thinner and more elegant one, but first you’ll have to find it. Here’s how.
There’s only one drawback to enjoying Venus at its radically thinnest — it’s very close to the Sun and visible only during the daytime. A look at the diagram above reveals that as Venus and Earth draw closer, the planet also aligns with the Sun. At conjunction on August 15, it will pass 7.9° south of our star, appearing as an impossibly thin crescent in the solar glare. The sight is unique, a curved strand of incandescent wire burning in the blue.
If you’re patient and the air is steady, you might even glimpse the cusps of the illuminated crescent extending beyond their normal length to partially or even completely encircle Venus’s disk. These thread-like extensions become visible when the planet lies almost directly between us and the Sun. Sunlight scatters off the Venus’s dense atmosphere, causing it to glow faintly along the limb. One of the most remarkable sights in the sky, the sight is testament to the thickness of the planet’s airy envelope.
Today, only 1.7% of the planet is illuminated by the Sun, which shines some 11° to the northwest. The Venusian crescent spans 57 arc seconds from tip to tip, very close to 1 arc minute or 1/30 the width of the Full Moon. Come conjunction day August 15, those numbers will be 0.9% and 58 arc seconds. The angular resolution of the human eye is 1 minute, implying that the planet’s shape might be within grasp of someone with excellent eyesight under a clear, clean, cloudless sky. However — and this is a big however — a bright sky and nearby Sun make this practically impossible.
No worries though. Even 7x binoculars will nail it; the trick is finding Venus in the first place. For binocular users, hiding the Sun COMPLETELY behind a building, chimney, power pole or tree is essential. The goddess lurks dangerously close to our blindingly-bright star, so you must take every precaution to protect your eyes. Never allow direct sunlight into your glass. Never look directly at the Sun – even for a second – with your eyes or UV and infrared light will sear your retinas. You can use the map provided, which shows several locations of the planet at 1 p.m. CDT when it’s highest in the sky, to help you spot it.
If you’d like to see Venus on a different day or time, download a free sky-charting program like Stellarium or Cartes du Ciel. With Stellarium, open the Sky and Viewing Options menu (F4) and click the Light Pollution Level option down to “1” to show Venus in a daytime sky. Pick a viewing time, note Venus’s orientation with respect to the Sun (which you’ve hidden of course!) and look at that spot in the sky with binoculars. I’ll admit, it’s a challenging observation requiring haze-free skies, but be persistent.
A safer and more sure-fire way to track the planet down involves using those setting circles on your telescope mount most of us never bother with. First, find the celestial coordinates (right ascension and declination) of the Sun and Venus for the time you’d like to view. For example, let’s say we want to find Venus on August 10 at 2 p.m. Using your free software, you click on the Sun and Venus’s positions for that time of day to get their coordinates, in this case:
Venus – Right ascension 9h 42 minutes, declination +6°.
Sun – RA 9h 22 minutes, dec. +15° 30 minutes
Now subtract the two to get Venus’ offset from the Sun = 20 minutes east, 9.5° south.
Next, polar align your telescope using a compass and then cover the objective end with a safe mylar or glass solar filter. Center and sharply focus the Sun in the telescope. Now, loosen the RA lock and carefully offset the right ascension 20 minutes east using your setting circle, then re-lock. Do the same with declination, pointing the telescope 9.5° south of the Sun. If you’re polar alignment is reasonably good, when you remove the solar filter and look through the eyepiece, you should see Venus staring back at you from a blue sky. If you see nothing at first, nudge it a little this way and that to bring the planet into view.
Sometimes it takes me a couple tries, but I eventually stumble arrive on target. Obviously, you can also use this technique to spot Mercury and Jupiter in the daytime, too. By the way, don’t worry what the RA and Dec. read on your setting circles when you begin your hunt; only the offset’s important.
This year’s conjunction is one of the best for finding Venus in daylight because it’s relatively far from the Sun. With an orbital inclination of 3.2°, Venus’s position can range up to 8° north and south of the Earth’s orbital plane or ecliptic. Rarely does the planet cross the ecliptic at the same time as inferior conjunction. When it does, we experience a transit of Venus. Transits always come in pairs; the last set occurred in 2004 and 2012; the next will happen over 100 years from now in 2117 and 2125.
I hope you’re able to make the most of this opportunity while still respecting your tender retinas. Good luck!
Of course they’ve always been real worlds. They just never looked that way. We’ve only known of their existence since 2005, when astronomers with the Pluto Companion Search Team spotted them using the Hubble Space Telescope. Never more than faint points of light, each is now revealed as a distinct, if tiny, world.
“Before last week, Hydra was just a faint point of light, so it’s a surreal experience to see it become an actual place, as we see its shape and spot recognizable features on its surface for the first time,” said New Horizons mission science collaborator Ted Stryk.
Nix looks like a strawberry-flavored jelly bean, but that reddish region with its vaguely bulls-eye shape hints at a possible crater on this 26 miles (42 km) long by 22 miles (36 km) wide moon. Hydra, which measures 34 x 25 miles (55 x 40 km), displays two large craters, one tilted to face the Sun (top) and the other almost fully in shadow. Differences in brightness across Hydra suggest differences in surface composition.
Now we’ve seen three of Pluto’ family of five satellites. Expect images of Pluto’s most recently discovered moons, Styx and Kerberos, to be transmitted to Earth no later than mid-October.
All of Pluto’s satellites are believed to have been created in what’s now referred to as “The Big Whack”, a long-ago collision between Pluto and another planetary body. A similar scenario probably played out at Earth as well, leading to the formation of our own Moon. In Pluto’s case, most of the material pulled together to form Charon; the leftover chips became the smaller satellites. Their sizes are too small for self-gravity to crush them into spheres, hence their irregular shapes. The moons’ neatly circular orbits about Pluto suggest they formed together rather than being captured willy-nilly from the Kuiper Belt.
Update: This just in. Take a look at this new close-up of Pluto that features a newly discovered mountain range in southwestern Tombaugh Regio. Sure looks like ice flows. This is a complex little dwarf planet!
Below we have a special treat just in this morning (July 22) — mosaics and montages of Pluto and family created by Damian Peach from New Horizons images. Be sure to click to see the hi-res versions. Enjoy!
Countdown to discovery! Not since Voyager 2’s flyby of Neptune in 1989 have we flung a probe into the frozen outskirts of the Solar System. Speeding along at 30,800 miles per hour New Horizons will pierce the Pluto system like a smartly aimed arrow.
Edging within 7,800 miles of its surface at 7:49 a.m. EDT, the spacecraft’s long-range telescopic camera will resolve features as small as 230 feet (70 meters). Fourteen minutes later, it will zip within 17,930 miles of Charon as well as image Pluto’s four smaller satellites — Hydra, Styx, Nix and Kerberos.
After zooming past, the craft will turn to photograph Pluto eclipsing the Sun as it looks for the faint glow of rings or dust sheets illuminated by backlight. At the same time, sunlight reflecting off Charon will faintly illuminate Pluto’s backside. What could be more romantic than Charonshine?
Six other science instruments will build thermal maps of the Pluto-Charon pair, measure the composition of the surface and atmosphere and observe Pluto’s interaction with the solar wind. All of this will happen autopilot. It has to. There’s just no time to send a change instructions because of the nearly 9-hour lag in round-trip communications between Earth and probe.
Want to go along for the ride? Download and install NASA’s interactive app Eyes on Pluto and then click the launch button on the website. You’ll be shown several options including a live view and preview. Click preview and sit back to watch the next few days of the mission unfold before your eyes.
Like me, you’ve probably wondered how daylight on Pluto compares to that on Earth. From 3 billion miles away, the Sun’s too small to see as a disk with the naked eye but still wildly bright. With NASA’s Pluto Time, select your city on an interactive mapand get the time of day when the two are equal. For my city, daylight on Pluto equals the gentle light of early evening twilight six minutes after sunset. An ideal time for walking, but step lightly. In Pluto’s gentle gravity, you only weigh 1/15 as much as on Earth.
New Horizons is the first mission to the Kuiper Belt, a gigantic zone of icy bodies and mysterious small objects orbiting beyond Neptune. This region also is known as the “third” zone of our solar system, beyond the inner rocky planets and outer gas giants. Pluto is its most famous member, though not necessarily the largest. Eris, first observed in 2003, is nearly identical in size. It’s estimated there are hundreds of thousands of icy asteroids larger than 61 miles (100 km) across along with a trillion comets in the Belt, which begins at 30 a.u. (30 times Earth’s distance from the Sun) and reaches to 55 a.u.
Below you’ll find a schedule of events in Eastern Time. (Subtract one hour for Central, 2 hours for Mountain and 3 hours for Pacific). Keep in mind the probe will be busy shooting photos and gathering data during the flyby, so we’ll have to wait until Wednesday July 15 to see the the detailed close ups of Pluto and its moons. Even then, New Horizons’ recorders will be so jammed with data and images, it’ll take months to beam it all back to Earth.
Fasten your seat belts — we’re in for an exciting ride.
We’ll be reporting on results and sharing photos from the flyby here at Universe Today, but you’ll also want to check out NASA’s live coverage on NASA TV, its website and social media.
Monday, July 13
10:30 a.m. to noon – Media briefing on mission status and what to expect broadcast live on NASA TV
Tuesday, July 14
7:30 to 8 a.m. – Arrival at Pluto! Countdown program on NASA TV
At approximately 7:49 a.m., New Horizons is scheduled to be as close as the spacecraft will get to Pluto, approximately 7,800 miles (12,500 km) above the surface, after a journey of more than 9 years and 3 billion miles. For much of the day, New Horizons will be out of communication with mission control as it gathers data about Pluto and its moons.
The moment of closest approach will be marked during a live NASA TV broadcast that includes a countdown and discussion of what’s expected next as New Horizons makes its way past Pluto and potentially dangerous debris.
8 to 9 a.m. – Media briefing, image release on NASA TV
Wednesday, July 15
3 to 4 p.m. – Media Briefing: Seeing Pluto in a New Light; live on NASA TV and release of close-up images of Pluto’s surface and moons, along with initial science team reactions.
We’ll have the latest Pluto photos for you, but you can also check these excellent sites:
The year’s finest conjunction is upon us. Chances are you’ve been watching Venus and Jupiter at dusk for some time.
Like two lovers in a long courtship, they’ve been slowly approaching one another for the past several months and will finally reach their minimum separation of just over 1/4° (half a Full Moon diameter) Tuesday evening June 30.
Most of us thrill to see a single bright planet let alone the two brightest so close together. That’s what makes this a very special conjunction. Conjunctions are actually fairly common with a dozen or more planet-to-planet events a year and 7 or 8 Moon-planet match-ups a month. It’s easy to see why.
All eight planets travel the same celestial highway around the sky called the ecliptic but at different rates depending upon their distance from the Sun. Distant Saturn and Neptune travel more slowly than closer-in planets like Mercury and Mars. Over time, we see them lap one another in the sky, pairing up for a week or so and inspiring the gaze of those lucky enough to look up. After these brief trysts, the worlds part ways and move on to future engagements.
In many conjunctions, the planets or the Moon and planet are relatively far apart. They may catch the eye but aren’t exactly jaw-dropping events. The most striking conjunctions involve close pairings of the brightest planets. Occasionally, the Moon joins the fray, intensifying the beauty of the scene even more.
While moving planets are behind many conjunctions, they often don’t do it alone. Earth’s orbital motion around the Sun helps move things along. This week’s event is a perfect example. Venus is currently moving away from Jupiter in the sky but not quickly enough to avoid the encounter. Each night, its apparent distance from the Sun decreases by small increments and the planet loses altitude. Meanwhile, Jupiter’s moving away from Venus, traveling east toward Regulus as it orbits around the Sun.
So how can they possibly get together? Earth to the rescue! Every day, our planet travels some 1.6 million miles in our orbit, completing 584 million miles in one year. We see this movement reflected in the rising and setting times of the stars and planets.
Every night, the stars rise four minutes earlier than the night before. Over days and weeks, the minutes accumulate into hours. When stars rise earlier in the east, those in the west set earlier. In time, all stars and planets drift westward due to Earth’s revolution around the Sun.
It’s this seasonal drift that “pushes” Jupiter westward to eventually overtake a reluctant Venus. Despite appearances, in this particular conjunction, both planets are really fleeing one another!
We’re attuned to unusual planetary groupings just as our ancestors were. While they might have seen a planetary alignment as a portent of kingly succession or ill fortune in battle, we’re free to appreciate them for their sheer beauty. Not to say that some might still read a message or experience a personal revelation at the sight. There’s something in us that sees special meaning in celestial alignments. We’re good at sensing change in our environment, so we sit up and take notice when unusual sky events occur like eclipses, bright comets and close pairings of the Moon and planets.
You can watch the Jupiter-Venus conjunction several different ways. Naked eye of course is easiest. Just face west starting about an hour after sunset and drink it in. My mom, who’s almost 90, will be watching from her front step. Binoculars will add extra brilliance to the sight and perhaps show several moons of Jupiter.
If you have a telescope, I encourage you to point it at the planetary doublet. Even a small scope will let you see Jupiter’s two dark, horizontal stripes — the North and South Equatorial Belts — and several moons. Venus will appear as a pure white, thick crescent 32 arc seconds across virtually identical in apparent size to Jupiter. To tame Venus’ glare, start observing early when the sky is still flush with pale blue twilight. I think the best part will be seeing both planets in the same field of view even at moderate magnification — a rare sight!
To capture an image of these shiny baubles try using your cellphone. For many, that’s the only camera we have. First, find a pretty scene to frame the pair. Hold your phone rock-solid steady against a post or building and click away starting about an hour after sundown when the two planets have good contrast with the sky, but with light still about. If your pictures appear too dark or light, manually adjust the exposure. Here’s a youtube video on how to do it with an iPhone.
Point-and-shoot camera owners should place their camera on a tripod, adjust the ISO or sensitivity to 100, open the aperture or f/stop to its widest setting (f/2.8 or f/4), autofocus on the planets and expose from 5-10 seconds in mid-twilight or about 1 hour to 90 minutes after sunset. The low ISO is necessary to keep the images from turning grainy. High-end digital SLR cameras have no such limitations and can be used at ISO 1600 or higher. As always, review the back screen to make sure you’re exposing properly.
I’m not a harmonic convergence kind of guy, but I believe this week’s grand conjunction, visible from so many places on Earth, will stir a few souls and help us appreciate this life that much more.
An uncontrolled, chaotic landing. Stuck in the shadow of a cliff without energy-giving sunlight. Philae and team persevered. With just 60 hours of battery power, the lander drilled, hammered and gathered science data on the surface of comet 67P/Churyumov-Gerasimenko before going into hibernation. Here’s what we know.
Despite appearances, the comet’s hard as ice. The team responsible for the MUPUS (Multi-Purpose Sensors for Surface and Sub-Surface Science) instrument hammered a probe as hard as they could into 67P’s skin but only dug in a few millimeters:
“Although the power of the hammer was gradually increased, we were not able to go deep into the surface,” said Tilman Spohn from the DLR Institute of Planetary Research, who leads the research team. “If we compare the data with laboratory measurements, we think that the probe encountered a hard surface with strength comparable to that of solid ice,” he added. This shouldn’t be surprising, since ice is the main constituent of comets, but much of 67P/C-G appears blanketed in dust, leading some to believe the surface was softer and fluffier than what Philae found.
This finding was confirmed by the SESAME experiment (Surface Electrical, Seismic and Acoustic Monitoring Experiment) where the strength of the dust-covered ice directly under the lander was “surprisingly high” according to Klaus Seidensticker from the DLR Institute. Two other SESAME instruments measured low vaporization activity and a great deal of water ice under the lander.
As far as taking the comet’s temperature, the MUPUS thermal mapper worked during the descent and on all three touchdowns. At the final site, MUPUS recorded a temperature of –243°F (–153°C) near the floor of the lander’s balcony before the instrument was deployed. The sensors cooled by a further 10°C over a period of about a half hour:
“We think this is either due to radiative transfer of heat to the cold nearby wall seen in the CIVA images or because the probe had been pushed into a cold dust pile,” says Jörg Knollenberg, instrument scientist for MUPUS at DLR. After looking at both the temperature and hammer probe data, the Philae team’s preliminary take is that the upper layers of the comet’s surface are covered in dust 4-8 inches (10-20 cm), overlaying firm ice or ice and dust mixtures.
The ROLIS camera (ROsetta Lander Imaging System) took detailed photos during the first descent to the Agilkia landing site. Later, when Philae made its final touchdown, ROLIS snapped images of the surface at close range. These photos, which have yet to be published, were taken from a different point of view than the set of panorama photos already received from the CIVA camera system.
During Philae’s active time, Rosetta used the CONSERT (COmet Nucleus Sounding Experiment by Radio wave Transmission) instrument to beam a radio signal to the lander while they were on opposite sides of the comet’s nucleus. Philae then transmitted a second signal through the comet back to Rosetta. This was to be repeated 7,500 times for each orbit of Rosetta to build up a 3D image of 67P/C-G’s interior, an otherworldly “CAT scan” as it were. These measurements were being made even as Philae lapsed into hibernation. Deeper down the ice becomes more porous as revealed by measurements made by the orbiter.
The last of the 10 instruments on board the Philae lander to be activated was the SD2 (Sampling, Drilling and Distribution subsystem), designed to provide soil samples for the COSAC and PTOLEMY instruments. Scientists are certain the drill was activated and that all the steps to move a sample to the appropriate oven for baking were performed, but the data right now show no actual delivery according to a tweet this morning from Eric Hand, reporter at Science Magazine. COSAC worked as planned however and was able to “sniff” the comet’s rarified atmosphere to detect the first organic molecules. Research is underway to determine if the compounds are simple ones like methanol and ammonia or more complex ones like the amino acids.
Stephan Ulamec, Philae Lander manager, is confident that we’ll resume contact with Philae next spring when the Sun’s angle in the comet’s sky will have shifted to better illuminate the lander’s solar panels. The team managed to rotate the lander during the night of November 14-15, so that the largest solar panel is now aligned towards the Sun. One advantage of the shady site is that Philae isn’t as likely to overheat as 67P approaches the Sun en route to perihelion next year. Still, temperatures on the surface have to warm up before the battery can be recharged, and that won’t happen until next summer.
Let’s hang in there. This phoenix may rise from the cold dust again.
Here on Earth we enjoy the nitrogen-oxygen atmosphere we’ve all come to know and love with each of the approximately 24,000 breaths we take each day (not to mention the surprisingly comfortable 14.7 pounds per square inch of pressure it exerts on our bodies every moment.) But every breath we take would be impossible (or at least quickly prove to be deadly) on any of the other planets in our Solar System due to their specific compositions. The infographic above, created by UK chemistry teacher Andy Brunning for his blog Compound Interest, breaks down — graphically, that is; not chemically — the makeup of atmospheres for each of the planets. Very cool!
In addition to the main elements found in each planet’s atmosphere, Andy includes brief notes of some of the conditions present.
“Practically every other planet in our solar system can be considered to have an atmosphere, apart from perhaps the extremely thin, transient atmosphere of Mercury, with the compositions varying from planet to planet. Different conditions on different planets can also give rise to particular effects.”
– Andy Brunning, Compound Interest
And if you’re thinking “hey wait, what about Pluto?” don’t worry — Andy has included a sort of postscript graphic that breaks down Pluto’s on-again, off-again atmosphere as well. See this and more descriptions of the atmospheres of the planets on the Compound Interest blog here.