Venus reflected in the Pacific Ocean late this fall seen from the island of Maui, Hawaii. The planet is now quickly dropping toward the sun. Credit: Bob King
I put down down the snow shovel to give my back a rest yesterday evening and couldn’t believe what I saw. Or didn’t see. Where was Venus? I looked to the south above the tree line and the goddess was gone! Sweeping my gaze to the right I found her again much closer to the western horizon point and also much lower.
As Venus revolves around the sun interior to Earth’s orbit, we see it pass through phases just like the moon. Tonight it’s still to the east of the sun (left side) and visible in the evening sky. On Jan. 11 it passes through conjunction and then appears on the other side of the sun in the morning sky. Illustration: Bob King
As 2013 gives way to the new year, Venus winds up its evening presentation as it prepares to transition to the morning sky. Catch it while you can. Each passing night sees the planet dropping ever closer to the horizon as its apparent distance from the sun shrinks. On January 11 it will pass through inferior conjunction as it glides between Earth and sun. Come the 12th, Venus nudges into the dawn sky – don’t expect to see it with the naked eye until around midmonth, when it’s far enough from the sun to bust through the twilight glare.
Phases of Venus during 2004 photographed through a telescope. When very close to inferior conjunction (bottom right) the crescent is seen to extend fully around the planet. Credit: Statis Kalyva / Wikipedia
Though the planet is departing, don’t let it disappear without at least a glance through binoculars. As conjunction approaches, Venus gets as close (and as large) as it can get to Earth and displays a most attractive crescent phase. Even 7x binoculars will show its thinning sickle shortly at dusk. Tonight (Dec. 27) Venus measures nearly 1 arc minute in diameter or 1/30 the width of the full moon and shines brightly at magnitude -4.5.
Venus is only about 12 degrees high in the southwestern sky some 20 minutes after sunset this evening Dec. 27. Stellarium
As the planet drops ever lower, the crescent grows both larger and thinner. A few days before conjunction, a telescope will show it extending beyond the usual 180-degree arc as sunlight beaming from behind Venus is scattered by the planet’s thick cloudy atmosphere.
When the air is transparent and seeing steady, amateur astronomers have photographed and observed the crescent wrapping a full 360 degrees around the planet’s disk – a sight quite unlike anything else in the sky.
Before Venus departs the evening sky, watch for it to pair up with a very thin crescent moon shortly after sunset on Jan. 2, 2014. Stellarium
In the coming week, watch for Venus starting about 15 minutes after sunset low in the southwestern sky. With each day, the planet becomes slightly less conspicuous as it competes against the twilight glow.
After final farewells late next week, we’ll look forward in the new year to welcoming the goddess in her new guise as morning star.
We enjoy the light from the Sun during the day, and then the comforting glow of the Moon at night. But the light coming from the Moon is an illusion. As you know, you’re actually seeing the reflected light from the Sun, bouncing off the Moon which acts like a mirror. A really terrible mirror.
When astronauts walked on the surface, they reported that it was dark grey, the color of pavement. Because of its dark color and bumpy surface, it only reflects about 12% of the light that hits it. Additionally, the amount of light we get from the Moon depends on the point of its orbit.
During its first and last quarters, the Moon is half illuminated, but it’s only 8% as bright when it’s full. Just imagine the surface when its only partly illuminated. With the Sun at a steep angle, the mountains cast long shadows. This makes the lunar surface much darker than when it’s directly illuminated.
During the full Moon, it’s so bright that it obscures fainter objects in the night sky. Many astronomers put their telescopes away during this phase, and wait for it to go away. When the Moon is highly illuminated, it reflects so much light we can even see it during the day.
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The brightness of the daytime sky completely washes out the light from the stars, but the Moon is even brighter, and so we can can see it in the sky during the day. The Moon follows an elliptical orbit around the Earth, changing its distance and brightness quite a bit. When it is at its closest point, and it’s full, this is known as a supermoon. This Moon can be 20% brighter than normal.
You’ve probably experienced how the Moon can cast shadows. In fact, there are three objects in the sky that can cast shadows. The Sun, of course, the Moon… and Venus.
Venus is the next brightest object in the sky, after the Moon. It reflects 65% of the sunlight that hits it. Every few months, Venus reaches its brightest time – that’s when you can see your shadow. On a night with no Moon, head far away from city lights. Let your eyes adjust and watch as your hand casts a shadow on a white piece of paper, illuminated only by Venus.
One last thought on reflected light.We talked about how bad a mirror the Moon is, reflecting only 12% of the light that hits it. That’s nothing. Saturn’s moon Enceladus, on the other hand, reflects about 99% of the light that falls on it. If astronauts ever get the chance to walk on the surface of Enceladus, it’ll feel like freshly fallen snow.
The "pale blue dot" of Earth as seen from Cassini on July 19, 2013.
This summer, for the first time ever, the world was informed that its picture was going to be taken from nearly a billion miles away as the Cassini spacecraft captured images of Saturn in eclipse on July 19. On that day we were asked to take a moment and smile and wave at Saturn, from wherever we were, because the faint light from our planet would be captured by Cassini’s camera, shielded by Saturn from the harsh glare of the Sun.
A few preliminary images were released just a few days later showing the “pale blue dot” of Earth nestled within the glowing bands of Saturn’s rings. It was an amazing perspective of our planet, and we were promised that the full mosaic of Cassini images was being worked on and would be revealed in the fall.
Well, it’s fall, and here it is:
The full mosaic from the Cassini imaging team of Saturn on July 19, 2013… the “Day the Earth Smiled”
“After much work, the mosaic that marks that moment the inhabitants of Earth looked up and smiled at the sheer joy of being alive is finally here. In its combination of beauty and meaning, it is perhaps the most unusual image ever taken in the history of the space program.”
In this panorama of the Saturnian system, a view spanning 404,880 miles (651,591 km), we see the planet silhouetted against the light from the Sun. It’s a unique perspective that highlights the icy, reflective particles that make up its majestic rings and also allows our own planet to be seen, over 900 million miles distant. And it’s not just Earth that was captured, but the Moon, Venus, and Mars were caught in the shot too.
According to the description on the CICLOPS page, “Earth’s twin, Venus, appears as a bright white dot in the upper left quadrant of the mosaic… between the G and E rings. Mars also appears as a faint red dot embedded in the outer edge of the E ring, above and to the left of Venus.”
This was no simple point-and-click. Over 320 images were captured by Cassini on July 19 over a period of four hours, and this mosaic was assembled from 141 of those images. Because the spacecraft, Saturn, and its moons were all in constant motion during that time, affecting not only positions but also levels of illumination, imaging specialists had to adjust for that to create the single image you see above. So while all elements may not be precisely where they were at the same moment in time, the final result is no less stunning.
“This version was processed for balance and beauty,” it says in the description. (And I’ve no argument with that.)
See below for an annotated version showing the position of all visible objects, and read the full article on the CICLOPS page for an in-depth description of this gorgeous and historic image.
2013 Saturn mosaic, annotated version.
“I hope long into the future, when people look again at this image, they will recall the moment when, as crazy as it might have seemed, they were there, they were aware, and they smiled.”
All images credit NASA/JPL-Caltech/Space Science Institute
UPDATE 11/13: CICLOPS Director Carolyn Porco describes how this image was acquired and assembled in this interview video from the World Science Festival:
It’s amazing to think that for the majority of human history, we had almost no understanding about the Sun. We didn’t know what it was made of, how it formed, or how it produced energy. We didn’t know how big it was, and we didn’t know how far away it was.
We orbit the Sun at a distance of about 150 million kilometers. This number is actually an average, since we follow an elliptical path. At its closest point, the Earth gets to 147 million km, and at its most distant point, it’s 152 million km.
Distances in the Solar System are so vast that astronomers use this distance as a standard for measurement, and so the average distance from the Earth to the Sun is called an astronomical unit. Instead of saying that Pluto is 5.87 billion kilometers away from the Sun, astronomers say that it’s 39 astronomical units, or AUs.
You might be surprised to know that the distance from the Sun to the Earth was only determined within the last few hundred years. There were just too many variables. If astronomers knew how big it was, they could figure out how far away it was, or vice versa, but both of these numbers were mysteries.
Ancient astronomers, especially the Greeks, tried estimating the distance to the Sun in several different ways: measuring the length of shadows on Earth, or comparing the size of the Moon and its orbit to the Sun. Unfortunately, their estimates were off at least by a factor of 10.
The key to figuring out the distance to the Sun came from observing Venus as it passed directly in front of the Sun. This rare event, known as a Transit of Venus, happens only twice every 108 years. Once devised, the best opportunities for taking this precise measurement came during the Venus transits of 1761 and 1769. Astronomers were dispatched to remote corners of the globe to observe the precise moment when Venus began to move in front of the Sun, and when it had moved completely across the surface.
By comparing these measurements, astronomers could use geometry to calculate exactly how far away the Sun is. Their initial calculations put the distance at 24,000 times the radius of the Earth. Not bad considering our modern measurement of 23,455 times the radius of the Earth.
Modern astronomers can use radar and laser pulses to calculate the distance to objects in the Solar System. For example, they fire an intense beam of radio waves at a distant object, like Mercury, and then calculate how long it takes for the waves to bounce off the planet and return to Earth. Since the speed of light is well known, the return travel time tells you how far away the planet is.
Astronomy has truly helped us find our place in the Universe. It nice to be living in a time when many of these big mysteries have been solved. I don’t know about you, but I can’t wait to see what’s around the corner of the next discovery.
The crescent Moon and Venus as seen from São Paulo, Brazil on September 8, 2013. Credit and copyright: Ednilson Oliveira
Did you notice a bright “star” close to the Moon last night (September 8, 2013)? People around the world had the treat of seeing the waxing crescent Moon have the planet Venus snuggle up close… or in some places, the Moon actually passed in front of Venus, in what is known as an occultation. Also, on Saturday, the bright star Spica added to the scene.
Thanks to our readers from around the world for sharing their images and videos!
Moon and Venus conjunction over the Eternal Flame of the 9/11 Memorial located here in San Antonio, Texas. Credit and copyright: Adrian New.The Moon and Venus on September 8, 2013. Credit and copyright: Wes Schulstad.The waxing crescent Moon near Venus on the evening of Sunday, September 8, 2013, as seen from southern Alberta, Canada. Credit and copyright: Alan Dyer/Amazing Sky Photography.
Here’s a video showing the occultation of Venus by the Moon, photographed by Fabian Gonzalez.
The 12% waxing crescenet Moon and Venus on September 8, 2013 as seen from Shot in Kennesaw, Georgia. Credit and copyright: Stephen Rahn.The new Moon with Venus on its right. Taken from the dark sky preserve at the Nutwood Observatory in central Ontario, Cananda. Credit and copyright: Brian McGaffney.A close-up of September’s waxing crescent Moon with Venus on September 8, 2013. Credit and copyright: Tavi Greiner.A calm and peaceful moment on a beautiful beach, with a planetary alignment between planets, Saturn (in the top left corner), Venus and Spica star (in the center image), and the crescent Moon above the horizon, as seen on September 7, 2013. Credit and copyright: Miguel Claro.Conjunction of Saturn, Venus, and the 2.5 day old Moon on Saturday, September 7, 2013. Spica sneaks into the photo beneath Venus. Taken from Salem, Missouri. Credit and copyright: Joe Shuster, Lake County Astronomical Society.
Video of the occultation of Spica by the Moon on September 7, 2013 from Israel, taken by Gadi Eidelheit. Read more about at his website, VenusTransit.
Beautiful Moon & Venus as seen from Mumbai on 8th September 2013. Credit and copyright: Henna Khan.The crescent Moon and Venus as seen from central Illinois. Credit: Nancy Atkinson.
Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.
A close conjunction of Venus and the crescent Moon as seen on February 27th, 2009. (Photo by author).
Sky watchers worldwide are in for a treat Sunday evening September 8, 2013 as the waxing crescent Moon passes near the dazzling planet Venus. And for a select few, the Moon will actually pass in front of Venus, in what is known as an occultation.
The action has already started this week, as the Moon reached New phase earlier today at 7:36 AM EDT/11:36 UT. The appearance of the slim crescent Moon nearest to the September equinox marks the start of the Jewish New Year with the celebration of Rosh Hashanah, which this year began as early as it possibly can at sundown on September 4th. As per tradition, Rosh Hashanah formally begins when the sky is dark enough for three stars to be seen. The convention established by Hillel II in 363 A.D. uses the mean motion of the Moon to fix the start dates of the Jewish luni-solar calendar, which means that occasionally Rosh Hashanah can start a day early. This also occurred in 2002.
The New Moon has also been historically an opportune time for nighttime military operations to commence —Desert Storm in 1991 and the raid against Bin Laden in 2011 were both conducted under the darkness afforded by the absence of moonlight around a New Moon. It’s yet to be seen if planners looking to conduct airstrikes on Syria are planning on taking advantage of the same conditions to begin operations soon.
Tonight, you can see the +1st magnitude star Spica less than two degrees away from -4th magnitude Venus. This places Venus at 100 times brighter than Spica and visible before sunset if you know exactly where to look for it.
The brightest star in the constellation Virgo, Spica is 260 light years distant and on the short list of nearby stars that will eventually go supernova. Fortunately for us, Spica is well outside of the ~100 light year radius “kill zone”.
You might just be able to spy the Moon and the -1st magnitude planet Mercury low to the west at dusk for the first time for this lunation tonight or (more likely) Friday night. This is also a great time to check out LADEE’s future home as it departs for lunar orbit from Wallops Island in Virginia on Friday night.
Hey, LADEE sitting on the pad atop its Minotaur V rocket with the slim crescent Moon in the background at dusk Friday night would be a great money shot, I’m just sayin’…
This weekend will see the Moon increase in illumination and elevation above the western horizon each evening until Spica, Venus, and the waxing crescent Moon fit within a four degree circle on Sunday night. The Moon will be 12% illuminated, while Venus is currently at a gibbous phase and 72% lit.
Looking west from latitude 30 north Sunday night from the US east coast… note that Mercury and Saturn are in the picture as well! (Created by the author in Stellarium).
This will also present a good chance to see Venus during the daytime, using the nearby crescent Moon as a guide. This is a fun thing to try, and no gear is required! Though Venus may seem tough to find against the bright daytime sky, appearances are deceptive. With an albedo of 67% versus the Moon’s average of 14% Venus is actually brighter than the Moon per square arc second of size!
The Moon will also occult Spica on the evening of September 8th for observers in the Middle East and Europe right around sunset. Spica is one of four bright stars that the Moon can occult in the current epoch, along with Antares, Aldebaran, and Regulus. This is also part of a series of fine occultations of Spica by the Moon ongoing from 2012 to 2014.
Sundown on September 8th offers a special treat, as the 3-day old Moon passes less than a degree from Venus worldwide. The pair will fit easily into the field of view of binoculars or a telescope at low power and present an outstanding photo op.
And for observers based in Argentina and Chile, the Moon will actually occult Venus. Occultations are grand events, a split-second astronomical event in a universe that seems to usually move at a glacial pace. This particular occultation occurs for South American observers just before & after sunset.
The occultation of Venus by the Moon; the footprint over South America. (Credit: Occult 4.1.0.2).
We witnessed and recorded a similar pairing of Venus and the daytime Moon from the shores of our camp on Saint Froid Lake in northern Maine back in 2007:
Also, keep an eye out for a ghostly phenomenon known as the ashen light on the dark limb of the Moon. Also known as Earthshine, what you’re seeing is the reflection of sunlight off of the Earth illuminating the (cue Pink Floyd) dark side of the Moon. When the Moon is a crescent as seen from the Earth, the Earth is at gibbous phase as seen from the nearside of the Moon. Remember, the lunar farside and darkside are two different things! Earthshine can vary in brightness, based on the amount of cloud and snow cover present or absent on the Earth’s moonward side. My Farmer’s Almanac-consulting grandpappy would call ashen light the “Old Moon in the New Moon’s arms,” and reckon rain was a comin’…
Be sure to check out these astronomical goings on this weekend, and send those pics in to Universe Today!
Venus reflected in Boulder Lake north of Duluth, Minn. two nights ago. Credit: Bob King
Curious coincidences occur in the sky just as they do on Earth. Take tonight for instance. The moon is in gibbous phase or about 3/4 full – 78% to be exact – while Venus, which also undergoes phases identical to the moon, is likewise gibbous and 78% full.
That’s just cool. If you have telescope, focus on Venus low in the western sky just after sunset and see a perfect replica in miniature of tonight’s moon.
Look for Venus about a fist up in the west-southwest shortly after sunset. Stellarium
Be sure you’re out early as the planet is low to begin with and drops lower in the west with each passing minute. Provided the sky is haze-free, Venus isn’t difficult to spot even 5 minutes after sunset. Look about 10 degrees (one fist held at arm’s length) above the west-southwest horizon.
The moon and Venus are coincidentally in exactly the same phase tonight – 78% gibbous. Stellarium
The moon shows spectacular craters and mountains, but Venus hides its equally spectacular scenery of volcanic mountains, craters and cracked plains beneath a permanent cover of sulfur-dioxide-laced clouds. Clouds are excellent reflectors of sunlight. Not only is the planet brilliant because of them but looks as white as a shiny cue ball.
Venus’ changing position with relation to the Earth as it orbits around the sun causes it to exhibit phases like the moon. I’ve marked approximately where Venus is in mid-August. After gibbous, the planet will wane to half and then a crescent over the coming months as it catches up and passes the Earth. Illustration: Bob King
Tomorrow night the moon and Venus will go their own phase-y way, the moon fattening up toward full and Venus slowly slimming its waistline as it works its way toward the Earth. For now enjoy their temporary bond.
Over the past six years wind speeds in Venus' atmosphere have been steadily rising (ESA)
High-altitude winds on neighboring Venus have long been known to be quite speedy, whipping sulfuric-acid-laden clouds around the superheated planet at speeds well over 300 km/h (180 mph). And after over six years collecting data from orbit, ESA’s Venus Express has found that the winds there are steadily getting faster… and scientists really don’t know why.
Cloud structures in Venus’ atmosphere, seen by Venus Express’ Ultraviolet, Visible and Near-Infrared Mapping Spectrometer (VIRTIS) in 2007 (ESA)
By tracking the movements of distinct features in Venus’ cloud tops at an altitude of 70 km (43 miles) over a period of six years — which is 10 of Venus’ years — scientists have been able to monitor patterns in long-term global wind speeds.
What two separate studies have found is a rising trend in high-altitude wind speeds in a broad swath south of Venus’ equator, from around 300 km/h when Venus Express first entered orbit in 2006 to 400 km/h (250 mph) in 2012. That’s nearly double the wind speeds found in a category 4 hurricane here on Earth!
“This is an enormous increase in the already high wind speeds known in the atmosphere. Such a large variation has never before been observed on Venus, and we do not yet understand why this occurred,” said Igor Khatuntsev from the Space Research Institute in Moscow and lead author of a paper to be published in the journal Icarus.
Long-term studies based on tracking the motions of several hundred thousand cloud features, indicated here with arrows and ovals, reveal that the average wind speeds on Venus have increased from roughly 300 km/h to 400 km/h over the first six years of the mission. (Khatuntsev et al.)
A complementary Japanese-led study used a different tracking method to determine cloud motions, which arrived at similar results… as well as found other wind variations at lower altitudes in Venus’ southern hemisphere.
“Our analysis of cloud motions at low latitudes in the southern hemisphere showed that over the six years of study the velocity of the winds changed by up 70 km/h over a time scale of 255 Earth days – slightly longer than a year on Venus,” said Toru Kouyama from Japan’s Information Technology Research Institute. (Their results are to be published in the Journal of Geophysical Research.)
Both teams also identified daily wind speed variations on Venus, along with shifting wave patterns that suggest “upwelling motions in the morning at low latitudes and downwelling flow in the afternoon.” (via Cloud level winds from the Venus Express Monitoring Camera imaging, Khatuntsev et al.)
A day on Venus is longer than its year, as the planet takes 243 Earth days to complete a single rotation on its axis. Its atmosphere spins around it much more quickly than its surface rotates — a curious feature known as super-rotation.
“The atmospheric super-rotation of Venus is one of the great unexplained mysteries of the Solar System,” said ESA’s Venus Express Project Scientist Håkan Svedhem. “These results add more mystery to it, as Venus Express continues to surprise us with its ongoing observations of this dynamic, changing planet.”
Earth is the third planet from the Sun, and the climate here is just right for life. Here in our Solar System, there are planets both hotter and colder than Earth.
So… which one is the hottest?
You might think it’s Mercury, the planet closest to the Sun. Mercury orbits at a distance of only 58 million kilometers, travelling in a blast-furnace of scorching radiation. Its temperature can skyrocket to 700 Kelvin, or 426 degrees Celsius on the sunward side. In the shadows, temperatures plunge down to 80 Kelvin, which is -173 degrees Celsius
Mercury sure is hot, but Venus is hotter.
Venus imaged by Magellan Image Credit: NASA/JPLVenus is much further from the Sun, orbiting at a distance of more than 108 million kilometers. Average temperature there is a hellish 735 Kelvin, or 462 degrees Celsius – hot enough to melt lead.
Venus remains that same temperature no matter where you go on the planet. At the North Pole? 735 Kelvin. At night? 735 Kelvin. Daytime at the equator? You get the point.
So, why is Venus so much hotter than Mercury, even though it’s further away from the Sun? It’s all about the atmosphere.
Mercury is an airless world, not unlike the Moon. Venus, has a very thick atmosphere of CO2, which adds incredible pressure, and traps in the heat.
Atmosphere of Venus. Credit: ESAConsider our own planet. When you stand at sea level on Earth, you’re experiencing one atmosphere of pressure. But if you could stand on the surface of Venus – and trust me, you don’t want to – you’d experience ninety-two times as much atmospheric pressure. This is the same kind of pressure as being a kilometer underneath the surface of the ocean.
Venus also shows us what happens when carbon dioxide levels just keep on rising. Radiation from the Sun is absorbed by the planet, and the infrared heat emitted is trapped by the carbon dioxide, which creates a runaway greenhouse effect.
You might think a planet this hot with such extreme temperature and pressure, would be impossible to explore.
And if you did, you’d be wrong.
The Soviets sent a series of spacecraft called Venera, which parachuted down through the thick atmosphere and returned images from the surface of Venus. Although the first few missions were failures, this taught the Soviets just how hellish the Venusian environment really is. Surface of Venus by Venera.
Venera 13 made it down to the surface in nineteen-eighty-one and survived for one-hundred-and-twenty-seven minutes, sending back the first color pictures of Venus’ surface.
The hottest planet in our solar system is Venus,
When it comes to temperature, distance from the Sun matters, but it takes a backseat to wrapping a planet in a atmospheric blanket of carbon dioxide.
