Mercury starts its best period of visibility in the evening sky for skywatchers at mid-northern latitudes this weekend. This map shows the sky facing northwest about 40 minutes after sundown. Bright Jupiter also provides a convenient sightline for locating Mercury. Stellarium
Don’t let furtive Mercury slip through your fingers this spring. The next two and a half weeks will be the best time this year for observers north of the tropics to spot the sun-hugging planet. If you’ve never seen Mercury, you might be surprised how bright it can be. This is especially true early in its apparition when the planet looks like a miniature ‘full moon’.
Mercury, like Venus, displays phases as it revolves around the sun as seen from Earth’s perspective outside Mercury’s orbit. Both Mercury and Venus appear largest when nearly lined up between Earth and sun at inferior conjunction. Planets not to scale and phases shown are approximate. Credit: Bob King
Both Venus and Mercury pass through phases identical to those of the moon. When between us and the sun, Mercury’s a thin crescent, when off to one side, a ‘half-moon’ and when on the far side of the sun, a full moon. This apparition of the planet is excellent because Mercury’s path it steeply tilted to the horizon in mid-spring.
We start the weekend with Mercury nearly full and brighter than the star Arcturus. Twilight tempers its radiance, but :
* Find a location with a wide open view to the northwest as far down to the horizon as possible.
* Click HERE to get your sunset time and begin looking for the planet about 30-40 minutes after sunset in the direction of the sunset afterglow.
* Reach your arm out to the northwestern horizon and look a little more than one vertically-held fist (10-12 degrees) above it for a singular, star-like object. Found it? Congratulations – that’s Mercury!
* No luck? Start with binoculars instead and sweep the bright sunset glow until you find Mercury. Once you know exactly where to look, lower the binoculars from your eyes and you should see the planet without optical aid. And before I forget – be sure to focus the binoculars on a distant object like a cloud or the moon before beginning your sweeps. I guarantee you won’t find Mercury if it’s out of focus.
Through a telescope, Mercury looks like a gibbous moon right now but its phase will lessen as it moves farther to the ‘left’ or east of the sun. Greatest eastern elongation happens on May 24. On and around that date the planet will be farthest from the sun, standing 12-14 degrees high 40 minutes after sundown from most mid-northern locales.
Mercury is even better placed on May 19 but fades and begins to drop back down toward the horizon late in the month. Stellarium
The planet fades in late May and become difficult to see by early June. Inferior conjunction, when Mercury passes between the Earth and sun, occurs on June 19. Unlike Venus, which remains brilliant right up through its crescent phase, Mercury loses so much reflective surface area as a crescent that it fades to magnitude +3. Its greater distance from Earth, lack of reflective clouds and smaller size can’t compete with closer, brighter and bigger Venus.
When a planet crosses the disk of the sun it’s called a transit. Mercury’s path across the solar disk is seen from the Solar and Heliospheric Observatory (SOHO) on November 8, 2006. Credit: NASA.
Mercury’s 7-degree inclined orbit means it typically glides well above or below the sun’s disk at inferior conjunction. But anywhere from 3 up to 13 years in either November or May the planet passes directly between the Earth and sun at inferior conjunction and we witness a transit. This last happened for U.S. observers on Nov. 8, 2006; the next transit occurs exactly two years from today on May 9, 2016. That event will be widely visible across the Americas, Western Europe and Africa. After having so much fun watching the June 2012 transit of VenusI can’t wait.
In our Solar System, astronomers often divide the planets into two groups — the inner planets and the outer planets. The inner planets are closer to the Sun and are smaller and rockier. The outer planets are further away, larger and made up mostly of gas.
The inner planets (in order of distance from the sun, closest to furthest) are Mercury, Venus, Earth and Mars. After an asteroid belt comes the outer planets, Jupiter, Saturn, Uranus and Neptune. The interesting thing is, in some other planetary systems discovered, the gas giants are actually quite close to the sun.
This makes predicting how our Solar System formed an interesting exercise for astronomers. Conventional wisdom is that the young Sun blew the gases into the outer fringes of the Solar System and that is why there are such large gas giants there. However, some extrasolar systems have “hot Jupiters” that orbit close to their Sun.
The Inner Planets:
The four inner planets are called terrestrial planets because their surfaces are solid (and, as the name implies, somewhat similar to Earth — although the term can be misleading because each of the four has vastly different environments). They’re made up mostly of heavy metals such as iron and nickel, and have either no moons or few moons. Below are brief descriptions of each of these planets based on this information from NASA.
Mercury: Mercury is the smallest planet in our Solar System and also the closest. It rotates slowly (59 Earth days) relative to the time it takes to rotate around the sun (88 days). The planet has no moons, but has a tenuous atmosphere (exosphere) containing oxygen, sodium, hydrogen, helium and potassium. The NASA MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) spacecraft is currently orbiting the planet.
The terrestrial planets of our Solar System at approximately relative sizes. From left, Mercury, Venus, Earth and Mars. Credit: Lunar and Planetary Institute
Venus: Venus was once considered a twin planet to Earth, until astronomers discovered its surface is at a lead-melting temperature of 900 degrees Fahrenheit (480 degrees Celsius). The planet is also a slow rotator, with a 243-day long Venusian day and an orbit around the sun at 225 days. Its atmosphere is thick and contains carbon dioxide and nitrogen. The planet has no rings or moons and is currently being visited by the European Space Agency’s Venus Express spacecraft.
Earth: Earth is the only planet with life as we know it, but astronomers have found some nearly Earth-sized planets outside of our solar system in what could be habitable regions of their respective stars. It contains an atmosphere of nitrogen and oxygen, and has one moon and no rings. Many spacecraft circle our planet to provide telecommunications, weather information and other services.
Mars: Mars is a planet under intense study because it shows signs of liquid water flowing on its surface in the ancient past. Today, however, its atmosphere is a wispy mix of carbon dioxide, nitrogen and argon. It has two tiny moons (Phobos and Deimos) and no rings. A Mars day is slightly longer than 24 Earth hours and it takes the planet about 687 Earth days to circle the Sun. There’s a small fleet of orbiters and rovers at Mars right now, including the large NASA Curiosity rover that landed in 2012.
The outer planets of our Solar System at approximately relative sizes. From left, Jupiter, Saturn, Uranus and Neptune. Credit: Lunar and Planetary Institute
The Outer Planets:
The outer planets (sometimes called Jovian planets or gas giants) are huge planets swaddled in gas. They all have rings and all of plenty of moons each. Despite their size, only two of them are visible without telescopes: Jupiter and Saturn. Uranus and Neptune were the first planets discovered since antiquity, and showed astronomers the solar system was bigger than previously thought. Below are brief descriptions of each of these planets based on this information from NASA.
Jupiter: Jupiter is the largest planet in our Solar System and spins very rapidly (10 Earth hours) relative to its orbit of the sun (12 Earth years). Its thick atmosphere is mostly made up of hydrogen and helium, perhaps surrounding a terrestrial core that is about Earth’s size. The planet has dozens of moons, some faint rings and a Great Red Spot — a raging storm happening for the past 400 years at least (since we were able to view it through telescopes). NASA’s Juno spacecraft is en route and will visit there in 2016.
Saturn: Saturn is best known for its prominent ring system — seven known rings with well-defined divisions and gaps between them. How the rings got there is one subject under investigation. It also has dozens of moons. Its atmosphere is mostly hydrogen and helium, and it also rotates quickly (10.7 Earth hours) relative to its time to circle the Sun (29 Earth years). Saturn is currently being visited by the Cassini spacecraft, which will fly closer to the planet’s rings in the coming years.
Near-infrared views of Uranus reveal its otherwise faint ring system, highlighting the extent to which it is tilted. Credit: Lawrence Sromovsky, (Univ. Wisconsin-Madison), Keck Observatory.
Uranus: Uranus was first discovered by William Herschel in 1781. The planet’s day takes about 17 Earth hours and one orbit around the Sun takes 84 Earth years. Its mass contains water, methane, ammonia, hydrogen and helium surrounding a rocky core. It has dozens of moons and a faint ring system. There are no spacecraft slated to visit Uranus right now; the last visitor was Voyager 2 in 1986.
Neptune: Neptune is a distant planet that contains water, ammmonia, methane, hydrogen and helium and a possible Earth-sized core. It has more than a dozen moons and six rings. The only spacecraft to ever visit it was NASA’s Voyager 2 in 1989.
To learn more about the planets and missions, check out these links:
A radar view of Venus taken by the Magellan spacecraft, with some gaps filled in by the Pioneer Venus orbiter. Credit: NASA/JPL
There are dozens upon dozens of moons in the Solar System, ranging from airless worlds like Earth’s Moon to those with an atmosphere (most notably, Saturn’s Titan). Jupiter and Saturn have many moons each, and even Mars has a couple of small asteroid-like ones. But what about Venus, the planet that for a while, astronomers thought about as Earth’s twin?
The answer is no moons at all. That’s right, Venus (and the planet Mercury) are the only two planets that don’t have a single natural moon orbiting them. Figuring out why is one question keeping astronomers busy as they study the Solar System.
Astronomers have three explanations about how planets get a moon or moons. Perhaps the moon was “captured” as it drifted by the planet, which is what some scientists think happened to Phobos and Deimos (near Mars). Maybe an object smashed into the planet and the fragments eventually coalesced into a moon, which is the leading theory for how Earth’s Moon came together. Or maybe moons arose from general accretion of matter as the solar system was formed, similar to how planets came together.
The International Space Station captured as it passed in front of the Moon on Dec. 6, 2013, as seen from Puerto Rico. Credit and copyright: Juan Gonzalez-Alicea.
Considering the amount of stuff flying around the Solar System early in its history, it’s quite surprising to some astronomers that Venus does not have a moon today. Perhaps, though, it had one in the distant past. In 2006, California Institute of Technology researchers Alex Alemi and David Stevenson presented at the American Astronomical Society’s division of planetary sciences meeting and said Venus could have been smacked by a large rock at least twice. (You can read the abstract here.)
“Most likely, Venus was slammed early on and gained a moon from the resulting debris. The satellite slowly spiraled away from the planet, due to tidal interactions, much the way our Moon is still slowly creeping away from Earth,” Sky and Telescope wrote of the research.
“However, after only about 10 million years Venus suffered another tremendous blow, according to the models. The second impact was opposite from the first in that it ‘reversed the planet’s spin,’ says Alemi. Venus’s new direction of rotation caused the body of the planet to absorb the moon’s orbital energy via tides, rather than adding to the moon’s orbital energy as before. So the moon spiraled inward until it collided and merged with Venus in a dramatic, fatal encounter.”
Venus as photographed by the Pioneer spacecraft in 1978. Some exoplanets may suffer the same fate as this scorched world. Credit: NASA/JPL/Caltech
There could be other explanations as well, however, which is part of why astronomers are so interested in revisiting this world. Figuring out the answer could teach us more about the solar system’s formation.
Artist's impression of the planets in our solar system, along with the Sun (at bottom). Credit: NASA
The eight planets in our solar system each occupy their own orbits around the Sun. They orbit the star in ellipses, which means their distance to the sun varies depending on where they are in their orbits. When they get closest to the Sun, it’s called perihelion, and when it’s farthest away, it’s called aphelion.
So to talk about how far the planets are from the sun is a difficult question, not only because their distances constantly change, but also because the spans are so immense — making it hard for a human to grasp. For this reason, astronomers often use a term called astronomical unit, representing the distance from the Earth to the Sun.
The table below (first created by Universe Today founder Fraser Cain in 2008) shows all the planets and their distance to the Sun, as well as how close these planets get to Earth.
Mercury:
Closest: 46 million km / 29 million miles (.307 AU)
Farthest: 70 million km / 43 million miles (.466 AU)
Average: 57 million km / 35 million miles (.387 AU)
Closest to Mercury from Earth: 77.3 million km / 48 million miles
Venus:
Closest: 107 million km / 66 million miles (.718 AU)
Farthest: 109 million km / 68 million miles (.728 AU)
Average: 108 million km / 67 million miles (.722 AU)
Closest to Venus from Earth: 40 million km / 25 million miles
The planet Venus, as imaged by the Magellan 10 mission. Credit: NASA/JPL
Earth:
Closest: 147 million km / 91 million miles (.98 AU)
Farthest: 152 million km / 94 million miles (1.01 AU)
Average: 150 million km / 93 million miles (1 AU)
Mars:
Closest: 205 million km / 127 million miles (1.38 AU)
Farthest: 249 million km / 155 million miles (1.66 AU)
Average: 228 million km / 142 million miles (1.52 AU)
Closest to Mars from Earth: 55 million km / 34 million miles
Jupiter:
Closest: 741 million km /460 million miles (4.95 AU)
Farthest: 817 million km / 508 million miles (5.46 AU)
Average: 779 million km / 484 million miles (5.20 AU)
Closest to Jupiter from Earth: 588 million km / 346 million miles
Artist’s impression of Jupiter and Io. Credit: NASA/JPL
Saturn:
Closest: 1.35 billion km / 839 million miles (9.05 AU)
Farthest: 1.51 billion km / 938 million miles (10.12 AU)
Average: 1.43 billion km / 889 million miles (9.58 AU)
Closest to Saturn from Earth: 1.2 billion km /746 million miles
Uranus:
Closest: 2.75 billion km / 1.71 billion miles (18.4 AU)
Farthest: 3.00 billion km / 1.86 billion miles (20.1 AU)
Average: 2.88 billion km / 1.79 billion miles (19.2 AU)
Closest to Uranus from Earth: 2.57 billion km / 1.6 billion miles
Neptune:
Closest: 4.45 billion km /2.77 billion miles (29.8 AU)
Farthest: 4.55 billion km / 2.83 billion miles (30.4 AU)
Average: 4.50 billion km / 2.8 billion miles (30.1 AU)
Closest to Neptune from Earth: 4.3 billion km / 2.7 billion miles
As a special bonus, we’ll include Pluto too, even though Pluto is not a planet anymore.
Uranus and Neptune, the Solar System’s ice giant planets. Credit: Wikipedia Commons
Pluto:
Closest: 4.44 billion km / 2.76 billion miles (29.7 AU)
Farthest: 7.38 billion km / 4.59 billion miles (49.3 AU)
Average: 5.91 billion km / 3.67 billion miles (39.5 AU)
Closest to Pluto from Earth: 4.28 billion km / 2.66 billion miles
To learn more:
Online resources demonstrating the scale of the Solar System:
Planets in our Solar system size comparison.
Largest to smallest are pictured left to right, top to bottom: Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Mercury. Via Wikimedia Commons.
If you’re interested in planets, the good news is there’s plenty of variety to choose from in our own Solar System. From the ringed beauty of Saturn, to the massive hulk of Jupiter, to the lead-melting temperatures on Venus, each planet in our solar system is unique — with its own environment and own story to tell about the history of our Solar System.
What also is amazing is the sheer size difference of planets. While humans think of Earth as a large planet, in reality it is dwarfed by the massive gas giants lurking at the outer edges of our Solar System. This article explores the planets in order of size, with a bit of context as to how they got that way.
A Short History of the Solar System:
No human was around 4.5 billion years ago when the Solar System was formed, so what we know about its birth comes from several sources: examining rocks on Earth and other places, looking at other solar systems in formation and doing computer models, among other methods. As more information comes in, some of our theories of the Solar System must change to suit the new evidence.
Today, scientists believe the Solar System began with a spinning gas and dust cloud. Gravitational attraction at its center eventually collapsed to form the Sun. Some theories say that the young Sun’s energy began pushing the lighter particles of gas away, while larger, more solid particles such as dust remained closer in.
Artist’s conception of a solar system in formation. Credit: NASA/FUSE/Lynette Cook
Over millions and millions of years, the gas and dust particles became attracted to each other by their mutual gravities and began to combine or crash. As larger balls of matter formed, they swept the smaller particles away and eventually cleared their orbits. That led to the birth of Earth and the other eight planets in our Solar System. Since much of the gas ended up in the outer parts of the system, this may explain why there are gas giants — although this presumption may not be true for other solar systems discovered in the universe.
Until the 1990s, scientists only knew of planets in our own Solar System and at that point accepted there were nine planets. As telescope technology improved, however, two things happened. Scientists discovered exoplanets, or planets that are outside of our solar system. This began with finding massive planets many times larger than Jupiter, and then eventually finding planets that are rocky — even a few that are close to Earth’s size itself.
The other change was finding worlds similar to Pluto, then considered the Solar System’s furthest planet, far out in our own Solar System. At first astronomers began treating these new worlds like planets, but as more information came in, the International Astronomical Union held a meeting to better figure out the definition.
Hubble image of Pluto and some of its moons, Charon, Nix and Hydra. Image Credit: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI), and the HST Pluto Companion Search Team
The result was redefining Pluto and worlds like it as a dwarf planet. This is the current IAU planet definition:
“A celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.”
Jupiter (69,911 km / 43,441 miles) – 1,120% the size of Earth
Saturn (58,232 km / 36,184 miles) – 945% the size of Earth
Uranus (25,362 km / 15,759 miles) – 400% the size of Earth
Neptune (24,622 km / 15,299 miles) – 388% the size of Earth
Earth (6,371 km / 3,959 miles)
Venus (6,052 km / 3,761 miles) – 95% the size of Earth
Mars (3,390 km / 2,460 miles) – 53% the size of Earth
Mercury (2,440 km / 1,516 miles) – 38% the size of Earth
Eight planets and a dwarf planet in our Solar System, approximately to scale. Pluto is a dwarf planet at far right. At far left is the Sun. The planets are, from left, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. Credit: Lunar and Planetary Institute
Jupiter is the behemoth of the Solar System and is believed to be responsible for influencing the path of smaller objects that drift by its massive bulk. Sometimes it will send comets or asteroids into the inner solar system, and sometimes it will divert those away.
Saturn, most famous for its rings, also hosts dozens of moons — including Titan, which has its own atmosphere. Joining it in the outer solar system are Uranus and Neptune, which both have atmospheres of hydrogen, helium and methane. Uranus also rotates opposite to other planets in the solar system.
The inner planets include Venus (once considered Earth’s twin, at least until its hot surface was discovered); Mars (a planet where liquid water could have flowed in the past); Mercury (which despite being close to the sun, has ice at its poles) and Earth, the only planet known so far to have life.
To learn more about the Solar System, check out these resources:
Have you heard the terrifying news that the Earth’s poles are going to flip? What does “flipping” mean? And if the Earth’s poles do flip, are we in any danger?
Have you heard the startling news that the Earth’s poles might flip? Perhaps in the response to a close pass from the mysterious Planet X? Are you imagining the entire Earth actually flipping over on its side or rotating upside down, possibly while Yakkity Sax plays in the background? When will this happen? Can this happen?
First, there’s no secret planet hurtling through the Solar System causing chaos and orbital disturbances. So could the Earth spontaneously physically flip over? Some planets have already been tilted and flipped.
Take a look at Uranus. Its orbital tilt is 98-degrees. We assume the planet started with the same tilt as the rest of the Solar System, and some event in the ancient past caused it to fall over. It could have collided with another planet, billions of years ago, or gravitational interactions with other giant planets pushed it over.
And then there’s Venus, its axial tilt is 177-degrees. That’s essentially upside down. Venus is turning in the opposite direction from every other planet in the Solar System. Standing on the surface of Venus, you would see the Sun rise in the West and set in the East. Astronomers don’t know why this happened, perhaps it was gravitational interactions or a collision with another planet.
To actually flip a planet off its axis would take an event so catastrophic that it would devastate the planet. Don’t worry, as far as we know, those kinds of events and interactions stopped happening billions of years ago.
That’s the good news. The Earth isn’t likely to just fall over, or get bashed on its side like an office tower under the might of Godzilla
Schematic illustration of Earth’s magnetic field. Credit/Copyright: Peter Reid
Now what about those magnetic poles. On Earth, they can and do reverse on a regular basis. The Earth is often shown like a giant bar magnet, with a north magnetic pole and a south magnetic pole. Over vast periods of time, the Earth’s north pole becomes its south pole, and vice versa. Geologists measure the magnetic configuration of iron particles in ancient lava flows. in one part of the lava flow, the particles oriented with one magnetic configuration, and then in another, the particles were reversed. It turns out the planet reverses its polarity every 450,000 years, and the last reversal happened about 780,000 years ago. Which means it could happen in the next few thousand years.
If the Earth’s poles did reverse, what would happen to us? If the magnetic field disappeared entirely, the planet would be bathed in radiation from the Sun, which would likely cause an increase in cancer. But the Earth’s atmosphere would still protect us from majority of radiation.
What about mass extinctions? Scientists have wondered if there’s a link between them and magnetic reversals.
Fortunately for us, there doesn’t seem to be any connection. Whenever geomagnetic reversals happened in the past, it didn’t devastate life on Earth. So don’t worry about it.
There is a pretty good chance it won’t happen in our lifetime, and maybe not for hundreds of thousands of years. And even if the Earth’s poles flip, it wouldn’t be the end of the world. You might need to take a sharpie to your compass though.
Comet C/2014 E2 Jacques photographed from Siding Spring Observatory on March 14, 2014. Credit: Rolando Ligustri
Congratulations to Cristovao Jacques and the SONEAR team! On March 13 they snared C/2014 E2 (Jacques) in CCD images taken with a 0.45-meter (17.7-inch) wide-field reflector at the SONEAR (Southern Observatory for Near Earth Asteroids Research) observatory near Oliveira, Brazil. A very preliminary orbit indicates its closest approach to the sun will occur on June 29 at a distance of 56 million miles followed two weeks later by a relatively close flyby of Venus of 0.09 a.u. or 8.4 million miles (13.5 million km). If a comet approached Earth this closely so soon after perihelion, it would be a magnificent sight. Of course, watching from Venus isn’t recommended. Even if we could withstand its extreme heat and pressure cooker atmosphere, the planet’s perpetual cloud cover guarantees overcast skies 24/7.
Comet Jacques travels across the deep southern sky in early spring as seen from mid-northern latitudes. Approximate positions are shown through April 4. Stellarium
It’s the team’s second comet discovery this year after turning up C/2014 A4 (SONEAR) in January. Comet Jacques has been tracking across northern Centaurus since discovery. Over the next few nights, it straddles the border with Hydra where it will be visible low in the southern sky around for northern hemisphere observers from about midnight to 2 a.m. If you live on a Caribbean island and points south your view will be even better.
Steven Tilley’s animation of Comet C/2014 E2 Jacques over 35 minutes on March 13, 2014
Comet Jacques exhibits a dense, fairly bright 2-arc-minute coma or cometary atmosphere with a short northward-pointing tail. Brightness estimates have been hard to come by, but it appears the comet may be around magnitude +11.5 – 12 or within range of an 8-inch (20-cm) or larger telescope. One thing’s for certain. In the coming weeks, E2 will be approaching both the Earth and the sun and brightening as it slowly gains altitude in the evening sky.
Another view of the comet on March 13 through a 0.5-meter (19.5-inch) telescope. Credit: Ernesto Guido, Nick Howes, Martino Nicolini
Shortly after perihelion, Comet Jacques will shine brightest at around magnitude +10-10.5 (though it could be brighter) and remain nearly this bright as it swings north from Orion into Perseus from mid-July to mid- August. Closest approach to Earth occurs on Aug. 29-30 at 54 million miles (87 million km). It will join Comet Oukameiden – predicted to reach binocular visibility in late August – to offer comet lovers much to look forward to as the summer wanes.
False colour composite of a rainbow-like feature known as a ‘glory’, seen on Venus on 24 July 2011. The image is composed of three images at ultraviolet, visible, and near-infrared wavelengths from the Venus Monitoring Camera. The images were taken 10 seconds apart and, due to the motion of the spacecraft, do not overlap perfectly. The glory is 1200 km across, as seen from the spacecraft, 6000 km away. It's the only glory ever seen on another planet. Credit: ESA/MPS/DLR/IDA.
Oh glory! A rainbow-like optical phenomenon known as a ‘glory’ has been imaged for the first time on another planet. It was seen in the atmosphere of our nearest neighbor, Venus by ESA’s Venus Express orbiter.
Rainbows and glories occur when sunlight shines on cloud droplets. While rainbows arch across the sky, glories appear as circular rings of colored concentric rings centered on a bright core.
Glory with aircraft shadow in the center. Via Wikimedia Commons.
Glories are only seen when the observer is situated directly between the Sun and the cloud particles that are reflecting sunlight. On Earth, they can often be seen with the naked eye from airplanes, or when looking down upon fog or water vapor, such as when climbing a mountain.
On Earth, the simple ingredients needed for a rainbow are sunlight and raindrops. On Venus, the droplets are likely made of sulfuric acid.
Three images showing the glory at ultraviolet (left,) visible (centre) and near-infrared (right) wavelengths as taken by the Venus Monitoring Camera. The feature was observed on 24 July 2011 and measures 1,200 km across, as seen from the spacecraft, 6,000 km away. Credit: ESA/MPS/DLR/IDA.
Seeing this glory was no accident: they made a calculated effort to image the clouds with the Sun directly behind the Venus Express spacecraft. The scientists were hoping to spot a glory in order to determine important characteristics of the cloud droplets.
Today, the team reported that they were successful. The glory in the images here was seen at the Venus cloud tops, 70 km above the planet’s surface, back on July 24, 2011. Their paper was just recently accepted for publication.
The glory was 1,200 km wide as seen from the spacecraft, 6,000 km away.
The Venus Express team deduced that from these observations, the cloud particles are estimated to be 1.2 micrometres across, roughly a fiftieth of the width of a human hair.
The fact that the glory is 1,200 km wide means that the particles at the cloud tops are uniform on this scale at least.
The variations of brightness of the rings of the observed glory is different than that expected from clouds of only sulphuric acid mixed with water, suggesting that other chemistry may be at play.
One idea is that the cause is the “UV-absorber,” an unknown atmospheric component responsible for mysterious dark markings seen in the cloud tops of Venus at ultraviolet wavelengths. More investigation is needed to draw a firm conclusion.
Scientists also think that it would be possible to see a rainbow — and perhaps even a glory — on Titan since the atmosphere on this moon of Saturn is likely filled with methane droplets.
Rise of Venus and the Milky Way in Singapore on Feb. 28, 2014. Credit and copyright: Justin Ng.
“My dream to capture the beautiful Milky Way galaxy in Singapore has finally come true this morning after the monsoon season is over,” said noted astrophotographer Justin Ng, who lives in this island country in South East Asia. Justin noted that since Singapore is known for its heavy light pollution, there are many people who believe it’s impossible to capture stars and the arc of the Milky Way under those conditions. Justin has been taking amazing deep sky and night sky photos for quite some time, but he said with this particular image he’s hoping to prove the naysayers wrong.
“Plus, I hope to inspire more astrophotographers residing in heavily light polluted city to try to capture these ‘impossible’ images,” Justin added.
UPDATE: Below is a new timelapse video from Justin Ng.
This is a single exposure shot of planet Venus and Milky Way Galaxy in Singapore. However, the light pollution near the horizon is also visible.
Justin has now created a timelapse of his Milky Way photography from the same night he took this image, and he says a timelapse like this never been attempted by any photographers in Singapore, this is is the first:
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.
