Look west in twilight this Friday and Saturday (February 20th and 21st), and an unusual astronomical sight will await you.
Brilliant Venus and faint Mars will be paired remarkably close in the sky. And on Friday evening, the crescent Moon joins them in a tight bunch, a beautiful sight. On Saturday Venus and Mars appear even closer together, with the crescent Moon now looking down on them from above.
When it comes to “eyeball astronomy,” nothing is more satisfying than to see a pair of celestial objects appear close together in the sky, what astronomers call a conjunction. And 2015, notes Sky & Telescope’s longtime contributing editor Fred Schaaf, truly deserves to be called the “Year of the Conjunctions.” In January we watched Venus and Mercury come together in the evening twilight, and now comes a similarly close pairing of Venus and Mars. On Saturday they’ll appear 1/2° apart for viewers in North America. That’s about the width of a pencil held at arm’s length.
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ESA’s Venus Express has ended its eight-year mission after far exceeding its planned life. The spacecraft exhausted its propellant during a series of thruster burns to raise its orbit following the low-altitude aerobraking earlier this year.
Since its arrival at Venus in 2006, Venus Express had been on an elliptical 24‑hour orbit, traveling 66 000 km above the south pole at its furthest point and to within 200 km over the north pole on its closest approach, conducting a detailed study of the planet and its atmosphere.
However, after eight years in orbit and with propellant for its propulsion system running low, Venus Express was tasked in mid-2014 with a daring aerobraking campaign, during which it dipped progressively lower into the atmosphere on its closest approaches to the planet.
Normally, the spacecraft would perform routine thruster burns to ensure that it did not come too close to Venus and risk being lost in the atmosphere. But this unique adventure was aimed at achieving the opposite, namely reducing the altitude and allowing an exploration of previously uncharted regions of the atmosphere.
If you’re willing to rise before dawn on Monday, August 18th, you’ll be rewarded with the sight of the closest planet pairing of 2014 — and not just any planets, but the two brightest ones: Venus and Jupiter.
On that morning, these two worlds will form a striking “double star” low in the eastern sky. They will appear only 1⁄3° apart — a bit tighter than that in the eastern U.S. — close enough for both to be easily covered by the tip of your little finger at arm’s length.
You can start watching for Venus and Jupiter after they’ve cleared the east-northeastern horizon, as early as 80 minutes before sunrise, but make sure your view in that direction is wide open and unobstructed by trees or buildings. The best views will probably be from 60 to 30 minutes before sunrise, depending on how clear the air is, when the planets will be not quite so low.
As close as this conjunction is for early risers in North America, the pairing will be even tighter for skywatchers in Europe. From there, Venus and Jupiter will appear just 0.2° apart, about half the width of a pencil held at arm’s length.
When travelling above the clouds, airplane passengers sometimes witness a glory: a light phenomenon similar to a ring-shaped rainbow. Droplets in the clouds back-scattering the sunlight are responsible for this appearance. A team of scientists led by the Max Planck Institute for Solar System Research (MPS) in Göttingen have now fully imaged a glory on Venus – and thus for the first time on a planet other than Earth. The data was obtained by ESA’s space probe Venus Express. The data imply that the sulfuric acid in Venus’ cloud tops could additionally contain pure sulfur or iron chloride – and may help solve one of the oldest mysteries of Venus research.
The veil of clouds surrounding Venus is as beautiful as it is hostile to life. Sulfuric acid constitutes their main component. Together with the planet’s dense atmosphere composed mainly of carbon dioxide, this cloud cover causes Venus’ extreme greenhouse effect. Temperatures of more than 400 degrees Celsius are common on the planet’s surface. The exact composition of the creamy-yellow clouds is still unclear. Almost 90 years ago, ground-based observations had shown that these clouds “swallow” ultraviolet light of certain wavelengths. Sulfuric acid alone cannot be responsible for this effect.
NASA has released a natural-color image of Saturn from space, the first in which Saturn, its moons and rings, and Earth, Venus and Mars, all are visible.
The new panoramic mosaic of the majestic Saturn system taken by NASA’s Cassini spacecraft, which shows the view as it would be seen by human eyes, was unveiled at the Newseum in Washington on Tuesday.
Cassini’s imaging team processed 141 wide-angle images to create the panorama. The image sweeps 404,880 miles (651,591 kilometers) across Saturn and its inner ring system, including all of Saturn’s rings out to the E ring, which is Saturn’s second outermost ring. For perspective, the distance between Earth and our moon would fit comfortably inside the span of the E ring.
“In this one magnificent view, Cassini has delivered to us a universe of marvels,” said Carolyn Porco, Cassini’s imaging team lead at the Space Science Institute in Boulder, Colo. “And it did so on a day people all over the world, in unison, smiled in celebration at the sheer joy of being alive on a pale blue dot.”
Soon after the Sun dips below the western horizon on Sunday, September 8th, anyone looking in that direction will see a dramatic sight: a pretty crescent Moon paired closely with the dazzling planet Venus, the “Evening Star.”
“This is one you won’t want to miss,” says Alan MacRobert of Sky & Telescope magazine. “These are the two brightest objects in the nighttime sky.”
Start looking for the pair about 30 minutes after sunset. The farther south and east you are in North America, the closer they’ll appear. From locations along the East Coast, the they’ll be only about 1½° apart — about the width of your index finger at arm’s length. By the time darkness falls on the West Coast, the Moon will have edged slightly farther away.
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As the closest planet to Earth, Venus is a relatively easy object to observe. However, many mysteries remain, not least the super-rotation of Venus’ atmosphere, which enables high altitude winds to circle the planet in only four days. Now images of cloud features sent back by ESA’s Venus Express orbiter have revealed that these remarkably rapid winds are becoming even faster.
Similar in size to Earth, Venus has an extremely dense, carbon-dioxide-rich atmosphere and the planet’s surface is completely hidden by a blanket of bland, yellowish cloud. Only at ultraviolet wavelengths (and to a lesser extent in the infrared) do striking cloud streaks and individual cells emerge, due to the presence of some unknown UV absorber in the cloud deck.
By tracking the movements of these distinct cloud features, observers have been able to measure the super-hurricane-force winds that sweep around the planet at the cloud tops, some 70 km above the scorching volcanic plains.