Astronomy & Science

Venus and Jupiter: Superclose Conjunction Before Dawn on August 18th

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Alan MacRobert, Senior Editor, Sky & Telescope
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Kelly Beatty, Senior Contributing Editor, Sky & Telescope

Note to editors/producers: Two publication-quality images are available; click on the thumbnails below to view or download high-resolution versions.
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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 August 18th, the two brightest planets come together in the predawn sky for their closest pairing since 2000.

On August 18th, the two brightest planets come together in the predawn sky for their closest visible pairing since 1999.
Credit: Sky & Telescope

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.

A Gradual Approach

The two planets' tight tango develops over several days. Venus is sinking in the predawn twilight, whereas Jupiter has only recently climbed high enough in the sky to be seen before sunrise. On August 15th, they'll be about 3° apart. Each morning thereafter, Jupiter rises a little higher and Venus sinks a little lower. The distance between them shrinks each day until the morning of the 18th, when they'll appear closest together.

After that, they'll gradually separate. By August 23rd, they'll be 5° apart (with Jupiter now higher), and on that date the planet duo will be joined by a razor-thin waning crescent Moon to their right.

Rarely do planets approach each other this closely. While these conjunctions of Venus and Jupiter occur about once a year on average, they vary considerably in visibility and separation. Some happen in daylight, while others are wide misses. These two planets have not paired this tightly while in good view in 15 years. The next Venus-Jupiter conjunction occurs on June 30, 2015, though their separation will not be quite as close.

Around August 18th, Venus will appear six times brighter than Jupiter, even though its diameter (7,521 miles) is less than 1⁄10 that of Jupiter (86,881 miles). That's because Venus is closer to Earth (150 million miles compared to Jupiter's 580 million miles), and also because Venus is much closer to the Sun than Jupiter is, so its clouds are lit much more intensely.

The View Up Close Sky & Telescope / Stellarium

This is how Venus and Jupiter will appear as seen through a low-power telescope (at a magnification of about 50×) on the morning of August 18th.
Credit: Sky & Telescope / Stellarium

Binoculars will make it easier to spot the two planets, especially as dawn twilight brightens. If your sky is still dark enough, use the binoculars to look for a loose concentration of faint stars (called the Beehive Cluster) positioned just above the paired planets.

Even the smallest backyard telescope will show a dramatic view. Both planets will fit with room to spare in the same low-power telescopic field of view. Blazing Venus mimics a tiny full Moon; Jupiter, appearing three times wider despite its great distance, is accompanied by its four brightest moons, neatly aligned in a row.

For more skywatching information and other astronomy news, visit or pick up Sky & Telescope, the essential magazine of astronomy since 1941. Sky Publishing (an F+W company) was founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, the original editors of Sky & Telescope magazine. In addition to Sky & Telescope and, the company publishes two annuals (Beautiful Universe and SkyWatch), as well as books, star atlases, posters, prints, globes, and other fine astronomy products.

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The First Planetary Nebula Spectrum

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Celebrate the anniversary of a revolutionary discovery by gathering with other astronomers to observe planetary nebulae in August's evening sky.

NGC 6543

This detailed Hubble Space Telescope image reveals intricate structures in the planetary nebulae NGC 6543, known as the Cat's Eye. William Huggins's 1864 observation of this nebula revealed that these structures are "luminous gas."
NASA / ESA / HEIC / Hubble Heritage Team (STScI /AURA)

August 29, 2014 will mark the 150th anniversary of Sir William Huggins’s first observation of the spectrum of a planetary nebula. He was the first to split apart the light coming from these stellar death shrouds, using a newfangled instrument he called a star-spectroscope.

These days we’re familiar with the fact that planetary nebulae are large, dusty clouds thrown off by dying stars. But astronomers didn’t know that when Huggins took his first observations. His first peek through the spectroscope was a watershed moment in the history of astronomy, comparable to Galileo’s use of a spyglass to catch his first glimpse of Jupiter’s moons.

Here’s how the London-based amateur astronomer famously described the event more than thirty years after the fact:

On the evening of the 29th of August, 1864, I directed the telescope for the first time to a planetary nebula in Draco [NGC 6543, popularly known today as the Cat’s Eye]. The reader may now be able to picture to himself to some extent the feeling of excited suspense, mingled with a degree of awe, with which, after a few moments of hesitation, I put my eye to the spectroscope. Was I not about to look into a secret place of creation? I looked into the spectroscope. No spectrum such as I expected! A single bright line only! At first, I suspected some displacement of the prism, and that I was looking at a reflection of the illuminated slit from one of its faces. This thought was scarcely more than momentary; then the true interpretation flashed upon me. The light of the nebula was monochromatic, and so, unlike any other light I had as yet subjected to prismatic examination, could not be extended out to form a complete spectrum. . . . The riddle of the nebulae was solved. The answer, which had come to us in the light itself, read: Not an aggregation of stars, but a luminous gas.

[W. Huggins, “The New Astronomy: A Personal Retrospect,” Nineteenth Century, 41 (1897), pp. 916-17.]

Before Huggins’s startling observations of the Cat’s Eye and several other planetary nebulae that August night in 1864 (see list below), astronomers had disagreed on whether these objects were groups of stars too distant to distinguish or diffuse, glowing matter. His spectroscopic results offered astronomers an entirely new — and previously undreamed of — way to answer that nagging question. Astronomers would never look at these perplexing fuzzy little objects in the same way again.

August 29th falls on a Friday this year, just four days after the new Moon. It’s a convenient time to take a look at the Cat’s Eye yourself and commemorate William Huggins’s historic observations.

Better yet, help a local amateur group or observatory organize a public “nebula” party in your area. Many groups appear in Sky & Telescope’s online listings, or you can search the web for other groups in your area. If you can’t find anything nearby, create your own event! You can use Huggins’s list to plan the evening’s agenda.

To learn more about Huggins’s groundbreaking observation and the pivotal role it played in the early development of astrophysics, see chapter 5 (“The Riddle of the Nebulae”) in my book, Unravelling Starlight: William and Margaret Huggins and the Rise of the New Astronomy (Cambridge University Press, 2011).

Planetary Nebulae Observed by William Huggins at his Tulse Hill Observatory on August 29, 1864.NGCOther catalog designations
const.nicknameappearance, mag., size
Huggins's description of pl. nebula and spectrum
6543GC 4373
H IV 37DracoCat's Eyegreenish disk
22" x 16""greenish blue"
"three lines"6572GC 4390
Σ6OphiuchusEmeraldvery bright bluish disk
15"x12""greenish blue"
"three lines"6826GC 4514
H IV 73CygnusBlinkingm+11
25""greenish blue"
"three lines"6818GC 4510
H IV 51SagittariusLittle Gemgreenish disk
m+1022""greenish blue"
"not as bright - two brighter lines seen, third only by glimpses"7009GC 4628
H IV 1AquariusSaturnbright bluish-green disk
m+825""greenish blue"
"three lines"6720GC 4447
80"x60""greenish blue"
"nebula bright, but spectrum fainter - one bright line, second not so bright, no sign of third"7662GC 4964
H IV 18AndromedaBlue Snowballbright bluish-green disk
"three lines"6853GC 4532
8'x5'"one line, others not seen"

Barbara Becker received her PhD in history of science from The Johns Hopkins University. Until her recent retirement, she taught history of science at the University of California, Irvine. She is the author of Unravelling Starlight: William and Margaret Huggins and the Rise of the New Astronomy (Cambridge University Press, 2011) and editor of the recently completed Selected Correspondence of William Huggins, 2 vols (Pickering and Chatto, 2014).

Want help finding these planetary nebulae and other celestial objects? Look no further than Sky & Telescope's beloved Pocket Sky Atlas.

The post The First Planetary Nebula Spectrum appeared first on Sky & Telescope.

Venus-Jupiter Spectacle Coming August 18th

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Here's your invitation to a spectacular close conjunction of the sky's two brightest planets, Venus and Jupiter, next Monday morning.

On August 18th, the two brightest planets come together in the predawn sky for their closest pairing since 2000.
Sky & Telescope diagram

Planets pair up plenty often, but rarely do they dance this closely. Venus and Jupiter will tango shortly before dawn on Monday, August 18th. They'll be separated by only 1⁄3° or less, making this year's very best conjunction. In fact, these two planets haven't paired so closely since 2000.

And it all happens right next door to Messier 44, the Beehive Cluster, in the constellation Cancer the Crab.

The two planets' dance will be brief. Venus is headed toward the eastern horizon and solar conjunction, while Jupiter only recently escaped the glare of the sun. With every morning, Jupiter rises a little higher in the east and Venus a little lower. As the two planets trot off in different directions, we'll see them slowly approach and separate.

Some pairings are close, others far

Venus and Jupiter rise over Lake Superior in Duluth, Minn. on June 30, 2012. Some pairings are close, others far.
Bob King

On August 14th, they'll be just 3.8° apart some 10° high in the northeastern sky 30 minutes before sunrise. To spot the duo, find a location with an open view of the eastern horizon.

You can start watching as early as an hour before sunrise, but the planets will be very low and possibly obscured by clouds or haze. Bring along a pair of binoculars just in case. Not sure when the sun rises? Click here and enter your city.

Each following morning, the distance between them shrinks by 1° (twice the diameter of the full Moon) until the 18th, when they'll be about 20 arcminutes (20′) apart, depending where you are in North America. You'll be able to cover both planets with the eraser of a pencil held at arm's length. That's what I call snug!

A view built for two

Here's how Venus and Jupiter will look on August 18th in a low-power telescope. Jupiter's moons (from left): Ganymede, Callisto, Io, and Europa.
Source: Stellarium

While conjunctions of Venus and Jupiter occur about once a year on average, they vary considerably in visibility and separation. Some happen in daylight, while others are wide misses.

Proximity makes for exciting conjunctions, and this event is the closest for North America since a similar morning pairing on April 23, 1998, almost an eternity ago. And there's more: The next Jupiter-Venus tango occurs less than a year from now, on June 30th, when they'll be just 20′ apart and conveniently placed in the western evening sky during twilight.

The View Through a Telescope

If you own a telescope, tote it out for a closer look. Both planets will fit with room to spare in the same field of view, a sight not to be missed. Blazing Venus mimics a tiny full moon just 10″ across; Jupiter's three times as wide. Will you be able to spot Jove's two 'tire track' equatorial belts and four moons?

Jupiter and Venus buzz the Beehive

Not only are Jupiter and Venus paired up on August 18th, but they're also in conjunction with the Beehive star cluster, M44.
Source: Chris Marriott's SkyMap

With twilight well underway, binoculars should help you track down the Beehive Cluster. I suspect you'll still see its brightest stars — look just to the left of Venus.

As close as this conjunction is for observers in North America, the planets will be even cozier for central European sky watchers. Closest approach of 13′ (0.2°) happens around 5h Universal Time as dawn's first light touches the rugged Alps.

Track Jupiter and its moons in the sky using Sky & Telescope's handy JupiterMoons app.

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Extreme Volcanoes on Jupiter’s Moon Io

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Even on Io, a world known for spouting off, the titanic volcanic eruption seen on August 29, 2013, was among the most powerful ever recorded there — or anywhere else in the solar system.

This time last year, a trio of volcanoes erupted so violently and powerfully that they would have been "breaking news" had they occurred anywhere on Earth. Fortunately, the towering fountains of fire were more than a half billion miles away, on Jupiter's moon Io.

Near-infrared views of Io, recorded with adaptive optics at the Gemini North telescope, track the evolution of a very powerful volcanic eruption that began August 29, 2013. Due to Io’s rapid rotation, each night shows a different area of the surface. The outburst waned in brightness on August 30th and September 1st, 3rd, and 10th.Katherine de Kleer / UC Berkeley / Gemini Observatory / AURA

Near-infrared views of Io, recorded with adaptive optics at the Gemini North telescope, track the evolution of a very powerful volcanic eruption that began August 29, 2013. Due to Io’s rapid rotation, each night shows a different area of the surface. The outburst waned in brightness on August 30th and September 1st, 3rd, and 10th.
Katherine de Kleer / UC Berkeley / Gemini Observatory / AURA

Imke de Pater (University of California, Berkeley) discovered the first two outbursts on August 15, 2013, using one of the 10-meter telescopes at Keck Observatory in Hawaii. The brighter one, at a previously known eruption site named Rarog Patera, was calculated to have covered 50 square miles with a lava flow 30 feet thick. The other, at Heno Patera, spewed molten rock over roughly 120 square miles. Both had abated by the time de Pater checked again five days later.

But the real fireworks were yet to come. A third, even brighter eruption flared to life on August 29th and was captured simultaneously with the nearby Gemini North telescope and NASA's Infrared Telescope Facility on Mauna Kea. The outburst was so intense and hot — even by Io's standards — that it probably involved a cluster of towering lava fountains spread over an estimated 32 square miles. The eruption's location, within a few degrees of 223° west, 29° north, is not associated with any previously recognized volcanic site.

According to Katherine de Kleer, a UC Berkeley graduate student, the August 29th event unleashed an estimated 20 terawatts of energy, making it at least 10,000 times more powerful than the lava fountains spewed during the 2010 eruptions of Eyjafjallajökull in Iceland.

These near-infrared observations kicked off a year-long scrutiny of Io by de Kleer, de Pater, and two collaborators. Two analyses of the August 2013 eruptions, one led by de Pater and the other by de Kleer, were just published online in the planetary-science journal Icarus.


The Jovian moon Io is a dynamic world where volcanoes erupt continuously, staining the surface with red and yellow allotropes of sulfur. Taken by the Galileo spacecraft in December 2000, these images reveal a fresh red ring (left), some 1,000 miles (1,500 km) across, encircling the volcano called Pele.

The Voyager 1 spacecraft first discovered volcanoes on Io during its 1979 flyby. Since then observations with spacecraft and ground-based telescopes have shown that this moon erupts nearly constantly, making it the most volcanic body in the solar system. About 150 sites are active now, and the total count is roughly 400. Researchers believe Io's eruptions mimic the kinds of volcanic activity that shaped the inner planets, including Earth, in the early solar system.

For details about last year's trio of powerful eruptions, see the press releases from UC Berkeley and Gemini Observatory.

Track Jupiter and Io in the sky using Sky & Telescope's handy JupiterMoons app.

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GRBs: A New Standard Candle?

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Astronomers might be on the brink of developing a new rung on the cosmic distance ladder.

An artist's conception of a gamma-ray burst.  European Southern Observatory

An artist's conception of a gamma-ray burst.
European Southern Observatory

Astronomy is a discipline pursued at unimaginable distances. And yet actually measuring the distance to a nearby exoplanet, or to a galaxy shining at us from the dark depths of the cosmos, seems almost futile.

One of the simplest methods is to use standard candles — objects with a known intrinsic brightness — and infer their distances based on how bright they appear to be when seen from Earth.

Astronomers have used Type 1a supernovae (SNe) as standard candles to great success. These explosions are the death cry of a dense white dwarf once it has collected too much additional matter. But we’re constantly on the search for new standard candles that could be an independent rung on the cosmic distance ladder: a tool for measuring distances to farther and farther galaxies.

Now, two new papers submitted to separate journals have independently found that gamma-ray burst supernovae just might be “standardizable.” And although both have yet to go through the rigorous peer-review process, outside experts are commending their work as solid starting points.

Gamma-ray Bursts as Standard Candles?

Roughly once a day the sky is lit up by a mysterious flash of energy. These events — gamma-ray bursts (or GRBs for short) — are among the most explosive and energetic events in the universe, sending out as much energy in a fraction of a second as our Sun will give off during its entire lifespan. Long GRBs (lasting more than 2 seconds) come from massive stars going supernova.

“When these stars undergo core collapse, they form a ‘central engine,’ which is expected to either be a rapidly rotating black hole that is surrounded by an accretion disk, or a neutron star with an exceptionally large magnetic field,” says Zach Cano (University of Iceland), who authored one of the two studies. “When the core collapses, the central engine creates a bipolar jet that pierces through the star, and at a large distance from the star, creates a burst of gamma rays, and later an afterglow.”

Type 1a SNe are easily used as standard candles because the amount of light we receive over time follows a specific pattern. The plots of this emission, known as light curves, have a characteristic shape, allowing astronomers to determine the explosion’s intrinsic brightness based on this shape alone.

But at first glance, the supernovae that create GRBs have irregular light curves.

So Cano and a second, independent team comprising Xui Li and Jens Hjorth (both from University of Copenhagen, Denmark) simultaneously dug a little deeper. Both teams looked at separate sets of eight GRB-SNe events in order to search for any consistency across the light curves.

They used two different approaches. Cano assumed that all GRB-SNe follow the behavior of the prototypical GRB-SN 98bw (a step that astronomers have assured me is valid). Li and Hjorth instead directly used the light curves of the GRB-SNe and looked for a correlation among them.

At the end of the day Cano found that the supernova’s luminosity correlated surprisingly well with the light curve’s width, while Li and Hjorth found that the luminosity correlated surprisingly well with the light curve’s decline rate.

“Before the two teams ... [submitted] their papers, it was not clear whether GRB-SNe could be standard candles,” says expert Steve Schulze (Pontifical Catholic University, Santiago, Chile). “The papers by Cano and Li and Hjorth provide compelling evidence that GRB-SNe are standardizable.” It is even more promising that two independent teams unknowingly supported each other’s results so well.

There are multiple advantages to using GRB-SNe as standard candles, and both teams are excited to move forward.

“It appears that GRB-SNe may be as good standard candles as Type 1a SNe,” says Hjorth. He explains that a major advantage is GRBs’ high redshift range. Astronomers have detected GRBs at redshifts as high as 8, when the universe was only 0.6 billion years old. Using GRBs to measure distances in the early universe would better enable astronomers to understand the universe’s mysterious expansion over time.

But the next step is actually using GRBs as standard candles. Cano thinks he has found a way to do this, but he’s not going public just yet. "Building upon this result, initial (unpublished) results indicate that GRB-SNe can be used in the same fashion as SNe Ia to constrain cosmological models,” says Cano. “The initial results also show that the universe is comprised of mostly dark energy, and with a Hubble constant between 60 to 70 km/s/Mpc," which matches calculations by members of ESA's Planck mission. "The results are preliminary, but the results are exceedingly encouraging."

Of course it’s important to stress that this is still a very young method with plenty of hurdles to jump through. Both teams will have to look at much larger data sets before the community will agree this approach works.


Z. Cano. “Gamma-ray Burst Supernovae as Standardizable Candles.” Posted to on July 9, 2014.

Xui Li and Jens Hjorth. “Light Curve Properties of Supernovae Associated With Gamma-ray Bursts.” Posted to on July 13, 2014.

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