Venus is Lonely. Very, Very Lonely


Venus is a hellish world. Although the planet is nearly the same size of Earth, that’s where the similarities end. Having said that, it does have an atmosphere, but it’s not the kind of atmosphere you would ever want to spend time breathing in. Composed of a dense carbon dioxide/nitrogen mix where clouds are made from sulphuric acid, you can forget about Venus as a tropical holiday destination. Even if you found a way to ‘breathe’ on Venus, you’d need to prepare yourself for the scorching 470°C surface temperatures and bone crushing pressures 100 times the pressure we are used to on Earth.

Doesn’t sound like a very nice place does it? Certainly an interesting world, providing us with invaluable science (after all, the reason for the extreme temperatures on Venus is due to a run-away greenhouse effect, it could help us understand the growing problems we are facing with our comparatively mild global warming woes), but an unlikely candidate for human colonization (unless we lived in the clouds).

Venus might not be a popular world for mankind to live on, but it doesn’t seem to be a popular world for natural satellites to orbit around either. It doesn’t have any moons, and astronomers are a little confused as to why this is the case. The only other planet without moons is the innermost terrestrial planet, Mercury. Every other planet in the Solar System has at least one natural satellite.

For hundreds of years, astronomers have been on the lookout for anything orbiting Venus but they’ve had little luck. However, some of the earliest observations of Venus appeared to indicate the presence satellites (in 1645, F. Fontana mentioned the possibility of a satellite discovery, followed by further observations in the late 1600’s and 1700’s). Since 1768, there have been no further reports of any satellite sightings. 1956 was the last published survey for Venusian satellites, using photographic plates, and that survey (published by Gerard Kuiper in 1961) drew up blanks for any satellites measuring over 2.5 km wide.

The lack of Venusian moons is puzzling, as a Venus-moon interacting mechanism has often been invoked as the reason why Venus has a retrograde spin (i.e. viewed from the ‘top’ of the Solar System plane, Venus has a clockwise rotation, whereas the rest of the planets, apart from Uranus — that spins on its side, bizarrely — have an anti-clockwise, or prograde, spin). Perhaps Venus once had a moon, but it has since been lost due to gravitational interactions with other Solar System bodies, or due to tidal instabilities, the innermost terrestrial planets collided with their large satellites a long time ago.

This is where Scott Sheppard from the Carnegie Institution of Washington and Chadwick Trujillo from the Gemini Observatory (Hawaii) step in. In a recent publication titled, “A Survey for Satellites of Venus,” Sheppard and Trujillo pick up where Kuiper left off, and carry out a systematic survey searching for any natural satellites around Venus. Only this time, by using the cutting-edge 6.5 meter telescope and IMACS wide-field CCD imager at Las Campanas observatory in Chile, they looked for objects only a few hundred meters in diameter.

The researchers scanned the interior of the Venusian ‘Hill Sphere’ to see if any undiscovered tiny moons were lurking. The Hill sphere is the volume of space surrounding a planetary body where natural satellites can orbit without being destabilized by the gravitational effects of the Sun. If there are any unforeseen moons, they should be found in stable orbits within the Hill sphere.

Sheppard and Trujillo have drawn blanks. Although a few errant asteroids were detected, no natural satellites down to a diameter of 600 meters were discovered. They surveyed 90% of the Venusian Hill sphere, and 99% of the inner Hill sphere (0.7rH) — the volume of space predicted to contain the stable orbits of natural satellites.

This new survey improves the non-detection of satellites down to a factor of 50 on previous studies, thereby proving Venus either, a) never possessed any satellites over 1km in diameter, or b) the orbits of past large satellites have become unstable and crashed into Venus or flung into space.

Either way, Venus remains alone, with only the ESA Venus Express for company

Source: A Survey for Satellites of Venus, Sheppard & Trujillo, 2009. arXiv:0906.2781v1 [astro-ph.EP]


Hubble and Atlantis Transit the Sun (Photo)

The Hubble Space Telescope and Shuttle Atlantis pass in front of the blank Sun. Can't see their silhouettes? Click on the image for the large version and look in the bottom-left-hand corner. That's no sunspot pair... (©Thierry Legault)
The Hubble Space Telescope and Shuttle Atlantis pass in front of the blank Sun. Can't see their silhouettes? Click on the image for the large version and look in the bottom-left-hand corner. That's no sunspot pair... (©Thierry Legault)

Thierry Legault is one highly skilled astrophotographer. The transit of the Hubble Space Telescope and Space Shuttle Atlantis took only 0.8 seconds to clear the disk of the Sun, so Legault rapidly took four pictures per second, starting his series of pictures two seconds before the pair were predicted to pass in front of the Sun.

STS-125 Atlantis and Hubble Solar Transit. The image was captured from Florida at 12:17pm EST on May 13th as the Shuttle approached the orbiting telescope at 600km from Earth (©Thierry Legault)
STS-125 Atlantis and Hubble Solar Transit. The image was captured from Florida at 12:17pm EST on May 13th as the Shuttle approached the orbiting telescope at 600km from Earth (©Thierry Legault)

In the image above, the 35 meter-long Atlantis is easily identifiable, but the tiny speck of the 13 meter-long Hubble isn’t so easy to define, but the result is superb. According to Legault’s website, this is the only picture of the STS-125 and the observatory, orbiting at an altitude of 600 km.

Back in July 2008, Astroengine reported on the transit of the International Space Station across the disk of the Sun. Fortunately, in both cases, the Sun’s face was blank, and no sunspots are prominent enough to ruin the view.


Sources: NASA on Flickr, Astrosurf

The Sun Has An Anti-Climax

The solar disk on May 11th: Is it? Are they? Not quite (SOHO)
The solar disk on May 11th: Is it? Are they? Not quite (SOHO)

Some recent solar articles are freaking out, proclaiming that the Sun is waiting to unleash it’s fury on the Earth (re: Warning: Sunspot cycle beginning to rise) or that it’s lowering its energy output, possibly kickstarting Maunder Minimum 2.0 (re: New Forecast Calls for Calmer Sun).

So which one is it? Is the Sun just biding its time, waiting for the perfect moment to fire a salvo of flares at us? Or will it remain quiet, well into Solar Cycle 24, impacting our planet like the Maunder Minimum did during the Little Ice Age from the 16th-19th century?

It’s funny actually, both the above articles are based on the same research, and yet two very different conclusions were drawn from the text.

On the one hand, the Sun is acting rather strange; it’s undergoing a sustained solar minimum, the longest period of low sunspot population for the best part of a century. On the other hand, when the Sun does get active, steadily growing to a peak in activity for the 2012-2013 predicted solar maximum, the resulting flares and coronal mass ejections (CMEs) could inflict $2 trillion in damages on global infrastructure (according to a recent study), leaving us to mop up the mess for a decade. It’s these two extremes that are causing such a stir, generating the attention-grabbing headlines.

However, I seriously doubt that we are facing another Little Ice Age and I am highly skeptical of the predictions that the 11 years of Cycle 24 are going to be overly violent. To be honest, we just don’t know. Considering we live so close to the Sun, we actually know very little about it; to even begin trying to predict what it’s going to do next remains problematic.

That said, once the Sun starts producing lost of sunspots, this means magnetic activity is on the rise and solar activity is increasing, so when I see sunspots rotate into view, I can’t help but be a little excited. Today, it happened, two active regions appeared on the disk of the Sun. Could this be the real start to the solar cycle?


Today’s image is a magnetic map of the sun. Two active regions are circled. Their polarity identifies them as members of new Solar Cycle 24, but they lack the dark cores required of true sunspots. So, in spite of these lively magnetic imprints, we must still say “the sun is blank–no sunspots.”

No sunspots, another blank disk day and therefore low magnetic activity still.

How dull.

In 1839, The Moon Looked Like This

The first photograph of the Moon (John W. Draper)
The first photograph of the Moon (John W. Draper)

This is the first ever photograph taken of the Moon. The first. 170 years ago!

I was directed to the image by Twitter friend LouisS and I felt compelled to post it on Much like the 1911 Martian canal post last month, this serves as a reminder about the heritage of modern astronomy that dates back not decades, but centuries.

The 1839 photograph was taken by British ex-pat John William, a chemistry professor in the New York University, using a silver platinum plate.

For more, check out “One Photo, One Story” »

The Space Station Flares, Again!

I don’t usually post two identical stories within a few days of one another, but when I saw this image on I had to comment on it. On Friday, I was captivated by the astounding astrophotography by Nicolas Biver as he tracked the space station with video camera and telescope, to capture some great detail of the manned outpost as it passed over France. With a bit of luck and a whole world of skill, Biver observed a bright space station flare.

Next up, it’s the turn of Martin Gembec. On May 2nd, he grabbed this superb trail as the station passed through the distinctive edge-on disk of our galaxy over the Czech Republic. What’s more, the station flared as its huge solar arrays reflected sunlight through Gembec’s ‘scope… right at the moment when the station travelled through the hazy starlit disk of the Milky Way.

The ISS flares as it passes through the Milky Way's disk (©Martin Gembec)
The ISS flares as it passes through the Milky Way's disk (©Martin Gembec)

We were watching a bright flyby of the space station when the ISS surprised us with a big flare in the Milky Way,” said Gembec. “At maximum, the ISS reached magnitude -8.”

A magnitude of -8 makes this flare a beast; that’s 25× brighter than Venus and 400× brighter than the star Sirius.

In the photo above, there is a rather ominous piece of kit attached to a boom reaching into the centre of the image. This is a reflection of Gembec’s Canon 30D camera (that took the picture as the ISS passed overhead) in an all-sky mirror. The mirror is in a concave shape to collect the starlight from the sky, bouncing the light into the camera lens. It acts much like a satellite dish; except it doesn’t bounce and focus radio waves into an antenna, the all-sky mirror reflects visible light and focuses it into the open camera shutter. As you can see, the results are visually stunning.

Source: Space Weather

Space Station Flare Captured On Film

I’ve been watching this short video clip over and over. It may only be two seconds long, but it is such a unique view of the space station that I find it mesmerizing. Each time the animated GIF loops, another detail seems to reveal itself.

The ISS flare, as observed by Nicolas Biver from Versailles, France, on April 28th (©Nicolas Biver)
The ISS flare, as observed by Nicolas Biver from Versailles, France, on April 28th (©Nicolas Biver)

It’s also kinda hypnotizing in a rhythmic way; the space station appears to turn and boost away into the black of space, but just before its massive solar arrays capture the sunlight, dazzling the observer with a flash.

Is it me, or are those solar panels reminiscent of the sails hoisted up the masts of canon-touting battleships before the age of iron-hulled vessels and steam-powered engines? These slightly fuzzy images could even be from the turn of the 20th Century, when one of the first movie cameras filmed a ship steering out of port.

Of course, this isn’t a wooden ocean-going ship, it’s the space station, in orbit. And the video was taken with a modern digital camera through a 16-inch Dobsonian telescope by a highly skilled amateur astronomer called Nicolas Biver from Versailles, France. The reason why the station appears to “turn” is because the perspective of the observer changes as the station flies overhead, he did a great job of tracking it.

On April 28th, Biver tracked the space station through his ‘scope. Whether it was intentional or not, he was fortunate to capture an intense flare as the space station’s solar panels reflected sunlight at his location. The resulting flare was much brighter than Venus (after the Moon, the station is the second brightest object in the night sky). Usually when I hear about observations of flares made by stuff in orbit, I usually think of Iridium flares that occur at predictable times and locations, providing a target for observers on the ground to capture a meteor-like streak across the sky. The Iridium satellite network provides a great chance for astronomers to see the reflected light when the angle between them, the satellite’s solar panels and Sun is just right.

My astronomer friend Tavi Greiner (who has just joined the Astrocast.TV team as host of Our Night Sky, be sure to check it out!) is very skilled at observing the Iridium flare-ups, and as can be seen in this image, those things are bright.

However, on the 28th, it was the space station’s turn to reflect some light for Nicolas Biver.

In March, Space Shuttle Discovery completed the construction of the ISS solar arrays during the STS-119 mission. Over a series of space walks, the solar array had its area boosted to 16,000 square feet. With this extra surface area, comes the potential for very bright flaring events.

For the chance to view the ISS and possible flaring, check out’s Simple Satellite Tracker.

Source: Space Weather

In 1911, Martians Were Building Canals

Martians Build Two Immense Canals In Two Years

On August 27th, 1911 the New York Times Sunday magazine ran an article entitled “Martians Build Two Immense Canals In Two Years”. Astronomer Percival Lowell had been studying the Red Planet and sketched what he saw, in this case, a growing complex of apparent canals on the Martian surface. There was even a nice little story that went along with this canal-building alien civilization theory. Lowell said, “The whole thing is wonderfully clear-cut,” that the Martian civilization was dying and they were building canals to reach the water ice in the Martian poles.

It turns out he was right about the water ice, but there’s no trace of this canal-building race on Mars… in fact there’s little trace of anything biological on the Red Planet. So apart from a few historic anecdotes, there’s still no life on Mars. The search continues.

Canals a thousand miles long and twenty miles wide are simply beyond our comprehension. Even though we are aware of the fact that … a rock which here weighs one hundred pounds would there only weigh thirty-eight pounds, engineering operations being in consequence less arduous than here, yet we can scarcely imagine the inhabitants of Mars capable of accomplishing this Herculean task within the short interval of two years. — Excerpt from the 1911 New York Times article.

Source: The Futility Closet (an awesome site)

Mystery Blob Detected 12.9 Billion Light Years Away

The Himiko object, the most massive object ever discovered in the early universe (M. Ouchi et al.)

Take a good look, this is one of the most mysterious, massive objects ever discovered in the cosmos. We don’t really know what it is, but this thing is huge, spanning 55,000 light years across (the approximate radius of our Milky Way). What makes this all the more intriguing is the fact that this object formed only 800 million years after the Big Bang and it is 10 times more massive than the next biggest object observed in the early Universe. But what is it?
Continue reading “Mystery Blob Detected 12.9 Billion Light Years Away”

Are Brown Dwarfs More Common Than We Thought?

A brown dwarf plus aurorae (NRAO)

In 2007, a very rare event was observed from Earth by several observers. An object passed in front of a star located near the centre of the Milky Way, magnifying its light. Gravitational lensing is not uncommon in itself (the phenomenon was predicted by Einstein in 1915), but if we consider what facilitated this rare “microlensing” event, things become rather interesting.
Continue reading “Are Brown Dwarfs More Common Than We Thought?”

Listen to Brian Cox on BBC Radio 4: A Tribute to Carl Sagan (Update)

Listen to Brian Cox’s Tribute to Carl Sagan – it is fantastic »

Dr. Carl Sagan with a model of the Viking lander (NASA)
Dr. Carl Sagan with a model of the Viking lander (NASA)

News just in from Gia Milinovich via Twitter:

Physicist and broadcaster Brian Cox presents a tribute to his science hero, the American astronomer Carl Sagan, the man who many people describe as the greatest populariser of science of all time. His landmark television series Cosmos was seen by more than 600 million people worldwide and inspired a generation of young scientists to regard the universe with wonder and awe. — Synopsis about Brian’s show on BBC Radio 4

I’m a huge fan of Brian’s work, he’s a fantastic and entertaining communicator of all things scientific, so this is the perfect tribute to legendary astronomer and presenter, Carl Sagan. I’ll be sure to tune in… with my late-morning coffee. According to Gia, Brian thinks this is the best show he’s done, so if that’s anything to go by, this is one event you cannot miss!

Catch the BBC Radio 4 stream at 8pm GMT (in the US, that’s midday PST or 3pm EST).

We are a way for the Cosmos to know itself.” –Carl Sagan