Posted on by Fraser Cain

Clouds on Venus

Chemicals found in Venus' atmosphere. Image credit: ESA

The clouds of Venus are its defining characteristic. We can see the surface of Mars and Mercury, but the surface of Venus is shrouded by thick clouds. For most of history, astronomers had no idea what was beneath those clouds, and they imagined a tropical world with overgrown vegetation and constant rainfall. They couldn’t have been more wrong.

The climate of Venus isn’t tropical at all; it’s hellish. Temperatures on the surface of Venus approach 475 °C, and the atmospheric pressure is 93 times what you experience here on Earth. To experience that kind of pressure, you would need to swim down 1 km beneath the surface of the ocean. Venus’ atmosphere is made almost entirely of carbon dioxide, and not the oxygen/nitrogen mix we have here on Earth.

The clouds we see on Venus are made up of sulfur dioxide and drops of sulfuric acid. They reflect about 75% of the sunlight that falls on them, and are completely opaque. It’s these clouds that block our view to the surface of Venus. Beneath these clouds, only a fraction of sunlight reaches the surface. If you could stand on the surface of Venus, everything would look dimly lit, with a maximum visibility of about 3 km.

The upper cloud deck of Venus is between 60-70 km altitude. This is the part of Venus that we see in telescopes and visible light photographs of the planet.

The clouds on Venus rain sulfuric acid. This rain never reaches the ground, however. The high temperatures evaporate the sulfuric acid drops, causing them to rise up again into the clouds again.

Venus spacecraft have detected lightning on Venus, coming out of the clouds with a similar process to what we have on Earth. The first bursts of lightning were detected by the Soviet Venera probes and later confirmed by ESA’s Venus Express spacecraft.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

Posted on by Fraser Cain

Venus Number of Moons

Venus. Credit: NASA

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Earth has the Moon, Jupiter has more than 50 moons, even Pluto has 3 moons. So what about Venus? What number of moons does Venus have? Ready for this?

Venus: number of moons: 0.

That’s right, Venus has no moons at all; not even captured asteroids like Mars. Why doesn’t Venus have any moons?

There appears to be evidence that Venus did have moons in the ancient past. That’s because Venus is rotating backwards from the rest of the planets. Seen from above, all of the planets rotate counter-clockwise. From the surface of the planets, the Sun seems to rise in the east, travel across the sky and then set in the west. But on Venus, it’s backwards; the planet is rotating clockwise, so the Sun rises in the west and sets in the east.

Even stranger, a day on Venus lasts 243 days, while a year on Venus is only 224.7 days. In other words, a day on Venus lasts longer than a year on Venus.

This strange rotation is evidence that Venus was probably whacked hard in the past by a planetesimal; a similar event is believed to have happened to the Earth billions of years ago, forming the Moon. It’s possible that this collision threw up material that coalesced into a moon, or even moons. But the material wasn’t high enough in orbit to remain stable around Venus. Instead of orbiting the planet for billions of years, it would have crashed back into the planet. Perhaps the tidal forces from the Sun made the orbit unstable.

Unfortunately the evidence of any past moons of Venus has been completely wiped away. At some point in the last 300-500 millions years ago, the outer crust of Venus was completely resurfaced, removing all trace of impact craters, and ancient volcanism.

So we’ll never truly know the number of moons that Venus had. But today, it has no moons.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

Posted on by Anne Minard

Kepler Scores its First Exoplanet Sighting

First results from the Kepler mission. Credit: NASA

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NASA researchers have published confirmation this week that the Kepler mission will be able to reveal the presence of Earth-sized planets around Sun-like stars. The mission’s first scientific results appear today in the journal Science.

Lead author William Borucki, of NASA Ames Research Center in Moffett Field, California, and his colleagues announced that Kepler has detected the giant extrasolar planet HAT-P-7b, one of the roughly two dozen exoplanets that have been discovered by ground-based observations and the CoRoT mission as they “transited” in front of their stars, periodically dimming the starlight.

Many more exoplanets — more than 300 now — have been detected by the so-called “wobble” or radial velocity method, where a planet’s gravitational tug influences the motion of its star.

HAT-P-7b is comparable to Jupiter in size and orbits a star analogous to our Sun. It showed up in 10 days’ worth of Kepler data on the intensity of light from over 50,000 stars.

“The detection of the occultation without systematic error correction demonstrates that Kepler is operating at the level required to detect Earth-size planets,” the authors write.

The $500 million Kepler mission launched in March 2009 and will spend three and a half years surveying more than 100,000 sun-like stars in Cygnus-Lyra.

By staring at one large patch of sky for the duration of its lifetime, Kepler will be able to watch planets periodically transit their stars over multiple cycles, allowing astronomers to confirm the presence of planets and use the Hubble and Spitzer space telescopes, along with ground-based telescopes, to characterize their atmospheres and orbits. Earth-size planets in habitable zones would theoretically take about a year to complete one orbit, so Kepler will monitor those stars for at least three years to confirm the planets‘ presence.

Astronomers estimate that if even one percent of stars host Earth-like planets, there would be a million Earths in the Milky Way alone. If that’s true, hundreds of Earths should exist in Kepler’s target population of 100,000 stars.

Source: Science and NASA’s Kepler page

Posted on by Anne Minard

Titan Shaping Up to Look a Lot Like Pre-Life Earth

An artist's imagination of hydrocarbon pools, icy and rocky terrain on the surface of Saturn's largest moon Titan. Image credit: Steven Hobbs (Brisbane, Queensland, Australia)

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It’s more than a billion kilometers (759 million miles) away, but the more astronomers learn about Titan, the more it looks like Earth.

That’s the theme of two talks happening this week at the International Astronomical Union meeting in Rio de Janeiro, Brazil. Two NASA researchers, Rosaly Lopes and Robert M. Nelson of the Jet Propulsion Laboratory in Pasadena, California, are reporting that weather and geology have very similar actions on Earth and Titan — even though Saturn’s moon is, on average, 100 degrees C (212 degrees F) colder than Antarctica (and certainly much more frigid than either California or Brazil; lucky astronomers).

The researchers are also reporting a tantalizing clue in the search for life: Titan hosts chemistry much like pre-biotic conditions on Earth.

Wind, rain, volcanoes, tectonics and other Earth-like processes all sculpt features on Titan’s complex and varied surface — except, according to additional research being presented at the meeting,  scientists think the “cryovolcanoes” on Titan eject cold slurries of water-ice and ammonia instead of scorching hot magma.

“It is really surprising how closely Titan’s surface resembles Earth’s,” Lopes said. “In fact, Titan looks more like the Earth than any other body in the Solar System, despite the huge differences in temperature and other environmental conditions.”

The joint NASA/ESA/ASI Cassini-Huygens mission has revealed details of Titan’s geologically young surface, showing few impact craters, and featuring mountain chains, dunes and even “lakes.” The RADAR instrument on the Cassini orbiter has now allowed scientists to image a third of Titan’s surface using radar beams that pierce the giant moon’s thick, smoggy atmosphere. There is still much terrain to cover, as the aptly named Titan is one of the biggest moons in the Solar System, larger than the planet Mercury and approaching Mars in size.

New Cassini mosaic showing a dried-out lake at Titan's south pole.
New Cassini mosaic showing a dried-out lake at Titan's south pole.

Titan has long fascinated astronomers as the only moon known to possess a thick atmosphere, and as the only celestial body other than Earth to have stable pools of liquid on its surface. The many lakes that pepper the northern polar latitudes, with a scattering appearing in the south as well, are thought to be filled with liquid hydrocarbons, such as methane and ethane.

On Titan, methane takes water’s place in the hydrological cycle of evaporation and precipitation (rain or snow) and can appear as a gas, a liquid and a solid. Methane rain cuts channels and forms lakes on the surface and causes erosion, helping to erase the meteorite impact craters that pockmark most other rocky worlds, such as our own Moon and the planet Mercury.

Another Cassini instrument called the Visual and Infrared Mapping Spectrometer (VIMS) had previously detected an area, called Hotei Regio, with a varying infrared signature, suggesting the temporary presence of ammonia frosts that subsequently dissipated or were covered over. Although the ammonia does not stay exposed for long, models show that it exists in Titan’s interior, indicating that a process is at work delivering ammonia to the surface. RADAR imaging has indeed found structures that resemble terrestrial volcanoes near the site of suspected ammonia deposition.

Nelson said new infrared images of the region, also presented at the IAU, “provide further evidence suggesting that cryovolcanism  has deposited ammonia onto Titan’s surface. It has not escaped our attention that ammonia, in association with methane and nitrogen, the principal species of Titan’s atmosphere, closely replicates the environment at the time that life first emerged on Earth. One exciting question is whether Titan’s chemical processes today support a prebiotic chemistry similar to that under which life evolved on Earth?”

Many Titan researchers hope to observe Titan with Cassini for long enough to follow a change in seasons. Lopes thinks that the hydrocarbons there likely evaporated because this hemisphere is experiencing summer. When the seasons change in several years and summer returns to the northern latitudes, the lakes so common there may evaporate and end up pooling in the south.

Lead image caption: Artist’s impression of hydrocarbon pools, icy and rocky terrain on the surface of Saturn’s largest moon Titan. Image credit: Steven Hobbs (Brisbane, Queensland, Australia)

Source: International Astronomical Union (IAU)

Posted on by Nancy Atkinson

Half Comet-Half Asteroid a Fluke? Nope

Images of known MBCs from UH 2.2-meter telescope data. Credit: Henry Hsieh

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Back in 1996, astronomers discovered a strange object in the asteroid belt. They decided it was either a “lost” comet or an icy asteroid, as it ejected dust like a comet but had an orbit like an asteroid. No one had ever seen anything like the object, called 133P. Ever since it was found, astronomers have wondered if it was just an oddity — one of a kind. We now know it is not, and the discovery of more of these half asteroids/half comets means there is a new class of objects in our solar system.

One of these new objecst, 176P/LINEAR is also emitting dust as it orbits in the asteroid belt. It was found by Henry Hsieh at Queen’s University, Belfast in Northern Ireland. Hsieh has been working to figure out the unusual behavior of 133P. He hypothesized that either one of two things could explain the existence of the comet-asteroid: “(1.) 133P is a classical comet from the outer solar system that has evolved onto a main-belt orbit, or (2.) 133P is a dynamically ordinary main-belt asteroid on which subsurface ice has recently been exposed,” Hsieh wrote in his paper. “If (1) is correct, the expected rarity of a dynamical transition onto an asteroidal orbit implies that 133P could be alone in the main belt. In contrast, if (2) is correct, other icy main-belt objects should exist and could also exhibit cometary activity.”

Hsieh thought it was unlikely a comet could have been kicked around enough to end up in orbit in the asteroid belt, so he followed the assumption that 133P was a dynamically ordinary, yet icy main-belt asteroid. He set out to prove the hypothesis that 133P-like objects should be common and could be found by an well-designed observational survey.

Hsieh made 657 observations of 599 asteroids in the asteroid belt and found 176P/LINEAR. He also determined the asteroid is partially made of ice, which is being ejected following a collision with another object, thus the comet-like attributes.

Additionally, since there is evidence for past and even present water in main-belt asteroids, Hsieh says statistically there should be around 100 currently active Main Belt Comets (MBCs) as these objects are called, among the kilometer-scale, low-inclination, outer belt asteroid population.

The Technology Review blog offered suggestions for what to name these new objects that are half comet and half asteroid: “Comsteroids? Asteromets? Hsiehroids?”

Hseih’s paper,
 Hseih’s website on MBCs
Sources: Technology Review Blog, arXiv

Posted on by Fraser Cain

Albedo of Venus

Albedo of Venus

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The bond albedo of Venus is 0.75.

Albedo is a measurement of the reflectivity of an object. A theoretically perfect reflecting object would have an albedo of 1, and reflect 100% of the electromagnetic radiation that falls upon it. While an object that was perfectly black and doesn’t reflect any light would have an albedo of 0. In real life, objects in the Solar System have albedo values between 0 and 1. And in the case of Venus, the albedo is 0.75.

Just for comparison, the bond albedo of the Moon is only 0.12. That’s actually pretty dark. The brightest albedo in the Solar System is Saturn’s moon Enceladus, with an albedo of 0.99. It reflects almost all of the light that falls onto it.

One of the reasons that Venus is so bright in the sky is because of its high albedo. This albedo comes from the permanent cloud layer that surround the planet. These clouds are made up of sulfuric acid that reflect much of the radiation that falls upon them.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

Posted on by Brian Ventrudo

NASA Satellite Will Provide New Look At Cosmic X-Ray Sources

GEMS, the Gravity and Extreme Magnetism Small Explorer, will detect polarized X-rays from supernova remnants, neutron stars and black holes.

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NASA has announced the development of a space-based observatory to give astronomers a new way to view X-rays from exotic objects such as black holes, neutron stars, and supernovae.  Called the Gravity and Extreme Magnetism Small Explorer (GEMS), the mission is part of NASA’s Small Explorer (SMEX) series of cost-efficient and highly productive space-science satellites, and will be the first satellite to measure the polarization of X-rays sources beyond the solar system.

Polarization is the direction of the vibrating electric field in an electromagnetic wave. An everyday example of polarization is the attenuating effect of some types of sunglasses, which pass light that vibrates in one direction while blocking the rest.  Astronomers frequently measure the polarization of radio waves and visible light to get insight into the physics of stars, nebulae, and the interstellar medium, but few measurements have every been made of polarized X-rays from cosmic sources.

“To date, astronomers have measured X-ray polarization from only a single object outside the solar system — the famous Crab Nebula, the luminous cloud that marks the site of an exploded star,” said Jean Swank, a Goddard astrophysicist and the GEMS principal investigator. “We expect that GEMS will detect dozens of sources and really open up this new frontier.”

Black holes will be high on the list of objects for GEMS to observe.  The extreme gravitational field near a spinning black hole not only bends the paths of X-rays, it also alters the directions of their electric fields. Polarization measurements can reveal the presence of a black hole and provide astronomers with information on its spin. Fast-moving electrons emit polarized X-rays as they spiral through intense magnetic fields, providing GEMS with the means to explore another aspect of extreme environments.

“Thanks to these effects, GEMS can probe spatial scales far smaller than any telescope can possibly image,” Swank said. Polarized X-rays carry information about the structure of cosmic sources that isn’t available in any other way.

“GEMS will be about 100 times more sensitive to polarization than any previous X-ray observatory, so we’re anticipating many new discoveries,” said Sandra Cauffman, GEMS project manager and the Assistant Director for Flight Projects at Goddard.

Some of the fundamental questions scientists hope GEMS will answer include: Where is the energy released near black holes? Where do the X-ray emissions from pulsars and neutron stars originate? What is the structure of the magnetic fields in supernova remnants?

GEMS will have innovative detectors that efficiently measure X-ray polarization. Using three telescopes, GEMS will detect X-rays with energies between 2,000 and 10,000 electron volts. (For comparison, visible light has energies between 2 and 3 electron volts.) The telescope optics will be based on thin-foil X-ray mirrors developed at Goddard and already proven in the joint Japan/U.S. Suzaku orbital observatory.

GEMS will launch no earlier than 2014 on a mission lasting up to two years.  GEMS is expected to cost $105 million, excluding launch vehicle.

Orbital Sciences Corporation in Dulles, Va., will provide the spacecraft bus and mission operations. ATK Space in Goleta, Calif., will build a 4-meter deployable boom that will place the X-ray mirrors at the proper distance from the detectors once GEMS reaches orbit. NASA’s Ames Research Center in Moffett Field, Calif., will partner in the science, provide science data processing software and assist in tracking the spacecraft’s development.

Source: NASA Goddard

Also see Proposed Mission Could Study Space-Time Around Black Holes

Posted on by Fraser Cain

Winds on Venus

Layers of Venus' winds. Credits: R. Hueso (Universidad del País Vasco)

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Seen from Earth, Venus is a featureless ball; even the most powerful Earth-based telescope shows only clouds and more clouds. But those clouds are moving fast. The winds on Venus are powerful, circulating around the planet in just a matter of days. But because of Venus’ high temperatures and intense atmospheric pressure, they don’t behave like the winds on other planets.

The atmosphere of Venus extends up from the surface of the planet, up to an altitude of about 250 km. Down at the surface, the air pressure is 93 times higher than what we experience here on Earth. But once you rise up in altitude, the pressure drops to Earth surface pressure and then even lower.

At the very top of the cloud layers on Venus, wind speeds reach 355 km/hour (or 100 meters/second). This is the same the jet stream here on Earth. As you descend through the cloud layers, though, the wind speeds pick up. In the middle layer, the winds can reach speeds of more than 700 km/hour. That’s faster than the fastest tornado speed ever recorded on Earth.

But then as you descend further down through the clouds, the thickening atmosphere slows the winds down, so that they act more like currents in the ocean than winds in the atmosphere. Down at the surface, the winds only move at a few km/hour. That’s not much, but the thick atmosphere can still kick up dust and push around small rocks.

The winds on Venus travel in a westerly direction, the same backwards direction that Venus rotates. Seen from above, Venus rotates in a clockwise direction. This is backwards from the other 7 planets, which rotate counter-clockwise.

We have written many articles about Venus for Universe Today. Here’s an article about Venus’ wet, volcanic past, and here’s an article about how Venus might have had continents and oceans in the ancient past.

Want more information on Venus? Here’s a link to Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We have recorded a whole episode of Astronomy Cast that’s only about planet Venus. Listen to it here, Episode 50: Venus.

Posted on by Anne Minard

Spitzer Changes Its Glasses, Sees Cotton Candy

Infrared picture of a cloud, known as DR22, bursting with new stars in the Cygnus region of the sky.

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The Spitzer Space Telescope has run out of the liquid helium that kept its optics cool — but the scope has already returned compelling new images as if to say:

I don’t need no stinkin’ helium.

At five and a half years, Spitzer’s prime mission more than doubled initial expectations. It finally ran out of liquid helium in May and was retooled for a new “warm mission” that began July 27. With its two remaining infrared channels, the telescope promises to observe with roughly the same sensitivity as a 30-meter ground-based telescope.

The lead infrared image shows the dying star NGC 4361, which was once hot like our Sun before it puffed out.

This next one shows dusty gas in blue and hot clouds in orange in DR22, a cloud bursting with new stars in the Cygnus region of the sky.

Spitzer's infrared eyes can both see dust and see through dust. The blue areas are dusty clouds, and the orange is mainly hot gas.
Spitzer's infrared eyes can both see dust and see through dust. The blue areas are dusty clouds, and the orange is mainly hot gas.

The new images were snapped with the two infrared channels that still work at Spitzer’s still-quite-chilly temperature of 30 Kelvin (about minus 406 degrees F). The two infrared channels are part of Spitzer’s infrared array camera: 3.6-micron light is blue and 4.5-micron light is orange.

This last picture shows a relatively calm galaxy called NGC 4145, 68 million light-years away in the constellation Canes Venatici.

Barred Spiral Galaxy NGC 4145, 68 million light-years away in the constellation Canes Venatici.
Barred Spiral Galaxy NGC 4145, 68 million light-years away in the constellation Canes Venatici.

All of The new pictures were taken while the telescope was being re-commissioned, on July 18 (NGC 4145, NGC 4361) and July 21 (Cygnus), 2009.

Since its launch from Cape Canaveral, Florida on Aug. 25, 2003, Spitzer has made many discoveries. They include planet-forming disks around stars, the composition of the material making up comets, hidden black holes, galaxies billions of light-years away and more.

Perhaps the most revolutionary and surprising Spitzer finds involve planets around other stars, called exoplanets. In 2005, Spitzer detected the first photons of light from an exoplanet.

Warm Spitzer will address many of the same science questions as before. It also will tackle new projects, such as refining estimates of Hubble’s constant, or the rate at which our universe is stretching apart; searching for galaxies at the edge of the universe; characterizing more than 700 near-Earth objects, or asteroids and comets with orbits that pass close to our planet; and studying the atmospheres of giant gas planets expected to be discovered soon by NASA’s Kepler mission.

“The performance of the two short wavelength channels of Spitzer’s infrared array camera is essentially unchanged from what it was before the observatory’s liquid helium was exhausted,” said Doug Hudgins, the Spitzer program scientist at NASA Headquarters in Washington.

Credit for all images: NASA/JPL-Caltech

Source: NASA’s Spitzer site and a press release through the American Astronomical Society (AAS).

Posted on by Nancy Atkinson

Where In The Universe #65

Here’s this week’s image for the WITU Challenge, to test your visual knowledge of the cosmos. Take a look at this image and see if you can determine where in the universe this image is from. This one is a little different, but several readers sent it in, suggesting we use it. We’ll provide the image today, but won’t reveal the answer until tomorrow. This gives you a chance to mull over the image and provide your answer/guess in the comment section. Please, no links or extensive explanations of what you think this is — give everyone the chance to guess.

UPDATE: The answer has now been posted below.

This is a model of an exploding star’s core created by the U.S. Department of Energy’s Argonne National Laboratory developed to help show what happens inside core-collapse supernovae. The model was made using the lab’s IBM Blue Gene/P machine, currently ranked seventh on a list of the world’s most powerful supercomputers. Argonne’s Blue Gene/P boasts more than 160,000 processors, as many as would be found in Giants Stadium were it filled to capacity with people toting dual-core laptops.

To find out more about this images see this article in Scientific American.