Posted on by Ken Kremer

Assembling Curiosity’s Rocket to Mars

The first stage of the Atlas V rocket for NASA's Mars Science Laboratory (MSL) mission is lifted into an upright position for placement inside the Vertical Integration Facility at Space Launch Complex 41 on Cape Canaveral Air Force Station. A United Launch Alliance Atlas V-541 configuration will be used to loft MSL into space. NASA/Jim Grossmann

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Assembly of the powerful Atlas V booster that will rocket NASA’s Curiosity Mars Science Laboratory rover to Mars is nearly complete. The Atlas V is taking shape inside the Vertical Integration Facility at Space Launch Complex 41 at Cape Canaveral Air Force Station in Florida.

The rocket is built by United Launch Alliance under contract to NASA as part of NASA’s Launch Services Program to loft science satellites on expendable rockets.

At Launch Complex 41 at Cape Canaveral Air Force Station in Florida, workers guide an overhead crane as it lifts the Centaur upper stage for the United Launch Alliance Atlas V in the Vertical Integration Facility (VIF). Once in position, it will be attached to the Atlas V booster stage, already at the pad. Credit: NASA/Jim Grossmann

The Atlas V configuration for Curiosity is similar to the one used for Juno except that it employs one less solid rocket motor in a designation known as Atlas 541.

4 indicates a total of four solid rocket motors are attached to the base of the first stage vs. five solids for Juno. 5 indicates a five meter diameter payload fairing. 1 indicates use of a single engine Centaur upper stage.

Blastoff of Curiosity remains on schedule for Nov. 25, 2011, the day after the Thanksgiving holiday in the U.S. The launch window for a favorable orbital alignment to Mars remains open until Dec. 18 after which the mission would face a 26 month delay at a cost likely to be in the hundreds of millions of dollars.

Curiosity is set to touchdown on Mars at Gale Crater between August 6 & August 20, 2012. The compact car sized rover is equipped with 10 science instruments that will search for signs of habitats that could potentially support martian microbial life, past or present if it ever existed.

At the Vertical Integration Facility (VIF) at Launch Complex 41 at Cape Canaveral Air Force Station in Florida, the Centaur upper stage for the United Launch Alliance Atlas V is in position in the Vertical Integration Facility (VIF). It then will be attached to the Atlas V booster stage, already at the pad. The Atlas V is slated to launch NASA's Mars Science Laboratory (MSL) mission - the compact car-sized Curiosity Mars rover. Credit: NASA
With a unique view taken from inside Vertical Integration Facility (VIF) at Launch Complex 41 at Cape Canaveral Air Force Station in Florida, an overhead crane lifts the Centaur upper stage for the United Launch Alliance Atlas V. Once in position in the VIF it will be attached to the Atlas V booster stage, already at the pad. NASA/Jim Grossmann
Workers guide an overhead crane as it lifts the Centaur upper stage for the United Launch Alliance Atlas V into the Vertical Integration Facility (VIF). NASA/Jim Grossmann
An overhead crane lifts the Centaur upper stage for the Atlas V. NASA/Jim Grossmann
The final solid rocket motor (SRM) hangs in an upright position for mating to a United Launch Alliance Atlas V rocket. NASA/Jim Grossmann
A crane lifts the 106.5-foot-long first stage of the Atlas V rocket for NASA's Mars Science Laboratory (MSL) mission through the open door of the Vertical Integration Facility at Space Launch Complex 41. Credit: NASA/Cory Huston
Curiosity Mars Science Laboratory Rover - inside the Cleanroom at KSC. Credit: Ken Kremer

Meanwhile NASA’s Opportunity Mars rover is nearing 8 continuous years of Exploration and Discovery around the Meridiani Planum region of the Red Planet.

Read Ken’s continuing features about Curiosity and Opportunity starting here:
Encapsulating Curiosity for Martian Flight Test
Dramatic New NASA Animation Depicts Next Mars Rover in Action
Opportunity spotted Exploring vast Endeavour Crater from Mars Orbit
Twin Towers 9/11 Tribute by Opportunity Mars RoverNASA Robot arrives at ‘New’ Landing Site holding Clues to Ancient Water Flow on Mars
Opportunity Arrives at Huge Martian Crater with Superb Science and Scenic Outlook
Opportunity Snaps Gorgeous Vistas nearing the Foothills of Giant Endeavour Crater
Opportunity Rover Heads for Spirit Point to Honor Dead Martian Sister; Science Team Tributes

Posted on by Jon Voisey

Abuse From Other Universes – A Second Opinion

Concentric circles interpreted as bruises from collisions with alternate universes. Image Credit: Feeney et al.
Concentric circles interpreted as bruises from collisions with alternate universes. Image Credit: Feeney et al.

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At the end of last year, there was a flurry of activity from astronomers Gurzadyan and Penrose that considered the evidence of alternate universes or the existence of a universe prior to the Big Bang and suggested that such evidence may be imprinted on the cosmic microwave background as bruises of concentric circles. Quickly, this was followed by an announcement claiming to find just such circles. Of course, with an announcement this big, the statistical significance would need to be confirmed. A recent paper in the October issue of the Astrophysical Journal provides a second opinion.

The review was conducted by Amir Hajian at the Canadian Institute for Theoretical Astrophysics. To conduct the study, Hajian selected a large number of circles, similar to the ones reported in the previous studies and asked what the probability was that, randomly, the “edge” of the circles would contain hot-spots, similar to the ones predicted. These were then compared to the bruises reported by the other teams by examining their “variance” which is how much the points on the perimeter were spread around the average temperature.

Hajian notes that, with the resolution considered it would be possible to consider some 5 million circles. The results of his comparison demonstrated that it would be expected that some 0.3% of those should have features similar to the ones reported previously. With so many possibilities, this would imply that some 15,000 potential circles could be flagged as candidates for these cosmic bruises. Even the “best” candidate proposed in the Gurzadyan and Penrose study should still exist statistically.

As such, Hajian concludes that the features Gurzadyan and Penrose reported were not statistically anomalous. Hajian does not comment directly on Feeney et al.’s detection, but given theirs were constructed in a similar manner, it should be expected that they are similarly statistically insignificant. It would appear that if the fingerprints of other universes are embedded in the sky, they have been lost in the noise.

Posted on by VirtualAstro

Did The Draconids Perform?

Draconid Meteor Over Somerset UK Credit: Will Gater www.willgater.com

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After weeks of speculation of its intensity, the Draconid/Giacobond meteor shower finally arrived. Some astronomers predicted that this normally quiet meteor shower would deliver up to 1000 meteors per hour at its peak – Were they right?

At approximately 20:00 BST (21:00 UT) on October 8th 2011 the shower started in earnest and many in the UK and Europe looked forward to an evening of meteor watching.

Unfortunately, many people were under thick clouds and missed the display, but there were a few places where the clouds cleared and observers were treated to a memorable spectacle.

I have done many meteorwatch evenings in the past, but this one got exciting very quickly and the uncertainty of the amount of meteors was soon doused.

Many people including myself were popping outside and trying to glimpse meteors through the clouds, but most of the time the Meteorwatch Meteor Live View was being used.

Everything was fairly sedate apart from us all moaning about the weather, but then all of a sudden at approximately 20:30 BST (19:30 UT) The Meteor Live View app on the Meteorwatch website went crazy!

Meteor Live View Credit: meteorwatch.org/ Norman Lockyer Observatory UK

Many people started to get good breaks in the clouds including myself and there were reports of dozens of meteors in just a few short minutes, much to the envy and disappointment of those still clouded over.

At this time the International Meteor Organisation (IMO) reported observations of just over 300 meteors per hour (319 ZHR).

The evening continued and to everybody’s delight (to those who could see meteors), there were many. I saw 3 within a couple of seconds and this continued for about an hour.

Eventually rates started to decline, people saw less and the Meteor Live View started to show less activity.

At approximately 22:00 BST (21:00 UT) meteor activity dropped substantially – The show was over!

The IMO results were posted on their website with rates of just under 350 meteors per hour at the peak of the shower, reported by their observing stations.

Credit: IMO

Did the Dracondids/ Giacobonids live up to expectations in the end? I would say yes, a fairly heavy meteor shower, maybe it could be called a mini storm!

Posted on by Steve Nerlich

Astronomy Without A Telescope – Light Speed

The effect of time dilation is negligible for common speeds, such as that of a car or even a jet plane, but it increases dramatically when one gets close to the speed of light.

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The recent news of neutrinos moving faster than light might have got everyone thinking about warp drive and all that, but really there is no need to imagine something that can move faster than 300,000 kilometres a second.

Light speed, or 300,000 kilometres a second, might seem like a speed limit, but this is just an example of 3 + 1 thinking – where we still haven’t got our heads around the concept of four dimensional space-time and hence we think in terms of space having three dimensions and think of time as something different.

For example, while it seems to us that it takes a light beam 4.3 years to go from Earth to the Alpha Centauri system, if you were to hop on a spacecraft going at 99.999 per cent of the speed of light you would get there in a matter of days, hours or even minutes – depending on just how many .99s you add on to that proportion of light speed.

This is because, as you keep pumping the accelerator of your imaginary star drive system, time dilation will become increasingly more pronounced and you will keep getting to your destination that much quicker. With enough .999s you could cross the universe within your lifetime – even though someone you left behind would still only see you moving away at a tiny bit less than 300,000 kilometres a second. So, what might seem like a speed limit at first glance isn’t really a limit at all.

The effect of time dilation is negligible for common speeds we are familiar with on Earth, but it increases dramatically and asymptotically as you approach the speed of light.

To try and comprehend the four dimensional perspective on this, consider that it’s impossible to move across any distance without also moving through time. For example, walking a kilometer may be a duration of thirty minutes – but if you run, it might only take fifteen minutes.

Speed is just a measure of how long it takes you reach a distant point. Relativity physics lets you pick any destination you like in the universe – and with the right technology you can reduce your travel time to that destination to any extent you like – as long as your travel time stays above zero.

That is the only limit the universe really imposes on us – and it’s as much about logic and causality as it is about physics. You can travel through space-time in various ways to reduce your travel time between points A and B – and you can do this up until you almost move between those points instantaneously. But you can’t do it faster than instantaneously because you would arrive at B before you had even left A.

If you could do that, it would create impossible causality problems – for example you might decide not to depart from point A, even though you’d already reached point B. The idea is both illogical and a breach of the laws of thermodynamics, since the universe would suddenly contain two of you.

So, you can’t move faster than light – not because of anything special about light, but because you can’t move faster than instantaneously between distant points. Light essentially does move instantaneously, as does gravity and perhaps other phenomena that we are yet to discover – but we will never discover anything that moves faster than instantaneously, as the idea makes no sense.

We mass-laden beings experience duration when moving between distant points – and so we are able to also measure how long it takes an instantaneous signal to move between distant points, even though we could never hope to attain such a state of motion ourselves.

We are stuck on the idea that 300,000 kilometres a second is a speed limit, because we intuitively believe that time runs at a constant universal rate. However, we have proven in many different experimental tests that time clearly does not run at a constant rate between different frames of reference. So with the right technology, you can sit in your star-drive spacecraft and make a quick cup of tea while eons pass by outside. It’s not about speed, it’s about reducing your personal travel time between two distant points.

As Woody Allen once said: Time is nature’s way of keeping everything from happening at once. Space-time is nature’s way of keeping everything from happening in the same place at once.

Posted on by Tammy Plotner

Venus Express Discovers Venusian Ozone Layer

Venus Express has two solar cell panels per wing comprising alternating rows of standard triple junction solar cells as well as highly reflective mirrors to reduce the operating temperatures. There is twice as much sunlight in Venus's orbit as there is in Earth's orbit, plus additional thermal input from the Venusian surface and atmosphere – 75% of sunlight being reflected up from it. In certain cases, this results in Venus Express receiving an equivalent of the thermal input from 3.5 Suns. Credit: ESA

Every day brings on new discoveries and now ESA’s Venus Express spacecraft has delivered another… the red-hot planet has an ozone layer. Located high in the Venusian atmosphere, this planetary property will help us further understand how such features compare to Earth and Mars – along with refining our search for extra-terrestrial life.

This wonderful discovery was made while Venus Express was busy watching stars at the periphery. When seen through the planet’s atmosphere, the SPICAV instrument was able to distinguish gas types spectroscopically. By picking apart the wavelengths, ozone was detected through its absorption of ultraviolet light. It forms when sunlight breaks down the carbon dioxide molecules and releases oxygen. From there, they are distributed by planetary winds where the oxygen atoms will either combine into two-atom oxygen molecules, or form three-atom ozone.

“This detection gives us an important constraint on understanding the chemistry of Venus’ atmosphere,” says Franck Montmessin, who led the research.

This is an animation of Venus Express performing stellar occultation at Venus. Venus Express is the first mission ever to apply the technique of stellar occultation at Venus. The technique consists of looking at a star through the atmospheric limb. By analysing the way the starlight is absorbed by the atmosphere, one can deduce the characteristics of the atmosphere itself. Credits: ESA (Animation by AOES Medialab)

To date, ozone has been the sole property of Earth and Mars – but this type of discovery method could aid astronomers in searching for life on other worlds. Why is it important? Because ozone absorbs most of the Sun’s harmful ultra-violet rays… and because it is believed to be a by-product of life itself. When combined with carbon dioxide, this could create a signature as a strong signal for life. But don’t get too excited at the prospects, yet. The amount of ozone detected is also critical to refining models. It will need to be at least 20% of Earth’s value to even be considered.

“We can use these new observations to test and refine the scenarios for the detection of life on other worlds,” says Dr Montmessin.

While we know that chances are almost non-existent that Venus has life, it still brings it one step closer to planets like Mars and Earth.

“This ozone detection tells us a lot about the circulation and the chemistry of Venus’ atmosphere,” says Hakan Svedhem, ESA Project Scientist for the Venus Express mission. “Beyond that, it is yet more evidence of the fundamental similarity between the rocky planets, and shows the importance of studying Venus to understand them all.”

Original Story Source: ESA Space Science News.

Posted on by Jason Major

What is Airglow?

Recent photo from the ISS showing the airglow layer

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In many of the photos that we have featured recently from astronauts aboard the International Space Station, a glowing greenish-yellow band can be seen just above Earth’s limb. I’ve been asked before what this is, so I thought I’d explain it here. This is a phenomenon known as “airglow”.

A photochemical reaction that occurs high in the atmosphere, airglow is the result of various atoms, molecules and ions that get excited (chemistry-excited, that is… not “whee!”-excited) by ultraviolet radiation from the Sun and then release that energy as visible – as well as infrared – light when they return to their “normal” state. It’s not entirely unlike glow-in-the-dark toys or paint!

This light is most visible to the crew of the ISS when it is orbiting over the night side of the planet, and thus is seen in images like the one above. It appears like a thin band because viewing the atmosphere at a shallow angle – rather than directly down through it – increases the airglow layer’s relative visibility.

Most of visible airglow comes from oxygen atoms and molecules, which glow green… as commonly seen in the aurora. Other contributing elements include sodium and nitrogen. While present in the atmosphere at all layers, the region that glows visibly is typically constrained to a narrow band 85 – 95km (53-60 miles) high. The band itself is usually about 6 – 10km (4-6 miles) wide. The reason for this is that below those heights the atoms and molecules are more concentrated and collide more readily, releasing their energy sooner, and above it the density of the atoms is too low to do much colliding at all (to put it very simply.)

There are a lot of other factors involved with airglow as well, such as temperature and altitude, as well as different kinds of airglow depending on when in the day they occur. Nightglow is not exactly the same as dayglow, and then there’s even twilightglow… one could say there’s a lot glowing on in the upper atmosphere!

I’m here all week, folks.

You can read more about airglow in this informative article by the Institute of Astronomy and Astrophysics (Instituto de Astronomía y Física del Espacio) in Buenos Aires. Image credit: NASA.

 

Posted on by Jason Rhian

Lost in Translation: Cyrillic, Semantics and SpaceX

Previous statements made by Roscosmos officials have been clarified. According to sources, Russia merely wanted to ensure that SpaceX followed the same requirements as all other entities working to dock to the International Space Station. Image Credit: SpaceX

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Matters of space flight are no different than other international issues. What is said (or not said as the case may be) can suffer from being “lost in translation.” Such was the case recently when the media (this website included) reported on a Ria Novosti article that claimed that members within the Russian Space Agency had stated opposition to Space Exploration Technologies (SpaceX) docking their next Dragon spacecraft with the International Space Station.

“This was never a SpaceX issue,” said NASA Spokesman Rob Navias during a recent interview. “This was an International Space Program issue – which has final approving authority for any spacecraft set to dock with the International Space Station – be it the HTV, ATV or even Soyuz, they all have to go through the exact same process.”

SpaceX is prepping the next Falcon 9 for launch, liftoff is currently slated to occur no-earler-than Dec. 19. Photo Credit: Alan Walters/awaltersphoto.com

Navias stated emphatically that the Russian Space Agency never stated that they would not allow SpaceX to dock with the ISS – only that they wanted to ensure that the NewSpace firm followed the same procedure required of all other participants on the station (both a Stage Readiness Review as well as a Flight Readiness Review).

“This is basically an issue of semantics, of interpretation,” Navias said. “The Russian media wrote this article and when it was translated – it appeared as if that Russia was saying something – which they simply weren’t.”

The Ria Novosti report is now widely being disputed, by NASA, SpaceX and several other organizations. Photo Credit: Alan Walters/awaltersphoto.com

The partners involved in the International Space Station Program, the United States, Russia, the European Union, Japan and Canada all comprise a committee that determines matters concerning the orbiting laboratory. No one partner has a ‘controlling authority’ over the ISS. A good example of this is when Russia flew Dennis Tito to the ISS in 2001 – over initial U.S. objections.

If all goes according to plan SpaceX will launch the next Falcon 9 rocket with its Dragon spacecraft payload no-earlier-than Dec. 19, 2011 (although technically that launch is still on the books for Nov. 30). The Dragon, if cleared, will conduct station-keeping alongside the ISS where the station’s mobile servicing system (Canadarm 2) will grab it and then it will be docked to the ISS.

This mission could see both COTS 2 and COTS 3 mission objectives combined. Cargo from the International Space Station would then be placed into the Dragon which would return to Earth, splashing down in the Pacific Ocean, off the Coast of California.

If all goes according to plan, the next Dragon spacecraft to be launched will rendezvous with the ISS, where the Canadarm 2 will grapple it and attach it to the orbiting laboratory. Image Credit: SpaceX
Posted on by Ray Sanders

LROC “Treasure Map” Reveals Titanium Deposits

LROC WAC mosaic showing boundary between Mare Serenitatis and Mare Tranquillitatis. The relative blue colour of the Tranquillitatis mare is due to higher abundances of the titanium bearing mineral ilmenite. Image Credit: NASA/GSFC/Arizona State University

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At a joint meeting of the European Planetary Science Congress and the American Astronomical Society’s Division for Planetary Sciences, Mark Robinson and Brett Denevi have unveiled a map of the Moon combining observations in visible and ultraviolet wavelengths showing areas rich in Titanium ores. This discovery not only provides a potential source of a valuable metal, but also provides valuable information which will help scientists better understand lunar formation and composition of the Moon’s interior.

How did Robinson and Denevi create this map, and what can other scientists learn from this new data?

“Looking up at the Moon, its surface appears painted with shades of grey – at least to the human eye. But with the right instruments, the Moon can appear colourful,” said Robinson, (Arizona State University). “The maria appear reddish in some places and blue in others. Although subtle, these colour variations tell us important things about the chemistry and evolution of the lunar surface. They indicate the titanium and iron abundance, as well as the maturity of a lunar soil.”

Robinson and the LROC team previously used similar methods with Hubble Space Telescope images to map titanium abundances near the Apollo 17 landing site, which had varying titanium levels. When Robinson compared the Apollo data with the HST images, it was revealed that titanium levels corresponded to the ratio of ultraviolet to visible light reflected by the lunar surface.

“Our challenge was to find out whether the technique would work across broad areas, or whether there was something special about the Apollo 17 area,” said Robinson. Using nearly 4000 images from the LRO Wide-Area Camera (WAC), Robinson’s team created a mosaic image, which was then studied using the techniques developed with the Hubble imagery. The research used the same ultraviolet to visible light ratio to deduce titanium abundance, which was verified by surface samples gathered by Apollo and Luna missions.

“We still don’t really understand why we find much higher abundances of titanium on the Moon compared to similar types of rocks on Earth. What the lunar titanium-richness does tell us is that the interior of the Moon had less oxygen when it was formed, knowledge that geochemists value for understanding the evolution of the Moon,” added Robinson.

On our Moon, titanium is found in a mineral known as ilmenite, which contains iron, titanium and oxygen. In theory, Lunar miners could process ilmenite to separate the iron, titanium and oxygen. Aside from the elements present in ilmenite, Apollo data shows that minerals containing titanium can retaining particles from the solar wind, such as helium and hydrogen. Future inhabitants of the Moon would find helium and hydrogen, along with oxygen and iron to be vital resources.

“The new map is a valuable tool for lunar exploration planning. Astronauts will want to visit places with both high scientific value and a high potential for resources that can be used to support exploration activities. Areas with high titanium provide both – a pathway to understanding the interior of the Moon and potential mining resources,” said Denevi (John Hopkins University).

The new maps also provide insight into how lunar surface materials are altered by the impact of charged particles from the solar wind and high-velocity micrometeorite impacts. Over time, lunar rock is pulverized into a fine powder by micrometeorite impacts, and charged particles alter the chemical composition and color of the surface.Recently exposed materials, such as ejecta from impacts appear bluer and have higher reflectivity than older Lunar regolith (soil). Younger material is estimated to take about half a billion years to fully “weather” to the point where it would blend in with older material.

“One of the exciting discoveries we’ve made is that the effects of weathering show up much more quickly in ultraviolet than in visible or infrared wavelengths. In the LROC ultraviolet mosaics, even craters that we thought were very young appear relatively mature. Only small, very recently formed craters show up as fresh regolith exposed on the surface,” said Robinson.

So it seems there’s always something new to be learned from our Moon. Coincidentally, tomorrow (October 8th) is International Observe the Moon Night, so make sure you grab your binoculars or telescope tomorrow night and do some lunar observations! Be sure to check out our previous coverage of International Observe the Moon Night by our Senior Editor, Nancy Atkinson at: http://www.universetoday.com/89522/need-an-excuse-to-gaze-at-the-moon-international-observe-the-moon-night-is-coming/

If you’d like to learn more about the Lunar Reconnaissance Orbiter Camera, visit: http://lroc.sese.asu.edu/

Source: Europlanet Research Infrastructure / Division for Planetary Sciences of the American Astronomical Society Joint Press Release

Posted on by Tammy Plotner

Observing Alert – Draconid Meteor Shower Could Unleash A Burst Of Activity On October 8!

Meteor Burst - Credit: NASA

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If you live in the Europe, North Africa, and the Middle East area, then keep watching the clock for 17-18:00 UTC when you may be in the right place at the right time for a burst of activity from the annual Draconid Meteor Shower. There’s a possibility you might see up to 1,000 meteors an hour!

As always, meteor showers are unpredictable events – but that doesn’t mean you can’t be prepared or forewarned. While the gibbous Moon will put a damper on fainter meteor streaks, observers in Europe, North Africa, and the Middle East. are well situated to catch a strong pocket of activity.

“Meteor showers are as difficult to predict as rain showers. The Draconids have surprised us before, and they may do so again.” says Canadian astronomer Paul Wiegert. “I’d encourage anyone outside on the night of October the 8 to look to the northern skies, just in case.”

This isn’t the first time the Draconid meteor shower has produced a brief storm. In 1933 and 1946 the activity reached an average hourly rate of 10,000. While that’s pretty incredible, the same cometary debris trail left quite a show in the years 1952, 1985, and 1998 when it produced hundreds per hour. These remnants of Comet Giacobini-Zinner aren’t the most dramatic of all showings – but knowing where the meteoroid stream is located makes such predictions valid.

When and where? In this case, start your observations just as soon as the sky gets dark. Since Draco is a northern constellation, those at high latitudes are move favored (sorry, southern hemisphere), so face toward the north and get comfortable. While the storm prediction will happen during daylight hours for North American observers, don’t give up hope! It looks like clear skies for many of us and chances are above average for catching a shooting star.

When opportunity knocks, ya’ gotta’ be there to open the door…

And don’t despair if you don’t live in Europe, North Africa, and the Middle East, or if you get clouded out. You can still watch and listen to meteors enter the atmosphere on Spaceweather radio. Meteors reflect radio signals as they burn up and you can hear this as eerie whistles and pings.

A similar system, still employing the radio reflection method displays meteors coming in on your computer with a cool graph – The Meteorwatch Live View

And follow Universe Today’s Adrian West on his Twitter feed, VirtualAstro and on his website MeteorWatch as he’ll be providing updates on observed meteor rates in various parts of the world.

For Further Reading: Wiegert’s original announcement via Physorg.com.

Posted on by Jon Voisey

What Would Earth Look Like from a Distant Star?

The "pale blue dot" of Earth captured by Voyager 1 in Feb. 1990 (NASA/JPL)

As the number of discovered extrasolar planets grows, astronomers begin looking at the next step: finding rocky Earth-like planets. In addition, astronomers would ideally like to block out the parent star and detect some of the reflected glow from the planet’s atmosphere in an attempt to characterize the chemical makeup. But what would an “Earth-like” planet’s reflected light look like? To answer this, a new paper explores what Earth should have looked like at various points in our planet’s history.

Currently, astronomers have a good understanding on how our planet reflects light. Even before satellites were launched that could observe this directly, we could see the reflected light from our home on the moon, an effect known as “Earthshine”. The amount of light reflected depends on what’s on the surface.

The paper considers five different types of reflecting materials. Water and vegetation tend to be strong absorbers of light at visible and ultraviolet wavelengths whereas ice and deserts are highly reflective. The amount of cloud cover, which also reflects a good deal of light, is the fifth.

With the modern Earth, our planet currently reflects about 32% of all incoming light. This changes by a few percent depending on the season, depending mostly on the amount of cloud cover.

This new study also analyzes what the amount of reflected light should have been for Earth, known as its albedo, during four other historical periods: the Late Cretaceous (90 million years ago), the Late Triassic (230 My ago), the Mississippian (340 My ago), and the Late Cambrian (500 My ago).

Using simulations based on the various surface features, the team from the Instituto de Astrofísica de Canarias owned by Spain, the team reconstructed the expected amount of cloud cover for these various epochs to consider their contributions to the overall albedo.

In general, the historical periods had strikingly similar amounts of reflectiveness due to “similar ocean-land-vegitation distribution” as well as similar distributions of continents between hemispheres and most deserts in low latitudes. The exception to this, was the Late Cambrian. While the average was only slightly higher, this period varied depending on which portion of the Earth was viewed.

At that time, the original supercontinent, Pangea was in the process of breaking up. They were still clustered and almost exclusively in the southern hemisphere. The sea levels were also significantly higher meaning a larger portion of land was submerged, covered by the non-reflective water. Lastly, most of the life was still concentrated in the oceans. Since it had not yet advanced to land, it is expected that the surface was mostly rocky desert terrain which would have high reflectivity. During the times when the breaking up supercontinent was facing an observer, the albedo would jump to as much as 37% only to sink to 32% when it rotated from view.

The team suggests that such a variation may allow astronomers to determine the rotation rates of planets in the future. In an ideal situation, it may even give clues to the geographical arrangement of continents.