Ian O'Neill, Author at Universe Today

July 22, 2008December 24, 2015 by Ian O'Neill

Polaris Brightness Variations are Revived, Astronomers Mystified

[/caption]
Polaris is a well known Cepheid variable, but its periodic brightness variations have been steadily decreasing in amplitude for the last hundred years. Around the beginning of the 20th Century, Polaris’ brightness fluctuated every four days by 10%. Only ten years ago this variation had dropped to 2%, leading astronomers to believe this steady decline in the variability of the star was about to end. That was until recent observations uncovered an increase in variability to 4%. Polaris is an odd star in that it is a Cephid variable with a declining variability, and now astronomers are baffled as to why the brightness fluctuation has been revived…

Polaris (a.k.a. the North Star or Pole Star) has helped mankind navigate the globe since ancient times. Always positioned around the North Polar axis of the Earth, Polaris has also provided material for literature, poetry and religion. In astronomical terms it is also significant as it is a Cepheid variable with a regular variation in brightness, although it is the only Cepheid variable known that has been decreasing in brightness for the last several decades. But to complicate matters even further, this Type 1a supergiant (approximately 4-5 solar masses and 30 solar radii) appears to have been rejuvenated, and the vibrations have increased, varying in brightness by 4 %.

This discovery comes after observations made by Hans Bruntt from the University of Sydney and his international collaboration. Dr Alan Penny, co-investigator from the University of St. Andrews, UK, will present the team’s findings at his university’s “Cool Stars 15” conference this week.

In reality, the astronomers had focused their attention on Polaris in the hope to catch the point at which its variations ceased completely, only to find they had increased. “It was only through an innovative use of two small relatively unknown telescopes in space and a telescope in Arizona that we were able to discover and follow this star’s recovery so accurately,” Penny said. He was using the SMEI space camera, usually applied for solar-terrestrial observations of the solar wind, but he used it to accurately survey the night sky for Cepheid variables. At the same time, Bruntt was using a small telescope attached to NASA’s retired infra-red space telescope (WIRE) set up to study Polaris for a short period. When Penny noticed the strange recovery of Polaris in his SMIE data, it was compared with Bruntt’s WIRE data. It was therefore confirmed that Polaris’ vibrations had been revived.

Decrease over 100 years of amplitude of 4-day light variation of Polaris and of the increase since 2000. Credit: H. Bruntt et al. 2008

Backing up Penny and Bruntt, Professor Joel Eaton (Tennessee State University), who was using the AST automated spectroscopic telescope located in Arizona, noticed variations in the plasma velocity on the surface of Polaris. These measurements showed the brightness variations were correlated with expansion and contraction effects through the body of the star.

These observations are both exciting and perplexing. Although the variations observed in Cepheid variables are poorly understood, the vast majority of these “standard candles” do not change in brightness, let alone revive themselves. It would appear Polaris is undergoing a change that isn’t predicted by the standard model for stellar evolution, so the team of astronomers will be quick to follow up these observations with some theory as to what is causing the changes inside Polaris…

Sources: Physorg, arXiv

July 22, 2008December 24, 2015 by Ian O'Neill

Large Chunk of ISS Space Junk Becomes Easy to Observe (Video)

The Easy Ammonia Servicer (EAS) photographed on July 23rd, 2007, by ISS astronauts. Watch your heads, it's re-entering tomorrow! (NASA)

[/caption]
A huge piece of space debris, weighing 1400 lb (635 kg) and the size of two refrigerators, is gradually falling to Earth, giving observers on the ground a great opportunity to see it. The junk was jettisoned from the International Space Station (ISS) in 2007 and it is expected to re-enter the atmosphere later this year or early 2009. The Early Ammonia Servicer (EAS) was dropped from the ISS after a seven hour spacewalk and pushed in the opposite direction of the space station’s orbit shortly before a re-boost by a Soyuz resupply vehicle. This ensured the EAS would pose no danger to the ISS or crew on future orbits. Now the container is beginning its final few months in space and the bets are on as to where it will crash to Earth…

When the EAS, filled with ammonia coolant, had served its purpose the ISS crew had little choice but to throw it overboard. Astronaut Clay Anderson led the July 23rd 2007 operation with the assistance of cosmonauts Fyodor Yurchikhin and robotic arm operator Oleg Kotov as they shoved the EAS Earth-ward along with a 212 lb (96 kg) stanchion used to attach a camera to the station. The whole EVA lasted 7 hours and 41 minutes and the EAS was noted as the largest single piece of junk dropped from the ISS. At the time, mission control estimated that the EAS would orbit the Earth for 300 days; obviously this was a huge underestimate as it continues to spiral closer to the atmosphere one year after the mission.

The EAS is a huge piece of debris and easily tracked from the ground and poses no threat to missions, but it may be a hazard if, as expected, a large portion of the equipment survives re-entry. Dangers aside for now, the EAS is providing amateur astronomers with a new target to point their telescopes at. When the EAS was jettisoned, it was barely visible to the naked eye as it sped overhead with a magnitude of +4 to +4.5. Two days ago on July 20th, veteran satellite observer Marco Langbroek of Leiden, the Netherlands reported observing the EAS at an observable magnitude of +2.0. But it is moving very fast due to its decreased altitude.

Watch the EAS pass Altair in this high quality piece of video astronomy by Kevin Fetter (July 15th, 2008) »

Currently, the EAS can be seen over Europe, and next week North America will be able to spot it. For information on where and when to look for a chance to observe this huge lump of waste from the ISS, check out SpaceWeather.com’s Simple Satellite Tracker before it starts to flirt with our upper atmosphere in the next few months.

Sources: Space Weather, NASA, Collect Space.

July 21, 2008December 24, 2015 by Ian O'Neill

The Cosmic Void: Could we be in the Middle of it?

Is our region of space unique? As in there isn't much here? Credit: ESO. Edit: Ian O'Neill

[/caption]
On large scales, the Universe is homogeneous and isotropic. This means that no matter where you are located in the cosmos, give or take the occasional nebula or galactic cluster, the night sky will appear approximately the same. Naturally there is some ‘clumpiness’ in the distribution of the stars and galaxies, but generally the density of any given location will be the same as a location hundreds of light years away. This assumption is known as the Copernican Principle. By invoking the Copernican Principle, astronomers have predicted the existence of the elusive dark energy, accelerating the galaxies away from one another, thus expanding the Universe. But say if this basic assumption is incorrect? What if our region of the Universe is unique in that we are sitting in in a location where the average density is a lot lower than other regions of space? Suddenly our observations of light from Type 1a supernovae are not anomalous and can be explained by the local void. If this were to be the case, dark energy (or any other exotic substance for that matter) wouldn’t be required to explain the nature of our Universe after all…

Dark energy is a hypothetical energy predicted to permeate through the Cosmos, causing the observed expansion of the Universe. This strange energy is believed to account for 73% of the total mass-energy (i.e. E=mc²) of the Universe. But where is the evidence for dark energy? One of the main tools when measuring the accelerated expansion of the Universe is to analyse the red-shift of a distant object with a known brightness. In a Universe filled with stars, what object generates a “standard” brightness?

The progenitor of a Type Ia Supernova. Credit: NASA, ESA, and A. Field (STScI)

Type 1a supernovae are known as ‘standard candles’ for this very reason. No matter where they explode in the observable universe, they will always blow with the same amount of energy. So, in the mid-1990’s astronomers observed distant Type 1a’s a little dimmer than expected. With the basic assumption (it may be an accepted view, but it is an assumption all the same) that the Universe obeys the Copernican Principle, this dimming suggested that there was some force in the Universe causing not only an expansion, but an accelerated expansion of the Universe. This mystery force was dubbed dark energy and it is now a commonly held view that the cosmos must be filled with it to explain these observations. (There are many other factors explaining the existence of dark energy, but this is a critical factor.)

According to a new publication headed by Timothy Clifton, from the University of Oxford, UK, the controversial suggestion that the widely accepted Copernican Principle is wrong is investigated. Perhaps we do exist in a unique region of space where the average density is much lower than the rest of the Universe. The observations of distant supernovae suddenly wouldn’t require dark energy to explain the nature of the expanding Universe. No exotic substances, no modifications to gravity and no extra dimensions required.

Clifton explains conditions that could explain supernova observations are that we live in an extremely rarefied region, right near the centre, and this void could be on a scale of the same order of magnitude as the observable Universe. If this were the case, the geometry of space-time would be different, influencing the passage of light in a different way than we’d expect. What’s more, he even goes as far as saying that any given observer has a high probability of finding themselves in such a location. However, in an inflationary Universe such as ours, the likelihood of the generation of such a void is low, but should be considered nonetheless. Finding ourselves in the middle of a unique region of space would out rightly violate the Copernican Principle and would have massive implications on all facets of cosmology. Quite literally, it would be a revolution.

The Copernican Principle is an assumption that forms the bedrock of cosmology. As pointed out by Amanda Gefter at New Scientist, this assumption should be open to scrutiny. After all, good science should not be akin to religion where an assumption (or belief) becomes unquestionable. Although Clifton’s study is speculative for now, it does pose some interesting questions about our understanding of the Universe and whether we are willing to test our fundamental ideas.

Sources: arXiv:0807.1443v1 [astro-ph], New Scientist Blog

July 21, 2008December 24, 2015 by Ian O'Neill

Successful Test Firing of Orion Jettison Motor (Video)

Successful test-firing of Orion's jettison engines (Aerojet)

[/caption]
It looks like the hardware is gradually slotting into place for the development of the Orion capsule in NASA’s Constellation Program. On July 17th, the ultimate “ejection seat” was tested by NASA and rocket contractor Aerojet: The Orion jettison motor. Should there be an emergency during Ares rocket/Orion capsule during launch, the Orion capsule will have the capability to eject (whether it is on the launchpad or travelling through the atmosphere), ensuring the safety of the crew. This is the first safety measure of its kind, so a successful engine test can only help to boost confidence in the technology behind Orion…

Although there are concerns for the Constellation Program funding and technology-wise, there is good news coming from the development of NASA’s new Orion crew module. The first full-scale test firing of the jettison motor was successful, boosting confidence in the new safety system the capsule will have installed. Later this year, a full-scale “Pad Abort-1” test is scheduled in the New Mexico desert, where a mock Orion will be blasted clear of a model launchpad (up to a mile in altitude) to test the effectiveness of the system. Tests are already under way to deduce whether a dry or wet touch-down will be carried out by the Orion capsule using cadavers (human corpses) as crash-test dummies.

The jettison motor was tested at the Astrojet facility in Sacramento, California, which marks the start of a series of developmental tests before the finished article is integrated into the mock Orion module to begin the New Mexico tests. During last weeks test firing, engineers were testing acoustic, vibration and shock effects on the engines. It appears everything ran smoothly, indicating the jettison system is close to system-level demonstration.

View the test-firing on the Constellation Project site »

This is a critical stage in the development of Orion. Since the Columbia disaster in 2003, NASA has felt pressure to ensure the safety of their astronauts. Although strict guidelines are in place, space travel remains a risky business where tough decisions need to be made. Installing an Orion jettison system will be a huge piece of mind for mission controllers and Constellation astronauts should there be launch complications on the pad or as Ares powers through the atmosphere.

Source: NASA

July 18, 2008December 24, 2015 by Ian O'Neill

How do you Weigh a Supermassive Black Hole? Take its Temperature

A composite image of Chandra and Hubble Space Telescope observations of giant elliptical galaxy NGC 4649 (ASA/STScI/NASA/CXC/UCI/P. Humphrey et al.)

[/caption]
Working out the mass of huge black holes, like the ones hiding in the centre of galactic nuclei, is no easy task and attempts are being made to find novel ways to weigh them. Using data from the Chandra X-ray Observatory, two scientists have confirmed a theory they conceived ten years ago, that the supermassive black holes in the centre of galaxies strongly influence the nature of the gases surrounding them. So, acting like a remote thermometer, Chandra is being used to probe deep into the neighbourhood of these exotic objects, gauging their masses very accurately…

The supermassive black hole at the centre of NGC 4649 is a monster. It is about 3.4 billion times the mass of the Sun and a thousand times bigger than the black hole at the centre of the Milky Way. This fact makes it an ideal candidate to test new methods of measuring the mass of black holes to see how the results correlate with traditional methods. With a high degree of accuracy, scientists have proven that a previously untested theory of weighing black holes works by using the Chandra X-ray telescope.

Until now, supermassive black hole masses have been measured by observing the motions of stars and gas deep inside galactic nuclei, now astronomers are using the gravitational influence of the black hole over the hot gas trapped around the singularity. As the gas is pulled slowly toward the black hole, it is compressed and heated. The bigger the black hole, the higher the peak temperature. Chandra has been used to measure the peak temperature of the gas right in the centre of NGC 4649 to find the derived mass is identical to the mass previously measured by traditional means.

Fabrizio Brighenti from the University of Bologna in Italy, and William Mathews from the University of California at Santa Cruz have been working on this research for the past decade. It is only now, with the availability of a telescope as powerful as Chandra that these observations have been possible.

“It was wonderful to finally see convincing evidence of the effects of the huge black hole that we expected. We were thrilled that our new technique worked just as well as the more traditional approach for weighing the black hole.” – Fabrizio Brighenti

The black hole inside NGC 4649 appears to be in a dormant state; it doesn’t seem to be pulling in material toward its event horizon very rapidly and it isn’t generating much light as it slowly grows. Therefore, using Chandra to indirectly measure its mass by sensing the peak temperature of surrounding matter is required to weigh it. In the early universe, huge black holes such as these will have generated dramatic displays of light. Now, in the local Universe, such black holes lead a more retiring life, making them difficult to observe. This prospect excites the lead scientist on the project, Philip Humphrey. “We can’t wait to apply our new method to other nearby galaxies harboring such inconspicuous black holes,” he said.

Source: Physorg.com

July 17, 2008December 24, 2015 by Ian O'Neill

The Mysterious Mars Mounds

The mystery mounds on Mars. Credit: HiRISE/NASA

[/caption]

The High Resolution Imaging Science Experiment (HiRISE) continues to churn up stunning images as NASA’s Mars Reconnaissance Orbiter passes over the Martian surface. However, today’s example probably creates more questions than answers. Close to the Mars equator, south of Elysium Planitia, exists a crater and inside are some strange mounds that have so far eluded formal explanation. There are a few possibilities how these mounds may have formed and there may also be some examples on Earth too…

These features resemble mesas being stripped by Martian winds, or a build-up of sand/sediment dropped after a sand storm. Actually, these “mystery” features are not formed by sand and may not have been carved out by the wind. This image was commissioned by the HiRISE team to investigate a previous Mars Orbital Camera (MOC, on the Mars Global Surveyor) image of the region showed an ancient filled-in crater with some strange undulations in the bottom. Using the full 25 cm/pixel resolving power of HiRISE, these features can be seen in great detail.

The full HiRISE image of the region. Credit: NASA/JPL/University of Arizona

The largest mounds appear to be around 200 meters wide and vary in shape. Between the mounds appear to be wind-blown sand features, but scientists cannot explain the formation of the mounds at present. Attention is being paid to the rough surface texture of the mounds which suggests they may be outcrops of tough bedrock where loose sand or sedimentary rock has been eroded away, leaving the mounds behind. But how did this erosion occur and why is the bedrock so hardy?

The mounds could be ancient lava flows, fluvial sediment (indicating a plentiful supply of water in the past) or impact ejecta (i.e. hot material kicked into the old crater after another impact). Any one of these factors may have produced these hardened features. The strange thing is that there is a huge plain of these mounds, they aren’t isolated features. To be able to determine the origin of these mounds, further analysis needs to be carried out. The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on board the Mars Reconnaissance Orbiter will now be used to derive the mineral content of the region so a better understanding can be attained. But until then, these mounds will remain a true Martian mystery…

Source: HiRISE

July 17, 2008December 24, 2015 by Ian O'Neill

The Space Station as an Interplanetary Transport Vehicle?

The ATV has carried out a series of boosts for the ISS (ESA)

[/caption]
The International Space Station (ISS) is the jewel in the crown of human ingenuity and a testament to the incredible engineering mankind is capable of. The modular human outpost began construction in 1998 and it is hoped the final configuration will be complete by 2010. Apart from orbiting the Earth and the occasional re-boost by the docked Automated Transport Vehicle (ATV) “Jules Verne,” the ISS is going nowhere in a hurry. But wait a minute, isn’t that what the ISS is all about? Isn’t it simply an orbital science outpost? Well it is, but could it be something a bit more dynamic? Some critics cite the ISS as the most expensive waste of time the international collaboration of space agencies have ever been committed to; after all, who needs more zero-G experiments?

Solution: Attach a rocket and a steerage system and behold, we have a huge interplanetary transport vehicle, capable of travelling to the Moon and possibly to Mars. Who needs the Constellation Program anyway…

In an entertaining Washington Post article, Michael Benson discusses something I’ve never thought about. Rather than letting the ISS gradually fade away to a perpetually orbital retirement and eventual re-entry, why not do something a little more exciting with the football pitch-sized manned outpost? Forget more zero gravity experiments, stop throwing boomerangs around (yes, it came back), abandon the thousandth test on sprouting barley (although the beer might be good), install another toilet and let’s get serious. Upgrade the ISS into a full-blown spaceship and let’s begin exploring the Solar System in style!

So what’s the logic behind this conclusion? The ISS has 15,000 cubic feet of habitable space in 10 modules. It has ample working and living areas with scope for more. It can repair itself (using the Canadian robotic arm, controlled from inside the craft). This creates a more than comfortable space habitat for five permanent crew members plus the occasional guest. The space station has been billed as a “stepping stone” for future missions to the Moon and beyond, but those plans will probably not see the light of day in the ISS’ lifetime. Besides, as the Constellation Program shows, “stepping stones” are not needed; NASA is favouring the direct flight route to the Moon and Mars, stopping for lunch at the ISS isn’t necessary (besides, it’s a waste in fuel and resources).

Also, space stations are not new. The Russians have had a series of seven manned outposts (from the 1971-2001 Salyut and Mir programs) and the US had the 1973-79 Skylab station. There is a huge wealth of data available from the vast numbers of experiments that have been carried out, many present-day ISS “experiments” often appear to be slightly frivolous (i.e. the afore mentioned boomerang tests) when compared with the pioneering observations of the human body in space.

Artist impression of the final configuration of the ISS by 2010 (NASA)

All this said the ISS would be a great candidate for interplanetary travel. Although it might look a little ungainly, in the vacuum of space there’s little concern for aerodynamics (besides, for a station orbiting at a speed of 17,000 miles/hr, its shape is hardly holding it back!). It’s a tried and tested space-worthy candidate. Plus, the Constellation Program would fit right in. Perhaps the Orion module could be integrated into the station, and the engines from the powerful Ares rocket could be attached for propulsion. If something a little gentler is required, ion propulsion engines are becoming more and more sophisticated. If you’re thinking all of this is fantasy, well it isn’t. The station depends on “re-boosts” from docked resupply ships (such as Soyuz and the ATV) to occasionally increase its orbit. Back in April, Jules Verne pushed the 280 tonne station nearly three miles higher in only 12 minutes. This was achieved by using the small thrusters on the ATV; imagine if a larger thrust was achieved. Naturally, there may be structural questions hanging over the subject of thrust, but it seems only a small yet constant force is required for long-term interplanetary missions.

The International Space Station could be the ultimate “mother ship,” where astronauts live, but small planetary missions can detach and land on the Moon or even Mars. Besides, the ISS is set for retirement in 2016, perhaps it could be reborn and refurbished (in time for the realisation of the Constellation Program) into a new class of space vehicle; not a space station, a space exploration vehicle. After all, it needn’t only orbit the Earth…

Original Source: Washington Post

July 16, 2008November 30, 2020 by Ian O'Neill

Japanese SELENE (Kaguya) Lunar Mission Spots Apollo 15 Landing Site (Images)

The Apollo 15 Lunar Module in 1971 (NASA)

The Japanese lunar mission SELENE (Selenological and Engineering Explorer), also known as “Kaguya” has imaged the “halo” left behind in the lunar surface from Apollo 15’s lunar module engine exhaust plume. This is the first time a mission after the Apollo Program has detected such a feature. Apollo 15 landed on the Moon in 1971 in a region called Mare Imbrium, and SELENE’s Terrain Camera (TC) is continuing to reconstruct a 3D view of the region in unprecedented high-resolution.

The Hadley Rille, at the foot of the Apennine Mountains encircling the Mare Imbrium where Apollo 15 landed (NASA/JAXA)

Apollo 15 touched down on the lunar surface on July 31st, 1971 with David Scott and James Irwin, to carry out 18.5 hours of lunar extra-vehicular activity. This was the first “J mission” where a greater emphasis was placed on scientific studies. After the lunar module blasted off from the Moon, the lunar astronauts looked back on the launch site to see a fresh “halo” had formed after the surface was exposed to the module’s engine exhaust plume. The NASA astronauts took before and after shots of the landing zone where a lightening of the surface is evident. This halo had not been observed since Apollo 15, until the high resolution Terrain Camera on board SELENE imaged the region.

Apollo 15 halo as observed by SELENE (JAXA)

The image (pictured left) processed by the SELENE mission instrument team appears to show a bright patch in the exact location of the Apollo 15 lunar module landing zone at the foot of the Apennine Mountains around the Mare Imbrium close to “Hadley Rille.” The Hadley Rille is a sinuous rille with a length of 80km and depth of 300m. A “sinuous rille” is a long, narrow, meandering depression in the lunar surface (much like a river basin, minus water). One of the primary mission objectives of Apollo 15 was to understand the origin of this rille. The most likely cause of Hadley Rille is lava flow during early development of the Moon. For the Apollo 15 astronauts, this region will have been an awesome sight, especially being at the base of the towering Apennine Mountains.

Comparison between 3D SELENE landscape and Apollo 15 photo (JAXA/NASA)

The TC instrument has been instrumental in creating 3D visualizations of the lunar surface. In the example left, a comparison of the TC reconstruction and an actual Apollo 15 photograph are compared. Although some of the detail is missing (as the individual rocks are below the 10 meter resolving power of the orbiting camera), the scenes are identical. The SELENE mission (launched in 2007) continues to generate a huge amount of 3D data, contributing to some of the most detailed maps of the lunar surface ever created.

Source: JAXA

July 15, 2008December 24, 2015 by Ian O'Neill

Griffin: China Could Beat US in Moon Race

Long March II F rocket carrying Chinas second manned spacecraft Shenzhou VI in 2005 (Xinhua)

More bad news for NASA: even their administrator thinks China could beat the US to the Moon. Speaking with the BBC today, Michael Griffin shared his views about the Chinese space aspirations, pointing out that the super-state could, if they wanted to, send a manned mission to the lunar surface within a decade. NASA’s return mission to the Moon is planned to launch, at the earliest, in 2020, so this news is bound to knock the wind out of the US space agency’s hopes to continue where it left off in 1972…

In the last five years, China has been teetering on the edge of a full-manned space program. In 2003, the nation became only the third country to put a national into space (following the Russia and the USA), blasting Yang Liwei into orbit for 21 hours on the Shenzhou 5 spacecraft. Shenzhou 6 was launched with two astronauts (or “taikonauts”) on board, spending five days orbiting the Earth in 2005. This year, shortly after the Beijing Olympics in October, China is sending another manned mission into orbit, only this time it is hoped a spacewalk will be possible. With this rapid succession of successful manned launches, it comes as no surprise that attention is swinging away from NASA and to China for the next big step into space.

The last time man set foot on the Moon was in 1972 when Eugene Andrew Cernan, last man on the Moon, boarded the Apollo 17 lunar module. That was 36 years ago and space flight has changed significantly since then, now NASA has more competition, as highlighted by Griffin during a visit to London:

“Certainly it is possible that if China wants to put people on the Moon, and if it wishes to do so before the United States, it certainly can. As a matter of technical capability, it absolutely can.” – Dr Michael Griffin

As to whether it actually matters whether China are the next to land on the Moon is open to interpretation. After all, the first nation to set foot on Earth’s natural satellite was the USA, so is a return trip a big psychological “victory” for China? “I’m not a psychologist, so I can’t say if it matters or not. That would just be an opinion and I don’t want to air an opinion in an area that I’m not qualified to discuss,” Griffin added.

Recently, there has been increased cooperation between the US and China when sharing science and information. “We do have some early co-operative initiatives that we are trying to put in place with China, mostly centred around scientific enterprises. I think that’s a great place to start,” he said. Although many will view an early Chinese lunar mission as a NASA failure, both nations appear to be trying to forge close relationships that could possibly lead to joint space missions in the future. After all, even at the peak of the Cold War, the US and Russia began working on a common goal.

“I think we’re always better off if we can find areas where we can collaborate rather than quarrel. I would remind your [audience] that the first US-Soviet human co-operation took place in 1975, virtually at the height of the Cold War. And it led, 18 years later, to discussions about an International Space Station (ISS) programme in which we’re now involved.” – Dr Michael Griffin

Regardless of who gets to the Moon first, Griffin will be feeling the pressure of the “five-year gap” between the Shuttle being retired in 2010 and Constellation completion in 2015, there is still little alternative than relying on Russia and Europe for US access to space. Griffin has tried to increase Constellation funding by $2bn to bring completion forward by a year, but the application was quickly turned down by Congress. Those five long years may be more costly than the US government realizes as NASA loses more footing in manned access to space…

Source: BBC

July 15, 2008December 24, 2015 by Ian O'Neill

What’s the Weather Like on Extrasolar Planet HD 189733b?

An artists impression of HD 189733b, a configuration that matches the predictions of Spitzer observations (NASA)

HD 189733b is a Jupiter-sized extrasolar planet orbiting a yellow dwarf star. Due to its size and compact orbit, HD 189733b is one of the most studied extrasolar planets. HD 189733b shares many similar characteristics as HD 209458b (a.k.a. “Osiris,” as I reported in a UT article yesterday), and similar techniques have been used to analyse the spectral emissions from both parent stars. Although HD 189733b’s atmosphere isn’t thought to be evaporating like Osiris’, atmospheric gases extend far beyond the planetary “surface” allowing stellar light to pass through, giving astronomers a peek into what chemical compounds surround HD 189733b. From this analysis, scientists have deduced that water and methane is contained in the atmosphere; the Spitzer space telescope has even mapped the temperature distribution around the globe. Now, an Indian researcher has published work indicating a thin layer of particles exists in the upper atmosphere of HD 189733b. So what is the weather like on HD 189733b?

HD 189733b was discovered in 2005 and orbits a star in a binary system called HD 189733 in the constellation of Vulpecula. As the main star in the binary is a variable star (due to the transit of HD 189733b, periodically eclipsing the star), it has been designated with the variable name V452 Vulpeculae. The star system itself is located near the Dumbell Nebula, approximately 62 light years from Earth. As the star is relatively dim, as the exoplanet transits the star, there is an appreciable decrease in luminosity (of about 3%), creating the ideal conditions for the atmosphere of HD 189733b to be studied.

This exoplanet is approximately the same mass (1.15 Â± 0.04 M_J) and radius (1.154 Â± 0.032 R_J) as Jupiter, but it orbits very close to its parent star (~0.03 AU) so it is known as a “Hot Jupiter.” Due to the water/methane mix in the planet’s atmosphere, it is believed HD 189733b may have a blue hue, much like the colour of Uranus.

In 2007, the Spitzer Space Telescope observed HD 189733b and compiled a temperature map of the planet, showing that the equator was much hotter than the poles. Astronomers were also able to deduce that the atmosphere contains iron, silicate and aluminium oxide particulates. In new research by Sujan Sengupta from the Indian Institute of Astrophysics in Bangalore, it appears that these particles may collect in the upper atmosphere, forming a thin haze. This tentative conclusion was reached after careful examination of the polarization of emission from the star as HD 189733b transited. Preliminary results suggest there is a thin, reflective cloud in the exosphere.

So what is the weather like on HD 189733b? Hot and cloudy.

Source: arXiv Blog
Paper: arXiv:0807.1794v1 [astro-ph]