Posted on by Fraser Cain

Formation of the Solar System

Artist's impression of planetary formation. Image credit: NASA

Where did the Solar System come from? How did we go from space to a star with planets orbiting around it? Before we can look at the formation of the Solar System, we have to see what this region looked like.

Throughout the Milky Way, there are clouds of cold gas and dust, just sitting there, doing nothing. At some point in the distant past, this cloud was disturbed; either through the collision of another galaxy, or the explosion of a massive star.

The explosion would have sent waves through space that squeezed the gas and dust together. The clumping material was able to attract more material with its gravity, and started to collect into the solar nebula. The mutual movement of all the atoms in the cloud gave the solar nebula a direction to spin.

The Sun formed out of the largest collection of mass at the center of the solar nebula. Because it was spinning quickly, the rest of the nebula collected into a flattened disk around the newborn Sun – astronomers call this an accretion disk. Within the accretion disk, additional clumps gathered together; these would eventually form the planets.

The planets started out as tiny specks of dust that clumped together. As they continued to gather together, they became pebbles, rocks, boulders and eventually planetoids. These planetoids violently collided together to become the planets we know today.

By studying the decay of radioactive elements in meteorites, astronomers have been able to determine that the Solar System formed about 4.6 billion years ago.

When astronomers look out into the Universe, they see other Solar Systems forming at different stages. Some are large clouds of cold dust, others are starting to collapse. Others have accretion disks, and some might even have planets clearing out paths in the dust of the disk. We can’t see the formation of our own Solar System, but we can see it happening everywhere we look, so we assume our Solar System formed in the same way.

Here’s an article from Universe Today about planetary formation, and another about how the gas giants might have formed quickly.

Here’s an article from Wikipedia about the formation of the Solar System, and a link to NASA’s Solar System Simulator.

We have recorded a whole series of podcasts about the Solar System at Astronomy Cast. Check them out here.

Posted on by Nancy Atkinson

New Evidence for a Wetter, Warmer Ancient Mars

A 3-D image of a trough in the Nili Fossae region of Mars shows phyllosilcates (in magenta and blue hues) on slopes of mesas and canyon walls, showing water played a role in Mars’ past.

For all the Mars romanticists out there, we (yes, that means me, too) hope and maybe even dream that Mars once harbored water. And not just a little spurt of groundwater every once in awhile; we want the water to have been there in abundance and for enough time to make an impact on the planet and its environment. Now, proof of copious amounts of water in Mars’ past may have been found. Two new papers based on data from the Mars Reconnaissance Orbiter (MRO) found that vast regions of the ancient southern highlands of Mars hosted a water-rich environment, and that water played a sizable role in changing the minerals of a variety of terrains in the Noachian period – about 4.6 billion to 3.8 billion years ago.

John Mustard, a professor of planetary geology at Brown University and deputy principal investigator for the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) on MRO investigated the pervasive presence of phyllosilicates, clay-like minerals that preserve a record of water’s interaction with rocks.

Specifically, Mustard and his team from 13 other institutions focused on phyllosilicate deposits in areas like craters, valleys and dunes all over the planet. Among the highlights, he detected the clay-like minerals in fans and deltas within three regions, most notably the Jezero crater. That discovery marks the first time hydrated silicates have been found in sediments “clearly lain by water,” Mustard said.

The team also found phyllosilicate deposits in thousands of places in and around craters, including the pointed peaks located at the center of some of the depressions. This suggests that water was present 4-5 kilometers below the ancient Martian surface, the team wrote, due to the generally accepted principle that crater-causing collisions excavate underground minerals that are then exposed on the crater peaks.

“Water must have been creating minerals at depth to get the signatures we see,” Mustard said.

The clay minerals were formed at low temperatures (100-200°C) – an important clue to understanding the Red Planet’s potential for habitability during the Noachian period.

“What does this mean for habitability? It’s very strong,” Mustard said. “It wasn’t this hot, boiling cauldron. It was a benign, water-rich environment for a long period of time.”

In another paper, graduate student Bethany Ehlmann and colleagues from Brown and other institutions analyzed sediment deposits in two exquisitely preserved deltas in the Jezero crater, which held an ancient lake slightly larger than Lake Tahoe. The deltas suggest a flow from rivers carrying the clay-like minerals from an approximate 15,000-square kilometer watershed during the Noachian period.
Ehlmann said scientists cannot determine whether the river flow was sporadic or sustained, but they do know it was intense and involved a lot of water.

The deltas appear to be excellent candidates for finding stored organic matter, Ehlmann said, because the clays brought in from the watershed and deposited in the lake would have trapped any organisms, leaving in essence a cemetery of microbes.

“If any microorganisms existed on ancient Mars, the watershed would have been a great place to live,” Ehlmann said. “So not only was water active in this region to weather the rocks, but there was enough of it to run through the beds, transport the clays and run into the lake and form the delta,” she said.

Original News Source: Brown University Press Release

Posted on 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

Posted on 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 ± 0.04 MJ) and radius (1.154 ± 0.032 RJ) 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.

Spitzer temperature map of HD 189733b (NASA)

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]

Posted on by Nancy Atkinson

Eta Vs. Peony: Which Star Will Go Supernova First?

The reigning champion for brightest star in the Milky Way is Eta Carinae, a highly unstable star prone to violent outbursts. Astronomers say Eta Car’s life will probably end in 100,000 years or so with a supernova explosion. That’s relatively soon in cosmic terms. But the Spitzer Space Telescope has unearthed a contender, both in brightness and in the supernova competition, found in the dusty depths of our galaxy’s center. Astronomers say the Peony nebular star might be as bright as Eta. But the biggest question may be, which star will be the first to go supernova?

Eta Carinae has the luminosity of 4.7 million times the brightness of our sun. And the new challenger, Peony, burns with the brightness of an estimated 3.2 million suns. But astronomers say it’s hard to pin down the exact brightness for these blazing stars, so they might shine with a similar amount of light.

Scientists already knew the Peony nebula star was out there, but they couldn’t get a good look at it to estimate its luminosity because of its sheltered location in the dusty central hub of our galaxy. Spitzer’s dust-piercing infrared eyes can penetrate the dust, and look into areas not visible with optical telescopes. Spitzer data was teamed up with infrared data from the European Southern Observatory’s New Technology Telescope in Chile to calculate the Peony nebula star’s luminosity.

“Infrared astronomy opens extraordinary views into the environment of the central region of our galaxy,” said Lidia Oskinova of Potsdam University in Germany. “The Peony nebula star is a fascinating creature. It appears to be the second-brightest star that we now know of in the galaxy. There are probably other stars just as bright if not brighter in our galaxy that remain hidden from view.”

Peony, with its rather delicate sounding name, is really a Big Bertha of a star. Astronomers estimate the Peony nebula star started its life with a hefty mass of roughly 150 to 200 times that of our sun. It is a type of giant blue star called a Wolf-Rayet star, with a diameter roughly 100 times that of our sun. That means this star, if placed where our sun is, would extend out to about the orbit of Mercury.

Stars this massive are rare and puzzle astronomers because they push the limits required for stars to form. Theory predicts that if a star starts out too massive, it can’t hold itself together and must break into a double or multiple stars instead.

Peony (maybe in an effort to control her weight) sheds an enormous amount of stellar matter in the form of strong winds. This matter is pushed so hard by strong radiation from the star that the winds speed up to about 1.6 million kilometers per hour (one million miles per hour) in only a few hours.

Ultimately, the Peony nebula star will live a short life of a few million years and will blow up in the most fantastic of cosmic explosions called a supernova. In fact, Oskinova and her colleagues say that the star is ripe for exploding soon, which in astronomical terms mean anytime from now to millions of years from now.

When this star blows up, it will evaporate any planets orbiting stars in the vicinity,” said Oskinova. “Farther out from the star, the explosion could actually trigger the birth of new stars.”

In addition to the star itself, the astronomers noted a cloud of dust and gas, called a nebula, surrounding the star. The team nicknamed this cloud the Peony nebula because it resembles the ornate flower.

Eta and Peony. Deceptively petite and delicate names for such big stars about to go boom.

Let the competition begin!

News Source: JPL

Posted on by Astronomy Cast

Podcast: Galaxies

Whirlpool Galaxy. Image credit: Hubble

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This week we’re going to look at some of the biggest objects in the Universe: galaxies. It was the discovery of galaxies in the early 20th century that helped astronomers realize just how big the Universe is, and how far away everything is. Let’s learn how galaxies formed and how they evolve and change over time, merging with the neighbors. And what the future holds.

Click here to download the episode

Galaxies – Show notes and transcript

Or subscribe to: astronomycast.com/podcast.xml with your podcatching software.

Posted on by Nancy Atkinson

The “Other” Moon Rocket Some NASA Engineers Believe is Better Than Ares

Jupiter 110 and 232. From Directlauncher.com

There’s a group of NASA engineers who believe NASA is making a mistake with its new Constellation program to replace the shuttle, which will use the new Ares rockets for launches starting in 2014. Constellation is an all new program which requires everything to be built from the ground up. The group of engineers asks, why not use the systems we already have that work reliably? The engineers, who are working clandestinely after hours on their plans have been joined by business people and space enthusiasts, and they call the plan Direct 2.0. They believe this approach could be flying sooner than Ares, reducing the gap in the US’s access to space, and providing a smoother transition for the workforce. Additionally it is more powerful than Ares, has lower risks for the astronauts, adds additional servicing missions to the Hubble Space Telescope, and reduces the cost to orbit by half.

Proponents say the Direct 2.0 approach is more capable than Orion, can lift more mass into Earth orbit and boost more mass out of Earth orbit on to other destinations. The concept is simple: use the same orange external tank and booster rockets as the shuttle, but don’t use the orbiter. Put additional engines on the bottom of the tank, and the cone-shaped Orion capsule on the nose. They call the rocket system Jupiter, and not only would Jupiter have less cost per launch, but it would cost less per kilogram to put things in orbit. They also say the crew abort limits are safer than Ares 1, and would require only minor modifications to the current mobile launch platform.

Instead of having the separate Ares-I Crew Launch Vehicle (CLV) and Ares-V Cargo Launch Vehicle (CaLV) they use just one single Jupiter launcher, capable of performing both roles.

On their website, Directlauncher.com, they say “This change to NASA’s architecture completely removes the costs & risks associated with developing and operating a second launcher system, saving NASA $19 Billion in development costs, and a further $16 Billion in operational costs over the next 20 years.”

But recent articles by the Associated Press and the Orlando Sentinel say that NASA is not interested in this concept, and that its nothing more than a concept on the back of a napkin. Additionally, Ares is so far along, with test flights scheduled for next year, that there’s no turning back now.

But the Orlando Sentinel article says that NASA ended a study last fall which showed Direct 2.0 would outperform Ares. The initial results showed Direct 2.0 was superior in cost, overall performance and work-force retention, which is a big issue for Florida.

The engineers who work at NASA say they can’t speak out directly for fear of being fired, but an outside group who supports their efforts are trying to get the word out about the plan.

Check out their website includes a discussion forum, a presentation on their concept and much more. Here’s a video that explains the concept:

In short, they say the Direct 2.0 approach introduces many advantages over the current Ares Launch Vehicles, such as:

Shorter “gap” after the Shuttle retires (3 years vs. 5)
Earlier return to the Moon (2017 vs. 2019)
Deletes all risks and costs associated with a second new launch vehicle
Optimum use of the existing NASA & contractor experience

Original News Sources: AP, Orlando Sentinel, ABC’s Science and Society Blog, Directlauncher.com

Posted on by Ian O'Neill

Observing an Evaporating Extrasolar Planet

Artist impression of an evaporating planet orbiting a main sequence star (NASA)

Observations of planets orbiting other stars are becoming increasingly common as astronomical techniques become more and more sophisticated. But some extrasolar planets have a stronger than normal spectroscopic signature, often stronger than their optical signature. What could be causing this? In a recent study, observations of the extrasolar planet HD 209458b (also unofficially known as “Osiris”, which orbits a star in the constellation of Pegasus) revealed the strongest ever spectroscopic signature for a giant extrasolar planet, indicating Osiris is producing a huge cloud of gas. This gas is being lost from the planet’s atmosphere; Osiris is evaporating…

Osiris orbits a star (imaginatively) called HD 209458, a yellow dwarf not too dissimilar to our Sun (with 1.1 solar masses, 1.2 solar radii and a surface temperature of 6000 K). This extrasolar planet is special in that it is readily observable during its transit period of 3.5 terrestrial days. This very short year is due to its small orbital radius of only 0.047 AU. Osiris could be called a “hot Jupiter” as it is a gas giant, approximately 60% the mass of Jupiter and it orbits within 0.05 AU of its parent star. Because of its close proximity to HD 209458, Osiris has a surface temperature of over 1000 K.

Osiris’ size and compact orbit causes HD 209458’s luminosity to vary by 2% as the planet passes in front of the star. It is for this reason that HD 209458 has been designated as a “variable star” with the name V376 Pegasi.

However, spectroscopic analysis of the star show that emissions from elements such as neutral hydrogen and a carbon ion are dimmed far more than the 2% optical luminosity dimming. What could be causing this increase in dimming for spectroscopic emission lines? As light is produced by HD 209458, it is blocked by the Osiris planetary disk, creating the 2% dimming observed by optical instrumentation. However, something is increasing the disk cross section area, absorbing certain spectral wavelengths of stellar emission. For example, there is a 5-15% dimming effect on neutral hydrogen (H I at 121.6 nm) and a 7-13% dimming effect on both atomic oxygen (O I at 130.5 nm) and singly ionized carbon (C II at around 133.5 nm). This led astronomers to realize there was a cloud of gas surrounding Osiris, allowing most of the optical wavelengths to pass through, but absorbing some spectroscopic lines.

As Osiris is orbiting so close to its star, the X-ray and EUV emissions are exciting gases in the exosphere (the uppermost reaches of the gas giant’s atmosphere), causing heating and expansion. As the planet is strongly influenced by its star’s gravitational pull, tides will play a strong part in amplifying the expansion of Osiris’ atmosphere. At a certain point, when the planet’s “exobase” (or the base of the exosphere) reaches the Roche Limit, atmospheric gases will begin to escape the gravitational pull of the planet and the interaction with HD 209458 causes a geometrical blow-off, ejecting huge amounts of atmospheric gases into space. The atmosphere of Osiris is therefore evaporating.

This is an intriguing subject, and more details can be found in the review recently published by David Ehrenreich from the Laboratoire d’astrophysique de Grenoble, Universite Joseph Fourier, France.

Source: arXiv:0807.1885v1 [astro-ph]

Posted on by Nancy Atkinson

Echus Chasma From Mars Express

echus chasma. Credits: ESA/ DLR/ FU Berlin (G. Neukum)

 

Do these valleys on Mars come from gushes of water from past rainfall, or groundwater springs, or could they have possibly been formed from magma flows on Mars surface? That’s the debate surrounding the many valleys, chasms and dry gullies found on the Red Planet.

The majority of planetary geologists seem to favor the idea of water flowing on Mars surface in the past. The images shown here of Echus Chasma are from the European Space Agency’s Mar’s Express, and its High-Resolution Stereo Camera (HRSC). Echus Chasma is believed to be one of the largest water source regions on the Red Planet. The valleys, cut into the landscape look similar to drainage networks found on Earth.

The image here has a ground resolution of approximately 17 m/pixel, and is so clear and distinct it almost makes you feel like you’re there!

echus chasma. Credits: ESA/ DLR/ FU Berlin (G. Neukum)
Image of the Echus Chasma showing elevation. Credits: ESA/ DLR/ FU Berlin (G. Neukum)

Echus Chasma is approximately 100 km long and 10 km wide. Echus Chasma is believed to be the water source region that formed Kasei Valles, a large valley which extends thousands of kilometers to the north. It’s located in the Lunae Planum high plateau, north of Valles Marineris – the Grand Canyon of Mars. This image indicates elevation data, also obtained by the HRSC.

Echus Chasma mosaic. Credits: ESA/DLR/ FU Berlin (G. Neukum)
Echus Chasma mosaic. Credits: ESA/DLR/ FU Berlin (G. Neukum)

An impressive cliff, up to 4000 m high, is located in the eastern part of Echus Chasma. Possibly, gigantic water falls may once have plunged over these cliffs on to the valley floor. The remarkably smooth valley floor was later flooded by basaltic lava.

Echus Chasma. Credits: ESA/ DLR/ FU Berlin (G. Neukum)
Overhead view of the Echus Chasma. Credits: ESA/ DLR/ FU Berlin (G. Neukum)

The smaller valleys, also called sapping canyons, are believed to originate from the discharge of groundwater.

Original News Source: ESA

Posted on by Nancy Atkinson

Where Do Meteorites Come From?

If you’ve ever held a real meteorite in your hand, you probably wanted to know, “Where has this rock been in space and where did it come from?” Until now, no one has been able to definitively establish where the majority of meteorites found on Earth came from because of the changes that occur in meteorites after they are ejected from the asteroids they were originally part of. The most common type of meteorite found on Earth, about 75% of those identified, are chondrites, stony bits of space rocks that didn’t undergo any melting while out in space. Two astronomers say have determined that most of these meteorites come from the asteroid belt between Mars and Jupiter. Using the GEMINI telescope, they found that asteroids in that region are similar to chondrites found on Earth.

This discovery is the first observational match between the most common meteorites and asteroids in the main belt. It also confirms the role of space weathering in altering asteroid surfaces.

To find the parent asteroid of a meteorite, the astronomers compared the spectra of a meteorite specimen to those of asteroids. This is a difficult task because meteorites and their parent asteroids underwent different processes after the meteorite was ejected. In particular, surfaces of asteroids are known to be altered by a process called “space weathering”, which is probably caused by micrometeorite and solar wind action that changes the surface and spectra of asteroid surfaces.

Meteoroids are created, usually when there is a collision between asteroids. When an impact of a large asteroid occurs, the fragments broken off can follow the same orbit as the primary asteroid. These groups of fragments are called “asteroid families.” Until recently, most of the known asteroid families have been very old (they were formed 100 million to billions of years ago), and younger families are more difficult to detect because asteroid fragments are closer to each other.

In 2006, four new, extremely young asteroid families were identified, with an age ranging from 50,000 to 600,000 years. The astronomers, Thais Mothé-Diniz from Brazil and David Nesvorný from the US observed these asteroids, obtaining visible spectra. They compared the asteroids spectra to the spectra of an ordinary chondrite (the Fayetteville meteorite, shown in the top photo) and found they matched.

Identifying the parent asteroid of a meteorite is a unique tool when studying the history of our solar system because one can infer both the time of geological events (from the meteorite that can be analyzed through dating techniques) and their location in the solar system (from the location of the parent asteroid).

Meteorites are also a major tool for knowing the history of the solar system because their composition is a record of past geologic processes that occurred while they were still incorporated in the parent asteroid.

Original News Source: Astronomy and Astrophysics