New Observatories Could Spot Waterworlds

Image credit: ESA

The European Space Agency is planning a series of space-based observatories designed to search space for evidence of Earth-like worlds. But an easier target to spot should be waterworlds; six times the mass of the Earth and covered with an ocean 100km deep. The CNES/ESA mission Corot will launch in 2005, and should just barely be able to spot dimming stars as these “waterworlds” pass in front. Even more powerful Eddington will launch in 2008 and should be able to see planets half the size of Earth. Finally, Darwin will launch in 2014 and search for signs of life on Earthlike planets.

Science fiction writers and movie-makers have imagined a world completely covered by an ocean, but what if one really existed? Would such a world support life, and what would this life be like?

ESA could make science fiction become science fact when it finds such a world, if the predictions of a group of European astronomers are correct. The ESA mission Eddington, which is now in development, could be the key.

At the recent ESA co-sponsored ‘Towards Other Earths’ conference, nearly 250 of the world’s leading experts in planet detection discussed the strategy for finding Earth-like worlds. Alain L?ger and colleagues of the Institut d’Astrophysique Spatiale, France, described a new class of planets that could be awaiting discovery: ‘waterworlds’.

According to L?ger and his colleagues, these waterworlds would contain about six times the mass of Earth, in a sphere twice as wide as our planet. They would possess atmospheres and orbit their parent star at roughly the same distance that the Earth is from the Sun. Most excitingly, an ocean of water entirely covers each world and extends over 25 times deeper than the average depth of the oceans on Earth.

A hundred kilometres deep
According to calculations, the internal structure of a waterworld would consist of a metallic core with a radius of about 4000 kilometres. Then there would be a rocky mantle region extending to a height of 3500 kilometres above the core?s surface, covered by a second mantle made of ice up to 5000 kilometres thick. Finally, an ocean blankets the entire world to a depth of 100 kilometres, with an atmosphere on top of this.

With twice the radius of the Earth, they will be easily spotted by the Eddington spacecraft, which is designed to detect planets down to half the size of the Earth. “A waterworld passing in front of a star, somewhat cooler than the Sun, will cause a dimming in the stellar light by almost one part in a thousand. That’s almost ten times larger than the smallest variation Eddington is designed to detect. So, waterworlds ? if they exist ? will be a very easy catch for Eddington,” says Fabio Favata, ESA?s Eddington Project Scientist.

The CNES/ESA mission Corot, which is a smaller, precursor mission to Eddington due for launch around 2005, may also be just able to glimpse them, if they are close enough to their parent stars.

Origins of life
Scientists are now asking if such worlds could support life, and what would it be like, especially since water is a prime ingredient for life on Earth. While waterworlds seem to have everything to sustain life, there is a big question mark over whether they could actually allow it to start in the first place.

One of the leading theories for life’s origin in deep oceans is that it requires hot springs on the ocean floor, heated by volcanic activity like the ‘black smokers’ found here on Earth. On a waterworld however, 5000 kilometres of ice separate the ocean floor from any possible smokers. On the other hand, a water-surface origin may still be possible.

Perhaps the only way to know if anything lives on a waterworld will be to study them with ESA’s habitable-planet-finding mission, Darwin. When it launches in around 2014, this flotilla of spacecraft will look for tell-tale signs of life in the atmospheres of any planets, including waterworlds.

Original Source: ESA News Release

How the Owl Nebula Got its Shape

Image credit: Hubble/NOAO

A team of astronomers have created a model to explain how the Owl Nebula (NGC 3587) got its unique shape. They believe that the outer halo was formed when the star first lost mass and blew off its outer layer; the circular middle shell was caused by solar wind from the star blowing additional material; and then an even faster solar wind created the inner layer. Other planetary nebulae show a similar triple-shell appearance, so it’s likely they formed the same way.

Astronomers have assembled the first effective model for both the shape and evolutionary history of the Owl Nebula, the well-known planetary nebula in the constellation Ursa Major.

Named for its ghostly similarity to the face of the carnivorous bird of prey, the Owl Nebula (NGC 3587) has a complex structure consisting of three concentric shells. The aptly named nebula boasts a faint outer halo, a circular middle shell, and a roughly elliptical inner shell. The inner shell houses a bipolar cavity that forms the owl?s ?eyes,? and two areas of enhanced brightness are seen as the owl?s ?forehead? and ?beak.?

In an article published in the June 2003 Astronomical Journal, researchers from the University of Illinois at Urbana-Champaign, the Instituto de Astrofisica de Canarias in Spain, and Williams College in Williamstown, MA, present the first cohesive model for the appearance and evolution of the Owl Nebula.

Using observations made with the William Herschel Telescope in La Palma, Spain, and the 0.6-meter Burrell Schmidt telescope at Kitt Peak National Observatory, the researchers concluded that the halo of the Owl was formed when the parent star first underwent significant mass loss after the cessation of fusion in its core. The resulting instabilities then produced a stellar wind, driven by a combination of stellar pulsations and radiation pressure.

Evolution of the Owl?s parent star caused the stellar wind to intensify to a ?superwind,? driving even more gas and dust outward to form the middle shell. A subsequent faster stellar wind compressed the superwind to form the inner shell and bipolar cavity, but that wind has since ceased. The cavity is currently being back-filled with nebular material in the absence of the fast stellar wind, much as air flows back out of a balloon if you stop blowing into it.

?Different evolutionary models can produce the same structure for the nebula, but until now none has been able to also account for its motion,? says Martin A. Guerrero of the University of Illinois, the lead author of the recent study. ?There are many investigations of physical structures of planetary nebulae, but most studies only look at one piece of data and tend to ignore the bigger picture.?

Other planetary nebulae show triple-shell structure similar to the Owl Nebula and it is likely that they followed this same evolutionary path, according to co-author Karen Kwitter of Williams College. ?These nebulae form an illuminating sample to study, and the Owl Nebula is the nearest one, only about 2,000 light-years from Earth.?

Despite the name, planetary nebulae are not related to planets. Sir William Herschel gave these fascinating objects their misleading name in 1782 because, through his telescope, they resembled the appearance of Uranus and Neptune. In reality, planetary nebulae are shells of gas and dust ejected from aging stars. When the mass loss is finished, the hot core of the star is exposed, causing the ejected gas to glow.

A newly processed image of the Owl Nebula from this study is available above.

The Burrell Schmidt telescope is part of the Warner and Swasey Observatory of Case Western Reserve University, Cleveland, OH. The telescope is located at Kitt Peak National Observatory near Tucson, AZ, which is part of the National Optical Astronomy Observatory (NOAO). NOAO is operated by the Association of Universities for Research in Astronomy (AURA) Inc., under a cooperative agreement with the National Science Foundation.

Original Source: NRAO News Release

Discuss Articles on Universe Today

I’ve added a new feature to Universe Today: the ability for people to discuss stories posted on the website. If you look at today’s stories, you’ll see I added a “Discuss this story” link to each one. Click it and it’ll take you to a feedback page specifically for that story.

My hope is that people can use this mini-forum as a way to better understand the story. Ask questions, post your theories, and generally use it as a way to connect with other space fans. Of course, I’m sure it’ll also get used to catch my various typos. 🙂 I’ll be as active in the threads as I can, but I urge knowledgeable space experts to lend a hand answering people’s questions.

Please give me any feedback you may have about this.


Fraser Cain
Universe Today

Pluto’s Atmosphere is Expanding

Image credit: NASA

A team of astronomers from MIT reported today that Pluto’s atmosphere is expanding, even as the planet is getting further away from the Sun on its elliptical orbit. The team made their findings by watching the dimming of a star as Pluto passed in front. Astronomers were expecting to find the opposite situation; that its atmosphere would shrink as it gets further from the Sun, but it’s similar to the Earth, where early afternoon is hotter than noon, when the Sun is at its brightest. If all goes well, NASA will launch its New Horizons mission by 2006 to reach Pluto in 2015.

Pluto?s atmosphere is expanding even as it continues on its long orbit away from the sun, a team of astronomers from MIT, Boston University, Williams College, Pomona College, Lowell Observatory and Cornell University report in the July 10 issue of Nature.

The team, led by James Elliot, professor of planetary astronomy at MIT and director of MIT?s Wallace Observatory, made this finding by watching the dimming of a star when Pluto passed in front of it on Aug. 20, 2002. The team carried out observations using eight telescopes at Mauna Kea Observatory, Haleakala, Lick Observatory, Lowell Observatory and Palomar Observatory.

Elliot said the new results seem counterintuitive, because observers assumed Pluto?s atmosphere would begin to collapse as it cooled. In fact, the temperature of Pluto?s mostly nitrogen atmosphere has increased around 1 degree Celsius since it was closest to the sun in 1989.

Elliot attributes the increase to the same lag effect that we experience on Earth?even though the sun is most intense at its highest point at noon, the hottest part of the day is around 3 p.m. Because Pluto’s year is equal to 248 Earth years, 14 years after Pluto’s closest approach to the Sun is like 1:15 p.m. on Earth. At the rate of Pluto?s orbit, it may take another 10 years to cool down and would just be beginning to cool when the NASA New Horizons mission to Pluto, scheduled to be launched in 2006, reaches it in 2015.

Pluto?s predominantly nitrogen atmosphere is in vapor pressure equilibrium with its surface ice, and can therefore undergo large changes in pressure in response to small changes in surface ice temperature. As its icy surface gets colder, it condenses into fresh white frost that reflects more of the sun?s heat and gets colder still. As space dirt and objects collect on its surface, it darkens and absorbs more heat, accelerating the warming effect. Pluto has been darkening since 1954.

?The August 2002 data have allowed us to probe much more deeply into Pluto’s atmosphere and have given us a more accurate picture of the changes that have occurred,” Elliot said.

Pluto?s orbit is much more elliptical than that of the other planets, and its rotational axis is tipped by a large angle relative to its orbit. Both factors could contribute to drastic seasonal changes.

Since 1989, for example, the sun?s position in Pluto?s sky has changed by more than the corresponding change on the Earth that causes the difference between winter and spring. Pluto’s atmospheric temperature varies between around -235 and -170 degrees Celsius, depending on the altitude above the surface.

Pluto has nitrogen ice on its surface that can evaporate into the atmosphere when it gets warmer, causing an increase in surface pressure. If the observed increase in the atmosphere also applies to the surface pressure?which is likely the case?this means that the average surface temperature of the nitrogen ice on Pluto has increased slightly more than 1 degree Celsius over the past 14 years.

Researchers study faraway objects through occultations?eclipse-like events in which a body (Pluto in this case) passes in front of a star, blocking the star?s light from view. By recording the dimming of the starlight over time, astronomers can calculate the density, pressure and temperature of Pluto?s atmosphere.

Observing two or more occultations at different times provides researchers with information about changes in the planet?s atmosphere. The structure and temperature of Pluto?s atmosphere was first determined during an occultation in 1988. Pluto?s brief pass in front of a different star on July 19 led researchers to believe that a drastic atmospheric change was under way, but it was unclear whether the atmosphere was warming or cooling.

The data resulting from this occultation, when Pluto passed in front of a star known as P131.1, led to the current results. ?This is the first time that an occultation has allowed us to probe so deeply into Pluto’s atmosphere with a large telescope, which gives a high spatial resolution of a few kilometers,? Elliot said. He hopes to use this method to study Pluto and the Kuiper Belt objects more frequently in the future.

NASA recently authorized the New Horizons Pluto-Kuiper Belt mission to start building spacecraft and ground systems. The mission will be the first to Pluto and the Kuiper Belt. Richard P. Binzel, professor of earth, atmospheric and planetary sciences (EAPS) at MIT, is co-investigator.

The New Horizons spacecraft is scheduled to launch in January 2006, swing past Jupiter for a gravity boost and scientific studies in 2007, and reach Pluto and Charon moon of Pluto as early as summer 2015. Pluto is the only planet not yet observed at close range. This mission will seek to answer questions about the surfaces, atmospheres, interiors and space environments of the solar system?s outermost planet and its moon.

In the meantime, researchers hope to use SOFIA, a 2.5-meter telescope mounted in an aircraft being built by NASA in collaboration with the German space agency, starting in 2005. SOFIA would be able to be sent to the right location around the globe to best observe occultations, providing high-quality data on a much more frequent basis than is possible using ground-based telescopes alone.

In addition to Elliot, MIT co-authors are recent physics graduate Kelly B. Clancy; graduate students Susan D. Kern and Michael J. Person; recent MIT graduate Colette V. Salyk; and aeronautics and astronautics senior Jing Jing Qu.

The Williams College collaborators included Jay M. Pasachoff, professor of astronomy; Bryce A. Babcock, staff physicist; Steven V. Souza, observatory supervisor; and undergraduate David R. Ticehurst. They used the University of Hawaii’s telescope at the 13,800-foot altitude of the Hawaiian volcano Mauna Kea and a Williams College electronic detector normally part of eclipse expeditions.

Pomona College collaborators are Alper Ates and Ben Penprase. The Boston University collaborator is Amanda Bosh. Lowell Observatory collaborators are Marc Buie, Ted Dunham, Stephen Eikenberry, Cathy Olkin, Brian W. Taylor, and Lawrence Wasserman. Boeing collaborators are Doyle Hall and Lewis Roberts.

The United Kingdom Infrared Telescope collaborator is Sandy K. Leggett. U.S. Naval Observatory collaborators are Stephen E. Levine and Ronald C. Stone. The Cornell collaborator is Dae-Sik Moon. David Osip and Joanna E. Thomas-Osip were at MIT and are now at the Carnegie Observatories. John T. Rayner is at NASA’s Infrared Telescope Facility. David Tholen is at the University of Hawaii.

This work is funded by Research Corp., the Southwest Research Institute, the National Science Foundation and NASA.

Original Source: MIT News Release

Beagle 2 Tests Complete

Image credit: ESA

The European Space Agency has been testing all aspects of the Mars Express spacecraft to ensure that it’s ready for its encounter with Mars. This week they put the UK-built Beagle 2 lander through its paces. The tests included uploading software and turning various instruments on and off, and everything seems to be working properly. A final series of tests will be done in mid-July. Mars Express is expected to reach the Red Planet on December 19 – Beagle 2 will land on the surface on December 25.

On Friday 4 July, and Saturday 5 July 2003, engineers successfully carried out overnight tests on the Mars Express lander, Beagle 2.

Ground controllers at the European Space Agency’s Operations Centre in Darmstadt, Germany, contacted Mars Express at the weekend to carry out the tests on the lander, which were rescheduled from two weeks ago. These functional tests included uploading software and switching units on and off.

With these tests, the near-Earth phase of the Mars Express payload check-outs is almost complete. All instruments, including the lander, have performed as expected. Star calibration of some instruments is scheduled for mid-July, which marks the first attempt to make scientific measurements. This will also be done in the same way when nearer to Mars.

Rudi Schmidt, ESA Mars Express Project Manager, said: “This check-out was a marvellous example of complete cooperation between ESA?s Mars Express and the Beagle lander teams Another major milestone has been achieved successfully. What a fantastic feeling!”

Original Source: ESA News Release

Hot Gases Breached a Shuttle Back in 2000

NASA has released photographs that show how the space shuttle Atlantis suffered damage from hot gases back in May 2000 when it returned through the atmosphere on a mission. The damage wasn’t permanent and repaired in time for its next mission four months later. NASA blamed the damage on improper installation of a seal between protective panels on the shuttle’s left wing. Atlantis is expected to be the first shuttle to return to space when NASA begins launches again in early 2004.

X-Prize Entrant Completes Drop Test

Image credit: Armadillo Aerospace

Texas-based Armadillo Aerospace successfully performed a helicopter drop test on a component of their spacecraft on Sunday. Armadillo is just one of the teams competing for the X-Prize, which will pay $10 million to the first private space ship capable of lifting three people to an altitude of 100km. The company is led by John Carmack, who’s better known as the founder of id software – creators of the popular video games Doom and Quake.

We finished up all of the prep work for the vehicle on Tuesday. We welded in strapping points to hold 600 pounds of ?passenger? sandbags in the cabin area, and we mounted five 45 pound Olympic barbell plates on a peg at the end to simulate the weight of the final engines, plumbing, and backup recovery system that will be on the full size vehicle. We mounted four 2? throat engine shells as placeholders. Total weight is just under 2400 pounds. We use a combination of multiple chain hoists, a palette jack, and a forklift to move the full vehicle around and get it up on the trailer, but we did wind up breaking one of the castor wheels that we had mounted on our tank cradle. If we wind up having to use the 1600 gallon propellant tank (the current one is 850 gallons), we aren?t going to be able to stand the vehicle up under the main girder inside our shop, which will be inconvenient.

On Saturday, we headed out to our test site for the drop test. There were quite a few stares on the road in transit? We had a few spatters of rain, and the wind occasionally gusted to 12 knots, but we were able to perform the drop in relatively calm 6 knot winds.

Anna rented a big RV for the day, which was very worthwhile. It was nice to be able to take a break in an air-conditioned space.

5 State Helicopters arrived with a big Sikorsky for the lifting. It was very convenient that they were based close by, and didn?t have a problem with our unusual application (although they did have us contact the local mayor and sheriff for explicit permission). We were very impressed with the precision that they were able to do the lifting ? we were afraid that the vehicle might get dragged or bounced on the crush cone, which could buckle it before the test even started, but they were able to perfectly pivot it up on the nose, and gently lift it off the ground. If we had known they were that precise, we probably could have skipped renting the forklift truck for recovery and just had them lower the rocket back onto the trailer after the test.

We made several 18? diameter test parachutes that were weighted to drift at about the same rate that the full size parachute was expected to fall. We did the test drop from 1500? AGL, under the assumption that the big vehicle would fall several hundred feet before the main chute was fully deployed. The landing point for the test parachute was satisfactory, so we planned the full vehicle drop for 2000? AGL. Neil rode in the helicopter to do the parachute releasing, and Anna hung out the side of the helicopter (with a safety strap) to get aerial footage.

We had to abort our first attempt to drop the vehicle, because the line that we ran from the helicopter to the Sea-Catch toggle release above the rocket had wrapped itself around the chain so many times that Neil couldn?t pull it hard enough to trigger the release. This was fixed by tying loose loops of plastic every few feet along the chain, which kept the pull-line in place.

On the second try, the release worked perfectly. You can clearly see the naturally unstable aerodynamics of the vehicle, as it starts to tip over almost immediately after release. We all held our breath as it started to fall, but the drogue immediately inflated and started pulling the main canopy out. It was nine seconds from release to full canopy inflation. The opening shock was negligible, barely hitting 2G?s. For high altitude flights, we are aiming for a 200 mph terminal velocity under the stabilizer drogue at the time of main canopy deployment, so opening shock will be much greater then.

The wake of the main canopy is so great that the deployment drogue just rests on the canopy during descent, without any inflation at all. The real deployment system will have a much longer line on the drogue (because it is used for vehicle stabilization before deploying the main), which will probably cause it to trail behind the main chute, still inflated.

The drift was going about where we expected, but we were a little concerned when we saw that the vehicle was oscillating +/- 13 degrees under the canopy, which is a pretty big swing at that length. The actual landing point was unfortunately just behind some low foliage, so we didn?t get a perfect shot of it, but we did see it hit at enough of an angle that it rolled almost back upright as it landed.

We ran over to collapse the chute and examine the state of the vehicle. The crush cone had buckled right at the mounting point from the angled impact, but the vehicle looked basically sound. None of the sandbags in the cabin had broken open. Two of the engine support studs were bent from when it tipped back up.

We had the helicopter pick it back up and drop it off by the trailer, which was a lot more convenient than driving the lift truck over to the vehicle.

When we got it back to the shop, we pulled some things apart to take a closer look. The bent mounting studs unscrewed right out of their mounts, so replacing those is trivial. We are considering adding some more bracing below the engine plates, which would probably keep them from bending at all. When we got the crush cone off, we did find that the cabin had been bent right at the end of the cone, and the buckle in the crush cone had pushed in far enough to crease the honeycomb bulkhead.

We are probably going to continue using this cabin for the first couple flights of the big vehicle, but start on a second-generation cabin structure that will incorporate some improvements for off-angle landings, as well as several other lessons we have learned in working with the current cabin. Because we bonded a mounting flange to the tank, we should be able to simply swap the cabin when we want to.

The accelerometer data showed 10G acceleration peaks during the landing and bounce, which is over twice what we saw with the straight down drop tests that collapsed perfectly. This is still acceptable, although bouncing up and back down in the cabin would have been a pretty harsh ride. Making some changes to the vehicle structure will improve the behavior of the crush cone and over tipping effects, and we are going to see if Strong Enterprises can do anything with the canopy design to reduce the oscillations during descent.

Overall, the operation was a good success, and demonstrates that recovering the complete vehicle after flight should work fine.

Original Source: Armadillo Aerospace News Release

Test Blasts a Hole in Shuttle Wing

Columbia accident investigators fired a chunk of foam at a sample wing of the space shuttle on Monday, and managed to knock out a 40 centimetre hole. The investigators believe this is the “smoking gun” that proves how events led to the destruction of the space shuttle in February. The impact was so strong that it damaged some of the sensors designed to measure the damage. The board has already made preliminary recommendations about how NASA can improve its policies to reduce risks to the shuttle in the future, but their full report is due later this month.

Opportunity Blasts Off for Mars

NASA’s second Mars Exploration Rover, Opportunity, successfully lifted off from Florida early Tuesday morning after several delays. The launch was halted only seven seconds away from liftoff during the first window because of a problem with a valve on the rocket, but during the second window at 0318 GMT (11:18 pm EDT Monday) the Delta II successfully blasted off. Opportunity will reach Mars on January 25.

Next Space Tourist Selected

US-based Space Adventures has selected the next tourist who will fly into space on board a Russian Soyuz rocket to visit the International Space Station. Space Adventures won’t reveal the identity of the tourist right now, but he or she is expected to blast off some time in 2004 or 2005. The tourist will next be required to sign a contract with the Russian space agency and pay the $20 million fee. If successful, he or she will become the third space tourist after Dennis Tito and Mark Shuttleworth.