Posted on by Fraser Cain

Giant Jet Streams

Jupiter. Image credit: NASA/JPL Click to enlarge
Turbulence driven by sunlight and thunderstorm activity may explain the multiple east-west jet streams on Jupiter and Saturn and even produce strong winds extending hundreds or thousands of kilometers into the interior, far below the altitudes where the jets are driven.

Scientists have been trying to understand the mechanisms that form the jet streams and control their structure since the first high-resolution images of Jupiter were returned by the Pioneer and Voyager spacecraft in the 1970s.

On Earth, the jet streams — narrow currents of air flowing from west to east in the midlatitudes — form a major component of our planet’s global circulation, and they control much of the large-scale weather experienced by the United States and other countries outside of the tropics. Similar east-west jet streams dominate the circulation of the giant planets Jupiter, Saturn, Uranus, and Neptune, reaching up to 400 miles per hour on Jupiter and nearly 900 miles per hour on Saturn and Neptune. The question of what causes these jet streams and how deep they extend into the interior of the giant planets remain some of the most important unsolved problems in the study of planetary atmospheres.

Adam Showman and Yuan Lian of The University of Arizona in Tucson and Peter Gierasch of Cornell University in Ithaca, New York, explained how cloud-layer turbulence can drive deep jets at the 37th annual meeting of the Division of Planetary Sciences of the American Astronomical Society, held in Cambridge, England.

Lian, Showman, and Gierasch performed computer simulations showing that horizontal temperature contrasts — generated by sunlight or differences in thunderstorm activity — can produce multiple jet streams that penetrate deep into the interior of a giant planet. In the simulations, the temperature contrasts induce deep-penetrating circulation cells that in turn drive the deep jets. The study, which uses an advanced three-dimensional computer model, is among the first that allows an assessment of how jets formed near the top of the atmosphere interact with the interior.

Most planetary scientists have assumed that jets pumped near the top of the atmosphere will remain confined to those shallow layers, and we’ve shown that this is not a valid assumption,” Showman said.

NASA’s Galileo Probe, which parachuted through Jupiter’s atmosphere in 1995, was intended in part to help answer the question of how deep the jet streams extend. The probe found strong winds extending at least 150 kilometers (almost 100 miles) below the clouds. Planetary scientists have widely interpreted this measurement as evidence that the jets are driven from deep inside Jupiter’s interior. The new study challenges this interpretation.

“We still don’t know whether the jets on the giant planets are driven from the top or within the deep interior,” Showman said. “But our study shows that the deep winds measured by the Galileo probe could just as easily result from shallow cloud-layer turbulence as from turbulence deep inside Jupiter’s interior.”

“This result contradicts a long-standing assumption on the part of many planetary scientists.”

The new study also shows that, under realistic conditions, the turbulence can produce not only numerous jet streams but a strong eastward flow at the equator, as observed on Jupiter and Saturn. Such flows are notoriously difficult to produce in atmospheric models, Showman noted.

Original Source: NASA Astrobiology

Posted on by Fraser Cain

The Risk of a Comet Strike is Low

Comet. Image credit: NASA/JPL Click to enlarge
The chances of the Earth being hit by a comet from beyond Pluto ? ? la Deep Impact ? are much lower than previously thought, according to new research by an ANU astronomer.

Using computer simulations and data from an American military telescope, Dr Paul Francis, from the ANU Research School of Astronomy and Astrophysics at Mt Stromlo, has found there are seven times fewer comets in our solar system than previously thought.

?I calculate that small comets, capable of destroying a city, only hit the Earth once every 40 million years or so,? Dr Francis said. ?Big continent-busting comets, as shown in the movie Deep Impact, are rarer still, only hitting once every 150 million years or so. So I don?t lose sleep over it, but you?re still more likely to be killed by a comet than to win the Lotto jackpot.?

Previous estimates of the number of comets were based on the work of amateur astronomers, who for hundreds of years have been scanning the skies, looking for new comets.

Previously, it was believed that these amateur astronomers were only spotting three per cent of the comets passing close to the Earth: the rest were thought to be missed because they were in the wrong part of the sky or were too faint.

But Dr Francis found that the amateurs were doing better than anyone had realised ? they were actually spotting 20 per cent of comets. There are therefore far fewer undiscovered comets.

?The new data allowed us to count the number of faint and far-away comets that the amateurs had missed. And we found that they were pretty rare,? Dr Francis said.

These results apply to comets coming from beyond the orbit of Pluto, which is where most comets live. The Earth is still at risk of being hit by asteroids, and by so-called short-period comets ? ones that come past repeatedly, like Halley?s comet.

?But asteroids and short-period comets come past again and again, so if we?re clever enough we can find them all and predict which, if any, will hit the Earth,? said Dr Francis. ?If we find one on a collision course with the Earth, we would normally have hundreds of years warning in which to do something about it, like deflecting the asteroid.

?The comets coming from beyond Pluto, so called long-period comets, are nastier, as they are totally unpredictable, and if we see one on a collision course we?d have at best one or two years warning ? not long enough to do anything.?

Dr Francis? research has been accepted for publication in the Astrophysical Journal. It was based on computer simulations, published data from the Lincoln Near Earth Asteroid Research Project at White Sands Missile Range in New Mexico, and on data from amateur astronomers around the world.

Original Source: ANU News Release

Posted on by Fraser Cain

Hubble’s View of the Boomerang Nebula

Boomerang Nebula. Image credit: STScI/AURA Click to enlarge
The Hubble Space Telescope has “caught” the Boomerang Nebula in these new images taken with the Advanced Camera for Surveys. This reflecting cloud of dust and gas has two nearly symmetric lobes (or cones) of matter that are being ejected from a central star. Over the last 1,500 years, nearly one and a half times the mass of our Sun has been lost by the central star of the Boomerang Nebula in an ejection process known as a bipolar outflow. The nebula’s name is derived from its symmetric structure as seen from ground-based telescopes. Hubble’s sharp view is able to resolve patterns and ripples in the nebula very close to the central star that are not visible from the ground.

Astronomers are uncertain of the cause of bipolar outflow in this, and many other, young nebulae like the Boomerang. It may be that a disk of slow-moving material is situated around the equator of the star, thereby blocking more rapidly moving ejected material there, and allowing only matter closer to the poles to be ejected. Another consideration may be that magnetic fields are responsible for constraining the material and thus causing the double-lobed shape of the nebula.

Bipolar outflows are seen to occur both from very young stars (“protostars”) that are still in the process of collapsing and forming, and from old stars nearing the ends of their lives that have become bloated red giants. The Boomerang is believed to be the ejected outer layers from an old red giant. Each lobe of the Boomerang Nebula is nearly one light-year in length, making the total length of the nebula half as long as the distance from our Sun to our nearest neighbors- the Alpha Centauri stellar system, located roughly 4 light-years away.

These images of the Boomerang were taken in early 2005 with the Advanced Camera for Surveys onboard Hubble. A visible light filter was used in combination with a series of polarization filters. Similar to polarizing sunglasses that are used to reduce the amount of scattered light that enters our eyes on a sunny day, the telescope’s polarizing filters allow only light of a specific polarization angle to pass through to the camera’s detector. By combining images taken at different polarization angles, astronomers can study light scattering in the nebula and the properties of the small dust particles responsible for the scattering. Colors were assigned to represent different polarization components, and then those colors were adjusted to accentuate features in the nebula, resulting in the multi-hued composite image.

The Boomerang Nebula is located about 5,000 light-years from Earth in the direction of the Southern constellation Centaurus. Submillimeter radio measurements made in 1995 show the deep interior of the nebula to have a temperature of only one degree Kelvin above absolute zero, with absolute zero equal to nearly -460 degrees Fahrenheit. This makes the inner regions of the Boomerang Nebula one of the coldest known places in the universe.

Original Source: Hubble News Release

Posted on by Fraser Cain

Solar Storms Can Shift Dangerous Areas in Space

Astronaut on the Moon surface. Image credit: NASA Click to enlarge
A breakthrough by a team of British, US and French scientists will help protect astronauts, spacecraft and satellites from radiation hazards experienced in space.

Reporting in the journal Nature this week, the team describe how their study of rare and unusual space storms provided a unique opportunity to test conflicting theories about the behaviour of high energy particles in the Van Allen radiation belts* – a volatile region 12000 miles (19,000 km) above the Earth.

Lead author, Dr Richard Horne of the British Antarctic Survey (BAS) says

?Solar storms can increase radiation in the Van Allen belts to levels that pose a threat to spacecraft. As modern society relies increasingly on satellites for business, communications, and security, it is important to understand the environment that spacecraft operate in so that we can help protect our space investment.

?For a long time scientists have been trying to explain why the number of charged particles inside the belts vary so much. Our major breakthrough came when we observed two rare space storms that occurred almost back-to-back in October and November 2003. During the storms part of the Van Allen radiation belt was drained of electrons and then reformed much closer to the Earth in a region usually thought to be relatively safe for satellites.

? When the radiation belts reformed they did not increase according to a long-held theory of particle acceleration. Instead, by using scientific instruments in Antarctica and on the CLUSTER mission satellites, we showed that very low frequency radio waves caused the particle acceleration and intensified the belts.

?This new information will help spacecraft operators and space weather forecasters who must predict when satellites and missions are most at risk from radiation events allowing them to take measures to protect instruments and systems from damage, and astronauts from risks to their health.?

Original Source: BAS News Release

Posted on by Fraser Cain

Progress 19 Brings Spare Parts to the Station

A Progress supply ship. Image credit: NASA Click to enlarge
An unpiloted Russian Progress cargo ship docked to the aft port of the International Space Station (ISS) Zvezda module today at 10:42 a.m. EDT, as the Station flew 220 miles above Central Asia near northern Kazakhstan. The 19th Progress spacecraft to visit the ISS is carrying more than 5,000 pounds of supplies for the crew.

Expedition 11 Commander Sergei Krikalev and Flight Engineer John Phillips will check for leaks before opening the hatch to the Progress later today. They’ll begin unloading the cargo tomorrow.

The supplies include food, fuel, oxygen and air, clothing, experiment hardware, Russian spacesuit components and spare parts for the Vozdukh carbon dioxide removal system. A new water circulation liquids unit is onboard the supply ship. This unit is for the station’s Elektron oxygen-generating system which is inoperable. The unit will be installed next week to try to bring Elektron back into service.

The remainder of the Progress payload includes 1,763 pounds of propellant for the Russian thrusters; 242 pounds of oxygen and air in tanks as a backup supply for the oxygen generated by Elektron; and 463 pounds of water to augment the supplies left by the Space Shuttle Discovery during the STS-114 mission.

Some of the clothing and personal effects delivered to the station include items for the next resident crew, Expedition 12 Commander Bill McArthur and Flight Engineer Valery Tokarev. They are scheduled to launch from the Baikonur Cosmodrome in Kazakhstan Oct. 1 in the Soyuz TMA-7 capsule.

Information about the crew’s activities on board the station, future launch dates, and sighting opportunities is available on the Web at: http://www.nasa.gov/station

Original Source: NASA News Release

Posted on by Fraser Cain

Podcast: The Fate of the Universe

How will the Universe end? Right now cosmologists have two equally distressing scenarios mapped out for the long term fate of the Universe. On the one hand, gravity might slow down the expansion of our Universe so that it coasts to a stop and possibly even collapses back down into a Big Crunch. On the other hand, the expansion of the Universe could continue indefinitely thanks to the acceleration of dark energy. We would face a cold, lonely future as other galaxies fade away into the distance. My guest today is Eric Linder from the Lawrence Berkeley National Laboratory and he’s proposing experiments that could help us learn which of these two fates await us.
Continue reading “Podcast: The Fate of the Universe”

Posted on by Fraser Cain

What’s Up This Week – September 12 – September 18, 2005

The Moon, captured by Apollo 11 astronauts. Image credit: NASA. Click to enlarge.
Monday, September 12 – If you’re up before sunrise this morning, be sure to step outside with a pair of binoculars and check out how close Saturn is to the M44. You should be able to see them both in the same field of view!

Today in 1959, the USSR’s Luna 2 scored a mark as it became the first manmade object to hit the moon. The successful mission landed in the Paulus Putredinus area, and tonight we’ll go there.

The most outstanding feature will be mid-placed Copernicus. Head northeast for Eratosthenes caught on the “tail” of the Apennine Mountains. To the northeast you will see prominent crater Archimedes with smaller craters Aristillus and Autolycus to the east. South of this pair, and caught along the mountain range, you will spy a dark grey, heart-shaped area known as the “Rotten Swamp” – Paulus Putredinus. Apollo 15 landed near Mons Hadley on its northeastern shore, but Luna 2 beat it there. Look at the area between the southern Autolycus and Archimedes. Spaseba!

Before we call it a night, why not point your scope toward the star in the northeast corner of the diamond of Delphinus? Its name is Gamma and it is one of the best double stars in this area for a small optics. Discovered by Struve in 1880, this 100 light year distant pair will show a slight yellow tinge in the fourth magnitude primary, and perhaps a little green in the fifth magnitude secondary. Enjoy it tonight…

Tuesday, September 13 – Today in 1922, the highest air temperature ever recorded at the surface of the Earth occurred. The measurement was taken in Libya burned in at a blistering 136?F, but did you know that the temperatures in the sunlight on the Moon double that? Tonight let’s take a look at a sunlit feature as we head for the bright point of crater Euler.

Beginning towards the north in the mostly disclosed Mare Ibrium region, look for this small, but conspicuous crater near the terminator. Note that it is roughly the same size as its two attendant craters to the east – Lambert and Pytheas, but has a noticeably central peak. If timing is right, you may be able to see the peak of Mons Vinogradov peeking above the terminator to its west.

For viewers in New Zealand, you will have the opportunity to watch the Moon occult Tau Sagittarius on this universal date. Please check this IOTA webpage for details.

If that’s not “hot” enough for you, then take a look straight overhead at brilliant star Vega. It is a “Sirian type” star and with a surface temperature of about 9200 degrees Kelvin, it’s twice as hot as our own Sun. At around 27 light years away, our entire solar system is moving towards Vega at a speed of 12 miles per second, but don’t worry… It will takes us another 450,000 years to get there. If we were to arrive tonight, we’d find that Vega is around 3 times larger than Sol and that it also has a 10th magnitude companion that can often be resolved in mid-sized scopes. It’s one of the first stars to ever be photographed. Back in 1850, that simple star – Vega – took and exposure time of 100 seconds through a 15″ scope. How times have changed!

Wednesday, September 14 – If you have a clear western horizon, take the time after the Sun sets to look at how far the evening planets have now moved apart. With Venus still blazing, Jupiter is becoming harder and harder to spot as it has moved a handspan away to the west. It’s almost gone…

Before we head off into the night, let’s take a look at the lunar surface. While outstanding Gassendi will catch the eye, there are more craters along the shores of Mare Humorum that deserve some attention! South of Gassendi and along the west shore is Class III crater Mersenius. Perhaps the terminator will be dividing it at the time of your viewing at it will appear like a “bite” taken out of the edge. Perhaps it will be well lit and you will see a cruciform structure of mountains and craters. Tonight its features look quite high, but by tomorrow, it will be totally washed out.
Due south of Gassendi across Mare Humorum is Doppelmeyer, who’s eroded walls have left it nothing more than a ghost of its former self – yet you can still see an upsweep in its interior landscape. If skies are stable, power up and see if you can spot Rimae Doppelmeyer to the west or the faded ruins of Puiseux on its eastern flank.

Thursday, September 15 – Head’s up, Eastern Europe! Tonight you have a chance to watch the Moon occult Epsilon Capricornii. Please check this IOTA webpage for details in your area.

Tonight on the lunar surface, we’ll visit the far north as well look towards our guidepost, Sinus Iridum. Head north once again to spot the rather unusual rectangle shape of crater Babbage. This ancient, shallow enclosure has many younger craters within it, and Babbage A will be quite clear. Heading northeast about twice the length of Babbage, you will spot a rather deformed “heart shape” that marks crater Anaximander. This will be part of a group of five overlapping craters, and the name is given essentially to the whole complex. Look for younger crater Carpenter as a black ellipse with a bright border intruding in its walls.

While you’re out, stop to look up at Beta and Gamma Lyrae, the lower two stars in the “Harp”. Beta is actually a quick changing variable which drops to less than half the brightness of Gamma in around 12 days. For a few days the pair will seem of almost equal brightness and then you will notice the star closest to Vega fades away. Beta is one of the most unusual spectroscopic stars in the sky, and it is possible that its eclipsing binary companion may be the prototype of the “collapsar”, (yep. a “black hole”!) rather than a true luminous body.

Friday, September 16 -The Moon rises shortly before Sun sets tonight amidst the difficult to see stars of the constellation Aquarius. Believe it or not, Uranus is only about 3 degrees away, but it will be next to impossible to pick the distant planet out with the lunar glare. So why ignore the Moon? Let’s do some exploring and we can start just as easily as identifying the grey oval of Grimaldi.

Just north of Grimaldi is Class V Hevelius. It will show as a bright oval, similar to Grimaldi, but will contain an off-center mountain peak. Its north wall is broken by Class I Calaverius, a narrow, bright ellipse with a thin, black border to the east. Only 100 kilometers away from here on the edge of Oceanus Procellarum lay the remains of the very first successful lunar landing. It was here on February 3, 1966 that the Soviet probe – Luna 9 – touched down. The man-sized craft sent back panoramic television images to a waiting Earth, revealing the uneven, jagged surface covered with dust. So good were the probe’s images, that scientists were even able to discern small depressions and protrusions only millimeters in size.

Saturday, September 17 – On this day in 1789, Sir William Herschel discovered Saturn’s moon Mimas. And indeed the Moon will be on our mind as tonight is “Harvest Moon”.

At exactly 10:01 p.m. EDT, the Moon will become Full and it will be the closest to the Autumnal Equinox. Because the orbit is more horizontal with the eastern horizon, it will rise a dusk for the next several nights in a row. On the average, the Moon rises about 50 minutes later each night, but at this time of year it’s around 20 minutes later for mid-northern latitudes and even faster farther north. Because of this added extra light, the name “Harvest Moon” came about because it allowed farmers more time to work in the fields.

Often times we perceive the “Harvest Moon” as being more orange than any other time of the year. The reason is not only scientific enough – but true. Coloration is caused by the scattering of the light by particles in our atmosphere. When the Moon is low, like now, we get more of that scattering effect and it truly does appear more orange. The very act of harvesting itself produces more dust and often times that coloration will last the whole night through. And we all know the size is only an “illusion”…

So, instead of cursing the Moon for hiding the deep sky gems tonight, enjoy it for what it is… A wonderful natural phenomena that doesn’t even require a telescope! Is that Mars following behind it?

Sunday, September 18 – If you’re up before dawn this morning, why not take the opportunity to step outside and look at how much the sky has changed. The winter constellation of Orion has now well risen and the harbinger of the Winter – Sirius – has now appeared.

Once again, the Moon will play a major role in tonight’s sky, but why not take the time to enjoy some of its incredible features? With just your eye you can identify Mare Crisium to the northeast, and Mare Fecundatitus to the southeast. Mare Frigorus is the long, dark stretch that runs across the northern section and the expanse of Mare Ibrium and Oceanus Procellarum dominate the northwest quadrant. Can you spot the dark oval of Mare Humorum to the southwest or Nubium to its east?

Those of you with sharp eyes might be able to make out the small dark oval of crater Plato to the north or Grimaldi to the west. Can you see the bright point of Tycho? Just north of central is the very round, grey Mare Serenitatis and south of it, Mare Tranquillitatis. Using binoculars, trace out the bright rays of Proculus in the east and Tycho to the south. Aristarchus and Kepler shine like beacons in the northwest and while the southwest is far more muted, look for the bright point of Euclides.

Hang tough. A few more days and darker skies will be on our side! Until then? May all your journeys be at light speed…. ~Tammy Plotner

Posted on by Fraser Cain

Join the Bad Astronomy/Universe Today BOINC Team

Several years ago, scientists at University of California, Berkeley came across a situation in which more data was being gathered by a radio telescope than could be analyzed by any single computer. The solution to this problem was to use the idle time of personal computers all around the world. This resulted in the creation of SETI@Home, a downloadable application that would do some calculations on a very small piece of the gathered data. The results would then be returned to SETI@Home’s servers to be combined back with results from other computers all around the world. This later branched into BOINC, a project that allows one to choose from multiple projects such as SETI@Home and run many projects on one computer. The user can even allot how much time is spent on each project. BOINC runs at a low priority on one’s computer, which means when other programs (Word, Internet Explorer, etc.) request the processor, BOINC hands it over and allows the program to do as it wishes. When the program is done, BOINC picks up where it left off.

The Bad Astronomy/Universe Today forum currently has a team for four of the BOINC projects. The team is named BABB, but that will soon change when the BAUT forum name is finalized. The name will change to reflect the BAUT name. Though the team is named after the forum, those who are not a part of the forum are welcome to join.

The Einstein@Home project searches for spinning neutron stars known as pulsars by searching for gravity waves in data from the LIGO and GEO gravitational wave detectors. Anyone wishing to sign up for Einstein@Home can do so here and can sign up for the Bad Astronomy/Universe Today team by clicking join here.

The LHC@Home project allows for the simulation of a particle travelling through a large particle accelerator that is due to be completed by 2007 by CERN known as the LHC (Large Hadron Collider). Anyone wishing to sign up for Einstein@Home can do so here and can sign up for the Bad Astronomy/Universe Today team by clicking join here.

The SETI@Home project searches for evidence of extraterrestrial intelligence through radio waves received from the Arecibo Observatory. Anyone wishing to sign up for SETI@Home can do so here and can sign up for the Bad Astronomy/Universe Today team by clicking join here.

The orbit@home project will take data from observations of asteroids and calculate their orbits. This will assist in the search for any asteroids in an eventual collision course with the Earth, as well as catalogue the orbits of the asteroids. This project is not running yet, but soon will be in the test phase. Member creation is shutdown for the time being. The project will have to be tested for a while before it goes online.

The team has a web page and member stats. Any questions regarding this project can be asked at this thread on the BAUT forum or sent to [email protected].

Posted on by Mark Mortimer

Book Review: Voyages to the Stars and Galaxies

Texts on general courses need to fulfill two goals; they must explain the details, and they must capture the imagination. Those contemplating sticking their toe into the pool of astronomy could understandably get nervous. This field has contributions made from most of the greatest thinkers of our species. In addition, our primitive five senses are woefully inadequate to peel back the shrouds of astronomical mystery. Today, professionals tell tales of trying to contact aliens, go through a spacetime continuum, or detect dark energy. They rely on state-of-the-art technology using ultimate processing power and quirky algorithms to make sense of what the uninitiated would consider random patterns. Yet, in starting from the beginning and keeping the information succinct, an introductory text can supply adequate elucidation and perhaps entice another neophyte to continue past the general level.

The team of Fraknoi, Morrison and Wolff, in their textbook, meet both these goals. For astronomy, they offer completeness. To start, there’s the perspective of astrology based solidly in history. Then they proceed down the chronological path bringing in each contributor and the significant contributions. Orbits, geocentricity, eclipses and tides lay the ground work. However, the text quickly proceeds to the electromagnetic spectrum, radio telescopes, nuclear chemistry and the basis of today’s observation, that is, star types, distances and life attributes. The end brings the reader to current perceptions on relativity, cosmology, and astrobiology. There is no doubt that the authors explain the details, though for the most part they focus on data rather than on rationale.

Trying to capture an imagination without knowing the person is much more nebulous a task. Clearly, the authors assume the reader has no technical background. The powers of ten mathematics notation is the most complex math and has two solid descriptions, one in the text and the other in the appendices. Photographs, diagrams, historical vignettes and charts ease the way forward for those not used to contemplating quantitative descriptions. Analogies appear throughout. For example, did you know the density of a neutron star is similar to squeezing all the people on Earth into the volume of a single rain drop? Lastly, the accompanying CD, with the student edition of The Sky, gives many opportunities to take the data in the text and compare it to night time observations for any latitude or longitude within a time of 10 000 years. If the student truly has interest in astronomy, then this text should capture their imagination, at least until the end of the course.

As a text, this book aims solidly for course work. Each significant subject of astronomy has its own chapter. The chapter layout starts with the history, emphasizing the practitioners, next the current activity emphasizing the equipment, and then ends with expectations emphasizing the research thrusts. At the conclusion of each chapter, a summary, list of group activities, review questions and contemplative questions provide lots of study material. In a unique step, the authors have set up an adoption program whereby they keep all registered users up to date on new material. They also have a help hot line (actually email line) where they promise to quickly answer any (student or lecturer) question regarding this course work.

Given that this version is the third edition, it should and does flow smoothly. Chapters stand on their own. Different styles emerge, likely due to the different authors, but no problems result. The information is current, though it can be necessarily vague, such as the topic on our universe’s size. Also, like most texts, the contents revolves around data and is perfect for digesting and regurgitation. The sparse amount of theory is appropriate for a general introductory text.

September is the time for school and the show of Sagittarius in the night sky. School has surprises but so does Sagittarius. Did you know that within the boundaries of this constellation there lies a galaxy that’s about to get eaten up by our own Milky Way? Read the book Voyages to the Stars and Galaxies by Andrew Fraknoi, David Morrison, and SidneyWolff to learn about the constellations, stars and their marvellously unique and sometimes hungry properties. Anthropic or not, you’ll see that we’re in one amazing universe.

Review by Mark Mortimer

Read more reviews online, or purchase a copy from Amazon.com.

Posted on by Fraser Cain

Audio: The Fate of the Universe

The SuperNova/Acceleration Probe, SNAP. Image credit: Berkeley Lab Click to enlarge
Listen to the interview: The Fate of the Universe (6.2 MB)

Or subscribe to the Podcast: universetoday.com/audio.xml

Fraser Cain: Can you lay out the two fates that may await our Universe?

Eric Linder: Well, our picture of what the fate of the Universe is has really changed dramatically in the last 5-10 years. We used to think it was fairly simple, it was just a matter of how much content there was in the Universe, how much matter there was. If there was enough matter, then the gravitational attraction would cause the Universe to slow down in its current expansion, and to basically re collapse and we’d have what some people call a Big Crunch to end our Universe. And if there was not enough matter, there would not be enough gravity to slow down the current expansion and it would just become more and more diffused – a colder and lonelier place to live in. In 1998, these two groups of scientists discovered a very bizarre occurrence that the expansion of the Universe was not slowing down either dramatically or even gradually, under the gravity of the matter in the Universe, but rather, it was speeding up. It was accelerating. Sort of like if you threw a baseball up in the air you know eventually it’s going to slow down, reach a peak, and usually come down back to Earth. If you throw it hard enough, it’ll go off into orbit. But here the Universe threw a baseball up in the air, and now that baseball is speeding away faster and faster. So this has completely puzzled scientists, and was completely contrary to what we were expecting. Under this new picture, the fate of the Universe appears to be that it is going to simply expand forever and ever, become colder, more diffuse, atoms will get more and more spread out, the distance between galaxies will increase. And we’ll have this fate of the Universe which is sometimes called the “Heat Death”, where everything just becomes very cold and motionless and isolated from each other.

But it depends on what’s causing this acceleration. That’s the great mystery. It’s possible that the physics giving us this acceleration could suddenly go away, in which case we’d be back to the earlier picture where the Universe might collapse. Or it could do something completely bizarre and we don’t know. So this is a big question that we want to find out. What is the fate of the Universe, but trying to figure out, what is the physics in this acceleration.

Fraser: Why has that question not been answered so far? Have we not gotten a good enough look at the supernovae?

Linder: Right, as I said, the acceleration of this expansion was only discovered in 1998. And people haven’t been sitting on their hands, they’ve been trying to answer this question very passionately. By getting more supernovae, we can use these exploding stars sort of like fireworks off in the Universe. If we know that the fireworks always go off with the same energy, with the same brightness, we can tell how far away they are by how bright they appear to us today. And so we need more of these supernovae, and we need more and more distant ones, so we can map the history of the Universe; the expansion of the Universe over a greater period of time. And people are gradually doing that. There are some very large projects underway with telescopes on the ground attempting to get what were just tens of supernovae, now we’re trying to get hundreds of supernovae. But eventually, to really answer these fundamental questions, we’re going to need thousands of supernovae at great distances. In order to get that, we’re going to need observations from space, so currently we have one space telescope – the Hubble Space Telescope – that is suitable for these sort of observations, and it’s doing a great job. It’s seeing the most distant supernovae that we’ve yet discovered; about 10 billion years out in the history of space, but it can only see them one by one. And so what scientists have proposed is that we build a new space observatory, a new telescope in space, called SNAP (Supernova Acceleration Probe), and this will be able to get thousands of supernovae very efficiently, very rapidly, seeing them extremely faint and extremely deep. And this has really caught the imagination of the science community. There have been a number of recommendations from the National Academy of Sciences, from various professional organizations, that some sort of space observatory like this will figure out: what is this mysterious physics causing this completely unusual acceleration that’s acting opposite to gravity? So there’s almost like a repulsive version of gravity that’s really going to rewrite all the physics textbooks. So a lot of people think that we really do need to go forward with these observations, more precise observations and many more observations, such as you spoke about. We just need to improve the data that we already have, and the technology is good enough that we can go out and do this. It just requires us to sit down and build the thing, and launch it and try to find out these answers.

Fraser: Now I’ve heard quite a few suggestions for what this dark energy might be. What kinds of things would you be looking for in your observations that could maybe map against some of those theories that have been put forward?

Linder: So the granddaddy of all concepts of dark energy was put forward by Albert Einstein all the way back in 1917, what he called the cosmological constant. And it didn’t agree with the observations at the time, and so it kind of went into retirement for a while. And every few decades, scientists brought it back out to say, well maybe that could explain some other observations we’ve made. And then it goes back into retirement because it doesn’t really fit. But now it seems this might be its time, to bring back this 90 year old concept from Einstein, because it can give this acceleration of the expansion of the Universe. It’s a very simple picture for how you could get this acceleration, but it doesn’t solve everything. There are some really very puzzling aspects of it. What you would think if you did some naive calculations is that it should accelerate the Universe, but should have started accelerating the Universe all the way back from the very first instant of time, and we would not have the Universe we see today if that happened. In fact, we would not have been able to get stars and galaxies and the structure that we see in the Universe. And so for some reason there has to be much much weaker than we would think as its natural value. So it’s possible that it’s the answer, but we don’t understand why it’s so weak, relative to what we think it should be. To get around that, people come up with these other ideas, this idea of quintessence, or a 5th substance to the Universe where it acts like the cosmological constant, but it varies in time, and so it can start off very weak and now today it can be dominating the expansion of the Universe. And so that’s an attractive idea, but nobody really has any first, basic idea of how to make it work exactly. Right now it’s a concept but the details haven’t been worked out on how it arises from the physics. So that’s another thing that we can be very interested in. Another possibility is the way we’ve been analyzing the data, saying, well, gravity is an attractive force, it’s given by Einstein’s Theory of General Relativity. Maybe something breaks down there. Maybe what we’re seeing is a breakdown in the theory of gravity as we understand it. People have come up with ideas that involve extra dimensions for example. Instead of just three dimensions in space, there might be an extra few dimensions in space, and that gravity is gradually sort of leaking out into this extra dimension in space and that’s making it weaker and that will act in opposition to gravity and give us acceleration. So we have all these incredibly exciting possibilities for how physics might change and we don’t know which they are. And so what we need are these very detailed observations of mapping the expansion of the Universe for example through the supernovae, these exploding stars – and there are other methods as well – to really try and decide, how are we going to rewrite the physics textbooks; which direction do we need to start erasing things in and writing new things in. So, it’s incredibly exciting for scientists who have puzzles facing them like this.

Fraser: When are these missions planned for launch? When should they be operational?

Linder: So NASA and the US Department of Energy have agreed to work together to put a mission into orbit. The general name for it is called the Joint Dark Energy Mission. And there are currently studies going on for how one would design such a space telescope. And we’re hoping that if enough public shows a strong interest, and the professional societies – like the National Academies of Sciences, which recommended such a mission. If they continue to support this, then we hope that we can go forward and launch it within about 6-7 years. So it’s very much possible that the students in school now will know the answers to things in 6-7 years that currently no professional scientist has the slightest clue for what the answer is. So it’s always very exciting to be able to tell students, and to be able to tell the public: you’re going to know things 6-7 years from now that we have no idea what the answer is right now. You’re going to be smarter in 6 or 7 years than we are right now. So it’s really an exciting endeavour to be in the middle of.

Fraser: And if you had your way, would it be fiery hot death, or cold freezing death?

Linder: I think the main thing I’d like is that it be far off. So we know the ends of the Universe are not going to be for at least 10s of billions of years – about the length of time that we’ve already had in the Universe – so it’s nothing we have to be concerned with overnight, but I don’t know what would be the best solution. You could argue that something like an overturning of Einstein’s Theory of Gravity and just a completely new framework of physics, and new territory to explore. That might be the most exciting outcome where you might have all sorts of different possibilities arising. But as you allude to, the fate of the Universe that really grabs our imagination, of everyone, from the scientists to school children.