Posted on by Ian O'Neill

The “Astronomical Unit” May Need an Upgrade as the Sun Loses Mass

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The Sun is constantly losing mass. Our closest star is shedding material through the solar wind, coronal mass ejections and by simply generating light. As the burning giant begins a new solar cycle, it continues to lose about 6 billion kilograms (that’s approximately 16 Empire State Building’s worth) of mass per second. This may seem like a lot, but when compared with the total mass of the Sun (of nearly 2×1030 kilograms), this rate of mass loss is miniscule. However small the mass loss, the mass of the Sun is not constant. So, when using the Astronomical Unit (AU), problems will begin to surface in astronomical calculations as this “universal constant” is based on the mass of the Sun…

The AU is commonly used to describe distances within the Solar System. For instance, one AU is approximately the mean distance from the Sun to Earth orbit (defined as 149,597,870.691 kilometres). Mars has an average orbit of 1.5AU, Mercury has an average of about 0.4AU… But how is the distance of one AU defined? Most commonly thought to be derived as the mean distance of the Sun-Earth orbit, it is actually officially defined as: the radius of an unperturbed circular orbit that a massless body would revolve about the Sun in 2Ï€/k days (that’s one year). There lies the problem. The official calculation is based on “k”, a constant based on the estimated constant mass of the Sun. But the mass of the Sun ain’t constant.

As mass is lost via the solar wind and radiation (radiation energy will carry mass from the Sun due to the energy-mass relationship defined by Einstein’s E=mc2), the value of the Astronomical Unit will increase, and by its definition, the orbit of the planets should also increase. It has been calculated that Mercury will lag behind it’s current orbital position in 200 years time by 5.5 km if we continue to use today’s AU in future calculations. Although a tiny number – astrophysicists are unlikely to lose any sleep over the discrepancy – a universal constant should be just that, constant. There are now calls to correct for this gradual increase in the value of the AU by discarding it all together.

“[The current definition is] fine for first-year science courses. But for scientific and engineering usage, it is essential to get it right.” – Peter Noerdlinger, astronomer at St Mary’s University, Canada.

Correcting classical “constants” in physics is essential when high accuracy is required to calculate quantities over massive distances or long periods of time, therefore the AU (as it is currently defined) may be demoted as a general description of distance rather than a standard scientific unit.

Source: New Scientist

Posted on by Ian O'Neill

Ulysses Passes Over Sun’s North Pole

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Continuing on its epic journey around the Sun, Ulysses has reached the Sun’s north pole just in the nick of time. In fact, its timing couldn’t be better, just as the Sun begins “Solar Cycle 24”. The probe is in a unique orbit, passing over the solar north and south poles, out of the ecliptic plane of the solar system, giving it an unprecedented view of parts of the Sun we cannot observe on Earth. “Graveyards for sunspots” and mysterious coronal holes lurk in these regions and Ulysses will be perfectly placed, directly above.

The joint NASA and ESA Ulysses mission has been a resounding success in its 18 years of operation since launch on board Space Shuttle Discovery (STS-41) in October 1990. The intrepid spacecraft was helped on it’s way by a gravitational assist by the planet Jupiter which flung it over the poles of the Sun. Quietly travelling in a perpendicular orbit (space missions and the planets usually orbit around the Sun’s equator), Ulysses has been measuring the distribution of solar wind particles emanating from latitudinal locations for one and a half orbits.

As Ulysses passes over the north polar region, the Sun will be observed during a period of minimum activity at this location for the first time. The poles of the Sun are of particular interest to scientists as this is where the fast solar wind originates from open magnetic field lines reaching into space. The dynamics of solar material in this location provides information on how the Sun interacts with interplanetary space and how the solar wind is generated. Observing the solar wind at “solar minimum” will be of massive interest as it may provide some answers as to why the solar wind is accelerated hundreds of kilometers per hour even when activity is at its lowest.

“Just as Earth’s poles are crucial to studies of terrestrial climate change, the sun’s poles may be crucial to studies of the solar cycle.” – Ed Smith, Ulysses project scientist, NASA Jet Propulsion Laboratory.

The dynamics of low altitude magnetic fields in polar regions are also a focus for interest. As 11-year solar cycles progress, sunspot population increase near the solar equator. As the magnetic field is “wound up”, sunspots (and their associated magnetic flux) drift toward the poles where they slowly disappear as the old magnetic field sinks back into the Sun, quite accurately described as sunspot graveyards. Understanding how this cycle works will help to reveal the secrets of the solar cycle and ultimately help us understand the mechanisms behind Space Weather.

Source: NASA Featured News

Posted on by Ian O'Neill

SoHO Celebrates its 12th Birthday

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On December 2nd, 1995 a large joint ESA and NASA mission was launched to gain an insight to the dynamics of the Sun and its relationship with the space between the planets. 12 years on, the Solar and Heliospheric Observatory (SoHO) continues to witness some of the largest explosions ever seen in the solar system, observes beautiful magnetic coronal arcs reach out into space and tracks comets as they fall to a fiery death. In the line of duty, SoHO even suffered a near-fatal shutdown (in 1998). As far as astronomy goes, this is a tough assignment.

By the end of 1996, SoHO had arrived at the First Lagrange Point between the Earth and the Sun (a gravitationally stable position balanced by the masses of the Sun and Earth, about 1.5 million km away) and orbits this silent outpost to this day. It began to transmit data at “solar minimum”, a period of time at the beginning of the Solar Cycle, where sunspots are few and solar activity is low, and continues toward the upcoming solar minimum after the exciting firworks of the last “solar maximum”. This gives physicists another chance to observe the majority of a Solar Cycle with a single observatory (the previous long-lasting mission was the Japanese Yohkoh satellite from 1991-2001).

On board this ambitious observatory, 11 instruments constantly gaze at the Sun, observing everything from solar oscillations (“Sun Quakes�), coronal loops, flares, CMEs and the solar wind; just about everything the Sun does. SoHO has become an indispensable mission for helping us to understand how the Sun influences the environment around our planet and how this generates the potentially dangerous “Space Weather�.

The SoHO mission site confidently states that SoHO will remain in operation far into the next Solar Cycle. I hope this is the case as the new Hinode and STEREO probes will be good company for this historic mission.

Source: NASA News Release

Posted on by Ian O'Neill

Hinode Discovers the Sun’s Hidden Sparkle

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Blinking spots of intense light are being observed all over the lower atmosphere of the Sun. Not just in the active regions, but in polar regions, quiet regions, sunspots, coronal holes and loops. These small explosions fire elegant jets of hot solar matter into space, generating X-rays as they go. Although X-ray jets are known to have existed for many years, the Japanese Hinode observatory is seeing these small flares with unprecedented clarity, showing us that X-ray jets may yet hold the answers to some of the most puzzling questions about the Sun and its hot corona.

Although a comparatively small mission (weighing 875 kg and operating just three instruments), Hinode is showing the world some stunning high resolution pictures of our nearest star. In Earth orbit and kitted out with an optical telescope (the Solar Optical Telescope, SOT), Extreme ultraviolet Imaging Spectrometer (EIS) and an X-Ray Telescope (XRT), the light emitted from the Sun can be split into its component optical, ultraviolet and X-ray wavelengths. This in itself is not new, but never before has mankind been able to view the Sun in such detail.

It is widely believed that the violent, churning solar surface may be the root cause of accelerating the solar wind (blasting hot solar particles into space at a mind-blowing 1.6 million kilometers per hour) and heating the million plus degree solar atmosphere. But the small-scale processes close to the Sun driving the whole system are only just beginning to come into focus.

Up until now, small-scale turbulent processes have been impossible to observe. Generally, any feature below 1000 km in size has remained undetected. Much like trying to follow a golf ball in flight from 200 meters away, it is very difficult (try it!). Compare this with Hinode, the same golf ball can be resolved by the SOT instrument from nearly 2000 km away. That’s one powerful telescope!

The limit of observable solar features has now been lifted. The SOT can resolve the fine structure of the solar surface to 180 km, this is an obvious improvement. Also, the EIS and XRT can capture images very quickly, one per second. The SOT can produce hi-res pictures every 5 minutes. Therefore, fast, explosive events such as flares can be tracked easier.

Putting this new technology to the test, a team led by Jonathan Cirtain, a solar physicist at NASA’s Marshall Space Flight Center, Huntsville, Alabama, has unveiled new results from research with the XRT instrument. X-ray jets in the highly dynamic chromosphere and lower corona appear to occur with greater regularity than previously thought.

X-ray jets are very important to solar physicists. As magnetic field lines are forced together, snap, and form new configurations, vast quantities of heat and light are generated in the form of a “microflare”. Although these are small events on a solar scale, they still generate huge amounts of energy, heating solar plasma to over 2 million Kelvin, create spurts of X-ray emitting plasma jets and generate waves. This is all very interesting, but why are jets so important?

The solar atmosphere (or corona) is hot. In fact, very hot. Actually, it is too hot. What I’m trying to say is that measurements of coronal particles tell us the atmosphere of the Sun is actually hotter than the Suns surface. Traditional thinking would suggest that this is wrong; all sorts of physical laws would be violated. The air around a light bulb isn’t hotter than the bulb itself, the heat from an object will decrease the further away you measure the temperature (obvious really). If you’re cold, you don’t move away from the fire, you get closer to it!

The Sun is different. Through interactions near the surface of the Sun between plasma and magnetic flux (a field known as “magnetohydrodynamics” – magneto = magnetic, hydro = fluid, dynamics = motion: “magnetic-fluid-motion” in plain English, or “MHD” for short), MHD waves are able to propagate and heat up the plasma. The MHD waves under scrutiny are known as “Alfvén wavesâ€? (named after Hannes Alfvén, 1908-1995, the plasma physics supremo) which, theoretically, carry enough energy from the Sun to heat the solar corona hotter than the solar surface. The one thing that has dogged the solar community for the last half a century is: how are Alfvén waves produced? Solar flares have always been a candidate as a source, but observation suggested that there wasn’t enough flares to generate enough waves. But now, with advanced optics used by Hinode, many small-scale events appear to be common… bringing us back to our X-ray jets…

Previously, only the largest X-ray jets have been observed, putting this phenomenon at the bottom of the priority list. NASA’s Marshall Space Flight Center group has now turned this idea on its head by observing hundreds of jet events each and every day:

“We now see that jets happen all the time, as often as 240 times a day. They appear at all latitudes, within coronal holes, inside sunspot groups, out in the middle of nowhere–in short, wherever we look on the sun we find these jets. They are a major form of solar activity” – Jonathan Cirtain, Marshall Space Flight Center.

So, this little solar probe has very quickly changed our views on solar physics. Launched on September 23, 2006, by a consortium of countries including Japan, USA and Europe, Hinode has already revolutionized our thinking about how the Sun works. Not only looking deep into the chaotic processes in the solar chromosphere, it is also finding new sources where Alfvén waves may be generated. Jets are now confirmed as common events that occur all over the Sun. Could they provide the corona with enough Alfvén waves to heat the Sun’s corona more than the Sun itself? I don’t know. But what I do know is, the sight of solar jets flashing to life in these movies is awesome, especially as you see the jet launch into space from the original flash. This is also a very good time to be seeing this amazing phenomenon, as Jonathan Cirtain points out the site of solar jets reminds him of “the twinkle of Christmas lights, randomly oriented. It’s very pretty”. Even the Sun is getting festive.

Posted on by Nicholos Wethington

Cancer Rates Rise and Fall with Cosmic Rays

Showers of high energy particles occur when energetic cosmic rays strike the top of the Earth's atmosphere. Cosmic rays were discovered unexpectedly in 1912. Illustration Credit: Simon Swordy (U. Chicago), NASA.

Cancer is a mysterious and complicated disease, with many different types and causes. Researchers are still trying to track down all of the environmental effects that can lead to the disease, as anything from what someone eats to where they live determines the probability of developing cancer. A paper published in 2007 in the International Journal of Astrobiology looked at data for cancer deaths from around the world for the past 140 years, and found a strong correlation between rises in cancer deaths and the variation over time in the amount of galactic cosmic rays we encounter here on Earth.

In a paper titled, Correlation of a 140-year global time signature in cancer mortality birth cohorts with galactic cosmic ray variation by Dr. David A. Juckett from the Barros Research Institute at Michigan State University, he showed that the amount of deaths due to cancer on a global scale was higher when the background cosmic rays originating from outside the Solar System were more numerous.

The study looked at available cancer death data from the United States, United Kingdom, Australia, Canada and New Zealand for the past 100-140 years. These data were compared with the amount of variations in galactic cosmic rays during the same period, taken from analysis of ice core samples from Greenland and Antarctica.

Dr. Juckett showed that as the amount of cosmic ray activity increased, the number of people who died from cancer was also higher. There are two peaks in cosmic ray activity during this point, around 1800 and 1900, and a low point around 1860. The total deaths due to cancer were highest, though, around 1830 and 1930, and lowest in the 1890’s.

There is a 28-year lag between the increased presence of cosmic rays and the increase in cancer deaths. It’s not so simple as a person being exposed to cosmic rays and then developing cancer immediately afterwards. What is called the “grandmother effect” comes into play; the cosmic rays actually damage the germ cells of one’s parent while that parent is still in the grandmother’s womb.

“The grandmother would have to be exposed to radiation – which she is all the time – while she is pregnant with the mother of the affected individual. What this is basically implying is that, during a sensitive time in pregnancy, the constant background radiation may cause a chemical change in just the right cell and DNA stretch to lead to future cancer. The background radiation is causing very low level damage all the time to random cells in the body, but anything significant happening to germ cells would lead to a whole organism eventually carrying that damage (or predisposition),” said Dr. Juckett.

So, the parent is exposed to cosmic rays while the fetus is still developing, and this damage then emerges as cancer in child, but is not passed down further.

Galactic cosmic rays consist of high-energy radiation, and are composed primarily of high-energy protons and atomic nuclei. Their origin in not fully understood, but are thought to possibly come from supernovae, active galactic nuclei, quasars and/or gamma ray bursts.

There are several factors that may contribute to the flux of cosmic rays, and they may produce showers of secondary particles that penetrate and impact the Earth’s atmosphere and sometimes reach the surface.

In the study, the researchers found the trend between cosmic ray increase and cancer death increase was a global effect, but there are places on the Earth where the magnetosphere blocks more of the cosmic rays than others. At about 10°N of the equator, fewer cosmic rays get through than elsewhere on the Earth because of the way the Earth’s magnetosphere blocks energetic particles.

People in more northern and southern latitudes are exposed to more of this radiation, thus the rates of cancer death were higher in these regions than near the equator. On average, the oscillation in cancer deaths was between 10-15% during the period of the study.

Any good scientist will tell you that correlation does not necessarily mean causation; the increase in cosmic rays matches well the increase in cancer deaths over this time period, but there could yet be other reasons for this increase.

Dr. Juckett cautions, “Of course, other explanations could be hypothesized. Standard epidemiological approaches would partition individual cases by risk factors (e.g., smoking, environment pollution, diet, age-at-menarche, family history, etc.). Only when there is no correlation to these would other hypotheses, like cosmic rays be entertained. Unfortunately, to look at the 100-yr data for long-term trends, this kind of information is generally not available. The one thing that seems certain is that the common oscillations in the US, UK, CA, NZ, and AU data suggest a global environmental signal of some kind. This does limit things a bit (e.g., solar radiation effects, cosmic ray effects, global pollution).”

The effects that cosmic rays and other types of radiation have on human beings are important to study, as we venture outside the protective magnetic field of the Earth into space. The researchers said that “this effect has profound implications for evolution, long-distance space travel and the colonization of planets with high background radiation.” Long journeys in space would expose astronauts to this same type of radiation for long periods of time, so taking precautions to protect them makes good sense.

What can one do to protect themselves from this type of radiation here on Earth?

“I cannot of think of anything one can do to protect themselves from their inherited propensities. However, cancer is a multi-step process. It still requires other random ‘mutations’ to occur during life. Healthy living is still called for. In other words, reducing exposure to toxins, radiation, and injury. Eventually, the biochemical fingerprints of possible inherited changes may be deciphered and then testing could be possible,” said Dr. Juckett.

There is no cause for alarm, though; cosmic rays are only about 20-30% of the background radiation we are exposed to every day, and are a minimal cause of cancer in comparison to other environmental effects such as smoking.

Original Source: International Journal of Astrobiology

Posted on by Fraser Cain

Comet Holmes is Bigger than the Sun

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All right, that title is a little misleading. In fact, when I first read the original press release, my skepticism alarms went off. But it’s true, the amazing Comet Holmes now has a halo that’s larger than the Sun. Not bad for a comet that, until three weeks ago, was just a tiny dim dirty snowball orbiting near Jupiter.

Comet Holmes made its spectacular outburst on October 24, 2007. Formally dim enough to only be visible in the most powerful telescopes, it quickly brightened up to be seen with the unaided eye – even in light-polluted cities (like my very own Vancouver).

Astronomers from the University of Hawaii’s Institute for Astronomy recently measured the halo surrounding Comet Holmes to be 1.4 million kilometres (0.9 million miles). And as I mentioned in the opening paragraph, that makes it larger than the Sun. Of course, it’s just a thin halo of gas and dust particles, but still, that’s pretty impressive.

Just to get a sense of the change, Holmes has brightened by a factor of 500,000x. All this gas and dust is pouring out of a tiny nucleus only 3.6 km (2.2 miles) in diameter.

In the image captured by the Institute for Astronomy, you can make out the brighter nucleus, near the centre of the halo. And then there’s a hazy tail pointing towards the lower right of the image.

Over the next few months, astronomers predict the cometary halo will expand even larger; although, it will be fading away as the dust disperses over a larger volume.

Holmes performed a similar outburst back in 1892, and it brightened again just a couple of months later. Astronomers are hoping it’ll make another double outburst, just like it did before.

Original Source: IfA News Release

Posted on by Fraser Cain

Video of the Sun, Thanks STEREO

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Well, this is one of the coolest things I’ve seen all week. NASA released a new video of the Sun, captured by the twin STEREO spacecraft. The video, in Quicktime format, covers 2.5 days of the Sun, and shows it slowly rotating, with solar prominences blasting out into space.

If you want to just cut straight to the video, check it out here.

The series of images were captured by STEREO from August 16-18, 2007, and then stitched together into a single animation. The prominences that you see on the edges of the Sun were captured in extreme ultraviolet light by the Ahead spacecraft (the one leading the Earth in orbit). And if you watch right to the end, you’ll see a prominence on the upper side arch away into space.

Just amazing to watch.

Click here to watch the video.

Just in case you need a reminder, NASA’s STEREO mission is a set of twin solar observing spacecraft. One is leading the Earth in our orbit around the Sun, and the other is trailing behind us. Because of their different points in space, they’ll be able to create a 3-dimensional view of events on the Sun’s surface – just in the same way your eyes give you depth perception. They launched in October, 2006 on board a Delta II rocket.

One of the best uses of this binocular vision will be to trace the path of coronal mass ejections; especially the ones headed towards Earth. With STEREO, astronomers will be able to know right away if a CME is headed our way, and can help power companies and satellite operators prepare for some rough space weather. And they’ll be able to give us a better idea of when to head outside and see an aurora.

I think this mission is going to be one of the surprising hits for astronomy fans. Make sure you get a pair of 3-D glasses to really enjoy some of the STEREO movies.

Original Source: NASA STEREO Site

Posted on by Fraser Cain

The Sun Isn’t Responsible for Climate Change

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I recently wrote an article for Wired Science about how there doesn’t appear to be a link between cosmic rays and global warming. Now another argument against human-created global warming has fallen to the wayside: increasing temperatures from the Sun.

It turns out energy output from the Sun has actually been decreasing over the last two decades. And during this period, temperatures across the planet have been steadily rising.

The research was published in the Royal Society’s journal Proceedings A, entitled Recent oppositely directed trends in solar
climate forcings and the global mean surface air temperature. The report covers not only trends in solar output, but also deals with decreasing trends in cosmic rays as well.

The Sun varies on an 11-year cycle between periods of high and low activity. But above this, there’s a longer term trend. For most of the 20th century, output from the Sun was slowly and steadily rising. But in 1985, that trend reversed, with solar output slowly declining. Global temperatures here on Earth continued climbing, unaffected.

If it’s not the Sun, and it’s not cosmic rays, what’s left? Oh right… humans.

Original Source: Royal Society journal Proceedings A

Posted on by Fraser Cain

Astronauts Will Get Some Warning When the Space Storm’s Coming

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One of the great risks of space travel is the threat from solar radiation storms. An unlucky group of astronauts traveling to the Moon could get caught unprotected as a hail of charged particles and radiation blast through the spacecraft. But now NASA researchers think the Solar and Heliospheric Observatory (SOHO) will be able to give astronauts some warning before the big storm hits.

SOHO is normally used for scientific observations of the Sun. But it’s equipped with an instrument called the Comprehensive Suprathermal and Energetic Particle Analyzer (COSTEP), which counts particles coming from the Sun, and measures their energies.

One of the main predictors are electrons, which aren’t dangerous in themselves, but are the first wave of a coming storm. The electrons are lighter than the other particles, so they’re carried out ahead of the heavier, and more dangerous particles. By analyzing hundreds of solar storms, the researchers were able to match electrons with a predicted density of ions.

When SOHO is experiencing one of these electron storms, astronauts traveling to the Moon will be experiencing it as well. And the more dangerous ions and heavier particles are about to arrive. This advance notice will allow the astronauts to retreat to a safer location in the spacecraft and ride out the storm, suffering the minimum radiation damage.

This technique was able to predict all 4 major storms in 2003, providing advance warnings from 7 to 74 minutes.

Original Source: NASA News Release

Posted on by Fraser Cain

Cluster Sees Earth’s Bow Shock Crumple and Reform

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ESA’s Cluster spacecraft were at the right place at the right time to encounter a very special event: the Earth’s bow shock – a wave that forms where the solar wind buffets the magnetosphere – breaking and reforming. This situation was predicted in theory more than 20 years ago, but scientists had never seen it happening in space, until now.

The event occurred on January 24, 2001, when the four spacecraft that make up the Cluster formation were flying at an altitude of 105,000 km above the Earth. Each spacecraft was separated by a distance of about 600 km, allowing them to see space weather events at different times and places. As they approached the bow shock region, scientists expected they’d see roughly the same thing.

Instead, each spacecraft saw large fluctuations in its readings. The magnetic and electric fields were breaking and then reforming further out, like waves build up and crash on shore, and then reform again further out to sea.

Although rare in the Solar System, these kinds of events are very common in the Universe. Photos from Hubble have shown bow shocks form when the intense radiation from young stars blasts into the surrounding stellar nebula.

Original Source: ESA News Release