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What’s up? Night sky for April 2012

Star trails over an observatory

The southern sky is full of wonderful treats for the stargazer. (This star trail photo by Iztok Boncina was made by keeping the camera shutter open.)

Except where indicated, all of the phenomena described here can be seen with the unaided eye. And unless otherwise specified, dates and times are for the Australian Eastern Standard Time zone, and sky directions are from the point of view of an observer in the Southern Hemisphere. (If you’re in the Northern Hemisphere, please see the video at the bottom of the page for What’s Up in your night sky.)

April 3

The Moon, now just over three-quarters full, will be about 11 Moon widths above and to the left of the bright blue star, Regulus, the brightest star of the constellation Leo. A little further below is what looks like a red star, but is actually the planet Mars. The colours of Regulus and Mars make a nice contrast. About 77.5 light years from Earth, Regulus is not one star but four, grouped into two pairs. Multiple star systems are very common throughout the Milky Way galaxy.

April 4

The Moon is still in the vicinity of Mars tonight, being above and to the right of the planet. Incidentally, when I use a term such as “vicinity”, it is not to be taken as suggesting the two bodies are physically near each other out there in space. Rather, they are simply within similar lines-of-sight from our vantage point on Earth.

April 4 sky view

April 4, 8:00pm. The Moon, Mars and the star Regulus will make an attractive triangle in the northern part of the sky. Note the colour difference between blue Regulus and ruddy Mars.

April 7

Full Moon occurs today at 5:19am Sydney time (19:19 Universal Time on April 6). In a similar fashion to its “encounters” with Regulus and Mars a few days earlier, tonight the Moon will be about six Moon widths to the right of another bright star, Spica, and about 10 Moon widths above the planet Saturn. Spica is the brightest star of the constellation Virgo; it is a blue giant star about 260 light years from Earth. This is a great time to see Saturn (see April 16), so it’s a good idea to use the nearby Moon to identify it.

April 8

Today the Moon will be at the closest point in its orbit, called perigee. The distance between the two bodies today will be 358,311 kilometres.

April 10

This evening, take a look about 12 Moon widths below the Moon and you’ll see a reddish looking star that looks a bit like Mars. It’s the star Antares, and its name actually “rival of Mars”. Antares is the brightest star of the constellation Scorpius, and is a red supergiant star about 883 times bigger than our Sun!

Saturn

Saturn, as it appears through a backyard telescope. Image by Steve Massey.

April 13

It is Last Quarter Moon tonight at 8:50pm Sydney time (10:10 Universal Time).

April 16

Today the planet Saturn reaches what astronomers call “opposition”. This means that, from an Earthly perspective, it is the opposite direction to the Sun—so if you could look down on the Solar System from above you’d see the Sun, Earth and Saturn (in that order) in a straight line … although Saturn, of course, is much further from us than the Sun. The period around opposition is a considered a great time to view a planet, as it rises in the east around the same time as the Sun sets in the west, and is therefore nice and high in the sky by late evening.

April 19

If you’re an early riser, out to east this morning before sunrise you’ll see the very thin crescent Moon. Above and to its right is a bright looking star. Well that’s not a star; it’s the planet Mercury, the closest planet to the Sun.

April 19 sky view

April 19, 6:30am. The thin crescent Moon and the planet Mercury will be visible together in the eastern sky before sunrise.

April 21

New Moon occurs today at 5:18pm Sydney time (07:18 Universal Time).

April 23

Today the Moon will again reach the farthest point in its orbit, apogee, at a distance from Earth of 406,421 kilometres.

April 24

Today the Moon makes another apparent close approach to a star, this time Aldebaran, the brightest star of the constellation Taurus. The pair will be low in the western sky after sunset. Like Antares, Aldebaran too is a red star, but not a supergiant—it is only about 44 times the size of our Sun. It’s about 65 light years from Earth.

April 25

There’ll be a lovely astronomical pairing in this evening’s sky, with the Moon very close to Venus. The Moon is the second-brightest object in our night sky, and Venus is the third-brightest.

April 25 sky view

April 25, about 7:15pm. The thin crescent Moon and Venus will be close together in the western sky.

April 29

It is First Quarter Moon today at 7:58pm Sydney time (09:58 Universal Time). First Quarter is a good time to look at the Moon through a telescope, as the sunlight angle means the craters and mountains are throwing nice shadows, making it easier to get that 3D effect.

There’s more great night sky viewing information at Melbourne Planetarium’s Skynotes site.

If you’re in the Northern Hemisphere, here’s a Jet Propulsion Laboratory video that details what you can see this month:

If you have any questions or comments on the night sky, we’d be happy to answer them. Please use the Feedback Form below. Happy stargazing!

Images courtesy IAU and Iztok Boncina / ESO.

Get SpaceInfo.com.au daily updates by RSS or email! Click the RSS Feed link at the top right-hand corner of this page, and then save the RSS Feed page to your bookmarks. Or, enter your email address (privacy assured) and we’ll send you daily updates. Or follow us on Twitter, @spaceinfo_oz

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Solar storm reaches Earth

Illustration of space weather

Artist's illustration of events on the Sun changing the conditions in Near-Earth space

THIS WEEK SAW A HUGE solar disturbance that sent a storm of energy on a collision course with our planet.

The Sun erupted with one of the largest solar flares of this solar cycle on March 6. The flare was categorised as an X5.4, making it the second largest flare—after an X6.9 on August 9, 2011—since the Sun’s activity moved into a period of relatively low activity called solar minimum in early 2007. The current increase in the number of X-class flares is part of the Sun’s normal 11-year solar cycle, during which activity ramps up to solar maximum, which is expected to peak in late 2013.

About an hour later, the same region let loose an X1.3 class flare. An X1 is 5 times smaller than an X5 flare.

Space weather starts at the Sun. It begins with an eruption such as a huge burst of light and radiation called a solar flare or a gigantic cloud of solar material called a coronal mass ejection (CME). But the effects of those eruptions are felt at Earth, or at least near-Earth space. Scientists monitor several kinds of “space weather” events—geomagnetic storms, solar radiation storms, and radio blackouts—all caused by these immense explosions on the Sun.

Geomagnetic storms

One of the most common forms of space weather, a geomagnetic storm refers to any time Earth’s magnetic environment, the magnetosphere, undergoes sudden and repeated change. This is a time when magnetic fields continually re-align and energy dances quickly from one area to another.

Geomagnetic storms occur when certain types of CMEs connect up with the outside of the magnetosphere for an extended period of time. The solar material in a CME travels with its own set of magnetic fields. If the fields point northward, they align with the magnetosphere’s own fields and the energy and particles simply slide around Earth, causing little change. But if the magnetic fields point southward, in the opposite direction of Earth’s fields, the effects can be dramatic. The Sun’s magnetic fields peel back the outermost layers of Earth’s fields changing the whole shape of the magnetosphere. This is the initial phase of a geomagnetic storm.

The next phase, the main phase, can last hours to days, as charged particles sweeping into the magnetosphere accumulate more energy and more speed. These particles penetrate closer and closer to the planet. During this phase viewers on Earth may see bright aurora at lower latitudes than usual. The increase—and lower altitude—of radiation can also damage satellites travelling around Earth.

The final stage of a geomagnetic storm lasts a few days as the magnetosphere returns to its original state.

The movie below shows the March 6, 2012 X5.4 flare, captured by the Solar Dynamics Observatory (SDO) spacecraft. One of the most dramatic features is the way the entire surface of the Sun seems to ripple with the force of the eruption. This movement comes from something called EIT waves—because they were first discovered with the Extreme ultraviolet Imaging Telescope (EIT) on the Solar Heliospheric Observatory (SOHO).

Since SDO captures images every 12 seconds, it has been able to map the full evolution of these waves and confirm that they can travel across the full breadth of the Sun. The waves move at over a million miles per hour, zipping from one side of the Sun to the other in about an hour. The movie shows two distinct waves. The first seems to spread in all directions; the second is narrower, moving toward the southeast. Such waves are associated with, and perhaps trigger, fast coronal mass ejections, so it is likely that each one is connected to one of the two CMEs that erupted on March 6.

Geomagnetic storms do not always require a CME. Mild storms can also be caused by something called a co-rotating interaction region (CIR). These intense magnetic regions form when high-speed solar winds overtake slower ones, thus creating complicated patterns of fluctuating magnetic fields. These, too, can interact with the edges of Earth’s magnetosphere and create weak to moderate geomagnetic storms.

Geomagnetic storms are measured by ground-based instruments that observe how much the horizontal component of Earth’s magnetic field varies. Based on this measurement, the storms are categorized from G1 (minor) to G5 (extreme). In the most extreme cases transformers in power grids may be damaged, spacecraft operation and satellite tracking can be hindered, high frequency radio propagation and satellite navigation systems can be blocked, and auroras may appear much further south than normal.

Solar radiation storms

A solar radiation storm, which is also sometimes called a solar energetic particle (SEP) event, is much what it sounds like: an intense inflow of radiation from the Sun. Both CMEs and solar flares can carry such radiation, made up of protons and other charged particles. The radiation is blocked by the magnetosphere and atmosphere, so cannot reach humans on Earth. Such a storm could, however, harm humans travelling from Earth to the Moon or Mars, though it has little to no effect on airplane passengers or astronauts within Earth’s magnetosphere. Solar radiation storms can also disturb the regions through which high frequency radio communications travel. Therefore, during a solar radiation storm, airplanes travelling routes near the poles—which cannot use GPS, but rely exclusively on radio communications—may be re-routed.

Photo of an aurora

Aurorae occur primarily near Earth's poles. They are the most common and the only visual result of space weather. This aurora image associated with solar flares and CMEs on February 23-24, 2012 was taken over Muonio, Finland before sunrise on February 27, 2012.

Solar radiation storms are rated on a scale from S1 (minor) to S5 (extreme), determined by how many very energetic, fast solar particles move through a given space in the atmosphere. At their most extreme, solar radiation storms can cause complete high frequency radio blackouts, damage to electronics, memory and imaging systems on satellites, and radiation poisoning to astronauts outside of Earth’s magnetosphere.

Radio blackouts

Radio blackouts occur when the strong, sudden burst of X-rays from a solar flare hits Earth’s atmosphere, jamming both high and low frequency radio signals. The X-rays disturb a layer of Earth’s atmosphere known as the ionosphere, through which radio waves travel. The constant changes in the ionosphere change the paths of the radio waves as they move, thus degrading the information they carry. This affects both high and low frequency radio waves alike. The loss of low frequency radio communication causes GPS measurements to be off by feet to miles, and can also affect the applications that govern satellite positioning.

Radio blackouts are rated on a scale from R1 (minor) to R5 (extreme). The strongest radio blackouts can result in no radio communication and faulty GPS for hours at a time.

More information: Space Weather Frequently Asked Questions

Adapted from information issued by NASA. Images courtesy NASA and Thomas Kast. Video courtesy NASA / GSFC / SDO.

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What’s up? Night sky for January 2012

Stargazers with telescopes at night

Summer nights are perfect for stargazing.

Except where indicated, all of the phenomena described here can be seen with the unaided eye. And unless otherwise specified, dates and times are for the Australian Eastern Daylight Time (AEDT) zone, and sky directions are from the point of view of an observer in the Southern Hemisphere.

January 1

It is First Quarter Moon today at 5:15pm AEDT. First Quarter is a good time to look at the Moon through a telescope, as the sunlight angle means the craters and mountains  throw nice shadows, making it easier to get that 3D effect.

January 3

Today the Moon will reach the farthest point in its orbit from the Earth, which is called apogee. It’s distance from our planet will be 404,578 kilometres.

While you’re out looking at the Moon, you’ll notice a bright looking star above and to the left. Well, that’s not a star; it’s actually the planet Jupiter. If you have access to a telescope, or even a pair of 7×50 (or better) binoculars, train them on Jupiter and you should see up to four tiny pinpoints of light on either or both sides of the planet—these are the moons Galileo discovered, Io, Europa, Ganymede and Callisto. If you take a look again tomorrow night, you’ll see that their positions will have changed as they whiz around the planet.

And in fact, we’re only a few days away from the anniversary of their discovery. On the 7th of this month, it will be 402 years since Galileo spotted them!

January 5

Today the Earth reaches perihelion in its orbit around the Sun. Perihelion is the point in a solar orbit when the body in question (eg. Earth) is at its closest to the Sun. Perihelion occurs today at midday AEDT, at a distance between Earth and Sun of about 147,098,000 kilometres. (The opposite of perihelion is aphelion, which for Earth will occur on July 5, 2012 at a distance of about 152,098,000 kilometres.)

If you have a pair of binoculars, you’ll see a pretty sight tonight, with the soon-to-be-full Moon appearing to sit above a beautiful star cluster called the Pleiades, or Seven Sisters. When the Moon is not around and the sky is dark, most people can make out 6 to 7 of the Pleiades stars, although eagle-eyed stargazers can see a few more. There are actually hundreds of stars in this beautiful open star cluster, and it is also filled with beautiful whispy gas clouds, although the stars and the gas are not actually related to each other—we just happen to be seeing them at a time when the stars are drifting through the gas.

Diagram of Moon near Pleiades in January 5's night sky

This is the view in the evening of January 5, with the Moon sitting above the beautiful star cluster known as the Pleiades. A pair of binoculars will show the scene well. Tomorrow night the Moon will have shifted east, and will be near to Albebaran, the brightest star in the constellation Taurus.

January 6

Tonight you might notice a fairly bright, reddish-looking star just above the Moon. This is Aldebaran, the brightest star in the constellation Taurus.

January 9

Full Moon occurs today at 6:30pm AEDT.

January 12

Tonight, the Moon will appear above and to the right of a bright blue star. This is Regulus, the brightest star in the constellation Leo.

January 14

In this morning’s pre-dawn sky out to the east, the Moon will appear above and to the left of the planet Mars, which looks like a ruddy-coloured star. As you gaze at it, spare a thought for the Mars Science Laboratory, which was launched a little under two months ago and which is due to reach the Red Planet on August the 6th this year.

January 16

It is Last Quarter Moon today at 8:08pm AEDT.

January 17

In this morning’s sky, the Moon will be just above and to the right of the planet Saturn, which looks like a bright star. Nearby is Spica, the brightest star in the constellation Virgo.

Diagram showing the Moon near Spica and Saturn in January 17's night sky

The Moon will be near to both the star Spica and the planet Saturn (the bright yellowish "star" below the Moon) on January 17. If you have access to a small telescope, take a look at both the craters and mountains on the Moon and Saturn and its glorious rings.

January 18

Today the Moon will be at the closest point in its orbit, called perigee. The distance between the two bodies today will be 369,887 kilometres.

January 20

In the early dawn sky, take a look for the Moon and you should see a reddish-looking star just above it. This is Antares, the brightest star in the constellation Scorpius. Compare Antares with Mars—do you think they look similar? The ancients thought so, and in fact the name Antares means “rival of Mars”.

January 23

New Moon occurs today at 8:39pm AEDT.

January 27

Tonight, there’ll be a lovely sight in the evening sky out to the west, with the crescent Moon paired with the bright planet Venus (about 20 Moon widths to its left).

January 30

This evening, the Moon meets up with Jupiter again, appearing below the planet in the northwestern part of the sky.

Also today, the Moon will again reach apogee again, at a distance from Earth of 404,323 kilometres.

Diagram showing the Moon near Jupiter in January 30's night sky

The Moon will sit just below the planet Jupiter in the evening sky of January 30.

January 31

And finally for January, we have a second First Quarter Moon, which occurs today at 3:10pm AEDT.

There’s more great night sky viewing information at Melbourne Planetarium’s Skynotes site.

If you have any questions or comments on the night sky, we’d be happy to answer them. Please use the Feedback Form below. Happy stargazing!

Main image courtesy IAU.

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Video – The Sun unleashes its fury

TO US DOWN HERE ON THE GROUND, the Sun seems unchanging and ever-reliable on a day-to-day basis. But satellites reveal the reality to be very different. Our nearest star is actually a boiling, roiling cauldron of hot gases, unseen magnetic fields and titanic explosions.

Those explosions are called coronal mass ejections, or CMEs, and they shoot enormous clouds of particles far out into the Solar System. Sometimes they hit Earth…but fortunately we’re protected by our planet’s strong magnetic field and thick atmosphere.

The Sun produced about a dozen CMEs between November 22 and 28, 2011. The SOHO spacecraft—which monitors the Sun 24/7—spotted them blasting out in different directions. The following video clip comprises over 1,300 frames, and gives us a sped-up view of those eight eventful days on the Sun:

In order to see the CMEs, SOHO had to block out the glare of the Sun using a coronagraph (black circle). A separate instrument took images of the Sun at the same time (superimposed in the middle) so that we could get the best of both worlds.

The next video was produced from images taken with a different Sun-monitoring spacecraft, the Solar Dynamics Observatory. It shows a portion of an extremely long filament (over 1,000,000 km) that was stretched across much of the face of the Sun and gracefully erupted into space (November 14, 2011).

Filaments are cooler gas structures that are tethered to the Sun by magnetic forces. About the upper third of this filament rose up and broke away, but the other two-thirds still remains in sight. The images were taken in extreme ultraviolet light. The clip covers about 12 hours of activity.

Finally, here’s an amazing video that gives us a complete time-lapse of the Sun spanning the entire months of September, October and November 2011 as seen through the SWAP ultraviolet instrument aboard yet another Sun-monitoring satellite, the European Space Agency’s Proba-2 (PRoject for OnBoard Autonomy).

Adapted from information issued by NASA / SDO / ESA.

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What’s up? The night sky for December 2011

Telescope dome at night

Stargazing is great fun, now that the warmer summer weather is here.

Except where indicated, all of the phenomena described here can be seen with the unaided eye. And unless otherwise specified, dates and times are for the Australian Eastern Standard Time zone, and sky directions are from the point of view of an observer in the Southern Hemisphere.

December 2

It is First Quarter Moon today at 8:52pm Australian Eastern Daylight Time (AEDT). First Quarter is a good time to look at the Moon through a telescope, as the sunlight angle means the craters and mountains  throw nice shadows, making it easier to get that 3D effect.

December 6

Today the Moon will reach the farthest point in its orbit, apogee, at a distance from Earth of 405,412 kilometres. And if you take a look at the Moon this evening, you’ll see a bright ‘star’ above and to its right. That’s not a star—it’s actually the planet Jupiter!

December 9

Take a look at the Moon in this evening’s sky, and you’ll see a brightish star a little way out to its right. And yes, this one really is a star. It’s called Aldebaran, and it’s the brightest star in the constellation Taurus. Aldebaran is a red giant star roughly 44 times as big as the Sun, and is about 65 light-years from Earth.

December 10

Full Moon occurs today at 1:36am AEDT, and tonight everyone in Australia and New Zealand will experience a total lunar eclipse. See our separate lunar eclipse story for full details on how, when and where to see it.

Eclipses aside…although it looks very pretty high up there in the sky, astronomers, both amateur and professional, generally hate the full Moon. This is because its light tends to drown out many of the fainter objects they’re interested in seeing. (It does this by actually making the sky glow.) It’s also not a good time to look at the Moon itself through a telescope, as the overhead sunlight (as seen from the perspective of the Moon) doesn’t throw any shadows across the lunar surface—and shadows are what give the craters and mountains their 3D look.

Man looking through a telescope

The Moon looks great through a telescope, but you won't need one to see the total lunar eclipse on December 10, 2011.

December 17

If you’re up early today, look for the Moon and you’ll see that it seems to have two companions. A little way below and to its left is the star Regulus, and below and to its right is the planet Mars. Regulus is actually a quadruple star system, comprised of four stars in two groups of two, gravitationally bound to one another. But the main star is a young, blue star a little over three times the mass of the Sun, and about three to four times as big as the Sun too.

December 18

It is Last Quarter Moon today at 11:48am AEDT. The Moon is still near Mars in the sky, being above and to the right of the planet in the hours before dawn.

December 21

The Moon, a star and a planet make a nice triangle in this morning’s sky. The star is Spica, the brightest star in the constellation Virgo, and the planet is Saturn. Saturn will be to the left of the Moon, and Spica will be above Saturn. Spica, a blue giant star, is the 15th brightest star in the night sky and is about 260 light-years from Earth.

December 22

There are two items of note for today. First, the Moon will be at the closest point in its orbit, called perigee, which is the opposite of apogee. The distance between the two bodies today will be 364,800 kilometres. And secondly, today marks the summer solstice in the Southern Hemisphere. This is the day of the year when the Sun is highest in the sky.

December 25

New Moon occurs today at 5:06am AEDT.

December 27-28

The Moon is back in the western evening sky. Over these two nights, it’ll be paired up with the planet Venus—the duo will make a very attractive sight in the evening dusk.

There’s more great night sky viewing information at Melbourne Planetarium’s Skynotes site.

If you have any questions or comments on the night sky, we’d be happy to answer them. Please use the Feedback Form below. Happy stargazing!

Story by Jonathan Nally. Images courtesy IAU.

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Killer solar storms? Sorry, not going to happen

THERE’S A LOT OF NONSENSE flying around at the moment about the supposed arrival of a killer solar storm season next year.

As this NASA video points out, there is no expectation that Earth is in any danger. In fact, according to NASA, there “simply isn’t enough energy in the sun to send a killer fireball 93 million miles to destroy Earth.”

Story by Jonathan Nally. Image and video courtesy NASA / GSFC.

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What’s up? Night sky for November 2011

People looking at the evening sky

Late spring nights and mornings are ideal for stargazing, and there are some interesting things to see this month.

Except where indicated, all of the phenomena described here can be seen with the unaided eye. And unless otherwise specified, dates and times are for the Australian Eastern Standard Time zone, and sky directions are from the point of view of an observer in the Southern Hemisphere.

November 3

It is First Quarter Moon today at 3:38am Australian Eastern Daylight Time. First Quarter is a good time to look at the Moon through a telescope, as the sunlight angle means the craters and mountains are throwing nice shadows, making it easier to get that 3D effect.

November 9

Take a look in the evening sky and you’ll see the Moon with what looks like a bright star above and to its right. Well, that’s not a star, it’s the planet Jupiter. Also today, the Moon will reach the farthest point from Earth in its orbit, apogee, at a distance from Earth of 406,176 kilometres.

November 10

Take a look at the western horizon after sunset and you’ll see a pretty group comprising Venus, Mercury and the star Antares.

Looking at the Moon with a telescope

The Moon teams up with several planets during November

November 11

Full Moon occurs today at 7:16am Australian Eastern Daylight Time.

November 11-12

Out to the east in the early morning sky (pre-dawn) you’ll find a pair of celestial orbs that contrast each other nicely in colour. Ruddy coloured Mars will appear very close to Regulus, a blue giant star that is the brightest star in the constellation Leo.

November 19

It is Last Quarter Moon today at 2:09am Australian Eastern Daylight Time. If you’re up before dawn, take a look out to the eastern sky and you’ll see the Moon with the star Regulus close by, and the planet Mars about 4 degrees away as well.

November 23

Another attractive grouping, but quite low in the eastern sky before dawn (so you’ll need a clear horizon). There’ll be the Moon, plus the star Spica (the brightest star in the constellation Virgo) and the planet Saturn as well.

November 24

Today the Moon will be at the closest point to Earth in its orbit, called perigee, which is the opposite of apogee. The distance between the two bodies today will be 359,691 kilometres.

November 25

New Moon occurs today at 5:10pm Australian Eastern Daylight Time.

November 27

Take a look out to the west just after sunset, and you might see the very thin crescent Moon below and to the right of the planet Venus.

If you have any questions or comments on the night sky, we’d be happy to answer them. Please use the Feedback Form below. Happy stargazing!

Images courtesy IAU / TWAN / Babak /A. Tafreshi.

Get SpaceInfo.com.au daily updates by RSS or email! Click the RSS Feed link at the top right-hand corner of this page, and then save the RSS Feed page to your bookmarks. Or, enter your email address (privacy assured) and we’ll send you daily updates. Or follow us on Twitter, @spaceinfo_oz

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Solar flare heads for Earth

SOLAR FLARES ARE GIANT EXPLOSIONS ON THE SUN that send energy, light and high-speed particles into space. These flares are often associated with solar magnetic storms known as coronal mass ejections (CMEs).

The number of solar flares increases approximately every 11 years, and the Sun is currently moving towards another solar maximum, likely in 2013.

That means more flares will be coming, some small and some big enough to send their radiation all the way to Earth.

The biggest flares are known as “X-class flares” based on a classification system that divides solar flares according to their strength. The smallest ones are A-class (near background levels), followed by B, C, M and X.

Overload

Similar to the Richter scale for earthquakes, each letter represents a 10-fold increase in energy output. So an X is ten times an M and 100 times a C. Within each letter class there is a finer scale from 1 to 9.

C-class and smaller flares are too weak to noticeably affect Earth. M-class flares can cause brief radio blackouts at the poles and minor radiation storms that might endanger astronauts.

And then come the X-class flares. Although X is the last letter, there are flares more than 10 times the power of an X1, so X-class flares can go higher than 9.

The most powerful flare measured with modern methods was in 2003, during the last solar maximum, and it was so powerful that it overloaded the sensors measuring it. The sensors cut out at X28.

Here’s a video of that X28 flare:

Satellites at risk

The biggest X-class flares are by far the largest explosions in the Solar System and are awesome to watch. Loops tens of times the size of Earth leap up off the Sun’s surface when the Sun’s magnetic fields cross over each other and reconnect.

In the biggest events, this reconnection process can produce as much energy as a billion hydrogen bombs.

If they’re directed at Earth, such flares and associated CMEs can create long lasting radiation storms that can harm satellites, communications systems, and even ground-based technologies and power grids.

X-class flares on December 5 and December 6, 2006, for example, triggered a CME that interfered with GPS signals being sent to ground-based receivers.

Danger to astronauts

NASA and NOAA (the US National Oceanic and Atmospheric Administration)—as well as the US Air Force Weather Agency (AFWA) and others—keep a constant watch on the Sun to monitor for X-class flares and their associated magnetic storms.

With advance warning many satellites and spacecraft can be protected from the worst effects.

On August 9, 2011 at 3:48am US EDT, the Sun emitted an X6.9 flare, as measured by the NOAA GOES satellite, and aimed at Earth. These gigantic bursts of radiation cannot pass through Earth’s atmosphere to harm humans on the ground, however they can disrupt the atmosphere and disrupt GPS and communications signals.

In this case, it appears the flare is strong enough to potentially cause some radio communication blackouts. It also produced increased solar energetic proton radiation—enough to affect humans in space if they do not protect themselves.

There was also a coronal mass ejection (CME) associated with this flare. CMEs are another solar phenomenon that can send solar particles into space and affect electronic systems in satellites and on Earth. However, this CME is not travelling toward Earth and so no Earth-bound effects are expected.

Here’s a NASA video that shows the power of X-class flares:

Adapted from information issued by NASA.

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Two massive solar eruptions

THE SUN BLEW OUT TWO sizeable ‘coronal mass ejections’ that headed in just about opposite directions over about a two-day period (July 24-25, 2011). Both of these were from the far side of the Sun and had no impact on Earth.

A coronal mass ejection, or CME, is a huge magnetic bubble of plasma that erupts from the Sun’s corona (the outermost layer of the solar atmosphere) and travels through space at high speed.

In the video—which has been put together from a series of still images and sped up—the Sun (represented real-size by the white circle) and some additional area around it is blocked out with an occulting disc so that the fainter details in the corona can be seen.

To give you an idea of the size of these CMEs, look at the white circle that represents the Sun and remember that the Sun is 109 times wider than the Earth!

The images were taken by the STEREO (Ahead) spacecraft.

Adapted from information issued by NASA.

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What’s up? Night sky for August 2011

Stargazers with telescopes

This month, Saturn will be the planet to watch in the western part of the sky after sunset.

FOUR PLANETS ARE VISIBLE THIS MONTH, although you’ll have to be quick to spot Mercury, as it starts the month low on the western horizon after sunset and within about a week will have become lost in the Sun’s glare.

Slightly higher in the western sky after sunset is Saturn, shining brightly and visited by the Moon on the 4th.

Jupiter and Mars are still the luminaries of the morning sky—Jupiter high in the north, and Mars low in the north-east. Their brighter sibling, Venus, will not be visible this month, as it is on the opposite side of the Sun from us.

Except where indicated, all of the phenomena described here can be seen with the unaided eye. And unless otherwise specified, dates and times are for the Australian Eastern Standard Time zone, and sky directions are from the point of view of an observer in the Southern Hemisphere.

August 1

Look for the very thin crescent Moon low in the west after sunset. The planet Mercury will be about seven Moon widths above and to the right. Mercury is becoming much harder to see now, and over the next week will sink lower and lower toward the horizon and become lost in the Sun’s glare. The innermost planet will reappear in our morning sky out to the east next month.

August 3

Today the Moon will be at the closest point to Earth in its orbit, called perigee, at 7:00am. The distance between the two bodies will be 365,755 kilometres.

August 4

Look for the Moon and Saturn close together in the west in the early evening sky.

August 5

The Moon and the star Spica—the brightest star in the constellation Virgo—will appear close together tonight. The Moon will be about six Moon widths above the star.

August 6

It is First Quarter Moon today at 9:08pm. First Quarter is a good time to look at the Moon through a telescope, as the sunlight angle means the craters and mountains throw nice shadows, making it easier to get that 3D effect.

August 8

Now almost three-quarters full, the Moon will be near the star Antares—the brightest star in the constellation Scorpius. Antares has a reddish colour, and to the naked eye it looks a bit like the planet Mars. In fact, its name means ‘rival of Mars’.

Stargazers

Make the most of the late-winter nights by doing some stargazing.

August 14

Full Moon will occur today at 4:58am.

August 16

If you’ve been wondering why Venus doesn’t appear to be in our evening or morning skies, it’s because it is lost in the glare of the Sun. Today marks its ‘superior conjunction’, which means that it is on the exact opposite side of the Sun from us.

August 17

Mercury, which has been lost in the glare of the setting Sun for a while now, today reaches ‘inferior conjunction’, which means that it is exactly between us and the Sun. Mercury will reappear low in the east in the morning sky next month.

August 19

Today the Moon will be at the farthest point from Earth in its orbit, called apogee, at 2:24am. The distance between the two bodies will be 405,159 kilometres.

August 21

Look out to the east this morning, and you’ll see the Moon and what looks like a very bright star above and to its left. That’s not a star; it’s the planet Jupiter. Even if you don’t have a telescope, a normal pair of binoculars should reveal up to four of Jupiter’s largest moons, looking like small pinpricks of light to one or both sides of the planets.

August 22

It is Last Quarter Moon today at 9:55pm.

August 26

If you’re an early riser, take a look out to the east and you’ll see the Moon very close to the planet Mars.

August 29

New Moon occurs today at 1:04pm.

August 31

Today the Moon will again be at the closest point to Earth in its orbit, perigee, this time at 3:36am. The distance between the two bodies will be 360,857 kilometres.

If you have any questions or comments on the night sky, we’d be happy to answer them. Please use the Feedback Form below. Happy stargazing!

Images courtesy IAU.

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