sun Archives

October 22, 2014December 23, 2015 by Bob King

Beastly Sunspot Amazes, Heightens Eclipse Excitement

Ron Cottrell captured the sunspot in all its swirly magnetic goodness in hydrogen-alpha light on October 19. To appreciate its size, he included the Earth (lower left) for reference. Credit: Ron Cottrell

That’s one big, black blemish on the Sun today! Rarely have we been witness to such an enormous sunspot. Lifting the #14 welder’s glass to my eyes this morning I about jumped back and bumped into the garage.

Properly shielded, it was very easy to see with the naked eye. Unlike some other naked eye sunspots, this one showed structure. The eastern end was darker, the western half grayer and more extended.

Watch the giant spot rotate into view and grow right before your eyes in this 72-hour time-lapse video taken by SOHO’s HMI imager Oct. 18-20, 2014

Through a small telescope, the mix of dark umbras scattered amid weirdly sculpted penumbral “islands” was incredible to see. Photographs like the one above are wonderful documents, but witnessing this beautiful complex magnetic mess with your own eyes is another experience altogether. Region 2192 continues to grow and size and complexity and is now the largest sunspot group of solar cycle 24 which began in 2009 – more than five years ago!

Active region 2192 is now the largest sunspot group to appear in over five years. Credit: Alex Young — Active region 2192 is now the largest sunspot group to appear in over five years. Compare to Jupiter and the Earth. Credit: SDO/HMI/Alex Young

Every sunspot marks a region on the Sun’s shiny outer skin called the photosphere where magnetic energy is concentrated. Strong magnetic fields within a sunspot group quell the turbulent churning of the photosphere, chilling the region by several thousand degrees. Sunspots appear dark against the Sun’s blazing disk because they’re cooler. Cooler meaning 8,000 F instead of 11,000 F, so yes, they’re still VERY hot.

Watch as Region 2192 crackles with energy and flares as seen in far ultraviolet light with NASA’s Solar Dynamics Observatory.

Energy stored in sunspots’ twisted magnetic fields can suddenly be released in violent, explosions called solar flares. Billions of tons of solar plasma – the sizzling mix of protons and electrons that composes the Sun – are heated to millions of degrees during the explosion and rapidly accelerated into space. Radiation from radio waves to X-rays and gamma rays fans out at the speed of light. Fortunately for us, our atmosphere and planetary magnetic field protect us from most of what flares can fling our way.

NASA's Solar Dynamics Observatory took this photo of the sun and Jupiter-sized sunspot 2192 this morning Oct. 22 at 8:45 a.m. CDT. The view in a small telescope equipped with a safe solar filter is even better! Credit: NASA — NASA’s Solar Dynamics Observatory took this photo of the Sun and Jupiter-sized sunspot region 2192 this morning Oct. 22 at 8:45 a.m. CDT. The view in a small telescope equipped with a safe solar filter is even better! Credit: NASA

But as the Sun rotates this monster into our line of sight, possibilities for Earth-directed flares and coronal mass ejections increase as do geomagnetic storms, the bringer of auroras. Already in the past 48 hours, the spot has dished out seven M-class flares and a powerful X-1 flare even before it has fully come into view. There’s more to come – Region 2192 harbors an unstable beta-gamma-delta magnetic field ripe for additional flaring including more of the X-class variety.

The sun on October 21 showing smaller sunspot regions along with our featured group. Credit: Sarah and Simon Fisher — The Sun on October 21 showing smaller sunspot regions along with our featured group. Credit: Sarah and Simon Fisher

There’s no doubt now that this behemoth will stick around to add a whole new dimension to tomorrow’s partial solar eclipse. I can’t wait to see the Moon’s black curve approach and at least partially occult the group from view. If you’re interested in getting some one-of-a-kind pictures of the scene, please see our own Dave Dickinson’s excellent guide on photographing the partial eclipse.

A sliver of a Moon rises in morning twilight today October 22 just a day away from its appointment with the Sun. Credit: Bob King

While we’re on the Moon, early morning risers had the pleasure of its company just one day before New Moon and solar eclipse. I was out watching the Orionid meteor shower. While not rich like the Perseids or Geminids I managed to catch a few including a few lucky shots with the camera.

An Orionid meteor slashes across the top of the frame directly above the constellation Orion early this morning October 22, 2014. Details: 24mm lens, f/2.8, 30-seconds at ISO 1600. Credit: Bob King

The shower has peaked but will still be active the remainder of the week if you’re inclined to take a look. And I can’t resist. How about one last sweet close-up photo of sunspot group 2192? I have a feeling you won’t mind.

Monster Sunspot AR12192 taken by Karzaman Ahmad on October 21, 2014 from Langkawi Nagtional Observatory, Malaysia credit: Karzaman Ahmad and shared at spaceweather.com — Monster Sunspot AR12192 taken by Karzaman Ahmad on October 21, 2014, from Langkawi Nagtional Observatory, Malaysia. Credit: Karzaman Ahmad and shared at spaceweather.com. Click the image to see additional animations and photos on Alex Young’s site

October 20, 2014December 23, 2015 by Jason Major

Awesome Photo Shows Monster Sunspot Aiming Our Way

Visible light image of the Sun captured on Oct. 19, 2014. © Alan Friedman. All rights reserved.

It’s a-comin’: a “monster” sunspot is steadily rotating around the Sun’s southern hemisphere and will soon be in position to fire flares and CMEs in our direction — and this past weekend master solar photographer Alan Friedman captured it on camera!

The image above was taken in full-spectrum visible light on Sunday, Oct. 19 by Alan from his backyard in Buffalo, New York. Sunspots 2186 (at the top limb), 2187 (upper center), 2193 (the small middle cluster) and the enormous AR2192 are easily visible as dark blotches – “cooler” regions on the Sun’s surface where upwelling magnetic fields interrupt the convective processes that drive the Sun’s energy output.

This particular image was a single frame of video, unlike some of Alan’s other photographs. According to Alan the air turbulence was particularly bad that day, shooting between the clouds, so only this one frame was usable. Click the image for full-scale “wow” factor.

(And if you think AR2192 looks scary in that image, check it out in CaK bands here!)

Scale size of Earth compared to AR2192 on Oct. 20 (NASA/SDO/AIA. Edit by J. Major.) — Scale size of Earth compared to AR2192 on Oct. 20 (NASA/SDO/AIA. Diagram by J. Major.)

According to Spaceweather.com AR2192 has grown considerably over the past few days and has the potential to unleash M- and X-class flares in our direction now that it’s moving into Earth-facing position. It’s currently many times larger than Earth and will likely get even bigger… in fact, during this week’s partial solar eclipse AR2192 should be visible with the naked (but not unprotected!) eye for viewers across much of North America.

See more of Alan’s photography on his Averted Imagination site here (with prints available for purchase) and watch a TEDx presentation by Alan on how and why he does solar photography.

Image © Alan Friedman. Used with permission.

October 20, 2014December 23, 2015 by Bob King

How to Safely Enjoy the October 23 Partial Solar Eclipse

The partially eclipsed sun sets over Island Lake north of Duluth, Minn. on May 20, 2012. Credit: Jim Schaff

2014 – a year rich in eclipses. The Moon dutifully slid into Earth’s shadow in April and October gifting us with two total lunars. Now it’s the Sun’s turn. This Thursday October 23 skywatchers across much of the North America and Mexico will witness a partial solar eclipse. From the eastern U.S. the eclipse will reach maximum around the time of sunset, making for dramatic picture-taking opportunities. Further west, the entire eclipse will occur with the sun up in the afternoon sky. Either way, you can’t go wrong.

During a solar eclipse, the orbiting Moon passes between the Sun and Earth completely blocking the Sun from view as shown here. In Thursday's partial eclipse, the moon will pass a little north of a line connecting the three orbs, leaving a piece of the sun uncovered for a partial eclipse. Credit: Wikipedia — During a solar eclipse, the orbiting Moon passes between the Sun and Earth completely blocking the Sun from view as shown here. In Thursday’s eclipse, the moon will pass a little north of a line connecting the three orbs, leaving a portion of the sun uncovered. To view a partial solar eclipse, a safe solar filter is necessary. Credit: Wikipedia

Solar eclipses occur at New Moon when the Moon passes between the Sun and the Earth and blocks the Sun from view. During a total solar eclipse, the Sun, Earth and Moon are exactly aligned and the Moon completely hides the brilliant solar disk. Partial eclipses occur when the Moon passes slight north or south of the line connecting the three bodies, leaving a slice of the Sun uncovered. For that reason, a safe solar filter is required to protect your eyes at all times. We’ll delve into that in a minute, but first let’s look at the particulars of this eclipse.

Map showing times and percentage of the sun covered during Thursday's partial solar eclipse. Times are Pacific Daylight - add 1 hour for MDT, 2 hours for CDT and 3 hours for EDT. Credit: NASA, F. Espenak with additions by the author — Map showing times and percentage of the sun covered during Thursday’s partial solar eclipse. Times are Pacific Daylight – add 1 hour for MDT, 2 hours for CDT and 3 hours for EDT. Interpolate between the lines to find your approximate viewing time. The arc marked A shows where the eclipse begins at sunset; B = Maximum eclipse at sunset and C = Eclipse ends at sunset. Credit: NASA, F. Espenak,with additions by Bob King

Nowhere will this eclipse be total. At best, polar bears and musk oxen in Canada’s Nunavut Territory near Prince of Wales Island will see 81% of the sun covered at sunset at maximum eclipse. Most of the rest of us will witness about half the Sun covered with the northern U.S. getting around 65% and the southern states closer to 40%. In Minneapolis, Minn. for instance, the eclipse begins at 4:23 p.m. CDT, reaches a maximum of 62% at 5:35 p.m. and continues on till sunset at 6:14 p.m. For times, coverage and other local circumstances for your town, click over to U.S. cities and cities in Canada and Mexico.

Safe solar filters for looking at the sun come in several different varieties. Read down to learn more about each kind. Photo: Bob King — Safe solar filters come in several varieties ranging from plastic glasses to a #14 welder’s glass for visual observation and snug-fitting optical filters that fit over the end of a telescope. Credit: Bob King

There are several ways to observe a partial eclipse safely, but they all start with this credo: Never look directly at the Sun. Dangerous ultraviolet and infrared light focused on your retinas will damage your vision for life. Nothing’s worth that risk. Happily, filters and indirect viewing methods are available. Eclipse glasses fitted with mylar or polymer lenses are a great choice. I’ve used them all but my favorite’s still the classic #14 welder’s glass because it slips in the pocket easily and takes a beating. Make sure it’s a #14, not a #13 or lower.

You can mount binoculars on a tripod, cover one lens with a lenscap and project the sun's image safely onto a sheet of white cardboard. Credit: Bob King — You can mount binoculars on a tripod, cover one lens with a lenscap and project the sun’s image safely onto a sheet of white cardboard. Credit: Bob King

Telescopes should be outfitted with an optical mylar or aluminized glass solar filter that fits snugly over the top end of the tube. A welder’s glass gives a green solar image, mylar a blue one and black polymer a pale orange. Filters work by only allowing a fraction of the Sun’s light to reach the eye. At the end of this article I’ve listed several sites that sell a variety of safe solar filters for naked eye and telescopic use.

Easy guide to building a pinhole projector for solar eclipse viewing

Indirect methods for safe viewing include projecting the Sun’s image through a small telescope or pair of binoculars onto a sheet of white paper or cardboard. You can also build a pinhole projector shown in the video above. A box and piece of aluminum foil are all you need.

Tiny gaps along the length of this palm frond created a series of solar crescents during the July 1991 eclipse. Credit: Bob King

If for some reason you aren’t able to get a solar filter, all is not lost. The tiny spaces between leaves on a tree act like pinhole projectors and will cast hundreds of images of the Sun on the ground below during the eclipse. To see the effect even better, bring along a white sheet or blanket and spread it out beneath the tree. You can even cross your hands over one another at a right angle to create a pattern of small “holes” that will reveal the changing shape of the Sun as the eclipse proceeds.

The white crescents show how much of the Sun will be visible from a variety of locations at maximum eclipse. The farther north you go, the deeper the eclipse. Credit: Jay Anderson

Now that you’re rockin’ to go, here are some other cool things to look for during the eclipse:

* Sunspots appear black when viewed through a filtered telescope, but they’re no match for the opaque-black Moon silhouetted against the Sun. Compare their unequal degrees of darkness. With a little luck, the giant sunspot region 2192 will provide a striking contrast with the moon plus add interest to the eclipse. This region only recently rotated onto the Sun’s front side and will be squarely in view on Thursday.

* The moon may look smooth and round to the eye, but its circumference is bumpy with crater rims and mountain peaks. Watch for these tiny teeth to bite into the solar disk as the eclipse progresses.

* From locations where half or more the Sun’s disk is covered, look around to see if you can tell the light has changed. Does it seem somehow “grayer” than normal? Is the blueness of the sky affected?

As I learned from comet discoverer and author David Levy many years ago, every eclipse involves the alignment of four bodies: Sun, Earth, Moon and you. We wish you good weather and a wonderful eclipse, but if clouds show up, you can still watch it via live stream on SLOOH.

Not only will the sun be eclipsed this afternoon but the planet Venus shines just 1.1 degrees to its north. Venus is very close to superior conjunction which occurs early Saturday. In the photo, the planet is in the background well behind the Sun. Don’t count on seeing Venus – too much glare! This photo was taken from space by NASA’s Solar and Heliospheric Observatory this afternoon using a coronagraph to block the Sun from view. Credit: NASA/ESA — UPDATE: Not only will the sun be eclipsed Thursday afternoon but the planet Venus will shine just 1.1 degrees to its north. Venus is just two days from superior conjunction. In the photo, the planet is in the background well behind the Sun. Don’t count on seeing it – too close and too much dangerous glare! This photo was taken from space by NASA’s Solar and Heliospheric Observatory early Thursday Oct. 23 using a coronagraph to shade the Sun. Credit: NASA/ESA

Solar filter suppliers – for a #14 welder’s glass, check your local phone book for a welding supply shop:

* Thousand Oaks Optical — Large variety of solar filters for telescopes and cameras. Sheets of black polymer available if you want to make your own.
* Rainbow Symphony — Eclipse glasses and solar viewers as well as filters for binoculars and telescopes. The basic glasses cost less than a buck apiece, but you’ll need to buy a minimum of 25 pairs.
* Opt Corp — Offers high-quality Baader mylar optical filter material to make your own.
* Orion Telescopes — Glass and mylar filters for telescopes and binoculars.
* Amazon.com – Filters for naked eye use

October 10, 2014March 1, 2017 by Fraser Cain

What Part of the Milky Way Can We See?

When you look up and see the Milky Way, you’re gazing into the heart of our home galaxy. What, exactly, are we looking at?

Anyone who’s ever been in truly dark skies has seen the Milky Way. The bright band across the sky is unmistakable. It’s a view of our home galaxy from within.

As you stare out into the skies and see that splash of stars, have you ever wondered, what are you looking at? Which parts are towards the inside of the galaxy and which parts are looking out? Where’s that supermassive black hole you’ve heard so much about?

In order to see the Milky Way at all, you need seriously dark skies, away from the light polluted city. As the skies darken, the Milky Way will appear as a hazy fog across the sky.

Imagine it as this vast disk of stars, with the Sun embedded right in it, about 27,000 light-years from the core. We’re seeing the galaxy edge on, from the inside, and so we see the galactic disk as a band that forms a complete circle around the sky.

Which parts you can see depend on your location on Earth and the time of year, but you can always see some part of the disk.

The galactic core of the Milky Way is located in the constellation Sagittarius, which is located to the South of me in Canada, and only really visible during the Summer. In really faint skies, the Milky Way is clearly thicker and brighter in that region.

Want to know the exact point of the galactic core? It’s right… there.

During the Winter, we’re looking away from the galactic core to the outer regions of the galaxy. It still has the same band of stars, but it’s thinner and without the darker clouds of dust that obscure our view to the galactic core.

How do astronomers even know that we’re in a spiral galaxy anyway?

There are two major types of galaxies, spiral galaxies and elliptical galaxies.

Elliptical galaxies are made up of so many galactic collisions, they’re nothing more than vast balls of trillions of stars, with no structure. Because we can see a distinct band in the sky, we know we’re in some kind of spiral.

The differences between elliptical and spiral galaxies is easy to see. M87 at left and M74, both photographed with the Hubble Space Telescope. Credit: NASA/ESA

Astronomers map the arms by looking at the distribution of gas, which pulls together in star forming spiral arms. They can tell how far the major arms are from the Sun and in which direction.

The trick is that half the Milky Way is obscured by gas and dust. So we don’t really know what structures are on the other side of the galactic disk. With more powerful infrared telescopes, we’ll eventually be able to see though the gas and dust and map out all the spiral arms.

If you’ve never seen the Milky Way with your own eyes, you need to. Get far enough away from city lights to truly see the galaxy you live in.

The best resource is “The Dark Sky Finder”, we’ll put a link in the show notes.

Have you ever seen the Milky Way? If not, why not? Let’s hear a story of a time you finally saw it.

And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

September 22, 2014December 23, 2015 by Nancy Atkinson

NASA Explains: The Difference Between CMEs and Solar Flares

Solar prominences and filaments on the Sun on September 18, 2014, as seen with a hydrogen alpha filter. Credit and copyright: John Chumack/Galactic Images.

This is a question we are often asked: what is the difference between a coronal mass ejection (CME) and a solar flare? We discussed it in a recent astrophoto post, but today NASA put out a video with amazing graphics that explains it — and visualizes it — extremely well.

“CMEs and solar flares are both explosions that occur on the Sun,” the folks at NASA’s Goddard Spaceflight Center’s Scientific Visualization Studio explain. “Sometimes they occur together, but they are not the same thing.”

CMEs are giant clouds of particles from the Sun hurled out into space, while flares are flashes of light — occurring in various wavelengths — on the Sun.

You can find even more details from NASA here.

September 11, 2014December 23, 2015 by Nancy Atkinson

Astrophoto: The Sun as a Work of Art

A stylized Coronal Mass Ejection: The Sun as work of art. Credit and copyright: Rick Ellis.

Here’s a solar flare with a little flair added! Astrophotographer Rick Ellis from Toronto, Canada created this “artsy” Sun by using a series of photoshop filters and effects with a combination of two images from the Solar Dynamics Observatory taken on April 12, 2013. He tinkered with the contrast at specific color ranges, applied “equalization,” and used a filter called “accented edges.”

“Then I posterized it and ran it through the “posterize edges” filter which really brings out many details,” Rick said via email.

Rick admitted to some confusion about the difference between solar flares and coronal mass ejections, and so we figured this might be a good time to explain. They do have several similarities, however: both solar flares and CMEs are energetic events on the Sun that are both associated with high energy particles, and they both depend on magnetic fields on the Sun.

In the case of a CME, coronal material is ejected into space at high speeds. According to Berkeley University the most obvious difference between a solar flare and a CME is the spatial scale on which they occur.

“Flares are local events as compared to CMEs which are much larger eruptions of the corona,” says the Berkeley webpage, and sometimes a CME can be larger than the Sun itself. Solar flares and coronal mass ejections often occur together, but each can also take place in the absence of the other.

Want to get your astrophoto featured on Universe Today? Join our Flickr group or send us your images by email (this means you’re giving us permission to post them). Please explain what’s in the picture, when you took it, the equipment you used, etc.

September 5, 2014December 23, 2015 by Shannon Hall

A New Marker Might Better Track the Solar Cycle

This image from the Solar and Heliospheric Observatory (SOHO) Extreme ultraviolet Imaging Telescope (EIT) image shows large magnetically active regions and a pair of curving erupting prominences on June 28, 2000 during the current solar cycle 23 maximum. Prominences are huge clouds of relatively cool dense plasma suspended in the Sun's hot, thin corona. Magnetically active regions cause the principal total solar irradiance variations during each solar cycle. The hottest areas appear almost white, while the darker red areas indicate cooler temperatures. Credit: NASA & European Space Agency (ESA) — The Sun. Credit: NASA & European Space Agency (ESA)

Approximately every 11 years the Sun becomes violently active, putting on a show of magnetic activity for aurora watchers and sungazers alike. But the timing of the solar cycle is far from precise, making it hard to determine the exact underlying physics.

Typically astronomers use sunspots to map the course of the solar cycle, but now an international team of astronomers have discovered a new marker: brightpoints, small bright spots in the solar atmosphere that allow us to observe the constant turmoil of material inside the Sun.

The new markers provide a new method in understanding how the Sun’s magnetic field evolves over time, suggesting a deeper and longer cycle.

A well-behaved Sun flips its north and south magnetic poles every 11 years. The cycle begins when the field is weak and dipolar. But the Sun’s rotation is faster at its equator than at its poles, and this difference stretches and tangles the magnetic field lines, ultimately producing sunspots, prominences, and sometimes flares.

“Sunspots have been the perennial marker for understanding the mechanisms that rule the sun’s interior,” said lead author Scott McIntosh, from the National Center for Atmospheric Research, in a news release. “But the processes that make sunspots are not well understood, and far less, those that govern their migration and what drives their movement.”

So McIntosh and colleagues developed a new tracking devise: spots of extreme ultraviolet and X-ray light, known as brightpoints in the Sun’s atmosphere, or corona.

“Now we can see there are bright points in the solar atmosphere, which act like buoys anchored to what’s going on much deeper down,” said McIntosh. “They help us develop a different picture of the interior of the sun.”

McIntosh and colleagues dug through the wealth of data available from the Solar and Heliospheric Observatory and the Solar Dynamics Observatory. They noticed that multiple bands of these markers also move steadily toward the equator over time. But they do so on a different timescale than sunspots.

At solar minimum there might be two bands in the northern hemisphere (one positive and one negative) and two bands in the southern hemisphere (one negative and one positive). Due to their close proximity, bands of opposite charge easily cancel one another, causing the Sun’s magnetic system to be calmer, producing fewer sunspots and eruptions.

But once the two low-latitude bands reach the equator, their polarities cancel each other out and the bands abruptly disappear — a process that takes 19 years on average.

The Sun is now left with just two large bands that have migrated to about 30 degrees latitude. Without the nearby band, the polarities don’t cancel. At this point the Sun’s calm face begins to become violently active as sunspots start to grow rapidly.

Solar maximum only lasts so long, however, because the process of generating a new band of opposite polarity has already begun at high latitudes.

In this scenario, it is the magnetic band’s cycle that truly defines the solar cycle. “Thus, the 11-year solar cycle can be viewed as the overlap between two much longer cycles,” said coauthor Robert Leamon, from Montana State University in Bozeman.

The true test, however, will come with the next solar cycle. McIntosh and colleagues predict that the Sun will enter a solar minimum somewhere in the last half of 2017, and the first sunspots of the next cycle will appear near the end of 2019.

The findings have been published in the Sept. 1 issue of the Astrophysical Journal and are available online.

August 29, 2014December 23, 2015 by Jason Major

Enjoy This Eye-Meltingly Awesome Photo of Our Sun

Photo of the Sun captured and processed by Alan Friedman. (All rights reserved.)

Here’s yet another glorious photo of our home star, captured and processed by New York artist and photographer Alan Friedman on August 24, 2014. Alan took the photo using his 90mm hydrogen-alpha telescope – aka “Little Big Man” – from his backyard in Buffalo, inverted the resulting image and colorized it to create the beautiful image above. Fantastic!

Hydrogen is the most abundant element in our Sun. The “surface” of the Sun and the layer just above it — the photosphere and chromosphere — are regions where atomic hydrogen exists profusely in upper-state form, and it’s these layers that hydrogen alpha photography reveals in the most detail.

In Alan’s image from Aug. 24 several active sunspot regions can be seen, as well as long snaking filaments (which show up bright in this inverted view – in optical light they appear darker against the face of the Sun) and several prominences rising up along the Sun’s limb, one of which along the left side stretching completely off the frame a hundred thousand miles into space!

Click here to see the image above as well as some close-ups from the same day on Alan’s astrophotography website AvertedImagination.com. And you can learn more about how (and why) Alan makes such beautiful images of our home star here.

August 18, 2014March 1, 2017 by Fraser Cain

How Do The Tides Work?

Anyone who lives close to ocean is familiar with the tides. And you probably know they have something to do with the Moon. But how do the tides work? Do other planets experience tides?

Just what the heck are tides? Some kind of orbit jiggle jello effect from the magic Etruscan space-whale song? Is it an unending slap-back of gravitometric Malthusian resonance originating from the core of the Sun’s crystalline liver-light organelles? Is it all the plankton agreeing to paddle in the same direction at their monthly oceanic conferences?

As certain as I am that you enjoy my word terminology salads, with apologies to Papa Bear, we both know tides are caused by the gravitational interaction with the Moon. You would think we’d have only one high tide and one low tide, with the Moon pulling the Earth’s water towards it. Moon goes one side, water rushes over to that side, moon goes to other side, water chases around to follow it. But the tides make the water levels appear to rise twice a day, and lower twice a day in 6 hour increments. So, it’s clearly more complicated than that.

The gravity from the Moon does pull the water towards it. That’s what gives you the highest tide of the day. It’s a bulge of water that follows the Moon around and around as the Earth rotates. This makes sense to us. But then Earth itself is pulled with a little less gravity than the water towards the Moon and, the water on the opposite side of the Earth is pulled with even less gravity, and so you wind up with another bulge on the opposite side of the Earth.

So from our perspective, you end up with a bulge of water towards the Moon, and a bulge away from it. The part of the Earth with the water getting pulled towards the Moon experiences a high tide, and same with the part on the opposite side of the Earth with the other bulge. Correspondingly, the parts of the Earth at right angles are experiencing low tides.

It would be hard enough to predict with a simple spherical Earth covered entirely by water, but we’ve got continents and coastlines, and that makes things even more complicated. The levels that the tides rise and fall depend quite a bit on how easily the water can move around in a region. That’s why you can get such big tides in places like the Bay of Fundy in Canada.

The Moon over Gulf Islands National Seashore near Navarre Beach, Florida. Credit: Mindi Meeks.

Our Sun also contributes to the tides. Surprisingly, it accounts for about 30% of the them. So when the Sun and the Moon are lined up in the sky, you get the highest high tides and the lowest low tides – these are Spring Tides. And then when the Sun and Moon are at right angles, you get the lowest high tides and the highest low tides. These are Neap Tides.

Tidal forces can be very powerful. They can tear galaxies apart and cause moons to get shredded into pieces. Perhaps the most dramatic example is how Jupiter’s enormous gravity pulls on Io so strongly that its surface rises and falls by 100 meters. This is 5 times greater than the Earth’s biggest water tides. This constant rise and fall heats up the moon, giving it non-stop volcanism.

What do you think? Share your favorite tidal science fact in the comments below. And if you like what you see, come check out our Patreon page and find out how you can get these videos early while helping us bring you more great content!

July 17, 2014December 23, 2015 by Brian Koberlein

Is Our Solar System Weird?

This artist’s view shows an extrasolar planet orbiting a star (the white spot in the right). Image Credit: IAU/M. Kornmesser/N. Risinger (skysurvey.org)

Is our Solar System normal? Or is it weird? How does the Solar System fit within the strange star systems we’ve discovered in the Milky Way so far?

With all the beautiful images that come down the pipe from Hubble, our Solar System has been left with celestial body image questions rivaling that of your average teenager. They’re questions we’re all familiar with. Is my posture crooked? Do I look pasty? Are my arms too long? Is it supposed to bulge out like this in the middle? Some of my larger asteroids are slightly asymmetrical. Can everyone tell? And of course the toughest question of all… Am I normal?

The idea that stars are suns with planets orbiting them dates back to early human history. This was generally accompanied by the idea that other planetary systems would be much like our own. It’s only in the last few decades that we’ve had real evidence of planets around other stars, known as exoplanets. The first extrasolar planet was discovered around a pulsar in 1992 and the first “hot jupiter” was discovered in 1995.

Most of the known exoplanets have been discovered by the amazing Kepler spacecraft. Kepler uses the transit method, observing stars over long periods of time to see if they dim as a planet passes in front of the star. Since then, astronomers have found more than 1700 exoplanets, and 460 stars are known to have multiple planets. Most of these stellar systems are around main sequence stars, just like the Sun. Leaving us with plenty of systems for comparison.

Artist's impression of the solar system showing the inner planets (Mercury to Mars), the outer planets (Jupiter to Neptune) and beyond. Credit: NASA — Artist’s impression of the solar system showing the inner planets (Mercury to Mars), the outer planets (Jupiter to Neptune) and beyond. Credit: NASA

So, is our Solar System normal? Planets in a stellar system tend to have roughly circular orbits, just like our Solar system. They have a range of larger and smaller planets, just like ours. Most of the known systems are even around G-type stars. Just like ours.….and we are even starting to find Earth-size planets in the habitable zones of their stars. JUST LIKE OURS!

Not so fast…Other stellar systems don’t seem to have the division of small rocky planets closer to the star and larger gas planets farther away. In fact, large Jupiter-type planets are generally found close to the star. This makes our solar system rather unusual.

Computer simulations of early planetary formation shows that large planets tend to move inward toward their star as they form, due to its interaction with the material of the protoplanetary disk. This would imply that large planets are often close to the star, which is what we observe. Large planets in our own system are unusually distant from the Sun because of a gravitational dance between Jupiter and Saturn that happened when our Solar System was young.

Although our Solar System is slightly unusual, there are some planetary systems that are downright quirky. There are planetary systems where the orbits are tilted at radically different angles, like Kepler 56, and a sci-fi favorite, the planets that orbit two stars like Kepler 16 and 34. There is even a planet so close to its star that its year lasts only 18 hours, known 55 Cancri e.

And so, the Kepler telescope has presented us with a wealth of exoplanets, that we can compare our beautiful Solar System to. Future telescopes such as Gaia, which was launched in 2013, TESS and PLATO slated for launch in 2017 and 2024 will likely discover even more. Perhaps even discovering the holy grail of exoplanets, a habitable planet with life…

And the who knows, maybe we’ll find another planet… just like ours.

What say you? Where should we go looking for habitable worlds in this big bad universe of ours? Tell us in the comments.

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