Our Sun in all its intense, energetic glory. When life appeared on Earth, the Sun would have been much different than it is now; a more intense, energetic neighbor. Image: NASA/SDO.
The early Solar System was a much different place than it is now. Chaos reigned supreme before things settled down into their present state. New research shows that the young Sun was more chaotic and expressive than it is now, and that Earth’s magnetic field was key for the development of life on Earth.
Researchers at the Harvard Smithsonian Centre for Astrophysics have been studying a star called Kappa Ceti, about 30 light years away in the Cetus constellation. Kappa Ceti is in many ways similar to our own Sun, but it’s estimated to be between 400 million to 600 million years old, about the same age as our Sun when life appeared on Earth. Studying Kappa Ceti gives scientists a good idea of the type of star that early life on Earth had to contend with.
Kappa Ceti, at its young age, is much more magnetically active than our 4.6 billion year old Sun, according to this new research. It emits a relentless solar wind, which the research team at Harvard says is 50 times as powerful as the solar wind from our Sun. It’s surface is also much more active and chaotic. Rather than the sunspots that we can see on our Sun, Kappa Ceti displays numerous starspots, the larger brother of the sunspot. And the starspots on Kappa Ceti are much more numerous than the sunspots observed on the Sun.
We’re familiar with the solar flares that come from the Sun periodically, but in the early life of the Sun, the flares were much more energetic too. Researchers have found evidence on Kappa Ceti of what are called super-flares. These monsters are similar to the flares we see today, but can release 10 to 100 million times more energy than the flares we can observe on our Sun today.
So if early life on Earth had to contend with such a noisy neighbour for a Sun, how did it cope? What prevented all that solar output from stripping away Earth’s atmosphere, and killing anything alive? Then, as now, the Earth’s electromagnetic field protected it. But in the same way that the Sun was so different long ago, so was the Earth’s protective shield. It may have been weaker than it is now.
The researchers found that if the Earth’s magnetic field was indeed weaker, then the magnetosphere may have been only 34% to 48% as large as it is now. The conclusion of the study says “… the early magnetic interaction between the stellar wind and the young Earth planetary magnetic field may well have prevented the volatile losses from the Earth exosphere and created conditions to support life.”
Or, in plain language: “The early Earth didn’t have as much protection as it does now, but it had enough,” says Do Nascimento.
Artists concept of a shredded asteroid getting too close to a star. (NASA/JPL-Caltech)
The Sun has enormous destructive power. Any objects that collide with the Sun, such as comets and asteroids, are immediately destroyed.
But now we’re finding that the Sun has the ability to reach out and touch asteroids at a far greater distance than previously thought. The proof of this came when a team at the University of Hawaii Institute of Astronomy was looking at Near-Earth Objects (NEOs) catalogued by the Catalina Sky Survey, and trying to understand what asteroids might be missing from that survey.
An asteroid is classified as an NEO when, at its closest point to the Sun, it is less than 1.3 times the distance from the Earth to the Sun. We need to know where these objects are, how many of them there are, and how big they are. They’re a potential threat to spacecraft, and to Earth itself.
The 60 inch Mt. Lemmon telescope is one of three telescopes used in the Catalina Sky Survey. Image: Catalina Sky Survey, University of Arizona.
The Catalina Sky Survey (CSS) detected over 9,000 NEOs in eight years. But asteroids are notoriously difficult to detect. They are tiny points of light, and they’re moving. The team knew that there was no way the CSS could have detected all NEOs, so Dr. Robert Jedicke, a team member from the University of Hawaii Institute of Astronomy, developed software that would tell them what CSS had missed in its survey of NEOs.
This took an enormous amount of work—and computing power—and when it was completed, they noticed a discrepancy: according to their work, there should be over ten times as many objects within ten solar diameters of the Sun as they found. The team had a puzzle on their hands.
The team spent a year verifying their work before concluding that the problem did not lay in their analysis, but in our understanding of how the Solar System works. University of Helsinki scientist Mikael Granvik, lead author of the Nature article that reported these results, hypothesized that their model of the NEO population would better suit their results if asteroids were destroyed at a much greater distance from the sun than previously thought.
They tested this idea, and found that it agreed with their model and with the observed population of NEOs, once asteroids that spent too much time within 10 solar diameters of the Sun were eliminated. “The discovery that asteroids must be breaking up when they approach too close to the Sun was surprising and that’s why we spent so much time verifying our calculations,” commented Dr. Jedicke.
There are other discrepancies in our Solar System between what is observed and what is predicted when it comes to the distribution of small objects. Meteors are small pieces of dust that come from asteroids, and when they enter our atmosphere they burn up and make star-gazing all the more eventful. Meteors exist in streams that come from their parent objects. The problems is, most of the time the streams can’t be matched with their parent object. This study shows that the parent objects must have been destroyed when they got too close to the Sun, leaving behind a stream of meteors, but no apparent source.
There was another surprise in store for the team. Darker asteroids are destroyed at a greater distance from the Sun than lighter ones are. This explains an earlier discovery, which showed that brighter NEOs travel closer to the Sun than darker ones do. If darker asteroids are destroyed at a greater distance from the Sun than their lighter counterparts, then the two must have differing compositions and internal structure.
“Perhaps the most intriguing outcome of this study is that it is now possible to test models of asteroid interiors simply by keeping track of their orbits and sizes. This is truly remarkable and was completely unexpected when we first started constructing the new NEO model,” says Granvik.
A compilation of images of the Sun taken at the same time and place over the course of 2015, as seen from Sulmona, Abruzzo, Italy. Credit and copyright: Giuseppe Petricca.
If you took a picture of the Sun every day, always at the same hour and from the same location, would the Sun appear in the same spot in the sky? A very fine image, compiled by astrophotographer Giuseppe Petricca from Italy, proves the answer is no.
“A combination of the Earth’s 23.5 degree tilt and its slightly elliptical orbit combine to generate this figure “8” pattern of where the Sun would appear at the same time throughout the year,” said Petricca.
This pattern is called an analemma, the full version shown below:
A compilation of images of the Sun taken at the same time and place over the course of 2015, as seen from Sulmona, Abruzzo, Italy. Credit and copyright: Giuseppe Petricca.
The life cycle of a Sun-like star, from its birth on the left side of the frame to its evolution into a red giant on the right after billions of years. Credit: ESO/M. Kornmesser
The Sun has always been the center of our cosmological systems. But with the advent of modern astronomy, humans have become aware of the fact that the Sun is merely one of countless stars in our Universe. In essence, it is a perfectly normal example of a G-type main-sequence star (G2V, aka. “yellow dwarf”). And like all stars, it has a lifespan, characterized by a formation, main sequence, and eventual death.
This lifespan began roughly 4.6 billion years ago, and will continue for about another 4.5 – 5.5 billion years, when it will deplete its supply of hydrogen, helium, and collapse into a white dwarf. But this is just the abridged version of the Sun’s lifespan. As always, God (or the Devil, depending on who you ask) is in the details!
To break it down, the Sun is about half way through the most stable part of its life. Over the course of the past four billion years, during which time planet Earth and the entire Solar System was born, it has remained relatively unchanged. This will stay the case for another four billion years, at which point, it will have exhausted its supply of hydrogen fuel. When that happens, some pretty drastic things will take place!
The Birth of the Sun:
According to Nebular Theory, the Sun and all the planets of our Solar System began as a giant cloud of molecular gas and dust. Then, about 4.57 billion years ago, something happened that caused the cloud to collapse. This could have been the result of a passing star, or shock waves from a supernova, but the end result was a gravitational collapse at the center of the cloud.
Artist’s concept of a star surrounded by a molecular cloud to form a swirling disk called a “protoplanetary disk.” Credit: NASA/JPL-Caltech
From this collapse, pockets of dust and gas began to collect into denser regions. As the denser regions pulled in more and more matter, conservation of momentum caused it to begin rotating, while increasing pressure caused it to heat up. Most of the material ended up in a ball at the center while the rest of the matter flattened out into disk that circled around it.
The ball at the center would eventually form the Sun, while the disk of material would form the planets. The Sun spent about 100,000 years as a collapsing protostar before temperature and pressures in the interior ignited fusion at its core. The Sun started as a T Tauri star – a wildly active star that blasted out an intense solar wind. And just a few million years later, it settled down into its current form. The life cycle of the Sun had begun.
The Main Sequence:
The Sun, like most stars in the Universe, is on the main sequence stage of its life, during which nuclear fusion reactions in its core fuse hydrogen into helium. Every second, 600 million tons of matter are converted into neutrinos, solar radiation, and roughly 4 x 1027 Watts of energy. For the Sun, this process began 4.57 billion years ago, and it has been generating energy this way every since.
However, this process cannot last forever since there is a finite amount of hydrogen in the core of the Sun. So far, the Sun has converted an estimated 100 times the mass of the Earth into helium and solar energy. As more hydrogen is converted into helium, the core continues to shrink, allowing the outer layers of the Sun to move closer to the center and experience a stronger gravitational force.
The Sun captured by NASA’s Solar Dynamics Observatory Spacecraft.
This places more pressure on the core, which is resisted by a resulting increase in the rate at which fusion occurs. Basically, this means that as the Sun continues to expend hydrogen in its core, the fusion process speeds up and the output of the Sun increases. At present, this is leading to a 1% increase in luminosity every 100 million years, and a 30% increase over the course of the last 4.5 billion years.
In 1.1 billion years from now, the Sun will be 10% brighter than it is today, and this increase in luminosity will also mean an increase in heat energy, which Earth’s atmosphere will absorb. This will trigger a moist greenhouse effect here on Earth that is similar to the runaway warming that turned Venus into the hellish environment we see there today.
In 3.5 billion years from now, the Sun will be 40% brighter than it is right now. This increase will cause the oceans to boil, the ice caps to permanently melt, and all water vapor in the atmosphere to be lost to space. Under these conditions, life as we know it will be unable to survive anywhere on the surface. In short, planet Earth will come to be another hot, dry Venus.
Core Hydrogen Exhaustion:
All things must end. That is true for us, that is true for the Earth, and that is true for the Sun. It’s not going to happen anytime soon, but one day in the distant future, the Sun will run out of hydrogen fuel and slowly slouch towards death. This will begin in approximate 5.4 billion years, at which point the Sun will exit the main sequence of its lifespan.
With its hydrogen exhausted in the core, the inert helium ash that has built up there will become unstable and collapse under its own weight. This will cause the core to heat up and get denser, causing the Sun to grow in size and enter the Red Giant phase of its evolution. It is calculated that the expanding Sun will grow large enough to encompass the orbit’s of Mercury, Venus, and maybe even Earth. Even if the Earth survives, the intense heat from the red sun will scorch our planet and make it completely impossible for life to survive.
Final Phase and Death:
Once it reaches the Red-Giant-Branch (RGB) phase, the Sun will haves approximately 120 million years of active life left. But much will happen in this amount of time. First, the core (full of degenerate helium), will ignite violently in a helium flash – where approximately 6% of the core and 40% of the Sun’s mass will be converted into carbon within a matter of minutes.
The Sun will then shrink to around 10 times its current size and 50 times its luminosity, with a temperature a little lower than today. For the next 100 million years, it will continue to burn helium in its core until it is exhausted. By this point, it will be in its Asymptotic-Giant-Branch (AGB) phase, where it will expand again (much faster this time) and become more luminous.
Over the course of the next 20 million years, the Sun will then become unstable and begin losing mass through a series of thermal pulses. These will occur every 100,000 years or so, becoming larger each time and increasing the Sun’s luminosity to 5,000 times its current brightness and its radius to over 1 AU.
At this point, the Sun’s expansion will either encompass the Earth, or leave it entirely inhospitable to life. Planets in the Outer Solar System are likely to change dramatically, as more energy is absorbed from the Sun, causing their water ices to sublimate – perhaps forming dense atmosphere and surface oceans. After 500,000 years or so, only half of the Sun’s current mass will remain and its outer envelope will begin to form a planetary nebula.
The post-AGB evolution will be even faster, as the ejected mass becomes ionized to form a planetary nebula and the exposed core reaches 30,000 K. The final, naked core temperature will be over 100,000 K, after which the remnant will cool towards a white dwarf. The planetary nebula will disperse in about 10,000 years, but the white dwarf will survive for trillions of years before fading to black.
Ultimate Fate of our Sun:
When people think of stars dying, what typically comes to mind are massive supernovas and the creation of black holes. However, this will not be the case with our Sun, due to the simple fact that it is not nearly massive enough. While it might seem huge to us, but the Sun is a relatively low mass star compared to some of the enormous high mass stars out there in the Universe.
As such, when our Sun runs out of hydrogen fuel, it will expand to become a red giant, puff off its outer layers, and then settle down as a compact white dwarf star, then slowly cooling down for trillions of years. If, however, the Sun had about 10 times its current mass, the final phase of its lifespan would be significantly more (ahem) explosive.
When this super-massive Sun ran out of hydrogen fuel in its core, it would switch over to converting atoms of helium, and then atoms of carbon (just like our own). This process would continue, with the Sun consuming heavier and heavier fuel in concentric layers. Each layer would take less time than the last, all the way up to nickel – which could take just a day to burn through.
Then, iron would starts to build up in the core of the star. Since iron doesn’t give off any energy when it undergoes nuclear fusion, the star would have no more outward pressure in its core to prevent it from collapsing inward. When about 1.38 times the mass of the Sun is iron collected at the core, it would catastrophically implode, releasing an enormous amount of energy.
Within eight minutes, the amount of time it takes for light to travel from the Sun to Earth, an incomprehensible amount of energy would sweep past the Earth and destroy everything in the Solar System. The energy released from this might be enough to briefly outshine the galaxy, and a new nebula (like the Crab Nebula) would be visible from nearby star systems, expanding outward for thousands of years.
All that would remain of the Sun would be a rapidly spinning neutron star, or maybe even a stellar black hole. But of course, this is not to be our Sun’s fate. Given its mass, it will eventually collapse into a white star until it burns itself out. And of course, this won’t be happening for another 6 billion years or so. By that point, humanity will either be long dead or have moved on. In the meantime, we have plenty of days of sunshine to look forward to!
Flashback to 1995: Clinton was in the White House, Star Trek Voyager premiered, we all carried pagers in the pre-mobile phone era, and Windows 95 and the Internet itself was shiny and new to most of us. It was also on this day in late 1995 when our premier eyes on the Sun—The SOlar Heliospheric Observatory (SOHO)—was launched. A joint mission between NASA and the European Space Agency, SOHO lit up the pre-dawn sky over the Florida Space Coast as it headed space-ward atop an Atlas IIAS rocket at 3:08 AM EST from launch complex 39B at Cape Canaveral Air Force Station.
Envisioning SOHO
SOHO on Earth
There aren’t a whole lot of 20th century spacecraft still in operation; SOHO joins the ranks of Hubble and the twin Voyager spacecraft as platforms from another era that have long exceeded their operational lives. Seriously, think back to what YOU were doing in 1995, and what sort of technology graced your desktop. Heck, just thinking of how many iterations of mobile phones spanned the last 20 years is a bit mind-bending. A generation of solar astronomers have grown up with SOHO, and the space-based observatory has consistently came through for researchers and scientists, delivering more bang for the buck.
“SOHO has been truly extraordinary and revolutionary in countless ways,” says astrophysicist Karl Battams at the Naval Research Laboratory in Washington D.C. “SOHO has completely changed our way of thinking about the Sun, solar active regions, eruptive events, and so much more. I honestly can’t think of a more broadly influential space mission than SOHO.”
SOHO has monitored the Sun now for the complete solar cycle #23 and well into the ongoing solar cycle #24. SOHO is a veritable Swiss Army Knife for solar astrophysics, not only monitoring the Sun across optical and ultraviolet wavelengths, but also employing the Michelson Doppler Imager to record magnetogram data and the Large Angle Spectrometric Coronograph (LASCO) able to create an artificial solar eclipse and monitor the pearly white corona of the Sun.
Peering into the solar interior.
SOHO observes the Sun from its perch one million miles sunward located at the L1 Sun-Earth point. It actually circles this point in space in what is known as a lissajous, or ‘halo’ orbit.
SOHO has revolutionized solar physics and the way we perceive our host star. We nearly lost SOHO early on in its career in 1998, when gyroscope failures caused the spacecraft to lose a lock on the Sun, sending it into a lazy one revolution per minute spin. Quick thinking by engineers led to SOHO using its reaction wheels as a virtual gyroscope, the first spacecraft to do so. SOHO has used this ad hoc method to point sunward ever since. SOHO was also on hand to document the 2003 Halloween flares, the demise of comet ISON on U.S. Thanksgiving Day 2013, and the deep and strangely profound solar minimum that marked the transition from solar cycle 23 to 24.
What was your favorite SOHO moment?
A massive sunspot witnessed by SOHO in 2000, compared to the Earth.
SOHO is also a champion comet hunter, recently topping an amazing 3000 comets and counting. Though it wasn’t designed to hunt for sungrazers, SOHO routinely sees ’em via its LASCO C2 and C3 cameras, as well as planets and background stars near the Sun. The effort to hunt for sungrazing comets crossing the field of view of SOHO’s LASCO C3 and C2 cameras represents one of the earliest crowd-sourced efforts to do volunteer science online. SOHO has discovered enough comets to characterize and classify the Kreutz family of sungrazers, and much of this effort is volunteer-based. SOHO grew up with the internet, and the images and data made publicly available are an invaluable resource that we now often take for granted.
A ‘neat’ image… Comet NEAT photobombs the view of SOHO’s LASCO C3 camera.
NASA/ESA has extended SOHO’s current mission out to the end of 2016. With any luck, SOHO will complete solar cycle 24, and take us into cycle 25 to boot.
“Right now, it (SOHO) is operating in a minimally funded mode, with the bulk of its telemetry dedicated solely to the LASCO coronagraph,” Battams told Universe Today. “Many of its instruments have now been superseded by instruments on other missions. As of today it remains healthy, and I think that’s a testament to the amazing collaboration between ESA and NASA. Together, they’ve kept a spacecraft designed for a two-year mission operating for twenty years.”
Today, missions such as the Solar Dynamics Observatory, Hinode, and Proba-2 have joined SOHO in watching the Sun around the clock. The solar occulting disk capabilities of SOHO’s LASCO C2 and C3 camera remains unique, though ESA’s Proba-3 mission launching in 2018 will feature a free-flying solar occulting disk.
Happy 20th SOHO… you’ve taught us lots about our often tempestuous host star.
Ever wonder what happens on the surface of other stars?
An amazing animation was released this week by astronomers at the Leibniz Institute for Astrophysics (AIP) in Potsam Germany, showing massive sunspot activity on the variable star XX Trianguli (HD 12545). And while ‘starspot’ activity has been seen on this and other stars before, this represents the first movie depicting the evolution of stellar surface activity beyond our solar system.
“We can see our first application as a prototype for upcoming stellar cycle studies, as it enables the prediction of a magnetic-activity cycle on a dramatically shorter timescale than usual,” says Leibniz Institute for Astrophysics Potsdam astronomer Andreas Kunstler in a recent press release.
The images were the result of a long term analysis of the star carried out using the twin STELLA (STELLar Activity) robotic telescopes based on Tenerife in the Canary Islands. The spectroscopic data was gathered over a period of six years, and this video demonstrates that, while other stars do indeed have sunspot cycles similar to our Sun, those of massive stars such as XX Tri are much more intense than any we could imagine here in our own solar system.
STELLA on the hunt. Image credit:
Even the largest and closest of stars have a minuscule angular diameter –measured in milliarcseconds (mas, our 1/1,000ths of an arc second)—in size. For example, we know from lunar occultation timing experiments that the bright star Antares at 550 light years distant and 5 times the radius of our Sun is about 41 mas in size. At an estimated 910 to 1,500 light years distant and 10 times the radius of our Sun, XX Tri is probably comparable, at about 20 mas in size.
That’s tiny from our perspective, though the massive starspot depicted must be truly gigantic to see up close.
To image something on that scale, astronomers use a technique known as Doppler tomography gathered from high-resolution spectra. Over said six year span covering a period from July 2006 to April 2012, 667 viable spectra were gathered, covering 86 total rotational periods for the star. Incidentally, that’s not much longer than the average equatorial rotational period of our Sun—remember, as a ball of gas, the rotational period of our Sun varies with solar latitude—at about 22 days.
Our relatively sedate host star. Image credit: Dave Dickinson
The views compiled by the team show a pole facing, Mercator projection, and a spherical ‘real view’ of the star. Of course, to see XX Tri up close would be amazing, if a not a little intimidating with those massive, angry spots dappling its surface.
Watch the animation, and you can see the changing morphology of the spots, as they decay, merge and defuse again. Just how permanent is that massive pole spot? Why are we seeing spots across the pole of a star like XX Tri at all, something we never see on the Sun? Do other stars follow something analogous to Spörer’s Law and their own version of the 11-year sunspot cycle that we see on Sol?
Capabilities such as those demonstrated by STELLA may soon crack these questions wide open. Composed of two 1.2 meter robotic telescopes jointly operated by the Institute for Astrophysics at Potsdam and the Instituto de Astrofísica de Canarias (IAC), STELLA combines the capability of a wide-field photometric imager with that of a high-resolution spectrograph, ideal for this sort of analysis of remote stellar surfaces.
A diagram featuring the twin STELLA instruments. Image credit: Leibniz Institute for Astrophysics Potsdam (AIP)
Hey, here’s a crazy idea: turn STELLA loose on KIC 8462852 and see if the hypothesized ‘exo-comets’ or ‘alien mega-structures’ turn up… though it weighs in much smaller than XX Tri at 1.4x solar masses, KIC 8462852 is also about 1,400 light years distant, perhaps just doable using high resolution spectroscopy…
The location of XX Tri (also known as HIP 9630) in the northern sky. Image credit: created by the author using Stellarium planetarium software
Want to see XX Tri for yourself? An RS Canum Venaticorum variable orange giant star (spectral type K0 III) located in the constellation of Triangulum the Triangle, XX Tri shines at magnitude +8.5 and varies over about half a magnitude in brightness. Its coordinates are:
Right Ascension: 2 hours 3 minutes 47 seconds
Declination: 35 North 35 minutes 29 seconds
The more we learn about other stars, the more we understand about how to live with our very own sometimes placid, sometimes tempestuous host star.
Does XX Trianguli look familiar? That might be because it was featured as the Astronomy Picture of the Day as ‘imaged’ by the Coude Feed Telescope on Kitt Peak way back when on November 2nd, 2003.
The Sun. Credit: NASA & European Space Agency (ESA)
The Sun is the center of the Solar System and the source of all life and energy here on Earth. It accounts for more than 99.86% of the mass of the Solar System and it’s gravity dominates all the planets and objects that orbit it. Since the beginning of history, human beings have understood the Sun’s importance to our world, it’s seasons, the diurnal cycle, and the life-cycle of plants.
Because of this, the Sun has been at the center of many ancient culture’s mythologies and systems of worship. From the Aztecs, Mayans and Incas to the ancient Sumerians, Egyptians, Greeks, Romans and Druids, the Sun was a central deity because it was seen as the bringer of all light and life. In time, our understanding of the Sun has changed and become increasingly empirical. But that has done nothing to diminish it’s significance.
A montage of 31 images taken in less than a second as the International Space Station transits the Sun and a solar prominence. Credit and copyright: Thierry Legault.
When you’re Thierry Legault and you want to challenge yourself, the bar is set pretty high.
“This is a challenge I imagined some time ago,” Legault told Universe Today via email, “but I needed all the right conditions.”
The challenge? Capture a transit of the International Space Station of not just the Sun — which he’s done dozens of times — but in front of a solar prominence.
Legault said the transit of the prominence, which he captured on August 21, 2015, lasted 0.8 seconds. His camera was running at 40 frames per second, and he got about 32 shots in that time.
See a video of the transit in real time, and more, below:
We’ve described in our previous articles how Legault determines the exact location where he needs to be to capture the images he wants by considering the width of the visibility path, and trying to be as close to the center of the path as possible. But this challenge was a bit different.
“I took the last transit data from Calsky, the real position of the prominences, and made angles and distances calculations to place my telescope this time not on the central line of the transit but 1 mile north from it,” Legault said, “to have the ISS passing in front of the largest prominence.”
You can see some of Legault’s stunning and sometimes ground-breaking astrophotography here on Universe Today, such as images of the space shuttle or International Space Station crossing the Sun or Moon, or views of spy satellites in orbit.
If you want to try and master the art of astrophotography, you can learn from Legault by reading his book, “Astrophotography,” which is available on Amazon in a large format book or as a Kindle edition for those who might like to have a lit version while out in the field. It is also available at book retailers like Barnes and Noble and Shop Indie bookstores, or from the publisher, Rocky Nook, here.
A Full Moon in all its horizontal glory. When near the horizon, refraction squeezes the lunar disk into an oval. Scattering removes the shorter wavelengths of white light, leaving the Moon a rich red or orange. Credit: Bob King
Who doesn’t love a Full Moon? Occurring about once a month, they never wear out their welcome. Each one becomes a special event to anticipate. In the summer months, when the Moon rises through the sultry haze, atmosphere and aerosols scatter away so much blue light and green light from its disk, the Moon glows an enticing orange or red.
At Full Moon, we’re also more likely to notice how the denser atmosphere near the horizon squeezes the lunar disk into a crazy hamburger bun shape. It’s caused by atmospheric refraction. Air closest to the horizon refracts more strongly than air near the top edge of the Moon, in effect “lifting” the bottom of the Moon up into the top. Squished light! We also get to see all the nearside maria or “seas” at full phase, while rayed craters like Tycho and Copernicus come into their full glory, looking for all the world like giant spatters of white paint even to the naked eye.
At full phase, the Moon lies directly opposite the Sun on the other side of Earth. Sunlight hits the Moon square on and fully illuminates the Earth-facing hemisphere. Credit: Bob King
Tomorrow night (August 29), the Full Sturgeon Moon rises around sunset across the world. The name comes from the association Great Lakes Indian groups made between the August moon and the best time to catch sturgeon. Next month’s moon is the familiar Harvest Moon; the additional light it provided at this important time of year allowed farmers to harvest into the night.
A Full Moon lies opposite the Sun in the sky exactly like a planet at opposition. Earth is stuck directly between the two orbs. As we look to the west to watch the Sun go down, the Moon creeps up at our back from the eastern horizon. Full Moon is the only time the Moon faces Sun directly – not off to one side or another – as seen from Earth, so the entire disk is illuminated.
The moon provides the perfect backdrop for watching birds migrate at night. Although a small telescope is best, you might see an occasional bird in binoculars, too. Credit: Bob King
If you’re a moonrise watcher like I am, you’ll want to find a place where you can see all the way down to the eastern horizon tomorrow night. You’ll also need the time of moonrise for your city and a pair of binoculars. Sure, you can watch a moonrise without optical aid perfectly well, but you’ll miss all the cool distortions happening across the lunar disk from air turbulence. Birds have also begun their annual migration south. Don’t be surprised if your glass also shows an occasional winged silhouette zipping over those lunar seas.
Because the Moon’s orbit is tilted 5.1° with respect to Earth’s, it normally passes above or below Earth’s shadow with no eclipse — either lunar or solar. Only when the lineup is exact, does the Moon pass directly behind Earth and into its shadow. Credit: Bob King
Next month’s Full Moon is very special. A few times a year, the alignment of Sun, Earth and Moon (in that order) is precise, and the Full Moon dives into Earth’s shadow in total eclipse. That will happen overnight Sunday night-Monday morning September 27-28. This will be the final in the current tetradof four total lunar eclipses, each spaced about six months apart from the other. I think this one will be the best of the bunch. Why?
The totally eclipsed moon on April 15, 2014 from Duluth, Minn. This was the first in the series of four eclipses called a tetrad. September’s totally eclipsed Moon will appear similar. The coloring comes from sunlight grazing the edge of Earth’s atmosphere and refracted by it into the planet’s shadow. Credit: Bob King
Convenient evening viewing hours (CDT times given) for observers in the Americas. Partial eclipse begins at 8:07 p.m., totality lasts from 9:11 – 10:23 p.m. and partial eclipse ends at 11:27 p.m. Those times mean that for many regions, kids can stay up and watch.
The Moon passes more centrally through Earth’s shadow than during the last total eclipse. That means a longer totality and possibly more striking color contrasts.
September’s will be the last total eclipse visible in the Americas until January 31, 2018. Between now and then, there will be a total of four minor penumbral eclipses and one small partial. Slim pickings.
Diagram showing the details of the upcoming total lunar eclipse. The event begins when the Moon treads into Earth’s outer shadow (penumbra) at 7:12 p.m. CDT. Partial phases start at 8:07 and totality at 9:11. Credit: NASA / Fred Espenak
Not only will the Americas enjoy a spectacle, but totality will also be visible from Europe, Africa and parts of Asia. For eastern hemisphere skywatchers, the event will occur during early morning hours of September 28. Universal or UT times for the eclipse are as follows: Partial phase begin at 1:07 a.m., totality from 2:11 – 3:23 a.m. with the end of partial phase at 4:27 a.m.
September 27-28, 2015 eclipse visibility map. Credit: NASA / Fred Espenak
We’ll have much more coverage on the upcoming eclipse in future articles here at Universe Today. I hope this brief look will serve to whet your appetite and help you anticipate what promises to be one of the best astronomical events of 2015.
Need an easy way to remember the order of the planets in our Solar System? The technique used most often to remember such a list is a mnemonic device. This uses the first letter of each planet as the first letter of each word in a sentence. Supposedly, experts say, the sillier the sentence, the easier it is to remember.
So by using the first letters of the planets, (Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune), create a silly but memorable sentence.
Here are a few examples:
My Very Excellent Mother Just Served Us Noodles (or Nachos)
Mercury’s Volcanoes Erupt Mulberry Jam Sandwiches Until Noon
Very Elderly Men Just Snooze Under Newspapers
My Very Efficient Memory Just Summed Up Nine
My Very Easy Method Just Speeds Up Names
My Very Expensive Malamute Jumped Ship Up North
The Sun and planets to scale. Credit: Illustration by Judy Schmidt, texture maps by Björn Jónsson
If you want to remember the planets in order of size, (Jupiter, Saturn, Uranus, Neptune, Earth, Venus Mars, Mercury) you can create a different sentence:
Just Sit Up Now Each Monday Morning
Jack Sailed Under Neath Every Metal Mooring
Rhymes are also a popular technique, albeit they require memorizing more words. But if you’re a poet (and don’t know it) try this:
Amazing Mercury is closest to the Sun,
Hot, hot Venus is the second one,
Earth comes third: it’s not too hot,
Freezing Mars awaits an astronaut,
Jupiter is bigger than all the rest,
Sixth comes Saturn, its rings look best,
Uranus sideways falls and along with Neptune, they are big gas balls.
Or songs can work too. Here are a couple of videos that use songs to remember the planets:
If sentences, rhymes or songs don’t work for you, perhaps you are more of a visual learner, as some people remember visual cues better than words. Try drawing a picture of the planets in order. You don’t have to be an accomplished artist to do this; you can simply draw different circles for each planet and label each one. Sometimes color-coding can help aid your memory. For example, use red for Mars and blue for Neptune. Whatever you decide, try to pick colors that are radically different to avoid confusing them.
Or try using Solar System flash cards or just pictures of the planets printed on a page (here are some great pictures of the planets). This works well because not only are you recalling the names of the planets but also what they look like. Memory experts say the more senses you involve in learning or storing something, the better you will be at recalling it.
Planets made from paper lanterns. Credit: TheSweetestOccasion.com
Maybe you are a hands-on learner. If so, try building a three-dimensional model of the Solar System. Kids, ask your parents or guardians to help you with this, or parents/guardians, this is a fun project to do with your children. You can buy inexpensive Styrofoam balls at your local craft store to create your model, or use paper lanterns and decorate them. Here are several ideas from Pinterest on building a 3-D Solar System Model.
If you are looking for a group project to help a class of children learn the planets, have a contest to see who comes up with the silliest sentence to remember the planets. Additionally, you can have eight children act as the planets while the rest of the class tries to line them up in order. You can find more ideas on NASA’s resources for Educators. You can use these tricks as a starting point and find more ways of remembering the planets that work for you.
