I'm a long-time amateur astronomer and member of the American Association of Variable Star Observers (AAVSO). My observing passions include everything from auroras to Z Cam stars. I also write a daily astronomy blog called Astro Bob. My new book, "Wonders of the Night Sky You Must See Before You Die", a bucket list of essential sky sights, will publish in April. It's currently available for pre-order at Amazon and BN.
This graphic shows the orbit of the planet in the HD 131399 system (red line) and the orbits of the stars (blue lines). The planet orbits the brightest star in the system, HD 131399A. Credit: ESO
This graphic shows the orbit of the planet in the HD 131399 system (red oval) and the orbits of the stars (blue arcs). The planet orbits the brightest star in the triple system, HD 131399A with a period of about 550 years. Credit: ESO
In the famous scene from the Star Wars movie “A New Hope” we recall young Luke Skywalker contemplating his future in the light of a binary sunset on the planet Tatooine. Not so many years later in 2011, astronomers using the Kepler Space Telescope discovered Kepler-16b, the first Tatooine-like planet known to orbit two suns in a binary system. Now astronomers have found a planet in a triple star system where an observer would either experience constant daylight or enjoy triple sunrises and sunsets each day, depending on the seasons, which last longer than human lifetimes.
They used the SPHERE instrument on the European Southern Observatory’s Very Large Telescope to directly image the planet, the first ever found inside a triple-star system. The three stars are named HD 131399A, HD 131399B and HD 131399C in order of decreasing brightness; the planet orbits the brightest and goes by the chunky moniker HD 131399Ab.
This composite image shows the newly discovered exoplanet HD 131399Ab in the triple-star system HD 131399. The image of the planet was obtained with the SPHERE imager. This is the first exoplanet to be discovered by SPHERE and one of very few directly-imaged planets. This picture was created from two separate SPHERE observations: one of the three stars and one to detect the faint planet. The planet appears vastly brighter in this image than in would in reality in comparison to the stars. Credit: ESO/K. Wagner et al.
Located about 320 light-years from Earth in the constellation of Centaurus the Centaur HD 131399Ab is about 16 million years old, making it also one of the youngest exoplanets discovered to date, and one for which we have a direct image. With a temperature of around 1,075° F (580° C) and the mass about four times that of Jupiter, it’s also one of the coldest and least massive directly-imaged exoplanets.
This infrared image of Saturn’s largest moon, Titan, was one of the first produced by the SPHERE instrument soon after it was installed on ESO’s Very Large Telescope in May 2014. This picture shows how effective the adaptive optics system is at revealing fine detail on this tiny disc (just 0.8 arc seconds across). Credit: ESO/J.-L. Beuzit et al./SPHERE Consortium
To pry it loose from the glare of its host suns, a team of astronomers led by the University of Arizona used a state of the art adaptive optics system to give razor-sharp images coupled with SPHERE, an instrument that blocks the light from the central star(s) similar to the way a coronagraph blocks the brilliant solar disk and allows study of the Sun’s corona. Finally, the region around the star is photographed in infrared polarized light to make any putative planets stand out more clearly against the remaining glare.
The planet, HD 131399Ab, is unlike any other known world — its orbit around the brightest of the three stars is by far the widest known within a multi-star system. It was once thought that planets orbiting a multi-star system would be unstable because of the changing gravitational tugs on the planet from the other two stars. Yet this planet remains in orbit instead of getting booted out of the system, leading astronomers to think that planets orbiting multiple stars might be more common that previously thought.
This artist’s impression shows a view of the triple star system HD 131399 from close to the giant planet orbiting in the system. The planet is known appears at the lower-left of the picture. Credit: ESO / L. Calcada
HD 131399Ab orbits HD 131399A, estimated to be 80% more massive than the Sun. Its double-star companions orbit about 300 times the Earth-Sun distance away. For much of the planet’s 550 year orbit, all three stars would appear close together in the sky and set one after the other in unique triple sunsets and sunrises each day. But when the planet reached the other side of its orbit around its host sun, that star and the pair would lie in opposite parts of the sky. As the pair set, the host would rise, bathing HD 131399Ab in near-constant daytime for about one-quarter of its orbit, or roughly 140 Earth-years.
Click to see a wonderful simulation showing how the planet orbits within the trinary system
Planets in multi-star systems are of special interest to astronomers and planetary scientists because they provide an example of how the mechanism of planetary formation functions in these more extreme scenarios. Since multi-star systems are just as common as single stars, so planets may be too.
How would our perspective of the cosmos change I wonder if Earth orbited triple suns instead of a single star? Would the sight deepen our desire for adventure like the fictional Skywalker? Or would we suffer the unlucky accident of being born at the start of a multi-decade long stretch of constant daylight? Wonderful musings for the next clear night under the stars.
Hubble Space Telescope view of a plume high in the martian atmosphere seen in May 1997. Credit: NASA/ESA
A curious plume-like feature was observed on Mars on May 17, 1997 by the Hubble Space Telescope. It is similar to the features detected by amateur astronomers in 2012, although appeared in a different location. Credit: JPL/NASA/STScI
Strange plumes in Mars’ atmosphere first recorded by amateur astronomers four year ago have planetary scientists still scratching their heads. But new data from European Space Agency’s orbiting Mars Express points to coronal mass ejections from the Sun as the culprit.
Mystery plume in Mars’ southern hemisphere photographed and animated by amateur astronomer Wayne Jaeschke on March 20, 2012. The feature lasted for about 10 days. Credit: Wayne Jaeschke
On two occasions in 2012 amateurs photographed cloud-like features rising to altitudes of over 155 miles (250 km) above the same region of Mars. By comparison, similar features seen in the past haven’t exceeded 62 miles (100 km). On March 20th of that year, the cloud developed in less than 10 hours, covered an area of up to 620 x 310 miles (1000 x 500 kilometers), and remained visible for around 10 days.
Back then astronomers hypothesized that ice crystals or even dust whirled high into the Martian atmosphere by seasonal winds might be the cause. However, the extreme altitude is far higher than where typical clouds of frozen carbon dioxide and water are thought to be able to form.
Indeed at those altitudes, we’ve entered Mars’ ionosphere, a rarified region where what air there is has been ionized by solar radiation. At Earth, charged particles from the Sun follow the planet’s global magnetic lines of force into the upper atmosphere to spark the aurora borealis. Might the strange features observed be Martian auroras linked to regions on the surface with stronger-than-usual magnetic fields?
Mars has magnetized rocks in its crust that create localized, patchy magnetic fields (left). In the illustration at right, we see how those fields extend into space above the rocks. At their tops, auroras can form. Credit: NASA
Once upon a very long time ago, Mars may have had a global magnetic field generated by electrical currents in a liquid iron-nickel core much like the Earth’s does today. In the current era, the Red Planet has only residual fields centered over regions of magnetic rocks in its crust.
The top image shows the location of the mysterious plume on Mars, identified within the yellow circle (top image, south is up), along with different views of the changing plume morphology on March 21, 2012. Copyright: W. Jaeschke and D. Parker
Instead of a single, planet-wide field that funnels particles from the Sun into the atmosphere to generate auroras, Mars is peppered with pockets of magnetism, each potentially capable of connecting with the wind of particles from the Sun to spark a modest display of the “northern lights.” Auroras were first discovered on Mars in 2004 by the Mars Express orbiter, but they’re faint compared to the plumes, which were too bright to be considered auroras.
Still, this was a step in the right direction. What was needed was some hard data of a possible Sun-Earth interaction which scientists ultimately found when they looked into plasma and solar wind measurements collected by Mars Express at the time. David Andrews of the Swedish Institute of Space Physics, lead author of a recent paper reporting the Mars Express results, found evidence for a large coronal mass ejection or CME from the Sun striking the martian atmosphere in the right place and at around the right time.
Earth-based observations of the plume on March 21, 2012 (top right) and of Mars Express solar wind observations during March and April 2012 (bottom right). The left-hand graphics show Mars as seen by Mars Express. Green represents the planet’s dayside and gray, the nightside. Magnetic areas of the crust are shown in blue and red. The white box indicates the area in which the plume observations were made. Together, these graphics show that the amateur observations were made during the martian daytime, along the dawn terminator, while the spacecraft observations were made along the dusk terminator, approximately half a martian ‘day’ later.The black line on Mars is the ground track of the Mars Express orbiter. The plot on the lower right shows Mars Express’s solar wind measurements. The peaks marked by the horizontal blue line indicate the increase in the solar wind properties as a result of the impact of the coronal mass ejection. Credit: Copyright: visual images: D. Parker (large Mars image and bottom inset) & W. Jaeschke (top inset). All other graphics courtesy D. Andrews
CMEs are enormous explosions of hot solar plasma — a soup of electrons and protons — entwined with magnetic fields that blast off the Sun and can touch off geomagnetic storms and auroras when they encounter the Earth and other planets.
“Our plasma observations tell us that there was a space weather event large enough to impact Mars and increase the escape of plasma from the planet’s atmosphere,” said Andrews. Indeed, the plume was seen along the day–night boundary, over a region of known strong crustal magnetic fields.
Locations of 19 auroral detections (white circles) made by Mars Express during 113 nightside orbits between 2004 and 2014, over locations already known to be associated with residual crustal magnetism. The data is superimposed on the magnetic field line structure (from NASA’s Mars Global Surveyor) where red indicates closed magnetic field lines, grading through yellow, green and blue to open field lines in purple. The auroral emissions are very short-lived, they are not seen to repeat in the same locations. Credit: ESA / Copyright Based on data from J-C. Gérard et al (2015)
But again, a Mars aurora wouldn’t be expected to shine so brightly. That’s why Andrews thinks that the CME prompted a disturbance in the ionosphere large enough to affect dust and ice grains below:
“One idea is that a fast-traveling CME causes a significant perturbation in the ionosphere resulting in dust and ice grains residing at high altitudes in the upper atmosphere being pushed around by the ionospheric plasma and magnetic fields, and then lofted to even higher altitudes by electrical charging,” according to Andrews.
A colossal CME, composed of a magnetized cloud of subatomic particles, departs the Sun in February 2000. Credit NASA/ESA/SOHO
With enough dust and ice twinkling high above the planet’s surface, it might be possible for observers on Earth to see the result as a wispy plume of light. Plumes appear to be rare on Mars as a search through the archives has revealed. The only other, seen by the Hubble Space Telescope in May 1997, occurred when a CME was hitting the Earth at the same time. Unfortunately, there’s no information from Mars orbiters at the time about its effect on that planet.
Observers on Earth and orbiters zipping around the Red Planet continue to monitor Mars for recurrences. Scientists also plan to use the webcam on Mars Express for more frequent coverage. Like a dog with a bone, once scientists get a bite on a tasty mystery, they won’t be letting go anytime soon.
Mars snapped with the Hubble Space Telescope on May 12 just days before opposition. Credit: NASA/ESA
On May 12, the Hubble Space Telescope took this photo of Mars. Some prominent features of the planet are clearly visible: the ancient and inactive shield volcano Syrtis Major (far right and partly covered by clouds); the heavily eroded Arabia Terra in the center of the image; the dark features of Sinus Sabaeous and Sinus Meridiani below center and the small north polar cap (top).
We’re in store for an exciting weekend as the Earth and Mars get closer to each other than at any time in the last ten years. To take advantage of this special opportunity, the Hubble Space Telescope, normally busy eyeing remote galaxies, was pointed at our next door neighbor to capture this lovely close-up image.
Opposition occurs when Mars and Earth line up on the same side of the Sun. The two planets are closest together around that time. Mars opposition occurs on May 22, when the planet will shine at magnitude -2.0 and with an apparent diameter of 18.6 arc seconds, its largest in over 10 years. Credit: Bob King
As Universe Today writer David Dickinson described in his excellent Mars guide, the planet reaches opposition on Sunday morning May 22. That’s when the planet will be directly opposite the Sun in the sky and rise in the east around the same time the Sun sets in the west. Earth sits squarely in between. Opposition also marks the planet’s close approach to Earth, so that Mars appears bigger and brighter in the sky than usual. A perfect time for detailed studies whether through both amateur and professional telescopes.
Although opposition for most outer planets coincides with the date of closest approach, that’s not true in the case of Mars. If Mars is moving away from the Sun in its orbit when Earth laps it, closest approach occurs a few days before opposition. But if the planet is moving toward the Sun when our planet passes by, closest approach occurs a few days after opposition. This time around, Mars is headed sunward, so the date of closest approach of the two planets occurs on May 30.
It’s all goes back to Mars’ more eccentric orbit, which causes even a few days worth of its orbital travels to make a difference in the distance between the two planets when Earth is nearby. On May 22, Mars will be 47.4 million miles away vs. 46.77 million on the 30th, a difference of about 700,000 miles.
Every 26 months Mars reaches opposition. This mosaic of photos taken by Hubble show seven different oppositions since 1995. Because of Mars’ elliptical orbit, it shows variations in apparent size from opposition to opposition. Mars was the closest in 2003 when it came within 34.8 million miles (56 million kilometer) of Earth. The part of Mars that is tilted towards the Earth also shifts over time, resulting in the changing visibility of the polar caps. Clouds and dust storms, as well as the size of the ice caps, can change the appearance of Mars on time scales of days, weeks, and months. Other features of Mars, such as some of the large dark markings, have remained unchanged for centuries. Credit: NASA/ESA
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On May 12, Hubble took advantage of this favorable alignment and turned its gaze towards Mars to take an image of our rusty-hued neighbor, From this distance the telescope could see Martian features as small as 18.6 miles (30 kilometers) across. The image shows a sharp, natural-color view of Mars and reveals several prominent geological features, from smaller mountains and erosion channels to immense canyons and volcanoes.
Some of the more prominent features in the Hubble photo of Mars are marked here. Limb hazes are visible in modest-sized telescopes as a pale edging around the planet’s rim. The planet’s distinctive red color is created by rust. Billions of years ago, it’s thought that ultraviolet light from the Sun split water in the Martian atmosphere into hydrogen and oxygen. The hydrogen escaped, but the oxygen combined with iron in the planet’s surface rocks to form iron oxide or rust. Many of Earth’s red rock formations are similarly “oxidized.” Credit: NASA/ESA
The orange area in the center of the image is Arabia Terra, a vast upland region. The landscape is densely cratered and heavily eroded, indicating that it could be among the oldest features on the planet.
While the polar caps aren’t currently visible, telescope users will be treated to nice views of India-shaped Syrtis Major. The large crater Hellas at the top (south) limb is currently covered in winter clouds. Credit: Christopher Go
South of Arabia Terra, running east to west along the equator, is the long dark feature named Sinus Sabaeus that terminates in a larger, dark blob called and Sinus Meridiani. These darker regions are covered by bedrock from ancient lava flows and other volcanic features. An extended blanket of clouds can be seen over the southern polar cap where it’s late winter. The icy northern polar cap has receded to a comparatively small size because it’s now late summer in the northern hemisphere.
Mars on May 2 shows Syrtis Major off to the east (right). Crossing the top of the photo are Mare Tyrrhenum to the right of the planet’s central meridian and Mare Cimmerium, to the left. Credit: Christopher Go
So the question now is how much will you see as we pull up alongside the Red Planet this weekend? With the naked eye, Mars looks like a fiery “star” in the head of Scorpius the scorpion not far from the similarly-colored Antares, the brightest star in the constellation. It’s unmistakable. Even through the haze it caught my eye last night, rising in the southeast around 10 o’clock with its signature hue.
Through a 4-inch or larger telescope, you can see limb hazes/clouds and prominent dark features such as Syrtis Major, Utopia, clouds over Hellas, Mare Tyrrhenum (to the west of Syrtis Major) and Mare Cimmerium (west of M. Tyrrhenum).
Expert astroimager Damian Peach created this photographic map of Mars labeled with its most prominent features visible in amateur telescopes. Click for a large version. Credit: Damian Peach
These features observers across the America will see this week and early next between about 11 p.m. and 2 a.m. local time. As Mars rotation period is 37 minutes longer than Earth’s, these markings will gradually rotate out of view, and we’ll see the opposite hemisphere in the coming weeks. You can use the map to help you identify particular features or Sky & Telescope’s handy Mars Profilerto know which side of the planet’s visible when.
The Full Moon, Mars only hours before opposition, Saturn and Antares gather in the southern sky for a special, diamond-shaped grouping. Diagram: Bob King, source: Stellarium
To top off all the good stuff happening with Mars, the Full Flower Moon will join up with that planet, Saturn and Antares Saturday night May 21 to create what I like to call a “diamond of celestial lights” visible all night. Don’t miss it!
Italian astronomer Gianluca Masi will offer up two online Mars observing sessions in the coming week, on May 22 and 30, starting at 5 p.m. CDT (22:00 UT). Yet another opportunity to get acquainted with your inner Mars.
Views of the rotating jet in comet 252P/LINEAR on April 4, 2016. Credit: Credit: NASA, ESA, and J.-Y. Li (Planetary Science Institute)
These photos, taken on April 4, 2016 over the span of 4 1/2 hours, reveal a narrow, well-defined jet of dust ejected by the comet’s icy nucleus. With a diameter of only about a mile, the nucleus is too small for Hubble to see. The jet is illuminated by sunlight and changes direction like the hour hand on a clock as the comet spins on its axis. Credit: NASA, ESA, and J.-Y. Li (Planetary Science Institute)
Remember 252P/LINEAR? This comet appeared low in the morning sky last month and for a short time grew bright enough to see with the naked eye from a dark site. 252P swept closest to Earth on March 21, passing just 3.3 million miles away or about 14 times the distance between our planet and the moon. Since then, it’s been gradually pulling away and fading though it remains bright enough to see in small telescope during late evening hours.
252P LINEAR looks like a big fuzzy ball in this photo taken on April 30. The comet is located in Ophiuchus and rises in the eastern sky at nightfall. At this scale, the jet shown in the Hubble photos is too tiny to see. See map below to find the comet yourself. Credit: Rolando Ligustri
While amateurs set their clocks to catch the comet before dawn, astronomers using NASA’s Hubble Space Telescope captured close-up photos of it two weeks after closest approach. The images reveal a narrow, well-defined jet of dust ejected by the comet’s fragile, icy nucleus spinning like a water jet from a rotating lawn sprinkler. These observations also represent the closest celestial object Hubble has observed other than the moon.
Want to get a good look at a comet’s tiny nucleus and its jets of vapor and dust? Get up close in the spaceship. This photo was taken by the European Space Agency’s Rosetta probe which has been orbiting Comet 67P/Churyumov-Gerasimenko since the fall of 2014. Credit: ESA
Sunlight warms a comet’s nucleus, vaporizing ices below the surface. In a confined space, the pressure of the vapor builds and builds until it finds a crack or weakness in the comet’s crust and blasts into space like water from a whale’s blowhole. Dust and other gases go along for the ride. Some of the dust drifts back down to coat the surface, some into space to be shaped by the pressure of sunlight into a dust tail.
This map shows the path — marked off every five nights at 11:30 p.m. CDT (4:30 UT) — of 252P/LINEAR along the border of Ophiuchus and Hercules through the end of June. Bright stars are labeled by Greek letter or number. Stars shown to magnitude 8.5. Click to enlarge. Diagram: Bob King, source: Chris Marriott’s SkyMap
You can still see 252P/LINEAR if you have a 4-inch or larger telescope. Right now it’s a little brighter than magnitude +9 as it slowly arcs along the border of Ophiuchus and Hercules. With the moon getting brighter and brighter as it fills toward full, tonight and tomorrow night will be best for viewing the comet. After that you’re best to wait till after the May 21st full moon when darkness returns to the evening sky. 252P will spend much of the next couple weeks near the 3rd magnitude star Kappa Ophiuchi, a convenient guidepost for aiming your telescope in the comet’s direction.
Get oriented on where to look for the comet by first using this map, which shows the sky facing southeast around 11-11:30 p.m. local daylight time in mid-May. Mars and Saturn make excellent guides to help you find Kappa Oph, located very near the comet. Diagram: Bob King , source: Stellarium
While you probably won’t see any jets in amateur telescopes, they’re there all the same and helped created this comet’s distinctive and large, fuzzy coma. Happy hunting!
The full sequence of images of the spinning jet in 252P/LINEAR seen by Hubble. Credit: NASA, ESA, and Z. Levay (STScI)
The magnetic field and electric currents in and around Earth generate complex forces that have immeasurable impact on every day life. The field can be thought of as a huge bubble -- called the magnetosphere -- protecting us from cosmic radiation and charged particles that bombard Earth in solar winds. Credit: ESA/ATG medialab
Illustration of the invisible magnetic field lines generated by the Earth. Unlike a classic bar magnet, the matter governing Earth’s magnetic field moves around. The flow of liquid iron in Earth’s core creates electric currents, which in turn creates the magnetic field. Credit and copyright: Peter Reid, University of Edinburgh
Although invisible to the eye, Earth’s magnetic field plays a huge role in both keeping us safe from the ever-present solar and cosmic winds while making possible the opportunity to witness incredible displays of the northern lights. Like a giant bar magnet, if you could sprinkle iron filings around the entire Earth, the particles would align to reveal the nested arcs of our magnetic domain. The same field makes your compass needle align north to south.
We can picture our magnetic domain as a huge bubble, protecting us from cosmic radiation and electrically charged atomic particles that bombard Earth in solar winds. Satellites and instruments on the ground keep a constant watch over this bubble of magnetic energy surrounding our planet. For good reason: it’s always changing.
Earth’s magnetic field is thought to be generated by an ocean of super-heated, swirling liquid iron that makes up its the outer core 1,860 miles (3000 kilometers) under our feet. Acting like the spinning conductor similar to a bicycle dynamo that powers a headlight, it generates electrical currents and a constantly changing electromagnetic field. Other sources of magnetism come from minerals in Earth’s mantle and crust, while the ionosphere, magnetosphere and oceans also play a role. The three Swarm satellites precisely identify and measure precisely these different magnetic signals. Copyright: ESA/ATG Medialab
The European Space Agency’s Swarm satellite trio, launched at the end of 2013, has been busy measuring and untangling the different magnetic signals from Earth’s core, mantle, crust, oceans, ionosphere (upper atmosphere where the aurora occurs) and magnetosphere, the name given to the region of space dominated by Earth’s magnetic field.
At this week’s Living Planet Symposiumin Prague, Czech Republic, new results from the constellation of Swarm satellites show where our protective field is weakening and strengthening, and how fast these changes are taking place.
Based on results from ESA’s Swarm mission, the animation shows how the strength of Earth’s magnetic field has changed between 1999 and mid-2016. Blue depicts where the field is weak and red shows regions where the field is strong. The field has weakened by about 3.5% at high latitudes over North America, while it has grown about 2% stronger over Asia. Watch also the migration of the north geomagnetic pole (white dot).
Between 1999 and May 2016 the changes are obvious. In the image above, blue depicts where the field is weak and red shows regions where it is strong. As well as recent data from the Swarm constellation, information from the CHAMPand Ørsted satellites were also used to create the map.
The animation shows changes in the rate at which Earth’s magnetic field strengthened and weakened between 2000 and 2015. Regions where changes in the field have slowed are shown in blue while red shows where changes sped up. For example, in 2015 changes in the field have slowed near South Africa but changes got faster over Asia. This map has been compiled using data from ESA’s Swarm mission.
The animation show that overall the field has weakened by about 3.5% at high latitudes over North America, while it has strengthened about 2% over Asia. The region where the field is at its weakest – the South Atlantic Anomaly – has moved steadily westward and weakened further by about 2%. Moreover, the magnetic north pole is also on the move east, towards Asia. Unlike the north and south geographic poles, the magnetic poles wander in an erratic way, obeying the movement of sloshing liquid iron and nickel in Earth’s outer core. More on that in a minute.
The ‘South Atlantic Anomaly’ refers to an area where Earth’s protective magnetic shield is weak. The white spots on this map indicate where electronic equipment on a TOPEX/Poseidon satellite was affected by radiation as it orbited above. The colors indicate the strength of the planet’s magnetic field with red the highest value and blue the lowest. Credit: ESA/DTU Space
The anomaly is a region over above South America, about 125-186 miles (200 – 300 kilometers) off the coast of Brazil, and extending over much of South America, where the inner Van Allen radiation belt dips just 125-500 miles (200 – 800 kilometers) above the Earth’s surface. Satellites passing through the anomaly experience extra-strong doses of radiation from fast-moving, charged particles.
This cutaway of planet Earth shows the familiar exterior of air, water and land as well as the interior: from the mantle down to the outer and inner cores. Currents in hot, liquid iron-nickel in the outer core create our planet’s protective but fluctuating magnetic field. Credit: Kelvinsong / Wikipedia
The magnetic field is thought to be produced largely by an ocean of molten, swirling liquid iron that makes up our planet’s outer core, 1,860 miles (3000 kilometers) under our feet. As the fluid churns inside the rotating Earth, it acts like a bicycle dynamo or steam turbine. Flowing material within the outer core generates electrical currents and a continuously changing electromagnetic field. It’s thought that changes in our planet’s magnetic field are related to the speed and direction of the flow of liquid iron and nickel in the outer core.
Chris Finlay, senior scientist at DTU Space in Denmark, said, “Swarm data are now enabling us to map detailed changes in Earth’s magnetic field. Unexpectedly, we are finding rapid localized field changes that seem to be a result of accelerations of liquid metal flowing within the core.”
The magnetic field and electric currents in and around Earth generate complex forces that have immeasurable impact on every day life. The field can be thought of as a huge bubble, protecting us from cosmic radiation and charged particles that bombard Earth in solar winds. It’s shaped by winds of particles blowing from the sun called the solar wind, the reason it’s flattened on the “sun-side” and swept out into a long tail on the opposite side of the Earth. Credit: ESA/ATG medialab
Further results are expected to yield a better understanding as why the field is weakening in some places, and globally. We know that over millions of years, magnetic poles can actually flip with north becoming south and south north. It’s possible that the current speed up in the weakening of the global field might mean it’s ready to flip.
Although there’s no evidence previous flips affected life in a negative way, one thing’s for sure. If you wake up one morning and find your compass needle points south instead of north, it’s happened.
A coronal aurora twists overhead in this photo taken early on May 8, 2016 from near Duluth, Minnesota. Credit: Bob King
Skywatchers across the northern tier of states, the Midwest and southern Canada were treated to a spectacular display of the aurora borealis last night. More may be on tap for tonight — in honor of Mother’s Day of course! Credit: Bob King
Simple choices can sometimes lead to dramatic turns of events in our lives. Before turning in for the night last night, I opened the front door for one last look at the night sky. A brighter-than-normal auroral arc arched over the northern horizon. Although no geomagnetic activity had been forecast, there was something about that arc that hinted of possibility.
It was 11:30 at the time, and it would have been easy to go to bed, but I figured one quick drive north for a better look couldn’t hurt. Ten minutes later the sky exploded. The arc subdivided into individual pillars of light that stretched by degrees until they reached the zenith and beyond. Rhythmic ripples of light – much like the regular beat of waves on a beach — pulsed upward through the display. You can’t see a chill going up your spine, but if you could, this is what it would look like.
A coronal aurora twists overhead in this photo taken around 12:15 a.m. on May 8 from near Duluth, Minn. What this photo and the others don’t show is how fast parts of the display flashed and flickered. Shapes would form, disappear and reform in seconds. Credit: Bob King
Auroras can be caused by huge eruptions of subatomic particles from the Sun’s corona called CMEs or coronal mass ejections, but they can also be sparked by holes in the solar magnetic canopy. Coronal holes show up as blank regions in photos of the Sun taken in far ultraviolet and X-ray light. Bright magnetic loops restrain the constant leakage of electrons and protons from the Sun called the solar wind. But holes allow these particles to fly away into space at high speed. Last night’s aurora traces its origin back to one of these holes.
Both a bar magnet (left) and Earth are surrounded by magnetic fields with north and south poles. Earth’s field is shaped by charged particles – electrons and protons – flowing from the sun called the solar wind. Credit: Andy Washnik (left) and NASA
The subatomic particles in the gusty wind come bundled with their own magnetic field with a plus or positive pole and a minus or negative pole. Recall that an ordinary bar magnet also has a “+” and “-” pole, and that like poles repel and opposite poles attract. Earth likewise has magnetic poles which anchor a large bubble of magnetism around the planet called the magnetosphere.
Visualization of the solar wind encountering Earth’s magnetic “defenses” known as the magnetosphere. Clouds of southward-pointing plasma are able to peel back layers of the Sun-facing bubble and stack them into layers on the planet’s nightside (center, right). The layers can be squeezed tightly enough to reconnect and deliver solar electrons (yellow sparkles) directly into the upper atmosphere to create the aurora. Credit: JPL
Field lines in the magnetosphere — those invisible lines of magnetic force around every magnet — point toward the north pole. When the field lines in the solar wind also point north, there’s little interaction between the two, almost like two magnets repelling one another. But if the cloud’s lines of magnetic force point south, they can link directly into Earth’s magnetic field like two magnets snapping together. Particles, primarily electrons, stream willy-nilly at high speed down Earth’s magnetic field lines like a zillion firefighters zipping down fire poles. They crash directly into molecules and atoms of oxygen and nitrogen around 60-100 miles overhead, which absorb the energy and then release it moments later in bursts of green and red light.
View of the eastern sky during the peak of this morning’s aurora. Credit: Bob King
So do great forces act on the tiniest of things to produce a vibrant display of northern lights. Last night’s show began at nightfall and lasted into dawn. Good news! The latest forecast calls for another round of aurora tonight from about 7 p.m. to 1 a.m. CDT (0-6 hours UT). Only minor G1 storming (K index =5) is expected, but that was last night’s expectation, too. Like the weather, the aurora can be tricky to pin down. Instead of a G1, we got a G3 or strong storm. No one’s complaining.
So if you’re looking for that perfect last minute Mother’s Day gift, take your mom to a place with a good view of the northern sky and start looking at the end of dusk for activity. Displays often begin with a low, “quiet” arc and amp up from there.
The camera recorded pale purple, red and green, but the primary color visible to the eye was green. Cameras capture far more color than what the naked eye sees because even faint colors increase in intensity during a time exposure. Details: ISO 800, f/2.8, 13 seconds. Credit: Bob King
Aurora or not, tomorrow features a big event many of us have anticipated for years — the transit of Mercury. You’ll find everything you’ll need to know in this earlier story, but to recap, Mercury will cross directly in front of the Sun during the late morning-early evening for European observers and from around sunrise (or before) through late morning-early afternoon for skywatchers in the Americas. Because the planet is tiny and the Sun deadly bright, you’ll need a small telescope capped with a safe solar filter to watch the event. Remember, never look directly at the Sun at any time.
Nov. 15, 1999 transit of Mercury photographed in UV light by the TRACE satellite. Credit: NASA
If you’re greeted with cloudy skies or live where the transit can’t be seen, be sure to check out astronomer Gianluca Masi’s live stream of the event. He’ll hook you up starting at 11:00 UT (6 a.m. CDT) tomorrow.
The table below includes the times across the major time zones in the continental U.S. for Monday May 9:
A bright Eta Aquarid earthgrazer streaks across the northern lights in May 2013. Credit: Bob King
The Eta Aquarid meteor shower peaks shortly before dawn on Thursday and Friday mornings. The radiant lies in Aquarius near the star Eta. Diagram: Bob King, source: Stellarium
Itching to watch a meteor shower and don’t mind getting up at an early hour? Good because this should be a great year for the annual Eta Aquarid (AY-tuh ah-QWAR-ids) shower which peaks on Thursday and Friday mornings May 5-6. While the shower is best viewed from tropical and southern latitudes, where a single observer might see between 25-40 meteors an hour, northern views won’t be too shabby. Expect to see between 10-15 per hour in the hours before dawn.
Most showers trace their parentage to a particular comet. The Perseids of August originate from dust strewn along the orbit of comet 109P/Swift-Tuttle, which drops by the inner solar system every 133 years after “wintering” for decades just beyond the orbit of Pluto.
Halley’s Comet crossing the Milky Way, taken by the Kuiper Airborne Observatory in New Zealand on April 8-9, 1986. Credit: NASA
The upcoming Eta Aquarids have the best known and arguably most famous parent of all: Halley’s Comet. Twice each year, Earth’s orbital path intersects dust and minute rock particles strewn by Halley during its cyclic 76-year journey from just beyond Uranus to within the orbit of Venus.
Our first pass through Halley’s remains happens this week, the second in late October during the Orionid meteor shower. Like bugs hitting a windshield, the grains meet their demise when they smash into the atmosphere at 147,000 mph (237,000 km/hr) and fire up for a brief moment as meteors. Most comet grains are only crumb-sized and don’t have a chance of reaching the ground as meteorites. To date, not a single meteorite has ever been positively associated with a particular shower.
A bright, earthgrazing Eta Aquarid streaks across Perseus and through the aurora on May 6, 2013. Because the radiant is low for northern hemisphere observers, earthgrazers – long, bright meteors that come up from near the horizon and have long-lasting trails. Credit: Bob King
The farther south you live, the higher the shower radiant will appear in the sky and the more meteors you’ll spot. A low radiant means less sky where meteors might be seen. But it also means visits from “earthgrazers”. These are meteors that skim or graze the atmosphere at a shallow angle and take many seconds to cross the sky. Several years back, I saw a couple Eta Aquarid earthgrazers during a very active shower. One other plus this year — no moon to trouble the view, making for ideal conditions especially if you can observe from a dark sky.
From mid-northern latitudes the radiant or point in the sky from which the meteors will appear to originate is low in the southeast before dawn. At latitude 50° north the viewing window lasts about 1 1/2 hours before the light of dawn encroaches; at 40° north, it’s a little more than 2 hours. If you live in the southern U.S. you’ll have nearly 3 hours of viewing time with the radiant 35° high.
Meteors in a meteor shower appear to radiate from a point in the distance in identical fashion to the way snow or rain radiates from a point in front of your car when you’re driving. Credit: Bob King
Grab a reclining chair, face east and kick back for an hour or so between 3 and 4:30 a.m. An added bonus this spring season will be hearing the first birdsong as the sky brightens toward the end of your viewing session. And don’t forget the sights above: a spectacular Milky Way arching across the southern sky and the planets of Mars and Saturn paired up in the southwestern sky.
Meteor shower members can appear in any part of the sky, but if you trace their paths in reverse, they’ll all point back to the radiant. Other random meteors you might see are called sporadics and not related to the Eta Aquarids. Meteor showers take on the name of the constellation from which they originate.
Aquarius is home to at least two showers. This one’s called the Eta Aquarids because it emanates from near the star Eta Aquarii. An unrelated shower, the Delta Aquarids, is active in July and early August. Don’t sweat it if weather doesn’t cooperate the next couple mornings. The shower will be active throughout the weekend, too.
The Wow! signal recorded on August 15, 1977. The ones, twos and threes indicate weak background noise. Letters, especially those closer to the end of the alphabet, represent stronger signals. The “6EQUJ5” is read from top to bottom (see graph below) and shows the signal rising from “6” to “U” before dropping back down to “5”. Credit: Big Ear Radio Observatory and North American AstroPhysical Observatory (NAAPO)
The Wow! signal recorded on August 15, 1977. The ones, twos and threes indicate weak background noise. Letters, especially those closer to the end of the alphabet, represent stronger signals. The “6EQUJ5” is read from top to bottom (see graph below) and shows the signal rising from “6” to “U” before dropping back down to “5”. Credit: Big Ear Radio Observatory and North American AstroPhysical Observatory (NAAPO)
Comets get blamed for everything. Pestilence in medieval Europe? Comets! Mass extinctions? Comets! Even the anomalous brightness variations in the Kepler star KIC 8462852 was blamed for a time on comets. Now it looks like the most famous maybe-ET signal ever sifted from the sky, the so-called “Wow!” signal, may also be traced to comets.
Say it ain’t so!
The Big Ear Observatory, on the grounds of Ohio Wesleyan University, operated from 1963-1998. It was part of Ohio State University’s long-running Search for Extraterrestrial (SETI) program. The observatory was torn down in 1998 to make room for a golf course. Credit: Bigear.org / NAAPO
In August 1977, radio astronomer Jerry Ehman was looking through observation data from the Ohio State’s now-defunct Big Ear radio telescope gathered a few days earlier on August 15. He was searching for signals that stood apart from the background noise that might be broadcast by an alien civilization. Since hydrogen is the most common element in the universe and emits energy at the specific frequency of 1420 megahertz (just above the TV and cellphone bands), aliens might adopt it as the “lingua franca” of the cosmos. Scientists here on Earth concentrated radio searches at and around that frequency looking for strong signals that mimicked hydrogen.
Ehman’s searches turned up mostly background noise, but that mid-August night he spotted a surprise — a vertical column with the alphanumerical sequence “6EQUJ5″ that indicated a strong signal at hydrogen’s frequency. Exactly as predicted. Big Ear picked up the signal from near the 5th magnitude star Chi-1 Sagittarii in eastern Sagittarius not far from the globular cluster M55.
Astonished by the find, Ehman pulled out a red pen, circled the sequence and wrote a big “Wow!” in the margin. Ever since, it’s been called the Wow! signal and considered one of the few signals from space that defies explanation. Before we look at how that may change, let’s make sense of the code.
Plot of signal strength vs time of the Wow! signal on August 15, 1977. The signal rose and fell during the 72 seconds observation window. Credit: Maksim Rossomakhin
Each digit on the chart corresponded to a signal intensity from 0 to 35. Anything over “9” was represented by a letter from A to Z. It was probably the “U” that knocked Ehman’s socks off, since it indicated to a radio burst 30 times greater than the background noise of space.
In Big Ear’s 35 years of operation, it was the most intense, unexplainable signal ever recorded. What’s more, it was narrowly focused and very close to hydrogen’s special frequency.
Big Ear listened for just 72 seconds before Earth’s rotation carried the signal’s location out of “view” of antenna. Since the radio array had two feed horns, the transmission was expected to appear three minutes apart in each of the horns, but only a single one ever picked it up.
Despite follow-up observations byEhman and others (more than 100 studies were made of the region) the signal was gone. Never heard from again. Nor has anything else like it ever been recorded anywhere else in the sky.
Careful scrutiny eliminated earthbound possibilities such as aircraft or satellites. Nor would anyone have been transmitting at 1420 MHz since it was within a protected part of the radio spectrum used by astronomers and off-limits to regular broadcasters. The nature of the signal implied a point source somewhere beyond the Earth. But where?
On August 15, 1977, periodic comets 266P/Christensen and 335P/Gibbs would have both been very close to the narrow swath of sky south of Chi Sagittarii where the Wow! signal was received. Could they be implicated? Diagram: Bob King, source: Stellarium
If it really was an attempt at alien contact, why try only once and for so short a time interval? Even Ehman doubted (and still doubts) an extraterrestrial intelligence origin, but a much more recent suggestion made by Prof. Antonio Paris of St. Petersburg College, Florida may offer an answer. Paris earlier worked as an analyst for the U.S. Department of Defense and returned to the “scene of the crime” looking for any likely suspects. After studying astronomical databases, he discovered that two faint comets, 266P/Christensen and 335P/Gibbs, discovered only within the past decade, had been plying the very area of the Wow! signal on August 15, 1977.
A huge cloud of hydrogen surrounded Comet Hale-Bopp when it neared the Sun in 1997. Ultraviolet light, charted by the SWAN instrument on the SOHO spacecraft, revealed that the cloud far exceeded the great comet’s visible tail (inset photo) — 70 times wider than the Sun itself (yellow circle to scale at right). Credit: SOHO (ESA & NASA) and SWAN Consortium / inset: Dennis di Cicco
If you recall, a comet has two or three basic parts: a fuzzy head or coma and one or two tails streaming off behind. Invisible to earthbound telescopes, but showing clearly in orbiting telescopes able to peer into ultraviolet light, the coma is further wrapped in a huge cloud of neutral hydrogen gas.
As the Sun warms a comet’s surface, water ice or H2O vaporizes from its nucleus. Energetic solar UV light breaks down those water molecules into H2 and O. The H2 forms a huge, distended halo that can expand to many times the size of the Sun.
Paris published a paper earlier this year exploring the possibility that the hydrogen envelopes of either or both comets were responsible for the strong 1420 MHz signal snagged by Big Ear. On the surface, this makes sense, but not all astronomers agree. First off, if comets are so radio-bright in hydrogen light, why don’t radio telescopes pick them up more often? They don’t. Second, some astronomers doubt that the signals from these comets would have been strong enough to be picked up by the array.
Image of the full page of the computer printout that contains the “Wow!” signal. Credit: Big Ear Radio Observatory and North American AstroPhysical Observatory (NAAPO)
A quick check on 266P and 335P at the time of the signal show them both around 5 a.u. from the sun (Jupiter’s distance) and extremely faint at magnitudes 22 and 27 respectively. Were they even active enough at those distances to form clouds big enough for the antenna to detect?
Paris knows there’s only one way to find out. Comet 266P/Christensen will swing through the same area again on Jan. 25, 2017, while 335P/Gibbs follows suit on January 7, 2018. Unable to use an existing radio telescope (they’re all booked up!), he’s begun a gofundme campaign to purchase and install a 3-meter radio telescope to track and analyze the spectra of these two comets. The goal is $20,000 and Paris is already well on his way there.
It would be a little bit sad if the Wow! signal turned out to be a “just a comet”, but the possibility of solving a 39-year-old mystery would ultimately be more satisfying, don’t you think?
The Solar and Heliospheric Observatory (SOHO) took these photos of Mercury during its last transit of the Sun on Nov. 8, 2006. Credit: NASA/ESA
Be sure to mark your calendar for May 9. On that day, the Solar System’s most elusive planet will pass directly in front of the Sun. The special event, called a transit, happens infrequently. The last Mercury transit occurred more than 10 years ago, so many of us can’t wait for this next. Remember how cool it was to see Venus transit the Sun in 2008 and again in 2012? The views will be similar with one big difference: Mercury’s a lot smaller and farther away than Venus, so you’ll need a telescope. Not a big scope, but something that magnifies at least 30x. Mercury will span just 10 arc seconds, making it only a sixth as big as Venus.
Two basic types of safe solar filters for telescopes: an aluminized polymer such as Baader film and a dedicated glass solar filter for a particular make and model. Credit: Bob King
Map showing Mercury’s path across the Sun at three key points on May 9: transit start or ingress (left); midpoint and transit end or egress (right). Credit: Tom Ruen with additions by author
If I might make a suggestion, consider buying a sheet of Baader AstroSolar aluminized polyester film and cutting it to size to make your own filter. Although the film’s crinkly texture might make you think it’s flimsy or of poor optical quality, don’t be deceived by appearances.
The material yields both excellent contrast and a pleasing neutral-colored solar image. You can purchase any of several different-sized films to suit your needs either from Astro-Physicsor on Amazon.com. Prices range from $40-90.
Nov. 8, 2006 Transit of Mercury by Dave Kodama
With filter material in hand, just follow these instructions to make your own, snug-fitting telescopic solar filter. Even I can do it, and I kid you not that I’m a total klutz when it comes to building things. If for whatever reason you can’t get a filter, go to Plan B. Put a low power eyepiece in your scope and project an image of the Sun onto a sheet of white paper a foot or two behind the eyepiece.
World map showing where the May 9-10 Mercury transit will be visible. Universal times of the four key contacts (see below for details), mid-transit time and position angle on the Sun’s limb where the planet will first appear and disappear are given at upper left. Credit: Xavier M. Jubier
Since May 9th is a Monday, I’ve a hunch a few of you will be taking the day off. If you can’t, pack a telescope and set it up during lunch hour to share the view with your colleagues. Mercury will spend a leisurely 7 1/2 hours slowly crawling across the Sun’s face, traveling from east to west. The entire transit will be visible across the eastern half of the U.S., most of South America, eastern and central Canada, western Africa and much of western Europe. For the western U.S., Alaska and Hawaii the Sun will rise with the transit already in progress.
Time Zone
Eastern (EDT)
Central (CDT)
Mountain (MDT)
Pacific (PDT)
Transit start
7:12 a.m.
6:12 a.m.
5:12 a.m.
Not visible
Mid-transit
10:57 a.m.
9:57 a.m.
8:57 a.m.
7:57 a.m.
Transit end
2:42 p.m.
1:42 p.m.
12:42 p.m.
11:42 a.m.
Nov. 2006 animation by Hinode. Credit: NASA
At first glance, the planet might look like a small sunspot, but if you look closely, you’ll see it’s a small, perfectly circular black dot compared to the out-of-round sunspots which also possess the classic two-part umbra-penumbra structure. Oh yes, it also moves. Slowly to be sure, but much faster than a typical sunspot which takes nearly two weeks to cross the Sun’s face. With a little luck, a few sunspots will be in view during transit time; compared to midnight Mercury their “black” umbral cores will look deep brown.
I want to alert you to four key times to have your eye glued to the telescope; all occur during the 3 minutes and 12 seconds when Mercury enters and exits the Sun. They’re listed below in Universal Time or UT. To convert UT to EDT, subtract 4 hours; CDT 5 hours; MDT 6 hours, PDT 7 hours, AKDT 8 hours and HST 10 hours.
The black drop effect seen to good advantage during the June 2004 transit of Venus. Credit: Jan Herold
First contact (11:12 UT): Watch for the first hint of Mercury’s globe biting into the Sun just south of the due east point on along the edge of disk’s edge. It’s always a thrill to see an astronomical event forecast years ago happen at precisely the predicted time.
Second contact (11:15 UT): Three minutes and 12 seconds later, the planet’s trailing edge touches the inner limb of the Sun at second contact. Does the planet separate cleanly from the solar limb or briefly remain “connected” by a narrow, black “line”, giving the silhouette a drop-shaped appearance?
This “black drop effect”is caused primarily by diffraction, the bending and interfering of light waves when they pass through the narrow gap between Mercury and the Sun’s edge. You can replicate the effect by bringing your thumb and index finger closer and closer together against a bright backdrop. Immediately before they touch, a black arc will fill the gap between them.
The “black drop effect” can be reproduced by slowly bringing your thumb and index finger together. It’s caused by diffraction combined with blurring from the atmosphere. Credit: Bob King
Third contact (18:39 UT): A minute or less before Mercury’s leading edge touches the opposite limb of the Sun at third contact, watch for the black drop effect to return.
Fourth contact (18:42 UT): The moment the last silhouetted speck of Mercury exits the Sun. Don’t forget to mark your calendar for November 11, 2019, date of the next transit, which also favors observers in the Americas and Europe. After that one, the next won’t happen till 2032.
Other interesting visuals to keep an eye out for is a bright ring or aureole that sometimes appears around the planet caused when our brain exaggerates the contrast of an object against a backdrop of a different brightness. Another spurious optical-brain effect keen-eyed observers can watch for is a central bright spot inside Mercury’s black disk. Use high power to get the best views of these obscure but fascinating phenomena seen by many observers during Mercury transits.
NASA’s Hinode X-ray telescope captured this view of Mercury silhouetted against the Sun’s corona during the Nov. 2006 transit. Similar views are possible in H-alpha light should the planet pass in front of a prominence. Credit: NASA
While I’ve been talking all “white light” observation, the proliferation of relatively inexpensive and portable hydrogen-alpha telescopes in recent years makes them another viewing option with intriguing possibilities. These instruments show solar phenomena beyond the Sun’s limb, including the flaming prominences normally seen only during a total eclipse. That makes it possible to glimpse Mercury minutes in advance of the transit (or minutes after transit end) silhouetted against a prominence or nudging into the rim furry ring of spicules surrounding the outer limb. Wow!
One final note. Be careful never to look directly at the Sun even for a moment during the transit. Keep your eyes safe! When aiming a telescope, the safest and easiest way to center the Sun in the field of view is to shift the scope up and down and back and forth until the shadow the tube casts on the ground is shortest. Try it.
I hope the weather gods smile on you on May 9, but it they don’t or if you live where the transit won’t be visible, Italian astrophysicist Gianluca Masi will stream it live on his Virtual Telescope websitestarting at 11:00 UT (6 a.m CDT).
This artwork shows a rocky planet being bombarded by comets. Image credit: NASA/JPL-Caltech
Artist’s impression of Planet Nine as an ice giant eclipsing the central Milky Way, with a star-like Sun in the distance. Neptune’s orbit is shown as a small ellipse around the Sun. The sky view and appearance are based on the conjectures of its co-proposer, Mike Brown. Credit: Tom Ruen with background from the Milky Way, an ESO image.
Planet Nine, the massive orb proposed to explain the clustered orbits of a half dozen remote Kuiper Belt asteroids, may have a darker side. Periodic mass extinctions on Earth, as indicated in the global fossil record, could be linked to the hypothetical planet according to research published by Daniel Whitmire, a retired professor of astrophysics and faculty member of the University of Arkansas Department of Mathematical Sciences.
Artist’s impression of a collision between Earth and and a comet or asteroid a few kilometers in diameter would release as much energy as several million nuclear weapons detonating and set off a mass extinction event.
Planet Nine is estimated to be 10 times more massive than Earth and currently orbiting about 1,000 times farther away from the Sun. Astronomers have been searching for a potential large planet — for years called “Planet X” — that might be implicated in a handful of major mass extinctions over the past 500 million years. During those times, between 50 and more than 90% of species on Earth perished in a geological heartbeat. The worst, dubbed the Permian-Triassic eventor the Great Dying, occurred 250 million years ago and saw the disappearance of more than 90% of the planet’s life in a geological heartbeat.
Whitmire and his colleague, John Matese, first published research on the connection between Planet X and mass extinctions in the journal Nature in 1985 while working as astrophysicists at the University of Louisiana at Lafayette. They proposed that perturbations from a 10th planet (Pluto was considered a planet back then) could fling a shower of comets from the Kuiper Belt beyond Neptune in Earth’s direction every 28 million years in sync with recorded mass extinctions.
Two other ideas also proposed at the time they wrote their paper — a sister star to the Sun and vertical oscillations of the Sun as it orbits the galaxy — have since been ruled out because the timing is inconsistent with the extinction record. Only Planet X remained as a viable theory, and it’s now gaining renewed attention.
Neil deGrasse Tyson explains precession and Mercury’s orbit
Whitmire and Matese proposed that as Planet X orbits the Sun, its tilted orbit slowly rotates, causing the location of its perihelion (closest point to the Sun) to slowly precess or shift position along its orbit instead of remaining in the same place. Every planet precesses, so no surprises here.
This artist’s conception shows a rocky planet being bombarded by comets. Credit: NASA/JPL-Caltech
But location can make a huge difference. The team proposed that Planet X’s slow orbital gyration directs it into the Kuiper Belt approximately every 27 million years, knocking comets into the inner Solar System. The dislodged comets not only smash into the Earth, they also vaporize and break apart in the inner Solar System as they get nearer to the Sun, reducing the amount of sunlight that reaches the Earth. Add it up, and you have a recipe for cyclic destruction.
One thing to keep in mind is that their research led them to conclude that Planet X was only 5 times as massive as Earth and 100 times farther from the Sun. This doesn’t jive with the size and mass particulars for Planet Nine inferred by researchers Konstantin Batygin and Michael E. Brown at Caltech earlier this year, but until someone tracks the real planet down, there’s room for argument.
Comet and asteroid showers are often cited as possible bad guys in extinction episodes. And why not? We have hard evidence of the asteroid impact that sealed the dinosaurs’s fate 65 million years ago and have seen some six impacts at Jupiter since 1994. It’s cosmic billiards out there folks, and the game’s not over.
