Space Weather Causing Martian Atmospherics

Hubble Space Telescope view of a plume high in the martian atmosphere seen in May 1997. Credit: NASA/ESA

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.

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?

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.

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.

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.

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.

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.

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Friendly Giants Have Cozy Habitable Zones Too

Artist's impression of a red giant star. Credit:NASA/ Walt Feimer

It is an well-known fact that all stars have a lifespan. This begins with their formation, then continues through their Main Sequence phase (which constitutes the majority of their life) before ending in death. In most cases, stars will swell up to several hundred times their normal size as they exit the Main Sequence phase of their life, during which time they will likely consume any planets that orbit closely to them.

However, for planets that orbit the star at greater distances (beyond the system’s “Frost Line“, essentially), conditions might actually become warm enough for them to support life. And according to new research which comes from the Carl Sagan Institute at Cornell University, this situation could last for some star systems into the billions of years, giving rise to entirely new forms of extra-terrestrial life!

In approximately 5.4 billion years from now, our Sun will exit its Main Sequence phase. Having exhausted the hydrogen fuel in its 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, which in turn will cause the Sun to grow in size and enter what is known as the Red Giant-Branch (RGB) phase of its evolution.

This period will begin with our Sun becoming a subgiant, in which it will slowly double in size over the course of about half a billion years. It will then spend the next half a billion years expanding more rapidly, until it is 200 times its current size and several thousands times more luminous. It will then officially be a red giant star, where it will measure approximately 2 AU in diameter, thus reaching beyond Mars’ current orbit.

As we explored in a previous article, planet Earth will not survive our Sun becoming a Red Giant – nor will Mercury, Venus or Mars. But beyond the “Frost Line”, where it is cold enough that volatile compounds – such as water, ammonia, methane, carbon dioxide and carbon monoxide – remain in a frozen state, the remain gas giants, ice giants, and dwarf planets will survive. Not only that, but a massive thaw will set in.

In short, when the star expands, its “habitable zone” will likely do the same, encompassing the orbits of Jupiter and Saturn. When this happens, formerly uninhabitable places – like the Jovian and Cronian moons – could suddenly become inhabitable. The same holds true for many other stars in the Universe, all of which are fated to become Red Giants as they near the end of their lifespans.

However, when our Sun reaches its Red Giant Branch phase, it is only expected to have 120 million years of active life left. This is not quite enough time for new lifeforms to emerge, evolve and become truly complex (i.e. like humans and other species of mammals). But according to a recent research study that appeared in The Astrophysical Journal – titled “Habitable Zone of Post-Main Sequence Stars” – some planets may be able to remain habitable around other red giant stars in our Universe for much longer – up to 9 billion years or more in some cases!

To put that in perspective, nine billion years is close to twice the current age of Earth. So assuming that the worlds in question also have the right mix of elements, they will have ample time to give rise to new and complex forms of life. The study’s lead author, Professor Lisa Kaltennegeris, is also the director of the Carl Sagan Institute. As such, she is no stranger to searching for life in other parts of the Universe. As she explained in a Cornell University press release, which coincided with the publication of the study:

“When a star ages and brightens, the habitable zone moves outward and you’re basically giving a second wind to a planetary system. Currently objects in these outer regions are frozen in our own solar system, like Europa and Enceladus – moons orbiting Jupiter and Saturn… Long after our own plain yellow sun expands to become a red giant star and turns Earth into a sizzling hot wasteland, there are still regions in our solar system – and other solar systems as well – where life might thrive.”

Using existing models of stars and their evolution – i.e. one-dimensional radiative-convective climate and stellar evolutionary models – for their study, Kaltenegger and Ramirez were able to calculate the distances of the habitable zones (HZ) around a series of post-Main Sequence (post-MS) stars. Ramses M. Ramirez – a research associate at the Carl Sagan Institute and co-author of the paper – explained the research process to Universe Today via email:

“We used stellar evolutionary models that tell us how stellar quantities, mainly the brightness, radius, and temperature all change with time as the star ages through the red giant phase. We also used a  climate model to then compute how much energy each star is outputting at the boundaries of the habitable zone. Knowing this and the stellar brightness mentioned above, we can compute the distances to these habitable zone boundaries.”

At the same time, they considered how this kind of stellar evolution could effect the atmosphere of the star’s planets. As a star expands, it loses mass and ejects it outward in the form of solar wind. For planets that orbit close to a star, or those that have low surface gravity, they may find some or all of their atmospheres blasted away. On the other hand, planets with sufficient mass (or positioned at a safe distance) could maintain most of their atmospheres.

“The stellar winds from this mass loss erodes planetary atmospheres, which we also compute as a function of time,” said Ramirez. “As the star loses mass, the solar system conserves angular momentum by moving outwards. So, we also take into account how the orbits move out with time.” By using models that incorporated the rate of stellar and atmospheric loss during the Red Giant Branch (RGB) and Asymptotic Giant Branch (AGB) phases of star, they were able to determine how this would play out for planets that ranged in size from super-Moons to super-Earths.

What they found was that a planet can stay in a post-HS HZ for eons or more, depending on how hot the star is, and figuring for metallicities that are similar to our Sun’s. As Ramirez explained:

“The main result is that the maximum time that a planet can remain in this red giant habitable zone of hot stars is 200 million years. For our coolest star (M1), the maximum time a planet can stay within this red giant habitable zone is 9 billion years. Those results assume metallicity levels similar to those of our Sun. A star with a higher percentage of metals takes longer to fuse the non-metals (H, He..etc) and so these maximum times can increase some more, up to about a factor of two.”

Within the context of our Solar System, this could mean that in a few billion years, worlds like Europa and Enceladus (which are already suspected of having life beneath their icy surfaces) might get a shot at becoming full-fledged habitable worlds. As Ramirez summarized beautifully:

“This means that the post-main-sequence is another potentially interesting phase of stellar evolution from a habitability standpoint. Long after the inner system of planets have been turned into sizzling wastelands by the expanding, growing red giant star, there could be potentially habitable abodes farther away from the chaos. If they are frozen worlds, like Europa, the ice would melt, potentially unveiling any preexisting life. Such pre-existing life may be detectable by future missions/telescopes looking for atmospheric biosignatures.”

But perhaps the most exciting take-away from their research study was their conclusion that planets orbiting within their star’s post-MS habitable zones would be doing so at distances that would make them detectable using direct imaging techniques. So not only are the odds of finding life around older stars better than previously thought, we should have no trouble in spotting them using current exoplanet-hunting techniques!

It is also worth noting that Kaltenegger and Dr. Ramirez have submitted a second paper for publication, in which they provide a list of 23 red giant stars within 100 light-years of Earth. Knowing that these stars, all of which are in our stellar neighborhood, could have life-sustaining worlds within their habitable zones should provide additional opportunities for planet hunters in the coming years.

And be sure to check out this video from Cornellcast, where Prof. Kaltenegger shares what inspires her scientific curiosity and how Cornell’s scientists are working to find proof of extra-terrestrial life.

https://youtu.be/GnnTVjgSuEs

Further Reading: The Astrophysical Journal

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Watch Mercury Transit the Sun in Multiple Wavelengths

A composite image of the May 9, 2016 transit of Mercury across the face of the Sun, as seen by the Solar Dynamics Observatory.  Credit: NASA's Goddard Space Flight Center/SDO/Genna Duberstein

On May 9, 2016, Mercury passed directly between the Sun and Earth. No one had a better view of the event than the space-based Solar Dynamics Observatory, as it had a completely unobstructed view of the entire seven-and-a-half-hour event! This composite image, above, of Mercury’s journey across the Sun was created with visible-light images from the Helioseismic and Magnetic Imager on SDO, and below is a wonderful video of the transit, as it includes views in several different wavelenths (and also some great soaring music sure to stir your soul).

Mercury transits of the Sun happen about 13 times each century, however the next one will occur in only about three and a half years, on November 11, 2019. But then it’s a long dry spell, as the following one won’t occur until November 13, 2032.

Make sure you check out the great gallery of Mercury transit images from around the world compiled by our David Dickinson.

The post Watch Mercury Transit the Sun in Multiple Wavelengths appeared first on Universe Today.

Give Mom the Aurora Tonight / Mercury Transit Update

A coronal aurora twists overhead in this photo taken early on May 8 from near Duluth, Minn. 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.

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.

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.

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.

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.

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.

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:

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.

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Our Sun May Have Eaten A Super Earth For Breakfast

A new paper says that a Super-Earth may have formed in our Solar System and been swallowed by the Sun. Image Credit: ESA/Hubble, M. Kornmesser

Our Solar System sure seems like an orderly place. The orbits of the planets are predictable enough that we can send spacecraft on multi-year journeys to them and they will reliably reach their destinations. But we’ve only been looking at the Solar System for the blink of an eye, cosmically speaking.

The young Solar System was a much different place. Things were much more chaotic before the planets settled into the orbital stability that they now enjoy. There were crashings and smashings aplenty in the early days, as in the case of Theia, the planet that crashed into Earth, creating the Moon.

Now, a new paper from Rebecca G. Martin and Mario Livio at the University of Nevada, Las Vegas, says that our Solar System may have once had an additional planet that perished when it plunged into the Sun. Strangely enough, the evidence for the formation and existence of this planet may be the lack of evidence itself. The planet, which may have been what’s called a Super-Earth, would have formed quite close to the Sun, and then been destroyed when it was drawn into the Sun by gravity.

In the early days of our Solar System, the Sun would have formed in the centre of a mass of gas and dust. Eventually, when it gained enough mass, it came to life in a burst of atomic fusion. Surrounding the Sun was a protoplanetary disk of gas and dust, out of which the planets formed.

[embed]https://www.youtube.com/watch?v=UNPj7e6XJCQ[/embed]

What’s missing in our Solar System is any bodies, or even rocky debris in the zone between Mercury and the Sun. This may seem normal, but the Kepler mission tells us it’s not. In over half of the other solar systems it’s looked at, Kepler has found planets in the same zone where our Solar System has none.

A key part of this idea is that planets don’t always form in situ. That is, they don’t always form at the place where they eventually reach orbital stability. Depending on a number of factors, planets can migrate inward towards their star or outwards away from their star.

Martin and Livio, the authors of the study, think that our Solar System did form a Super-Earth, and rather than it migrating outward, it fell into the Sun. According to them, the Super-Earth most probably formed in the inner regions of our Solar System, on the inside of Mercury’s orbit. The fact that there are no objects there, and no debris of any kind, suggests that the Super-Earth formed close to the Sun, and that its formation cleared that area of any debris. Then, once formed, it fell into the Sun, removing all evidence of its existence.

The authors also note another possible cause for the Super-Earth to have fallen into the Sun. They propose that Jupiter may have migrated inward to about 1.5 AUs from the Sun. At that point, it got locked into resonance with Saturn. Then, both gas giants migrated outward to their current orbits. This process would have shepherded a Super-Earth into the Sun, destroying it.

Some of the thinking behind this whole theory involves the size of the inner terrestrial planets in our Solar System. They’re very small in comparison to other systems studied by the Kepler Mission. If a Super-Earth had formed in the inner part of our System, it would have dominated the accretion of available material, leaving Mercury, Venus, Earth and Mars starved for matter.

A key idea behind this study is what’s known as a dead zone. In terms of a solar system and a protoplanetary disk, a dead zone is a zone of low turbulence which favors the formation of planets. A system with a dead zone would have enough material to allow Super-Earths to form in-situ, and they would not have to migrate inward from further out in the system. However, since large planets like Super-Earths take a long time to fully form, this dead zone would have to be long-lived.

If a protoplanetary disk lacks a dead zone, it is likely too turbulent for the formation of a Super-Earth close to the star. A turbulent protoplanetary disk favors the formation of Super-Earths further out, which would then migrate inwards towards the star. Also, a turbulent disk allows for quicker migration of planets, while a pronounced dead zone inhibits migration.

As the authors say in the conclusion of their study, “The lack of Super–Earths in our solar system is somewhat puzzling given that more than half of observed exoplanetary systems contain one. However, the fact that there is nothing
inside of Mercury’s orbit may not be a coincidence.” They go on to conclude that in our Solar System, the likely scenario is the in situ formation of a Super-Earth which subsequently fell into the Sun.

There are a lot of variables that have to be fine-tuned for this scenario to happen. The young solar system would need a dead zone, the depth of the turbulence in the protoplanetary disk would have to be just right, and the disk would have to be the right temperature. The fact that these things have to be within a certain range may explain why we don’t have a Super-Earth in our system, while over half of the systems studied by Kepler do have one.

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How to Safely Watch Mercury Transit the Sun on May 9

Transit May7_2003 SOHO

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.

That also means  you’ll need a solar filter for your telescope. If you’ve put off buying one, now’s the time to plunk down that credit card. Safe, quality filters are available from many sources including Orion Telescopes, Thousand Oaks Optical, Kendrick Astro Instruments and Amazon.com.

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-Physics or on Amazon.com.  Prices range from $40-90.

https://www.youtube.com/watch?v=qhZwhOMkQw4
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.

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.

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.

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.

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.

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.

Good luck and may the weather gods smile on you on May 9!

The post How to Safely Watch Mercury Transit the Sun on May 9 appeared first on Universe Today.

Huge Sunspot Turns Earthward

Massive sunspot AR 2529 at sunset. Image credit and copyright: Gadi Eidelheit.

Our seemly placid host star is just full of surprises.

Just one week ago, it looked like we were set to enter the first spotless stretch of 2016, as the Earthward face of Sol presented one lonely sunspot group going ’round the limb, headed towards the solar far side.

Ah, but a few days can make all the difference when it comes to solar astronomy. Late Sunday night we were flooded with new solar images taken by observers worldwide, showing the emergence of sunspot active region AR 2529. This monster spot is easily already number one with a bullet for 2016.

And as Gadi Eidelheit based in Israel notes, you can already see AR 2529 without magnification, using solar filter glasses:

How big will AR 2529 get? One thing is for certain: it’ll be turned directly Earthward in just a few days. AR 2529 currently harbors the potential for C-class flares, and could send some love our way in the form of solar flares, and just maybe a coronal mass ejection or two. This also means we could be in for a fine aurora display later this weekend for folks living in high latitudes.

This development certainly goes against the prevailing trend. One swallow certainly does not make a spring, and AR 2529 appeared just as we were sliding back towards another solar activity minimum for sunspot cycle 24. The last solar minimum back in 2009 was the deepest in over a century, and some heliophysicists speculate that Cycle #25 may be absent all together. Another idea in the solar astronomy community is that perhaps the classic use of sunspot numbers does not completely describe current solar activity, and perhaps the orientation of what’s known as the solar heliospheric current sheet paints a more accurate picture.

Can you see it? We urge all owners of solar scopes and eclipse glasses to get out and try to spot AR 2529 this week. Welder’s glass #14 works great as well. Do not, of course, stare at the Sun unprotected, or attempt the long list of unsafe methods we’ve heard of over the years, to include smoked glass, sunglasses, exposed film negatives, screw-on eyepiece filters, etc. All of these are dangerous.

You can also safely project the image of the Sun onto a piece of paper using binoculars and see large sunspots… or you can watch the daily growth and progression of AR 2529 via NASA’s Spaceweather website or the joint NASA/ESA Solar Heliospheric Observatory (SOHO) mission.

The Sun rotates once every 25 days at the equator, and slower at the poles. Remember, the Sun is a big whirling ball of gas. The sunpot cycle peaks once every 11 years. AR 2529 shows the hallmarks of a late cycle spot, as it’s located very near the solar equator. One sign that a new solar cycle is underway is the appearance of high latitude sunspots, which then progress towards the equator as the cycle matures. Such a progression in latitude was first noted by Richard Carrington in 1861 and refined by Gustav Spörer, and the charting of such a cycle—known as a Spörer diagram—now bears his name.

Is AR 2529 the ‘last hurrah’ of Solar Cycle #24? Will the Sun present a spotless or active face for the transit of Mercury on May 9th? Though Cycle #24 was a lackluster one, it did have some memorable moments, such as the massive sunspot that graced the solar disk during the partial solar eclipse of October 2014.

Of course, it’s a lingering mystery as to just why the solar cycle is exactly 11 years long, and whether longer cycles persist. As we study similar activity periods on other stars, we’ll most likely gain an insight to characterize just what powers our own. No other astronomical object is more important to humanity as a species, as the Sun energizes and powers the drama of life on Earth. Outbursts such as the massive 1859 Carrington superflare could spell an extremely bad day for our modern day technologically dependent civilization. It’s imperative to know just what our Sun is doing, now more than ever. To this end, a fleet of Earth and space-based systems keep tabs on Sol 24-7, to include SOHO, SDO, Hinode, Proba-2, and the STEREO A and B spacecraft, just to name a few.

In all likelihood, though, AR 2529 will most likely just put on a good show. Solar astronomy, unlike following other objects, is a place where things are happening, sometimes, within the short span of an hour or so.

Stay tuned for updates!

Send those sunspot images in to Universe Today’s Flickr forum… we just might feature ’em in an upcoming post!

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Did the Sun Steal Planet Nine?

Artist's impression of Planet Nine. Credit: ESO/Tomruen/nagualdesign

One of the biggest new mysteries in our Solar System is the purported presence of a large and distant “Planet Nine,” traveling around the Sun in a twenty-thousand-year orbit far beyond Pluto. Although this far-flung world’s existence has yet to actually be confirmed (or even detected) some scientists are suggesting it might have originally been an exoplanet around a neighboring star, pilfered by our Sun during its impudent adolescence.

In January 2016 the remorseless “planet killer” Mike Brown — a Caltech professor and astronomer whose discovery of Eris in 2005 prompted the IAU’s reclassification of planets, thereby knocking Pluto from the official list — announced evidence for the existence of a “real” ninth planet orbiting the Sun four times farther than Pluto…and possibly even farther out than the Kuiper Belt is thought to extend. According to Brown and co-researcher Konstantin Batygin their Planet Nine may be almost as massive as Neptune, but they’re still on the hunt for it within the regions where they think it should be.

Formed five billion years ago in a cluster of other stars, our Sun once had hundreds if not thousands of stellar siblings (now long since dispersed through the nearby galaxy.) As the stars developed many likely had planets form around them, just as the Sun did, and with all the young star systems in such relatively close proximity it’s possible that some planets wound up ejected from their host star to be picked up — or possibly even outright stolen — by another.

Brown and Batygin’s Planet Nine could be one of these hypothesized adopted worlds. A team of researchers, led by Alexander Mustill at the Lund Observatory in Sweden, recently investigated the probability of this scenario, described in an April 4, 2016 article on New Scientist.

What the researchers found based on their models — which took into consideration the orbits of known KBOs and trans-Neptunian objects (TNOs) but not the effects of known planets — was that the Sun could very easily capture nearby exoplanets as well as clusters of smaller bodies (like “mini Oort clouds”) given that the objects are far enough from their host star and the relative velocities during the “pick-up” are low.

While the researchers admit that the chances of a heist scenario having actually taken place are quite small — anywhere from 0.1 to 2% — they’re not zero, and so should be considered a reasonable possibility.

“While the existence of Planet 9 remains unproven, we consider capture from one of the Sun’s young brethren a plausible route to explain such an object’s orbit.”
– A. Mustill et al., Is There An Exoplanet In The Solar System? (Source)

It’s previously been suggested that the Sun could have captured worlds from other stars in passing, such as comets and even the approximately 1,800-kilometer-wide KBO Sedna.

There’s also the possibility, note Mustill et al., that a world like Planet Nine could have ended up a member of our Solar System after being forcibly ejected from its own where it formed close to its star but within an orbit that wasn’t stable — especially considering the complexities of multi-body systems.

Of course Planet Nine, if it exists at all and if so, whatever it happens to get named, may also have formed from the same planetary disk as the other planets. But even if that’s the case there will be many questions that will then need to be answered.

Sources: New Scientist and arXiv.org

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