Carnival of Space #105 @ Space Disco(very)

Ian O'Neill takes the helm at the Discovery Space and hosts the 105th Carnival of Space.  This week there's lots going on from why people should go to Mercury, more Tunguska weirdness put in its place, a space elevator concept that leaves me spinning, and much more.

Carnival of Space #104 - The Arrow Edition

Welcome to ...
Carnival of Space #105 #104
... at Mang's Bat Page!

I'd like to thank Fraser for this my second time hosting the Carnival. While my first effort was a real blast, I do hope you all get a lift from this one.

This 105th 104th edition of the Carnival of Space is dedicated to Canada's CF-105 Avro Arrow the most advanced and ill-fated aircraft of its day.

Before we begin, I'd like to reflect on this amazing aircraft and its bittersweet legacy.

Arrow Reflections

In the 1950's Canada wanted a twin engine, all-weather, two seat, supersonic interceptor to defend against the Soviet bombers. The Arrow was our answer. Only it was never to be.

The Arrow was a source of national pride and shame for Canadians. An advanced fighter interceptor, widely believed to be superior to British and US projects. It incorporated many innovations including fly-by-wire, computer control, an integral missile system, and internal weapons pod. The Arrow was capable of exceeding Mach 2 with a 60,000 foot ceiling. It was even able to reach supersonic speeds without afterburners! A Mach 3, 80,000+ foot version was under study. The Iroquois engine being designed for the mark 2 Arrow was the most powerful turbojet in the world at the time. Ultimately the Arrow failed because of politics, changing roles, and a lack of buyers outside the country. For the US, Britain, and France - it was not invented there. Sadly, the five Arrows were reduced to scrap. There is even a conspiracy theory about a missing Arrow. The real tragedy was the damage to our aerospace industry and in true Canadian fashion the cancellation may have cost more than completing the program.

I grew up within sight of the production and test facilities. One of my mothers friends was a friend of Jan Zurakowski, the first test pilot, and I believe also one of the chase pilots. And when I was a child, I built models of the plane. Little did I realise that families living just down the street had been hurt by the 30,000+ layoffs and job losses resulting from the cancellation.

Others gained from Canada's loss. A group of 32 engineers went to NASA and worked on manned space programs. Others worked on the Concorde. The legacy of this project is an amazing tale.

And now the 105th 104th Carnival of Space ...

Startup, Blueprints, Models and Test Flights

• Alan over at MSN's Cosmiclog shows how Young star trekkers shine. But it's not quite what you might expect.


• Ethan at Starts with a Bang! contributes "The Lazy Astronomer" on how you can start exploring the night sky with no knowledge and good pair of binoculars for less than $100.


• Rob at the Orbiting Frog wants to know how people got into astronomy by sharing how he got into astronomy.


• David at Robot Explorers recalls Project Hyreus a clever and impressive student designed Mars Sample Return mission.


• Lousie at "A Babe in the Universe" get a looks at NASA's full-scale “Moonbase” mock up under construction with the cylindrical and toroidal modules and docked lunar rover.

Look off the Port Wing. Higher. Higher!

• The Bad Astronomer presents this unusual and awesome view of Saturn! There's a lot going on in the shadows and it takes someone with Phil's knowledge to explain it.


• The Lab Lemming catches on of those rare moments when both Scorpio and Orion are visible at the same time. Keep running oh boastful hunter ....


• Astroblogger presents this photo of the anomalously bright Comet C/2008 Q3 Garrad near a Globular Cluster.


• Nancy at Universe Today reports on The Brotherhood of Hubble Warriors: Jeff Hoffman Reflects on HST Repair Missions .


• Nicole at One Astronomer's Noise reflects on the STS-125 Hubble Repair and the different challenges facing terrestrial and space telescope repair.


• Bente at Planetbye has a little fun with a female perspective on the awesome Hubble fix.


• Steinn at the Dynamics of Cats shows a video of the STS-125 Hubble Wrap-up STS-125 Hubble Wrap-up.


• The Cosmiclog looks at why space repairs aren't easy.


• Mang (oh that's me) presents a third article using the JPL orbit simulator, this time looking at Strange Orbits: Quasi-satellites, Horseshoes, Corkscrews and Earth Stalkers - Earths Other Moons II. As an added bonus, meet Asteroid David Dunlap inspired by the fight to save Canada's largest telescope and observatory.

In-Flight Entertainment

• Jazz Singer, Diane Nalini launched a new album "Kiss Me Like That" in Toronto on Sunday May 24th. The album features 13 songs bringing astronomical themes to Jazz. (h/t to Ray Khan)


• The Space Writer reviews the new Star Trek movie.


• Cosmiclog looks at the lighter side of spacewalking. And no, it is not boomdiada!

Landings

• Ian O'Neill has taken over the role of Producer at Discovery Space and the Space Disco blog replacing Dave Mosher.  Good luck Ian (and Dave).
  

Science and Engineering

• We continue to learn from mistakes and disasters, this time Space Disco shows How the Chernobyl disaster may help plants grow on Mars.


• OrbitalHub presents Glory In The Sky a look at a science mission that will look at Earth?s energy budget and hopefully allow us to anticipate changes to the climate


• Cheap Astronomy presents a podcast "One Crowded Second" the first of a two part series on the time line of the Big Bang and subsequent evolution of the cosmos.


• Do you find you have less energy and are less active as you get older? Do you wonder why you never see grannies brake dancing? It turns out stars aren't that much different, find out about the interesting science of gyro-chronology.


• Bruce at 21st Century Waves looks at a mega-engineering project from the late19th and early 20th century and what we may learn about the future of manned spaceflight in  "10 Lessons the Panama Canal Teaches Us About the Human Future in Space".

Imagine the Possibilities

• Centauri Dreams looks at "The Hunt for Centauri Planets" about an ambitious but tracking low-key hunt for planets around the nearest star(s). In less than five years we might discover an Earth sized planet orbiting one of our nearest neighbours.


• Cosmiclog looks at the past and future of private space flight from Mircorp to Space-X in "The Past and future of 'New Space'".


• Out of the Cradle offers up an EVA interview with Paul Eckert about the 6th Space Investment Summit


• Cosmiclog presents a Time Travelogue looking at that staple of fantasy and science fiction from Dickens to Star Trek and the Terminator. It turns out that some of these scenarios may be testable at a quantum level.


• CumbrianSky looks at some historical events and asks what might have been if things had gone slightly differently?

Belated

• Music of the Sphere's provides insight into the "Super-cool Spacecraft" Herschel and Planck.

Arrow Footnotes
We now conclude our regularly scheduled Carnival and leave you with some more Arrow references:

• The Canadian Air and Space Museum in Downsview (Toronto)
• The Canadian Aviation Museum in Ottawa
• Wikipedia on the Arrow
• Wikipedia on Avrow
  
• An arrow site at avro-arrow.org
  
• A Video on the Arrow at google
  
• The Arrow site and links at the University of Saskatchewan Archives
• The Iron Warrior (U of Waterloo) looks back on the Arrow
• The Arrow at Fighter-planes.com
• The Arrow at Global Aircraft.com (suggested by a reader)
  

If you are in Toronto check out the Canadian Air and Space Museum where you can see a full sized replica of the Arrow. Or in Ottawa, the Canada Aviation Museum has some of the remaining components of the Arrow.

You may want to read one of Peter Zuuring's books "The Arrow Scrapbook", "Arrow Rollout", or "Arrow Countdown".

There was also a 1997 made for TV movie called The Arrow starring Dan Ackroyd that was loosely based on the Arrow story.

So long until the next carnival!

Space Carnival Chain

Last Week (103) : @ The Chandra Blog

Next Week (105) : @ Space Disco

Home Base : Carnival of Space | Universe Today

<==== Don't forget to checkout the Unoffical Carnival of Space Search on the blog sidebar (near the top).

David Dunlap Asteroid

The main belt asteroid 70207 discovered in 1999 is now called 70207 Davidunlap.  It orbits once every 3.7 yeas near the inner edge of the main astreoid belt and is 5 kilometers in size. You can see the orbit diagarm here.

The astroid was one of 62 discovered by Mike Collins, an amateur astronomer who lives in California.  Mike is a supporter of the efforts to save the Dunlap Observatory and Park in Richmond Hill.  He named the asteroid to recognize the  "extraordinary effort demonstrated by the dedicated community of Richmond Hill for the past 20 months to save its greatest landmark".
h/t to Ray Khan

Strange Orbits: Quasi-satellites, Horseshoes, Corkscrews and Earth Stalkers - Earths Other Moons II

Source: Paul Wiegert's Quasi-satellite page at UWO. Click on image for more or see links below.

This time let's look at a number of very strange objects known as quasi-satellites and co-orbital bodies using the JPL orbit simulator.

Basically co-orbital bodies are objects that share an orbit but are too far apart for one to be a natural satellite or true moon. Even very large planets can't completely clear all of the debris out of their orbits. In fact, they create special opportunities for co-orbital bodies at what are known as the five Lagrange Points and through resonant orbits.


True Moons

Before we talk of false moons, we need to be sure of true moons. Natural satellites or true moons orbit inside a volume of space known as a Hill Sphere. This is where the gravity of a planet or other object dominates the gravity of a second more massive object like the Sun. It might help a bit to think of water running down a drain in a basin with two drains - the whirlpool is a little bit like a Hill sphere. (I'm sure there are problems with this analogy but it might make an interesting school science experiment.)

There are two points on the surface of a Hill Sphere where the gravity of the two main objects is in balance. These points are known as L1 and L2 and for the Earth-Sun system the sphere is about 1.5 million km (or 0.01 AU) in radius. While there are a number of types of orbits that will keep an object at L1 and L2, these aren't stable places and asteroids wouldn't remain there for long. However, it does turn out that L1 and L2 are very useful places to put satellites.

In practice a moon will be found well within the Hill Sphere of a planet.

Trojans (and Greeks)

The first and simplest type of false moon are called Trojans. These objects orbit at or near the L4 and L5 Lagrange Points which are placed equally forward and behind a planet on it's orbit forming an equilateral triangle with the two major objects (such as Earth-Sun or Jupiter-Sun).

The first Trojan asteroid was discovered in 1906 and named Achilles ( orbit diagram, Wikipedia ). Achilles, which leads Jupiter, and its fellows at L4 became known as the Greeks camp or the Greeks. And the Jupiter trailing asteroids at L5 became known as the Trojan Camp. There are even a couple of "spies" that were named before the convention was agreed upon.

Whenever you have one body in orbit around another you will have these points. It can be relative to a star and planet like the Sun and Jupiter, or even a planet and its moons. Saturn's moons Tethys and Dione each have Trojan moons. In theory, there could even be Trojan planets that could arise in situations like binary star systems.

Other than Jupiter, both Mars and Neptune have know Trojans. Earth has no know Trojans. Wikipedia has a list of objects at Lagrange Points.

And if you're wondering why I haven't mentioned the L3 Lagrange Point.  That point lies on the opposite side of the larger object. Anything near there would be unstable.   Beyond some science fiction like Journey to the Far Side of the Sun, there's nothing there.

Weird orbits - Truth is stranger than fiction

Finally, there are a variety of objects with very strange orbits. Some of these are called Quasi-Satellites with orbits that have been described as Horseshoe or Tadpole and Corkscrew shaped. Stranger still, some of these switch back and forth. Below are some of these:

• 3753 Cruithne ( orbit Diagram, Wikipedia), sometimes described as Earth's second moon, follows one of these orbits. There is an interesting simulation over at the orbit and gravity simulator here that shows the long term effect much better.
• 2009 BD ( orbit Diagram, Strange Asteroid 2009 BD Stalks the Earth | Universe Today) a recently discovered Earth Stalker. Try centering on the Earth and zooming in all the way, hit play and watch the race. Remember, Earth's Hill Sphere has a radius of about 0.01 AU - you can see that BD doesn't get that close.
• 2003 YN107 ( orbit Diagram, Wikipedia) a small corkscrew meteoroid that switches between corkscrew and horseshoe orbits.
  
• (164207) 2004 GU9 ( orbit Diagram, Wikipedia) a large 200+m corkscrew asteroid with a very stable long term orbit.
• 2002 VE68 ( orbit Diagram, Wikipedia) A long term companion for Venus.
  

While the effect isn't as obvious or dramatic as the movies and animations on the UWO page, try switching from Sun to Earth centered views and using the sliders to adjust your point of view.  It may help to remove most of the orbit lines with "No Orbits" and just add back the Earth's and maybe the objects.  Don't forget to zoom in for a better look.

Suspected space junk with weird orbits

These aren't in the orbits database but may be of interest:

• An Apollo 3rd stage booster
  
• They're not quite sure ...
  

Related Articles - Elsewhere

• Quasi-Satellite information page - Uneversity of Western Ontario, Paul Wiegert - good info, animations, and movies of various co-orbitals
  
• Cork-screw asteroids - NASA
  
• The moon that went up a hill and came down a planet | Bad Astronomy - why the moon isn't a planet but could be if ...
• Pluto's big hill to climb | Bad Astronomy - a discussion of why orbital dynamic characteristics like clearing the neighbourhood and Hill spheres probably shouldn't be used to classify planets

Related Articles - This Site

• Part I - Orbits: Intro to NASA's Orbit Simulator - solar system small body tour
• Part II - Orbits: Comet/Asteroid/Meteor Close Encounters, Near Misses and Impacts
• The Last Planet?
• Earth's other moons ...

Carnival of Space #102 @ The Spacewriter's Ramblings

The 102nd edition of the carnival is now up here.  Enjoy the cotton candy and the rides!

David Dunlap Observatory slated to reopen in the IYA2009!

The observatory that confirmed the first black hole will reopen this summer for public outreach programs!

Congratulations to the folks at the Royal Astronomical Society of Canada!

For more read the RASC news item.

No word on any potential research.

Related Articles

• April - Last chance to see DDO Canada's largest telescope  
• David Dunlap Observatory Tour and Photos 
• Black Hole discoverer to be eaten by land developers

Space badge resource for Girls and Boys

Ken Murphy over at Out of the Cradle wrote a piece on Girl Scout space badges in Scouting the Moon.  The article also has some references to US Boy Scout Space Exploration merit badge and the interesting online resource meritbadge.org.

(See what you can find when you read Carnival of Space, h/t to Issue #101)

Carnival of Space #101 @ Robot Explorers!

Hey folks!  The Carnival has set up again, this time you can find it at David Portree's Robot Explorers!

David's blog has lots of interesting material on space exploration both proposed and actualized.

BTW. The host really liked my article on asteroid and comet near misses and impacts.  Thanks David.

Orbits: Comet/Asteroid/Meteor Close Encounters, Near Misses and Impacts

People are fascinated by the prospect of near misses and impacts by asteroids, comets, and meteors. A few decades ago there was almost no awareness of the potential risks. As automated search telescopes like LINEAR and the Catalina Sky Survey are being used to study the risk, the public is becoming more aware of the numbers of near misses and the potential danger. There is also a great deal of work being done on how to change the course of potential impactors.

This article will use the NASA JPL orbit simulator to illustrate some of these. If you don't know about the simulator, please read Orbits: Intro to NASA's Orbit Simulator - solar system small body tour.

Before we start, I should put the risk into perspective. For anyone who isn't aware of it the automated searches are happening because the US government realized the long term risk of an impact with something large from space was something they could and should investigate. To date, these studies have identified over a thousand objects to keep our eyes on in their search for potentially hazardous objects. Most of these are too small to cause critical or even major damage. Many of the orbits of others are known well enough to rule them out. The search and monitoring continues, but as of right now, despite some close calls being predicted there are exactly ZERO of these to really worry about.

The Earth is constantly encountering things in space. Meteor showers are caused by dust and small particles left over from comets. Occasionally we get some spectacular fireballs from some larger rocks. Really damaging objects, say larger than a good sized house, are much rarer. And lastly, more of these miss us than hit us. Of all of the objects whizzing by Earth, the most potentially damaging are probably comets. The tend to be bigger and many of them are only being seen for the first time. Fortunately, if you look at the history of comet close calls they have been much farther away than anything else.

Now, a tour of celestial close encounters using the JPL Orbit Simulator

For each of these I recommend adjusting the controls to center on one of the near colliding objects and using the date control to set a date a few days or weeks before the impact or near miss and hit play or step through it. You may notice that some of the simulations aren't perfect, they won't take in all the effects of gravity as objects get very close to planets but they'll give you an idea.

I am taking some liberty in referring to these objects as rocks. Asteroids are now thought to be more like large rock piles rather than single pieces of rock.

1993 F2 ( Comet Shoemaker-Levy 9 ) - ( orbit diagrams, NASA, Wikipedia)

In 1992 this comet passed too close to Jupiter and was torn into fragments setting up a cosmic 21 gun salute and the most spectacular impacts ever seen. Between July 16 and July 22, 1994 twenty one (21) fragments ranging in size up to 2km slammed into Jupiter at over 60 km/s. Under the scrutiny of the Hubble and every spare telescope available the results were spectacular. A couple of the fragments left scars the size of the Earth on Jupiter.

One thing to understand about impacts, the damage done is a factor of kinetic energy and the speed of the object contributes far more to the damage than the size. The same impact at half the speed would only produce 1/4 of the damage.

You'll notice the orbit simulation doesn't quite show a collision or even the orbits intersecting at the right dates. Sorry no kaboom in the simulator.

2007 WD5 - ( orbital diagram, Wikipedia )

While not large enough to cause a Mars shattering kaboom, Marvin the Martian breathed a sigh of relief on January 30, 2008 when this small (50m) rock whizzed by his planet at 12 km/s. Many of Earth's telescopes including the Hubble were watching just in case they might catch the largest ever observed impact on a rocky body. The asteroid's orbit was altered by its close encounter and it is now considered lost.

Note: Smaller impacts have been seen on the Moon and even filmed - see here.

2008 TC3 - ( orbital diagram, Wikipedia )

On October 6, 2008 the automated telescopes of the Catalina Sky Survey detected an object that would hit Earth in less than 24 hours somewhere over north Africa. The meteor (5 m) entered from west to east at a speed of 13km/s and exploded high over the desert near the border of Sudan and Egypt. The explosion was seen by airline pilots, satellites, and people on the ground. Remarkably fragments of the meteor were recovered by researchers after a search of the desert.

This was the first ever predicted meteor strike.

2007 TU24 - ( orbital diagram, Wikipedia )

On January 29, 2008 this rock (250 m) missed Earth by about 1/2 million kilometers or about half again as far away as the orbit of the moon. However, this didn't stop the lunatic fringe from making all sorts of bizarre claims that scientists didn't understand the real threat and it would do all kinds of damage. They even tried to say that some minor events were caused by it. All hogwash.

Comet Halley (1P Halley) - ( orbit diagram, Wikipedia )

The most famous comet returns every 75-76 years has been observed going back to ancient times. It wasn't until Edmond Halley calculated the orbit did people realise it was a repeat visitor. The comet is about 11km in size and irregular (peanut shaped) and follows a retrograde (backwards) orbit attaining speeds of 70 km/s. Dust from the comet is responsible for two meteor showers in October and May.

Comet Holmes (17P Holmes) - ( orbit diagram, Wikipedia, Comet Holmes visits the 433rd! )

Comet Holmes is a very short period of about 7 years and is notable because it periodically has major outburts of gas. On most normal orbits the comet would pass almost unnoticed. But it holds the record for the most major gas outburst of any comet. In 2007 gas and dust cloud around the comet swelled to over 1 million km making it briefly larger than the Sun. The nucleus of this comet is about 3-4km in size.

2004 NM4 (99942 Apophis) - ( orbital diagram, Wikipedia )

This asteroid (270m) discovered in 2004 caused some concern after early calculations showed it might collide with the Earth in 2029 or 2036. It will pass between Earth and our geosynchronous satellites on Friday, April 13, 2009 when it should be as bright enough to be seen even within cities as it moves very quickly across the sky. The asteroid is being studied for risk of future impacts including a possible hit in the Pacific Ocean in 2036 (more study and analysis has shown this to be unlikely).

29075 (1950 DA) - ( orbital diagram, NASA's NEO pages, Wikipedia )

This asteroid (1.1km) is being studied because it is an impact concern for the year 2880. There are many variables that affect the orbit of an asteroid in subtle ways and these are all being studied to get a better understanding of the risk from this and other asteroids. Unfortunately JPL's time machine won't let you go that far into the future.

2004 XP14 - ( orbit diagram, Wikipedia )

On July 3, 2006 this asteroid (300-900m) passed Earth just beyond the orbit of the Moon. This is the closest recorded pass of an asteroid other than the 50m sized 2009 DD4.

4179 Toutatis (1989 AC) - ( orbit diagram, Wikipedia )

A large (2-4km) irregular asteroid that can come within a 1/2 million to a million km of the Earth and Moon about every four years. This may be the largest close approaching asteroid we know of.

Lexell's Comet - ( orbit diagram, Wikipedia )

Set the wayback machine to July 1, 1770 to see the closest recorded pass of a comet to Earth! Lexell passed us with a slender gap of just over 2 million km. The comet is now lost and it's believed that an interaction with Jupiter has altered its orbit.

Update: 2009 HC82 - ( orbit diagram, Universe Today )

Just in, on April 29th the Catalina Sky Survey bagged another very strange one.  The object which is 2-3 km in size and has a steep 3.39 year retrograde (backwards) orbit suggesting it may be a burnt-out comet.  It also comes within 3.5 million km of Earth's orbit.  The team at the sky survey are surprised that this wasn't discovered sooner as it should have been observable nine years ago.  Try setting the simulator date to early 2001 and the speed to about 3 days per frame or less, hit the play ">>" button and tinker with the controls.  For more see the Universe Today article.

A few more close objects

• Comet 55P Tempel-Tuttle - (3.5 km) and the source of the Leonids with a 33yr orbit - ( orbit diagram, Wikipedia )
• Comet Catalina 3 (2005 JQ5) - once considered an impact risk for 2085 it is 1.4km in size on a 4.5yr orbit - ( orbit diagram, New Scientist )
• 109P Swift Tuttle - a 133 year orbit and the source of the Perseids. Also a possible future Earth/Moon impactor beyond 3000CE - ( orbit diagram, Wikipedia )
• 2004 FU162 - A 6m rock that passed us on March 31, 2004 at a distance of 7,000km - ( orbit diagram, Wikipedia)
• 2004 FH - A 30m rock passing at 43,000km on March 18, 2004 - ( orbit diagram, Wikipedia ).
• 2003 SQ222 - A 5m rock passing 88,000km on Sept 17, 2006 27, 2003 and detected 11 hours after closest approach. - ( orbit diagram, Universe Today )
• 2009 DD45 - A 50m rock passing us within 63,000km on March 2, 2009 - ( orbit diagram, Wikipedia )

More Information on Near Earth Objects, Potentially Hazardous Asteroids and Minor Planets

• The JPL orbit simulator Near Earth Object lookup page
• The Harvard Centre for Astrophysics list of close asteroid approaches to Earth
• The Harvard Centre for Astrophysics list of close comet approaches to Earth
• The JPL list of recent and upcoming Neart Earth Object (NEO) close approaches to Earth
• The Harvard Centre for Astrophysics Potentially Hazardous Asteroid Close Approach List
• Andrew Lowes' list of upcoming close passes of objects with the inner planets. Passes closer than 3 million km (0.02 AU) are highlighted in red.
• The Lowell Minimum Orbital Intersect Distances (MOIDs) page. Small MOIDs indicate potential close encounters and opportunities for planets may change the orbits of small bodies.
• There are lists of planet crossing objects (they still call them minor planets) at Wikipedia:


• List of Venus-crossing minor planets
• List of Earth-crossing minor planets
• List of Mars-crossing minor planets
• List of Jupiter-crossing minor planets
• List of Saturn-crossing minor planets
• List of Uranus-crossing minor planets
• List of Neptune-crossing minor planets
  


• A list of notable asteroids and close approaches at Wikipedia
  

Some recent fireballs (we don't have orbits for) bolides is the proper name:

• October 15, 2008 Southern Ontario fireball
  
• February 15, 2009 Texas fireball
• March 15, 2009 Southern Ontario fireball
  
• November 20, 2008, Alberta Fireball
• Evidence of recent Martian bolide impact
  

Update: Some very interesting tibits from the Planetary Defense Conference on the sizes and numbers of discoveries of NEOs can be found here at Planetary Sociecty Blog. And a second article talking about what could be done if we knew we were going to be hit.

Related Articles

• Orbits: Intro to NASA's Orbit Simulator - solar system small body tour
• Tunguska's Legacy
  
• The Last Planet?
• Earth's other moons ...
• Comet Holmes visits the 433rd!

See the Sun through an Hydrogen-Alpha filter (May 2 11am-4pm)

The folks at Khan Scope Centre on 3243 Dufferin Street south of Yorkdale are demonstrating a Lunt Hydrogen Alpha solar telescope between 11am and 4pm (if the clouds stay away).  If you've seen the Sun through a normal solar filter you'll be surprised at the details these filters reveal.  

Who knows perhaps there'll be a sunspot too?

BTW They're having a tent sale on Saturday May 30th.