Starlight from baby stars within the nebula blow outward in jets, sculpting nebulae into beautiful and exotic shapes in a way very similar to the way rain and wind sculpt the rocks of Arches National Park, Goblin Valley or Monument Valley.

Here’s the link. Here’s NASA’s link.

After the images load they’ll automatically start showing the animations.  Each frame of the movie represents a Hubble image taken at one year intervals of regions in our galaxy where stars are being born.

Notice that in each movie window a scale size marker is displayed – showing a scale distance of 1,000 Astronomical Units.  1 A.U. = the distance from the Sun to the Earth, which is 93 million miles (150 million km.)

That means that at this scale the distance from the Sun to our Earth is smaller (a lot smaller) than one pixel on these images.  Or you could think of it like this – that line representing 1,000 A.U. represents a distance that a beam of light would require about six days to cover.

Hubble images have also been used this way to make a movie revealing the rapidly spinning pulsar at the center of the Crab Nebula (click here).

The Hubble Space Telescope as a movie camera – who saw that coming?

It began in 2009 when NASA centers in Maryland and California hosted events to celebrate the successful arrival of NASA’s Lunar Reconnaissance Orbiter spacecraft into lunar orbit. These events provided opportunities for the public to observe the Moon.  The overwhelming public response inspired them to do the event again on a much larger scale. Other astronomy organizations have joined in making it an international effort.

So, join in and observe the Moon on September 18th! Look for it in the southeast at sunset. Use binoculars or a telescope if you have them. Try to identify several of the roundish darker regions. These are large impact basins that have been filled by dark lava. When observing through a telescope, the best place to look is near the day-night line, called the terminator. Here, long shadows allow surface details like mountains and craters to stand out.

Don’t have a telescope? The Salt Lake Astronomical Society will host a free public star party (weather permitting) at the Stansbury Park Observation Complex (SPOC) on Saturday September 18. (They will also hold a “sneak preview”, the night before at the Taylorsville Harmons, 5454 S Redwood Road). Both observing sessions run from dusk to 11:00 p.m. Directions to SPOC

The Sun has periodic explosions of material on its surface which we call Solar Flares.  These flares can sometimes lift highly charged material off the surface of the Sun and into space, and event called a Coronal Mass Ejection (CME).  CMEs generally take about 3 days to travel the distance between the Sun and Earth’s orbit.  If this happens to occur while pointed towards the Earth, it can cause several different effects, one of which is the Aurora Borealis (and Aurora Australis in the southern hemisphere).  Auroras occur because the charged particles in the CME interact with our Earth’s magnetic field and our atmosphere.  Particles in the atmosphere can begin to emit light, or glow, due to this interaction. 

There is no danger to observers on the ground, though some other effects of arriving CMEs can be harmful if precautions are not taken.  NOAA (National Oceanic and Atmospheric Administration), and more specifically the Space Environment Center, is primarily responsible for monitoring the space environment and issues alerts.  These alerts allow satellite and utilities companies to take precautions with their hardware.  Airplane flights over the polar regions of the Earth will also divert to protect passengers.  And Space Shuttle and Space Station astronauts take cover in special areas of their spacecraft in order to be sheltered from the CME’s effects.  A lot of study and monitoring goes into making sure that we are kept safe from these frequent “burbs” from the Sun.

Misconception #1

    The Seasons are caused by the changing distance between Earth and the Sun.

Misconception #2

    There are two days in the year when the sun is directly over the north or south poles of the Earth.

Misconception #3

    The Earth’s axis changes the direction of its orientation throughout the year.  

Granted, it is difficult to grasp the reasons for the cyclic changes of our seasons from our singular perspective on the Earth’s surface and these common misconceptions are supported by some reasonable evidence.  Take for example the first misconception; the seasons are caused by the changing distance between the Earth and the Sun. For example, you may have noticed experiencing more heat energy from a source, like a campfire, as you get closer to the source and notice it less as you back further away.  This is an occurrence which seems to support this popular misconception.  The reality is that Earth gets only a little closer to or farther from the Sun during its orbit. When near a campfire, it’s easy to get twice as close without much movement at all. It’s largely an issue of scale and distance.

Earth orbits the Sun at an average distance of about 93,000,000 miles. One full orbit takes about 365 ¼ days. Earth is only – about 1.6% closer or 1.6% farther at its extremes throughout the year. That’s not much of a change.   The reality is that this change makes very little difference in our temperatures. There is even a paradox. Earth is closest to the Sun on or about January 4^th. Six months later when we are farthest from the sun, the date is near the 4^th of July. Anyone who lives in Utah, or anywhere in the northern hemisphere, should recognize the paradox. The northern hemisphere is actually warmer when the Earth is farther from the Sun. This paradox shows us that the changing distance has little effect on Earth’s seasons.

As we will discover later, the seasons are caused by Earth’s tilt causing more ‘direct’ rays of the sun to strike the surface of the earth for a longer time in the summer and ‘indirect’ rays to strike the surface for less time in the winter.

In conclusion, we have dispelled the first myth about the seasons.  We know that the seasons are not influenced by the slightly changing distance between Earth and Sun.  Stay tuned to Clark Planetarium’s blog for part 2 of our seasons discussion were we will examine the second common misconception.

For those of us that live north of the Tropic of Cancer, the Sun appears highest in the sky every day when it is due south. Its height on a particular day is determined by Earth’s orientation to the Sun. To quote from that previous post:

“Earth’s rotational axis is tilted by about 23.4º and points in a nearly constant direction as Earth circles the Sun. This is evidenced by the northern axis pointing toward Polaris, the North Star. While the axis continues to point in the same direction, it’s orientation to the Sun changes. Back on December 21, Earth was at the place in its orbit where the northern axis leans most away from the Sun.” This is illustrated in the diagram below.

The Sun has a diameter 109 times that of Earth. To correctly show how light from the sun strikes Earth at 40 degrees N latitude, the circle representing the Sun in the diagram has been placed too high with respect to Earth’s center.

In the diagram, light from the Sun is shown striking Earth at 40 degrees N latitude (Salt Lake City, Utah). An observer standing upright at 40 degrees N latitude would be on the line perpendicular to the horizon line. The angle between the horizon line and the line from the Sun is the angle that the Sun’s rays strike the surface of Earth. It is the angle that an observer in Salt Lake City would measure when the Sun is due south. On December 21, the angle between the horizon and the Sun is about 26 degrees, so we see the sun low in the sky at noon. (To see this better, turn the diagram so the horizon line is horizontal).

Back to the March post: “As Earth continues to move around the Sun, the angle between the axis and the Sun decreases.   . . .  until June 21, when Earth reaches the place in its orbit where the northern axis leans most toward the Sun.”

On this date we see the Sun high in the sky, but NOT directly overhead. For Salt Lake City, the Sun is about 73 degrees above the horizon. This is actually the highest we ever see the Sun.

Supernova 1987A appears as a very bright star near the center of this image. The photograph was taken by Marcelo Bass at the National Optical Astronomy Observatories’ Cerro-Tololo Inter-American Observatory, on March 2nd 1987. Image Credit: Marcelo Bass, CTIO/NOAO/AURA/NSF

The first visible sign of the supernova was captured on a photograph taken at a telescope in Australia about 3 hours after the neutrino burst. Since the neutrinos arrived two to three hours earlier than the light, does that mean that neutrinos travel faster than light? No, it means the neutrinos got a head start.

The processes inside stars and the events that lead to a supernova are detailed and complex. While the following description omits many important and interesting details, it has enough information to explain the neutrino head start.

A supernova is the explosive end of a massive star (the Sun is not big enough to explode as a supernova). Normal stars produce energy by fusing lighter elements into heavier ones deep in their cores. Energy is produced in the fusion process. The energy moves outward and eventually reaches the surface of the star, causing it to shine. This energy production also results in an outward pressure that balances the inward force of gravity. A supernova occurs when a star runs out of fuel in its core and the fusion reactions suddenly shut down. With the loss of outward pressure, gravity takes over and the core of the star collapses in a fraction of a second. The core of a massive star has enough gravity to squeeze the matter in it so tightly that protons and electrons combine to form neutrons. This transformation also produces an enormous number of neutrinos. The neutrinos are able to pass through the star’s outer layers and escape into space before the star shows any outward sign of trouble.

Meanwhile, deep within the star, the core collapse triggers a shock wave that moves rapidly outward. The shock wave takes several hours to reach the surface. When it does, the radiation released in the explosion can briefly outshine a galaxy. Astronomers predicted that neutrinos from a supernova would arrive before its light. So, the early arrival of neutrinos from supernova 1987A was evidence that astronomers have a correct understanding of what causes a massive star to go supernova.

The most obvious would be the lack of a sky glow produced by a myriad of outdoor lights. This glow washes out the richness and beauty of the starry sky, except for those few that live far away from light polluted cities.  

The second difference is more subtle. While most of the stars and constellations would appear the same, a few stars would be out of place. One of the most noticeable is Arcturus, fourth brightest star in the night sky. Arcturus, a red giant, is a prominent star on clear spring evenings. It can be found by following the curve made by the handle of the Big Dipper. As you observe it, can you detect a hint of red or orange color?

What makes Arcturus different? It is a galactic invader, a star that was once part of a small galaxy that was ripped apart and absorbed by our Milky Way Galaxy in the distant past.

Our Sun is in motion around the center of our galaxy. Most of the stars around us are in similar orbits, so we all move more or less together, like a large flock of migrating birds. Because of this, stars appear motionless over time spans as short as several thousand years. In contrast, Arcturus has a very different orbit. It is currently plunging down through the galactic plane, moving sideways to the local stellar “traffic stream,” That is why this bright star shifts its position noticeably with time. It takes Arcturus slightly less than 1600 years to move one degree in the sky, twice the apparent width of the full moon.

So, as the weather begins to warm, look off to the east and greet this galactic visitor.

For this model we will need a meter stick and something to mark the positions of each planet’s orbit, like a pen, small pieces of masking tape, or pins. The Sun is at the beginning of the meter stick. On this scale it would be the size of the point of a pin.

Mark each planet’s orbit at the distance given below.

Distance (inches)

Mercury ³/₈
Venus ³/₄
Earth 1
Mars 1 ^l/₂
Jupiter 5 ³/₁₆
Saturn 9 ⁹/₁₆
Uranus 19 ¹/₄
Neptune 30 ¹/₈
Pluto 39 ^l/₃ - at the far end of the meter stick.

In this scale model, New Horizons is now about 14 inches from the Sun. As can be seen, it is still a long way from Pluto. How far away are the nearest stars on this scale?

For distances beyond the solar system, a light-year is one of the units of distance that are used. Although it is sometimes confused with a unit of time, a light-year is the distance light travels in one year. Light (in a vacuum) travels 299,792.458 kilometers (186,282 miles) in one second. This is about 7 ½ times around Earth. A light-year is about 9,460,000,000,000 kilometers or 5,880,000,000,000 miles.

In our meter stick model, one light-year is one mile. Since the nearest star to the sun is 4.2 light-years away, in the meter stick model, it is over FOUR MILES AWAY! Pluto now seems very close.

Below is a list and a diagram of all of the stars within 10 light-years of the Sun. The distance to each star in light-years is distance to each star in miles in the meter stick model. With the exception of the stars in the Alpha Centauri and Sirius systems, those within 10 light-years of the Sun are red dwarf stars.

The Sun’s Neighborhood

This image shows the relative sizes of some of these stars.

Models can sometimes help our understanding of difficult concepts. With less than a dozen pinpoint sized stars in a 10 mile radius, our neighborhood is mostly empty space.

I keep a little dashboard widget from NASA on my Mac at home that keeps a running score on the number of extra-solar planets that have been discovered.  When I left for work this morning the exoplanet tally stood at 374.  As I write this post, that number has zoomed past 400.

Wow!

Think about that for a moment.  We now know of 50 extra-solar planets for every one planet in our solar system.  That 50:1 ratio is only going to get more lopsided as research continues.

I wrote this past summer about how astronomers hunt for exoplanets here.

Pay particular attention to the Kepler research spacecraft currently orbiting Earth.  This robotic telescope is right now simultaneously scanning about 100,000 stars in the vicinity of the constellation Cygnus on a hunt for earth-like planets.

Clark Planetarium will host a “Searching for other Earths” lecture this coming February by an astronomer working on the Kepler mission – keep an eye on the planetarium web site for details.

What we’ll do with scientific evidence of truly earth-like worlds in our galaxy is a fascinating topic to think about.

What would you do with certain knowledge of an earth-like planet a few hundred light years from us?  I can imagine lots of things – but shrugging my shoulders and saying “so what?” isn’t one of them.

When (not if) genuinely earth-like planets are discovered, that won’t mean UFOs are really alien spaceships.  The distances between us and any exoplanets are on the order of hundreds or thousands of light years.  In-person visits are out of the question – the distances involved are overwhelming.

If you could somehow make a spaceship travel ten thousand times faster than the fastest space vehicle ever launched, then a journey to one of the nearest of these recently discovered exoplanets would still require hundreds of years.

“Warp speed” is fine for sci-fi entertainment, but in the real world there are implacable laws of physics and mathematics that dictate why travel at the speed of light is impossible:

• To travel at the speed of light you become more massive than the entire universe,
• Your width shrinks to zero and you become two-dimensional,
• Time stops completely for you and the universe ages out of existence in an eyeblink, and oh-by-the-way,
• Your mathematics must be able to produce real-numbers answers for equations that involve dividing by zero.

You want to imagine going faster than light? (Scotty!  We need full power to the warp drive, NOW!)

Good luck with that.  Faster-than-light travel requires mathematics that produce real-number solutions to equations that involve taking the square-roots of negative numbers (go ahead and try that with your calculator).  Then there’s the whole cause-precedes-effect relationship being violated by superluminal speeds to deal with.  Good luck with that, too.

But don’t stop thinking about how to get to one of these soon-to-be-discovered earth-like exoplanets just because I’m throwing a few division-by-zero stumbling blocks in your path.  If you can actually, demonstrably and “for-reals” figure out a way to get to a habitable world orbiting Epsilon Eridani in less than ten years then fame and wealth beyond imagination are yours and I’ll be the first to applaud your success.

(But please  – don’t send me your ideas for a warp-drive.  I’m not in a position to evaluate such things.)

Nature loves spheres. It can’t get enough of them.

Soap bubbles are spherical because that shape most efficiently balances the outward pressure of the air within the bubble against the surface tension of the soap film.

When water splashes and for a brief instant a droplet of water is neither rising nor falling and is momentarily weightless, what shape does the droplet’s surface tension force the water to take?  A sphere.

Nature loves spheres. In the case of bubbles and droplets of liquid, surface tension creates a sphere to minimize surface area.

Stars are perfect examples of natural spheres.  The mass of a star is mind-bogglingly large and creates an equally mind-bogglingly large amount of gravity. What shape does Mother Nature give to so much mass to minimize its enormous volume?  A sphere.

Stars like our Sun are huge, dynamic, energy-producing concentrations of Hydrogen and Helium, compacted by their enormous gravity into spheres.

The reason planets appear spherical is because gravity compresses the planet into a shape that most evenly distributes the gravitational force among the planet’s mass.

Whether it is shaping water droplets, stars, soap bubbles or planets, nature seeks to minimize the surface area needed to contain a given volume, and the shape that keeps volume at the absolute minimum a sphere.

Any object in weightless space larger than a couple of hundred miles in diameter has enough mass for its gravity to overcome large-scale irregularities and force it into a spherical shape.  This gravitational compression also generates significant amounts of heat at the center of the planet. This heat melts, or at least softens, any solid materials within the planet, facilitating the planet’s collapse into a spherical shape.

Objects in space smaller than about 100 miles in diameter, such as most asteroids, comet nuclei and small moons, lack the mass to create a gravitational field strong enough to compress themselves into spheres.  These little worlds often take on what I call the “sick potato” look.

The 12.5 mile-long, 7.5 mile wide asteroid Gaspra, imaged in October 1991 from a distance of 1,600 miles by the Galileo spacecraft en route to Jupiter.

A really large asteroid, such as Ceres (diameter = 600 miles), has enough mass for its gravity to compress it into a sphere.

The 600 mile-wide asteroid Ceres as seen by the Hubble Space Telescope.

However, “perfect” spheres are hard to find in space.

Pretty much everything is space rotates, and rotating a non-rigid sphere causes it to “bulge” at its equator from the centrifugal forces acting on it.

This spinning distorts large planets into a slightly squashed shape known as an “oblate spheroid.” This means that a planet’s diameter measured through its poles is smaller than the diameter measured through its equator.

Whereas the difference between the polar diameter and the equatorial diameter of Earth is a barely noticeable 0.3%, the oblateness of Saturn, a large, gaseous and rapidly spinning planet,  is greater than 10%.  You can easily see Saturn’s polar flattening through a telescope.

Saturn's polar diameter is 33,700 miles, but its equatorial diameter is 37,360 miles.

There may not be such a thing as a “perfect” sphere in nature, but there is no doubt that spheres, nature’s favorite shape, are perfectly lovely.