The Sky Tonight Update: Rare Transit of Mercury Across the Sun

The planet Mercury will move directly between the Earth and the Sun. Viewers with telescopes and approved solar filters will be able to observe the dark disk of the planet Mercury moving across the face of the Sun. This is an extremely rare event that occurs only once every few years. The next transit of Mercury will not take place until 2039. This transit will be visible throughout all of South America and Central America, and parts of North America, Mexico, Europe, the Middle East, and Africa. The best place to view this event in its entirety will be the eastern United States, Central America, and South America.
(Transit Visibility Map and Information)

ISS Celebrates 15 Years in Space- See if you can locate it while looking for Comet ISON

The connected Zarya and Unity modules after Unity was released from the Space Shuttle Endeavor’s cargo bay.

Fifteen years ago on  Nov. 20, 1998, the Roscosmos (the former Russian Space Agency) launched a Proton rocket that sent the Zarya module into space.  This was the first section of the International Space Station.  Two weeks later on Dec. 4, the United States launched the Unity module making the 2 modules a real international space station.

The ISS is now the third brightest object in the sky after the sun and moon.  If you know where and when to look you can easily see it without a telescope, and NASA’s Mission Control at the Johnson Space Center in Houston can tell you when and where.  Log onto Nasa.gov to receive e-mail or text alerts a few hours before the ISS will be passing over your area.  If you sign up soon you might even be able to spot it while “comet hunting” during the Thanksgiving holiday.

Why is Comet ISON Green?…. and other updates

Great news, everyone! Astronomers world wide have confirmed that in the last day or so, ISON has increased in brightness to the point where it is visible to the naked eye. You still have to look closely, as it is still on the border of visibility. Astronomers expect the comet to brighten as it continues to approach the Sun, but no one can know for sure. Through telescopes the green color of the comet is visible.

So why is the comet green? It isn’t uncommon for comets to glow green. This is due to the presence of certain chemicals inside the comet that are released as the nucleus sublimates away into space. Most often these chemicals are cyanogen (CN) and diatomic carbon (C2). Both of these chemicals emit greenish-blue light when in a vacuum (like outer space) and exposed to large amounts of energy (which they are getting from the Sun).

Today I came across this awesome interactive website that allows you to track ISON (as well as other Solar System objects) through the sky from different points of view. I’ll be using  it to see where ISON will be over the next view weeks, it also gives you key dates and info. Click the picture below to visit the site:

Unfortunately for us here in Baton Rouge, the next few days have a lot of clouds in the forecast! There will still be time to view the comet early next week once the sky clears… Between now and November 28 the comet is approaching the Sun. From Earth it will be getting closer and closer to the horizon in the early morning sky. If you can, try and view it before Thanksgiving.  All you have to do is:

1. Wake up very early, around 5:00 AM!

2. Find a place with a clear view of the eastern horizon.

3. Find the constellation Virgo (outlined in the image above), it will be nearly due east.

4. Look for a faint fuzzy object

5. If you’re feeling up to it, bring the camera out and snap a picture. Click here for a past article about astrophotography tips, it is for a meteor shower, but similar rules apply.

6. While you’re out, don’t miss Saturn, Mercury, and Mars.

Astronomers are unsure of ISON’s fate after it’s close approach to the Sun (which will occur on Thanksgiving Day), it is possible that the Sun’s gravity will cause ISON’s nucleus to break apart. If ISON survives its close encounter with the Sun, it will be visible once again in the morning sky around December 6th. Cross your fingers for ISON’s safe passage around the Sun, and happy viewing!

Related articles

• Comet ISON, sun headed for close encounter on Thanksgiving (mnn.com)
• Potentially Dazzling Comet ISON Now Visible to Naked Eye After Outburst (space.com)
• Comet ISON Suddenly Brightens as it Dives Toward the Sun (universetoday.com)

Solar Eclipse Sunday Morning!

There will be a solar eclipse tomorrow morning (Nov 3). Unfortunately it is not visible from Baton Rouge. However, you can watch the web cast courtesy of SLOOH here
For info on viewing for our nationwide and worldwide readers please click here

Last but not least… Please practice safe viewing techniques when observing the Sun!

Happy Autumnal Equinox, balance an egg!

I decided to take a break this week from Full Dome Saga to observe the upcoming autumnal equinox, which occurs on Sunday, September 22. I was having a conversation the other day about the first day of fall, and the age-old subject of balancing an egg came up in the discussion.  Can you balance an egg on the equinox????

First, let’s take a look at the equinox itself. For a refresher on the reasons for the seasons, click here .

Last time I wrote a seasonal article, our Earth’s axis was tilting towards the Sun on the summer solstice. Now, the Earth has traveled along another quarter of its orbit. The Earth is still tilted, but the axis is leaning neither towards nor away from the Sun.  This happens twice per year (once during fall and once during spring).  On the equinox, the day and night are about the same length. The name equinox is derived from the Latin words aequus, meaning “equal”, and nox, meaning “night”. If you are standing at the equator, the Sun will appear directly overhead at noon; both poles receive equal sunlight. For us up here in the Northern Hemisphere we are observing the start of fall. Remember, however, that down in the Southern Hemisphere they will be celebrating the vernal equinox as they are moving into springtime.

So where does the egg fit into all of this? Some say the idea of balancing the egg was started by the ancient Chinese. Balancing an egg on the equinox symbolized equality and the balance of light and darkness.  You can do this yourself at home. It is a challenge to balance an egg, due to its shape and its viscous interior (not to mention the position of the yoke throwing it off balance).

Balancing the egg on the equinox became a phenomenon mainly because the idea was passed from person to person. People thought that the equinox was a special day on which you can balance an egg. Perhaps this gave people the extra motivation to really try and get that egg to stand up. Successful egg balancers felt validated by their triumphs, which furthered the notion that this could only be accomplished on the equinox. This most likely led to the big misconception that the cause is a special balance between the gravitational pull from the Sun and the gravitational pull of the Earth during the equinox. This is not the case. So what makes the egg stand?

The answer is: our efforts! Try it yourself. The egg can balance upright on any day of the year. It takes time, concentration, and steady hands, but it can be done. Perhaps that was the original intent of the egg balancing; it’s a way to meditate and ponder on the first day of the new season. So go forth, celebrate the coming of fall, and balance an egg!

Related articles

• Short Lessons on Equinoxes and Seasons (freetech4teachers.com)
• Equinox: Balancing Light and Dark (oneroomairycastle.wordpress.com)

Why is the sky blue and why is the sunset red and orange?

When I was a kid I heard that the sky was blue because it was the reflection off the ocean.  The light from the Sun, which appears white, is actually made up of all colors of the rainbow, when the light enters the atmosphere the colors can become separated (Imagine looking at light through a prism).  We know that bluer light travels in short, tight waves while redder light travels in longer waves. The shorter the wavelength, the more likely the light is to bounce off of an air molecule and become scattered. Blue light is scattered most in our atmosphere.

I also heard, when I was a kid, that when you observe a sunset and you see the shift in color from blue to red that you’re actually seeing the sun’s rays being filtered through the pollution.  Well, that sounds dismal.  It’s also not entirely true.

One of the main factors in determining a sunset’s color is the Earth’s atmosphere. The atmosphere is made up mostly of gases as well as some other molecules and particles thrown in for good measure.  The most common gasses in our atmosphere are nitrogen (78%) and oxygen (21%). The remaining single percent is made up of water vapor and lots of tiny solid particles like dust, soot & ash, pollen, and salt from the oceans.  There are also trace gasses like argon present. Also, depending on where you live, you’ll have to factor in that volcanoes can put large amounts of dust particles high into the atmosphere and pollution can add different gases or dust and soot to the air as well.

The atmosphere of the Earth can be thought of like a filter on a camera lens.

Light from a light bulb or the Sun may look white, but it is actually a combination of many colors. When you see light filtered through a prism you’ll see this white light split up into its separate colors, i.e. wavelengths.  White light is the colors of the spectrum blended into each other. And a rainbow that you see in the sky is actually a natural prism effect as rain drops split those different colors up.  The colors have different wavelengths, frequencies, and energies. Violet has the shortest wavelength. Red has the longest wavelength.  The shorter the wavelength means the more powerful the frequency.

So let’s put it all together in how light acts in the air surrounding our planet. Light moves in a straight line until it is messed with (be it gas, dust, ash, etc.). Once something interferes and gets in the way of the light wave it’ll scatter that light in different directions. The probability of light to be scattered by a molecule is proportional its wavelength, so shorter wavelengths of light are scattered much more often than longer wavelengths. In the case of air molecules, the molecules are much smaller than the wavelength of the scattered light, this is called Rayleigh scattering.

 

As the Sun sets later in the day, the light becomes less and less direct, think of what causes your shadow to be longer in the afternoon than during mid day. During mid day, sunlight is shining almost directly down through the atmosphere, while at the end of the day it is shining through more atmosphere. As the white sunlight travels through more atmosphere, more of the shorter wavelength colors are scattered away from our line of sight. Until finally as the Sun is about to set below the horizon, only red (the visible light with the longest wavelength) remains.

The Reason for the Season

Happy summer! Today is the Summer Solstice, our hemisphere’s longest day. Our Earth has seasons because its axis is tipped about 23 degrees, in other words it isn’t straight up and down. As the Earth orbits the Sun, the tilt causes us to experience seasons. In the United States, we have summer when the northern hemisphere is tilting towards the Sun. The summer solstice itself is the day when the axis is tilted most towards the Sun. From the ground, we can see that the Sun takes the highest path across the sky, and we experience the year’s longest day and shortest night. As the Earth continues in its orbit, the axis will slowly tilt away from the Sun. Little by little, we will see the Sun take a lower path across the sky and the days get shorter. Once the Earth has reached the opposite side of the Sun, its axis is tilted away and we experience winter. What’s happening in the Southern hemisphere during all of this? Exactly the opposite! They are having their Winter Solstice today.