A Total Eclipse of the Moon Sunday Evening September 27

I thought you might like advance notice of a very nice upcoming lunar eclipse visible next Sunday evening in North and South America and in the early morning in Europe and parts of Africa and west Asia. Below are the basics in the form of questions and answers.  All you need to enjoy the eclipse is clear skies and (on the American west coast) an unobstructed view toward the East.

Next week you will start reading media reports about this being both a “blood moon” and a “supermoon,” but don’t pay too much attention to that.  The Moon will be a bit closer to the Earth in its orbit than average, making it look a bit bigger, but the difference is not especially significant.  And every lunar eclipse could turn reddish, as explained below.  It’s rarely the color of blood, but the media love anything that can be connected to thoughts of violence.

The Sept. 27, 2015 Total Eclipse of the Moon

1. What Is Happening?

On Sunday evening Sept. 27, a total eclipse of the Moon will be visible from throughout the U.S. (and North and South America.) In a lunar eclipse, the full Moon & the Sun are exactly opposite each other in our sky, and the Earth gets between them. This means the Earth’s shadow falls on the full Moon, darkening it.  It’s a nicely democratic event; no special equipment is needed to see it (provided it’s not cloudy or foggy.) Plus it happens early in the evening; kids can watch & still be awake for school next day.

2. When Will the Eclipse Happen?

The table below is for the U.S. (for other countries and continents, see: http://www.timeanddate.com/eclipse/lunar/2015-september-28  which can be set for your home location.) 

Event	Pacific	Mountain	Central	Eastern
Partial eclipse starts	Moon not up	7:07 pm	8:07 pm	9:07 pm
Total eclipse starts	7:11 pm	8:11 pm	9:11 pm	10:11 pm
Total eclipse ends	8:23 pm	9:23 pm	10:23 pm	11:23 pm
Partial eclipse ends	9:27 pm	10:27 pm	11:27 pm	12:27 am

As Earth’s shadow slowly moves across the Moon, we first see only part of the Moon darkening (partial eclipse).  When our shadow completely covers the Moon, we see a total eclipse. The best time to start watching is about a 20 minutes before total eclipse begins, when much of the Moon is already darkened. 

NOTE: On the west coast, the eclipse will start low in the Eastern sky, so make sure your observing location has an unobstructed view toward the Eastern horizon.

3. What is Visible During a Lunar Eclipse?

As the shadow of the Earth covers the Moon, note that our natural satellite doesn’t become completely dark.  Some sunlight bent through the Earth’s atmosphere still reaches the shadowed Moon and gives it a dull brown or reddish glow.  The exact color of the glow and its darkness depend in part on the “sooty-ness” of our atmosphere – how recently volcanoes have gone off and how much cloud cover, storm activity, and human pollution there is around the globe. 

Once the Moon is totally eclipsed, the stars in the sky should become more easy to see.  What makes this eclipse a little bit unusual is that, by coincidence, it is happening just one hour after the Moon has reached the closest point in its monthly orbit around the Earth.  So the Moon will look a bit larger in the sky than usual.  (The media will be calling it a “supermoon,” but the effect is pretty subtle for the average person.)

4. Is it Safe to Watch, and How do I Watch?

Since the Moon is safe to look at, and eclipses make the Moon darker, there’s no danger in watching the eclipse with your eyes or a telescope.  (The dangerous eclipse is the solar one, where it is the Sun that gets covered.) And lunar eclipses don’t require you to go to a dark location.  Bring binoculars to see the Moon larger, but just your eyes are fine.  Since the total eclipse will last for an hour and 12 minutes, be sure to take someone along with whom you like to spend time in the dark!

5. What Can I Tell My Kids (or Kid Brother or Sister)?

Suggest that they take a careful look at the shadow of the Earth as it moves across the bright face of the Moon.  What shape is it?  The round shape of the Earth's shadow suggested to the ancient Greeks, more than 2000 years ago, that the Earth’s shape must be round too.  Eclipse after eclipse, they saw that the Earth cast a round shadow, and deduced that we lived on a round planet (long before we had pictures of it from space.)

Two Giant Black Holes Whirl at the Core of an Active Galaxy

Using the Hubble Space Telescope, a team of astronomers has found that a superbright (active) galaxy is powered at its core by two supermassive black holes whirling around each other in only a bit more than one year. This remarkable galaxy is called Markarian 231, after the Armenian astronomer who made a catalog of such active galaxies (with unusually bright centers.)

The galaxy is almost 600 million lightyears away, so we cannot see the tiny area in the center which contains the black holes directly. But a detailed study of the ultraviolet light from the core of the galaxy strongly implies that a black hole containing enough material to make 4 million Suns is whirling around a much larger black hole (with mass inside for 150 million Suns.)

Think about those numbers! You would not want to live near such overweight black holes, but luckily they are confined to the central regions of galaxies (including our own Milky Way) and are not a feature of the galactic outskirts where our solar system resides in comparative peace.

The idea that enormous black holes like this can share the same environment is not news to astronomers, but it's nice to have such a clear example. We now know that the giant islands of stars called galaxies probably all started much smaller and have been growing through "mergers" (if you'll pardon our appropriating a word from the world of business.)

Smaller galaxies are "eaten" by larger ones, or two galaxies of equal size are attracted together by their mutual gravity. If the smaller galaxies each contain a big black hole, both black holes will wind up near the center of the merged object. If the original galaxies had orbiting motion around each other, their inner black holes will have some of that motion, and can circle each other until -- later -- their gravity also pulls them together.

The fact that the two black holes in Markarian 231 take only about one year to go around means they will collide in a few hundred thousand years (a long time compared to the presidential nomination season, but short for galaxies.)

When two black holes collide you get -- surprise, surprise -- a bigger black hole. But we have caught Markarian 231 in the act of a small galaxy having been swallowed, but before the two black holes had time to merge. There are stars and huge clouds of gas and dust being pulled in by the pair of black holes and as they are torn apart and whirled around, they give off a lot of energy.

It's that energy of doomed material (before it falls into one or the other black hole) that makes Markarian 231's center so unusually bright.

The method used to find the waltzing, whirling black holes in this galaxy holds promise for finding other pairs of giant black holes in other distant galaxies. And the existence of such pairs of hungry black holes is good evidence that our merger theory of how galaxies "bulk up" is correct.

(By the way, our image, above, is a painting, based on the Hubble data.  As we said, we can't take a picture of the inner part of the galaxy.  But below is a Hubble image of the entire disturbed galaxy with its bright center.)

Good Meteor Shower This Wednesday Night

This Wednesday evening and Thursday morning there will be one of the best meteor showers you and your family can see.

This is a great year for the Perseid meteor shower, because it is happening during the phase of the Moon called New Moon (which is when the moon is absent from the sky).  So there will be no moonlight to interfere with seeing the faint “shooting stars” of the meteor shower.

The best night is the evening of Wed, Aug. 12 and morning of Thur., Aug. 13, although there could be significantly more meteors on the night before and the night after too.  Meteors (which have nothing to do with stars) are pieces of cosmic dust and dirt hitting the Earth’s atmosphere at high speed and making a flash of light.

The peak of the shower is predicted to happen around 1 am PDT Aug. 13th, which means that after it gets dark on Aug. 12th, there should already a good number of meteors to watch for.

Here are a few tips for best viewing:

8 HINTS FOR TAKING A METEOR SHOWER

1. Get away from city lights and find a location that’s relatively dark

2. If it’s significantly foggy or cloudy, you’re out of luck

3. Your location should allow you to see as much of the dome of the sky as possible

4. Allow time for your eyes to get adapted to the dark (at least 10 -15 minutes)

5. Don’t use a telescope or binoculars – they restrict your view (so you don’t have to be part of the 1% with fancy equipment to see it; this is a show for the 99%!)

6. Dress warm – it can get cooler at night even in August

7. Be patient (it’s not fireworks): keep looking up & around & you’ll see flashes of light

8. Take someone with you with whom you like to spend time in the dark!

The Perseid meteors are cosmic “garbage” (dust and dirt clumps) left over from a regularly returning comet, called Swift-Tuttle (after the two astronomers who first discovered it).  The comet itself returns to the inner solar system every 130 years; it was last here in 1992.  During each pass it leaves dirt and dust behind and it is this long dirt and dust stream that we encounter every August.  Some experts are predicting we might briefly encounter an especially crowded part of the debris stream this time.

Each flash you see is a bit of material from the comet hitting the Earth’s atmosphere and getting heated up (and heating up the air around it) as it speeds through our thick atmosphere.  Both the superheated dust and dirt and the heated air contribute to the visible light we observe.  Since comets are left-overs from the early days of our solar system, you can tell yourself (or your kids) that each flash of light is the “last gasp” of cosmic material that formed some 5 billion years ago.

[Note: image from Mike Hanley, American Meteor Society]

New Pluto Images Reveal Glaciers Flowing from the Heart

New images released from the New Horizons spacecraft's encounter with Pluto reveal a reddish world, where water is as hard as rock, and substances that are gas on Earth have become ice glaciers. The beautiful color picture with this post shows you a section of Pluto that includes the heart-shaped feature named after Clyde Tombaugh, Pluto's discoverer. The left lobe (section) of the heart is being called the "Sputnik region," after the first satellite humanity ever sent into outer space.

Why is Pluto reddish? The team's first thought is that ultra-violet light from the Sun acts on the gases in the thin Pluto atmosphere -- methane (natural gas) in particular -- and breaks them apart and reforms them into more complicated combinations of hydrogen and carbon. Eventually, the molecules get so complex and heavy, they fall out of the air and coat the surface. Such hydrocarbons tend to be reddish when we see them on other worlds.

The New Horizons craft has only returned about 5% of the data it has stored in its memory, but even first results show haze layers in the Pluto atmosphere that support the notion of the air having chemical reactions going on, despite the cold.

If you look at the Heart in the picture, you can see that the left Sputnik region (which is about the size of Texas) has a thicker covering of ice than the right half of the Heart. Our black-and-white image shows a close-up about 250 miles wide in the northern part of Sputnik. At the top you see some of the older, cratered terrain that is above the Heart. But below that, the Heart itself is smooth and young-looking (no craters, which are a sign of age.)

The smooth ice we see is made of nitrogen, methane, and carbon monoxide, its top layers freezing out of the air when Pluto gets further from the Sun. (Pluto was closest to the Sun in its almost 250-year orbit in 1989, so we are just moving away from the time that Pluto is warmest.)

At Pluto temperatures, an ice made of nitrogen will very slowly flow, like a glacier flows across the landscape on Earth. The arrows on our black-and-white image show the direction scientists think the ice is flowing in Sputnik. At Friday's press conference, the experts said that their impression of Sputnik is that it's a very young region (geologically speaking) -- perhaps only tens of millions of years old. (For comparison, we think Pluto, like the rest of the solar system, is 4600 million years old.) Its glaciers have moved into any available regions next to Sputnik, and have filled valleys and craters on all sides.

Look also at the intriguing "polygon" patterns (many-sided figures) in the ice of Sputnik on our picture. They look like huge, geometric cells in the ice, perhaps half a mile or more deep. One possibility is that in these cells, hotter material from deeper inside is slowly rising, a process called "convection."

These images and ideas are just the (pardon the expression when discussing Pluto), just the tip of the iceberg. It will take 16 months for the full set of pictures and data to be sent back from New Horizons. Better images are expected in September, for example. Stay tuned.

In this last image, you see Pluto (left) and its large moon Charon in realistic color.  Such a dramatic pair at the outskirts of our solar system!

Getting Close-up with Pluto's Moon Charon

One of the most intriguing things about Pluto is that it is more of a double planet than a planet with moons. One of Pluto's moons, Charon (pronounced like Sharon or Karen; both are used) is half the size of Pluto. No other moon we know is this big compared to the planet it orbits -- just another way that the Pluto system operates outside the usual rulebooks.

The diameter of Charon has been measured to be 751 miles, about the size of Texas. Charon has settled into the most comfortable orbit around Pluto that nature permits. It rotates and revolves in 6.4 Earth days, which is also the rate at which Pluto turns. This means that the day on Pluto is the same length as the Charon month, which hurts your head if you try to think too much about it.

Now the New Horizons craft is starting to send back images of Charon as well, and again, we are surprised. Our photo shows a black and white global picture of Charon that has been tinted with actual color information from one of the other instruments. The New Horizons team is informally referring to the striking dark spot near the top of the image as "Mordor," much to the delight of fans of the Lord of the Rings trilogy.

But the inset in our picture is the most interesting. It shows an area of about 240 miles across (from top to bottom) and you can see some of the trenches and canyons that we are finding on Charon. Craters are also visible. Near the top left, we see a giant ice mountain sticking out of a trench. The NASA news release says: “This is a feature that has geologists stunned and stumped.” How did the mountain get or grow in there? It's those kind of odd mysteries that scientists live for.

(By the way, if you were asking yourself why the big moon has two different ways of pronouncing its name, it's a romantic story. The proper pronunciation from Greek mythology is like "Karen". But James Christy, the astronomer who discovered the big moon in 1978, secretly wanted the name to also remind people of his wife Charlene. So he likes making the name sound more like "Sharon." Astronomers (like most people) love romantic stories, so many use the pronunciation that Christy likes.

And Pluto itself has a name with a secret -- the astronomers at the Lowell observatory wanted to name it after their patron and founder, Percival Lowell, but we don't name planets after real people. So when a schoolgirl in England suggested the name Pluto to them, they jumped at it, since the first two letters are Lowell's initials.)

First Close-up Peek at Pluto's Surface

Here is the first detailed image of the surface of Pluto, released today, and it's already providing surprises. The yellow bar gives you a sense of scale; Pluto's diameter is 1473 miles (just measured by New Horizons), so we are seeing only a small part of it here.

The angular structures in the top half of the picture are mountains, the tallest being about 2 miles high. Most likely these mountains are made of frozen water -- it's so cold on Pluto that water becomes harder than rock. In fact, it is likely to be layers of "hard frozen water" that make up much of the surface of this distant world.

The biggest surprise is that the surface shows no craters, large or small. Craters are made on every world when chunks of rock or ice hit and carve out a circular depression. Since every world is regularly being hit by pieces of cosmic debris that fly through our solar system, any world without craters must have a way of erasing them pretty quickly after they form. Scientists are estimating that the absence of craters means that the surface of Pluto is being refreshed by some process, and can't be more than a hundred millions years old -- which is very YOUNG compared to the 4600 million year age of the solar system. What keeps the surface of this little world refreshed and erased is the first challenge Pluto has thrown in the face of the scientists eager to study it.

The Revenge of the Dwarf Planets

Pluto Seen July 11, 2015 from NASA's New Horizons Spacecraft

This coming Tuesday, July 14th, humanity will -- for the first time -- fly by the world formerly known as planet Pluto.  Actually, the New Horizons spacecraft will be flying by a double world, because Pluto has a giant moon, Charon, which is half its size.  I can't wait to see the pictures.

In fact, see the Pluto image with this post -- it's from yesterday and already shows intriguing spots and circular areas.  Check out the even better new pictures and information as they are revealed this coming week and month.  You can find them at: http://pluto.jhuapl.edu/ 

When the data from the flyby are returned to Earth -- and they will take a year to download (and you think your connection is slow!!) -- we will have completed our first-look exploration of all the main worlds known when most of my readers were born.

Pluto was "kicked out of the planet club" only because a whole bunch of other "Plutos" were found beyond Neptune.  Pluto turned out to be the first of its kind (found by Clyde Tombaugh at Lowell Observatory in 1930), but now we've found Eris (which is the same size as Pluto) and several other round icy worlds that are smaller versions of them.  We probably should have picked a less insulting name than dwarf planet, but we used the word dwarf successfully in combination with star and galaxy, so we didn't anticipate so much public hostility to it.  For the full story, see: http://www.pbs.org/seeinginthedark/astronomy-topics/planets-and-pluto.html 

A few of Clyde Tombaugh's ashes are aboard the New Horizons craft.  You can read his own story of the discovery at: http://astrosociety.org/wp-content/uploads/2013/02/ab2009-23.pdf

Here is Clyde Tombaugh with your friendly blogger in 1985

Pluto is known to have four smaller moons, and others may yet be discovered in the coming weeks.  Pluto also has a thin changeable atmosphere, which instruments will be investigating as we fly by.

Another world that got reclassified in the Pluto saga was Ceres, the largest asteroid, which is now also called a dwarf planet.  Ceres is the only member of the asteroid belt between Mars and Jupiter to be round.  The Dawn spacecraft is settling into a lower and lower orbit around Ceres this summer and fall, and will be sending back never-before-seen details of what this intriguing world (about the size of Texas) looks like.

So it's going to be a summer of dwarf planet discovery.  They are going to be in the news so much, maybe we'll forget the issue of the name and enjoy them for what they have to tell us about the history and diversity of the solar system.

If you are really into the Pluto encounter, the most comprehensive post about what's happening is Emily Lakdawalla's at: http://www.planetary.org/blogs/emily-lakdawalla/2015/06240556-what-to-expect-new-horizons-pluto.html