Reading Recommendations: Pluto's Discovery; the Astronomy of Harry Potter

From time to time, I like to use this page to recommend some outside reading on interesting aspects of astronomy that you might enjoy. I have two recommendations this time, both from a column (called "Astronomy Beat") that I had the pleasure of editing for a number of years for the Astronomical Society of the Pacific.

This week was the anniversary of the discovery of Pluto, in February 1930, by Clyde Tombaugh, a young observer fresh off the farm and doing his first project for the Lowell Observatory. Before Tombaugh passed away, I was fortunate to be able to persuade him to write up the circumstances of his discovery. (This week's picture shows me -- with a lot more hair -- in 1985 with Tombaugh.) If you want to read his story, you can see it at:http://www.astrosociety.org/pluto/ab2009-23.pdf 

Another fun column covered the astronomy of Harry Potter and how teachers have used the popularity of those books and movies to encourage more interest in astronomy. Sirius Black (named after the brightest star visible in our sky) is only one of many astronomical references in the world of Hogwarts. Check out that column at:
http://astrosociety.org/wp-content/uploads/2013/02/ab2011-66.pdf

Links to all the columns in the series that have been made available to the public can be found at: http://astrosociety.org/publications/astronomy-beat/

I recommended the column by Frank Drake in an earlier post, but for readers new to the AstroProf pages, it has the story of how Frank Drake came up with the way of estimating the number of intelligent civilizations we might contact in our galaxy.  See: 
http://astrosociety.org/wp-content/uploads/2013/02/ab2010-46.pdf

(His way of estimating became known as the Drake Equation and is now part of popular culture.  You can see it discussed on the TV comedy, the Big Bang Theory for example, here: 
http://www.youtube.com/watch?v=cj_Bz_Cqu0g )

Discovery of the Smallest Planet Yet

Scientists with the Kepler Telescope in space announced the discovery today of the smallest planet yet found around another star, with the catalog number Kepler 37b. The new planet is smaller than Mercury, and only about 1/3 the size of Earth. That our technology is now good enough to detect a planet this small, when it is 210 light years away, is a tribute to the engineers and scientists involved with Kepler.

The new planet, one of three orbiting the nameless star we call Kepler 37, takes only 13 days to go around its star. (Mercury, the closest planet to the Sun, takes 88 days to orbit.) So conditions on the newly found planet are scorchingly hot. In one of NASA's news stories, the authors comment that a penny, laid out in its intense starlight, would soon melt. 

It was only in the last year or so that we were able to find Earth-size planets orbiting other stars, and now here we are finding much smaller worlds. You can compare the planets in the Kepler 37 system with those in our own solar system in the NASA image above.

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By the way, several readers asked me to comment on the chunk of rock that exploded over the Ural Mountain region of Russia over the weekend. As best we can tell, there was no connection between this cosmic visitor and the one I previewed in my previous post. It's just a coincidence that one came close by the Earth and the other fell toward Earth in the same 24-hour period. The smaller Russian chunk exploded high up, making a spectacular fireball in the sky. It appears that only small fragments made it to the ground. The injuries that were widely reported in the media came from the shock wave that spread out from the explosion in the atmosphere. This blast wave shattered windows, just at the moment when people were attracted by the fireball's intense light to look outside.

The two visitors are vivid reminders that we live in a system that has quite a bit of "cosmic debris" among the planets. We (and the Moon, and all other objects in the solar system) are subject to being hit by some of that debris at any time. Astronomers are working hard to catalog all the larger (and most dangerous) chunks that cross the Earth's orbit around the Sun. But the smaller chunks are so hard to see and so numerous, it's not currently possible to get to know them and predict their collisions with our planet.

Asteroid Passing Close to Earth on Friday

Artist's Impression from NASA/JPL

This Friday (2/15) a small asteroid will fly by the Earth at quite close a distance -- only about 17,000 miles above our planet's surface.   That's closer than some of the satellites that orbit the Earth. Closest passage will be around 11:30 am Pacific time on Friday, but it would not be visible without a telescope even if it were passing during night time.

There is nothing to fear from this flyby -- the asteroid is going to miss the Earth and shoot by us at eight times the velocity of a high-speed rifle bullet.  But it does remind us that we live in what some astronomers call "a cosmic shooting gallery," where chunks of rock and ice left over from the early days of our solar system still fly around and occasionally hit a planet or a moon. (You can see billions of years of such hits if you point a pair of binoculars at the Moon. Having no atmosphere, oceans, vegetation, or teenage children to erode its surface, our Moon preserves every impact as a round crater on its surface.)

This particular asteroid, discovered by a Spanish observatory last February, is given the catalog name of 2012 DA14.  We are not sure of its exact size, although we will learn much more about it as it swings by.  We estimate that it's about 90 to 150 feet in diameter, although it is probably not round, but shaped like a fresh potato (as shown in the JPL artist's conception that accompanies this article.)  If something this size were to hit the Earth at typical near-Earth asteroid speeds, it could take out an entire city, much like a nuclear bomb.  It could wreak devastation even if it never reached the surface, but exploded from the heat of friction in the atmosphere. 

You can understand why astronomers are working hard to catalog every significant-sized chunk of rock that crosses our planet's orbit.  Of course, the smaller the object, the harder it is to see when it's far away. But this way, if one of these larger cosmic "bullets" does have our name on it, we can know about far in advance and prepare.  With enough notice, we might even have the technology to nudge it aside and help it to miss our planet.  This would be the kind of project that would make astronomers and NASA popular for a while!

An Amazing Picture of an Active Galaxy by the Hubble and an Amateur Astronomer

This past week, the scientists at the Space Telescope Science Institute released a remarkable picture, which combines Hubble images with those taken by advanced amateur astronomers on Earth, and I'm glad to be able to share it with you.   (Click on the picture to make it bigger.)

In the image, we're seeing the central part of an "active" or disturbed galaxy about 25 million light years away, with the catalog number M106.  You can see the yellow center of the galaxy, crowded with stars whose light blends together.  You can also see its great spiral arms of stars, gently curving away from that center.  They are outlined with blue stars and regions where gas is being heated by stars and glowing red.  Those arms go much further out than the boundaries of this picture.  

But what is especially interesting is that there are also great jets of glowing red gas, which are not part of the flat spiral structure of the galaxy.  Instead, they are at odd angles to the galaxy's disk.  What we are seeing there are great clouds of glowing hydrogen -- the most common element in all galaxies.  But what makes them glow so intensely?  Astronomers have good evidence that they are energized by radiation (not visible to the human eye) coming from a super-giant black hole at the center of the galaxy.  

Neither the black hole (somewhere in the middle of the yellow center) or its rays of energy are visible here.  But when those rays hit the gas that is the "raw material" of such galaxies, they make it glow with a fierce intensity.  

This beautiful photograph was assembled by an amateur astronomer, Robert Gendler, a doctor living on the East Coast, who has made astronomical photography his hobby and his passion.  It's quite a coup to have his photograph used and released by the Hubble scientists.  For more of Dr. Gendler's photos, see his web site at: http://www.robgendlerastropics.com/

If you want to learn some basic information about black holes, you can check out a little video of a 6-minute talk I gave about them at the SETI Institute: http://www.youtube.com/watch?v=7DX_cc-IjpY 

Amateur astrophotographer R. Jay Gabany also contributed to the image.  You can see his image (with less detail) but showing the whole galaxy and really emphasizing the gas excited by the black hole at:
http://apod.nasa.gov/apod/image/1103/lrg_ngc4258gabany.jpg