Sunday, January 11, 2015

A Beautiful Comet Passes By



A faint but beautiful comet passed by the Earth recently, and the accompanying picture shows you why so many of us love observing these icy visitors from deep space.

Called Comet Lovejoy (after its discoverer, Australian astronomy hobbyist, Terry Lovejoy), the comet passed closest to Earth on Jan. 7th. It wasn't that close -- 44 million miles away. That's why you really need a telescope to see the comet well.

But in a telescope, as you can see in our image, made by Austrian astro-photographer Gerald Rhemann, a beautiful coma and tail have already formed.  (As always, click on the picture to see a bigger version.)

Comets are chunks of ice (with dust frozen within them) left over from the formation of our solar system. Comet Lovejoy is estimated to be about 2 to 3 miles in diameter. But when the ice comes nearer to the Sun, as Comet Lovejoy is doing until it rounds the Sun January 30th, the Sun's heat and wind evaporates the comet's ice and releases the dust that has been locked up inside it for billions of years.

As a result, a cloud of evaporated material form around the comet. Called a "coma," the cloud around Lovejoy is already about 400,000 miles in diameter!

The Sun's energy and particles push material away from the coma, producing the long and twisting tail we see, stretching for millions of miles, always pointing opposite the Sun. The tail of the comet is very tenuous -- astronomers like to say that a "comet's tail is the closest thing to nothing that something can be and still be something."

After Comet Lovejoy leaves our neighborhood, we estimate it won't return to the inner solar system for more than 8,000 years. So enjoy it now. You can do a Google image search and see pictures from many other astronomical photographers around the globe. (Just to avoid confusion, we should mention that this is the fifth comet Mr. Lovejoy has discovered, and so there were other Comet Lovejoy's in the past. The official nerdy name for this comet is C/2014 Q2.)


If you have good binoculars or a telescope, observing instructions can be found at:
http://www.skyandtelescope.com/astronomy-news/observing-news/spot-comet-lovejoy-tonight-122920141/ 
or
http://www.universetoday.com/118031/if-you-can-find-orion-you-can-find-comet-lovejoy/ 

Thursday, January 1, 2015

Happy 2015 and Happy Year of Pluto

 





Happy 2015, which is likely to be remembered in astronomy circles as the year we finally get close-up and personal with Pluto.

Nine years after its launch, the New Horizons spacecraft is "waking up" and getting ready for its encounter with distant Pluto this coming July. The intrepid little spacecraft has traveled almost 3 thousand million miles since its 2006 launch. It is so far away that its radio signals, moving at the speed of light, take 4 and a half hours to get to Earth. 


(This dramatic time delay will help you understand why Pluto is hard to see, even through the Hubble Space Telescope, and why astronomers are very excited that we will at last have a probe that can take detailed pictures as it flies by Pluto.)

If you are still confused about Pluto's status (why it got kicked out of the club of regular planets), you can read the background story I wrote at this PBS website:
http://www.pbs.org/seeinginthedark/astronomy-topics/planets-and-pluto.html

The only thing that has changed since I wrote that piece is that we now know that the dwarf planet called Eris is not bigger than Pluto, but the same size.

Another member of our solar system that got reclassified as a dwarf planet is the largest object in the asteroid belt, Ceres. To make 2015 more fun, the Dawn spacecraft will have a close encounter with Ceres in March and go into orbit around it, also giving us close-up images for the first time.

I am about to start teaching Astronomy 10A, my "Planets for Tourists" class at Foothill College and we will be paying special attention to Pluto and Ceres as their visitors approach them throughout the spring. I'll have more information on this blog too, as we learn more.

And for those of you who are near the San Francisco Bay Area, you are invited to a free lecture by Dr. Mark Showalter (who discovered two of the five moons of Pluto) at Foothill College Wed., Jan. 28, 2015, at 7 pm in our Smithwick Theater. If you live somewhere else, we will have the lecture up on YouTube on the Silicon Valley Astronomy Lectures channel after a few weeks:

http://www.youtube.com/SVAstronomyLectures

2015 is also the International Year of Light and the 100th anniversary of the completion of Einstein's General Theory of Relativity. Both of these -- light and relativity -- are important to our understanding of the universe, so we astronomers will be happily joining in both celebrations.  Perhaps you will too, as events are announced.

Here's wishing you a good new year from the old Astronomy Professor who keeps this blog.


Wednesday, December 24, 2014

An Amazing Image of Saturn's Rings for the Holidays



Carolyn Porco, the dynamic leader of the Imaging Team for the Cassini Mission (exploring Saturn and its neighborhood), has sent a remarkable holiday greeting card from Saturn and I wanted to share it with you.

What we are looking at is a view of the inner part of Saturn's complicated ring system (mainly the so-called B ring.) We are seeing about 750 miles of the white rim of the B ring, beyond which is the dark emptier space called the Cassini Division. You can see a number of thin "ringlets" in that division toward the upper part of our picture.

But what is really stunning is what the long shadows cast by the Sun reveal at the edge of the bright main ring. You can see peaks or thin mountains of ice particles, sticking up more than a mile and a half (2 km) above the plane of the rings. Compare those heights with the typical height of the ring system, which is about 10 meters (or about 30 feet) in most places.

Here is what Carolyn says about the image, "Cassini scientists believe that this is one prominent region at the outer edge of the B ring where large bodies, or moonlets, up to a kilometer or more in size, are found. It is possible that these bodies significantly affect the ring material streaming past them, and force the particles upward, in a "splashing" manner."

She continues, "This image [taken in 2009] and others like it are only possible around the time of Saturn's equinox, which occurs every half-Saturn-year, or about every 15 Earth years. The illumination geometry that accompanies equinox lowers the sun's angle to the ring plane and causes structures jutting out of the plane to cast long shadows across the rings."

The rings of Saturn are made of billions and billions (as Carl Sagan used to say) of individual chunks of ice -- mostly water ice. The particles range in size from smaller than a sand grain to larger than a modern SUV. We have known for some time that the interaction of moons and rings in the Saturn system can create a wide range of artistic patterns using the ring particles as their raw materials. But these tall icicles or icy towers are among the most spectacular we have ever seen.

Happy Holidays. May 2015 bring all of us more amazing views of our cosmic environment and increase our understanding that the differences that separate us on Earth are so trivial compared to the truly alien nature of what's out there.


[Click on the image to make it bigger and see even more detail!]


Tuesday, December 16, 2014

You Could Name a Crater on the Planet Mercury




The team of scientists and educators behind the Messenger spacecraft orbiting the planet Mercury is giving the public the chance to nominate artists, writers, or composers whose names deserve to be on one of five craters on the hot little planet closest to the Sun.

There have been a number of publicity campaigns recently that deal with naming things, but this one is the real thing. By international agreement, the naming of worlds and features in space is done by a special committee of the International Astronomical Union (the U.N. of astronomers.) But the committee is happy (when there is no duplication or veering from tradition) to honor the wishes of the discoverers. And the Messenger team, having discovered many new craters on the wonderful close-up images they have obtained, is happy to give the public a chance to participate.

Also by agreement, Mercury's huge population of impact craters is going to be named only for well-known composers of music, serious artists, and writers of renown. The most famous people in these categories (Beethoven, Van Gogh, Tolstoy) already have craters named for them. So now, it's time to find less well-known people from a wide range of cultures to be honored. The Messenger team will submit their 15 favorite entries to the committee to select the names of five newly discovered craters. You can see photos of the craters and get all the details on the contest website: http://namecraters.carnegiescience.edu/home

You are encouraged to check first to see if your favorite candidates don't already have a crater. I was pleased to see that Jean Sibelius, one of my favorite composers, was already on the list. On the other hand, Alexander Scriabin, who took romantic music in amazing new directions, and wanted to combine sound and light long before there were laser shows, still hasn't got a crater to his name anywhere in the solar system. Maybe some of us have to nominate him.

The rules say anyone you nominate has to have been publicly known for at least 50 years and dead for at least three. But beyond that, you are encouraged to get -- pardon the expression -- creative. The contest starts today and is open for only one month. There is no prize, only the satisfaction of knowing that you have helped put someone whose work you really enjoy on another world.


To see all the people who have given their names to features in the solar system, you can search at: http://planetarynames.wr.usgs.gov/AdvancedSearch  (putting the last name into the field called "Feature Name.")

Wednesday, December 10, 2014

The Lake that Built a Mountain on Mars




NASA’s instrument-laden Curiosity Rover is now at the foot of Mt. Sharp, its ultimate target on Mars. New results from the rover have confirmed and filled in our ideas about what the 3-mile high mountain is doing in the middle of 96-mile wide Gale Crater. And, most important, the new observations give us even more confidence in the notion that ancient Mars was very different from Mars today – it may well have had a much thicker atmosphere, flowing rivers, and occasionally full lakes of water.

Mt. Sharp is an interesting mountain, in that it seems to be built up out of layer after layer of sediment. This material might have been carried to the center of the crater by either water or winds, scientists thought. The new results indicate that both water and wind may have had a role in building Mt. Sharp over the millennia.

We already knew that one or more dry river channels end at Gale Crater, making it likely that long ago, water probably flowed into the crater. Over long periods of time, the crater lake may have formed and evaporated again and again. Rivers flowing over the red sands of Mars would have carried quite a bit of sediment into the crater and would have deposited this material in its center. As the central mountain began to accumulate, the next river flood would lap up against it. The resulting waves could carry material higher than the river’s original level, thus building up the mountain further.

When the lake was dry, the big wind storms, that other instruments have shown us are a regular feature of Mars weather, could have added wind blown sand to the top of the mountain. So Mt. Sharp could have grown during both wet and dry periods.

Curiosity is only at the bottom of the mountain right now, but it has the ability to climb up to higher layers over the coming months. Scientists are very interested in what the layers higher up might reveal to us about how Mt. Sharp grew and how the climate on ancient Mars changed as time passed.

Our top picture, taken on Mars on Nov. 2, shows some of the layers building up at the bottom of Mt. Sharp in a formation scientists have nicknamed "Whale Rock." For a version of this picture that shows scale, see: http://photojournal.jpl.nasa.gov/figures/PIA19081_fig1.jpg 


The picture below is an earlier "selfie" that the Curiosity rover took showing its instruments and cameras at work. Click on either photo and you'll see a larger version, full of amazing detail -- straight from the surface of Mars!

Sunday, November 30, 2014

A Rogue Black Hole Escaping its Galaxy


Astronomers have announced the possible discovery of a big black hole that has escaped the galaxy of stars that gave birth to it, a phenomenon that had been predicted in theory, but not observed.

Galaxies (great islands of stars) that share a neighborhood in space can sometimes collide. If each has a big black hole at the center -- as many galaxies do -- usually the two black holes collide and merge. But, under the right conditions, the black holes can engage in a "game of pool" (billiards for those with more refined tastes.)

One of the big black holes can "recoil" or "rebound," and wind up being shot out of the combined galaxies. This is a pretty unusual circumstance, and astronomers have been searching for an example. Now, it looks like they may have found one.

The project involved observations with several telescopes, including the Swift satellite and the giant Keck telescope in Hawaii. The galaxy that remains is called Markarian 177 (a name that comes from a catalog of disturbed galaxies made by an Armenian astronomer.) The object that may be the escaped black hole has a number from the Sloan Digital Sky Survey catalog -- SDSS1133.

The galaxy is about 90 million light years away in the bowl of the Big Dipper. As shown on the accompanying image, the rogue object is about 2600 light years from the center of the galaxy.

As black hole fans are now probably thinking as they read this, it's not the actual black hole we are seeing on this highly magnified Keck infra-red image. Black holes are black and hard to see against the black of space. The SDSS object is a black hole surrounded by gas and dust that the black hole is "eating." It is the ring of "food" that we see glowing on the picture.

There is a small possibility that the SDSS object is something else entirely, such as an exploding star, although there is evidence from earlier images against that interpretation. Astronomers plan to use the Hubble Space Telescope to get even more information about this mysterious pair of objects.

If the black hole interpretation holds up, this will be a new creature in the "astrophysical zoo" to add to the many weird things we have been discovering lately. Rogue black holes are already in use in science fiction (such as Allen Steele's novel "Spindrift") and may now join the real universe as well.

Thursday, November 20, 2014



The Movie Interstellar: The Science Behind the Story

Lots of my students are asking questions about the new film Interstellar.  I have been hearing about the movie for some time; the studio even sent me a “teachers’ guide” that was not especially useful, but piqued my interest.  Most exciting for me was the news that the scientific advisor (and one of the producers of the film) was Prof. Kip Thorne of Caltech, who is arguably the world’s expert on black holes and wormholes -- and designed the science behind the “galactic subway system” in Carl Sagan’s novel and film Contact.

I wrote to Dr. Thorne and he told me that he had indeed been involved with Interstellar, and had, in fact written a book, entitled The Science of Interstellar, to explain the complicated science that was the basis for some of the more intriguing scenes and events in the film.   The book also tells the story of the film, which was always supposed to be strong on science, and, at one time, was set to be directed by Stephen Spielberg.  But that original deal fell apart and it took a while to bring Christopher Nolan, the film’s current director, into the project.

Dr. Thorne wasn’t the only scientist involved in the long period before the movie went from an idea to a completed production.  Yesterday, I was talking with Dr. Frank Drake, the father of the scientific search for extra-terrestrial intelligence, and he told me that he was on one of the early panels of scientists brought together (with Stephen Spielberg) to make sure the plot stayed close to real science and possible science.

With Christopher Nolan and his brother Jonathan (a writer of screenplays) involved, the film evolved from the script Dr.Thorne and producer Lynda Obst had first envisioned, to include much more about a future Earth facing ecological disaster.  Still, the original thought, to portray black holes and worm holes as accurately as modern science can make it, was high on everyone’s list of priorities.

A black hole is a place where the death and collapse of a huge star has produced such strong gravity, that space itself is “warped” -- and nothing, not even light can escape.  Near a black hole, time proceeds more slowly than in the rest of the universe, and this change in the flow of time becomes a major plot element in the movie.  Both the existence of black holes and their strange effect on time have been demonstrated by many experiments and are well established.

A wormhole is more speculative, but something Einstein himself thought a bit about.   It’s a place where a black hole or some other unusual feature of space and time becomes a tunnel (or short cut) from one place in space to another place very far away, or even to another time.  In a wormhole, the dangerous effects you would feel falling into a black hole are somehow kept at bay, so that a spaceship can go through it to elsewhere or elsewhen.

Both wormholes and black holes get major roles in Interstellar.  The astronauts in the movie first use a wormhole to get from our Milky Way Galaxy to another galaxy far far away.   Then, they wind up in the new galaxy in a location where there is a massive, spinning black hole, with planets around it.  I won’t give anything else away, except to say that the special effects showing the wormhole and the gargantuan black hole were composed from calculations made by Dr. Thorne and his team at Caltech, fed directly to the computers of the special effects team for the movie – and they are truly SPECTACULAR.

For more, I recommend reading Dr. Thorne’s book (pictured in this post) and going to see the movie – especially if you are a black hole fan.  Dr. Thorne also has a web page with some animations at: https://interstellar.withgoogle.com/transmissions