Sunday, January 8, 2017

A Photo of the Earth and Moon from Mars!


   NASA has just released a remarkable image of the Earth and the Moon as seen from a spacecraft orbiting Mars. Our planet and Mars were 127 million miles apart when the photo was taken.
   The Mars Reconnaissance Orbiter (MRO) has been orbiting Mars since 2006, collecting very detailed close-up images and data about the surface of the red planet. In this case it was used to capture a photo of Earth and Moon with both bodies in the same frame. The image was taken at a time when the Moon was behind Earth as seen from Mars, so it shows the Earth-facing side of our natural satellite.
   Even at Mars' distance, the image of the Earth reveals continents. Australia is the reddish-brown feature in the center. Seeing ourselves as a tiny disk of light in the blackness of space can help remind us that we share a fragile and beautiful planet in our journey through space.

Sunday, December 11, 2016

My Mars Science Fiction Story Now Free on the Web


As some of you know, I have begun writing science fiction stories (based on ideas from astronomy) in recent years and two of them have now been published.
The first story (“The Cave in Arsia Mons”) was published in a small-press anthology of Mars stories entitled “Building Red: Mission Mars,” and deals with a surprising discovery made in a cave on the side of one of the giant volcanoes on the red planet.
The publisher has now given me permission to put the story on-line free and it can be found at: https://www.researchgate.net/publication/282914928_The_Cave_in_Arsia_Mons
If you click on the blue “download” button just above and to the right of the title, you get a PDF file with the story and a bit about the actual discovery of martian caves.
My second story (“Supernova Rhythm”) is just being published in an anthology entitled “Science Fiction by Scientists,” edited by astronomer Mike Brotherton, and published by Springer. It concerns an advanced civilization out there that can play music using exploding stars:
http://www.springer.com/us/book/9783319411019 or
https://www.amazon.com/Science-Fiction-Scienti…/…/3319411012
When I retire from teaching at Foothill College in June 2017, I am looking forward to spending more time writing science fiction stories like this.  For my listing of a wide range of science fiction stories with good astronomy, see: http://www.astrosociety.org/scifi 

Sunday, November 27, 2016

A Hidden Baby Galaxy in our Cosmic Neighborhood


An international team of astronomers, led by researchers at Japan’s Tohoku University, has just reported finding the faintest satellite galaxy ever seen orbiting our home galaxy, the Milky Way.  All stars are born in great islands or groupings of stars called galaxies.

Big galaxies like the Milky Way are surrounded by smaller “baby galaxies” (or satellite galaxies), some of which collide with it over cosmic times.  About 50 such galaxies are currently known to orbit our Milky Way – with the two “Magellanic Clouds” (discovered by Ferdinand Magellan’s crew) being the most famous of them.

Because many of the smallest galaxies are very faint, they are hard for us to make out.  Remember, we are inside the Milky Way, and so (as we try to look outwards) we always have to observe through the stars and star clusters of our own galaxy.  The faint baby galaxies can be hard to tell apart from clusters or groups of stars in the Milky Way itself. (This is why it’s hard to get a good photo of the Milky Way; we are inside it and so it’s like trying to take a selfie from inside your kidney.  The view is not so clear.)

Still, using the giant Subaru telescope (whose mirror is more than 24 feet wide), the team was able to find the faintest baby galaxy ever found, which is being called Virgo I (since we see it in the constellation of Virgo.)  At an estimated distance of 280,000 lightyears from us, Virgo I was much fainter than earlier surveys for our neighbor galaxies were able to reveal.

The whole Virgo I “dwarf galaxy” is only about 248 lightyears wide.  Compare that to the 100,000 lightyear diameter of the Milky Way! The Magellanic Clouds are estimated to be 7,000 and 14,000 light across.  So you can see that Virgo I really is just a baby. See the tiny smudge it makes on our accompanying image.

But if one such baby galaxy has escaped our notice until now, chances are many others like it may also be out there.  Some of our theories predict that major galaxies like the Milky Way should be surrounded by many more dwarf galaxies that we have seen so far.  Virgo I leads astronomers to think that more may be out there -- just waiting for bigger telescopes and more observations before they are discovered. 


Thursday, November 10, 2016

Enjoy Sunday and Monday's "Supermoon" But Don't Fall for the Hype!


You may read stories in the media about Sunday evening’s or Monday morning’s full moon being a “supermoon.” And it is true that – by a slight amount – the full moon just before Monday’s sunrise will be the closest, brightest, and largest-looking full moon since 1948.
But the average person won’t notice much difference between this “supermoon” and an ordinary full moon. Clouds, smog, and human lights turn out to have a much greater effect on how bright a full moon looks to us. Still, if you look carefully under dark skies, you might convince yourself that the full Moon Sunday night and Monday before dawn looks a bit bigger and brighter than usual.
“Supermoon” is not an astronomical term. It was suggested by an astrologer and suddenly became popular in the media (who always favor superlatives) in 2011. We astronomers have been stuck with it ever since.
Why are some full moons bigger and brighter than others? It’s because the Moon’s orbit around us is not a perfect circle, but on oval shape called an ellipse. That means sometimes the Moon is a bit closer to us and sometimes it’s a bit further away. If a full moon happens just when the Moon is closer, we get a bigger and brighter looking full moon. The more precisely the closest moon and the full moon coincide, the better the super effect. Nov. 14th, the moon is full at 5:52 am Pacific time, while the moon is closest at 3:23 am. That’s a pretty close coincidence.
Does the “supermoon” have any significant effect on planet Earth. You may read predictions that there will be much greater tides or even earthquakes Monday morning. Don’t believe it! We have slightly stronger tides every time the Sun, Earth and Moon are lined up (which they are at every full moon). But the only time the supermoon will show itself in a significantly stronger effect on the shore is if we happen to be in the middle of a huge storm. And the Sun and Moon have no effect on earthquakes, which happen deep inside the Earth.
So if you happen to glance at the full Moon Sunday evening or Monday morning, enjoy the knowledge that the Moon is a bit closer to you. You may even howl at the Moon if the candidate of your choice didn’t get chosen in our recent elections. But don’t add the “supermoon” to your list of things worth worrying about.

(Photo of the Lick Observatory with the Moon behind it by Rick Baldridge of the Peninsula Astronomical Society.  This was taken with a special lens to enlarge both the observatory and the Moon.)

Sunday, October 23, 2016

Water Worlds in the Solar System


There is new evidence for the existence of liquid water in the cold outer regions of our solar system. Astronomers using the Hubble Telescope see plumes of water erupting from the surface of Jupiter’s moon Europa, and measurements of Saturn’s little moon Dione indicate that it must have a substantial layer of liquid water deep underground.
In recent years, more and more evidence has accumulated that liquid water exists among the moons of the giant planets. We have known for a while that there is likely to be an underground ocean of water beneath the icy crust of Jupiter’s moon Europa, and perhaps also under the surface of its moon Ganymede (the largest moon in the solar system.)
Then the Cassini mission found great geysers of salt water emerging from the icy cracks on Saturn’s moon Enceladus, a world much smaller than the Jupiter moons we just discussed. The big deal here is not that there is water, since water ice makes up a large part of many of the solid worlds in the outer solar system. The big discovery is that, even in those icy realms, enough heat can be generated inside these moons to have oceans of liquid water.

The Hubble work is the second report of plumes coming out of cracks in the ice of Europa. Earlier work, also done with the Hubble, also hinted at such plumes, but now astronomers have observed them in ultraviolet light as Europa was crossing the face of Jupiter. Our top image shows you what was observed, with a visible-light picture of Europa photoshopped in to show you what the moon looks like. A short NASA movie explaining the discovery can be seen at:
https://www.youtube.com/watch?v=4QJS9LcB66g
The work on Dione was more indirect. This moon of Saturn’s is about 700 mi across, more than twice as big as Enceladus. The presence of water was suggested by measurement of the gravity of Dione, as the Cassini spacecraft flew by it. The gravity measurements fit with the presence of a water layer deep inside the moon, perhaps 60 mi beneath the surface.
(The bottom image shows a very detailed image of Dione's surface from the Cassini spacecraft.  You see many icy cracks and fractures, whose sides show as white cliffs.)
Something must heat the buried “oceans” in these moons to keep them liquid. In some cases, it is a tug of war between the gravity of the mother planet on one side, and a large moon on the other. Or it may be some kind of rocking back and forth, which scientists call “libration”. Whatever allows liquid water layers to exist out there, the fact that they do makes them an interesting place to look for the beginnings of life.

Water Worlds in the Solar System


There is new evidence for the existence of liquid water in the cold outer regions of our solar system. Astronomers using the Hubble Telescope see a plume of water erupting from the surface of Jupiter’s moon Europa, and measurements of Saturn’s little moon Dione indicate that it must have a substantial layer of liquid water deep underground.
In recent years, more and more evidence has accumulated that liquid water exists among the moons of the giant planets. We have known for a while that there is likely to be an underground ocean of water beneath the icy crust of Jupiter’s moon Europa, and perhaps also under the surface of its moon Ganymede (the largest moon in the solar system.)

Then the Cassini mission found great geysers of salt water emerging from the icy cracks on Saturn’s moon Enceladus, a world much smaller than the Jupiter moons we just discussed. The big deal here is not that there is water, since water ice makes up a large part of many of the solid worlds in the outer solar system. The big discovery is that, even in those icy realms, enough heat can be generated inside these moons to have oceans of liquid water.
The Hubble work is the second report of plumes coming out of cracks in the ice of Europa. Earlier work, also done with the Hubble, also hinted at such plumes, but now astronomers have observed them in ultraviolet light as Europa was crossing the face of Jupiter. Our top image shows you what was observed, with a visible-light picture of Europa photoshopped in to show you what the moon looks like. A short NASA movie explaining the discovery can be seen at:
https://www.youtube.com/watch?v=4QJS9LcB66g
The work on Dione was more indirect. This moon of Saturn’s is about 700 mi across, more than twice as big as Enceladus. The presence of water was suggested by measurement of the gravity of Dione, as the Cassini spacecraft flew by it. The gravity measurements fit with the presence of a water layer deep inside the moon, perhaps 60 mi beneath the surface.
(The bottom image shows a very detailed image of Dione's surface from the Cassini spacecraft.  You see many icy cracks and fractures, whose sides show as white cliffs.)
Something must heat the buried “oceans” in these moons to keep them liquid. In some cases, it is a tug of war between the gravity of the mother planet on one side, and a large moon on the other. Or it may be some kind of rocking back and forth, which scientists call “libration”. Whatever allows liquid water layers to exist out there, the fact that they do makes them an interesting place to look for the beginnings of life.