Archive for the ‘Astronomy’ category

So Is It A Planet?

August 24, 2009

And Why Not???

Pluto From New Horizons

Pluto From New Horizons

From CNN on-line:

It was three years ago Monday that the International Astronomical Union demoted Pluto from a planet to a dwarf planet, a decision that made jaws drop around the world.

An outcry followed, textbooks had to be rewritten, long-held beliefs were shattered, and many people felt our cosmic neighborhood just didn’t seem the same with eight — instead of nine –planets in the solar system.

Well, even though I was working on the New Horizons Mission to Pluto at the time, my jaw didn’t exactly drop. The debate had been going on for awhile. Besides. It’s just nomenclature. As it was, ever since Arthur C. Clarke pointed out that Europa was every bit as interesting as Jupiter, astronomically speaking, many of us had sort of realized early on that there was more to the Solar System than just planets, comets and asteroids.

Not that planets were downgraded, mind you. It was more like everything else was upgraded in importance. The icing on that particular cake was that astronomers began to realize that even the planets were more varied than originally supposed. There weren’t just two kinds; rocky like the Earth and gaseous-giants like Jupiter. It seems better now to recognize that Uranus and Neptune might be yet a third class – with interiors that are much different than the others, and with unique formation-histories to boot. The discovery of large ice-balls in the outer solar system, of which Pluto is  the earliest known (and probably best) example, is merely the last step in that march.

So, planet or no, Pluto is going to be a great place to visit.  Too long a commute to live there, however.

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Enceladus Is All Wet

June 25, 2009

…And Is A Moon of Saturn

Geysers on Enceladus

Geysers on Enceladus

Arrggg! So much news today! But the most interesting (unless you’re a real Michael Jackson fan) is from a paper published in the British journal Nature, by Frank Postberg of the University of Heidelberg.

The Cassini spacecraft has found what may be the strongest evidence yet that Saturn’s tiny moon Enceladus has an ocean beneath its icy surface. If the liquid water finding is confirmed, it would suggest that the moon may be one of the most promising places in the solar system to search for signs of past or present extraterrestrial life.

This is significant.

Tiger Stripes Indicate Organics

Saturns Moon Enceladus

You see, there are three ingredients necessary for life; an energy source, a good mix of organic chemicals (both of which Cassini has found on Enceladus already), and water.  Liquid water.

Researchers in Europe detected salt particles in the volcanic vapour-and-ice jets that shoot hundreds of kilometres (miles) into space, the strongest evidence to date of a liquid ocean under the moon’s icy crust.

If Jupiter’s moon Europa also has oceans below its frozen surface, the number of places in the solar system with the potential to harbor life is starting to look distinctly greater than 1.

Cassini has been circling Saturn since 2004.

Staring At The Sun

June 23, 2009
Not a Flower

Not a Flower

But Not For Too Long

What you see in the picture is not a flower, but a sunspot, close up.  Very close up.  The scale shown on the full size image indicates a bar that spans 10 million meters, or about 6,100 miles.  For comparison, the Earth’s diameter is about 8,000 miles.  What’s causing those flares, filiments and tongues of fire?  Why, magnetic fields, of course.

But you knew that.  You see, at the temperature of the Sun’s surface it’s hot enough (about 5,000 deg. K.) that electrons don’t stay tied to the nucleus of hydrogen (and some helium) very long, and go flying off.  That leaves a lot of naked, electrically charged stuff floating around for magnetic fields to play with, and boy, do they have a good time wallowing in all that plazma.

But that’s not the best part of that photogragh.  From Anne Minard at Universe Today:

In the just-released image above, the interface between a sunspot’s umbra (dark center) and penumbra (lighter outer region) shows a complex structure with narrow, almost horizontal (lighter to white) filaments embedded in a background having a more vertical (darker to black) magnetic field. Farther out, extended patches of horizontal field dominate. For the first time, scientists have modeled this complex structure in a comprehensive 3D computer simulation, giving scientists their first glimpse below the visible surface.

It’s good to know about the inner workings of the Sun, and sunspots are the portal through which we can study the sun’s interior.  Why should we bother?  There are two very good reasons.

Sunspots are the most striking surface manifestations of solar magnetism, and they are associated with massive ejections of charged plasma that can cause geomagnetic storms and disrupt communications and navigational systems. They also contribute to variations in overall solar output, which can affect weather on Earth and exert a subtle (and as-yet deciphered) influence on climate patterns.

A quote from Matthias Rempel, a scientist at NCAR’s High Altitude Observatory:

“If you want to understand all the drivers of Earth’s atmospheric system, you have to understand how sunspots emerge and evolve. Our simulations will advance research into the inner workings of the Sun as well as connections between solar output and Earth’s atmosphere.”

That’s the best reason.

Some Untruths

June 12, 2009

Things We Thought Were True, But Are Not

When I was learning this stuff, I was told that:

  • Astronomers would never see planets circling other stars
  • We can see almost to the end of the universe and almost count everything that’s there
  • The universe will stop expanding one day, and may even start to contract
  • You’ve been as constant as the Northern Star, the brightest star that shines

Oh wait – that last one is from a song by Gerry Rafferty.  It’s as wrong as all the other things in the list, though (Polaris, the “Northern Star”, is neither the brightest star, nor is it constant in brightness).

The latest bit of knowledge circa 1960 that’s gone “poof!” is the idea that the Earth’s atmosphere is pretty solidly connect to the planet, and is shielded from solar storms by the Earth’s magnetic field.  These storms and the solar wind would otherwise drive the atmosphere off the planet.  But unlike Mars, the air is not leaking away.

Oh yeah?

This may mean our planet’s magnetic shield may not be as solid a protective screen as once believed when it comes to guarding the atmosphere from an assault from the sun.

Researchers were stunned to discover recently that Earth is losing more of its atmosphere than Venus and Mars, which have negligible magnetic fields.

Once again, it’s the end of the world as we know it, and I still feel fine.

Hubble Repair Mission Launch

May 11, 2009

Monday, May 11, 2009, 2:01 EDT

This will be the 5th and final Hubble repair mission.

With two non-functioning cameras, the orbiting telescope is all but blind now.  NASA engineers readily admit that they’re going for broke with this ambitious mission, which will replace those cameras and upgrade a host of other sub-systems on the 19 year old observatory. Says Tariq Malik at Space.com:

If all goes well, the astronauts will leave Hubble’s vision and science capability more powerful than ever before by the end of the 11-day mission. Atlantis is also carrying a set of IMAX 3-D cameras to document Hubble’s last service call for a film slated to be released in spring 2010.

To see live coverage on your PC, go here for information or here for a live feed.

HST was designed to last a minimum of 15 years in space, but it was hoped that with well timed servicing missions it would be up there for 25. With this mission, the telescope should easily be able to last that long. Getting to this point has been sometimes problematic.

NASA canceled an Atlantis mission to extend Hubble’s operational life in January 2004 because the trip was considered too risky in the wake of the 2003 Columbia tragedy that killed seven astronauts. But public pressure and the development of safer shuttle technology led the U.S. space agency to reconsider.

As I type this, the weather report for launch could not be better.

Moon Shadow

April 13, 2009

And Cat Stevens

Credit - Cassini / NASA

Credit - Cassini / NASA

Emily at Planetary.org has a wonderful post about some shadow-play that’s occurring right now on Saturn’s rings.  You see, the rings are quickly becoming “edge-on” to the Sun, as they do twice every Saturnian year (which is about 30 Earth years).  Right now, shadows caused by the moons of Saturn that happen to fall on the ring system are very long, as you can see by the spike shaped shadow cast by Mimas in the photograph.

But that’s not the cool part. That would be the jagged, “grassy” edge that you can see above (and mostly to the left of) the spike (click on the thumbnail to enlarge it).  What’s that caused by? Why, something much smaller, clearly.

Emily does some quick “back of the envelope” calculations right there in her blog (she’s a pro., so please don’t try this at home without a trained mathematician nearby!) to show that whatever is causing that jagged line effect is only about 3 km. high.

But Cassini has already spotted moons around the planet that are about that size, and whatever is causing this doesn’t look like a moon to Cassini.  So are they many small moons – hundreds of them?  Not exactly, probably.

I believe that what we’re actually seeing is clumpiness of particles at the outer edge of the densest B ring, where particles bunch together partially by self-gravity (which would make them more like moons) but also by the periodic gravitational shoves they get from Mimas. At least that’s what the imaging team has said about past images of the outer edge of the B ring, like this one. These clumps would be transient, torn apart by the same forces that bring them together. The B ring is so dense that particles rub up against each other as they orbit Saturn — an astronaut would be able to travel easily from one particle to the next, clambering around the rings, though it’d be a long trip to circle Saturn! And, evidently, the astronaut would have some climbing to do, traveling up and down the clumps of big particles that form the B ring’s outer edge.

Now that’s cool!

Here’s more from Nancy Atkinson at Universe today.

Because Saturn is approaching its equinox, in August the rings will “disappear” from our view from Earth, as the rings will be exactly edge-on. But as the rings ease into alignment with the sun, Saturn’s moons cast their shadows across the rings, growing longer as equinox approaches. See in the image above, a shadow is cast on the rings[.]

What’s Up On Jupiter?

March 14, 2009

It’s Big, And It’s Climate Is Changing

090309-mm-jupiterspot-01Jupiter’s Great Red Spot has been there a long time.  Galileo first spotted it in 1610, and it’s been watched ever since.  But it’s not constant and unchanging.  We’ve known and observed small changes in in it’s size and color, and assumed that these changes reflect changes in it’s chemical composition.  But for the first time, The Great Red Spot seems to be shrinking, and other storms on Jupiter are merging to rival – or at least threaten – its status as the largest storm in the Solar System.  Earlier this week, Space.com gave us this:

On Earth, hurricanes form and dissipate in a matter of days. On Jupiter, storms can rage for years or even centuries. The Great Red Spot, a colossal storm twice the diameter of our planet, has lasted at least 300 years.

But now that mother of all storms is shrinking just as other spots emerge to challenge its status.

Observations of cloud cover over the past decade or so have suggested the huge, oval tempest was getting smaller as Jupiter’s climate changes.

Climate change?  Most assuredly.  Climates do that.  Jupiter’s Great Red Spot is not going to disappear tomorrow, but it is changing.  And change on a planetary scale is always “interesting”.  This may have something to do with the merging of 3 white “ovals” on Jupiter a few years ago.  Philip Marcus, a professor at the University of California, Berkeley is an expert in fluid and atmospheric dynamics, and decided that he has a good way to understand Jupiter’s changes.

“We think that upheavals might be related to the way that vortices move heat around the planet — when there are many vortices, they are very efficient at moving heat all the way from the equator to the poles,” Asay-Davis explained. “But when there are fewer, they are likely to be much less efficient.”

Back in 1998 to 2000, three large storms, all white ovals, merged. That might have had a big impact on the entire planet’s climate.