Exoplanets Are Planets Too!

My first reaction was, “Oh no, not again!” I always maintained Pluto was a “planet,” no matter how the IAU redefined it in 2006. Are we going to revive that old trope again?

In the August 2013 Sky and Telescope, in an article of the same name, veteran writer David Grinspoon does just that, but with a new twist. “Recent discoveries have exposed the absurdity of the IAU’s planet definition.”

Well, of course! How did we miss the obvious? With recent discoveries of huge numbers of planets orbiting other suns, we are calling them “planets.” We can’t call them “dwarf planets” because those will be too small for current detection methods for quite some time to come.

But according to the IAU definition, the very first requirement of a celestial body be that it “(a) is in orbit around the sun.”

What the hell were they thinking?

An engineer, a physicist, and a mathematician are shown a pasture with a herd of sheep, and told to put them inside the smallest possible amount of fence. The engineer is first. He herds the sheep into a circle and then puts the fence around them, declaring, “A circle will use the least fence for a given area, so this is the best solution.” The physicist is next. She creates a circular fence of infinite radius around the sheep, and then draws the fence tight around the herd, declaring, “This will give the smallest circular fence around the herd.” The mathematician is last. After giving the problem a little thought, he puts a small fence around himself and then declares, “I define myself to be on the outside!”

Even this WordPress blog post is a wolf in sheep’s clothing, if you’ll pardon the terrible metaphor. Defining something so that it meets a predetermined selection criteria you need it to match is an ancient malady, and it’s not confined to religion and politics.

1,257 total views, no views today

Iron Oxide on Mars

If Mars has all that rust, where did the oxygen come from? We call Mars the “Red Planet” because it has iron oxide – LOTS of it. Where did it come from? Scientists believe both Earth and Mars got most of its surface iron oxides from meteor bombardment about 4 billion years ago. Why does Mars have so much more of it?

BBC has done interesting documentaries on stromatolites, large living bacterial beach “rock” formations we can still see and investigate in Australia. According to this theory, these cyanobacteria use a primitive photosynthesis to generate Earth’s earliest oxygen. This started oxidizing particulate meteorite iron dust suspended in the oceans, converting it to rust, which settled to the ocean bed and was sequestered there. When free iron particles were essentially used up, oxygen could then start accumulating in our atmosphere … paving the way for higher Earth life forms.

Mars seems once to have had copious water. Could it have also had cyanobacteria? Is that how Mars got all its iron oxide?

Well, according to another theory I found on starryskies.com, Martian oceans simply rusted all that meteoric iron away. Of course, if this is the full explanation, we don’t need the stromatolite theory at all to account for iron oxides on either planet.

I found a third theory on BioEd Online. It suggests the answer is not that simple. Researchers have been able to show that Earth’s powerful gravitational field generates enough pressure and heat to melt iron oxide, in effect smelting oxygen out of it, and allowing it to sink into the molten core. Theoretical calculations show smaller Mars could not have generated the required compressional pressures. This would account for Earth’s huge liquid iron core and the powerful dynamo generating our planet’s magnetic field, in turn protecting our atmosphere from the solar radiation that we expect blasted most of the unprotected Martian atmosphere away.

If all goes well, our new robotic explorer Curiosity will safely descend to the Martian surface at 1:31 a.m. Monday Aug. 6 EDT (0531 GMT) – about 10:30PM Sunday night, Pacific time. Facebook has a Curiosity page, and NASA/JPL will have a “live” feed on UStream’s Curiosity Cam. Curiosity will not broadcast photos until it finishes all its own internal checks. The first photos will be black and white, with color plates following on later transmissions.  Remember, there’s currently a 14 minute radio signal delay between Mars and Earth.

I plan to try to stay up to see if the mission is successful. As for our iron oxide questions, it often turns out in science there is not just one “right” contributory answer. It will be interesting to see what mysteries Curiosity can solve.

3,503 total views, 5 views today

Will Earth Perish by Fire, Ice or Black Hole?

On last night’s news, veteran PBS news anchor Gwen Ifill interviewed a prominent astronomer to solicit comment on the recent discovery of two enormous black holes hiding in the bright central bulges of the giant elliptical galaxies NGC 3842 and NGC 4889.

The scientific news itself went “viral,” being picked up on BBC, The New York Times, Huffington and elsewhere that I can recall, as well as in the scientific journals. The Sky & Telescope article is much more oriented toward readers who are already familiar with cosmological objects and distances. It can be picked up at this link.

You can also read the PBS transcript of Ifill’s interview with Chung-Pei Ma. Ma is professor of astronomy at the University of California, Berkeley. She appeared visibly constrained by the problem of how to explain these concepts to a general viewing television audience.

But the item here concerns Gwen’s question to Chung-Pei Ma. Presumably Gwen had done her homework and knew the answer, but most viewers might not:

[quote]GWEN IFILL: Nearby, but not a threat? I mean, we’re not — you’re talking about black holes that suck in light and gases and everything in its path, but we’re not in its path?”[/quote]

Ma tried to explain, in lay terms, why not. Breaking this question apart, the salient components of a better answer would be:

  • how far out do the effects of these monster black holes reach?
  • how far away are we now?
  • how long in years could an approach to within their spheres of gravitational influence take?

Facts:

  • Both galaxies in question are about 300 million light years away.
  • “For NGC 3842’s central monster, the team found a mass between 7 and 13 billion Suns; for NGC 4889 the range is much bigger: 6 to 37 billion solar masses” [Sky & Telescope].
  •  In other words, each black hole’s estimated bulk suggested it had already swallowed the mass equivalent of an entire “ordinary” galaxy.
  • The “event horizon” of each black hole – the boundary inside of which even light cannot escape the black hole’s unimaginable gravitational field – is estimated at around 3 to 5 solar system diameters.
  • Our Solar System has a diameter of about 0.001 light year. To put this into some kind of perspective, our Milky Way galaxy has a diameter of about 100,000 light years.

Discussion:

  • So, our Milky Way (which has a large black hole of its own) is about 3,000 Milky Way diameters away from NGC 3842 and NGC 4889.
  • Looking at the second illustration in the Sky & Telescope article, and the companion text, it appears that only the the motion of stars within 1,000 light years of their black holes NGC 3842 and NGC 4889 are affected by the nearby dark monsters.
  • We are 300,000 times further way than that.

Devil’s Advocate:

But … but … supposing some cataclysmic upheaval were to propel our solar system, or our planet, toward those monster black holes? How long might it take for them to tear us apart? How fast could an “object” like us move in that direction?

Obviously, we’d have to move really fast.

  • Let’s disregard the fact that any catastrophic event powerful enough to do that would also undoubtedly shred Earth to dust, if not elemental gases.
  • A supernova explosion of our Sun might propel an expanding sphere of gases and dust outward at 11 million miles an hour, though it’s a fact our Sun is way too small to go supernova.
  • According to a Stanford article  “THE MYSTERY OF THE FASTEST MOVING STAR STILL PUZZLING,” they mention a candidate speed in this question: “How do you accelerate 2.7 octillion tons (27 followed by 26 zeros) from a standstill to over 1,800 kilometers per second, about one- half of one percent of the speed of light? That could be as fast as 4 million miles per hour.”

So, even at the catastrophic speed of one percent of the speed of light (give or take), hurtling straight toward either of those two monster black holes, it would take us something like 30,000 million years to reach a destination 300 million light years distant. The universe is currently 13.7 billion years old. Cosmologists think it might be good for another 10 or 20 billion years or so before perishing in fire, or ice, or whatever.

In short: since 30,000 million years is 30 billion years, the universe may not even exist by the time a battered Earth arrives at NGC 3842 and NGC 4889 at the improbably high speed of only one percent of the speed of light. Any slower than that, we’d never arrive, nor would there be any destination to arrive to. I don’t think we have to worry about it too much.

1,125 total views, no views today

NASA: Bright Are Saturn’s Moons

If you don’t already know about NASA’s Image of the Day program, you can follow the link below to their page and add your email app or social media to their RSS feed through the page’s Connect tab.

You can download stunning images daily in a choice of image sizes.

Below: “The Cassini spacecraft observed three of Saturn’s moons set against the darkened night side of the planet in this image from April 2011.” NASA. Pictured are Rhea, Enceladus and Dione.

link: view here

1,306 total views, no views today

Pluto, Once and Future Planet

“I can’t find Pluto anywhere!” – words of a grade-schooler at Hayden Planetarium.

History Channel ran an interesting Pluto retrospective last night. Dr. Neil deGrasse Tyson is a frequent science and astrophysics master of ceremonies on TV science shows, and director of Manhattan’s Hayden Planetarium, among other accomplishments. Dr. Tyson gained popular notoriety by supporting demotion of Pluto to “dwarf planet” status (2006), and, as planetarium director, being one of the first to remove the 9th “planet” from the gargantuan solar system exhibit. Continue reading

1,119 total views, no views today

Summer Solstice

DSC_1844.jpg Potsam and Jetsam ... Click image for larger file.

This photo was taken June 20, 2006. I got around to posting it in Photos that August. It’s not that bad for a photo, and even though the light is interesting, it’s not the kind of photo I normally post to a gallery. I knew there was something special about it, but I couldn’t quite put my finger on it.

I should have asked Astronomy Mag’s Bob Berman, author of the Strange Universe column. Continue reading

501 total views, no views today

Pluto – Enough Already

There’s rebellion in the ranks of amateur astronomy. Despite the IAU’s notorious demotion of Pluto in 2006, many refuse to accept the validity of their new definition. OK, when Clyde Tombaugh discovered Pluto in 1930, if he’d known what we know today about dwarf planet objects, perhaps we’d all be calling the ninth planet a “dwarf planet”. But we didn’t know anything about Eris, Quaoar or other near-planetary objects back then, and you don’t define a new class of objects based on knowledge of only one instance.

Dwarf Planets

Dwarf Planets - click image for website link

IAU Definition:

What constitutes a planet? The International Astronomical Union (IAU) developed some definitions in 2001, modified them again in 2003, and as of August 24, 2006, the IAU has come up with another definition. The IAU said in a statement that the definition for a planet is now officially known as “a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape and (c) has cleared the neighborhood around its orbit.”

Continue reading

1,140 total views, 2 views today

25 hour day = More Sleep

900 million years ago, according to the June Astronomy magazine, Earth’s day was only about 18 hours long. Our planet’s rotation has slowed since then due to the tidal drag or friction of the oceans as the Moon pulls. Due to the law of conservation of (angular) momentum, this also resulted in the Moon gradually increasing its orbital distance from Earth.

Doesn’t everybody occasionally yearn for that extra hour of sleep in the morning? Getting up for work 900 million years ago would have been a real drag, especially since coffee hadn’t been invented yet. The really good news is that, if we’ve gained 6 hours a day in the last 900 million years, then, assuming the process is linear, we’ll have 25-hour days in only another 150 million years. And that means we’ll finally be able both to sleep in, and get to work on time, for the first time in history.

And if you were thinking of just holding out until that blessed day, I’d recommend extra-heavy duty batteries for your alarm clock.

506 total views, no views today