Friday, April 16, 2010

Hubble's images of dwarf planet [?] Pluto

Is it accepted now? Is this logical? Dwarf planet expert studies and comments on Pluto, thus Pluto is a "dwarf planet". Warped logic of course. Here is the latest from NASA.


April 16, 2010: Lonely Pluto floats in the darkness at the edge of our solar system. It's so far away even the Hubble Space Telescope has trouble making out the details. Nevertheless, Pluto is so interesting, even fuzzy images of the dwarf planet are compelling.

A team of researchers led by Marc Buie of the Southwest Research Institute recently released the best Hubble images to date:

The data reveal an icy molasses-colored world with a surprising amount of activity. Buie compared Hubble images taken in 1994 vs. 2003 and discovered that Pluto's northern hemisphere has brightened while the southern hemisphere has dimmed. Ground-based observations suggest that Pluto's atmosphere doubled in mass during approximately the same time period. And no one is certain what's causing the molasses-colored splotches on Pluto's surface.

"It's baffling," says dwarf planet expert Mike Brown of Caltech. "For now, we can only guess. Although these images are the best we have to date, they just aren't clear enough to answer all the questions they raise."

For instance, what's happening to Pluto's atmosphere?

Pluto can get so cold, researchers believe, that its atmosphere can actually freeze and fall to the ground. If Earth's atmosphere did that, it would make a layer 30 feet thick, but Pluto has less to work with. When it’s on the ground, Pluto's entire blanket of air is no more than a frosty film of nitrogen and methane.

"Until the mid-1980s, Pluto's northern hemisphere was tilted away from the sun for over 100 years, accumulating a substantial amount of frost," says Buie. "Now the northern hemisphere is coming into sunlight and appears, as shown in the Hubble images, to have been growing brighter."

The atmosphere might also be changing in response to Pluto's highly eccentric orbit. During the late 1980s, Pluto approached as close to the sun as it ever gets (about 2 1/2 billion miles) and gradually started warming. Now the temperature on Pluto is up to a balmy -385 degrees Fahrenheit! Surface frosts exposed to such "warmth" may be subliming—that is, changing back into a gas.

"Pluto, right now, has the best atmosphere it's had in our lifetime," says Brown.

And about that molasses…

Researchers think these dark areas may be primordial organic matter.

"We know there's methane on Pluto," says Brown. "Here's what we think happens: Sunlight hits the methane and breaks it apart into its chemical components -- hydrocarbons. Over millions of years this process makes a dark reddish-brown oil or tar like substance that sticks to the ground. These darker areas spread larger as they absorb more sunlight and cause additional frost to sublimate."

"Now, Pluto is headed away from the sun again," says Brown. "It will gradually get colder and colder and its atmosphere will refreeze to its surface. In fact, that should have already started happening, but apparently it has not. It's a mystery."

NASA's New Horizons probe is en route to investigate. The spacecraft left Earth in January 2006 and has been racing toward Pluto for an encounter in July 2015, hopefully before the atmosphere refreezes.

"New Horizons will map the entire sunlit portion of Pluto," says Buie. "And as it swings closer, it will get very detailed images, maybe as good as 50-100 meter resolution."

"This will allow us to explore some of the interesting areas we've pinpointed," he continues. "For example, the recent Hubble images reveal a very bright spot – brighter than anything else on Pluto – near the equator. And just to the left of that bright spot is some of the darkest terrain on Pluto's surface. We want to examine the area where these bright and dark areas are touching and figure out what's causing the differences. This is a good target because it includes every kind of terrain Pluto has to offer."

"We know there are surprises waiting for us on Pluto," says Brown.


Laurel Kornfeld said...

I would like to see some comments from New Horizons Principal Investigator Dr. Alan Stern. He is the person who originally coined the term "dwarf planet," but he never intended dwarf planets to not be considered planets at all. Interestingly, in astronomy, dwarf stars are still stars, and dwarf galaxies are still galaxies.

As a dynamic world with geology and weather, Pluto shows it has more in common with the other, bigger planets than it does with most Kuiper Belt Objects except the few large ones, which should be considered planets too. Most KBOs in Pluto’s orbital path are tiny and do not have these features. These images show that before making definitive classifications, we should first get the data and analyze it; otherwise, we are defining objects without knowing significant factors about them.

Mercury said...

Hello Laurel:

Re: Alan Stern..."He is the person who originally coined the term "dwarf planet," but he never intended dwarf planets to not be considered planets at all. Interestingly...." I don't doubt your statement, but you know, I cannot find any source that supports the claim. Would you provide some direct evidence. Furthermore, Stern was quite upset with the IAU and stated "It's an awful definition; it's sloppy science and it would never pass peer review - for two reasons. Firstly, it is impossible and contrived to put a dividing line between dwarf planets and planets. It's as if we declared people not people for some arbitrary reason, like 'they tend to live in groups'. Secondly, the actual definition is even worse, because it's inconsistent." That makes sense...after all, Stern is the spearhead of New Horizons and it would not be proper for him to minimize Pluto's status.

"As a dynamic world with geology and weather, Pluto shows it has more in common with the other, bigger planets than it does with most Kuiper Belt Objects except the few large ones, which should be considered planets too." This is do not want to remove Pluto from our solar system list, but are willing to add a few more?

Pluto T-shirt is in the mail. :)

Laurel Kornfeld said...

You're going to have to give me time to search for the 2000 study in which Stern and Levison distinguished two classes of "uber planets" and "unter planets," which he equated to classical planets and dwarf planets--but never claimed dwarf planets are not planets. Unfortunately, I've been through a few hard drives and have lost information that I didn't back up, which I now have to find all over again (most recent hard drive crash was on March 3 of this year).

I do know that Stern objected to the idea of classifying an object only by where it is while ignoring what it is. The IAU definition ends up doing that because the further an object is from the Sun, the larger an orbit it will have to clear. He said Levison did the calculations and determined that if put in Pluto's orbit, Earth would not clear that orbit either.

I think Stern's objection to the IAU decision is less about New Horizons and more about his experience as a planetary scientist. After all, New Horizons is already fully funded and launched. Dawn did not suffer any funding crisis because it was sent to two objects designated as asteroids. We have had missions to comets as well. My understanding is that Stern's position is based on his concept of what compositionally makes an object a planet.

I am happy to add many more planets, as is Stern. In fact, he believes the majority of planets are of the small kind like Pluto and Eris. They are simply a third class of planet. Many people wrongly think that opposition to the IAU definition is about personal favoritism over Pluto. It is not. It comes from the position that a planet is a non-self-luminous spheroidal body orbiting a star. In other words, if a body is in hydrostatic equilibrium and directly orbits the Sun, it is a planet in our solar system. If that gives us 50 or 100 planets, so be it.

I will work on finding the appopriate links regarding Stern and dwarf planets. I am currently taking an astronomy class, and I have my second cold in three weeks, so I am a bit overwhelmed right now.

Mercury said...

"...that gives us 50 or 100 planets, so be it." YIPES! School kids will go crazy. Science fair exhibitions will need more space.

Only those that promote Pluto as a planet acquire a succession of "colds". :)

Timothy said...

any chance i could buy one to name after me....naw...i would lose it in the next divorce

Laurel Kornfeld said...

"Only those that promote Pluto as a planet acquire a succession of 'colds'?"

Is the IAU engaging in biological warfare now??? :)

In this article by Alan Boyle, Stern notes his coining of the term "dwarf planet" back in 1991:

Stern and Levison differentiate between "uber planets," which gravitationally dominate their orbits plus are in hydrostatic equilibrium and orbit stars, and "unter planets," which do not gravitationally dominate their orbits but are in hydrostatic equilibrium and orbit stars, in the following article: Stern, S. A., Levison, H. F., 2000. Regarding the Criteria for Planethood and Proposed Planetary Classification Scheme. Transactions of IAU.

In this article they distinguish between "uber planets" and "unter planets" but never say that "unter planets" are not planets at all.

I don't see why having 50 or 100 planets in our solar system is a problem. Memorizing a list and number of planets (or anything) is of questionable educational value. Kids aren't asked to memorize the names of all the world's rivers or of all of Jupiter's moons. Why not instead teach them the different categories of planets and the characteristics of each category? Science fair exhibitions on the solar system could focus on the many types of planets, such as terrestrials, gas giants, ice giants, dwarf planets, hot Jupiters, super Earths, etc. With new and diverse exoplanets being discovered every day, it is only a matter of time before we become accustomed to a world with as many planets as stars.

Timothy said...

well i see Laurel's point that we teach the many different classes of planets...certainly as our knowledge of solar system expands we are no doubt going to accrue knowledge of many different basic planet constructions....and i am willingly confident on that bet. seems to me a better pursuit than a silly argument over whether it is a least for now but considering human disputation....let us hope it continues

Mercury said...

The IAU vote was unanimous. :)

"Memorizing a list and number of planets (or anything) is of questionable educational value." Well, maybe. Can you name the primary colors of the visible spectrum..."ROY G. BIV"? Maybe the elements of the Periodic Table? Or, perhaps, a list of the brightest magnitude of stars? But then, you do have a good point in the classification of planets. I just appears awkward for this senior.

As I have said before, in regards to Pluto, the common lore is just as valid as the scientific terminology in astronomy and not mutually exclusive.

I probably have some disconnect issue with Stern in that at the website there were numerous documents listed but not available and no answer was given upon an inquiry. After all, NASA and all government funded projects have public access. Why list documents if they cannot be made public.