An artist's conception of two tidally locked objects orbiting the Sun from afar. The system: 2010 WG9 may likely look like this. Credit: zmescience
An artist's conception of two tidally locked objects orbiting the Sun from afar. The system: 2010 WG9 may likely look like this. Credit: zmescience

Solar System

Mysterious and Well-Preserved Oort Cloud Object Heading Into Our Solar System

28 May , 2013 by

What if we could journey to the outer edge of the Solar System – beyond the familiar rocky planets and the gas giants, past the orbits of asteroids and comets – one thousand times further still – to the spherical shell of icy particles that enshrouds the Solar System. This shell, more commonly known as the Oort cloud, is believed to be a remnant of the early Solar System.

Imagine what astronomers could learn about the early Solar System by sending a probe to the Oort cloud! Unfortunately 1-2 light years is more than a little beyond our reach. But we’re not entirely out of luck. 2010 WG9 – a trans-Neptunian object — is actually an Oort Cloud object in disguise. It has been kicked out of its orbit, and is heading closer towards us so we can get an unprecedented look.

But it gets even better! 2010 WG9 won’t get close to the Sun, meaning that its icy surface will remain well-preserved. Dr. David Rabinowitz, lead author of a paper about the ongoing observations of this object told Universe Today, “This is one of the Holy Grails of Planetary Science – to observe an unaltered planetesimal left over from the time of Solar System formation.”

Now you might be thinking: wait, don’t comets come from the Oort Cloud? It’s true; most comets were pulled out of the Oort cloud by a gravitational disturbance. But observing comets is extremely difficult, as they are surrounded by bright clouds of dust and gas. They also come much closer to the Sun, meaning that their ices evaporate and their original surface is not preserved.

So while there is a surprisingly high number of Oort cloud objects hanging out within the inner solar system, we needed to find one that is easy to observe and whose surface is well preserved. 2010 WG9 is just the object for the job! It is not covered by dust or gas, and is believed to have spent most of its lifetime at distances greater than 1000 AU. In fact, it will never approach closer than Uranus.

Astronomers at Yale University have observed 2010 WG9 for over two years, taking images in different filters. Just as coffee filters allow ground coffee to pass through but will block larger coffee beans, astronomical filters allow certain wavelengths of light to pass through, while blocking all others.

Recall that the wavelength of visible light relates to color. The color red, for example, has a wavelength of approximately 650 nm. An object that is very red will therefore be brighter in a filter of this wavelength, as opposed to a filter of, say, 475 nm, or blue. The use of filters allow astronomers to study specific colors of light.

Astronomers observed 2010 WG9 with four filters: B, V, R, and I, also known as blue, visible, red, and infrared wavelengths. What did they see? Variation – a change in color over the course of just days.

The likely source is a patchy surface. Imagine looking at the Earth (pretend there’s no atmosphere) with a blue filter. It would brighten when an ocean came into view, and dim when that ocean left the field of view. There would be a variation in color, dependent on the different elements located on the surface of the planet.

The dwarf planet Pluto has patches of methane ice, which also show up as color variations on its surface. Unlike Pluto, 2010 WG9 is relatively small (100 km in diameter) and cannot hold on to its methane ice. It’s possible that part of the surface is newly exposed after an impact. According to Rabinowitz, astronomers are still unsure what the color variations mean.

Rabinowitz was very keen to explain that 2010 WG9 has an unusually slow rotation. Most trans-Neptunian objects rotate every few hours. 2010 WG9 rotates on the order of 11 days! The best reason for this discrepancy is that it exists in a binary system. If 2010 WG9 is tidally locked to another body — meaning that the spin of each body is locked to the rate of rotation — then 2010 WG9 will be slowed down in its rotation.

According to Rabinowitz, the next step will be to observe 2010 WG9 with larger telescopes — perhaps the Hubble Space Telescope — in order to better measure the color variation. We may even be able to determine if this object is in a binary system after all, and observe the secondary object as well.

Any future observations will help us further understand the Oort cloud. “Very little is known about the Oort cloud – how many objects are in it, what are its dimensions, and how it formed,” Rabinowitz explained.  “By studying the detailed properties of a newly arrived member of the Oort cloud, we may learn about its constituents.”

2010 WG9 will likely hint at the origin of the Solar System in helping us further understand its own origin: the mysterious Oort cloud.

Source: Rabinowitz, et al. AJ, 2013

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By
Shannon Hall is a freelance science journalist. She holds two B.A.'s from Whitman College in physics-astronomy and philosophy, and an M.S. in astronomy from the University of Wyoming. Currently, she is working toward a second M.S. from NYU's Science, Health and Environmental Reporting program. You can follow her on Twitter @ShannonWHall.



51 Responses

  1. Bruce J. Martin says:

    Not sure what reading audience this is written for. Seems like it’s written at about the 6th grade level is several places. (Over)use of exclamation, redundancies, heavy-handed transitions, too many calls to “imagine” (and synonyms).

    • David Theiler says:

      I had to skip the paragraph where wavelength filters were compared to coffee filters. Does the author think her audience is five years old?

      • Tim Q says:

        And if my coffee filters start letting ground coffee get through, it is time for different filters (very poor analogy)

      • Dan Robinson says:

        She also thinks a coffee filter separates the grounds from the whole bean.

        A real editor would have thrown this one back at her with the admonition, “Get it right!”

        • William Sparrow says:

          The author’s bio states that she’s an aspiring science journalist. You may think her writing here is below your acceptable level, but I give her credit for her academic accomplishments thus far. How do yours compare?

    • Nicole Lindell says:

      Elitist much? Not all astronomy or space enthusiasts are college-level readers.

      • William Sparrow says:

        Thank you Nicole, my sentiments exactly.

      • Torbjörn Larsson says:

        FWIW, science and (usually) education is elitist. But not when it comes to public and/or politic outreach et cetera. So yeah, bad call.

    • It is a common misconception that “everyone” is reading on a person’s own subjective knowledge level. This is understandable because the world is seen from that viewpoint. It is, however, misleading. Lots of children are growing up and discovering science every day. We NEED articles that apply to them, the future engineers and astronauts.

      Also, there aren’t enough educated readers online to support the ad revenue for the site to keep it going if only they were coming by.

    • Andres says:

      Simple text is much better to understand if your mother tongue isn’t English!

    • Samantha Takahashi says:

      How incredibly rude. Anybody should be able to get interested in science. Not all people are native English speakers, either. How does your foot taste?

  2. Sam says:

    ‘Imagine looking at the Earth (pretend there’s no atmosphere) with a blue filter. It would brighten when an ocean came into view, and dim when that ocean left the field of view.’ With no atmosphere, the ocean would not be blue, would it?

    • Coacervate says:

      Water is pale blue

    • lincutious says:

      With no atmosphere, there would be no liquid water visible from space, just white ice like Enceladus, with our proximity to the sun and the moisture content of our planet it is doubtful that our gaseous atmosphere would ever ceases to exist.

  3. Diana Lynn Langton says:

    The average reader reads at the 8th grade level.

    • rotarman says:

      I always get the impression that people who quote this believe themselves not to be in that category, as if knowledge of the “fact” automatically makes them literary giants.

  4. DCF Per says:

    Sorry, but I could not finish reading this article. It seems to have been written for children.

  5. As was pointed out earlier. Anything constructive to add?

  6. Mike Petersen says:

    Mommy! Thanks for showing this to me! (says the 8 year old) I want to be an astronomer when I grow up!
    Now you might see why an article written like this can be worthwhile.

  7. Olaf2 says:

    I don’t mind the language. It would be foolish to assume that the UT readers are all higher educated people. Once in a while a topic should be easy explained like this does.

    • ChrisLoos says:

      Even you are still making assumptions :) Higher education does not necessarily mean educated in astronomy. I consider myself highly educated…over educated perhaps. But I still appreciated this article because I’m not an astronomer.

  8. NancyAtkinson says:

    Wow. Anyone care to comment on the exciting science that 2010 WG9 will likely provide? Solar system scientists have got to be ecstatic about this object!

    • Al_Hall says:

      I am.. I hope some day soon there will be pictures. That will be cool…
      I’m fine with the write up. No complaints at all.

    • Aqua4U says:

      Sounds like someone’s drumming up support for a possible mission? or mission enhancement? How about combining the asteroid retrieval mission NASA has proposed with closer obs. of 2010 WG9? Pick an asteroid to retrieve on the same side of the solar system as 2010 WG9 and then take a closer look at 2010 WG9 too?

  9. Jo Ann Smalley-cw Herrman says:

    There is a sci fi book from 2011, The Day Earth Was Visited, which features a spacecraft leaving the Oort Cloud, near our sun’s tenth dwarf planet Eris and headed directly to Earth. The 4 different aliens aboard visit Earth to suggest a way to eliminate terrorism on Earth before it self-destructs. Finally the Oort Cloud is getting the attention it deserves.

    • Basarab says:

      I’ve looked for that book and couldn’t find anything. Could you be less ambiguous about it and tell me some more details, it really sounds interesting.

  10. William Sparrow says:

    I suggest you write to Fraser and submit an example of what you consider appropriate for the readers of this site.

  11. ZempOh says:

    I like the article, the author did a good job of explaining concepts.

    I laugh at those of you who scoff at her ability to explain things in such a simple context — often that is the hardest part of writing or teaching — few are very good at it.

  12. tommy2X6 says:

    I like coffee.

  13. Torbjörn Larsson says:

    Even better, the likewise accessible Triton (around Neptune) makes an outer debris body comparison, Kuiper belt vs Oort cloud, vs size and location. However, Triton is large enough to be among our most geologically active planets*, which presumably is why Rabinowitz is excited about WeeGee’s freshness.

    * For nitpickers: Planet in the differentiation geophysical sense, not orbital astrophysical sense.

  14. Ed Roberts says:

    What strikes me most about this article is how much good information is in there, and how readable it is. I’ve read too many articles aimed at newcomers that are filled with errors; this is a refreshing exception.

    Sure, the coffee filter analogy is flawed, but it does the job. The same readers who might be newly attracted to astronomy–after all, they just read something they could understand without looking up every other word–aren’t going to sit there and try to poke holes in an analogy.

    Assignment: if you don’t like the coffee filter analogy, come up with a better one. It has to be 30 words or under, and based on something equally (or more) familiar to the general public.

    My suggestion is that those of us who may know more about the subject use our own filters and ignore those (very few) phrases or words that express such “unscientific” enthusiasm.

    :-)

  15. Daniel Rodriguez says:

    So, out of curiosity, this object does have the possibility of becoming a comet in the future if it does get pulled in closer by the Sun’s gravity? Or is it already considered a comet that just hasn’t sprouted a coma yet?

  16. Fraser Cain says:

    Figuring out which concepts to explain and which ones you can assume is one of the trickiest parts of science journalism. Those of us with lots of experience have honed this to a precise level, but this was Shannon’s second article with us.

    It takes years to craft an arsenal of perfect science analogies.

    Constructive feedback noted. Insulting feedback ignored.

  17. Ali says:

    So there’s this amazing article about discovery, and all you people talk about is how badly she wrote it and judge her level of writing skills? People of all ages should be able to appreciate this stuff. Kinda shows where the worlds gotten to today. Shut up and appreciate the wonders that surround us.

  18. jcitizen says:

    I can’t understand those that seem to not want to share understanding with those that may be at a different reading level? Isn’t that a science fan’s goal to spread science knowledge among the masses? I especially want children included in this, as that is the future. I became a science fanatic watching my brother build radios, and TV’s Star Trek was another bit motivator – I would have NEVER made it through college calculus without that motivation!!!

    Please continue on good author – we should be more than pleased! :)

  19. John Sheff says:

    So I’m like, wow! How can they spot a 100-meter wide object that’s at least as far as Uranus? I thought that would be far beyond our capabilities. We can barely find objects approaching Earth that are that small. Then I went to the original article, and it’s a 100-KILOMETER wide object. Whew! Big difference!

  20. Danny says:

    I like tea. I also like the java jive, and it likes me.

  21. Gerardo Gutierrez Muñoz says:

    Por favor no llamen a Plutón ” Planeta Enano ” La Categoría de Planeta, ya no le pertenece, Please do not call Pluto “Dwarf Planet” The Planet category, and does not belong,

  22. Hillary Leben says:

    I think the oort cloud probably looks something like this:
    http://www.thehillsite.com/?p=225#respond

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