Surface Feature Found on Haumea

by Paul Gilster on September 17, 2009

I’m sure there are people who can keep things straight in the shifting world of planetary definitions, but given the fact that I’m still not used to Pluto’s demotion, I have to look twice before I write anything on the subject. After checking, then, I confirm that Haumea, the interesting outer system object recently considered as the target of a fast orbiter mission (see this earlier post, and its sequel), is called a ‘dwarf planet.’ Orbiting in the Kuiper Belt, Haumea joins Eris, Pluto and Makemake in this category, the fourth largest dwarf planet now known in the Kuiper Belt. Dwarf planet Ceres is a main-belt asteroid, and thus not, like the others, a KBO as well.

haumea_1

Image: Composite image of computer model frames showing Haumea’s red spot as the dwarf planet rotates. Credit: P. Lacerda .

What’s special about Haumea? Its shape, for one thing. The distant world rotates in 3.9 hours, faster than any other large object in the Solar System. That spin seems to account for Haumea’s unusual ellipsoidal shape, which is itself thought to be the result of an ancient impact. Whatever the case, the ellipsoid measures 2000 kilometers by 1600 by 1000 kilometers, balancing gravitational and rotational accelerations.

And now we have new information: Haumea has a spot. The findings were presented by Pedro Lacerda at the European Planetary Science Congress in Potsdam on Wednesday. Lacerda (Queen’s University Belfast) has this to say about the find:

“Our very first measurements of Haumea told us there was a spot on the surface. The two brightness maxima and the two minima of the light curve are not exactly equal, as would be expected from a uniform surface. This indicates the presence of a dark spot on the otherwise bright surface. But Haumea’s light curve has told us more and it was only when we got the infrared data that were we able to begin to understand what the spot might be.”

Further observations planned for 2010 on ESO’s Very Large Telescope should tell us more. Haumea is thought to be covered in water ice, based on spectroscopic observations, but its density (2.5 times that of water) implies that its interior is rocky. The spot is evidently an area richer in minerals and organic compounds than its surroundings. One possibility is that the spot is the scar of an impact, one that left traces of the impactor on the surface of Haumea, possibly mixing with materials from within the dwarf planet. Changes in brightness flagged this area, which is redder in visible light and bluer at infrared wavelengths. I’m thinking the light curve of Haumea must be a thorny thing to untangle, given the speed of rotation and oddball shape.

Two papers cover this discovery. The first is Lacerda et al., “High Precision Photometry of Extreme KBO 2003 EL61,” Astronomical Journal Vol. 135 (May 2008), pp. 1749-1756 (abstract). The second is Lacerda et al., “Time-Resolved Near-Infrared Photometry of Extreme Kuiper Belt Object Haumea,” Astronomical Journal Vol. 137 (February 2009), pp. 3404-3413 (abstract). Look here for links to full text, and also for an interesting animation of these findings.

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James M. Essig September 17, 2009 at 15:04

Hi Paul;

The discovery of this spot is just plain and simply cool.

Given that Haumea seems to have a rocky inner composition, and that its density is about 2.5 times that of water ice, the possibility of manned expeditions to visit this odd minor planet seems highly plausible with craft powered by the VASIMR rocket or other electrical propulsion systems.

I would think that since Haumea is so far from the Sun, the risk of cosmic radiation from the Sun would be greatly reduced for manned surface excursions relative to say a prolonged unshielded stay on the Earth’s moon.

Adam September 17, 2009 at 16:26

Strange little worlds out in the Kuiper Belt. Will be a long search to uncover any traces of ETIs that might have been deposited over the aeons.

Mark September 17, 2009 at 19:04

It resembles nothing less than a huge cosmic eyeball.
Flashes me right back to an Alan Parsons Project song from the 1980′s…

I am the eye in the sky
Looking at you
I can read your mind

Duncan Ivry September 19, 2009 at 11:01

James M. Essig: “… since Haumea is so far from the Sun, the risk of cosmic radiation from the Sun would be greatly reduced for manned surface excursions …”

… and the risk of cosmic radiation from outside of the solar system would be greatly enlarged.

James M. Essig September 19, 2009 at 14:34

Hi Duncan;

I hear that the interstellar cosmic radiation is much less severe in interstellar space than that posed by the sun for astronuats at a distance of 1 AU from the sun. If you can definatively prove your point with quantitaive analysis or data, I will be inclined to agree with you, other wise I have stated my opinion which most likely will not change. Many papers come out against the possibility of manned interstellar space travel, but just as many or more come out in favor of it.

Regardless, adequate shielding can remedy any hazards posed by interstellar cosmic rays.

Administrator September 19, 2009 at 18:13

Jim, I’ve always heard that the heliosphere provides a protective shield against at least a large portion of galactic cosmic rays. We’ll know more when we get a true interstellar mission into the nearby medium. But presumably a KBO moving outside 100 AU or so would receive much more of this flux. Dana Andrews gets into the galactic cosmic ray question in an interesting post that I write about here:

http://www.centauri-dreams.org/?p=5994

James M. Essig September 21, 2009 at 14:31

Hi Paul and Duncan;

Thanks for the info and insights.

I must retract from my above position which was hastily made appearently without proper research. In our efforts to reach other star systems, we should definately take into account interstellar cosmic rays, not only from ambient fluxes appearent to a non-relativistic observer, but also from the incident particulate matter at relativistic ship speeds. Some sort of magnetosphere and/or dense shielding will be required, or atleast a layer of water or water ice with is a good absorber of cosmic rays with energies in the nuclear reaction by products range.

ljk November 3, 2009 at 0:32

The Sizes of Kuiper Belt Objects

Authors: Pedro Lacerda

(Submitted on 30 Oct 2009)

Abstract: One of the most fundamental problems in the study of Kuiper belt objects (KBOs) is to know their true physical size. Without knowledge of their albedos we are not able to distinguish large and dark from small and bright KBOs.

Spitzer produced rough estimates of the sizes and albedos of about 20 KBOs, and the Herschel space telescope will improve on those initial measurements by extending the sample to the ~150 brightest KBOs.

SPICA’s higher sensitivity instruments should allow us not only to broaden the sample to smaller KBOs but also to achieve a statistically significant sample of KBO thermal light curves (Herschel will measure only six objects).

A large sample covering a broad range of sizes will be key to identify meaningful correlations between size and other physical and surface properties that constrain the processes of formation and evolution of the solar system.

Comments: 6 pages, 6 figures, Proc. Workshop “The Space Infrared Telescope for Cosmology and Astrophysics: Revealing the Origins of Planets and Galaxies”

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Cite as: arXiv:0911.0004v1 [astro-ph.EP]

Submission history

From: Pedro Lacerda [view email]

[v1] Fri, 30 Oct 2009 20:03:20 GMT (546kb,D)

http://arxiv.org/abs/0911.0004

ljk November 3, 2009 at 0:34

The Dark Red Spot on KBO Haumea

Authors: Pedro Lacerda

(Submitted on 30 Oct 2009)

Abstract: Kuiper belt object 136108 Haumea is one of the most fascinating bodies in our solar system. Approximately 2000x1600x1000 km in size, it is one of the largest Kuiper belt objects (KBOs) and an unusually elongated one for its size. The shape of Haumea is the result of rotational deformation due to its extremely short 3.9-hour rotation period.

Unlike other 1000 km-scale KBOs which are coated in methane ice the surface of Haumea is covered in almost pure water-ice. The bulk density of Haumea, estimated around 2.6 g/cc, suggests a more rocky interior composition, different from the water-ice surface.

Recently, Haumea has become the second KBO after Pluto to show observable signs of surface features. A region darker and redder than the average surface of Haumea has been identified, the composition and origin of which remain unknown. I discuss this recent finding and what it may tell us about Haumea.

Comments: 7 pages, 2 figures, Proc. IAU 2009 Symposium S263 “Icy Bodies of the Solar System”

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Cite as: arXiv:0911.0009v1 [astro-ph.EP]

Submission history

From: Pedro Lacerda [view email]

[v1] Fri, 30 Oct 2009 20:15:32 GMT (161kb,D)

http://arxiv.org/abs/0911.0009

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