Strange Propeller-Like Object Discovered in the Outer Reaches of the Kuiper Belt
The bizarre, hourglass-shaped Kuiper belt object 2001QG298 spins round like a propeller as it orbits the Sun, according to an astronomer from Queens University Belfast. The discovery that the spinning object is tilted at nearly 90 degrees to the ecliptic plane is surprising, and suggests that this type of object could be very common in the Kuiper belt.
The Kuiper belt objects (KBOs) orbit the sun beyond Neptune and are the best preserved leftovers of the formation of the planets. 2001QG298 is a remarkable KBO made up from two components that orbit each other very closely, possibly touching.
"Imagine that you glue two eggs together tip to tip – that's approximately the shape of 2001QG298. It looks a bit like an hourglass," said Dr Pedro Lacerda at the Joint Meeting of the European Planetary Science Congress and the Division for Planetary Sciences in Nantes, France.
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The strange shape of 2001QG298 was uncovered by Dr Scott Sheppard and Prof David Jewitt in 2004. They noticed that 2001QG298's apparent brightness periodically tripled every 7 hours or so.
"The object is so distant that we cannot resolve its shape. But this brightness oscillation, called a lightcurve, reveals the strange shape of 2001QG298 as it spins round. The object appears faint at times because one lobe is hidden behind the other, so less area is reflecting sunlight. As the hidden component rotates back into view, we can see the full hour-glass shape. The reflecting area increases and the whole thing looks brighter," explains Lacerda.
However, Lacerda’s new study shows that 2001QG298's rotation is almost perpendicular to the plane of its orbit around the sun. Lacerda re-measured the object's lightcurve in late 2010 and noticed that it had changed from Sheppard and Jewitt’s observations. The lightcurve variation has become visibly shallower.
“It was impossible to tell from the original observations if the rotation and the orbital plane of 2001QG298 were aligned or perpendicular i.e. whether the object spun round horizontally like the blades on a helicopter or rotated vertically like the propeller of an aeroplane. The changes to the lightcurve variation show that it must be approximately vertical.
As 2001QG298 moves round in its orbit of The sun, our viewing geometry of the ‘propeller’ is gradually opening out from edge-on to seeing the whirling ‘blades’ full-face. This means that more of the reflecting surface is becoming visible at all times so the variation in the object’s brightness gradually disappears,” says Lacerda.
The most important consequence of this finding is that it suggests that this type of double KBO could be very common. When in 2004 Sheppard and Jewitt found 2001QG298 in a sample of 34 KBOs they realised that they were fortunate to spot its binary nature – if it had not happened to be edge-on at the time of their observations, they would not have seen the extreme lightcurve variation. They estimated that approximately 10% of all KBOs are contact binaries, assuming that their tilts are random.
However, Lacerda believes that the tilts of contact binaries may not actually be random and that objects similar to 2001QG298 could be even more common.
"It was a surprise to find that 2001QG298 is inclined by 90 degrees, but that's not the first time we’ve seen this in a contact binary,” he speculates. “There is another famous doublet object, a large Trojan asteroid called 624 Hektor. That object is also tilted almost 90 degrees."
If contact binaries tend to be highly tilted then the chance of spotting their characteristic variable lightcurve is even smaller – only about twice per orbit. The identification of one in a small sample implies that contact binaries may be even more abundant than Sheppard and Jewitt first thought. Lacerda estimates that as many as 25% of KBOs are contact binaries.
"If contact binaries do tend to be very inclined that may be telling us something about how these objects formed," concludes Lacerda.
Video of Object 2001QG298
"Imagine that you glue two eggs together tip to tip – that's approximately the shape of 2001QG298. It looks a bit like an hourglass," said Dr Pedro Lacerda at the Joint Meeting of the European Planetary Science Congress and the Division for Planetary Sciences in Nantes, France.
.
The strange shape of 2001QG298 was uncovered by Dr Scott Sheppard and Prof David Jewitt in 2004. They noticed that 2001QG298's apparent brightness periodically tripled every 7 hours or so.
"The object is so distant that we cannot resolve its shape. But this brightness oscillation, called a lightcurve, reveals the strange shape of 2001QG298 as it spins round. The object appears faint at times because one lobe is hidden behind the other, so less area is reflecting sunlight. As the hidden component rotates back into view, we can see the full hour-glass shape. The reflecting area increases and the whole thing looks brighter," explains Lacerda.
However, Lacerda’s new study shows that 2001QG298's rotation is almost perpendicular to the plane of its orbit around the sun. Lacerda re-measured the object's lightcurve in late 2010 and noticed that it had changed from Sheppard and Jewitt’s observations. The lightcurve variation has become visibly shallower.
“It was impossible to tell from the original observations if the rotation and the orbital plane of 2001QG298 were aligned or perpendicular i.e. whether the object spun round horizontally like the blades on a helicopter or rotated vertically like the propeller of an aeroplane. The changes to the lightcurve variation show that it must be approximately vertical.
As 2001QG298 moves round in its orbit of The sun, our viewing geometry of the ‘propeller’ is gradually opening out from edge-on to seeing the whirling ‘blades’ full-face. This means that more of the reflecting surface is becoming visible at all times so the variation in the object’s brightness gradually disappears,” says Lacerda.
The most important consequence of this finding is that it suggests that this type of double KBO could be very common. When in 2004 Sheppard and Jewitt found 2001QG298 in a sample of 34 KBOs they realised that they were fortunate to spot its binary nature – if it had not happened to be edge-on at the time of their observations, they would not have seen the extreme lightcurve variation. They estimated that approximately 10% of all KBOs are contact binaries, assuming that their tilts are random.
However, Lacerda believes that the tilts of contact binaries may not actually be random and that objects similar to 2001QG298 could be even more common.
"It was a surprise to find that 2001QG298 is inclined by 90 degrees, but that's not the first time we’ve seen this in a contact binary,” he speculates. “There is another famous doublet object, a large Trojan asteroid called 624 Hektor. That object is also tilted almost 90 degrees."
If contact binaries tend to be highly tilted then the chance of spotting their characteristic variable lightcurve is even smaller – only about twice per orbit. The identification of one in a small sample implies that contact binaries may be even more abundant than Sheppard and Jewitt first thought. Lacerda estimates that as many as 25% of KBOs are contact binaries.
"If contact binaries do tend to be very inclined that may be telling us something about how these objects formed," concludes Lacerda.
Video of Object 2001QG298
The Daily Galaxy via Europlanet
Comments
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I would change the title of this article to say Hourglass-Like instead of Propeller-Like. The term propeller has been used with respect to objects in rings (such as Saturn's) which are causing an increase in density before and after the object. I found the title set my expectations for the content far off track.
Posted by: antoniseb | October 04, 2011 at 05:56 AM
That looks like it might just work dude.
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Posted by: Jeoy WIlson | October 04, 2011 at 06:18 AM
they look like orbiting planets with long shadows cast from
their sun creating in the swirling haze the appearance of
Being solid objects.
Posted by: Jason bush | October 04, 2011 at 08:08 AM
they look like orbiting planets with long shadows cast from
their sun creating in the swirling haze the appearance of
Being solid objects.
Posted by: Jason bush | October 04, 2011 at 08:08 AM
could these nearly invisible KBO's be intelligently built alien satellites orbiting the sun?
www.holographicgalaxy.blogspot.com
Posted by: HoloGramUniverse.Wordpress.com | October 04, 2011 at 09:09 AM
There are more things in heaven and earth, Horatio, Than are dreamt of in your philosophy.
Posted by: women shoes | October 04, 2011 at 10:44 PM
Spinning hourglass? Great...the universe is running on Windows.
Posted by: Chas | October 05, 2011 at 10:43 AM
Spinning hourglass? Great...the universe is running on Windows.
Posted by: Chas | October 05, 2011 at 10:43 AM
We have seen comets like these "propellers", although I prefer the term "dumbbells". Comets Hartley 2 and Itokawa were both roughly shaped like this, see:
http://images.nationalgeographic.com/wpf/media-live/photos/000/283/overrides/1011045-hartley2-comet-collage-01_28353_600x450.jpg
http://upload.wikimedia.org/wikipedia/en/b/b4/Itokawa4.jpg
Posted by: Brce E. Arnold | October 05, 2011 at 11:13 PM
So who wants to run the figures to see which binary companion theory model best fits the fling parameters required for these objects and their properties? Or perhaps just give a few data set ranges that could be used in general? Tyche had some pretty narrow ranges. Walter Cruttenden has some other range possibilities, and I'm sure there are several others out there somewhere.
Posted by: SiliconJon | October 06, 2011 at 09:56 AM
It's a mass relay. Activate it and mankind joins galactic civilization.
Posted by: Bob | October 10, 2011 at 07:21 PM
Tyche had some pretty narrow ranges. Walter Cruttenden has some other range possibilities, and I'm sure there are several others out there somewhere.
Posted by: water for gas | February 13, 2012 at 07:55 AM