Dancing Brown Dwarf Stars

[MarkC]

Interesting things show up as they compare years of Hubble photos.

This seemingly unspectacular series of dots with varying distances between them actually shows the slow waltz of two brown dwarfs. The image is a stack of 12 images made over the course of three years with the NASA/ESA Hubble Space Telescope. Using high-precision astrometry, an Italian-led team of astronomers tracked the two components of the system as they moved both across the sky and around each other.

https://www.nasa.gov/feature/goddard/20 ... ing-dwarfs

Mark

[merle]

That's amazing. It's great when we can see evidence of the heaven's in motion.


Merle

[Dave Venne]

Hubble just keeps on giving! It's amazing to see that kind of motion in such detail.

What I don't understand is how the two stars can move along the two large arcs (which looks rather like a spiral motion in the time lapse) unless they're under the influence of a third mass. A cold, long-dead neutron star, maybe?

[MarkC]

Dave

I agree, it looks strange but "Hubble data showed that the two dwarfs are indeed dancing alone, unperturbed by a massive planetary companion."

Mark

[merle]

What I don't understand is how the two stars can move along the two large arcs (which looks rather like a spiral motion in the time lapse) unless they're under the influence of a third mass. A cold, long-dead neutron star, maybe?

Would it be the angle we're viewing from or the stars in elliptical orbits?


Merle

[Dave Venne]

Dave

I agree, it looks strange but "Hubble data showed that the two dwarfs are indeed dancing alone, unperturbed by a massive planetary companion."

Mark

I read that too, but how does one explain that looping motion? I don't think it's a question of the system's orbital plane of motion or the shape of the orbit.

It might be that the loops are caused by our changing viewpoint as the Earth orbits the Sun, and it's actually a really nice display of parallax.

[Dale Smith]

Dave’s suggestion that the looping is caused by parallax is interesting. However, I struggle to reconcile it with the details.

The link that instigated this thread said there were 12 photos made over the course of 3 years. It showed two images. The first was an animation of the photos in sequence, looping endlessly. The second was a static superposition of all 12 photos with curves drawn in to make it easier to track each star’s progress.

These curves look like rounded W ‘s (or 3’s turned on their sides) My problem with the parallax interpretation is that the top pixels of each W should represent the camera returning to its original position after one year’s orbit around our sun. The upper left pixel would represent time=0. The upper middle pixel would represent time = 1 year. The upper right pixel would represent time = 2 years. This does not add up to the 3 years mentioned in the link. Does anyone know the exact beginning and ending dates of the 12 photos? Could they represent, say, a 25 month period spanning December of one year, the next 2 complete calendar years and January of the final year?

[Dave Venne]

It should be possible to break the animated image into single frames and align them, then rebuild the animation. This will remove the system's proper motion and possibly give a clearer idea of what is happening. I'll give it a try.

[EDITED] Here are the results. The animated GIF:



This shows the stars seeming to make about a quarter revolution around their center of mass.

Next is a stacked image, showing the motion of the two-dwarf system as a double curve traced out by the field stars

CombineFilesAvg.jpg

This resembles a portion of a helix seen from an angle, kind of like this:

helix.jpg

I agree, the dates of the observations would be really good to know. And it would also be good to know the orientation of the curves relative to the Earth's orbital plane, too.