Hubble data used to look 10,000 years into the future (w/ Video)

Oct 26, 2010
The multicolor snapshot, at top, taken with Wide Field Camera 3 aboard NASA's Hubble Space Telescope, captures the central region of the giant globular cluster Omega Centauri. All the stars in the image are moving in random directions, like a swarm of bees. Astronomers used Hubble's exquisite resolving power to measure positions for stars in 2002 and 2006. From these measurements, they can predict the stars' future movement. The bottom illustration charts the future positions of the stars highlighted by the white box in the top image. Each streak represents the motion of the star over the next 600 years. The motion between dots corresponds to 30 years. Credit: NASA, ESA, and G. Bacon (STScI)

(PhysOrg.com) -- The globular star cluster Omega Centauri has caught the attention of sky watchers ever since the ancient astronomer Ptolemy first catalogued it 2,000 years ago. Ptolemy, however, thought Omega Centauri was a single star. He didn't know that the "star" was actually a beehive swarm of nearly 10 million stars, all orbiting a common center of gravity.

The stars are so tightly crammed together that astronomers had to wait for the powerful vision of NASA's to peer deep into the core of the "beehive" and resolve individual stars. Hubble's vision is so sharp it can even measure the motion of many of these stars, and over a relatively short span of time.

A precise measurement of star motions in giant clusters can yield insights into how stellar groupings formed in the , and whether an "intermediate mass" black hole, one roughly 10,000 times as massive as our Sun, might be lurking among the stars.

Analyzing archived images taken over a four-year period by Hubble's Advanced Camera for Surveys, astronomers have made the most accurate measurements yet of the motions of more than 100,000 cluster inhabitants, the largest survey to date to study the movement of stars in any cluster.

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This movie sequence begins with a ground-based image of the giant globular star cluster Omega Centauri and zooms very tightly in to a Hubble Space Telescope image of the central region of the cluster. In a simulation based on Hubble data, the stars appear to be moving in random directions, like a swarm of bees. Astronomers used Hubble's exquisite resolving power to measure positions for stars in 2002 and 2006. From these measurements, they can predict the stars' future movement, shown here for the next 10,000 years. Credit: NASA, ESA, and J. Anderson, R. van der Marel, and G. Bacon (STScI)

"It takes high-speed, sophisticated computer programs to measure the tiny shifts in the positions of the stars that occur in only four years' time," says astronomer Jay Anderson of the Space Telescope Science Institute in Baltimore, Md., who conducted the study with fellow Institute astronomer Roeland van der Marel. "Ultimately, though, it is Hubble's razor-sharp vision that is the key to our ability to measure stellar motions in this cluster."

Adds van der Marel: "With Hubble, you can wait three or four years and detect the motions of the stars more accurately than if you had waited 50 years on a ground-based telescope."

The astronomers used the Hubble images, which were taken in 2002 and 2006, to make a movie simulation of the frenzied motion of the cluster's . The movie shows the stars' projected migration over the next 10,000 years.

Identified as a globular star cluster in 1867, Omega Centauri is one of roughly 150 such clusters in our Milky Way Galaxy. The behemoth stellar grouping is the biggest and brightest globular cluster in the Milky Way, and one of the few that can be seen by the unaided eye. Located in the constellation Centaurus, Omega Centauri is viewable in the southern skies.

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Mayday
3 / 5 (3) Oct 26, 2010
To my eye, the video and the diagram seem to show every star traveling in a straight line, which is obviously not the case. What am I missing?

And I don't think the central image in the video is an image of the cluster's "core," but rather an image looking straight through the cluster's core. Doesn't it also include stars from the close side of the cluster as well as the far side? These stars would be nowhere near the core.
YouAreRight
5 / 5 (1) Oct 26, 2010
Foreground stars are recognizable by their distinct cross-like appearance. Background stars and galaxies would be moving too slowly compared to the stars in the central region of Omega Centauri to interfere with the observations. The stars may appear to be moving in straight lines but we are only looking at a 10,000yr period, not nearly enough to discern simple harmonic motion or arcs with the naked eye.
ArtyNouveau
2.3 / 5 (3) Oct 26, 2010
Furthermore, it takes three points (observations) to define an arc. This simulation is based on only two.
Skeptic_Heretic
2.3 / 5 (3) Oct 26, 2010
Furthermore, it takes three points (observations) to define an arc. This simulation is based on only two.
It doesn't take 3 points to define a delta in perceived motion of a point and extrapolate future posistion.

This is simple calculus.
winthrom
5 / 5 (2) Oct 26, 2010
Skeptic_Heretic: Actually simple analytic geometry. Three points will describe a curve that is second order (one maximum point) like an arc, which is simple calculus.
that_guy
1.8 / 5 (5) Oct 26, 2010
It seems that they think that globular clusters are too old to be affected by gravity. I understand that sheer amount of gravitational interactions would be near impossible to calculate, but to ignore it altogether renders this exercise completely pointless and asinine...
DamienS
5 / 5 (1) Oct 26, 2010
To my eye, the video and the diagram seem to show every star traveling in a straight line, which is obviously not the case. What am I missing?

More data points and the third dimension.

It seems that they think that globular clusters are too old to be affected by gravity.

Where does it say that?
msadesign
not rated yet Oct 27, 2010
Over the course of a very short time, the stars would likely appear to be traveling in a straight line. I am thinking that any orbit would have a very long radius and so not apparent in the very short term.
Skeptic_Heretic
1 / 5 (1) Oct 27, 2010
I really don't understand why you gents are saying that there are only two reference points. This was done from multiple images of a 4 year period of time. There are detectable differences within a single month, let alone of the course of this period of time.

They're not comparing 1 image from 04 and one from 06. They're comparing two sets of thousands of images.
DamienS
5 / 5 (2) Oct 27, 2010
I really don't understand why you gents are saying that there are only two reference points. This was done from multiple images of a 4 year period of time...They're not comparing 1 image from 04 and one from 06. They're comparing two sets of thousands of images.

I re-read the article but it still reads like they're dealing with two data points. Ir says:
The astronomers used the Hubble images, which were taken in 2002 and 2006

I dunno, maybe I'm still reading it wrong, but to me that sounds like they took a set of images in 2002 and another set in 2006 and extrapolated, rather than taking continuous images from 2002 to 2006. Is a 'set' of images taken in one year considered a single data point (as a long exposure)?

Skeptic_Heretic
1 / 5 (1) Oct 27, 2010
Is a 'set' of images taken in one year considered a single data point (as a long exposure)?
It isn't a single long exposure from 02 and a single from 06. It is multiple exposures from 02 and multiple exposures from 06 that are used in the process.
El_Nose
not rated yet Oct 27, 2010
correct me if I am wrong -- I am probably wrong...

the only way to observe SHM is to have a refence frame on the order of or longer than the period, or frequency correct. Well we may not have made the observation on that order but we do know the center of gravity that they are all pinned to. so in effect they are travelling in huge elliptical orbits , (RIGHT?? I am thinking Kepplers equations here.. ) around this center of gravity. So unless they are as close to this center of gravity as say the outer boundry of the solar systems Oort Cloud your not going to see a star do a circle in that video.... furthermore it would be against reason to expect them to be packed so close otherwise they would be colliding all the time.

please correct me if I am wrong.
yyz
5 / 5 (3) Oct 27, 2010
Indeed, 2 datasets were used to determine the proper motions of stars in Omega Cen. The first dataset was aquired over 4 days, June 27-30, 2002; the second dataset was obtained June 22, 2006. Both datasets consist of a series of images taken by Hubble that vary in exposure length, filter wavelength and pointing (a 3rd dataset from 2004 was also used, but not to produce the final proper motion catalog). The 4 day period in 2002 is considered as a 'single' observation and the epoch is given as 2002.49, as is the one in 2006 (2006.56). This gives a baseline of 4.07 years. Details of the observations are given in the paper by Anderson et al from the HubbleSite: http://hubblesite...related/

(Although I was able to download a copy this 31Mb PDF yesterday, no such luck today, YMMV)
yyz
5 / 5 (2) Oct 27, 2010
El Nose,

You are correct in noting the stars in globular clusters are for the most part in elliptical orbits around the gravity well of a globular cluster. Orbital periods can be millions of years.

"So unless they are as close to this center of gravity as say the outer boundry of the solar systems Oort Cloud your not going to see a star do a circle in that video..."

The main purpose of this study was to look for stellar motions that might be caused by an intermediate mass BH, similar (but not as extreme) to what we see in our galaxy with the SMBH Sag A*. A 2008 paper claimed there was evidence to infer the presence of a IMBH with a mass of 4 suns. This work found no evidence of such an object and put an upper mass limit at 1.2 Msun, only slightly larger than stellar mass BHs (this is the real story here). Again, details can be found in papers (I & II) in my link above.
napdaw
4 / 5 (1) Oct 27, 2010
So cool - 10000 years in the future - but really its the past because of how long the light takes to reach us!
Canman
4 / 5 (1) Oct 30, 2010
OK, so they are not accounting for gravitational effects here. But this is a very, very awesome video. I have seen globular cluster many times in my telescope. But, until now, I have never conceptualized what it would look like with highly magnified pinpoint resolution, much less be able to conceive the "beehive"-like motion within. This is really astounding. Hubble is a jewel among human achievements. Can't wait for 22nd century astronomy!!
ThanderMAX
1 / 5 (1) Nov 01, 2010
Looks like Brownian motion in space