Space

New map reveals a third of the stars in the Milky Way have dramatically changed orbit

New map reveals a third of the...
Two pairs of stars (red and blue), which started in the same orbit, have moved (red), or are moving (blue), into new orbits
Two pairs of stars (red and blue), which started in the same orbit, have moved (red), or are moving (blue), into new orbits
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Two pairs of stars (red and blue), which started in the same orbit, have moved (red), or are moving (blue), into new orbits
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Two pairs of stars (red and blue), which started in the same orbit, have moved (red), or are moving (blue), into new orbits

It's easy to think of stars as being fixed in place, because that's how we see them in the sky. But like Earth and the other planets, they have orbits. And it turns out those orbits can change dramatically. In creating a new map of the Milky Way as part of the Sloan Digital Sky Survey (SDSS), scientists recently discovered that around 30 percent of the stars in our galaxy have done exactly that – they've moved into a totally new orbit.

The scientists came upon this revelation by studying the chemical composition of each star, which is evident in the spectra – or the range and intensity of light wavelengths coming from the star – with different lines in a spectrograph corresponding to elements and compounds.

"Stellar spectra show us that the chemical makeup of our galaxy is constantly changing," explains New Mexico State University professor Jon Holtzman, who was involved in the study. "Stars create heavier elements in their core, and when the stars die, those heavier elements go back into the gas from which the next stars form."

The amount of heavy elements in each star tells astronomers which part of the galaxy it was born in, like a stellar fossil record. But data from the SDSS Apache Point Observatory Galactic Evolution Explorer (APOGEE) spectrograph, which studied 100,000 stars during a four-year period, suggests that as many as 30 percent of stars have moved far from their birthplace.

The scientists believe that the pattern can be explained by a model in which stars gradually move closer or farther from the center of the galaxy as they get older. This radial migration is thought to be caused by irregularities in the Milky Way's galactic disk – the spiral arms of gas, dust, and young stars.

But this discovery is just the tip of the iceberg for APOGEE data.

"Once we unlock the full information content of APOGEE, we will understand the chemistry and shape of our galaxy much more clearly," said APOGEE's principal investigator Steven Majewski.

A paper describing the study was published in The Astrophysical Journal.

Source: New Mexico State University

13 comments
Jugen
When the stars move out to more exterior parts of the galaxy, perhaps it is then when solar systems are born as on their journey they pick up orphan planets along the way. I wonder if solar systems even poach planets from other solar systems?
Bob
I'm sure someone will point to imaginary dark matter and dark energy as an explanation for erratic orbits. I would be more inclined to think that larger and smaller stars could have their orbits changed by the gravitational slingshot effect of simply passing near each other.
ramriot
Some good research and a good demonstration of evaporative cooling but on a galactic scale. As a galaxy evolves and matter is collected into discrete particles (stars) its begins to exhibit the behaviours of an ideal gas. In that it has a 'temperature' measured as the average motion of the particles. This is not like the temperature you can measure with a spectrograph or a thermometer, its just a way of stating the average orbital velocities of the particles due to gravitation. Thus it becomes possible for particle on particle interactions (slingshots) to transfer kinetic energy from one star to another. The star with the greater energy migrates outwards (or even leaves the galaxy altogether), while the other migrates inwards. Thus over time, as stars age there is a general tendency for them to migrate towards the barycentre, 'cooling' while a small number escape entirely 'evaporate'.
JAT
Maybe we just don't understand what we're looking at. Time for a new model.
Dave Mikulec
Geez, I'm so tired of moving. ;-)
JerryHatfield
I'm more inclined to believe that these start were originally plotted incorrectly. Seems to me that a proper "Orbit" tends to be more or less fixed. Sure it may be eccentric, and gravity from transients would throw off a few, but for a whole constellation (30%!) to shift orbits, there's a fundamental mistake somewhere in the original calculations. The rationale provided for the change seems specious. Personally, if 30% of the stars in the universe really HAVE shifted, I think we're headed for a lot of trouble in the future.
CherylDahl
God is an amazing artist and designer! :)
Dave Lawrence
I dunno, you turn your back for 5 MINUTES . . . . .
RayScucci
How much of a shift could have occurred? I mean it supposedly takes 250 million years for our solar system to orbit the Milky Way. then of course once everything completes one orbit there will be some various changes. Isn't it pretty much the same way a hurricane works? When it rotates, it may still look like a hurricane, but the outer bands alter as they expand and contract.
Ernani Medenilla
How about Dark Matter, must have made particle move to other direction? How about an invisible hand... Dark Matter is an invisible hand! Who decides where this things go? We only observe and marveled over it, we can't do anything about it except we try to figure, nothing more. Same goes with life here on Earth I'm sure, with or without Evolution theory ideas.