For the first time, astronomers catch asteroid in the act of changing color

For first time, astronomers catch asteroid in the act of changing color
The asteroid 6478 Gault is seen with the NASA/ESA Hubble Space Telescope, showing two narrow, comet-like tails of debris that tell us that the asteroid is slowly undergoing self-destruction. The bright streaks surrounding the asteroid are background stars. The Gault asteroid is located between the orbits of Mars and Jupiter. Credit: NASA, ESA, K. Meech and J. Kleyna, O. Hainaut

Last December, scientists discovered an "active" asteroid within the asteroid belt, sandwiched between the orbits of Mars and Jupiter. The space rock, designated by astronomers as 6478 Gault, appeared to be leaving two trails of dust in its wake—active behavior that is associated with comets but rarely seen in asteroids.

While astronomers are still puzzling over the cause of Gault's comet-like activity, an MIT-led team now reports that it has caught the asteroid in the act of changing color, in the near-infrared spectrum, from red to blue. It is the first time scientists have observed a color-shifting asteroid, in real-time.

"That was a very big surprise," says Michael Marsset, a postdoc in MIT's Department of Earth, Atmospheric and Planetary Sciences (EAPS). "We think we have witnessed the asteroid losing its reddish dust to space, and we are seeing the asteroid's underlying, fresh blue layers."

Marsset and his colleagues have also confirmed that the asteroid is rocky—proof that the asteroid's tail, though seemingly comet-like, is caused by an entirely different mechanism, as comets are not rocky but more like loose snowballs of ice and dust.

"It's the first time to my knowledge that we see a rocky body emitting dust, a little bit like a comet," Marsset says. "It means that probably some mechanism responsible for dust emission is different from comets, and different from most other active main-belt asteroids."

Marsset and his colleagues, including EAPS Research Scientist Francesca DeMeo and Professor Richard Binzel, have published their results today in the journal Astrophysical Journal Letters.

A rock with tails

Astronomers first discovered 6478 Gault in 1988 and named the asteroid after planetary geologist Donald Gault. Until recently, the was seen as relatively average, measuring about 2.5 miles wide and orbiting along with millions of other bits of rock and dust within the inner region of the , 214 million miles from the sun.

In January, images from various observatories, including NASA's Hubble Space Telescope, captured two narrow, comet-like tails trailing the asteroid. Astronomers estimate that the longer tail stretches half a million miles out, while the shorter tail is about a quarter as long. The tails, they concluded, must consist of tens of millions of kilograms of dust, actively ejected by the asteroid, into space. But how? The question reignited interest in Gault, and studies since then have unearthed past instances of similar activity by the asteroid.

"We know of about a million bodies between Mars and Jupiter, and maybe about 20 that are active in the asteroid belt," Marsset says. "So this is very rare."

He and his colleagues joined the search for answers to Gault's activity in March, when they secured observation time at NASA's Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. Over two nights, they observed the asteroid and used a high-precision spectrograph to divide the asteroid's incoming light into various frequencies, or colors, the relative intensities of which can give scientists an idea of an object's composition.

From their analysis, the team determined that the asteroid's surface is composed mainly of silicate, a dry, rocky material, similar to most other asteroids, and, more importantly, not at all like most comets.

Comets typically come from the far colder edges of the solar system. When they approach the sun, any surface ice instantly sublimates, or vaporizes into gas, creating the comet's characteristic tail. Since Marsset's team has found 6478 Gault is a dry, rocky body, this means it likely is generating dust tails by some other active mechanism.

A fresh change

As the team observed the asteroid, they discovered, to their surprise, that the rock was changing color in the near-infrared, from red to blue.

"We've never seen such a dramatic change like this over such a short period of time," says co-author DeMeo.

The scientists say they are likely seeing the asteroid's surface dust, turned red over millions of years of exposure to the sun, being ejected into space, revealing a fresh, less irradiated surface beneath, that appears blue at near-infrared wavelengths.

"Interestingly, you only need a very thin layer to be removed to see a change in the spectrum," DeMeo says. "It could be as thin as a single layer of grains just microns deep."

So what could be causing the asteroid to turn color? The team and other groups studying 6478 Gault believe the reason for the color shift, and the asteroid's comet-like activity, is likely due to the same mechanism: a fast spin. The asteroid may be spinning fast enough to whip off layers of dust from its surface, through sheer centrifugal force. The researchers estimate it would need to have about a two-hour rotation period, spinning around every couple of hours, versus Earth's 24-hour period.

"About 10 percent of asteroids spin very fast, meaning with a two- to three-hour rotation period, and it's most likely due to the sun spinning them up," says Marsset.

This spinning phenomenon is known as the YORP effect (or, the Yarkovsky-O"Keefe-Radzievskii-Paddack effect, named after the scientists who discovered it), which refers to the effect of solar radiation, or photons, on small, nearby bodies such as asteroids. While asteroids reflect most of this radiation back into space, a fraction of these photons is absorbed, then reemitted as heat, and also momentum. This creates a small force that, over millions of years, can cause the asteroid to spin faster.

Astronomers have observed the YORP effect on a handful of asteroids in the past. To confirm a similar effect is acting on 6478 Gault, researchers will have to detect its spin through light curves—measurements of the asteroid's brightness over time. The challenge will be to see through the asteroid's considerable tail, which can obscure key portions of the asteroid's light.

Marsset's team, along with other groups, plan to study the asteroid for further clues to activity, when it next becomes visible in the sky.

"I think [the group's study] reinforces the fact that the asteroid belt is a really dynamic place," DeMeo says. "While the asteroid fields you see in the movies, all crashing into each other, is an exaggeration, there is definitely a lot happening out there every moment."


Explore further

Hubble watches spun-up asteroid coming apart

More information: Megan E. Schwamb et al. Col-OSSOS: The Colors of the Outer Solar System Origins Survey, The Astrophysical Journal Supplement Series (2019). DOI: 10.3847/1538-4365/ab2194

Michaël Marsset et al. Col-OSSOS: Color and Inclination Are Correlated throughout the Kuiper Belt, The Astronomical Journal (2019). DOI: 10.3847/1538-3881/aaf72e

This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.

Citation: For the first time, astronomers catch asteroid in the act of changing color (2019, August 30) retrieved 17 September 2019 from https://phys.org/news/2019-08-astronomers-asteroid.html
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Aug 30, 2019
Marsset and his colleagues have also confirmed that the asteroid is rocky—proof that the asteroid's tail, though seemingly comet-like, is caused by an entirely different mechanism, as comets are not rocky but more like loose snowballs of ice and dust.

The plasma ignoramuses are continuously grasping at straws. It's the same mechanism given comets composition are almost identical to asteroids.
https://youtu.be/9Oner1To4Y8

Aug 30, 2019
My favorite part of that video is at 4:15 where the planets have a giant electric current between them. That's what's responsible for comets and asteroids. And it only happened in the last few thousand years! This video is pure gold. People actually believe this stuff?

How much Thunderbolts merchandise have you purchased CD?

Aug 30, 2019
well MrB
when camtthink l swipes his mother's creditcard from her purse tp place his orders to Thunderdolts Marketing(™)

it is with assistance of Anonym151810
who is one of Thunderdolts Marketing(™ offsite customer ordering network

& who is claiming to be making a fortune selling cantthink the complete collection of cherub decorated brass "Holey Thundermugs"
from the Thunderdolts officially blessed divinity products line

now MrB, only a commie hippy liberal-arts major league atheist would want to interfere with such a piously lucrative scam

Aug 30, 2019
"Comets typically come from the far colder edges of the solar system. When they approach the sun, any surface ice instantly sublimates, or vaporizes into gas, creating the comet's characteristic tail."

No icy comets proven. YORP, pathetic.

Aug 30, 2019
My favorite part of that video is at 4:15 where the planets have a giant electric current between them. That's what's responsible for comets and asteroids. And it only happened in the last few thousand years! This video is pure gold. People actually believe this stuff?

How much Thunderbolts merchandise have you purchased CD?

What really funny, is mainstream pseudoscience acknowledges planetary wandering as suggested by the video, the only difference being is that it happened "billions of years ago". Yet all the evidence suggests otherwise.

Aug 30, 2019
The plasma ignoramuses are continuously grasping at straws. It's the same mechanism given comets composition are almost identical to asteroids.
https://youtu.be/9Oner1To4Y8


Trivially false. Particularly as we've actually been to comets and asteroids. And measured their densities. And smashed impactors into them. Et cetera. Stop making stuff up.

Aug 30, 2019
"Comets typically come from the far colder edges of the solar system. When they approach the sun, any surface ice instantly sublimates, or vaporizes into gas, creating the comet's characteristic tail."

No icy comets proven. YORP, pathetic.


Liar. We have blasted thousands of tonnes of ice out of Tempel 1 back in '05. Did you miss that press release, due to the conmen T & T failing to report it to their imbecilic followers? Or what about the shed loads of ice floating around Hartley 2, after being ejected by CO2 jets? As observed. Again, not something your high priests wanted you to know. Look at the pretty picture!

https://phys.org/...met.html

Aug 30, 2019
My favorite part of that video is at 4:15 where the planets have a giant electric current between them. That's what's responsible for comets and asteroids. And it only happened in the last few thousand years! This video is pure gold. People actually believe this stuff?

How much Thunderbolts merchandise have you purchased CD?

What really funny, is mainstream pseudoscience acknowledges planetary wandering as suggested by the video, the only difference being is that it happened "billions of years ago". Yet all the evidence suggests otherwise.


No evidence suggests otherwise. You are making things up. It is a bad habit. Didn't your parents tell you about that sort of thing? You really must stop it.

Aug 31, 2019
Being a subject to the "YORP" effect must have asteroid Gault spinning in its spacious grave! I can "hear" the other asteroids sniggering.

My favorite part of that video is at 4:15 where the planets have a giant electric current between them. That's what's responsible for comets and asteroids. And it only happened in the last few thousand years!


Oy vey. This nonsense nonscience, right after the article discuss how this may not be a mystery as much as we need more tests to be less uncertain!?

So planets cannot have net charges and currents outside their magnetic fields; I once saw an astrophysicist for fun and effect estimate that Earth's dynamo field generated a persistent charge of 60 q or that many (sixty) electrons of net charge. The Jupiter flux tube is local, and no other flux tubes are known AFAIK.

The juxtaposition of these trolls with a religious ideology timeline is telling: these are multiple crackpots akin to Dunning-Kruger sufferers. I have the trolls blocked.

Aug 31, 2019
Or maybe it was 60 C, which is many more electrons, human memory impressions are fallible.

But in any case far less than 1 Ah total charge, which is handily stored in a phone. Not so imposing when stated in factual terms...

Sep 03, 2019
The Jupiter flux tube is local, and no other flux tubes are known AFAIK.

Willful ignorance stops scientific progress in its tracks. When observation doesn't match your beliefs, just ignore it and continue along in your safe little space.

Sep 03, 2019
The comment "The scientists say they are likely seeing the asteroid's surface dust, turned red over millions of years of exposure to the sun, being ejected into space" is followed up by "The asteroid may be spinning fast enough to whip off layers of dust from its surface"

And not just a little dust, either --> "The tails, they concluded, must consist of tens of millions of kilograms of dust, actively ejected by the asteroid, into space."

So after MILLIONS of years, now the asteroid is spinning fast enough to throw the dust off?

What caused such a massive change in the rotation/orbit/overall movement of this asteroid that it is suddenly rotating fast enough to throw off dust it has been gathering for millions of years?

Some sort of glancing impact seems the most likely cause of the change, but there is no mention here of any mechanism (other than a gradual spinning up via the YORP effect) to account for the observed sudden change.

Sep 06, 2019
The Jupiter flux tube is local, and no other flux tubes are known AFAIK.

Willful ignorance stops scientific progress in its tracks. When observation doesn't match your beliefs, just ignore it and continue along in your safe little space.


And what would you and your cult know about science?

Sep 07, 2019
Comets: A Tale of Two Tails?

These tails develop tails approaching perihelion
Solar heat vaporizes some cometary material
Releasing dust particles trapped in the ice
Solar radiation pressure
And solar wind blow gas and dust from the comet's nucleus
Forming two separate tails
The ion tail
And the dust tail

These Two Dusty Tails

Ultraviolet light
Ionizes the neutral gas blowing off this comet
Where the solar wind carries these ions
Out from the Sun
To form the ion tail
Which glows blue

This dust tail
Consists of neutral small dust particles
Pressure from the Sun's radiation
Pushes these particles
Away from the comet's nucleus
Where these particles
Continue to follow
This comets
Orbit around the Sun
Forming a diffuse
Curved tail
Appearing
White or pink

https://www.skyan...e-tails/

Sep 07, 2019
Solar Heat Vaporizes Cometary Material

Releasing dust particles trapped in the ice
Interesting
What do these dust particles consist of
For there seems
Memories
Of comets
As hard as nails
Braking hard as nails
Grappling hooks
For these dusty particles, are said to consist of asteroid material, frozen solid in this vacuum of space

Sep 07, 2019
Dusty Tails in Distinction

This distinction between asteroids
And comets
Appears to be blurring
As
These dusty collections of debris
Occupying this vacuum
Appears to be
Held together
With a combination of forces
One of which
Appears to be Ice

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