Starship Asterisk*

JohnD wrote: ↑Wed Jan 16, 2019 10:02 am Asteroid 6478 Gault has sprouted a tail.
https://www.lagranepoca.com/news/423844 ... 00-km.html

It is suggested that this is the result of a collision with another body out there.

But why a 'tail'? And not a cloud of debris around it? Same mechanism as a comet's tail, solar wind?

Chris Peterson wrote: ↑Wed Jan 16, 2019 5:18 pm

JohnD wrote: ↑Wed Jan 16, 2019 10:02 am Asteroid 6478 Gault has sprouted a tail.
https://www.lagranepoca.com/news/423844 ... 00-km.html

It is suggested that this is the result of a collision with another body out there.

But why a 'tail'? And not a cloud of debris around it? Same mechanism as a comet's tail, solar wind?

Not the solar wind. Radiation pressure is what creates a dust tail, whether from comets where the dust is released by evaporating gas, or in an asteroid collision, where it is released by the energy of the collision itself. Either way, we're talking very small particles- mostly in the micrometer range, not unlike smoke. A long, thin tail is indicative of a narrow range of particle sizes. A broad tail suggest a wider range of particle sizes. A collision probably creates a lot of fine dust, whereas a comet is simply releasing material of different sizes. That's why collisions appear to produce narrower tails (I know of at least one other asteroid collision, which also produced a long skinny tail). If we could aim Hubble at it we might see more complex debris patterns at the head, but with Hubble damaged and the shutdown preventing its repair, that may not happen.

Ann wrote: ↑Thu Jan 17, 2019 6:29 am

Chris Peterson wrote: ↑Wed Jan 16, 2019 5:18 pm Not the solar wind. Radiation pressure is what creates a dust tail, whether from comets where the dust is released by evaporating gas, or in an asteroid collision, where it is released by the energy of the collision itself. Either way, we're talking very small particles- mostly in the micrometer range, not unlike smoke. A long, thin tail is indicative of a narrow range of particle sizes. A broad tail suggest a wider range of particle sizes. A collision probably creates a lot of fine dust, whereas a comet is simply releasing material of different sizes. That's why collisions appear to produce narrower tails (I know of at least one other asteroid collision, which also produced a long skinny tail). If we could aim Hubble at it we might see more complex debris patterns at the head, but with Hubble damaged and the shutdown preventing its repair, that may not happen.

Sorry. How does radiation pressure differ from the solar wind?

https://en.wikipedia.org/wiki/6478_Gault wrote:

John Gault encased postage stamp

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<<6478 Gault, provisional designation 1988 JC1, is a Phocaea (foh-SEE-ə) asteroid from the inner regions of the asteroid belt, approximately 3.7 kilometers in diameter. The body's rotation period, pole and shape remain unknown. In October 2018, it was possibly impacted by an unidentified more than 500-meter-sized asteroid, causing it to become a main-belt comet with a tail. The likely S-type asteroid was discovered on 12 May 1988, by astronomer couple Carolyn and Eugene Shoemaker at the Palomar Observatory in California. It was named in memory of American planetary geologist Donald Gault (1923–1999), an expert in the field of impact crater forming processes. Gault conducted field experiments and applied his insight to the interpretation of impact data from the Moon, Earth, Mars and Mercury.

Gault is a core member of the Phocaea family. The large asteroid family consists of nearly 2,000 known stony asteroids, and was named after its largest member, 25 Phocaea. The old family formed up to 2.2 billion years ago and has the highest inclination of all families in the inner asteroid belt. Several of its members are also Mars-crossing asteroids with high eccentricities. The Phocaea family region contains other collisional families such as the recently identified carbonaceous, Tamara family, named after its potentially largest member 326 Tamara. The family has an estimated age of 264 million years.

Gault orbits the Sun at a distance of 1.9–2.8 AU once every 3 years and 6 months. Its orbit has an eccentricity of 0.19 and an inclination of 23° with respect to the ecliptic. The body's observation arc begins with its official discovery observation at Palomar in May 1988. In January 2019, it was discovered, that Gault possesses a comet tail, which had not been present in previous images. There is evidence that the asteroid became active in November 2018, and that material had been ejected from its surface, and that a collision or impact is responsible for its tail.>>

Chris Peterson wrote: ↑Wed Jan 16, 2019 5:18 pm... If we could aim Hubble at it we might see more complex debris patterns at the head, but with Hubble damaged and the shutdown preventing its repair, that may not happen.

bystander wrote: ↑Thu Jan 17, 2019 9:22 pm

Chris Peterson wrote: ↑Wed Jan 16, 2019 5:18 pm... If we could aim Hubble at it we might see more complex debris patterns at the head, but with Hubble damaged and the shutdown preventing its repair, that may not happen.

Hubble's Wide Field Camera 3 Recovered and Collecting Science
NASA | GSFC | Hubble | WFC3 | 2019 Jan 17