Starship Asterisk*

Holger Nielsen wrote: ↑Sun Jan 31, 2021 8:41 am According to the link given (https://hubblesite.org/image/616/category/39-asteroids) they "were created by cosmic rays, energetic subatomic particles that struck the camera's detector". But I don't understand why some are colored yellow and others blue.

Holger Nielsen wrote: ↑Sun Jan 31, 2021 1:04 pm Yes, of course, Ann, you must be right, its a filter effect! Thank you, Color Commentator. As to the short yellow streaks, I think they are due to cosmic rays just as the very short streaks, perhaps coming in at a low angle. Asteroids at the same distance would create streaks of about the same length. But on the other hand the long blue streak could originate from a *very* close asteroid. To distinguish one would have to know the exposure time and the image scale.

Sa Ji Tario wrote: ↑Sun Jan 31, 2021 1:57 pm I understand that the Earth grows about 4,000 tons of dust per year that we receive by the Pointing-Robertson effect

Wadsworth wrote: ↑Sun Jan 31, 2021 4:24 pm It's a little confusing for me to understand how Hubble caught a picture of an asteroid burning up in our atmosphere.
Is there still enough atmosphere where Hubble is in orbit that it can catch an asteroid burning up while pointed away from the Earth?
Or was this image captured when Hubble was pointed more towards Earth, catching the asteroid from a 'side' angle?

APOD Robot wrote: ↑Sun Jan 31, 2021 5:07 am
Explanation: Many kilograms of space dust pitter to Earth daily.

Henry Wadsworth Longfellow, "The Children's Hour" wrote:

• : Between the dark and the daylight,
  : When the night is beginning to lower,
  : Comes a pause in the day's occupations,
  : That is known as the Children's Hour.
  
  : I hear in the chamber above me
  : The patter of little feet,
  : The sound of a door that is opened,
  : And voices soft and sweet.

................................................................
pitter-patter : a series of quick, light knocking sounds:

"I heard the pitter-patter of tiny feet." (dust mite radius ~ 1.5 x 10^-4 m)

Chris Peterson wrote: ↑Sun Jan 31, 2021 2:57 pm

Sa Ji Tario wrote: ↑Sun Jan 31, 2021 1:57 pm
I understand that the Earth grows about 4,000 tons of dust per year that we receive by the Pointing-Robertson effect

Probably more in the range of 100,000 to 1,000,000 tons. And only some is delivered from outside our orbit by the Poynting-Roberson effect. We encounter material from inside our orbit being pushed outward by solar wind and radiation pressure, we encounter cometary debris in orbits that intersect our own, we encounter material larger than dust that is perturbed into orbits that cross ours.

https://link.springer.com/article/10.1007/s11214-017-0458-1 wrote:
Impacts of Cosmic Dust on Planetary Atmospheres and Surfaces
by John M. C. Plane, George J. Flynn, Anni Määttänen, John E. Moores, Andrew R. Poppe, Juan Diego Carrillo-Sanchez & Constantino Listowski

Space Science Reviews volume 214, Article number: 23 (2018)
Published: 21 December 2017

Fig. 7 : The estimated mass accretion rates of extraterrestrial objects at the top of the Earth’s atmosphere are dominated by two peaks. The peak at small masses is caused by the continuous accretion of cosmic dust, while the peak at large masses results from the infrequent impacts of large bodies (adapted from Kyte and Wasson 1986)

---

Surface Accretion of Dust and Meteorites

<<The contribution by dust and meteorites to planetary surfaces was demonstrated by the Apollo samples. Elemental analyses showed that the Lunar regolith and regolith breccias had elevated levels of Ir, Au, Zn, Cd, Ag, Br, Bi, and Tl compared to the ordinary Lunar rocks in a pattern that indicated the addition of 1.5% to 2.0% carbonaceous chondrite-like material to the regolith (Keays et al. 1970; Anders et al. 1973). In the case of the Earth, the mass flux at the top of the atmosphere has been estimated by combining results from satellite impact measurements for small particles, radar meteors for intermediate size objects, and the cratering record for large objects, as discussed by Peucker-Ehrenbrink et al. (2016). As shown in Fig. 7, the mass-frequency distribution is bimodal, with peaks corresponding to the continuous, planet-wide input of dust and the infrequent impact of large bodies, with a minimal contribution from objects in the intermediate size range. Measurements of impacts onto the Long Duration Exposure Facility, which was in low-Earth orbit for about 69 months, indicate that the accretion rate of cosmic dust into the Earth’s atmosphere is 110±55 t/d [= 20,000 to 60,000 tonnes/year] in the current era (Love and Brownlee 1993). This is at least 100 times larger than the annual influx of meteorites (Bland et al. 1996), with particles in the narrow mass range from 10⁻⁸ to 10⁻³ g contributing more than 80% of the total mass flux of meteoritic material in the 10⁻¹³ to 10⁶ g mass range incident on the Earth (Hughes 1978; Carrillo-Sánchez et al. 2016). Modeling by Carrillo-Sánchez et al. (2016) of the dust up to 500 μm in diameter indicates that the total mass input is 43±14 t/d, with 35.4 t/d surviving as either unmelted particles or melted spherules, and the remaining 7.9 t/d being deposited in the upper atmosphere as ablated atoms. The dust accretion rate was likely much greater during the first 0.6 billion years of Solar System history, when asteroids and comets were more abundant in the inner Solar System as evidenced by the higher impact rate of large objects on the Moon during the Late Heavy Bombardment (Hartmann et al. 2000).>>

https://en.wikipedia.org/wiki/Long_Duration_Exposure_Facility wrote:

LDEF is removed from Columbia's payload bay

---

<<NASA's Long Duration Exposure Facility, or LDEF (pronounced "eldef"), was a school bus-sized cylindrical facility designed to provide long-term experimental data on the outer space environment and its effects on space systems, materials, operations and selected spores' survival. It was placed in low Earth orbit by Space Shuttle Challenger in April 1984. LDEF successfully carried science and technology experiments for about 5.7 years that have revealed a broad and detailed collection of space environmental data. LDEF's 69 months in space provided scientific data on the long-term effects of space exposure on materials, components and systems that has benefited NASA spacecraft designers to this day.

The LDEF structure shape was a 12 sided prism (to fit the shuttle orbiter payload bay), and made entirely from stainless steel. There were 5 or 6 experiments on each of the 12 long sides and a few more on the ends. It was designed to fly with one end facing earth and the other away from earth. Attitude control of LDEF was achieved with gravity-gradient stabilization and inertial distribution to maintain three-axis stability in orbit. Therefore, propulsion or other attitude control systems were not required, making LDEF free of acceleration forces and contaminants from jet firings. There was also a magnetic/viscous damper to stop any initial oscillation after deployment.

At LDEF's launch, retrieval was scheduled for March 19, 1985, eleven months after deployment. Schedules slipped, postponing the retrieval mission first to 1986, then indefinitely due to the Challenger disaster. After 5.7 years its orbit had decayed to about 175 nautical miles and it was likely to burn up on reentry in a little over a month. It was finally recovered by Columbia on mission STS-32 on January 12, 1990. Columbia approached LDEF in such a way as to minimize possible contamination to LDEF from thruster exhaust. While LDEF was still attached to the RMS arm, an extensive 4.5 hour survey photographed each individual experiment tray, as well as larger areas. Nevertheless, shuttle operations did contaminate experiments when concerns for human comfort out-weighed important LDEF mission goals.>>

Ann wrote: ↑Sun Jan 31, 2021 10:18 am

I think - mind you, I think

Michiel van der Wulp wrote: ↑Thu Feb 04, 2021 8:44 am How come the blue line is not straight but curved?
Is the asteroid not flying in a straight line?