APOD: Asteroids in the Distance (2021 Jan 31)

[APOD Robot]

Asteroids in the Distance

Explanation: Rocks from space hit Earth every day. The larger the rock, though, the less often Earth is struck. Many kilograms of space dust pitter to Earth daily. Larger bits appear initially as a bright meteor. Baseball-sized rocks and ice-balls streak through our atmosphere daily, most evaporating quickly to nothing. Significant threats do exist for rocks near 100 meters in diameter, which strike the Earth roughly every 1000 years. An object this size could cause significant tsunamis were it to strike an ocean, potentially devastating even distant shores. A collision with a massive asteroid, over 1 km across, is more rare, occurring typically millions of years apart, but could have truly global consequences. Many asteroids remain undiscovered. In the featured image, one such asteroid -- shown by the long blue streak -- was found by chance in 1998 by the Hubble Space Telescope. A collision with a large asteroid would not affect Earth's orbit so much as raise dust that would affect Earth's climate. One likely result is a global extinction of many species of life, possibly dwarfing the ongoing extinction occurring now.

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[RocketRon]

If it doesn't happen soon-ish, the current extinction rates over the longer term may not leave much anyway ?

Back to basics first maybe though.
What are all the blues and yellows in this image ?

[Holger Nielsen]

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.

[Ann]

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.

Cyan and orange filters on Hubble detecting asteroids and cosmic rays.

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Two-filter Hubble image of galaxy NGC 2683. Either the filters used were cyan and orange, or else the filter images were mapped as cyan and orange. NASA - http://www.nasa.gov/multimedia/imagegallery/image_feature_2210.html.

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I think - mind you, I think - that the asteroid was caught by the cyan filter of Hubble. The short yellow streaks might just be asteroids caught by the orange filter of Hubble.

As for the blue and yellow "very short streaks" that are seen all over the image, I think many of them may be cosmic rays, caught by either the cyan or the orange filter.

It seems obvious that Hubble was busy taking a two-filter color image, using a cyan and an orange filter for the image. To see what such a two-filter Hubble color image might look like, I recommend the picture of galaxy NGC 2683.

Ann

[Holger Nielsen]

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.

[orin stepanek]

Rocks in Space; Earth must be getting bigger from all the impacts!

[Sa Ji Tario]

I understand that the Earth grows about 4,000 tons of dust per year that we receive by the Pointing-Robertson effect

[Chris Peterson]

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.

Also, keep in mind that cosmic rays often hit structure around the camera and create a particle cascade. We call all those artifacts in the image "cosmic ray hits", but many are the result of secondary hits. So there is a wide range of both energies and impact angles.

These are normally removed by stacking together multiple images using some kind of median processing. But when you're looking at a moving object like an asteroid, you can't do that.

[Chris Peterson]

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.

[Sa Ji Tario]

Thank you Chris

[Wadsworth]

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?

[Chris Peterson]

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?

These asteroids are not in our atmosphere. They are in orbit around the Sun, in space.

[neufer]

Explanation: Many kilograms of space dust pitter to Earth daily.

• : 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)

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.

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)

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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).>>

LDEF is removed from Columbia's payload bay

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<<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.>>

[FLPhotoCatcher]

What is the name of the asteroid? I imagine it refers to the Hubble telescope?

[FLPhotoCatcher]

Are the fuzzy black blobs gas clouds, or dead pixel patches?

[TheZuke!]

I think - mind you, I think

And therefore, you ARE!

[Michiel van der Wulp]

How come the blue line is not straight but curved?
Is the asteroid not flying in a straight line?

[Chris Peterson]

How come the blue line is not straight but curved?
Is the asteroid not flying in a straight line?

I think it's a parallax effect, a consequence of the fact that HST is imaging from low Earth orbit, tracking a sky that rotates every 95 minutes in a 28° inclination.