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Hubble watches an asteroid begin to rip

The asteroid belt between Mars and Jupiter orbits a rock called 6478 Gault. It is about 4-9 kilometers wide (it can be difficult to determine the exact size of the asteroids), which is quite typical. The orbit is somewhat unusual, being more elliptical and inclined than most asteroids, but that's no big deal.

What is . One big thing is that it seems to rip itself off. [19659002] Gault observations taken on 5 January 2019 by the ATLAS Telescopes in Hawaii showed that it had just grown a tail! Also a long, at least 400,000 kilometers long track – more than the distance of the moon from the earth.

But when did it happen? How long before these observations has the tail formed? The astronomers looked at older data from ATLAS and Pan-STARRS (a large telescope that performs surveys of great cardinal directions) and found that the tail was visible on Gault in early December. They looked further back and saw no evidence of a tail in observations from 201

0 to January 2018 (after that the asteroid was too close to the sun in the sky until the end of the year to see it).

Asteroids Sometimes After being hit by another, smaller asteroid, tails formed so Hubble went into action to see if the tail showed any signs that he was forming like this. To their surprise, the astronomers saw a second tail from Gault!

The second tail was shorter, narrower and more defined than the first, suggesting that he was younger. This is because the pressure from sunlight tends to atomize small particles hard enough to disperse them quickly, making the tail fuzzier.

Using models of how dust moves in these situations, the astronomers estimated the first tail to be around October 26, 2018 and the second on December 30. This makes an impact scenario unlikely. It is quite rare to be hit hard enough to eject a cloud of dust, so it is a bet that no astronomer covers if he has a second second within weeks of the first impact.

Could this be a disguised comet? Maybe a really old one that does not have much ice in it, but somehow suffered an event in which part of the remaining ice suddenly became warm, turned to gas, and emitted dust? Maybe it was a little farther out in the solar system, and Jupiter's gravity recently brought him into his present path.

The astronomers carried out simulations on Gault's orbit and found that it was stable, even after projecting the future after 100 million years. Therefore, it is unlikely that they are interloper lately. We have seen many comets that were affected by Jupiter, and they do not last long. It is much more likely that it was in its current orbit for a long time.

What is going on then?


The effect of Yarkovsky, O'Keefe, Radzievskii and Paddack. I've already written about it, so I'll leave it to myself:

A very strange but important concept in physics is that while the light does not have mass, it does have an impulse . When sunlight strikes an asteroid, the asteroid heats up and emits this heat as infrared light. If the asteroid were perfectly spherical and not rotating, the only effect would be to push the asteroid farther away from the sun (think of a very gentle breeze blowing on the asteroid giving it a tiny push). 19659013] However, if the asteroid rotates or has an irregular surface (which of course is the case, they have craters and pits and cracks, etc.), then the light emitted by it can be sent away at an angle producing a small one Torque, making the asteroid spin faster. Over time, the rotation of the asteroid can change significantly! It depends on many things, such as the exact shape of the asteroid, how reflective it is, how close it is to the sun, and more. This process is referred to as the YORP effect because it was dreamed by scientists named Yarkovsky, O'Keefe, Radzievskii and Paddack . Turn

faster. In the short term, this is not a big deal, but in the long run, this is a disaster: At some point, the stone rotates so fast that the centrifugal force outwardly balanced on its surface, the gravity inside. If you are a stone sitting on the surface, the asteroid will rotate faster over time, and you will feel less and less weightless. They weigh less!

This changes the stress and pressure of cairns on the surface. Sometime something has to give and you get a little landslide. Boulders, stones, pebbles and smaller dust grains fall down under the light gravity. The smallest dust grains gain the most energy as things move and jostle, and they get the highest speed that can easily exceed the escape speed of a small asteroid. This dust literally leaves the surface and forms a cloud around the asteroid. The pressure of sunlight blows it away and creates a tail.

Is this happening to Gault? Observations from the ground point to a rotation speed of about 2 hours, and it turns out that this is almost exactly the point at which the rotation speed is to be expected. In addition, the dust leaves the asteroid relatively slowly at speeds less than one meter per second (less than the walking speed). This is also what one would expect from dust thrown from a landward side into space (and the speed of rotation of the asteroid on the surface near the equator is about 2 meters per second, which also gives the dust a kick). By the way The amount of material in the tails is not much: 7 million tons in the first and 40,000 tons in the second tail.

I know that sounds like a lot, but they are just 82 and 14 meters in diameter; Compared to an asteroid that is several kilometers wide.

It all adds up: Gault was whirled up by the ethereal breeze of sunlight and is now very close to the point where he is flying apart. We do not know how long that will take – it depends on many factors that are difficult or impossible to measure, such as how dense it is, how big it is, how the surface is and even how fast its rotation accelerates up (which To be honest, not impossible to measure is very difficult).

It is estimated that approximately one asteroid in the main belt will burst by itself every year! While we do not know when Gault will destroy himself, we can be pretty sure there will inevitably be these legions of debris fields. 19659002 so easy to see. Small ones usually go first, and they can be incredibly weak, even if they disperse and form a cloud of dust, they only get a little brighter. Maybe that's why we do not see many … but we see them. For example, P / 2013 R3 broke apart in 2013. As the telescopes get better and we scan more from the sky, you can expect to see more.

In the meantime, you can be sure that the astronomers will keep an eye on Gault. We can watch an asteroid destroy itself in real time, and that's too cool to miss.

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