General Astronomy 🔭 (genastronomy.blogspot.com): 10/18/22

Tuesday, October 18, 2022

What Are Asteroids And Where Do They Come From?

One of the most well-known theories concerning the death of the dinosaurs argues that these ancient creatures went extinct when a large stone from space slammed into Earth.
Through a series of events, this ultimately led to the extinction of dinosaurs.
You have probably heard countless stories and hypotheses regarding the disastrous consequences of an asteroid strike on Earth, but what exactly are asteroids?
Where do they come from?
And most importantly, could they really obliterate the entire planet if they were to strike Earth with enough force?
An asteroid is a small, rocky object that orbits the sun, just like the rest of the planets and celestial bodies in our solar system.
Although asteroids are present throughout the solar system, most of them live in the asteroid belt—a region located between the orbits of Mars and Jupiter.
The size of objects within the asteroid belt have a wide range, from being no bigger than a dust particle to almost a thousand kilometers wide.
In fact, the largest asteroid present in the asteroid belt—Ceres—is 940 kilometers wide and is considered a dwarf planet.
Although the asteroid belt hosts a multitude of asteroids, it’s not the only region where these rocky objects hang around.
Some asteroids are also found in the orbits of planets, which means that the planet and the asteroid circle the sun on the same elliptical path.
Earth and a few other planets have asteroids like this.
For some, a more interesting question is, how did these asteroids come into being?
Our solar system came into existence about 4.6 billion years ago when a large cloud of gas and dust collapsed.
Following this event, most of that material fell to the center of the cloud and resulted in the formation of the sun—the central star of our solar system.
Planets were formed from some of the condensing dust in that cloud, but not all celestial material had the chance to be incorporated into planets.
The leftovers from that time took the form of asteroids.
Asteroids vary greatly in terms of their shape and size.
An asteroid can be as large as Ceres, nearly a thousand kilometers wide.
On the other end of the spectrum, the smallest asteroid ever studied is a space rock called 2015 TC25.
It’s 2 meters wide and was observed when it made a close flyby of Earth in October 2015.
Almost all asteroids are irregularly shaped, although a few big ones, like Ceres, are nearly spherical.
Asteroids are also cratered or pitted, and their surface is thought to be covered in dust.
Asteroids orbit the sun in elliptical orbits, but additionally, they also rotate, sometimes tumbling haphazardly through space.
They may even have their own moons! We know of more than 150 asteroids that have a small companion moon, and some have more than one! Asteroids are found in three main regions of our solar system.
A significant amount of asteroids are found in the Asteroid belt, which lies between Mars and Jupiter.
Then there are Trojan asteroids—a large group of asteroids that share the orbit of planets around the Sun.
Jupiter Trojans are the most well-known and numerous Trojans.
The total number of Jupiter trojans larger than 1 km in diameter is believed to be about 1 million! Finally, there are Near Earth Asteroids, or NEAs.
These circle closer to Earth than the sun.
It is believed that nearly 10,000 of all known asteroids are NEAs.
Asteroids are known to be composed of clay and rocks, as well as metals like nickel and iron.
Now, since some asteroids are very close to Earth, in comparison to other celestial bodies, Is it possible for them to slam into our planet?
Absolutely! Ever since Earth came into being, it has been struck relentlessly by asteroids and comets.
In fact, the most popular theory regarding the extinction of dinosaurs is related to an asteroid that slammed into Earth, causing widespread destruction, obliterating most life forms in the global aftermath.
Although many celestial objects approach our planet, a significant number of them get burned up in the atmosphere and never make it to Earth’s surface.
According to NASA, space rocks smaller than 25 meters will most likely burn up as they enter Earth's atmosphere.
However, some larger asteroids do make it through the atmosphere and impact our planet’s surface.
In 2013, an asteroid slammed into the atmosphere over the Russian city of Chelyabinsk.
The shock wave created by this event injured 1,200 people.
An asteroid capable of causing a global apocalypse would have to be more than 400 meters wide.
Impact from such an asteroid would cause massive destruction of both life and property on a global scale.
Fortunately, asteroids that huge strike Earth an average of once every 1000 centuries.
All in all, asteroids can and do orbit near our planet, but most will never approach Earth, and even if they do, they usually get burned up in the atmosphere before ever making contact with our planetary surface.

Student Mistakes

A greenhouse gas (GHG or GhG) is a gas that absorbs and emits radiant energy within the thermal infrared range, causing the greenhouse effect.
The primary greenhouse gases in Earth's atmosphere are water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O₃).
Without greenhouse gases, the average temperature of Earth's surface would be about −18 °C (0 °F), rather than the present average of 15 °C (59 °F).
The atmospheres of Venus, Mars and Titan also contain greenhouse gases.

Answer: 1.12E2

Do not enter ±1%.
One percent here is the range of answers that the test system evaluates as correct. Deviation of the student's answer from the correct value by less than one percent is not considered an error.

Here's the general rule for rounding:

If the number you are rounding is followed by 5, 6, 7, 8, or 9, round the number up.

Example: 1.235 rounded to the 3 significant figures is 1.24

If the number you are rounding is followed by 0, 1, 2, 3, or 4, round the number down.

Example: 1.234 rounded to the 3 significant figures is 1.23

From the hint, use radii: the radius of the Earth is 1 radius of the Earth. The radius of Jupiter is equal to 11.19 radii of the Earth. Calculate the ratio: 11.19 / 1 = 11.19

Don't convert the result from regular notation to scientific notation, as this question doesn't have that requirement.

If the diameter of the first spherical object is 3 times the diameter of the second spherical object, then how many times the volume of the first object is greater than the second.

Hint

Given Answer:	3
Correct Answer:	27

Solution
From the hint:

Then:
V₁/V₂ = (πd₁³/6) / (πd₂³/6) = d₁³/d₂³ = (d₁/d₂)³ = 3³ = 3⨯3⨯3 = 27

The orbital period of a satellite is the time it takes for it to complete one revolution around the Earth. Since the satellite is geostationary, this means that this time must be equal to the time of one rotation of the Earth around the Earth's axis of rotation, but it must be observed relative to the stars. So, the answer is a sidereal day. But we know (see the hint) that a sidereal day is about 4 minutes shorter than a solar day. So the answer is: 24 hours - 4 minutes = 23 hours 56 minutes.