Space Rocks: Asteroids, meteoroids and comets

Our Solar System is not just made up of planets, dwarf planets and moons. There are lots of other objects that make up the solar system family. There are some objects like Space rocks which have existed since the solar system formed and they have hit earth in the past 4.6 billion years ago. space rocks are all debris remaining from the nebula from which the solar system formed.

Space rocks are known by different names depending on their size. There are mainly 3 types of space rocks: Asteroids, meteoroids, comets.

ASTEROIDS

Rocky celestial objects that orbit around the Sun which are much smaller than planets are called asteroids. In our solar system, most of the asteroids located in a region called asteroid belt which lies between the orbit of Mars and Jupitor.

FEATURES AND TYPES:-

Asteroids are normally irregular in shape but some of them are spherical in shape. The average temp of the surface of the asteroid is -100° Farenheit.

These rocks have different shapes and structures. Some of them are solid bodies some are like rubber piles, some have tails and some other have own rings like structure.

Mainly asteroids are 1000km in diameter. Some are less than 1 km (0.6 miles) wide.

Asteroids are much smaller than planets called planetoids. According to size, there are millions of asteroids. Some asteroid have moons. The asteroid Ida has a moon called Dactyl.

  Orbit of Dactyl around Ida (Source: NASA/JPL-Dactyl potential 

Asteroids can be classified on the basis of their characteristic spectra and compositions. There are mainly 3 types of catagories.

C-type: Carbon-rich:-

             These asteroids are rich in carbon and dark, gyrish in colour. Most asteroid belongs to this group i.e about 75% of known asteroid belongs to this category.

The largest of this group was 10 Hygiea with a diameter of about 434 km.

The brightest of this group found was 324 Bamberga with wavelength below 0.4 μm.

These group is also divided into different sub-groups:) B-type, F-type and G –type.

Ceres is the largest known asteroid till date which belongs to G-type of this catagory with a diameter of 945 km.

M-type: Metallic:-

These asteroids are made up of metals like nickel, iron and have moderately bright in structure. Most of these asteroid resist on the middle of the asteroid belt.

The most massive asteroid of this group is 16 Psyche with a diameter 200 km. This was found by an Italian astronomer Annibale de Gasparis in the year 1852.

Another of this group is named as 216 Kleopatra i.e like dog-bone shape appearance.

 S-type: Silicate:-

These group asteroids consist of stony, silicate, mineral compositions and their main constituents are iron silicates and magnesium silicate. Very few asteroids belongs to this category i.e approximately 15-17% belongs to this group.

These are located in the inner part of the asteroid belt.

Largest known asteroid of this group till date is 15 Eunomia with a diameter 330 km.

ASTEROID DAY:- 30 June 

Recently Detected Asteroid:-

In 29^th April 2020, a big spherical asteroid named (52768) 1998 OR2 passed close to Earth this year.

This asteroid was first observed on 24^th July 1998 by the astronomers from Haleakala Observatory. Study confirms that asteroid  was about 2 km in diameter and rotates once in every 4.1 hours. This is one of the Near Earth asteroids (NEAs) of the group Amor asteroids.

Radius: 1.03 km

Orbital period : 1344 days

Group : Amor asteroid

 METEOROIDS

A small piece of rock or space dust that has broken off an asteroid or comet is called a meteoroid. If a meteoroid enters the Earth’s atmosphere and heated by friction and appears as a glowing streak of light called meteor, which is also called as “shooting star”. Most meteoroids burn up in the atmosphere. The remnants of the few of that are large enough to reach the Earth’s surface are called meteorites.

Everyday around 90 tonnes of rock and dust from space smashes into the Earth. Most of it burns up in the atmosphere, but larger objects can reach the ground. Scientists think a meteorite about 10 km (6 miles) wide hit into the Earth about 65 million years ago, wiping out the dinosaurs.

FEATURES AND TYPES:-

Meteoroids are small chunks of stone or iron and stone which are mainly the fragments of asteroids and comets. These range in size from tiny dust particles to objects of tens of meters across.

 Types of Meteorites:-

Iron meteorites:- Made of metals (mainly Iron)

Structure of this is very similar to the terrestrial planets( Mercury, Venus, Mars, Earth) which also have metallic cores.

Stony meteorites:- Composed of silicate materials (Chrondites and achrondites are the two main types of stony meteorites)

Chrondites consist of some oldest matters of our solar system where as achrondites include meteorites from asteroid , moon and mars.

Stony-iron meteorites:- consist of equal amount of metal and silicate crystals.

These are most beautiful meteorites divided into two distinct groups:) Pallasites and mesosiderites.

Pallasites are big olive-green crystals beautiful in shape. Researchers belive that they formrd from melted asteroids. Mesosiderites form when debris from a collision of two asteroids mixed together.

Meteor Shower-:

Due to streams of cosmic debries of meteoroids entering on Earth's orbit, a number of meteor originate at one point in the sky radiating light with high speed on parallel trajectories seems shower like structure called meteor shower.

Leonids meteor Shower was the greatest shower of all time. It was named according to it's constellation Leo. These are one of the distinct meteor shower famous for their spectacular meteor storms that occur every 33 years.

Leonid meteor Shower in 1966 (Image Credit-NASA)

First Discovery Date: 902 AD

Constellation : Leo

Parental body : 55P/Temple-Tuttle

COMETS

Comets are made from rock, volatile ice and dust materials, dusty snowball like structure which orbit the sun. There are thousands of billions of comets in our solar system which have the size of mountains.

The word comets came from greek word “Kometes” which means long haired. They range from a mile to tens of miles wide and they heat up when they orbit around the sun.

Structure of a comet (Credit-ESA)

 FEATURES AND TYPES:-

 Comets consist of a nucleus, coma, a ion or gas tail and a dust tail.The center or nucleus of comets are icy in nature which is surrounded by cloud of gas and dust like materials called coma. Comets have eccentric elliptical orbits and have wide range of orbital periods.

Comets are divided into long period comets and short period comets.  Normally short period comets originate in Kuiper Belt and have orbital period of less than 200 years. Long period comets are originated in the Oort cloud and orbital period ranges about thousands of years. Halley’s comet is one of the short period comet of about 75-76 years of orbital period.

 Comets travel around the sun in an oval-shaped orbit. Some comets are so far away that they take tens of millions of years to orbit the sun Comets get tail when they pass near the sun are heated up. The tails always point away from the Sun. Comets develop two tails when they travel close to the sun:) a straight gas tail and a curved dusty tail.

Recently Detected Comet:-

One of the brightest comet of decade named comet C/2020 F3 passed close to Earth on 22^nd july of this year. The comet called Neowise was first detected on 27^th march by NASA’s near Earth Object wide-field Infrared Survey explorer.

Track and positions of Neowise (Credit- JPL Small-Body Browser)

The speed of the comet was about 40 miles per second. Unique feature of the comet is that it had a division of it’s ion tail observed by Parker solar probe. It had two ion tains including a dust tail.

Radius :- 3 miles

Orbit type:- Long period comet

Current constellation:- Libra

All these space rocks can be indicated in large region most preferably in desert areas or in baren regions . Researchers also use ice regions like some parts of Antarctica to spot space rocks. 

Have you ever seen any of these kind of space rocks ?  Which of these space rocks you like to observe? Comment below!!