My Science School

What is galactic evolution?

There appears to be some evidence of a possible evolutionary progression among the types of galaxies such as normal galaxy radio galaxies, Seyfert galaxies and even some other bodies such as quasars. However, galactic evolution has not been conclusively proved and is still undergoing investigation.

 

 

 

What happens when two galaxies collide?

In spite of the colossal mass of stars and space debris contained in galaxies the mass is very highly dispersed. Though several colliding galaxies have been studied, there does not seem to be any evidence of catastrophic impact.

However, due to the tidal forces, the total masses of both galaxies are redistributed between them, though the two nuclei are comparatively less affected.

 

 

 

What is the Messier List?

The Messier List or Messier Catalogue represents the first attempt to publish a catalogue of heavenly bodies difficult to identify, and contains particular of 109 such objects including remote nebulae and galaxies. The list was prepared to forewarn astronomers who were constantly mistaking these for comets and stars.

What is the Messier Number?

The Messier Number is the identification code of a heavenly body in the Messier Catalogue. An example is the Andromeda galaxy designated as M31.

What are radio galaxies?

They are galaxies emitting a significantly large amount of radiation at radio wave frequencies though not necessarily emitting a large amount of visible light. A strong radio galaxy may be emitting radio power of up to a hundred times that of an ordinary galaxy like the Milky Way.

 

 

 

 

 

 

 

 

 

 

Continue reading "The Universe"

 

 

What is a “Nebula”?

A Nebula is a cloud of gas and dust floating in space. It is visible either as a luminous region or a dark patch against the back ground of stars.

 

 

 

 

 

What is a Planetary Nebula?

A planetary nebula is a spherical or ellipsoidal shell of gas around a white dwarf, and is formed when a red giant leaves behind an outer shell of matter while contracting.

 

 

 

 

 

 

What are the Magellanic Clouds?

In 1519, Ferdinand Magellan the navigator observed two small star clouds in the heavens, similar to the Milky Way, visible to the naked eye. These have been named after him, and are visible only from the southern hemisphere. These clouds have since been identified as satellite galaxies of our own system.

 

What is the nature of the path traced by the Earth across the Universe?

The path of the Earth across the Universe is in an elaborate series of loops and whirling spirals. A person on the Earth’s surface would move in a path governed by:

1. Rotation of the Earth about its axis at 460 meters/sec at Equator.


2. Earth’s rotation about the barycentre of the Earth-Moon System.


3. Earth’s rotation about the Sun at 30 km/sec.


4. The sun’s rotation about the Milky Way Galaxy at 220 km/sec.


5. The Milky Way Galaxy’s rotation about the Local Group of Galaxies (LGOG) towards the constellation Hercules.


6. The rotation of the LGOG about the Virgo Super Cluster of Galaxies (VSCG) towards the constellation Southern Cross.


7. The rotation of VSCG about the Universe.

 

Of the above, only items 1 to 4 are clearly known. Items 5 and 6 are still speculative while item 7 is still unknown.

 

What are open star clusters?

They are clusters of stars. In galaxies, the stars are densely packed together, whereas in open star clusters the stars are not densely packed together but only loosely associated.

 

 

 

What are globular star clusters?

They are a spherically shaped cluster of stars. Typically, it contains about ten thousand to ten million stars apparently concentrated towards the centre.

Are globular star clusters visible to the naked eye?

Only two clusters are visible to the naked eye, through more than 120 can be observed with instruments.

 

 

 

 

 

 

To what cluster of galaxies does the Milky Way Galaxy belong?

It belongs to the Local Group of Galaxies which contains about 20 galaxies including the Milky Way Galaxy, the Andromeda galaxy and the two Magellanic Clouds.

How many galaxies are there in a cluster of galaxies?

Galaxies tend to form clusters containing up to a few thousand galaxies. The Local Groups of Galaxies is a relatively small cluster of galaxies.

 

 

 

Are galactic clusters visible to the naked eye?

Yes. The Pleiades and the Hyades are examples of galactic clusters visible to the naked eye.

 

 

 

 

 

 

 

How did galactic clusters originate?

Galactic clusters are thought to have originated from the fragmentation of large gas into smaller gas clouds which in turn have formed stars. All galaxies in a galactic cluster may therefore be assumed to be of the same age. Most galactic clusters are relatively young, perhaps a few tens or hundreds of millions of years pls.

 

 

 

 

 

 

 

 

 

To what super cluster of galaxies does the Local Group of Galaxies belong?

The Local Group of Galaxies belongs to the Virgo Super Cluster of Galaxies containing thousands of galaxies.

 

What portion of the universe is influenced by gravitational force?

Gravitational force is a form of force of attraction in the Universe. Every particle of matter exerts a gravitational pull on every other particle in the Universe.

Is gravitational force variable?

In 1687, the famous British scientist Isaac Newton proved that bodies having more mass exert greater gravitational pulls and as one moves farther from the centre of a massive body, the effect of such pull decreases. For example, a person standing on the surface of the Moon would weigh less than what weighed on Earth since the gravity on the Moon’s surface is less than that on the Earth’s surface. Also if he goes away from the Earth in a rocket, his weight will go on increasing.

 

 

 

 

What is the relationship between gravity, mass, weight and density?

Mass is the amount of matter that an object contains. All objects have mass. When gravity acts on a body, the body appears to have weight. As gravity increases, weight of the body also increases but the mass of the body remains unchanged. A stone weighing 1 kg and a pillow weighing 1 kg both have the same mass and therefore the same weight, but the stone has less volume than the pillow, because the material in the stone is more density than the pillow.

 

 

 

Continue reading "The Universe"

 

 

What is cosmology?

Cosmology refers to the study of the Universe as a whole, its origin, evolution and future development.

 

 

 

 

 

 

 

 

 

 

 

What is the “Cosmic Egg”?

The concentration of matter and energy prior to the Big Bang has been nicknamed as the ‘Cosmic Egg’ – an analogy with an egg which gives birth to life.

Will the Universe continue to expand?

If the mean density of the Universe is less than a certain critical value, the rate expansion should tend to remain steady and the Universe would expand forever.

If the density is greater than the critical value, the expansion will eventually slow down and cease, followed by a contraction phase. According to the Oscillating Universe Theory, the Universe expands and contracts in a cyclic manner repeatedly.

 Is the volume of matter so far detected in the Universe likely to exceed the critical value required to substantiate the Oscillating Universe Theory?

The volume of matter detected so far is below the critical value. However, there are various types of matter in the Universe about which we have incomplete knowledge e.g., inter-galactic matter and “invisible” matter.

 

 

 

What is meant by inter-galactic matter?

Inter-galactic matter refers to the rarefied matter that exists in the space between the galaxies. Its existence has not been proved by direct observation but indirectly by interfaces.

What are the basic constituents of the “matter” in the Universe?

Matter refers to material objects. The smallest unit of matter that can exist independently as a chemical element is the atom. Groups of atoms combined together are known as molecules. The atom itself consists of a core called the “nucleus” surrounded by an outer shell containing particles called electrons.

How large is the Universe?

The Universe apparently stretches out to an infinite distance. There is however a limit as to how far we can observe the distant objects with our naked eyes or even with instruments.

How did the Universe originate?

It is believed by most astronomers that all the matter and energy was once concentrated at one point and there was then a cataclysmic explosion in which matter and energy were scattered in all directions. The matter later coalesced into galaxies and other celestial objects to from the Universe as existing now.

 

 

What is the Big Bang?

The cataclysmic explosion at the time of the birth of the Universe has been nicknamed as the “Big Bang”. The analogy is to a bomb which bursts with a bang and scatters fragments at random.

Is there any observational evidence in support of the Big Bang theory of the origin of the Universe?

According to the Big Bang theory, there must be some very weak background microwave radiation across the Universe as are result of the Big Bang. In 1965, the manifestation of such microwave radiation approaching is from all directions was discovered thereby providing evidence in support of the Big Bang theory.

Is the Universe now expanding, shrinking or steady in volume?

Astronomical observations have inferred that the matter scattered by the Big Bang continuous to fly off in all directions confirming the continuing expansion of the Universe.