After this, a main sequence star will continue emitting light and heat energy until it consumes all of its limited supply of hydrogen in its core. Then it will become redder, larger and luminous as it becomes a red giant star. At this stage, its outer envelopes will collapse and expand consuming nearby objects like planets, meteors and other heavenly objects.

It will continue to collapse its outer envelope and will even intensity its hotness is it exhausts the helium in its core, becoming a red super giant. It will eventually lose all of its mass and will leave a remnant of a hot core of carbon within a nebula of expelled gas. In some instances, the radiation from this hot core ionizes a nebula to produce a planetary nebula. But in most cases, the core of carbon cools down to become a white dwarf, a star that is relatively dim as compared to what it once was, a bright star and this ends its stellar evolution until it becomes black dwarf or a burned out star.

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But what is relativity all about and how was it able to answer these questions? We can begin with what Einstein came up with, the idea that if we are to believe that the natural laws of the universe are absolute and true then they must be true under all circumstances and at all times. According to him, this is only made possible when elements such as space, time, matter, and energy are altered or are changed constantly in order to present us with the same circumstance every time. Applying that to observations of the universe, he supposes that even empty space can contract or expand depending on the position of the person observing it.

In astronomy, relativity has found its place especially when observing or studying objects that move in a strong gravitational field as well as those that are moving near the speed of light.

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The speculation about this celestial body exists even long before. The existence of these systems was confirmed in 1994 when Robert O’ Dell and his co-workers from the Rice University, through the use of the Hubble Space Telescope examined newborn stars in Orion Nebula.

According to the theory, it requires at least ten million earth years for a planetary system to be fully established and planets to fully form, through the combining of gas and dust clumping or forming together as one. In 1999, a certain protoplanetary disk was found in the Taurus portion of the galaxy, and it seemed that 6 young planets are surrounded by space gas and dust, indicating a formation of a new star system. Apart from this, it was also concluded that since the said disk was near the solar system, it also means that another star system can form at any time, in between another star system as well.

Furthermore, the protoplanetary disk is said to have a mass of 0.01 to 0.1 solar mass according to results found on newborn planets or stars. On the contrary, the results gained a discrepancy since the mass of a certain star system varies according to cumulative planetary and star masses.

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Not all planetesimals merge on collision. Some are unlucky enough to break apart on impact. The one that are lucky enough to survive will eventually grow to approximately one kilometer in size when it can then attract each other to form even larger bodies. This process continues until the accumulation of matter forms into a moon or eventually a planet.

Components of planetesimals vary depending on their distance from the sun. The inner portion of the solar nebula is hot, thus the planetesimals that grow are mostly composed of metals and silicates. The outer portion of the solar nebula is much cooler, thus allowing the formation of planetesimals made mostly of water ice. This can account for the fact that the gas giants in the outer portion of our solar system are mostly composed of gas and liquid cores.

The term planetesimals is also used by some scientists when referring to asteroids, comets and other small astronomical objects that are believed to be debris produced by the planetary formation process.

Planetesimals provide scientists with valuable material from when they were first formed, which is key to further studies on the condition of the solar nebulae around the time our solar system was formed.

Planetisimal Theory

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Extragalactic astronomy is a branch of astronomy concerning all other astronomical objects outside our own galaxy, the Milky Way Galaxy. Study methods have improved over the years, thanks to the new technology we have at our disposal. More distant objects can be examined with more detail and understanding.

We know that our planet, and the whole solar system, resides in the Milky Way. But what else lies beyond the darkness? We know, thanks to astronomical instruments like the Hubble telescope, that the universe consists of 500 billion planets, 200 to 400 billion stars and 100 to 200 billion galaxies. With that big a number, chances are huge for forms of life and many scientists believe that there may be one or more intelligent forms of life other than in planet Earth.

The extragalactic exploration continues to in unknown territory. Astronomers engage in further studies to advance what we need to know about the universe.

Extragalactic Objects Through Hubble

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Are we really alone? According to the latest study, most people in the United States (more than 60% of the study) believe in extraterrestrial life. The universe is just too big for Earth to be the sole planet to support life. In fact, we can look to

Astrobiology, a study of possible life outside Earth, is an authentic and formalized field of science. NASA has funded programs to find extraterrestrial life in the universe. So far, the science has still a lot to learn and discover, and we can only speculate for now.

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There are also several mid-sized lightweight planets, just a few times larger than our beloved planet Earth. Most extrasolar planets rotate around stars, but there are also planets that orbit around brown dwarfs and planets that do not orbit on any body at all, floating freely to space.

Because of the discovery of many extrasolar planets, the interest in the possibility of extraterrestrial life has intensified in the field of science and astronomy. Various missions and projects have been made to determine if there is extraterrestrial life on these planets.

Astronomers have found two possible candidates that may hold extraterrestrial life: red dwarf planets Gliese 581 and Gliese 581 D. These planets have many Earth like qualities so possibility of life here is high. Because of this, scientists have sent a message to Gliese 581. Being 20.3 light years away from earth, the message is estimated to arrive by year 2029 and response, if ever there will be, will not come until year 2049.

ExtraSolar Planets

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Interstellar Medium

Most mediums in outer space are gas and space dust that have varying densities. One fact is that 15% of the visible material in the Milky Way is made up of interstellar gas and dust. Most gases present in this type of space gas or matter are primarily made up of Hydrogen as its main element. It can either be in molecular or ionized forms, and is easy to use since it only has a volume of 1 atom per cubic meter. The gas form may be easy to handle, the thing is that the gas levels add up due to the vast and wide distances between star systems.

Interstellar mediums, mainly dust on the other hand, is not just average dust. It contains different substances and is extremely small or tiny. These particles are also irregularly shaped and are made of different elements, most likely iron or ice.

Picture this, Interstellar Medium

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At the boundary of the heliosphere is the heliopause. This is supposed to be about 10 billion miles from the Sun. Its real distance though has not been exactly determined because it varies with the velocity of solar wind and the density of interstellar medium. The heliopause separates the solar system from other interstellar space. It is in this part of the Solar system that the charged particles from the Sun bump into the particles from other stars.

Inside the heliopause is the so-called termination shock. Due to the effect of particles from other stars, the solar wind in this region is slower than the speed of sound. The effect of these particles can cause some changes in the magnetic field, heating and compression. Finally, Heliosheath refers to the region between the heliopause and the termination shock.

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H= v/d

Where H is the Hubble’s constant, v refers to galaxy’s radial outward velocity or speed and d is the distance from the Earth. Based on this relationship, the farther the galaxy, the faster it is moving away from Earth. It is not easy to determine the exact value of Hubble constant. This is because the two quantities required are difficult to measure especially the exact distance of a galaxy from the Earth. The current value of this constant as calculated by Edwin Hubble as 500 km/s/Mpc or 500 kilometer per second per megaparsec.

Hubble’s Law is very important in astronomy and cosmology. It was the first concrete support for Einstein’s theory of Relativity being applied to the universe. The determined value of Hubble’s constant can be used to estimate an age of the universe. It also helps validate theories of Dark matter and Dark energy. A recent discovery in 1998 revealed that the expansion of the universe is accelerating.

Hubbles Law

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