Celestial objects are usually referred to as Astronomical Objects or Bodies. This term refers to the outer space physical units, associations or formations. Usually, a celestial body is a single entity or unified structure that is joined together by the virtue of a gravitational force like Earth, Moon, Sun, other planets, stars etc. A celestial object / body might be a single body, star huddle or a whole galaxy. Usually, a telescope is needed to view astronomical objects, but there are certain such celestial bodies that are visible even with naked eye. Some of these are huge and close enough to be seen with naked eye like Sun and Moon; others require great eyesight and perfect climate and weather conditions like planets. In this article, I will tell you about some celestial objects that can be seen with naked eye without any difficulty. Let us expand our knowledge.

1. Sun:

Sun is the nearest star to our planet, and this is why we can see it at day without any difficulty at all. In fact, we see with its help in the day time! This certainly isn’t the brightest star of our galaxy; it only is the closest and this is why we do not see other stars in the daytime. In the night, this huge celestial body shines on the other side of the Earth, thus we see stars which are far far away from our planet.

Here are some factual details about this huge star.

• Diameter: 1,392,000 kilometers (109 times diameter of the earth)
• Mass: 2 × 1030 (3,30,000 times mass of the earth)
• Mean distance form the earth: 1.496×108 km
• Hydrogen cover ¾ mass of the sun, left mass consists of helium and very little heavier elements for instance oxygen, iron, carbon etc.

As we all now, it is the centre of our solar system. Every planet of the solar system revolves around this huge bright star. It is a white star, but seems yellow due to the atmospheric scattering of blue light. The surface temperature of sun is around 5505 degree C. It comprises of almost 99.8632% of the total mass of our solar system. A lot of magnetic activity keeps on going on the sun. Its strong magnetic field changes from year to year. After every eleven years, the magnetic field reverses its direction around the solar maximum. This strong magnetic field of the sun is responsible for solar activity like solar flares, solar wind variations and sunspots. Solar activity has, supposedly, played vital role in the formation as well as evolution of the whole solar system. Also, it is responsible for changes in earth’s outer atmosphere, auroras on earth, as well as interrupted radio communication and electric power.

According to what we have been told, this great star was created 4.57 billion years ago due to collapsing of a hydrogen molecular cloud. Looking at the sun directly causes pain and sometimes it can be harmful. Also, viewing a solar eclipse directly can cause serious damage to the eyes of the viewer. Direct exposure to the sunrays is harmful and can cause grave skin ailments. For this purpose, sun blocks and sunscreens are advised to be applied before going out. Sunrays are also being used to produce energy called Solar Energy.

2. Moon:

Moon is a natural satellite, and is the only one Earth possesses. This is the fifth largest natural satellite of our solar system. We can see the moon with naked eye in when the sun sets. Sometimes, we can see it even in the daytime. The moon; though has a very dark surface, is the most bright object in the sky after sun. Its rotation is pretty much synchronized with that of the earth, and this is the reason that we always see the same “face” of moon always. It is also the only celestial object on which humans have landed. Many unmanned spacecrafts have been sent to this natural satellite for further studies. It is the second densest satellite in the solar system, following “Lo”.

Its movement is pretty interesting. In the beginning, it had faster rotation pace, but gravitational forces brought it to a steady speed. The moon takes almost the same time in rotating about its axis as revolving around the earth. Therefore, we always see the same side of the moon called “near side”. The other darker side of the moon is called “far side.”

There are some dark spots that we see on the surface of the moon. These are called “Maria”, which are hardened pools of very old basaltic lava. Maria cover almost 31% of the near side surface, whereas only 2% of the far side surface. Other light colored areas are called “Terrae.” Due to collision of comets and asteroids, various impact craters have been formed on the surface of the moon. Moon is responsible for the high tides in seas and rivers. It is the reason of solar eclipses; which happen when the moon comes in between the sun and the earth. Lunar eclipse occurs when the earth comes in between the sun and the moon, and sun becomes unable to provide illumination to the moon. Thus, we see a lunar eclipse.

It possesses a high status when it comes to cultural mythologies. A calendar is also associated with its name, specifically; the Lunar Calendar.

3. Comet:

Anciently considered as a bad omen when sighted; comets have been observed since old times. It is a small solar system body (SSSB); such object of the solar system which is neither a planet nor a dwarf planet. This is an icy SSSB. It can usually be seen with a tail, due to solar radiations and winds affecting its nucleus. This is why its coma and tail can be seen when it comes close to the sun. These two features distinguishes it form an asteroid. The nucleus is composed of ice, dust, rock and frozen gases. The surface is mostly dry, rocky and dusty. Inner side is believed to be icy.

When a comet is in the outer solar system; it remains unnoticeable. When it reaches the inner solar system, an atmosphere of its own is created around it due to solar wind and radiation. This atmosphere is called coma. The tail is created due to the pressure that is exerted on the coma by solar radiation and wind.

4. Meteoroid:

It is a particle of debris in the solar system, which can be of various sizes. When this debris made celestial object enters the earth’s atmosphere, it transforms into an observable band of light called “Meteor.” It becomes a Fireball when it is brighter than any planet. When the magnitude of a Fireball reaches -14 or brighter, it is called Bolide. A Bolide turns into Superbolide when the magnitude reaches -17 or brighter. A Meteorite is such a meteoroid or asteroid which reaches the surface of the earth undestroyed.

5. Star:

It is a radiant and shining round structure made up of plasma. It is held together by the virtue of gravity. Sun is a star which is visible in the day. Other stars are far away from us and can be seen only in the night; when sun has set. These glittering balls beautify the sky and add up to the charisma of night.

“This black hole is actually pushing the limits,” said Nikolai Shaposhnikov, the study team leader of NASA. “Scientists were working hard for many years to find out the smallest possible size of a black hole, and this invention is a big step towards answering that question,” he said in a statement.

Though it is smaller, it seems to be stronger than other larger black holes found at the centers of galaxies. If anyone goes nearer to J1650 (the name given to the black hole), its gravity would stretch your body into a “strand of spaghetti,” said Shaposhnikov.

This small black hole was once a star that has exhausted all its fuel and it eventually collapsed and shut down due to its own gravity.

This small black hole is situated in the XTE J1650-500 binary system of the constellation Ara of our Milky Way galaxy. With the help of NASA’s Rossi X-ray Timing Explorer satellite, Shaposhnikov and his colleague Lev Titarchuk found out a new method to estimate the size of the black hole.

“Based on the equations of Albert Einstein, a black hole having 3.8 times the mass of our Sun would be only 15 miles in diameter,” NASA said.”The invention of this new black hole makes the smallest object ever discovered outside our solar system,” said Shaposhnikov.

The smallest black hole which was identified earlier was GRO 1655-40, which weighs approximately 6.3 times the mass of the Sun.

A collapsed star smaller than J1650, would likely to form a neutron star and not a black hole, said the scientists.

Black holes can’t be seen and they’re identified by observing the activities taking place around them. Astronomers weigh the mass of black holes by using a relationship between the apparent size of the black hole and the X-rays emitted by the inundation of gas that twirl’s into the black hole’s disk from its neighboring star.

As the gas piles up near the black hole, it “becomes very dense and congested,” said Shaposhnikov in a press conference. “Therefore the matter cannot easily enter it has to squeeze into the black hole.”

Since the matter is squeezed, the gas gets heated up and emits X-rays.“This new invention is a big milestone for us that bring us much closer to the theoretically calculated limit,” said Shaposhnikov.

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The Cassini spacecraft had detected a large debris disk which appeared to be like rings around the 950-mile-wide moon Rhea. Scientists firmly believe that the discs are composed of particles ranging from the size of pebbles to big rocks.

In contrast to the rings around Jupiter, Saturn, Uranus and Neptune, the alleged arcs around Rhea remain invisible and cannot be seen directly. Scientists confirmed the existence of arcs based on the measurements made by Cassini, which detected a fall in electrons on both sides of the moon, indicating that the existence of rings was absorbing the electrons.

This is an artist concept of the ring of debris that may orbit Saturn’s second-largest moon, Rhea. The suggested disk of solid material is exaggerated in density here for clarity.

Credit: NASA/JPL/JHUAPL

It’s uncertain that when the rings would have originated, one thing is certain that they originated as a result of a collision of an asteroid or comet which took place long ago that disgorged the debris around Rhea.

“There is also possibility that rings might have formed even at the time of Rhea’s formation,” said Geraint Jones, a space physicist from University College of London.

Till now, we were known that only planets have rings, added Jones, who began the research while at the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany.

The Cassini mission, which was a joint effort by NASA and the space agencies of Italy and Europe, was launched into space in 1997. The spacecraft reached Saturn in 2004. The mission is controlled by NASA’s Jet Propulsion Laboratory in Pasadena.

“It is the first time to detect a moon having rings around it”, said the National Aeronautics and Space Administration.

Rhea, which is having a diameter of about 1500 kilometers, is the second-largest moon of Saturn. Cassini detected alleged arcs of debris which stretches several thousand miles from end to end said NASA.

“After excluding many other possibilities, we said these discs have similarities of rings,” said Jones. “No one might have expected rings around a moon.”

Cassini is the first spacecraft to explore the Saturn system of rings and moons from orbit.

‘Until now we believed that Saturn was the only planet having rings,’ said a scientist of Cassini mission. “Now we also have a moon of Saturn which seems to be a miniature version of it even more elaborately decorated parent.”

Relevant Links:

• Saturn’s Moon Rhea Also May Have Rings
• http://www.nasa.gov/mission_pages/cassini/media/rhea20080306.html

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They said that the new technique known as microlensing is very promising and can be used for many more stars with earth like Stars revolving around them.

Scott Gaudi, who led the study, said “We discovered a new solar system that appears similar to the solar system in which we live”

Using the technique of gravitational microlensing, a network of astronomers around the world from about 11 countries spotted the system that comprises two planets that are revolving around a star known as OGLE-2006-BLG-109L, which is about 1/2 the size of our sun and about 5,000 light years away.

“Microlensing technique works by making use of the gravity of the star as well as the Planet to bend and focus light rays from a Star in the background“, – said Scott Gaudi of Ohio State University. “If you are looking at a Star, and another goes by in the foreground will focus and bend light rays. This causes the magnification of the Star in the background.” – He added.

“Any planet revolving around the Star causes “a little bump” in the magnification effect,” Gaudi said.

The two planets in the new solar system are smaller than Saturn and Jupiter. The larger planet is slightly smaller than the Jupiter, with close to 70 percent of Jupiter’s mass. The smaller planet is about 30 percent of the mass of Jupiter, which makes it similar in size with Saturn.

Moreover, the two Planets are much nearer to their parent Star. The bigger planet is 2.3 astronomical units (AU) from its parent Star where as the smaller one is about 4.6 AUs from its Sun. In contrast to this in our solar system the Jupiter lies about 5.2 AUs from the sun while the Saturn is at a 9.5 Astronomical Units away from our sun.

The Sun i.e. the parent Star of the new solar system is dimmer than that of ours. However the temperatures in the two planets are similar to that of Jupiter and Saturn. This is because the planets are closer to their star than Jupiter and Saturn to our Sun.

The two planets are only the 5th and 6th identified using gravitational microlensing. “This is the first time a planet with Jupiter’s mass was identified where we had notable sensitivity to more planets. We may be able to find a full census of planetary systems in all over our galaxy,” – said Scott Gaudi.

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