Comet ISON - Will it dazzle Earthlings?
Expected to put on a dazzling celestial show, Comet ISON's close encounter with the Sun on 28th November will determine its fate.
Night sky and its wonders
A stargazing session on a clear, moonless sky has the potential to make you spellbound. Here is a list of things to watch out for in the night sky.
Planet Venus. Source: Stellarium
The planets Mercury, Venus, Mars, Jupiter and Saturn can be seen with the naked eye. Planets do not product light by themselves, they reflect the light from the Sun.
The brightness of a planet as seen from Earth varies over time. And you might not be able to see all the five planets on a single day.
A meteor streak. Source: Stellarium
A meteor is a streak of light caused by the burning up of small particles from asteroids or comets in our atmosphere. Although we can spot meteors on any given night, there are specific days in a year during which a large numbers of meteors can be spotted. These events are called meteor showers and they can produce tens of meteors per hour. Rarely, thousands of meteors can be spotted per hour. These events are called meteor outbursts or meteor storms.
Meteor showers happen when Earth passes through the dust and debris left over by a Comet. As the Earth passes though them, these particles enter our atmosphere at tremendous speeds. Friction between the particles and the atmosphere causes them to burn up, resulting in the streak of light.
Below are a few important meteor showers and their peak dates. Although each of these meteor showers will be active for days together, the peak display occurs on a single day or two.
|Meteor Shower||Peak Date|
|Eta Aquarids||May 5|
The International Space Station (ISS), the Hubble Space Telescope (HST), the Iridium satellites and a host of other satellites can be seen with the naked eye. Sunlight reflected from their solar panels enable us to see them. They look like stars moving across the sky. ISS in particular can be very bright.
Iridium satellites appear as stars moving across the sky with brilliant increase in brightness for a few seconds. These are called Iridium flares. Some Iridium flares can be seen even during the day.
The Milky Way. Source: Stellarium
The Andromeda galaxy. Source: Stellarium
Everything that we see in the night sky with the naked eye lies in our galaxy, the Milky Way (with only a very few exceptions). Apart from our home galaxy, we can see the Andromeda galaxy, the Triangulum galaxy and the Megallanic clouds with the naked eye.
Galaxies are very hard to see unless the sky is very dark. Milky Way appears to be a faint band of light stretching across the sky. The other galaxies appear like small fuzzy patches. Andromeda and Triangulum galaxies are some of the farthest objects that can be seen with the naked eye.
Planetarium softwares like Stellarium can be used to help spot the galaxies in the night sky of your region.
Comet Pan-STARRS. Image credit: Phil Hart
A Comet is an icy celestial object. Comets originate from regions of outer solar system known as the Kuiper belt and the Oort cloud. When close enough to the Sun, Comets display a tail which is caused by the evaporation of gases and dust from their surface due to the Sun's heat. These gases and dust particles are pushed away from the Comet by the pressure of sunlight, thus creating the tail.
Some Comets become bright enough to be seen with the naked eye. Later this year, a comet named ISON is expected to put on a splendid display. Some call it the comet of the century. This comet will make its close approach to Sun on 28th November 2013. If it survives the close encounter, a great celestial show is in store.
An Aurora is a natural light display in the sky that typically occurs at the high latitude regions.
Rarely, aurorae can be seen at lower latitudes when there is a geomagnetic storm. Geomagnetic storms occur when massive amounts of charged particles are released by the Sun. On 4th February 1872, an aurora was seen as low as 20 degrees magnetic latitude.
Aurorae are one of nature's most beautiful displays. Some internet resources like Space Weather Prediction Center predict Auroral activity around the world.
The Moon is the brightest object in the night sky. Situated at around 3,80,000 km from Earth, it is our closest celestial neighbour. Just like the planets, the Moon is illuminated by reflected sunlight.
Lunar eclipses, Earth shine, transits of artificial satellites and the Moon illusion are some interesting phenomena involving the Moon. Predictions of lunar eclipses and satellite transits can be found in websites like calsky.
Our Sun is an average sized star. There are many stars in the night sky that are much much bigger than our Sun. For example, the star Betelgeuse in the constellation Orion is so big that if it replaces our Sun, it will engulf the orbit of Mars and possibly Jupiter. Around 2,500 to 5,000 stars can be seen with the naked eye on any clear, moonless night.
Light takes 1 second to travel around 3,00,000 km. A light year is the distance that light can travel in a year. The brightest star, Sirius, is 8 light years away. This means, when we are looking at Sirius today, the light that left sirius 8 years ago is hitting our eyes. So, we are looking at Sirius as it was 8 years ago. Betelgeuse is 427 light years away. So, we are seeing Betelgeuse as it was 427 years ago. If Betelgeuse exploded as a supernova (a giant explosion that massive stars undergo) today, we will still be seeing it as a star for another 427 years. Only then will we see the supernova.