How Scientists Decet Extrasolar Planets

EXTRASOLAR PLANETS

For hundreds of years, scientists knew nothing of the world

outside our little planet earth. Now in the 21st century, science is

gathering more knowledge about the depths of the universe than

could have ever been imagined. Light years away, bodies outside of

our solar system are almost inconceivable, but new technology is

allowing us to not only detect these distant planets but also to take

pictures of them.

In the year 1993, a polish astronomer by the name of

Aleksander Wolszczan claimed to have discovered the first extrasolar

planet. His discovery was later confirmed, orbiting around a pulsar.

Planets around pulsars are believed to come from the remnants of

the supernova that produced the pulsar, or the cores of the gas

giants that survived the supernova. In the 1990's, more and more

planets were being discovered due to a vast improvement in

telescope technology, measuring gravitational influence upon stars

moreso than visually, although it is being done as well. To date more

than 150 extrasolar planets have been accounted for, most of which

being larger in mass than Jupiter.

There are several ways to detect planets that are too faint and

far away to be directly detected with a conventional telescope or

other method. Some of them are more effective than others, but

each has been a stepping stone in the field of detecting extrasolar

planets. The first method, pulsar timing, has been refuted before,

but the method did lead to the discovery of the first planets. Pulsar

timing involves observing abnormalities in the pulses from a pulsar

deep in space. The first "discovery" of a planet using pulsar timing

turned out to be inaccurate, since it failed to take into account the

motion of the Earth. This method involves precise measurements of

the pulsar's signal, but because of this the method is more

commonly used to detect pulsar companions than planets. However,

Aleksander Wolszczan used this method to discover the first solar

system outside of our own. This method also helped in the discovery

of the oldest known planet, which happens to also be the only

known planet to orbit two stars.

The oldest method, and consequently the most unreliable one

used in the search for extrasolar planets is astrometry. Astrometry

involves measuring the motion of a star in hopes of finding an

influence by its planets. Unfortunately, changes in the motion are so

small that they can not be detected accurately, nor confirmed by

other method. Since more successful methods have been found and

are easier, most scientists have given up on astrometry, and moved

to more efficient methods such as radial velocity.

Radial velocity measures differences in the speed that a star

moves either away or towards us. It is known as the "Doppler

Method" because the radial velocity can be derived from the

displacement of the parent star's spectral lines because of the

Doppler effect.

This method is the more successful one used by people in search of

planets, but it only works for stars that are relatively close, out to

about 160 light years. The radial velocity method easily finds planets

that are nearby to stars, and can be used to confirm the transit

method.

The transit method is a relatively new method that can detect a

planet's shadow when it passes in front of its host star. It only works

for a small percentage of planets when their orbits are perfectly

aligned from the point that we look from, but this method can be

used on stars much further away than the Doppler method. The

transit method can also be used to measure the radius of a planet,

and so scientists can determine the density of these planets by using

this method and another mass-determining method. The picture

below is a rendition of a planet's transit across a foreign star.

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