A cloud of gas and dust within which stars are formed. Above: The cloud in light photography
seen; Below: the cloud in infrared photography
Avishai Gal-Yam
Until recently, astronomers could only observe the solar system
our. The theory explaining the formation of the planets was built
Therefore in order to explain what is happening in this system. In recent years,
Following a series of technological breakthroughs in the production and operation of telescopes
Sophisticated, astronomers are able to observe star systems for the first time
Cults that are in the process of formation around other suns: radiation observations
Infrared, for example, shows how stars are in the process of formation
The primordials emerge from clouds of gas and dust.
As a result of the technological breakthroughs, much research effort has recently been devoted
To examine the processes of star formation. The researchers are trying to find out, without
Success still, why the stars that are formed are different from each other: there are stars
A giant whose mass is tens of times greater than that of the sun, compared to dwarfs whose mass it is
only about a tenth of that of the sun. Another question astronomers are trying to figure out
The answer is why most stars do not form individually but rather
As pairs: two stars orbiting each other.
Stars are formed from clouds of gas, mainly hydrogen, floating in space
The interstellar. The force of gravity acting between the gas particles causes clouds
shrink so that the distance between the gas particles is small. As a result, strength increases
the attraction between them. This process is called "gravitational collapse". the gas clouds
shrinking, the gas becomes more compressed and hotter. the temperatures
In the heart of the gas clouds collapsing under the influence of gravity can reach
Up to millions of degrees Celsius: in such cases the collisions between particles
The gas is extremely powerful.
Sometimes, atoms of hydrogen gas collide with each other with such great force that they
become atoms of another element: helium gas. This process is called fusion
Nuclear (or fusion) - the process on which the hydrogen bomb is based. When
Such a process takes place in the heart of a gas cloud, a tremendous amount of energy is released
In the form of heat and radiation: this can be compared to the explosion of millions of bombs
Hydrogen at the same time. The energy released in the core of the cloud as a result of a process
The nuclear fusion pushed the outer layers of the cloud outwards
and balances the force of gravity that pulls them inward: the gas cloud, which is now
Very hot, reaches a state of equilibrium. The heat and radiation, which originate in the center
The cloud is ejected from the outer layers, and the gas cloud turns into a hot ball
of gas emitting radiation and heat - and this is a star.
The described process explains how Shabbat stars are formed - our sun,
for example. But how were the planets formed? The nature of the planets
(Planets) is fundamentally different from the stars of the Sabbath. One of the differences
The greatest among them is that the stars of the Sabbath emit their own light. they look
We are so pale only because they are a huge distance away from us.
In contrast, the planets are much smaller bodies. They are not light sources
By themselves: the light that reaches our eyes from them is the reflected sunlight from above
their faces
The accepted scientific assumption is that the planets are formed from the remnants of the gas cloud
from which the main star of the system was formed. The remaining remains surround the
The young star and disk creators. As mentioned, most of this material is gas
Hydrogen, but it also has heavier elements: carbon, oxygen, nitrogen
and iron In the resulting disc, these materials crystallize into tiny dust grains,
which coalesce and become larger and larger lumps of matter. These lumps
collide with each other and form bodies whose shape is similar to asteroids in the system
our sun Over time, the largest lumps are captured, with the help of force
Gravity, all the matter that moves close to their orbit and become stars
Go, like Earth, Venus and Mars. These planets are mostly composite
oxygen, carbon, nitrogen and iron and are called Earth-like planets. to my stars
Especially heavy ones, which are in a distant orbit from the Sabbath star, for example
Jupiter and Saturn in our solar system, have strong enough gravity to order
Capture a shell of hydrogen gas: these stars are called "gas giants".
Two groups of astronomers from the USA recently used the space telescope
"Hubble" to examine the creation conditions of planets. The researchers chose
Two stars outside our solar system, which analysis of the properties of light
Coming from them indicates that they are quite young. The researchers wanted to watch
In the disk of dust around the stars, from which the planets are supposed to form.
Such observations are difficult to make because the light coming from the disc is very weak
relative to the dazzling light of the star. in order to distinguish the dust disk
orbiting the stars, the researchers used a camera sensitive to radiation
infrared. In this area, the light coming from the dust in the disk is relatively strong,
While the light coming from the star is relatively weak. the sharpness of the resulting images
The space telescope makes it possible to hide the light of the star, so that it is possible to distinguish
In the pale light emitted from the disc.
The images obtained from the space telescope revealed previously unseen details: the researchers
managed to clearly identify the dust disks around the two stars. It turned out
Even if the discs are not continuous: it is possible to notice that annular areas
Some discs are dust free. The obvious explanation for this is that in the systems
These are already formed planets, which have captured most of the dust and particles
The small matter near their orbits. with the means of observation at our disposal
Today it is impossible to see these planets themselves, because light
Their mother star being returned from them to us is too weak, however the trails they left
Following them in the gas disk, and the dust from which they were formed, testify to their existence.
{Appeared in Haaretz newspaper, 14/2/2000{
The Hidan site was until 2002 part of the IOL portal from the Haaretz group, Dr. Gal-Yam is currently a researcher at the Weizmann Institute
