"The dwarf galaxy NGC1427A flies through the Fornax galaxy cluster and undergoes disturbances that would not be possible if this galaxy were surrounded by a heavy and extended dark matter halo, as required by standard cosmology. Credit: ESO" (ScitechDaily.com/New Discovery Indicates an Alternative Gravity Theory)
The dwarf galaxies are interesting things. Dwarf galaxies are small star clusters, colder than giant galaxies and closer than ultra-diffuse galaxies or UDGs. That is very far from us.
Conditions in dwarf galaxies are sometimes similar to the UDGs. That thing is true if there are lots of old stars in the dwarf galaxy.
Some dwarf galaxies are following Milky Way. They are not as bright as Milky Way or Andromeda galaxy. And that allows for observing black holes in the middle of those small galaxies. In the cases of the Milky Way and Andromeda, the brightness of the dust hides the black hole behind them.
Their lack of material is the result of larger galaxies' gravitational effect. Some dwarf galaxies or ball-shaped stellar clusters. Along with open stellar clusters are full of blue supergiants. And those stars are extremely hot and bright.
That allows observing energy interactions inside those small galaxies. There is the possibility that there is star formation in dwarf galaxies. But the gravitational effect of the larger galaxies pulls dust and gas away from those star clusters. Also, a large number of blue supergiants can push material away from the galaxy.
By observing galaxies is possible to research things, like how the bubble of dark matter that surrounds the dwarf galaxy interacts with visible material. And if the bubble of dark matter will pull material from both sides, that thing makes it possible that the shape of a dwarf galaxy turns into a disk.
The difference between a star cluster and a dwarf galaxy is not very big. Sometimes is introduced that the star cluster is where new stars are forming. And that are separated from the galaxies are dwarf galaxies.
The difference between dwarf galaxies and normal galaxies is their size. In dwarf galaxy is normally 1000 up to several billions of stars. There are 200-400 billion stars in Milky Way.
In some dwarf galaxies is only young or old stars.
The difference between open and other star clusters is that there is no dominating gravitational center in open star clusters. In other, ball-shaped star clusters is the gravitational center. And other stars are orbiting that gravitational center.
In embedded star clusters there are forming stars all the time. Those star clusters are full of young stars. And the globular clusters are opposite to the embedded clusters.
The oldest known stars are in the globular star clusters. And there is a possibility that the globular star clusters are sometimes the remnants of dwarf galaxies.
In those cases, larger galaxies pulled the material away from the dwarf galaxy. And that thing turns the dwarf galaxy into a globular star cluster. The age of the stars in that type of star cluster is almost the same as in the universe. So star clusters and dwarf galaxies are fascinating things.
https://scitechdaily.com/new-discovery-indicates-an-alternative-gravity-theory/
https://en.wikipedia.org/wiki/Dwarf_galaxy
https://en.wikipedia.org/wiki/Ultra_diffuse_galaxy
Image: https://scitechdaily.com/new-discovery-indicates-an-alternative-gravity-theory/
https://en.wikipedia.org/wiki/Star_cluster
https://anewtonsapple.blogspot.com/
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