The ghost galaxy CDG-2 (Candidate Dark Galaxy-2) was captured by the NASA/ESA Hubble telescope. This galaxy is very unique because it is almost entirely dominated by dark matter. Astronomers also call it a rare cosmic phenomenon.
Read Also: Rare Galaxy NGC 7722 Revealed Through Hubble Telescope Observations
It’s not surprising because galaxies usually appear to be shining brightly with lots of stars. However, for CDG-2 it looks dim. Almost transparent in fact. This is what makes it nicknamed the ghost galaxy.
CDG-2 Ghost Galaxy Successfully Found
Table of Contents
The findings of this galaxy are contained in the journal The Astrophysical Journal Letters. In the journal it was revealed that the location of the discovery was around 300 million light years from planet Earth. The discovery was in the Perseus galaxy cluster.
When it was discovered, this galaxy was known as low-surface-brightness galaxy. This means a galaxy that has a low surface brightness level. Because of this, many astronomers are tempted to study it in more depth.
CDG-2 As Low-surface-brightness Galaxy
Because it’s included low-surface-brightness galaxythis ghost galaxy CDG-2 has only a few stars. Meanwhile, most of the mass of this galaxy probably includes dark matter. This material is a mysterious substance that does not absorb, emit or reflect light.
Read Also: Get to know Black Hole Phoenix A and its powerful energy explosion
In CDG-2, dark matter makes up 99% of its total mass. This ratio is very extreme. This is because standard galaxies usually only have 5 times more dark matter when compared with ordinary matter.
The dim light is equivalent to the light of 6 million stars similar to the sun. 16% of this brightness level comes from the globular star cluster within it. Visually, the galaxy only has 4 globular clusters (ball star clusters).
This cluster itself is a collection of stars with a solid spherical shape. Usually these clusters orbit large galaxies. Because this cluster was detected, it means it is a marker for the presence of galaxies in the vicinity. In the end, scientists succeeded in finding CDG-2.
Reasons for CDG-2 Lack of Stars
As we mentioned earlier, the ghost galaxy CDG-2 only has a few stars because it is full of dark matter. Regarding this, there is actually a reason. The reason turned out to be due to extreme conditions in the Perseus cluster.
Most of the normal material, such as hydrogen gas, which is nothing more than the raw material for forming stars, may have been swept away. This is due to gravitational interactions with neighboring galaxies which tend to be more massive. However, the globular star cluster CDG-2 can still survive.
Its ability to survive is apparently due to having such a large density of stars and being gravitationally bound. In the end, this resistance to the problem of gravitational tides allowed scientists to recognize the galaxy in almost invisible conditions. This is what makes astronomers so relieved to be able to find this hidden galaxy.
CDG-2 Discovery Technology
In confirming the discovery of the CDG-2 ghost galaxy, astronomers utilized a number of cutting-edge technologies. Starting from the Hubble telescope, Subaru to Euclid. Each telescope has its own important role.
For the Hubble telescope, its use is in revealing high-resolution images originating from a collection of star clusters. Then there is the Subaru telescope (Hawaii) which is useful in providing supporting data. This data aims to validate the galactic environment.
Furthermore, the team of astronomers also used the Euclid telescope (ESA). This telescope can confirm the existence of diffuse or scattered light. The light is said to be very dim around the object.
Through these three advanced technologies, the data is then combined. Then the research team detected a faint light that appeared to stretch around the cluster. David Li’s team from the University of Toronto, Canada considers the ghost galaxy CDG-2 to be the first galaxy to be detected solely through a population of globular clusters.
In fact, it’s not just relying on technology alone. Apparently his discovery also utilized ground observatories. Then it also involves the accuracy of astronomers, scientists or researchers in studying it in more depth.
Read Also: Revealing the Discovery of the Markarian Dwarf Galaxy 178 in the Ursa Major Constellation
In fact, the discovery of the CDG-2 ghost galaxy is unique and surprising. With the precision of astronomers and the sophistication of technology, they can finally reveal the existence of galaxies hiding in the universe. To reveal other interesting information about this galaxy, you need to explore it further. There is great hope that astronomers will be able to discover other hidden galaxies in the future. (R10/HR-Online)
