UDFj-39546284
Encyclopedia
UDFj-39546284 is a compact galaxy
of blue stars that existed as we see it 13.2 billion years ago, around 480 million years after the Big Bang
. It is the oldest galaxy found and exceeds the previous distance record holder by roughly 150 million years. It could remain so until the anticipated launch of the James Webb Space Telescope
sometime this decade. The galaxy has a z (redshift
) of ~10. But unlike UDFy-38135539
, UDFj-39546284 has not been spectroscopically confirmed
. There is therefore still the possibility that it actually is at a lower redshift.
The galaxy is remarkable mainly because it holds significantly expanded information of the early period after the Big Bang. Astronomers were surprised to find evidence that the rate at which the universe was forming stars greatly increased over a 200-million-year time span; the rate of star birth increased by about a factor of ten during the period between 480 million years and 650 million years after the Big Bang.
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
of blue stars that existed as we see it 13.2 billion years ago, around 480 million years after the Big Bang
Big Bang
The Big Bang theory is the prevailing cosmological model that explains the early development of the Universe. According to the Big Bang theory, the Universe was once in an extremely hot and dense state which expanded rapidly. This rapid expansion caused the young Universe to cool and resulted in...
. It is the oldest galaxy found and exceeds the previous distance record holder by roughly 150 million years. It could remain so until the anticipated launch of the James Webb Space Telescope
James Webb Space Telescope
The James Webb Space Telescope , previously known as Next Generation Space Telescope , is a planned next-generation space telescope, optimized for observations in the infrared. The main technical features are a large and very cold 6.5 meter diameter mirror, an observing position far from Earth,...
sometime this decade. The galaxy has a z (redshift
Redshift
In physics , redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum...
) of ~10. But unlike UDFy-38135539
UDFy-38135539
UDFy-38135539 is the Hubble Ultra Deep Field identifier for a galaxy which has been calculated to have a light travel time of 13.1 billion years with a present comoving distance of around 30 billion light-years...
, UDFj-39546284 has not been spectroscopically confirmed
Spectroscopy
Spectroscopy is the study of the interaction between matter and radiated energy. Historically, spectroscopy originated through the study of visible light dispersed according to its wavelength, e.g., by a prism. Later the concept was expanded greatly to comprise any interaction with radiative...
. There is therefore still the possibility that it actually is at a lower redshift.
The galaxy is remarkable mainly because it holds significantly expanded information of the early period after the Big Bang. Astronomers were surprised to find evidence that the rate at which the universe was forming stars greatly increased over a 200-million-year time span; the rate of star birth increased by about a factor of ten during the period between 480 million years and 650 million years after the Big Bang.