Extreme Universe: The Most Distant Object Measured in the Universe October 21, 2010Posted by jcconwell in Cosmology, Extreme Universe, Galaxy.
Tags: Extreme Universe, Galaxy, UDFy-38135539
Coming in as the most distant object with a confirmed redshift, UDFy-38135539 is the Hubble Ultra Deep Field (UDF) classification for a galaxy which, as of October 2010, is the most distant object from Earth known to exist in the universe. Its discovery is formally detailed in the 21 October 2010 article “Spectroscopic Confirmation of a Galaxy at Redshift z=8.6” in the journal Nature.
Other than putting a trophy on the wall for a new record distance, what makes this object so important? To understand this, it might be better to translate this from the most distant object to the oldest measured object. With a measured cosmological redshift of z=8.6, the object emitted the light we are seeing about 13.1 billion years ago, or more useful here, when the universe was only 600 million years old.
What was it like in the universe at that age? Conditions were quite different back then. This epoch of time is when the Universe went from largely neutral gas to basically ionized plasma, called reionization.
The reionization period is about the farthest back in time that astronomers can observe. The Big Bang, 13.7 billion years ago, created a hot, plasma filled universe. Some 400,000 years after the Big Bang, temperatures cooled, from the expanding universe, so electrons and protons joined to form neutral hydrogen, and the murk cleared. By about 1 billion years after the Big Bang, this neutral hydrogen began to form stars in the first galaxies, which radiated energy and reionzied the hydrogen. Radiation from the hot new stars started to clear the opaque hydrogen plasma surrounding the newly formed galaxies that filled the cosmos at this early time.
Much of any ultraviolet light from these new stars was absorbed in the gas surrounding the stars, the remainder has been redshifted down to the infrared by the expansion of the universe over 13.1 billion years.
To obtain such dim spectra, scientists turned the the VLA (Very Large Telescope).
The Very Large Telescope (VLT) is made up of four separate optical telescopes (the Antu telescope, the Kueyen telescope, the Melipal telescope, and the Yepun telescope) organized in an array formation, built and operated by the European Southern Observatory (ESO) at the Paranal Observatory on Cerro Paranal, a 2,635 m high mountain in the Atacama Desert in northern Chile. Each telescope has an 8.2 m aperture. The array is complemented by four movable Auxiliary Telescopes (ATs) of 1.8 m aperture. Working together in interferometric mode, the telescopes can achieve an angular resolution of around 1 milliarcsecond, meaning it could distinguish the gap between the headlights of a car located on the Moon.
To get a spectra of such a dim object, about 4 billion times dimmer than the dimmest star you can see with the naked eye, the VLA took an exposure of about 16 hours.