The Hubble Space Telescope has done it again! As a veritable space and time machine, it takes us across the immense gulf of space and back eons of time to when the universe was a much younger and a much different place than it is today. In another incredible first, the orbiting observatory has pushed back the distance frontier yet again, capturing the light of a galaxy that began its journey 13.4 billion years ago, a mere 400,000,000 years after the Initial Inflationary Event (the Big Bang)!
In his now famous 1929 announcement, Edwin Hubble concluded that the universe is expanding and thus began a journey of discovery that continues today, evolving from the notion that the universe was static and predictable to one that is dynamic, changing and expanding, with galaxies, far-flung and receding across the limitless frontiers of space and time.
The expanding universe, the discovery of increasing recessional velocity with distance, today known as the Hubble Constant, is a consequence of a uniformly expanding space. This concept underpins much of our Cosmology and understanding of the large scale universe. The expanding universe behaves like a gas, cooling as it expands and today we observe the expanding cosmic afterglow of the Big Bang, the once super-hot expanding plasma now cooled to almost absolute zero as the Cosmic Microwave Background (CMB) at a temperature of 2.7 degrees Kelvin.
The Hubble Team’s observation of galaxy GN-z11 is at the limit of detection for the telescope. Due to the galaxy’s tremendous distance, almost all of the visible light has been “Red Shifted” into the near Infrared, the region of the electromagnetic spectrum just beyond the visible, red end of the spectrum.
Much in the same way that the sound pitch of a train whistle changes as the train passes through a station, the color or wavelength of light emitted by an object changes depending on the relative speeds of the observer and the object. If the object is receding, the color or wavelength of the light is shifted to the red; if the object is approaching, the color or wavelength of the emitted light is shifted towards the blue. The magnitude of the shift depends on the relative velocities of the object and observer. This is one key aspect of Hubble’s Distance/Velocity metric, the further an object is, the greater its recessional velocity and thus, the greater its redshift.
The feeble light from the galaxy that went into producing the image, that pushed the limits of the mighty Hubble, represented blue and visible light in the rest frame of the galaxy; it was emitted originally as blue and visible light but, because of the tremendous distance and relative recessional velocity, it was received by Hubble as deep red and near Infrared light! That this galaxy was detected at all is a testament to its high blue luminosity, an observation that would be consistent with our models of the early universe that indicate greater star formation rates with newly formed stars generally thought to be hotter, bluer and more luminous than they are today. Any deeper observations will require a larger instrument, observations that are perfectly suited for the James Webb Space Telescope (JWST), scheduled for deployment in 2018. Hopefully HST will still be on orbit and operational when JWST comes online, thus providing a seamless overlap between the two observatories.
NASA/ESA/Hubble Press Release here.
Imagination is more important than knowledge
An index of all articles in this blog can be found here.