The Hubble telescope just spotted the most distant star ever detected
How much further back could we go?
Why look back?
One of the main goals of JWST is to know what the early universe looked like and when early stars and galaxies formed, thought to be between 100 million and 250 million years after the Big Bang. And, luckily, we can get hints about this by looking even further back than Hubble or the JWST can manage.
We can see light from 13.8 billion years ago, although it is not starlight – there were no stars then. The furthest light we can see is thecosmic microwave background(CMB), which is the light leftover from the Big Bang, forming just 380,000 years after our cosmic birth.
The universe before the CMB formed contained charged particles of positive protons (which now make up the atomic nucleus along with neutrons) and negative electrons, and light. The light was scattered by the charged particles, which made the universe a foggy soup. As the universe expanded it cooled until eventually the electrons combined with the protons to form atoms.
Unlike the soup of particles, the atoms had no charge, so the light was no longer scattered and could move through the universe in a straight line. This light has continued to travel across the universe until it reaches us today. The wavelength of the light got longer as the universe expanded – and we currently see it as microwaves. This light is the CMB and can be seen uniformly at all points in the sky. The CMB is everywhere in the universe.
The CMB light is the furthest back in time that we have seen, and we cannot see light from earlier times because that light was scattered and the universe was opaque.
There is a possibility, however, that we can one day see even beyond the CMB. To do this we cannot use light – we will need to usegravitational waves. These are ripples in the fabric of spacetime itself. If any formed in the fog of the very early universe, then they could potentially reach us today.
In 2015, gravitational waveswere detectedfrom the merging of two black holes using the LIGO detector. Maybe the next generationspace-based gravitational wave detector– such as Esa’s telescope Lisa, which is due for launch in 2037 – will be able to see into the very early universe before the CMB formed 13.8 billion years ago.
Article byCarolyn Devereux, Senior Lecturer in Astrophysics,University of Hertfordshire
This article is republished fromThe Conversationunder a Creative Commons license. Read theoriginal article.
Story byThe Conversation
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