by S. Prasad Ganti
Every decade, a survey is conducted in the US to check for the trends in astronomy so that recommendations can be made for projects like building new telescopes. It is called the decadal survey. For this decade, the survey was delayed by about a year due to the pandemic. This decadal survey is titled “Astro 2020”.
The survey takes note of the achievements made using the current telescopes and detectors and comes up with areas which need more focus or further study. While I try to summarize the key points from the report, quoting some statements verbatim, the complete report is available at the following link. It is very educational to read the whole report.
The first trend is to look for habitable worlds. Basically, looking for exoplanets outside of our solar system, with the grand goal of finding potentially habitable worlds. As a part of this trend, the first recommendation is to launch a space telescope which can observe in the infrared/optical/ultraviolet ranges. With a mirror size of 6m, compared to 2.5m for the Hubble space telescope Such a telescope will be very sophisticated and time consuming to design and build. It is not expected to launch till the 2040s. Another recommendation is to study to build two strategic missions- one a Far-Infrared space telescope and second a high-resolution X-ray space telescope.
Second trend is to provide new windows on the dynamic universe – to understand the black holes and the neutron stars better. This can lead to understanding the violent events which create them and also to know more about the earliest moments after the Big Bang. Towards this end, the recommendation is to build a Cosmic Microwave Background Stage 4 Observatory. It will study the polarization of gravity waves from the early universe.
The third trend is to study the drivers of galaxy growth. As to how galaxies evolve from the webs of gases leading to star formation. Studies of gas are usually done in the radio range. The recommendation is to replace the current radio telescopes – Karl Jansky Very Large Array and the Very Long Baseline Array. The replacement should be the Next-Generation Very Large array – an array with ten times the sensitivity to be constructed by the end of the decade.
The current telescopes under construction have been mentioned in the survey. Recommendation is made for the US to invest in the GMT (Giant Magellan Telescope) and the TMT (Thirty Meter Telescope). GMT is under construction in Chile. While the TMT ran into trouble in Hawaii with the local population, it is being relocated to an alternate site.
The long awaited James Webb Space Telescope (JWST) will hopefully be launched in December 2021 and will directly examine the youngest observable galaxies, The Vera Rubin observatory under construction in Chile and the launch of Nancy Grace Roman observatory is expected in 2025. They will transform the views of dwarf galaxies at the extremes of galaxy formation and the record of ancient stars they left behind. Laser Interferometer Space Antenna (LISA) (launch expected in mid2030s) should identify mergers of black holes all the way back to their earliest form. LISA is an advanced interferometer with a million and a half miles on each triangular side, to detect gravity waves.
Gravity waves, along with neutrinos are the new messengers. It all started with the naked eye astronomy by looking at dark skies and tracing star patterns. Then came the telescope to see dimmer or distant stars. Next, Telescopes were built to detect the other invisible parts of the spectrum – radio, infrared, ultraviolet, X-rays, Gamma rays etc. And now the Gravity wave detectors and neutrino detectors. Often, incidents are followed up via multiple paths for confirmation. Getting information via all these paths paints a composite picture of the Universe.
The recommendation is to build the next generation neutrino detector – IceCube-Gen 2. IceCube is a neutrino detector at the South pole. But this committee lacks the charter to press upon such a recommendation. Nevertheless, hopefully, the next generation neutrino detector will be built.
We are living in exciting times. And more excitement is in the air.