NASA Roman Core Survey Will Trace Cosmic Expansion Over Time

The Roman Spatial Telescope Nancy Grace of NASA will be a discovery machine, thanks to its large field of vision and its resulting data torrent. Scheduled to launch at the latest in May 2027, the team working at the launch in the fall of 2026, its wide instrument on the field in almost infrared will capture a 200 times larger zone than the infrared camera of the Hubble space telescope, and with the same sharpness and the same sensitivity. Roman will devote around 75% of its scientific observation time during its main mission over five years to conduct three basic community surveys which have been defined in collaboration by the scientific community. One of these investigations will travel the sky for things that burst, flash and change differently, like the explosion of stars and collision of neutron stars.

Called the investigation into the high latitude temporal domain, this program will look outside the plane of our Milky Way Galaxy (that is, high galactic latitudes) to study objects that change over time. The main objective of the survey is to detect tens of thousands of a particular type of explosive star known as IA type supernovae. These supernovae can be used to study how the universe has extended over time.

“Roman is designed to find tens of thousands of IA type supernovae at greater distances than ever,” said Masao Sako of the University of Pennsylvania, who was co -chaired by the committee which defined the statement of the High Latitude Domaine. “By using them, we can measure the history of the expansion of the universe, which depends on the quantity of dark matter and dark energy. In the end, we hope to know more about the nature of dark energy.”

Sound the dark energy

IA supernovae are useful as cosmological probes because astronomers know their intrinsic brightness, or how brilliant they are, at their peak. By comparing this with their observed brightness, scientists can determine how far they are. Roman can also measure the speed with which they seem to move away from us. By following the speed at which they retreat at different distances, scientists will retrace the cosmic expansion over time.

The only novel can find the weakest and most distant supernovae which illuminate early cosmic eras. It will complete the ground telescopes such as the VERA C. Rubin observatory in Chile, which are limited by the absorption of the earth’s atmosphere, among other effects. Rubin’s greatest strength will be to find supernovae that has occurred in the past 5 years. Roman will extend this collection to times much earlier in the history of the universe, around 3 billion years after the Big Bang, or up to 11 billion years in the past. This would double more than the measured calendar in the history of the expansion of the universe.

Recently, the black energy survey has revealed clues that dark energy can weaken over time, rather than being a constant expansion force. Roman surveys will be essential to test this possibility.

Search for exotic phenomena

To detect transitional objects, whose brightness changes over time, Roman must review the same fields at regular intervals. The High Latitude Survey of Time Domaine will devote a total of 180 days of time observation to these observations spread over a period of five years. Most will occur over a period of two years in the middle of the mission, revisiting the same areas once every five days, with 15 days of additional observations at the start of the mission to establish a basic line.

“To find things that change, we use a technique called image subtraction,” said Sako. “You take an image and subtract an image of the same piece of sky which was taken much earlier – as soon as possible in the mission. So you delete everything that is static, and you find yourself with things that are new.”

The survey will also include an extensive component which will revisit some of the observation fields approximately every 120 days to search for objects that change on long ladders. This will help detect the most distant transients that existed as long as a billion years after the Big Bang. These objects vary more slowly due to the dilation of time caused by the expansion of the universe.

“You really benefit from taking observations over the duration of the mission,” said Brad Cenko of the Goddard Space Flight Center in NASA in Greenbelt, Maryland, the other co -president of the investigation committee. “This allows you to capture these very rare and distant events which are really difficult to obtain otherwise, but which tell us a lot about the conditions of the early universe.”

This extended component will collect data on some of the most energetic and lasting transients, such as the disturbance events of the tides – when a supermassive black hole shouts a star – or planned but still invisible of invisible events under the name of a supernova for instability of the pairs, where a massive star explodes without leaving a nine hole or a black hole.

Details of the investigation

The investigation in the high latitude temporal field will be divided into two imagery “levels” – a wide level which covers more area and a deep level which will focus on a smaller area for a longer period to detect lower objects. The wide level, totaling just over 18 square degrees, will target objects over the 7 billion years, or half the history of the universe. The deep level, covering an area of 6.5 square degrees, will reach lower objects that existed up to 10 billion years. Observations will take place in two areas, one in the northern sky and one in the southern sky. There will also be a spectroscopic component of this survey, which will be limited to the southern sky.

“We have a partnership with the Subaru Observatory on the ground, which will follow spectroscopic from the northern sky, while Roman will make spectroscopy in the southern sky. With spectroscopy, we can say with confidence what type of supernovae we see, “said Cenko.

In collaboration with the two other community surveys of novel, the broad survey of great latitude and the Galactic Bulge survey in the field of time, the investigation in the time of time at high latitude will help to map the universe with clarity and a depth never done before.

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The Roman Spatial Telescope of Nancy Grace is managed at the Goddard Space Flight Center in NASA in Greenbelt, Maryland, with the participation of the NASA jet propulsion laboratory in Southern California; Caltech / Ipac in Pasadena, California; The Institute of Sciences of the Space Telescope in Baltimore; And a scientific team including scientists from various research institutions. The main industrial partners are BAE Systems, Inc. in Boulder, Colorado; L3harris Technologies in Melbourne, Florida; And Teledyne Scientific & Imaging at Thousand Oaks, California.

By Christine Pulliam
Science Institute of the Space Telescope, Baltimore, MD.