NASA’s Nancy Grace Roman Space Telescope will create a huge panorama of the universe to help us answer questions about the evolution of the universe. Astronomers also expect the mission to use two different techniques to find thousands of planets because it surveys a wide variety of stars in the Milky Way.
Rome will locate these potential new worlds or exoplanets by tracking the amount of light emitted by distant stars over time. In a technique called gravitational microlensing, the spikes of light indicate the possible presence of planets. On the other hand, if the light emitted by the star dims periodically, it may be because a planet traverses the surface of the star as it completes its orbit. This technique is called the transit method. By using these two methods to find new worlds, astronomers will gain unprecedented views on the composition and arrangement of our Milky Way planetary system.
Rome is scheduled to launch in the mid-2020s, and it will become one of NASA’s most prolific planet hunters.
The mission’s wide field of view, excellent resolution and incredible stability will provide a unique observation platform for discovering the tiny light changes needed to find other worlds through microlenses. This detection method uses the gravitational light bending effect of massive objects predicted by Einstein’s general theory of relativity.
This happens when the foreground star (lens) is randomly aligned with the distant background star (source) when viewed from the earth. As the stars drift along their orbits around the Milky Way, their arrangement varies from a few days to a few weeks, thereby changing the apparent brightness of the source star. The precise patterns of these changes provide astronomers clues about the nature of the lensed stars in the foreground, including the existence of planets around them.
Roman is already looking for many microlensed stars, which may contain planets in motion.
Astrophysicist Benjamin Montet, a science lecturer at the University of New South Wales in Sydney, said: “Microlensing events rarely happen, and they happen very quickly, so you need to observe many stars repeatedly and accurately measure brightness changes. Detect them.” “These are exactly the same as looking for transit planets, so by creating a reliable microlens survey, Roman will also produce a good transit survey.”
Montet and colleagues pointed out in a 2017 paper that the Romans (previously known as WFIRST) could capture more than 100,000 planets in front of their host stars or passing by their stars. Planets will periodically dim as they travel repeatedly in front of their stars. This provides strong evidence, which astronomers usually have to confirm through follow-up observations.
For NASA’s Kepler and K2 missions, the transit method for finding exoplanets has achieved great success. So far, Kepler and K2 missions have discovered about 2,800 confirmed planets. It has been used by NASA’s Transit Exoplanet Survey Satellite (TESS). Because Roman will find planets orbiting farther, dimmer stars, scientists usually have to rely on expansive data sets from missions to verify these planets. For example, Roman may see a second solar eclipse-when a planetary candidate passes behind its host star, the brightness will decrease a bit, which may help confirm its existence.
The dual detection methods of microlens and transit complement each other, allowing Roman to find a variety of planets. The transition method is best for planets that orbit very close to the star. On the other hand, the microlens can detect planets orbiting away from their host star. This technology can also find so-called rogue planets, which are not combined with stars under the action of gravity. These worlds range from rocky planets smaller than Mars to gas giants.
About three-quarters of the transit planets that Roman will discover will be natural gas giants such as Jupiter and Saturn, or ice giants such as Uranus and Neptune. Most of the rest may be planets, whose mass is four to eight times that of Earth, namely mini-Neptune. These worlds are particularly interesting because there are no planets like them in our solar system.
Some Roman catches in transit are expected to be located within the habitable zone of their star, or the planet may be within the orbital distance of liquid water on its surface. The location of this area depends on the size and temperature of the host star-the smaller and cooler the star, the closer its habitable area. Roman’s sensitivity to infrared makes it a powerful tool for finding planets around these dark orange stars.
The Romans will also look farther from the earth than previous planet hunting missions. Kepler’s initial survey was to monitor stars at an average distance of about 2,000 light-years. It looked at a moderate sky area, totaling about 115 square degrees. TESS can scan almost the entire sky, but its purpose is to find the world closer to the earth, with a typical distance of about 150 light years. Roman will use both microlens and transit detection methods to find planets 26,000 light-years away from Earth.
Combining the results of the Roman microlens and transit planet search will reveal worlds of various sizes and orbits, thereby helping to provide a more complete planetary survey. This mission will provide the first opportunity to discover a large number of orbiting planets located thousands of light years away, thereby helping astronomers to learn more about the demographics of planets in different regions of the Milky Way.
Research co-author Jennifer Ye, an astrophysicist at the Center for Astrophysics, said: “The fact that we can detect thousands of planets just by looking at the collected microlens data is exciting.” Cambridge, Massachusetts Harvard University and Smithsonian Institution. “This is free science.”
NASA’s Rome mission will probe the core of the Milky Way to find hot Jupiter, brown dwarf stars
Courtesy of NASA’s Goddard Space Flight Center
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