The first Israeli in space

NASA decided to name its new satellite after an Israeli scientist. What is the importance of the "High Energy Spectroscopic Solar Observatory named after Reuven Ramati" and why did Ramati, who passed away recently, receive this great honor

By Avishai Gal-Yam

The American space agency decided to name a new satellite launched recently after Reuven Ramati, an Israeli scientist who worked for many years in the United States. Ramati is the first Israeli, and the first scientist from NASA's Goddard Space Center, to receive this honor. He joins a very small group of physicists and astronomers for whom previous research satellites were named, including Galileo, Newton, Einstein and Hubble.

Ramati, who was born in 1937 in Romania and immigrated to Israel as a teenager, was one of the first physics students at Tel Aviv University. After receiving a bachelor's degree from the university in 1961 and teaching physics at the "Holtz" technical high school in Tel Aviv, he went to doctoral studies at the University of California, Los Angeles (UCLA). In 1967, a year after he finished his doctorate, he joined the team of scientists at the Goddard Space Center, where he worked until his death last year from Lou Gehrig's disease.

In 1980, Prof. Ramati was appointed head of the theoretical department at the High Energy Astrophysics Laboratory at Goddard, served as a professor of physics at the University of Maryland, and in 1981 was awarded the NASA Medal for outstanding scientific achievements. Throughout his years of work at NASA, he maintained his Israeli citizenship and worked in close cooperation with fellow scientists in Israel.

Despite his serious illness, which deprived him of the ability to speak and severely limited his movement, he continued to work until his last day. A few hours before his death, he was still working with his colleague and close friend Prof. Ben Zion Kozlovsky from Tel Aviv University on a scientific article. The article was published a few months ago, after Ramati's death.

Ramati was a multidisciplinary physicist. His scientific activity was concentrated in the field of high-energy astrophysics: a field that combines knowledge in the fields of atomic, nuclear and particle physics, and uses them to understand various processes in the universe - energetic phenomena on the surface of the Sun and on the surface of other stars; the ways of the creation of light elements in the universe; And the sources of cosmic radiation - a stream of particles that constantly arrive from space to the earth.

Ramati was a pioneer in the field known as gamma ray spectroscopy. Gamma radiation is a type of electromagnetic radiation, like light or radio waves, that has the most energy. On Earth, gamma radiation is emitted from radioactive materials and is one of the products of nuclear explosions. Ramati and his partners showed that an accurate analysis of the amount of gamma radiation emitted from the sun at different energies (the spectrum of gamma radiation) may make a decisive contribution to understanding various processes on the surface of the sun.

Although Shermati concentrated on theoretical research, he distinguished himself by working in close cooperation with observational astronomers, who were engaged in the development of advanced observational instruments that make it possible to test the theory's predictions. Ramati was one of the main driving forces behind the launch of the research satellite, HESSI, which was sent into space on February 5 and focuses on the study of X-rays (X-rays) and gamma radiation coming from the sun. To mark his great contribution to astrophysics in general and HESSI's research fields in particular, NASA authorities decided to rename the satellite: RHESSI the Reuven Ramati High Energy Solar Spectroscopic Imager

The main purpose of RHESSI is to observe solar flares. Solar flares are the most powerful explosions in our solar system. During such an eruption, energy equal to the explosion of billions of tons of TNT is released for a few minutes. As a result, material in the outer shell of the Sun is heated to a temperature of millions of degrees and particles are accelerated to a speed close to the speed of light. Some of the particles that are accelerated during such a solar eruption hit the sun's atmosphere and stop, while emitting X-rays and gamma rays. However, other particles are emitted into space and some reach the Earth's region.

It is not known exactly how solar flares are formed. The assumption is that the energy comes from internal movements of matter inside the sun (similar to the movement of the plates on the earth, which creates earthquakes and volcanic activity). The flow of large amounts of gas inside the sun creates strong magnetic fields where a lot of energy is stored. When this energy is suddenly released, a solar flare occurs. Despite years of research and observations, researchers do not know exactly where on the surface of the sun the eruptions form and are unable to predict their appearance. The ability to predict solar flares is of great importance because strong flares may cause damage to spacecraft, astronauts and satellites in space, as well as disruptions to communication and electrical systems on Earth. This is the main reason why NASA and the US government devote a lot of effort and money to research on this subject.

In general, the level of energetic activity on the surface of the sun (manifested in a variety of phenomena, including the appearance of dark "sunspots") changes in 11-year cycles. Every 11 years the sun's activity reaches a peak - and then fades. It turns out that the appearance of solar flares also depends on this cycle: the largest flares occur mainly when the sun is at its peak activity. This is why it was imperative to launch RHESSI now, near the peak of the Sun's activity last year. With the help of the detectors installed on the satellite, the most sensitive and the best ever installed in any research spacecraft of this type, the scientists will be able to determine for the first time exactly where on the surface of the sun the eruptions occur, how such a huge amount of energy is released in such a short time and how the particles are accelerated that eventually reach the environment Earth. It is possible that with the help of the information received from RHESSI, it will be possible to give "early warnings" about the appearance of particularly dangerous solar eruptions.

About two months after he began scientific activity, the scientists are very satisfied with the first observations coming from RHESSI. Reuven Ramati, who pushed and accompanied the launch project of the satellite for many years, did not get to see the fruits of his work, but the NASA authorities did not forget his contribution: on the 17 In May, an event was held at the Goddard Space Center to mark the beginning of HESSI's scientific activity, and on this occasion it was announced that the name of the satellite would be changed. Adding the letter R to the original name is a final salute to Reuven Ramati's scientific work.