Nearly 4,000 exoplanets have been discovered so far and orbiting distant stars. One question that inevitably arose is how similar are these planets and solar systems to ours, especially to Earth? Are their composition comparable or completely different? A new study, presented at the Goldschmidt conference in Boston on August 15, 2018, helps shed light on the subject. It turns out that the "constituents" that make up the Earth are rather normal with the same elements, in the same proportion as material in planetary systems elsewhere.
The scientists involved have measured the compositions measured from 18 different planetary systems, up to 456 light-years away. They found many similarities between the composition of the planets in these systems and those of the Earth. The does not mean that all these planets are exactly like the earth, but that they are made up of the same elemental things as the earth in terms of elements. Like Dr. Siyi Xu from the Gemini Observatory in Hawaii said:
Most of the building blocks that we have looked at in other planetary systems have a composition that is very similar to Earth's.
Dr. Xu presented the new findings at the Goldschmidt conference. She added:
It is difficult to directly examine these distant bodies. Because of the long distances, nearby stars tend to drown out electromagnetic signals such as light or radio waves. So we had to look at other methods.
Dr. Xu's team investigated how these planetary building blocks influence the light that comes from white dwarf stars – small, dense stars that have burned most of their hydrogen and helium gases. She used spectrographs on the Keck telescope in Hawaii, the world's largest optical and infrared telescope, and the Hubble Space Telescope. After Dr. Xu:
White atmospheres of the White Dwarfs consist of either hydrogen or helium, which give a fairly clear and clean spectroscopic signal. However, as the star cools, it begins to collect material from the planets, asteroids, comets, etc., that have orbited it, some forming a dust disk, somewhat like the rings of Saturn. As this material nears the star, how we see the star changes. This change is measurable because it affects the spectroscopic signal of the star and allows us to identify the type and even the amount of material surrounding the white dwarf. These measurements can be very sensitive so that bodies as small as an asteroid can be detected.
In this study, we focused on the sample of white dwarfs with dust disks. We were able to measure the calcium, magnesium and silicon content in most of these stars and some other elements in some stars. Maybe we also found water in one of the systems, but we have not quantified it yet: it is likely that there will be a lot of water in some of these worlds. For example, we previously identified a star system 170 light-years away in the constellation Boothes, which was rich in carbon, nitrogen, and water and had a composition similar to that of Halley's Comet. In general, their composition is similar to Earth's mass.
This would mean that the chemical elements, the building blocks of the earth, are common in other planetary systems. From what we can see, in terms of the presence and proportion of these elements, we are normal, pretty normal. And that means that we can probably expect Earth-like planets elsewhere in our galaxy.
This work is ongoing and recently released data from the Gaia satellite, which has so far characterized 1.7 billion stars, has revolutionized the area. That means we will understand the White Dwarves much better. We hope to determine the chemical composition of the extrasolar planetary material with a much higher accuracy.
It has been discovered that other exoplanets look very different, from giant "hot Jupiter" to "super-Earth" (larger than Earth, but smaller than Uranus or Neptune) and small, rocky worlds Earth or Mars. If the total mass compositions of these planets are similar to our solar system, especially the Earth, as the evidence suggests, then that is a good indication that worlds that are really similar to Earth are probably out there, waiting to be discovered. Like Dr. Sara Seager, Professor of Planetary Science at the Massachusetts Institute of Technology, and the Deputy Science Director of the recently launched Mission Exits Transit Exoplanet Survey (TESS) said:
It's amazing to me that exoplanets are best studied inside torn and absorbed by its white dwarf star. It's great to see progress in this area of research and to have solid evidence that planets with Earth-like compounds are widespread – which reinforces our confidence that an Earth-like planet is waiting for a very close normal star out there to find] Source: Conclusions: According to a new study, the constituents that make up the Earth are the same elements in the same proportions as the material in other planetary systems.
Via Goldschmidt Conference