Hubble's successor will study hot Jupiters, brown dwarfs and exoplanets. Why are they interesting?

More about the Roman telescope and mission

NASA has officially named its next receiver "Hubble". Previously

known as wide-angle infraredSurvey Telescope (WFIRST), this project has now received a new name - Nancy Grace Roman Space Telescope - or simply Roman Space Telescope - after the first chief astronomer of NASA, which is often called "Mother of Hubble."

Roman Space Telescope should be launched inmid-2020s as the successor to the aging Hubble. Despite the fact that they are equipped with a mirror of the same size - 2.4 m wide, the new telescope uses a wide-angle instrument to study a region of the sky that is 100 times larger than that which Hubble can capture.

When observing the universe in infraredrange, the Roman Space Telescope will have several primary targets. The first is to search for and study exoplanets using spectroscopy and an experimental coronography tool to produce high-contrast images of these worlds.

He also explores dark energy, mysteriousa force that appears to be causing the expansion of the universe to accelerate. The Roman Space Telescope can also help study dark matter and a range of other astrophysical topics.

What will the telescope study?

Japanese and American scientists have calculated thatNASA's Nancy Grace Roman Space Telescope will find about 10 hot Jupiters and 30 brown dwarfs closer to the center of the galaxy using the effect of gravitational lensing.

The telescope will primarily usegravitational microlensing method. The essence of the method is as follows: when a massive object, such as a star, passes in front of a more distant star (in relation to the telescope), light from the more distant star will be refracted.

As a result, the closer object acts likenatural lens, magnifying the light from the background star. Planets orbiting a lens star can produce a similar effect on a smaller scale, so astronomers aim to detect them by analyzing light from a farther star.

Since the method helps to detect evensmall planets with a wide range of orbits, scientists expect a survey of the new telescope to reveal analogs of almost every planet in our solar system. And also more exotic worlds - giant planets in tiny orbits known as hot Jupiters, and so-called "failed stars" - brown dwarfs.

Brown dwarfs

Brown dwarfs are substellar objects (with masses ranging from 0.012 to 0.0767 solar masses, or, respectively, from 12.57 to 80.35 Jupiter masses).

As in stars, thermonuclear reactions take place in them.nuclear fusion on the nuclei of light elements (deuterium, lithium, beryllium, boron), but, unlike main sequence stars, the contribution to the heat release of such stars from the nuclear fusion of hydrogen nuclei (protons) is insignificant.

In brown dwarfs, unlike the stars of the mainsequence, there are also no spherical layers of radiant energy transfer - heat transfer in them is carried out only due to turbulent convection, which determines the homogeneity of their chemical composition over depth.

Brown dwarf (smaller object) rotatingaround the star Gliese 229, which is located in the constellation Hare about 19 light-years from Earth. The brown dwarf Gliese 229B has a mass of 20 to 75 Jupiter masses.

One of the mechanisms of origin of browndwarfs are similar to planetary. A brown dwarf forms in a protoplanetary disk on its outskirts. At the next stage of their life, under the influence of the surrounding stars, they are thrown into the surrounding space of their parent star and form a large population of independent objects.

Like ordinary stars, brown dwarfs canbe formed independently of other objects. They can form individually or in close proximity to other stars. In 2015, a group of forming brown dwarfs were studied, and some of them showed the same jets as more massive stars in the process.

Unlike main sequence stars,the minimum surface temperature of which is about 4000 K, the temperature of brown dwarfs lies in the range from 300 to 3000 K. Unlike stars, which heat themselves up due to the thermonuclear fusion taking place inside them, brown dwarfs constantly cool down throughout their life, while the larger the dwarf, the slower it cools.

Properties of brown dwarfs, transitional betweenplanets and stars by mass, are of particular interest to astronomers. A year after the discovery of the first object of this class, weather phenomena were discovered in the atmospheres of brown dwarfs. It turned out that brown dwarfs can also have their own moons.

Hot Jupiters

Hot Jupiters are a class of exoplanets with massof the order of the mass of Jupiter (1.9⋅1027 kg). Unlike Jupiter, which is 5 AU away. from the Sun, a typical hot Jupiter is located at a distance of about 0.05 AU. from the star, that is, one order of magnitude closer than Mercury from the Sun and two orders of magnitude closer than Jupiter.

Hot Jupiters once occupieda significant part of the list of open exoplanets, since they are the easiest to detect, since they introduce noticeable short-period disturbances in the motion of the star, which can be detected by the displacement of the spectral lines.

In addition, the probability of the planet passing in front of the star's disk is quite high, which makes it possible to estimate the planet's size from the decrease in the star's luminosity.

Artistic representation of the hot extrasolar planet XO-1 b

Specifications:

  • Heating the surface to a temperature of 1000-1500 K(and sometimes up to almost 3000 K), due to their proximity to the star, causes additional thermal expansion, so that the radii of such planets are larger than those of similar ones, but located at a greater distance from the parent star.
  • The eccentricity of the orbit is usually close to zero as it decreases due to tidal forces.

It is believed that near the star itself is not enoughmaterial for the formation of planets. All planets of this type were formed in the outer part of the system, and then migrated to the center due to deceleration in the gas-dust disk.

There is also a subclass of hot Jupiters called short-period hot Jupiters. They are "hot-hot" Jupiters, that is, the hottest Jupiters closest to the stars.

The period of rotation of such planets around the staris 1-2 days, and the temperature can often reach 2000 ° C (while the surface temperature of the star itself is often only 2-3 times the temperature of the planet's surface). The hottest short-period hot Jupiter (as well as the hottest known exoplanet) is WASP-33 b.

At a very small distance to the star and not veryWith a large planet mass (less than 2 Jupiter masses), the planet is not kept from warming up by its gravity, which leads to its strong thermal expansion and a drop in density to extremely low values. Such a planet is more of a gas cloud than a full-fledged planet and is called a loose planet.

Exoplanets

Exoplanet - a planet outside the Sunsystems. For a long time, the task of detecting planets near other stars remained unresolved, since the planets are extremely small and dim in comparison with the stars, and the stars themselves are far from the Sun (the closest is at a distance of 4.24 light years). The first exoplanets were discovered in the late 1980s.

Now such planets began to be discovered thanks toadvanced scientific methods are often at their limits. As of January 6, 2021, the existence of 4396 exoplanets in 3242 planetary systems has been reliably confirmed, of which 720 has more than one planet.

Number of reliable exoplanet candidatesmuch bigger. So, for the Kepler project in January 2020, there were 2,420 more candidates, and for the TESS project for January 2020, 1,082 candidates, however, to obtain the status of confirmed planets, they must be re-registered using ground-based telescopes.

The total number of exoplanets in the Milky galaxyThe path is estimated at no less than 100 billion, of which 5 to 20 billion are possibly "earthlike". Also, according to current estimates, about 34% of sun-like stars have planets in the habitable zone that are comparable to Earth.

The total number of planets outside the solar system,resembling Earth and discovered as of August 2016, is 216. At the end of October 2020, scientists calculated the total number of possible habitable exoplanets in the Milky Way galaxy, their number is about 300 million.

The vast majority of discovered exoplanetsdetected using various indirect detection techniques rather than visual observation. Most of the known exoplanets are gas giants and are more like Jupiter than Earth. This is due to the limited detection methods (short-period massive planets are easier to detect).

Animation of the chronology of the discovery of exoplanets.The dot color indicates the opening method. The horizontal axis is the size of the semi-major axis. The vertical axis is mass. For comparison, the planets of the solar system are marked in white

Scientists predict that only in the galaxyThe Milky Way (where our planet Earth is located), according to the latest data, their number is about 300 million. Inhabited planets mean the presence of microbes, plants and animals on them, but not necessarily civilizations or other intelligent life.

Calculations of scientists have shown that if in the nextdecades, at least one planet with possible traces of life will be discovered, this will mean that there are other similar worlds in our galaxy with a probability of 95-97%.

The discovery of exoplanets allowed astronomers to makeconclusion: planetary systems are a widespread phenomenon in space. Until now, there is no generally accepted theory of the formation of planets, but now, when it is possible to sum up statistics, the situation in this area is changing for the better.

Most of the detected systems are very differentfrom the solar - most likely, this is due to the selectivity of the methods used (the easiest way to detect short-period massive planets). In most cases, planets similar to the Earth, and smaller in size, at the moment (August 2012), can only be detected by the transit method.

What are the goals of the new Roman telescope program?

Since the method helps to detect evensmall planets with a wide range of orbits, scientists expect a survey of the new telescope to reveal analogs of almost every planet in our solar system. And also more exotic worlds - giant planets in tiny orbits known as hot Jupiters, and so-called "failed stars" - brown dwarfs.

Previous planet-hunting missions infirst of all, they were looking for new worlds relatively close to us, at a distance of up to several thousand light years. Close proximity makes more detailed study possible. However, astronomers believe that studying bodies close to the core of our galaxy could provide new insights into how planetary systems evolve.

Unlike the stars in the disk of the galaxy, whichare at comfortable distances from each other, the stars near the core are much denser. Roman could figure out if this close arrangement of stars affects the orbits of the planets. If a star passes close to a planetary system, its gravity could push the planets out of their normal orbits.

Supernovae are also more common near the center.galaxies. These catastrophic events are so intense that they can create new elements that are released into the environment when the exploding stars die. Astronomers believe that this could affect the formation of planets.

Finding worlds in this region can help us learn more about the factors that influence planetary formation.

When will the telescope start working?

Roman Space Telescope has already received the green lightfor development and testing. However, this will most likely only start after 2021, because NASA plans to focus its attention and budget on first completing the James Webb Space Telescope, which is scheduled to launch in 2021.

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