TESS found the first exoplanet in the thick disk of the milky Way

Astronomers have found in the data space Observatory TESS indications of the presence of extrasolar planets in the stars of the thick disk of the milky Way. Such objects in a given
the moment little is known, but for TESS it was the first such discovery, write the authors in the accepted
for publication in The Astronomical Journal
Preprint on the server arXiv.org.

Astronomers distinguish in our spiral galaxy the milky Way
several subsystems, of which the principal is a bulge, thin disk, thick disk
and halos. A bulge is a bulge in the Central region of the galaxy, the halo is
a spheroidal component surrounding the galaxy, and two kinds of disks,
populations of stars with different physical parameters. On the thin disk have
the absolute majority of lights: about 85 percent of visible close to the plane
The milky Way belongs to thin component.

One of the main differences between the thin and thick disk is
in the velocity dispersion: the speed of stars from the thin disk lying in a narrower
range. In other words, the temperature of the gas of the stars of the thin disc is less
than Tolstoy, and what determines their characteristic thickness in the perpendicular
the galactic plane direction. Highlighted a number of differences: on average, in the large
disk stars are older and less metallicky, i.e. it contains less elements
heavier than helium. The separation of thin and thick disc is mounted and
its existence I agree most of the scientific community, though
there are works in which the possibility of partitioning the entire set of stars on
two separate populations questioned.

At the moment there are more than four thousand exoplanets, but
only in a few cases the parent star were assigned to the thick disk (the first work, this conclusion was published in 2010).
It is believed that significantly higher speeds of movement of stars
a thick disk may affect the formation of planets around them, but
the moment the received data are insufficient to draw firm conclusions.

Astronomers from the UK, Spain, Italy, Canada, China, USA, France, Chile and Japan have discovered the first exoplanet, the star
thick disk in the data space telescope TESS — LHS 1815b. Around lights LHS 1815 times
in 3,1843 day turns planet, exceeding the Earth in size 1,088 ± 0,064 times.
Its weight for such a large radius is 4,2 ± 1,5 earth, but known with
great errors. The semi-major axis is 0.04 astronomical units, which is
only 17 times the radius of the star.

The star LHS 1815, has repeatedly come to the attention of TESS in
for the first two years of operation of the apparatus. A long series of observations allowed
to detect coating of small depth, which changes the radiation flux from the star just
0.04 per cent. The presence of the planet was confirmed by additional observations on
the HARPS spectrograph,
mounted on the 3.6-meter telescope at the Observatory of La Silla.

As TESS watches only bright enough stars, all studied
this tool also measured astrometric telescope Gaia, which with high
precision determines the coordinates and speed of the bodies. it Turned out that the LHS 1815 quickly
moves relative to the local standard of rest, i.e. the reference system,
moving around the center of the milky Way at an average speed of a substance near
Sun: about 110 kilometers per second to 15, the Sun.

The authors ‘ analysis shows that the measured
projection speed with high precision show that the LHS 1815 to
the thick disk, while no other stars that watched TESS, such a conclusion clearly
it was not done. At the moment LHS 1815 is located just 29.9 parsecs
Land that is close to the galactic plane, but is removed from it and the high has to rise
approximately 1.8 kiloparsec above it.

LHS 1815b is quite a good, though imperfect
candidate for observation with telescopes of the next generation, such as “James
Webb”. Meanwhile, continuing surveillance TESS needs
identify new extrasolar planets in stars of the thick disk. Getting a great
the sample of such objects will allow to study in detail the possible differences in
formation and evolution of planets orbiting stars of different component of the Galaxy.

Previously, astronomers found 11 candidates in the quark exoplanets first detected this object with a long and eccentric orbit and showed the planet that survived the expansion of the stars.

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