The European Gaia space mission has produced an unprecedented amount of new, improved, and detailed data for almost two billion objects in the Milky Way galaxy and the surrounding cosmos. The Gaia Data Release 3 on Monday revolutionizes our knowledge of the Solar System and the Milky Way and its satellite galaxies.
From: University of Helsinki
June 17, 2022 -- The
Gaia space mission of the European Space Agency ESA is constructing an
ultraprecise three-dimensional map of our Milky Way galaxy, observing almost
two billion stars or roughly one percent of all the stars in our galaxy. Gaia
was launched in December 2013 and has collected science data from July 2014. On
Monday, June 13, ESA released Gaia data in Data Release 3 (DR3). Finnish
researchers were strongly involved in the release.
Gaia data allows, for
example, for the derivation of asteroid and exoplanet orbits and physical
properties. The data helps unveil the origin and future evolution of the Solar
System and the Milky Way and helps understand stellar and planetary-system
evolution and our place in the cosmos.
Gaia revolves about its
axis slowly in about six hours and is composed of two optical space telescopes.
Three science instruments allow for accurate determination of stellar positions
and velocities as well as the spectral properties. Gaia resides at about 1,5
million kilometers from the Earth in the anti-Sun direction, where it orbits
the Sun together with the Earth in the proximity of the so-called Sun-Earth
Lagrange L2-point.
Gaia DR3 on June 13,
2022 was significant across astronomy. Some 50 scientific articles are being
published with DR3, of which nine articles have been devoted to underscoring
the exceptionally significant potential of DR3 for future research.
The new DR3 data
comprises, for example, the chemical compositions, temperatures, colors,
masses, brightnesses, ages, and radial velocities of stars. DR3 includes the
largest ever binary star catalog for the Milky Way, more than 150 000 Solar
System objects, largely asteroids but also planetary satellites, as well as
millions of galaxies and quasars beyond the Milky Way.
"There are so many
revolutionary advances that it is difficult to pinpoint a single most
significant advance. Based on Gaia DR3, Finnish researchers will change the
conception of asteroids in our Solar System, exoplanets and stars in our Milky
Way galaxy, as well as galaxies themselves, including the Milky Way and its
surrounding satellite galaxies. Returning to our home planet, Gaia will produce
an ultraprecise reference frame for navigation and positioning," says
Academy Professor Karri Muinonen from the University of Helsinki.
Gaia and asteroids
The ten-fold increase
in the number of asteroids reported in Gaia DR3 as compared to DR2 means that
there is a significant increase in the number of close encounters between
Gaia-detected asteroids. These close encounters can be utilized for asteroid
mass estimation and we expect a significant increase in the number of asteroid
masses to be derived by using Gaia DR3 astrometry, in particular, when combined
with astrometry obtained by other telescopes.
In the conventional
computation of an asteroid's orbit, the asteroid is assumed to be a point-like
object and its size, shape, rotation and surface light scattering properties
are not taken into account. The Gaia DR3 astrometry is, however, so accurate
that the angular offset between the asteroid's center of mass and the center of
the area illuminated by the Sun and visible to Gaia must be accounted for.
Based on Gaia DR3, the offset has been certified for asteroid (21) Lutetia
(Figure 2). The ESA Rosetta space mission imaged Lutetia during the flyby on
July 10, 2010. With the help of the Rosetta Lutetia imagery and ground-based
astronomical observations, a rotation period, rotational pole orientation, and
detailed shape model were derived. When the physical modeling is incorporated
into orbit computation, the systematic errors are removed and, contrary to
conventional computation, all observations can be incorporated into the orbit
solution. Consequently, the Gaia astrometry provides information about the
physical properties of asteroids. These properties need to be taken into
account using physical models or empirical error models for the astrometry.
The Gaia DR3 includes,
for the first time, spectral observations. The spectrum measures the color of
the target, meaning the brightness at different wavelengths. One especially
interesting feature is that the new release contains about 60 000 spectra of
asteroids in our Solar System (Figure 3). The asteroid spectrum contains information
on their composition and, thus, about their origin and the evolution of the
whole Solar System. Before the Gaia DR3, there has been only few thousand
asteroid spectra available, so Gaia will multiply the amount of data by more
than an order of magnitude.
Gaia and exoplanets
Gaia is expected to
produce detections of up to 20 000 giant exoplanets by measuring their
gravitational effect on the movement of their host stars. This will enable
finding virtually all Jupiter-like exoplanets in the Solar neighbourhood over
the coming years and determining how common are Solar System -like
architectures. The first such astrometric Gaia detection was a giant exoplanet
around epsilon Indi A, that corresponds to the nearest Jupiter-like exoplanet
only 12 light years away. The first such detections are possible because
acceleration observed in radial velocity surveys can be combined with movement
data from Gaia to determine the orbits and planetary masses.
Gaia and galaxies
The microarcsecond
resolution of Gaia DR3 provides precise measurements of the motions of stars,
not only within our own Milky Way galaxy, but also for the many satellite
galaxies that surround it. From the motion of stars within the Milky Way
itself, we can accurately measure its mass, and together with the proper motion
of satellites, we can now accurately determine their orbits. This lets us look
both into the past and into the future of the Milky Way galaxy system. For
example, we can find out which of the galaxies that surround the Milky Way are
true satellites, and which are just passing by. We can also investigate if the
evolution of the Milky Way conforms to cosmological models, and in particular,
whether the satellite orbits fit the standard dark matter model.
Gaia and reference
frames
The International
Celestial Reference Frame, ICRF3, is based on the position of a few thousand
quasars determined by Very Long Baseline Interferometry (VLBI) at radio
wavelengths. ICRF3 is used to obtain the coordinates of celestial objects and
to determine the orbits of satellites. Quasars of ICRF3 are also fixed points
on the sky that can be used to determine the precise orientation of the Earth
in space at any time. Without this information, for example, satellite
positioning would not work.
Gaia's data contain
about 1,6 million quasars, which can be used to create a more accurate
Celestial Reference Frame in visible light replacing the current one. In the
future, this will have an impact on the accuracy of both satellite positioning
and measurements of Earth-exploring satellites.
https://www.sciencedaily.com/releases/2022/06/220617165652.htm
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