Source: Osorio et al.
Source: Osorio et al.
Young star XZ Tau B displays a dwarf protoplanetary disk which may
evolve up to five hundred times faster than bigger disks and display
observable changes in just a few months
In the course of the last few decades, the discovery of thousands of
planets around other stars has unveiled a wide variety of planetary
systems whose architecture defies our understanding of planet formation.
The search for disks of gas and dust around young stars, from which
planetary systems stem, is fundamental to explain newly observed worlds,
and a recent finding confirms that miniature systems can exist.
The discovery, made by an international team led by researchers from
the Institute of Astrophysics of Andalusia (IAA-CSIC), was made in the
vicinity of XZ Tau B star which, with less than five million years of
existence (the Sun, for comparison, is five billion years old), is so
young that it has not yet completed its contraction process.
"This young star is surrounded by a disk of gas and dust only three
Astronomical Units in radius, with a central cavity which seems to have
been created by protoplanets orbiting around it, says Mayra Osorio,
IAA-CSIC researcher in charge of the project. One Astronomical Unit is
the equivalent of the distance from the Earth to the Sun (150 million
kilometers). In comparison, the typical size of disks studied so far
oscillated between fifty and a hundred astronomic units".
With a size tens of times smaller than our Solar System, which is about
one hundred Astronomical Units long, the disk around XZ Tau B not only
confirms the models that indicated that dwarf disks could exist but it
also fits the finding by the Kepler satellite of extremely compact
systems, containing various planets the size of the Earth (or several
Earths) orbiting around their star inside a space no bigger than one
Astronomical Unit.
"The XZ Tau B disk could therefore be the precursor to these types of
compact systems and suggests that there could be a great number of very
small protoplanetary disks left to discover”, says Enrique Macías,
IAA-CSIC researcher involved in the finding. "Highly sensitive
instruments with a high spatial resolution such as ALMA, with which we
have studied XZ Tau B, are allowing us to study systems that now seem
borderline but which are undoubtedly much more common than we used to
think".
The XZ Tau B disk displays, moreover, two very interesting traits.
First, its small size implies that it will develop between fifty and
five hundred times faster than bigger systems. "Changes which in
heretofore observed disks would take decades or centuries to observe
will occur here in a matter of months. It is one of the very scarce
phenomena in Astrophysics where a full monitoring could be carried out
in human time scales”, says Mayra Osorio (IAA-CSIC).
The second characteristic trait of this disk resides in its belonging
to a triple stellar system. “It is known that the existence of companion
stars influences the size of protoplanetary disks, so the in-depth
study of this small disk will bring information not only about how
planets are formed but also about how multiple star systems emerge and
evolve over time,” says Enrique Macías.
Reference:
M. Osorio et al. "A dwarf transitional protoplanetary disk around XZ Tau B". The Astrophysical Journal Letters, 825, L10 (2016). http://dx.doi.org/10.3847/2041-8205/825/1/L10
Contact:
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Unidad de Divulgación y Comunicación
Silbia López de Lacalle - sll[arroba]iaa.es - 958230532
http://www.iaa.es
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