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Blobrana


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Miniature solar systems
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New research led by a University of St Andrews astronomer has found evidence for what might be the raw material for the beginning of shrunken versions of our solar system -  miniature worlds in the making.
In their study Dr Alexander Scholz, SUPA Advanced Fellow at the University of St Andrews, and Professor Ray Jayawardhana, from the University of Toronto, challenge the assumption that other planetary systems in the Universe would necessarily look like our own solar system.

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Blobrana


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Astronomers find evidence of miniature solar systems in our galaxy
A new research by astronomers has found evidence for the existence of raw material for the beginning of miniature versions of our solar system.
According to the study by Dr Alexander Scholz, an astronomer from the University of St Andrews in Edinburgh, the birthplace of planets exist not only around young stars, but also around planemos (Planetary mass objects), that are not much larger or heavier than Jupiter.
This may imply the existence of miniature solar systems with a central object having only about 1% of the mass of the Sun.
But since their discovery in 2000, the nature and origin of planemos, has been more of a mystery because of the uncertainty that whether they are tiny stars or giant planets kicked out from a young planetary system.
The new study suggests that the former scenario is more likely.

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Imagine a solar system where planets encircle an object which itself is not much larger than a planet

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Blobrana


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Ophiuchus 162225-240515
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Title: Infrared Spectroscopy of the Ultra Low Mass Binary Oph 162225-240515
Authors: Alexis Brandeker, Ray Jayawardhana, Valentin D. Ivanov, Radostin Kurtev

Binary properties are an important diagnostic of the star and brown dwarf formation processes. While wide binaries appear to be rare in the sub-stellar regime, recent observations have revealed Ophiuchus 162225-240515 (2MASS J16222521-2405139) as a likely young ultra-low-mass binary with an apparent separation of ~240 AU. Here, we present low-resolution near-infrared spectra of the pair from NTT/SOFI (R~600) and VLT/ISAAC (R~1400), covering the 1.0-2.5um spectral region. By comparing to model atmospheres from Chabrier & Baraffe and Burrows et al., we confirm the surface temperatures to be T_A = (2350±150) K and T_B = (2100±100) K for the two components of the binary, consistent with earlier estimates from optical spectra. Using gravity sensitive K I features, we find the surface gravity to be significantly lower than field dwarfs of the same spectral type, providing the best evidence so far that these objects are indeed young. However, we find that models are not sufficiently reliable to infer accurate ages/masses from surface gravity. Instead, we derive masses of M_A = 13 (+8/-4) M_J and M_B = 10 (+5/-4) M_J for the two objects using the well-constrained temperatures and assuming an age of 1-10 Myr, consistent with the full range of ages reported for the Oph region.

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Blobrana


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Oph 162225-240515AB
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Near-infrared image of the system Oph 162225-240515AB, obtained with ISAAC on ESO's Very Large Telescope. North is up and East is to the left. The apparent separation is less than 2 arcseconds, corresponding to 242 times the distance between the Earth and the Sun (242 astronomical units) at the distance of the system, 400 light-years.

Oph162225-240515AB
Credit ISAAC/VLT

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Blobrana


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Posts: 131433
Date:
Oph 162225-240515
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A pair of strange new worlds that blur the boundaries between planets and stars have been discovered beyond our Solar System.

A few dozen such objects have been identified in recent years but this is the first set of "twins".
Dubbed "planemos", they circle each other rather than orbiting a star.
The two objects have similar spectra and colours, suggesting that they formed at the same time about a million years ago.
They are separated by about six times the distance between the Sun and Pluto, and can be found in the Ophiuchus star-forming region some 400 light years away.
The planemos have similar masses to many of the giant planets discovered beyond our Solar System (the largest weighs in at 14 times the mass of Jupiter and the other is about seven times more massive).
Oph 162225-240515 was discovered using the ESO's New Technology Telescope at La Silla, Chile. Follow-up studies were conducted with the ESO's Very Large Telescope.

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Blobrana


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Posts: 131433
Date:
Planemos
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Two free-floating objects have been found orbiting each other for the first time. The find raises questions about how such small objects could form.

Bodies that have the mass of a planet but are not bound to a star are called planetary mass objects, or "planemos". Astronomers are not sure how they form since planets such as those in our solar system took shape from a disc of gas and dust around a star.

One idea is that they are actually embryonic stars that got kicked out of their natal clouds early. Starved of fuel for further growth, they never grew beyond the mass of a planet. But the newly discovered pair of planemos challenges this scenario.
The system, called Oph 16225-240515, is about 400 light years from Earth. It had previously been identified as a possible free-floating planemo, but now it has been found to be a pair of such objects.
The discovery was made by Ray Jayawardhana of the University of Toronto, Canada, and Valentin Ivanov of the European Southern Observatory in Santiago, Chile. They used the Very Large Telescope in Paranal to obtain images and light spectra of the objects.
The researchers calculate that the objects are about 7 and 14 times the mass of Jupiter, respectively. They appear to be about 240 astronomical units apart – 1 AU is the distance between the Earth and the Sun.
The two are only very weakly bound to each other by gravity because they are relatively far apart and have relatively low masses. This casts doubt on the embryonic-star ejection hypothesis, because the pair would likely have been torn from each other by such a violent event, the team notes.

"It should not have survived such a chaotic birth. It provides one of the most extreme tests of the ejection model." - Ray Jayawardhana.

Instead, the discovery suggests that planemos form like stars, in cold clouds of gas. In this scenario, they come by their puny size simply because the gas clouds are relatively small to begin with, not because they were ejected.

Journal reference: Science (DOI: 10.1126/science.1132128)

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