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Post Info TOPIC: HIP 56948
Blobrana


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Title: The remarkable solar twin HIP 56948: a prime target in the quest for other Earths
Authors: Jorge Melendez, Maria Bergemann, Judith G. Cohen, Michael Endl, Amanda I. Karakas, Ivan Ramirez, William D. Cochran, David Yong, Phillip J. MacQueen, Chiaki Kobayashi, Martin Asplund

We study HIP 56948, the best solar twin known to date, to determine with an unparalleled precision how similar is to the Sun in its physical properties, chemical composition and planet architecture. We explore whether the abundances anomalies may be due to pollution from stellar ejecta or to terrestrial planet formation.
We perform a differential abundance analysis (both in LTE and NLTE) using high resolution (R = 100,000) high S/N (600) Keck HIRES spectra of the Sun and HIP 56948. We use precise radial velocity data from the McDonald and Keck observatories to search for planets around this star.
We achieve a precision of sigma = 0.003 dex for several elements. Including errors in stellar parameters the total uncertainty is as low as sigma = 0.005 dex (1 %), which is unprecedented in elemental abundance studies.
The similarities between HIP 56948 and the Sun are astonishing. HIP 56948 is only 17±7 K hotter than the Sun, and log g, [Fe/H] and microturbulence are only +0.02±0.02 dex, +0.02±0.01 dex and +0.01±0.01 km/s higher than solar, respectively. HIP 56948 has a mass of 1.02±0.02 solar masses and is 1 Gyr younger than the Sun. Both stars show a chemical abundance pattern that differs from most solar twins. The trend with T_cond in differential abundances (twins - HIP56948) can be reproduced very well by adding 3 Earth masses of a mix of Earth and meteoritic material, to the convection zone of HIP 56948. From our radial velocity monitoring we find no indications of giant planets interior to or within the habitable zone of HIP 56948.
We conclude that HIP 56948 is an excellent candidate to host a planetary system like our own, including the possible presence of inner terrestrial planets. Its striking similarity to the Sun and its mature age makes HIP 56948 a prime target in the quest for other Earths and SETI endeavours.

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Blobrana


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Title: HIP 56948: A Solar Twin With a Low Lithium Abundance
Authors: Jorge Melendez (RSAA/ANU), Ivan Ramirez (McDonald/U.Texas)

For more than a decade, 18 Sco (HD 146233) has been considered the star that most closely resembles the Sun, even though significant differences such as its Li content, which is about three times solar, exist. Using high resolution, high S/N spectra obtained at McDonald Observatory, we show that the stars HIP 56948 and HIP 73815 are very similar to the Sun in both stellar parameters and chemical composition, including a low Li abundance, which was previously thought to be peculiar in the Sun. HIP 56948, in particular, has stellar parameters identical to solar within the observational uncertainties, being thus the best solar twin known to date. HIP 56948 is also similar to the Sun in its lack of hot Jupiters. Considering the age of this star (1+/-1 Gyr older than the Sun) and its location and orbit around the Galaxy, if terrestrial planets exist around it, they may have had enough time to develop complex life, making it a prime target for SETI.

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HD 101364

HIP 56948 (HD 101364)
Position(2000): RA 11 40 28.4831 Dec +69 00 30.605

HIP 56948.kmz
Google Sky file



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Blobrana


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Peruvian astronomers Jorge Melendez of The Australian National University and Ivan Ramirez of The University of Texas at Austin have discovered the best solar twin to date, using the 2.7-meter Harlan J. Smith Telescope at McDonald Observatory. Their findings suggest that the Suns chemical composition is not unique, as some previously thought.
The star, HIP 56948, is more like the Sun than any yet seen, and is 200 light-years away in the constellation Draco, the dragon. The star may be a billion years older than the Sun.
Only three solar twins were previously known: 18 Scorpius, HD 98618, and HIP 100963. But while they were all like the Sun in many ways, there was one major difference: the amount of lithium they contained. They all had several times more than the Sun. Astronomers wondered if the Sun was unique in its low amount of lithium.
The discovery of this new solar twin puts that question to rest: it has the same low lithium content as the Sun. The study turned up another solar twin, HIP 73815, that contains a similarly low amount of lithium.
The question of chemical peculiarities in the Sun is related to the anthropic principle is there something special about the Sun that has allowed life to spring up in our solar system? Their findings dont answer that completely, but they do show that when it comes to the Suns chemical composition, the answer is an emphatic no.

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Blobrana


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HD 101364
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Astronomers have identified a yellow star they say is the best twin to our own sun yet seen.
In other words, its a star thats almost identical to the sun. And thats interesting because our sun shines on a life-bearing planet.
But stars like the sun are rare, according to astronomers. They account for only 4 percent of all stars in our Milky Way galaxy. And stars exactly like our sun must be even more rare. Scientists reported the previously best known example a star named 18 Scorpii ten years ago.

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Blobrana


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Posts: 131433
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HIP 56948
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Astronomers have found the most Sun-like star yet, and they say it is an ideal place to hunt for alien civilisations.
The star, called HIP 56948, lies a little more than 200 light years from Earth. Its size, mass, temperature, and chemical makeup are all so similar to the Sun's that no measurable differences could be found in high-resolution observations made by the 2.7-metre telescope at the McDonald Observatory in Texas, US.
The analysis was carried out by Jorge Melendez of Mount Stromlo Observatory in Weston Creek, Australia, and Ivan Ramirez of the University of Texas in Austin, US.
Other very Sun-like stars have previously been identified, including 18 Scorpii, HD 98618, and HIP 100963. But those three stars have several times more lithium than the Sun, while HIP 56948 is almost identical to the Sun in this respect as well, making it an even closer match.

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