Wednesday, January 10, 2018

First PEPSI Data Release

The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first batch of high-spectral resolution data to the scientific community. In a series of three papers in the European journal Astronomy & Astrophysics, the PEPSI team presents a new spectral atlas of the Sun, a total of 48 atlases of bright benchmark stars, and a detailed analysis of the chemical abundances of the 10-billion year old planet-system host Kepler-444.

Spectral atlases are the fingerprints of stars and give insights into almost all of their physical properties like temperature, pressure, velocities and chemical composition. The first paper contains a new spectral atlas of the Sun and proves for the first time that a night-telescope instrument can reach a quality comparable to a specialized solar instrument. All solar and stellar spectra were taken with an unprecedented spectral resolution of λ/Δλ=250,000, a resolution equivalent to a 1/100th of the diameter of a hydrogen atom (λ being the wavelength and Δλ the smallest measurable separation of two wavelengths) and cover the entire optical and near-infrared light (from 383 to 914nm).
The fingerprint of a star.
Example from the new PEPSI atlases:
the nearby planet-host star epsilon Eridani.
Click here for a full resolution pdf version.

For the Sun several spectral time series with up to 300 individual spectra per day were pre-analyzed and are also provided to the community. "These data recover the well-known solar 5-minute oscillation at a peak of 3 mHz (5.5min) from the disk-averaged light with a radial-velocity amplitude of only 47 cm/s, an incredibly small velocity from a stellar point of view", says Prof. Strassmeier, PEPSI principal investigator and director of the Cosmic Magnetic Field branch at the Leibniz Institute for Astrophysics Potsdam (AIP). The new atlas was also used to re-determine the abundance of Lithium in the Sun with very high precision. "Lithium is a key element for the nucleosynthesis in the universe and is also a tracer of mixing processes inside stars", explains Dr. Matthias Steffen, one of the project scientists. Three-dimensional dynamic model atmospheres and a full statistical treatment of the spectral properties of the lithium atom were applied to determine the solar abundance.

The 48 stellar atlases in the second paper include the northern Gaia benchmark stars as well as other Morgan-Keenan standard stars. Spectra of these targets were not available at the given resolution and signal-to-noise ratio (S/N) before. The latter quantity represents the photon noise relative to the signal strength from the star and thus the quality of the spectra. Previously available S/N for work on astrophysical parameters was typically several hundred at a spectral resolution λ/Δλ of at most 100,000. "PEPSI and the LBT provide S/N of several thousand at on average three times higher spectral resolution", says Ilya Ilyin, PEPSI’s project scientist. "With such numbers we have now the typical daytime solar-like spectrum quality available also for bright stars at night time", adds Strassmeier.

The PEPSI instrument at LBT. Credit: AIP
Finally, in the third paper, the star "Kepler-444", hosting five sub-terrestrial planets, was confirmed to be 10.5 billion years old, more than twice the age of our Sun and just a little bit younger than the universe as a whole. The star is also found being poor on metals. The chemical abundance pattern from the PEPSI spectrum indicates an unusually small iron-core mass fraction of 24% for its planets if star and planets were formed together. For comparison, terrestrial planets in the solar system have typically a 30% iron-core mass fraction. “This indicates that planets around metal-poor host stars are less dense than rocky planets of comparable size around more metal-rich host stars like the Sun”, explains Claude “Trey” Mack, project scientist for the Kepler-444 observation.

Science contacts:
    Prof. Dr. Klaus G. Strassmeier, 0331-7499-223,    
    Dr. Ilya Ilyin, 0331-7499-269,
    Dr. Christian Veillet (Large Binocular Telescope Observatory), +1 (520) 621-5286,

Media contact:
    Dr. Janine Fohlmeister, 0331-7499-803,

More information on PEPSI and the LBT:

Thursday, January 4, 2018

'SHARKs' will Help LBT Hunt for Exoplanets

Two new instruments will give the Large Binocular Telescope a set of sharper eyes capable of studying planets outside our solar system in greater detail.

A pair of new-generation instruments to be mounted on the world's largest optical telescope, the Large Binocular Telescope, or LBT, located on top of Mount Graham in Arizona, will turn the telescope into a formidable hunter of extrasolar planets. Named SHARK (short for System for coronagraphy with High order Adaptive optics from R to K band), the instruments will enable astronomers to obtain direct images of exoplanets, including very faint ones, by more effectively blocking the otherwise overpowering light from their host stars.

INAF, the Italian National Institute for Astrophysics, is leading the international consortium that will build the instruments and will also manage their scientific use.

SHARK recently has received the official green light from the LBT board, and the two instruments are expected to become fully operational by the end of 2019. SHARK consists of a pair of instruments working synergistically in visible light (SHARK-VIS) and in the near infrared (SHARK-NIR). These will be operated in parallel, taking advantage of the two big 8.4-meter mirrors of the LBT, thus making it the first telescope in the world capable of observing exoplanets simultaneously over such a wide range of wavelengths.

The main problem exoplanet hunters face when studying exoplanets is the extreme contrast between the planets' faintness in comparison to their host stars' light, explains Christian Veillet, director of the Large Binocular Telescope, which is managed by the University of Arizona.

To be able to study candidates for potentially Earth-like planets, for example, astronomers need more sophisticated instruments to tease out the signal from the noise.

The "SHARKs" will take full advantage of the outstanding adaptive optics system mounted on the LBT, which was also developed by INAF. This system corrects in real time the image distortions induced by the atmospheric turbulence to deliver final frames that are characterized by a sharpness and quality of detail better than those obtainable with the Hubble Space Telescope.

"LBT’s Adaptive Optics is currently undergoing a makeover offering even better performance, which will be fully utilized by SHARK to bring the LBT to the forefront of what is possible in this arena," Veillet says. "We are preparing the path to doing unprecedented science on the next generation of telescopes, such as the Giant Magellan Telescope, an LBT on steroids with seven 8.4-meter mirrors on the same mount instead of two."

"With SHARK, we will observe exoplanets at unprecedented angular resolution and contrast, so that we will be able to go closer to their host stars than what has been achieved up to now with direct imaging," says Valentina D’Orazi of the INAF-Osservatorio Astronomico di Padova, instrument scientist for SHARK-NIR. "This will be possible thanks to the use of coronagraphy, which blocks out the light from the central star and highly improves the contrast in the region around the source, thus allowing us to detect the planetary objects we want to study, which otherwise would remain hidden in the star light.”  


 "With this great combination, we will finally be able to reveal many exoplanets around stars in our galactic neighborhood and better characterize their properties, by also using images in optical light taken for the first time in the northern hemisphere," adds Fernando Pedichini of the INAF-Osservatorio Astronomico di Roma and principal investigator of SHARK-VIS.


With SHARK, it will be possible to directly image gaseous giants in the outer regions of exoplanetary systems, thus obtaining pieces of information about the architecture of such systems that are complementary to those provided by techniques purely focused on detection. Such techniques include observing the gravitational tug unseen planets exert on their host star, or the minuscule dip in a star's brightness when a planet passes in front of it.

"These observations are key to understanding the formation mechanisms of planetary systems," says Simone Antoniucci of the INAF-Osservatorio Astronomico di Roma, instrument scientist of SHARK-VIS. "Moreover, one of the unique features of SHARK will be the capability to directly observe the formation process of giant planets around very young stars."

"Thanks to the outstanding sensitivity of the LBT adaptive optics system, SHARK-NIR, used in parallel with SHARK-VIS and the LBTI LMIRCAM instrument, will allow us to study not only exoplanets, but also astrophysical phenomena," says Jacopo Farinato, astronomer at the INAF-Osservatorio Astronomico di Padova and principal investigator of SHARK-NIR. "For instance, we will be able to study with formidable accuracy disks and jets of young stars, gas envelopes around evolved stars, asteroids and minor bodies of the solar system and even the brightest extragalactic sources such as active galactic nuclei."

"While these two SHARKs are built as instruments to be operated by the teams who built them, they will be open to the whole LBT community," Veillet adds. "Both teams have garnered an impressive scientific collaboration, covering the wide range of potential scientific programs as well as the diverse partnership on which LBT is built."

Each SHARK will be installed on one side of the LBT Interferometer (LBTI), the green structure seen in the middle of the picture between the two main mirrors of LBT. 
The SHARK consortium is led by INAF, and the partners for the NIR channel are the Steward Observatory in Tucson (University of Arizona), the Max Planck institute of Heidelberg (Germany) and the Institut de Planétologie et d’Astrophysique of Grenoble. The Italian institutes involved in the instrument construction are the Observatories of Padova, Roma, Arcetri, Milano, Trieste and the Physics and Astronomy department of the University of Padova.

The Large Binocular Telescope (LBT) is an international collaboration of the University of Arizona, Italy's National Institute for Astrophysics (INAF), Germany's LBT Beteiligungsgesellschaft, The Ohio State University, the Tucson–based Research Corporation representing the University of Minnesota, the University of Virginia, and the University of Notre Dame.  INAF contributes 25 percent of the LBT costs (construction and management) and owns one fourth of the telescope and of the same share of observing time.

Contact Information

At INAF, Italy:
Marco Galliani Chief Press Officer - INAF (Italian National Institute for Astrophysics)
office phone +39 06 355 33 390  mobile +39 335 17 78 428

At LBTO (Tucson, AZ)
Christian Veillet -  - 1 (520) 349 4576

The INAF Press Release (in Italian) is here.