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Hobby-Eberly Telescope finds the...

123rd Planet Beyond the Solar System

Hobby-Eberly Telescope in a University of Texas at Austin photo by Thomas A. Sebring.
The Hobby-Eberly Telescope looks out at dusk from Mt. Fowlkes in the Davis Mountains in a University of Texas at Austin photo by Thomas A. Sebring.
Astronomers using the Hobby-Eberly Telescope in Texas have discovered the 123rd exoplanet. This one is a planet orbiting a star near the bright star Betelgeuse in the constellation Orion.

Without actually seeing the planet, the astronomers deduced its presence by noting how much the star wiggled.

The star is about 140 lightyears away from Earth and our Solar System. That is some 800 trillion miles.  lightyears explained  »»

An exoplanet is a planet in a star system beyond our own Solar System.

The planet, designated HD 37605b, is a gas giant like our system's largest planet, Jupiter. However, it has at least 2.8 times the mass of Jupiter.

HD 37605b zips around its star once every 54 days. Its star is near the bright star seen from Earth known as Betelgeuse.

The Hobby-Eberly Telescope...

The Hobby-Eberly Telescope, part of McDonald Observatory on Mt. Fowlkes in the Davis Mountains, 450 miles west of Austin, Texas, is a joint project of three American and two German universities: The Hobby-Eberly Telescope was designed to gather a very large amount of light for spectroscopy. It has 91 hexagonal mirrors collecting light across a surface 30 feet across. Currently, HET is the world's third largest optical telescope.

Each of the 91 hexagonal mirrors weighs about 250 lbs. and is spherically shaped, like a contact lens. A sensor is centered 26 meters from the mirror at the top of a tower called the Center of Curvature Alignment Sensor Tower.


The Hobby-Eberly Telescope is designed for spectroscopy, a scientific technique discovered in 1814 by Joseph von Fraunhofer. He identified those curious dark bands that are found in the spectrum of light that has passed through a narrow opening and then a prism.

Those dark areas correspond to a reduction or absence of energy at particular wavelengths of light. By studying its bands, scientists gain knowledge about a source of light.

Astronomers refer to the bands as spectral lines. A line represents the specific frequency of light given off by an atom or molecule.

Astronomers learn the chemical composition of stars, and interstellar gas and dust, by comparing the known spectral lines of atoms and molecules on Earth with lines seen in light coming from those sources across the Universe.

It has been said that most modern astronomical knowledge would not be known if the optical spectroscope had not been invented.

The Hobby-Eberly Telescope has three spectrographs with low, medium and high resolution.
At 11.1 meters by 9.8 meters, the primary mirror is the largest to date. Its effective aperture is 9.2 meters. Only part of the mirror is used for any one observation.

HET began commissioning in 1997 and science operations in 1999.

Tracking stars...

Because Earth spins, stars seem to move across the sky. That forces astronomers to move their telescopes to track stars.

Other telescopes are pointed up and down and moved around to compensate for the rotation of Earth. That way, stars remain centered in a telescope's eyepiece.

The Hobby-Eberly Telescope, on the other hand, tracks objects by moving its sensor around above the mirror. As a star moves overhead, its light bounces off of the large stationary mirror and the sensor moves to catch it.

McDonald Observatory...

The Hobby-Eberly Telescope can see 70 percent of the sky visible from McDonald Observatory in the Davis Mountains.

The observatory has four telescopes for imaging and spectroscopy of both optical and infrared light: McDonald Observatory operates a lunar ranging station. It hosts one of four global-network Robotic Optical Transient Search Experiment (ROTSE) telescopes. The observatory is a Monitoring Network of Telescopes (MONET) site.

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