Astronomers search universe for planets

Most of us are familiar with the planets Earth, Mercury, Mars, Venus, Saturn, Neptune, Uranus and Jupiter and the dwarf planet Pluto, but there are many more planets in the universe, a Mount Hopkins astronomer explained to Green Valley listeners Tuesday.

Emilio Falco, a staff astronomer at the Fred Lawrence Whipple Observatory on Mount Hopkins, said there may be more than 300 of these exoplanets that have been discovered.

Some orbit sun-like stars and some, a small number, are “free-floating planets,” sometimes called rogue or interstellar planets. They’re not a part of a solar system like our sun’s system. The first one of those was discovered in 1992.

Falco talked about exoplanets at the Smithsonian Astrophysicial Observatory’s astronomy lecture. There’s just one more of these periodic lectures in this year’s series.

There are several studies aimed at finding exoplanets, including project MEarth at the Smithsonian observatory here.

The study of all the planets outside the solar system is called exoplanetology.

Some of the ways exoplanets are discovered and observed include:

Astrometery, or precisely measuring a star’s position in the sky and see how it changes positions over time. The host star will wobble a bit due to the planet’s gravitational tug on it.

The Doppler method that measures the speed of a star as it moves toward or away from the Earth. That’s done by studying the parent star’s spectral lines. The lines in a star’s spectrum vary as the star speeds away or toward the earth.

The transit method, which measures the amount a star’s light is dimmed by a planet passing in front of it.

Both the huge MMTO 21-foot telescope and the HAT — for Hungarian-made automated telescope — network of optical reflector telescopes are used in the search for exoplanets.

The final Smithsonian star lecture will take place at 9 a.m. Wednesday, March 26.

Faith Vilas, director of the MMTO observatory will be the speaker, but she’ll be talking about data from the Messenger spaceship mission to the planet Mercury, and not the large multiple mirror telescope here..

The lectures are free.

jlamb@gvnews.com | 547-9749