MORE PLANETS EARTH SCIENCE

Dwarf planets are a lot like regular planets: They both have enough mass and gravity to be nearly round - unlike odd-shaped asteroids. They both travel through space in a path around the sun. Dwarf Planets

The big difference? A dwarf planet's path around the sun is full of other objects like asteroids and comets. A regular planet has a clear path around the sun. Most of the major impacts with other objects in its orbit happened billions of years ago. There is not much left over to get in the way. There may be dozens of dwarf planets in our solar system.

CERES Ceres is the largest object in the asteroid belt between Mars and Jupiter and the only dwarf planet located in the inner solar system. Even though Ceres comprises 25 percent of the asteroid belt's total mass, tiny Pluto is still 14 times more massive. It also is the first dwarf planet to be visited by a spacecraft - NASA's Dawn mission.

PLUTO Since its orbit is so elliptical, when Pluto is close to the sun, its surface ices sublimate, changing directly from solid to a gas, and rise and temporarily form a thin atmosphere. Pluto is classified as a dwarf planet and is also a member of a group of objects that orbit in a disc-like zone beyond the orbit of Neptune called the Kuiper Belt. This distant realm is populated with thousands of miniature icy and rocky worlds, which formed early in the history of our solar system. Discovered in 1930, Pluto was long considered our solar system's ninth planet. But after the discovery of similar intriguing worlds deeper in the distant Kuiper Belt, icy Pluto was reclassified as a dwarf planet.

The dwarf planet is often so far from the sun that its atmosphere collapses and freezes on the surface in an icy glaze. The coating gleams brightly, reflecting as much sunlight as freshly fallen snow. Scientists believe surface temperatures to vary from about -359 degrees Fahrenheit to -405 degrees Fahrenheit. The thin atmosphere will thaw in hundreds of years as Eris gets closer to the sun. ERIS

EXOPLANETS - planets that orbit another star FIVE WAYS TO FIND A PLANET WATCHING FOR WOBBLE - orbiting planets cause stars to wobble in space, changing the color of the light astronomers observe 646 planets discovered SEARCHING FOR SHADOWS - when a planet passes directly between its star and an observer, it dims the star's light by a measureable amount 2734 planets discovered TAKING PICTURES - astronomers can take pictures of exoplanets by removing the overwhelming glare of the stars they orbit44 planets discovered LIGHT IN A GRAVITY LENS - light from a distant star is bent and focused by gravity as a planet passes between the star and earth 47 planets discovered MINISCULE MOVEMENTS - the orbit of a planet can cause a star to wobble around in space in relation to nearby stars in the sky1 planet discovered

HABITABLE ZONE On this planet, currently our sole example of a life-bearing world, the need for water is non-negotiable. So astronomers search the cosmos for similar environments. Around almost every “normal” star, including our sun, we can draw a band of potential habitability: the right distance and temperature for liquid water to exist. The key, of course, is a planetary surface where the water could pool. Both stars and planets come in many types and sizes, and the interplay of these factors determines the extent and influence of this “habitable zone.”

ANOTHER EARTH? A giant, hot-burning star’s habitable zone would be found at a much greater distance than that of a smaller, cooler stellar dwarf. And if we stick with the plan—hunting first for what we know— then small, rocky worlds are our best bet for finding evidence of life as we know it (we’ll talk about “life as we don’t know it” in the next section). So the ideal candidate is an Earth-sized, rocky world nestled comfortably within its star’s habitable zone—though scientists’ understanding of what makes up a habitable zone continues to evolve.

HOW DO WE DETERMINE THE COMPOSITION of exoplanets? Light from exoplanets, if passed through a prism, can be spread out into a rainbow of colors called a spectrum. Different colors correspond to different wavelengths of light. Missing colors show up as black lines, indicating specific gases are present, because each gas absorbs light in a specific wavelength (or color).

VATICAN ASTRONOMY On 18 September, Pope Francis appointed Jesuit brother Guy Consolmagno as the new director of the Vatican Observatory, which employs a dozen astronomers to study asteroids, meteorites, extrasolar planets, stellar evolution, and cosmology. Consolmagno, 63, grew up in the Detroit, Michigan, area and has a Ph.D. in planetary science. He carried out postdoctoral research and taught astronomy before becoming a Jesuit in 1989.

WHAT ARE YOUR THOUGHTS? http://www.sciencemag.org/news/2015/09/talking-science- and-god-popes-new-chief-astronomer Read the interview. Write one page (two pages double-spaced) – briefly summarize the article and tell me your thoughts about what we’ve learned in astronomy. GRAMMAR AND PUNCTUATION COUNT