馬秀艷

Astronomers have created the most precise map to date of the Milky Way by tracking thousands of big pulsating stars spreading throughout the galaxy， demonstrating that， as is generally thought， its disk of various stars is not flat but dramatically warped and twisted in shape.

The researchers showed a three-dimensional map of the Milky Way—home to more than 100 billion stars including our sun—providing a comprehensive chart of its structure： a stellar（恒星的） disk including four major spiral（螺旋形的） arms and a bar-shaped core region.

“For the first time， our whole galaxy—from edge to edge of the disk—was mapped using real， precise distances，” said astronomer Andrzej Udalski of University of Warsaw， co-author of the study published in the journal Science.

Until now， the understanding of the galaxy's shape has been based upon indirect measurements of landmarks within the Milky Way and inferences from structures observed in other galaxies populating the universe.

The new map was formulated using precise measurements of the distance from the Sun to 2，400 stars called “Cepheid variables” scattered throughout the galaxy.

“Cepheids are ideal to study the Milky Way for several reasons，” added study co-author Dorota Skowron. “Cepheid variables are bright supergiant stars and they are 100 to 10，000 times brighter than the Sun， so we can detect them on the outskirts of our galaxy. They are relatively young—younger than 400 million years—so we can find them near their birthplaces.”

The astronomers tracked the Cepheids using the Warsaw Telescope located in the Chilean Andes. These stars pulsate at regular intervals and can be seen through the galaxy's large clouds of interstellar dust that can make dimmer stellar bodies hard to spot. The map showed that the galaxy's disk， far from flat， is significantly warped and varies in thickness from place to place， with increasing thickness measured further from the galactic center.

The Milky Way began to form relatively soon after the Big Bang that marked the beginning of the universe some 13.8 billion years ago.

閱讀檢測

1. It is generally believed that the galaxy's disk .

A. has a level surface

B. is shaped like a plate

C. is twisted in shape

D. has many raised dots

2. What makes dimmer stellar bodies hard to find？

A. The shaking of the stars.

B. The brightness of the stars.

C. The Big Bang.

D. Large clouds of interstellar dust.

語言學習

難句分析

These stars pulsate at regular intervals and can be seen through the galaxy's large clouds of interstellar dust that can make dimmer stellar bodies hard to spot. 這些恒星有規(guī)律地發(fā)生脈動，并且可以透過星系中巨大的星際塵埃云看到，這些塵埃云會使較暗的恒星體很難被發(fā)現(xiàn)。

本句是一個復合句。These stars pulsate...and can be seen...dust是主句，其中pulsate和can be seen是并列謂語，that引導的是定語從句。