X
  • This is a ground-based telescope's view of the Large Magellanic Cloud, a satellite galaxy of our Milky Way. The inset image, taken by the Hubble Space Telescope, reveals one of many star clusters scattered throughout the dwarf galaxy.

The cluster members include a special class of pulsating star called a Cepheid variable, which brightens and dims at a predictable rate that corresponds to its intrinsic brightness. Once astronomers determine that value, they can measure the light from these stars to calculate an accurate distance to the galaxy. When the new Hubble observations are correlated with an independent distance measurement technique to the Large Magellanic Cloud (using straightforward trigonometry), the researchers were able to strengthen the foundation of the so-called 
    NASA, ESA, A. Riess (STScI/JHU), and Palomar Digital Sky Survey
    This is a ground-based telescope's view of the Large Magellanic Cloud, a satellite galaxy of our Milky Way. The inset image, taken by the Hubble Space Telescope, reveals one of many star clusters scattered throughout the dwarf galaxy. The cluster members include a special class of pulsating star called a Cepheid variable, which brightens and dims at a predictable rate that corresponds to its intrinsic brightness. Once astronomers determine that value, they can measure the light from these stars to calculate an accurate distance to the galaxy. When the new Hubble observations are correlated with an independent distance measurement technique to the Large Magellanic Cloud (using straightforward trigonometry), the researchers were able to strengthen the foundation of the so-called "cosmic distance ladder." This "fine-tuning" has significantly improved the accuracy of the rate at which the universe is expanding, called the Hubble constant.
  • This illustration shows the three basic steps astronomers use to calculate how fast the universe expands over time, a value called the Hubble constant.

All the steps involve building a strong
    NASA, ESA, and A. Feild (STScI)
    This illustration shows the three basic steps astronomers use to calculate how fast the universe expands over time, a value called the Hubble constant. All the steps involve building a strong "cosmic distance ladder," by starting with measuring accurate distances to nearby galaxies and then moving to galaxies farther and farther away. This "ladder" is a series of measurements of different kinds of astronomical objects with an intrinsic brightness that researchers can use to calculate distances. Among the most reliable for shorter distances are Cepheid variables, stars that pulsate at predictable rates that indicate their intrinsic brightness. Astronomers recently used the Hubble Space Telescope to observe 70 Cepheid variables in the nearby Large Magellanic Cloud to make the most precise distance measurement to that galaxy. Astronomers compare the measurements of nearby Cepheids to those in galaxies farther away that also include another cosmic yardstick, exploding stars called Type Ia supernovas. These supernovas are much brighter than Cepheid variables. Astronomers use them as "milepost markers" to gauge the distance from Earth to far-flung galaxies. Each of these markers build upon the previous step in the "ladder." By extending the ladder using different kinds of reliable milepost markers, astronomers can reach very large distances in the universe. Astronomers compare these distance values to measurements of an entire galaxy's light, which increasingly reddens with distance, due to the uniform expansion of space. Astronomers can then calculate how fast the cosmos is expanding: the Hubble constant.
  • This is a scale and compass image for the Large Magellanic Cloud.
    NASA, ESA, A. Riess (STScI/JHU), and Palomar Digital Sky Survey
    This is a scale and compass image for the Large Magellanic Cloud.
Chat now!
2.67537