Space

April 11, 2014

NASA’s Hubble extends stellar tape measure 10 times farther into space

Using NASA’s Hubble Space Telescope, astronomers now can precisely measure the distance of stars up to 10,000 light-years away – 10 times farther than previously possible.

Astronomers have developed yet another novel way to use the 24-year-old space telescope by employing a technique called spatial scanning, which dramatically improves Hubble’s accuracy for making angular measurements. The technique, when applied to the age-old method for gauging distances called astronomical parallax, extends Hubble’s tape measure 10 times farther into space.

“This new capability is expected to yield new insight into the nature of dark energy, a mysterious component of space that is pushing the universe apart at an ever-faster rate,” said Noble laureate Adam Riess of the Space Telescope Science Institute (STScI) in Baltimore, Md.

Parallax, a trigonometric technique, is the most reliable method for making astronomical distance measurements, and a practice long employed by land surveyors here on Earth. The diameter of Earth’s orbit is the base of a triangle and the star is the apex where the triangle’s sides meet. The lengths of the sides are calculated by accurately measuring the three angles of the resulting triangle.

Astronomical parallax works reliably well for stars within a few hundred light-years of Earth. For example, measurements of the distance to Alpha Centauri, the star system closest to our sun, vary only by one arc second. This variance in distance is equal to the apparent width of a dime seen from two miles away.

Stars farther out have much smaller angles of apparent back-and-forth motion that are extremely difficult to measure. Astronomers have pushed to extend the parallax yardstick ever deeper into our galaxy by measuring smaller angles more accurately.

This new long-range precision was proven when scientists successfully used Hubble to measure the distance of a special class of bright stars called Cepheid variables, approximately 7,500 light-years away in the northern constellation Auriga. The technique worked so well, they are now using Hubble to measure the distances of other far-flung Cepheids.

Such measurements will be used to provide firmer footing for the so-called cosmic “distance ladder.” This ladder’s “bottom rung” is built on measurements to Cepheid variable stars that, because of their known brightness, have been used for more than a century to gauge the size of the observable universe. They are the first step in calibrating far more distant extra-galactic milepost markers such as Type Ia supernovae.

Riess and the Johns Hopkins University in Baltimore, Md., in collaboration with Stefano Casertano of STScI, developed a technique to use Hubble to make measurements as small as five-billionths of a degree.

To make a distance measurement, two exposures of the target Cepheid star were taken six months apart, when Earth was on opposite sides of the sun. A very subtle shift in the star’s position was measured to an accuracy of 1/1,000 the width of a single image pixel in Hubble’s Wide Field Camera 3, which has 16.8 megapixels total. A third exposure was taken after another six months to allow for the team to subtract the effects of the subtle space motion of stars, with additional exposures used to remove other sources of error.

Riess shares the 2011 Nobel Prize in Physics with another team for his leadership in the 1998 discovery the expansion rate of the universe is accelerating – a phenomenon widely attributed to a mysterious, unexplained dark energy filling the universe. This new high-precision distance measurement technique is enabling Riess to gauge just how much the universe is stretching. His goal is to refine estimates of the universe’s expansion rate to the point where dark energy can be better characterized.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center in Greenbelt, Md., manages the telescope. STScI conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.




All of this week's top headlines to your email every Friday.


 
 

 

Headlines September 2, 2014

News: Debris yields clues that pilot never ejected - When investigators were finally able to safely enter the crash site of an F-15C “Eagle” fighter jet on the afternoon of Aug. 27, they made a grim discovery that concluded more than 30 hours of searching – the pilot never managed to eject from the aircraft.  ...
 
 

News Briefs September 2, 2014

Pentagon: Iraq operations cost $560 million so far U.S. military operations in Iraq, including airstrikes and surveillance flights, have cost about $560 million since mid-June, the Pentagon said Aug. 29. Rear Adm. John Kirby, the Pentagon press secretary, said the average daily cost has been $7.5 million. He said it began at a much lower...
 
 

Unmanned aircraft partnership reaches major milestone

A team of research students and staff from Warsaw University of Technology have successfully demonstrated the first phase of flight test and integration of unmanned aircraft platforms with an autonomous mission control system. The demonstration marks a significant milestone in a partnership between the university and Lockheed Martin that began earlier this year. This is...
 

 

Raytheon delivers first Block 2 Rolling Airframe Missiles to US Navy

Raytheon delivered the first Block 2 variant of its Rolling Airframe Missile system to the U.S. Navy as part of the company’s 2012 Low Rate Initial Production contract. RAM Block 2 is a significant performance upgrade featuring enhanced kinematics, an evolved radio frequency receiver, and an improved control system. “As today’s threats continue to evolve,...
 
 
Courtesy photograph

Two Vietnam War Soldiers, one from Civil War to receive Medal of Honor

U.S. Army graphic Retired Command Sgt. Maj. Bennie G. Adkins and former Spc. 4 Donald P. Sloat will receive the Medal of Honor for actions in Vietnam. The White House announced Aug. 26 that Retired Command Sgt. Maj. Bennie G. A...
 
 

Sparks fly as NASA pushes limits of 3-D printing technology

NASA has successfully tested the most complex rocket engine parts ever designed by the agency and printed with additive manufacturing, or 3-D printing, on a test stand at NASA’s Marshall Space Flight Center in Huntsville, Ala. NASA engineers pushed the limits of technology by designing a rocket engine injector – a highly complex part that...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>