RF Cascade Workbook for Excel
RF & Electronics Symbols for Visio
RF & Electronics Symbols for Office
RF & Electronics Stencils for Visio
RF Workbench
T-Shirts, Mugs, Cups, Ball Caps, Mouse Pads
Espresso Engineering Workbook™
Smith Chart™ for Excel
|
 |
Hubble to Use Moon as Mirror to See Venus Transit |
This story was retrieved from the NASA website. Neither NASA nor any other entity
represented in the article endorses this website.
Hubble to Use Moon as Mirror to See Venus
Transit
05.04.12
 This mottled landscape
showing the impact crater Tycho is among the most violent-looking places on our Moon. Credit: NASA/ESA/D.
Ehrenreich < full-size
image>
This mottled landscape showing the impact crater Tycho is among the most violent-looking places on our moon.
Astronomers didn't aim NASA's Hubble Space Telescope to study Tycho, however. The image was taken in preparation
to observe the transit of Venus across the sun's face on June 5-6.
Hubble cannot look at the sun directly,
so astronomers are planning to point the telescope at the Earth's moon, using it as a mirror to capture reflected
sunlight and isolate the small fraction of the light that passes through Venus's atmosphere. Imprinted on that
small amount of light are the fingerprints of the planet’s atmospheric makeup.
These observations will
mimic a technique that is already being used to sample the atmospheres of giant planets outside our solar system
passing in front of their stars. In the case of the Venus transit observations, astronomers already know the
chemical makeup of Venus's atmosphere, and that it does not show signs of life on the planet. But the Venus
transit will be used to test whether this technique will have a chance of detecting the very faint fingerprints of
an Earth-like planet, even one that might be habitable for life, outside our solar system that similarly transits
its own star. , Venus is an excellent proxy because it is similar in size and mass to our planet.
The
astronomers will use an arsenal of Hubble instruments, the Advanced Camera for Surveys, Wide Field Camera 3, and
Space Telescope Imaging Spectrograph, to view the transit in a range of wavelengths, from ultraviolet to
near-infrared light. During the transit, Hubble will snap images and perform spectroscopy, dividing the sunlight
into its constituent colors, which could yield information about the makeup of Venus's atmosphere.
Hubble will observe the moon for seven hours, before, during, and after the transit so the astronomers can
compare the data. Astronomers need the long observation because they are looking for extremely faint spectral
signatures. Only 1/100,000th of the sunlight will filter through Venus's atmosphere and be reflected off the moon.
This image, taken with Hubble's Advanced Camera for Surveys, reveals lunar features as small as roughly 560 feet
(170 meters) across. The large "bulls-eye" near the top of the picture is the impact crater, caused by an asteroid
strike about 100 million years ago. The bright trails radiating from the crater were formed by material ejected
from the impact area during the asteroid collision. Tycho is about 50 miles (80 kilometers) wide and is circled by
a rim of material rising almost 3 miles (5 kilometers) above the crater floor. The image measures 430 miles (700
kilometers) across, which is slightly larger than New Mexico.
Because the astronomers only have one shot at
observing the transit, they had to carefully plan how the study would be carried out. Part of their planning
included the test observations of the moon, made on Jan. 11, 2012, as shown in the release image.
Hubble
will need to be locked onto the same location on the moon for more than seven hours, the transit's duration. For
roughly 40 minutes of each 96-minute orbit of Hubble around the Earth, the Earth occults Hubble's view of the
moon. So, during the test observations, the astronomers wanted to make sure they could point Hubble to precisely
the same target area.
This is the last time this century sky watchers can view Venus passing in front of
the sun. The next transit won't happen until 2117. Venus transits occur in pairs, separated by eight years. The
last event was witnessed in 2004.
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. The Space Telescope Science Institute (STScI) in Baltimore, Md., conducts Hubble science operations.
STScI is operated by the Association of Universities for Research in Astronomy, Inc., in Washington, D.C.
For images and more information about Hubble’s view of the Moon and the Venus transit, visit: https://hubblesite.org/news/2012/22 For more information about the Hubble Space Telescope, visit: https://www.nasa.gov/hubble
Cheryl Gundy, STScI
|
|
|
|
 |
