ESA missions gear up for transit of Venus

June 4, 2012
The path that Venus will take as it approaches the Sun in SOHO’s field of view. The image is from the transit of Venus in 2004, but a similar path will be taken during the transit of 2012. Credits: SOHO/ESA/NASA

(Phys.org) -- ESA’s Venus Express and Proba-2 space missions, along with the international SOHO, Hinode, and Hubble spacecraft, are preparing to monitor Venus and the Sun during the transit of Earth’s sister planet during 5-6 June.

ESA’s Express is the only spacecraft orbiting Venus at the moment and while the transit is being watched from Earth, it too will use light from the to study the planet’s atmosphere.

As sunlight filters through the atmosphere it reveals the concentration of different gas molecules at different altitudes.

This technique is also used to probe the atmospheres of planets outside our Solar System – exoplanets – to determine their potential habitability.

Simultaneous measurements are planned during the transit from ground-based observatories around the world to compare with the Venus Express results.  

Exoplanet scientists can then test their techniques for looking at the characteristics of rocky Earth-sized planets.

This video is not supported by your browser at this time.
This is an animation of Venus Express performing stellar occultation at Venus. Venus Express is the first mission ever to apply the technique of stellar occultation at Venus. The technique consists of looking at a star through the atmospheric limb. By analysing the way the starlight is absorbed by the atmosphere, one can deduce the characteristics of the atmosphere itself. Credits: ESA (Animation by AOES Medialab)

Because Venus Express is in orbit around the planet, it will not notice any difference while the transit is being observed from Earth. But the spacecraft will be watching the Sun setting through the atmosphere of Venus, and its data will be compared to measurements made at the Earth at the same time.

These will include data from ESA’s Proba-2 microsatellite and Japan’s Hinode solar satellite, which will have ringside seats in low-Earth orbit to watch as Venus passes in front of the Sun.

“Proba-2 is expected to see a dip in the solar brightness as soon as the thick atmosphere of Venus makes first contact with the solar disc, which is an important measurement for exoplanet scientists,” says Joe Zender, ESA’s Proba-2 mission manager.

There is also the possibility that if Venus passes exactly in front of an active region on the Sun we can obtain information about the energy emitted by that region.

“This is important for space weather studies that help us to understand the Sun and its influence on Earth.”

Hinode will be watching the transit in visible, X-ray, and ultraviolet wavelengths to study phenomena such as the ’black drop effect’ – the small black teardrop shape that appears to connect Venus to the limb of the Sun just after it has fully entered the solar disc and again later, when it begins to leave the disc.

It will also observe the aureole, an arc of light seen around the planet’s disc during the first and last minutes of the transit.

“The most spectacular images and movies should come from Hinode’s Solar Optical Telescope, which has by far the highest resolution of any solar instrument in space,” says Bernhard Fleck, ESA’s Hinode and SOHO project scientist.

“Unfortunately, SOHO will not be well placed to observe the transit. However, it has one thing that no other spacecraft can provide: views of Venus as it approaches the Sun days before the actual transit, and then moves away from the Sun for several days after the .”

Meanwhile, NASA/ESA’s Hubble Space Telescope will use the Moon as a giant mirror to capture diffuse, reflected sunlight: a small fraction of that light will have passed through the atmosphere of Venus en-route to the Moon.

This will test techniques aimed at measuring the atmospheres of Earth-sized rocky exoplanets that could potentially reveal traces of life on planets outside our Solar System.

Explore further: Counting down to the Transit of Venus - our nearest exoplanet test-lab

Related Stories

Venus to appear in once-in-a-lifetime event

May 1, 2012

On 5 and 6 June this year, millions of people around the world will be able to see Venus pass across the face of the Sun in what will be a once-in-a-lifetime experience.

Get ready for the transit of Venus

May 25, 2012

Scientists and amateur astronomers around the world are preparing to observe the rare occurrence of Venus crossing the face of the Sun on 5-6 June, an event that will not be seen again for over a hundred years.

ND expert: The science behind the transit of Venus

May 30, 2012

University of Notre Dame professor of physics Peter Garnavich has research interests that cover a wide range of topics in observational astrophysics. In preparation for the Tuesday (June 5) Transit of Venus, he offers an ...

Solar Dynamics Observatory to observe Venus transit

June 1, 2012

On June 5, 2012 at 6:03 PM EDT, the planet Venus will do something it has done only seven times since the invention of the telescope: cross in front of the sun. This transit is among the rarest of planetary alignments and ...

Recommended for you

Image: Hubble sees a dying star's final moments

July 31, 2015

A dying star's final moments are captured in this image from the NASA/ESA Hubble Space Telescope. The death throes of this star may only last mere moments on a cosmological timescale, but this star's demise is still quite ...

Binary star system precisely timed with pulsar's gamma-rays

July 31, 2015

Pulsars are rapidly rotating compact remnants born in the explosions of massive stars. They can be observed through their lighthouse-like beams of radio waves and gamma-rays. Scientists at the Max Planck Institute for Gravitational ...

Earth flyby of 'space peanut' captured in new video

July 31, 2015

NASA scientists have used two giant, Earth-based radio telescopes to bounce radar signals off a passing asteroid and produce images of the peanut-shaped body as it approached close to Earth this past weekend.

Exoplanets 20/20: Looking back to the future

July 31, 2015

Geoff Marcy remembers the hair standing up on the back of his neck. Paul Butler remembers being dead tired. The two men had just made history: the first confirmation of a planet orbiting another star.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.