Watch nearly seven hours of transit time in less than twenty seconds! This time lapse movie from ESA TV shows the transit of Venus as experienced under the midnight sun, 78 degrees north from the Arctic island of Svalbard. Interference from cloud gives an eerie feel to the scene.
Tag Archives: Venus
Transiting the midnight sun
Venus Express and the transit of Venus
ESA's Venus Express project scientist Håkan Svedhem observes the transit of Venus from Svalbard as Venus Express – the only spacecraft orbiting Venus at the moment – prepares to take its solar occultation measurements. During these measurements sunlight will filter through Venus' atmosphere, revealing the concentration of different gas molecules at different altitudes. This technique is also used to probe the atmospheres of planets outside of our Solar System – exoplanets – to determine their potential habitability. Simultaneous ground-based measurements will be compared with Venus Express data to test techniques used to characterise rocky Earth-sized planets.
The transit of Venus, from Saturn
Tonight’s transit of Venus may be the last for observers on Earth for the next century, but the Cassini spacecraft will only have to wait a few months.
On 21 December 2012, Saturn, Venus and the Sun will be aligned such that Cassini will be able to see Venus transit the Sun.
The faraway viewpoint in the outer Solar System will present an observing challenge, and Cassini will stare at the transit for a full nine hours to try and detect it.
The data collected will contribute valuable information to exoplanet scientists that are on the hunt for rocky, Earth-sized planets outside of our Solar System.
Venus approaches the Sun
Venus appeared in the field of view of ESA/NASA's SOHO satellite on 1 June, and has been fast approaching ahead of transit on 5-6 June. SOHO's LASCO instrument won't be able to see the transit because its coronagraph blocks out the bright solar disc so that it can study the fine detail of the Sun's atmosphere. Here it provides a unique view of the soon-t0-be transiting planet, which is currently difficult to observe from Earth while it is bathed in the Sun's glare.
Extrasolar worlds and transits
While transits of the 18th and 19th centuries gave astronomers a way to answer one of the biggest astronomical questions of the time – just how big is the Solar System – modern day astronomers use transits to search for planets outside of our Solar System.
As a planet passes in front of a star it temporarily blocks out a tiny portion of the star’s light, giving away its presence. The dip in starlight can be detected by sensitive telescopes such as Europe’s CoRoT and NASA’s Kepler space telescopes, which plot the reduction in light from the star in the form of a ‘light curve’.
There are some caveats, of course – the telescopes have to be looking in the line of sight of the planet as it transits across the face of its star, and to confirm the observation astronomers must wait for the planet to transit in front of the star several times. For example, if someone were watching the Earth transit across the face of the Sun, they would have to wait a year for each transit to occur. That’s why it can sometimes take several years for exoplanet ‘candidates’ to be confirmed.
Sometimes the light curves reveal that more than one planet is present around the star – of the 770+ planets known to date, over one hundred multiple planet systems are known!
As well as simply telling astronomers that a planet is present, the amount by which the brightness of the host star is reduced provides details of the planet’s size.
The transit method also makes it possible to study the atmosphere of the planet, and this is one of the techniques that astronomers will be testing during next week’s transit of Venus. As the planet passes in front of its host star, light from the star filters through the upper atmosphere of the planet. By studying the ‘fingerprints’ that the atmosphere leaves on the star’s light, astronomers can determine the concentration of different molecules in the planet’s atmosphere. Such a technique may enable astronomers to detect signs of life on potentially habitable Earth-sized worlds elsewhere in the Galaxy.