Featured Research

from universities, journals, and other organizations

Venus transit and lunar mirror could help astronomers find worlds around other stars

Date:
December 13, 2012
Source:
Royal Astronomical Society (RAS)
Summary:
On June 6, 2012, Venus passed directly between Earth and the sun, in a so-called transit where the planet appears as a silhouette against the solar disk, something that will not happen again until Dec. 5, 2117. A team of Italian astronomers used the opportunity to perform an unusual and challenging experiment, looking at the sunlight reflected off the moon ('moonlight') to see how it changed during the transit. This technique could help scientists to find planets in orbit around other stars.

The Transit of Venus of 6 June 2012 as seen from Fovant in Wiltshire, United Kingdom.
Credit: Grant Privett

On June 6, 2012, Venus passed directly between Earth and the Sun, in a so-called transit where the planet appears as a silhouette against the solar disk, something that will not happen again until Dec. 5, 2117. A team of Italian astronomers led by Paolo Molaro of the Instituto Nazionale di Astrofisica at the University of Trieste used the opportunity to perform an unusual and challenging experiment, looking at the sunlight reflected off the Moon ('moonlight') to see how it changed during the transit. This technique could help scientists to find planets in orbit around other stars.

The team publish their results in the journal Monthly Notices of the Royal Astronomical Society: Letters published by Oxford University Press.

When Venus passes in front of the Sun it hides a part of our star's rotating surface. Because of rotation, the spectrum of the Sun (created splitting the different colours of light using a spectrograph) is slightly different on each side. On one side, the solar surface is rotating towards the observer and so its light will be 'blueshifted', meaning the lines seen in a spectrum move towards shorter wavelengths. On the other, the surface is rotating away from the observer, so its light is 'redshifted', meaning that the lines move towards longer wavelengths.

By looking at the reflected light from the lunar surface, this is averaged out as a broadening of the various lines. When Venus moves in front of the Sun from east to west, it first blocks out the surface moving towards us and then the surface moving away from us. This causes a distortion in the spectral lines known as the "Rossiter-McLaughlin effect."

The astronomers realised that the High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph installed on a 3.6m telescope at La Silla in Chile, part of the European Southern Observatory (ESO), would be sensitive enough to detect the effect and that the Moon would be in the right place too. The Moon was slightly ahead of Earth in its orbit, so 'saw' the transit a couple of hours later than terrestrial observers. This also meant that the Moon was in the night time sky in Chile, making it possible for the La Silla telescope to operate safely and observe the change in the solar spectrum.

Distortions in the spectral lines resulting from the Rossiter-McLaughlin effect are extremely small and are equivalent to a 3km / hour shift in the observed motion of the Sun. It has been seen before, in binary systems where the two stars eclipse each other. But it becomes more and more difficult to observe when the celestial body is a planet and rather than being the size of Jupiter is similar in size to Earth, as Venus is. Scientists should nonetheless be able to measure the extent of this weak effect on the light from other planetary systems using telescopes such as the European Extremely Large Telescope (E-ELT) now under development. With the technique it should be possible to characterise important features of these systems and thus improve our understanding of the formation of planets in general.

Team member Lorenzo Monaco from ESO describes how important HARPS was in their work. "The measured magnitude of the Rossiter-McLaughlin effect is comparable to being able to track the speed of a person walking at a slow pace at a distance of 150 million kilometres, the space that separates us from the Sun. Nowadays there are very few instruments capable of recording such tiny changes, especially if you only have a few hours to measure them."

"There is close agreement between our work and the theoretical models," says Mauro Barbieri, from University of Padua, who is also a member of the team. "Among other things, this change in velocity is comparable with that due to the natural expansion and contraction of our star. Our observations however have allowed us to clearly see the Rossiter-McLaughlin effect during the transit."

"This measurement," says Paolo Molaro "shows the sensational results that spectrographs on telescopes like E-ELT will be able to deliver. We will open a new horizon in the study of the other Earth-like planets that are almost certainly waiting to be found around other stars in our galaxy."


Story Source:

The above story is based on materials provided by Royal Astronomical Society (RAS). Note: Materials may be edited for content and length.


Journal Reference:

  1. P. Molaro, L. Monaco, M. Barbieri, S. Zaggia. Detection of the Rossiter-McLaughlin effect in the 2012 June 6 Venus transit. Monthly Notices of the Royal Astronomical Society: Letters, 2012; DOI: 10.1093/mnrasl/sls027

Cite This Page:

Royal Astronomical Society (RAS). "Venus transit and lunar mirror could help astronomers find worlds around other stars." ScienceDaily. ScienceDaily, 13 December 2012. <www.sciencedaily.com/releases/2012/12/121213111734.htm>.
Royal Astronomical Society (RAS). (2012, December 13). Venus transit and lunar mirror could help astronomers find worlds around other stars. ScienceDaily. Retrieved April 24, 2014 from www.sciencedaily.com/releases/2012/12/121213111734.htm
Royal Astronomical Society (RAS). "Venus transit and lunar mirror could help astronomers find worlds around other stars." ScienceDaily. www.sciencedaily.com/releases/2012/12/121213111734.htm (accessed April 24, 2014).

Share This



More Space & Time News

Thursday, April 24, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Nuclear-Level Asteroids Might Be More Common Than We Realize

Nuclear-Level Asteroids Might Be More Common Than We Realize

Newsy (Apr. 23, 2014) The B612 Foundation says asteroids strike Earth much more often than previously thought, and are hoping to build an early warning system. Video provided by Newsy
Powered by NewsLook.com
NASA Chief Outlines Plan for Human Mission to Mars

NASA Chief Outlines Plan for Human Mission to Mars

AFP (Apr. 22, 2014) NASA administrator Charles Bolden, speaking at the 'Human to Mars Summit' in Washington, says that learning more about the Red Planet can help answer the 'fundamental question' of 'life beyond Earth'. Duration: 00:48 Video provided by AFP
Powered by NewsLook.com
Nasa Gives You An Excuse to Post a Selfie on Earth Day

Nasa Gives You An Excuse to Post a Selfie on Earth Day

TheStreet (Apr. 22, 2014) NASA is inviting all social media users to take a selfie of themselves alongside nature and to post it to Twitter, Facebook, Flickr, Instagram, or Google Plus with the hashtag #globalselfie. NASA's goal is to crowd-source a collection of snapshots of the earth, ground-up, that will be used to create one "unique mosaic of the Blue Marble." This image will be available to all in May. Since this is probably one of the few times posting a selfie to Twitter won't be embarrassing, we suggest you give it a go for a good cause. Video provided by TheStreet
Powered by NewsLook.com
SpaceX's Dragon Spacecraft Captured by International Space Station

SpaceX's Dragon Spacecraft Captured by International Space Station

Reuters - US Online Video (Apr. 20, 2014) SpaceX's unmanned Dragon spacecraft makes a scheduled Easter Sunday rendezvous with the International Space Station. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins