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Venus transit – get a live view from the Arctic

Transit of Venus with an aircraft in the field of view

Observers at the European Space Research and Technology Centre witnessed a spectacular event during the Venus transit of 2004 – an aircraft joined the planet in front of the Sun for a few fractions of a second. Copyright: Detlef Koschny.

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.

The occasion also celebrates the first transit while there is a spacecraft orbiting the planet – the European Space Agency’s (ESA) Venus Express.

ESA will be reporting live from the Arctic island of Spitsbergen, where the Venus Express science team will be discussing the latest scientific results from the mission while enjoying a unique view of the 2012 transit under the ‘midnight Sun’.

A transit of Venus occurs only when Venus passes directly between the Sun and Earth. Since the orbital plane of Venus is not exactly aligned with that of Earth, transits occur very rarely, in pairs eight years apart but separated by more than a century.

The last transit was enjoyed in June 2004 but the next will not be seen until 2117.

The transit of Venus

The transit of Venus across the Sun as recorded by European Space Astronomy Centre observers located in Portugal 8 June 2004. Copyright: ESA.

Venus – key to the Solar System

Venus transits are of great historical significance because they gave astronomers a way to measure the size of the Solar System.

The transits of the 18th century enabled astronomers to calculate the distance to the Sun by timing how long it took for Venus to cross the solar disc from different locations on Earth and then using simple trigonometry.

Also, during the transit of 1761 astronomers noticed a halo of light around the planet’s dark edge, revealing Venus to have an atmosphere.

Thanks to spacecraft that have since visited Venus, including Venus Express, we now know that it hosts an inhospitable dense atmosphere of carbon dioxide and nitrogen with clouds of sulphuric acid.

Testbed for exoplanets

Today transit events are a valuable tool for developing methods for detecting and characterising planets orbiting other stars than the Sun, planets that astronomers refer to as exoplanets.

As a planet passes in front of a star, it temporarily blocks out a tiny portion of the starlight, revealing its presence and providing information about the planet’s size. Europe’s CoRoT space telescope has used this technique to discover over 20 exoplanets.

Transits are also being used to search for exoplanets that may harbour life. If the planet has an atmosphere a small fraction of the light from the star will pass through this atmosphere and reveal its properties, such as the presence of water or methane.

Map showing where the transit of Venus will be visible

World visibility of the transit of Venus on 5-6 June 2012. Spitsbergen is an Arctic island – part of the Svalbard archipelago in Norway – and one of the few places in Europe from which the entire transit is visible. For most of Europe, only the end of the transit event will be visible during sunrise on 6 June. Copyright: Michael Zeiler, eclipse-maps.com

Where to view the transit of Venus

During next month’s transit, astronomers will have the chance to test these techniques and add to the data collected during only six previous Venus transits observed since the invention of the telescope in the early 1600s.

The 2012 transit will be visible in its entirety only from the western Pacific, eastern Asia, eastern Australia and high northern latitudes.

For the US, the transit will begin in the afternoon of 5 June and for much of Europe the Sun will rise on 6 June with the transit almost finished.

If you are observing the event please remember — NEVER look at the Sun with unprotected eyes, through ordinary sunglasses or through a telescope, as this will cause permanent blindness.

Live updates from the Arctic

The Sun does not set at Spitsbergen in June, providing a unique opportunity to observe the entire transit from 22:04 GMT 5 June (00:04 CEST 6 June) to 04:52 GMT (06:52 CEST).

“We’re very excited about watching the transit from such a unique European location while Venus Express is in orbit around the transiting planet,” says Håkan Svedhem, ESA’s Venus Express project scientist.

“During the transit, Venus Express will make important observations of Venus’ atmosphere that will be compared with ground-based telescopes to help exoplanet hunters test their techniques.”

As ESA prepares for this rare event with observations from space and from the ground, we will provide background information about the transit on a dedicated blog at: http://blogs.esa.int/venustransit/

Live updates will be posted from Spitsbergen during 5-6 June as the world tunes in to watch Venus make its journey across the Sun for the last time this century.

Adapted from information issued by ESA.

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Transit of Venus – more online resources

Here’s a collection of web pages with information on the transit of Venus. We’ll add more links as they come to hand.

ABC Science: Your Guide to the Transit of Venus

Astronomical Society of Australia: Transit of Venus factsheet (small PDF download)

Sydney Observatory: How to see the Transit of Venus safely

Perth Observatory: Viewing the Transit of Venus in Perth

Stardome Observatory Planetarium, Auckland: Transit of Venus viewing

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Transit of Venus – viewing in Melbourne

ON WEDNESDAY JUNE 6, Venus will line up directly with the Sun and we’ll see the planet as a small black dot tracking across the bright Sun.

It’s an astronomical curiosity today, but in times past it prompted major scientific expeditions. Men devoted their lives to the transit – some were successful and there were also many tales of despair – as they tried to unlock the true size of the Solar System.

The transit in June will be the last in our lifetimes. No one will witness this event again until 2117, and people in Melbourne are perfectly placed to see it.

Join Dr Tanya Hill for breakfast and witness this once in our lifetime event. See the moment when Venus crosses onto the Sun and discover the stories and history that surround this momentous event.

This special event includes telescope viewing, a presentation highlighting the stories surrounding the transit and a light breakfast.

Please note: This event will go ahead regardless of the weather conditions. In the case of bad weather an alternative program will be offered including the Planetarium show “Guiding Lights”, an extended talk by Dr Tanya Hill, the Planetarium’s astronomer and supplemented by footage from other locations in Australia or off-shore via a live feed.

Tickets are strictly limited, so book early!

More information: Melbourne Planetarium Transit of Venus viewing

Adapted from information issued by Melbourne Planetarium.

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Transit of Venus – Sydney viewing opportunity

THE UNIVERSITY OF WESTERN SYDNEY’S Penrith campus Observatory will be the best place in Sydney to witness one of the rarest astronomical phenomena of our lifetime – the transit of Venus – on June 6, 2012.

The transit of Venus occurs when Earth’s closest neighbour, the planet Venus, passes directly between Earth and the Sun. From Australia, Venus will look like a small, round silhouette, slowly moving across the surface of the Sun.

Director of the UWS Observatory, Associate Professor Miroslav Filipovic, says UWS has the biggest and best telescope within a 200-300km radius.

“The University’s 24inch (62cm) computerised telescope is equipped with special solar … filters, which will allow for a safe and exemplary viewing experience,” says Associate Professor Miroslav Filipovic.

“As part of the transit experience at UWS, guests will have the opportunity to view Venus’ travels through a range of telescopes and hear a short, educational talk.

“The entire event will also be televised in a new 3D movie theatre within the Observatory, and will be live-streamed on the University’s website.”

The transit of Venus occurs in pairs, in cycles of more than 100 years. Captain James Cook sailed to Tahiti to observe a pair of transits in 1761 and 1769, and our direct ancestors may have been fortunate enough to see the transits of 1874 and 1882.

The first transit of our lifetime occurred in 2004. After this year’s transit, Venus will not pass between Earth and the Sun again until December 2117 and 2125.

Members of the community are invited to book-in for a special one-hour viewing of this important celestial event, from 8am on Wednesday 6th June 2012.

Although optimal viewing of the transit is dependent on a clear and cloud-free day, this special event will run regardless of the weather with the assistance of the Western Sydney Amateur Astronomy Group (WSAAG).

WHAT: The UWS transit of Venus Experience

WHEN:  The transit will take place from 8.15am to 2.45pm, Wednesday, 6th June 2012

WHERE: Building AO, UWS Penrith campus, Great Western Highway, Werrington North

MAP: http://uws.edu.au/__data/campus_maps/Werrington_North_Campus_North_L.pdf

COST: $10 per person

WEBSITE: http://www.uws.edu.au/observatory

Bookings are essential. To schedule your viewing of the transit of Venus, please contact the UWS Observatory on: (02) 4736 0135 (Mondays, Wednesdays and Thursdays) or email r.mccourt@uws.edu.au

Adapted from information issued by UWS.

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Transit of Venus – live coverage details

ON WEDNESDAY JUNE 6, the people of Earth will be able to witness a ‘transit of Venus,’ when the planet Venus can be seen moving across the face of the Sun.

“Since the phenomena was first recognised and observed by Jeremiah Horrocks, an English astronomer and clergyman in 1639, there have only been five transits of Venus – 1761, 1769, 1874, 1882 and 2004,” says Dr Paul Willis, Director of the Royal Institution of Australia.

“By observing a transit, astronomers could, for the first time, calculate the distance from the Earth to the Sun with some accuracy,” he adds. “This had astounding implications for science’s understanding of the universe.

Livestreaming of the transit will be shown on RiAus website on 6 June 2012, from 7:30am – 3pm

“This is the last time people will get the chance to see this until 2117 – and for most of us the chances of being here then are pretty slim,” says Dr Nick Lomb, Curator of Astronomy, Powerhouse Museum. “It’s an experience not to be missed.”

“What many people don’t realise is that Australia has a very real connection to this rare astronomical event,” says Valerie Sitters, Collections Specialist, the State Library of South Australia.

“Lieutenant James Cook was sent to Tahiti on HMS Endeavour to observe the transit that occurred in 1769,” Sitters adds. “He was then ordered to search for the great south land when he discovered and charted the east coast of Australia.”

RiAus transit of Venus livestreaming site: http://riaus.org.au/events/livestreaming-of-the-transit-of-venus/

Adapted from information issued by RiAus.

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Transit of Venus – NASA’s live coverage

NASA TELEVISION will air a live program starting at 5:30 p.m. US EDT Tuesday, June 5, showcasing the celestial phenomenon of the planet Venus trekking across the face of the Sun. The rare event, known as the Venus transit, will not occur again until 2117.

The transit occurs when Venus passes directly between Earth and the Sun. Viewers will see Venus as a small dot gliding slowly across our nearest star. Historically, viewed by Captain James Cook and other luminaries, this rare alignment is how we measured the size of our Solar System.

There have been 53 transits since 2000 B.C. The last time the event occurred was on June 8, 2004, watched by millions worldwide. This year, observers on six continents and a small portion of Antarctica will be in position to see at least part of it.

NASA TV coverage will include updates from NASA centres across the USA and locations from some of the 148 countries hosting viewing activities. Images taken of the transit from the International Space Station and NASA’s Hubble Space Telescope and Solar Dynamics Observatory also will be aired with scientists sharing their perspectives and the historical significance of the event.

NASA EDGE, a behind-the-scenes, informative webcast, will air the transit live from Mauna Kea, Hawaii. This location offers the best viewing position of the entire transit.

More information about the worldwide events, safety precautions for viewing, educational content and social media activities:

http://venustransit.nasa.gov/

NASA TV streaming video, downlink and scheduling information:

http://www.nasa.gov/ntv

The public can follow the event on Twitter on #venustransit and download a free phone App:

http://venustransit.nasa.gov/2012/multimedia/apps.php

Adapted from information issued by NASA.

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Transit of Venus – viewing in the USA

ON TUESDAY AFTERNOON, June 5th (US time zone), everyone in the United States will have a chance to witness one of the rarest celestial phenomena known: a “transit of Venus”. Such an event occurs when the planet Venus passes almost exactly between the Earth and the Sun, and they are incredibly rare.

Since first predicted by the German mathematician and astronomer Johannes Kepler in the 17th century, only six transits of Venus have been observed. Weather permitting, this will be the seventh.

Transits of Venus occur at regular intervals that repeat over a 243-year period. Intervals between successive transits are 8 years, 105.5 years, 8 years, and 120.5 years. The next transit of Venus won’t occur until December 11, 2117, and it will not be visible from most of the USA.

Early transit of Venus expeditions

Kepler predicted the transit of December 7, 1631, but died before the event occurred. The next transit, on December 4, 1639, was observed by only two individuals, Jeremiah Horrocks and William Crabtree, from England.

In 1677 Edmond Halley (of comet fame) observed a transit of Mercury from St. Helena Island and realised that such events, if observed from many widely-spaced sites, could provide a geometric measure of the scale of the Solar System. His work led to several far-flung expeditions to observe the Venus transits of June 6, 1761 and June 3, 1769. One of the British expeditions to the latter transit was led by Captain James Cook.

Results from these expeditions were mixed, but enough experience was gained to attempt observations of the next series in the 19th century.

The transits of December 9, 1874, and December 6, 1882, were met with an armada of scientific expeditions equipped with state-of-the-art astronomical instruments. The U.S. Congress funded and outfitted eight separate expeditions for each event and placed overall scientific direction of these teams under the command of the U.S. Naval Observatory (USNO). Once again the results were inconclusive, but many of the instruments from these expeditions are still in the Observatory’s possession.

The 20th century saw no transits of Venus; the next one occurred on June 8, 2004. By this time the size of the Solar System had been well established, so observing the transit became more of an historical event than a scientific one.

Transit of Venus viewing for US citizens

This year’s transit will begin about 2.5 hours before sunset in the Washington, D.C., area at 6:04pm US Eastern Daylight Time. It will occur earlier in the day and at a higher altitude as one moves farther west, but no place in the “lower 48” will see the event in its entirety. Residents of Alaska, Hawai’i, and the U.S. Pacific Territories are the only Americans who will see the complete event.

At the USNO, we will once again attempt to observe the transit with one of our historic 5-inch Alvan Clark transit of Venus telescopes. This particular instrument, Number 856, successfully observed the transit of 1874 from Vladivostok, Siberia, and the 1882 transit from San Antonio, Texas.

It was employed to successfully observe the 2004 transit following restoration by the observatory’s instrument shop. If successful this year we will have the only instrument known to have observed four of the seven transits that humans have recorded.

Observing the transit will not require a telescope – the disc of Venus is large enough to be seen with the unaided eye. However, extreme precaution must be taken when observing the event or permanent eye damage and/or blindness will occur. The USNO strongly recommends that people wishing to observe the transit contact any of the local science centres, planetariums, or amateur astronomy clubs as they will have the proper equipment to enjoy this rare event. A listing of such regional organisations may be found on the USNO’s website:

http://www.usno.navy.mil/USNO/about-us/local-observatories-planetaria-and-clubs

Adapted from information issued by USNO.

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Making sense of the solar cycle

THE NUMBER OF SUNSPOTS increases and decreases over time in a regular, approximately 11-year cycle, called the sunspot cycle. The exact length of the cycle can vary. It has been as short as eight years and as long as fourteen, but the number of sunspots always increases over time, and then returns to low again.

Sunspots look dark only because they’re a bit cooler than the surrounding solar surface. In reality, sunspots are still intensely hot—around 3,000 to 4,000 degrees Celsius.

More sunspots mean increased solar activity, when great blooms of radiation known as solar flares or bursts of solar material known as coronal mass ejections (CMEs) shoot off the Sun’s surface.

The highest number of sunspots in any given cycle is designated “solar maximum,” while the lowest number is designated “solar minimum.”

A sunspot group

Sunspot numbers climb and fall over an 11-year cycle.

Each cycle, varies dramatically in intensity, with some solar maxima being so low as to be almost indistinguishable from the preceding minimum.

The last solar maximum was in the year 2000, and the next is expected to occur in early 2013.

Solar cauldron

Sunspots are a magnetic phenomenon. The entire Sun is magnetised with a north and a south magnetic pole just like a bar magnet. The comparison to a simple bar magnet ends there, however, as the Sun’s interior is constantly on the move.

By tracking pressure waves that course through the centre of the Sun, an area of research known as helioseismology, scientists can gain an understanding of what’s deep inside the Sun.

They have found that the magnetic material inside the Sun is constantly stretching, twisting, and crossing as it bubbles up to the surface.

The exact pattern of movements is not conclusively mapped out, but over time they eventually lead to the poles reversing completely.

The Sun flips out

The sunspot cycle happens because the magnetic poles flip—north becomes south and south becomes north—approximately every 11 years. Some 11 years later, the poles reverse again back to where they started, making the full solar cycle actually a 22-year phenomenon.

The Sun behaves similarly over the course of each 11-year cycle no matter which pole is on top, however, so the shorter cycle tends to receive more attention.

Adapted from information issued by NASA / Goddard Space Flight Centre. Images courtesy NSO and SOHO (ESA & NASA).

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Journey to the Sun!

AN AMBITIOUS MISSION to study the Sun is set for launch in 2017. Solar Orbiter will perform a close-up study of our Sun and inner heliosphere—the uncharted innermost regions of our Solar System—to better understand, and even predict, the unruly behaviour of the star on which our lives depend.

At its closest point, the spacecraft will be closer to the Sun than any previous spacecraft, braving the fierce heat and will carry its telescopes to almost one-quarter of Earth’s distance from our nearest star.

The European Space Agency’s Solar Orbiter will be the first satellite to provide close-up views of the Sun’s polar regions, which are very difficult to see from Earth. It will be able to almost match the Sun’s rotation around its axis for several days, and so it will be able for the first time to see solar storms building up over an extended period from the same viewpoint. It will also deliver data of the side of the Sun not visible from Earth.

Following “gravity assist” swing-bys of Venus and the Earth, Solar Orbiter will settle into a 168-day-long orbit around the Sun from which the spacecraft will begin its data collection mission.

Along this orbit, the spacecraft will reach closest approach to the Sun every five months—at around 42 million kilometres.

Adapted from information issued by ESA.

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