Mark your calendars for Tuesday, June 5, people.
The Houston Museum of Natural Science invites the public to observe a rare and special event on the afternoon of Tuesday, June 5. On that date, the planet Venus will transit the Sun, appearing as a black dot against the Sun’s disk. Weather permitting, the Museum will provide telescopes with filters to safely observe the Sun near the sundial just outside the Museum’s main entrance, as well as at the George Observatory and at our museum in Sugar Land.
A photograph taken of the 2004 transit of Venus at 3:39 p.m. Hong Kong time from Tuen Mun, New Territories, Hong Kong.
What’s the big deal?
On June 5, Venus passes the Earth on its faster orbit around the Sun. Venus’s orbit is between ours and the Sun, so it passes between Earth and Sun about once every 584 days. However, since Venus’s orbit is tilted by about five degrees to our own, it usually “misses” the Sun by a wide margin as seen from Earth. But on June 5, Venus lines up almost exactly with the Earth and the Sun. This causes Venus to appear as a black dot silhouetted on the Sun’s disk, an event called a “transit.” Only Mercury and Venus can transit the Sun because they are the only planets that pass between the Earth and Sun.
How often does this happen?
Transits of Venus occur in pairs eight years apart — and then not again for more than a century. Because of the way Venus’s orbit is aligned, transits occur only in June or December. This is the second of this pair of transits (the other, not visible in Houston, occurred in June 2004). The next transit visible here in Houston will occur the morning of December 8, 2125.
So how do I see Venus on the Sun’s disk?
Venus remains in front of the Sun for about six hours. Its disk will be over 30 times smaller than the Sun’s — roughly the size of a sunspot. To view the transit, we will provide solar telescopes and solar projection devices at the Museum, at the George Observatory, and at our Museum in Sugar Land. We will also have special solar glasses (the same kind used to watch eclipses) for purchase at all three locations.
As the transit begins, Venus will appear as a small dot on the right side of the Sun low in the western sky. Unlike any sunspots present, Venus will move quite noticeably across the Sun’s disk. Also, sunspots can be irregular in shape, while the disk of Venus is round. The transit begins in the afternoon at 5:09 p.m. and will still be in progress at sunset at 8:19 p.m.
If the Sun was still up, we would see Venus exit the Sun’s disk at 11:31 pm. Due to the trees surrounding Hermann Park and the deck at George Observatory, we will observe at these sites until 7:00 pm. At Sugar Land, however, the clear horizon means we can observe the Sun until 8:00 p.m.
At all three Museum locations, we will have free planetarium previews of the Venus transit, illustrating why it happens and why it is so rare. We’ll also take a virtual voyage to the planet. These special shows will be offered at 4:00, 4:15, 4:30, and 4:45 p.m. in preparation for the event beginning at 5:09 p.m.
This is the last transit of Venus that anyone alive today will ever be able to see, so don’t miss it!
Do not attempt to observe the Sun with the naked eye or through an unfiltered telescope. Failure to use appropriate filtration may result in permanent eye damage or blindness.