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Featured Occultation Events For July 2022:

Occultation by Saturn’s Moon Titan

The largest moon of Saturn, known as Titan, will be occulting an 8th magnitude star in the early morning hours of July 9th. The event is visible from the United States, the Caribbean, Mexico, Central America, and northern regions of South America.

Titan is a fascinating object that is somewhat reminiscent of Earth; it hosts standing liquid on its surface and a thick nitrogen dominated atmosphere. However, the liquid on Titan’s surface is not water, it is composed of hydrocarbons like methane and ethane. And the thick atmosphere on Titan does not have oxygen, but instead more methane. NASA’s Cassini spacecraft spent many years exploring Titan before it ended its mission by flying into Saturn in 2017. Now, we have the chance to improve upon our current location of Titan’s position by catching it in occultation.

 

Catch the Central Flash!

Any eVscope Observers within approximately 100 km of the predicted central line will have a chance at seeing a rare atmospheric phenomenon called a “central flash.” This is a spike in brightness that occurs during the occultation as the light from the star is focused toward the observer by the atmosphere of Titan. Light traveling in an atmosphere follows a curved path due to atmospheric refraction. On Earth, this is why the Sun appears squished when it is close to the horizon and is the cause of the illusive green flash. For observers near the center of the occultation of Titan, its atmosphere will act like a lens and bend the star light back into their line of sight. This phenomenon can help us learn about the structure and temperature of Titan’s atmosphere, so it is an extremely valuable observation to make.

The central flash was caught on video by Hans Bode during the 1989 Titan occultation. You watch this video at the following link for an idea of what to expect on July 9: Central Flash Video.

If you are interested in learning more, follow this link to a scientific article titled “The Structure of Titan’s Stratosphere from the 28 Sgr Occultation” written by Sicardy et al. in 1999 following a previous Titan stellar occultation.

If you are able to position yourself within ~200 km of the center line of the occultation, you stand a chance to see this flash!

The wide occultation path of Titan across much of the western hemisphere. Image created with Google Earth Pro.
Light curve of the 1989 occultation of Titan observed from Hanover, Germany. The sharp peak in the middle of the light occultation is the central flash. Credit: Hubbard, Sicardy, Bode, et al. (1993) Astronomy & Astrophysics, 269, 541.

Lucy Occultations in Oceania

For June and July, we are launching an occultation campaign to observe the Jupiter Trojan asteroid Patroclus and its binary companion Menoetius. This asteroid system is a top priority target of NASA’s Lucy mission, which will be visiting the asteroid system as the grand finale of its primary mission in 2033.

Patroclus and Menoetius exist within a swarm of other Trojan asteroids in the L5 Lagrange point within Jupiter’s orbit. A Lagrange point is a region of gravitation stability created by the presence of Jupiter and the Sun. It is thought that Patroclus and Menoetius are relics of the early Solar System. They are classified as “P-Type” asteroids, which are fairly dark (i.e. low albedo) and likely contain organics and volatile elements. By studying them in more detail, we hope to “travel back” to the early days of the Solar System and understand how the planets formed.

Patroclus & Menoetius paths across Australia and Oceania in June and July. Credit: NASA/Lucy Mission.

The Unistellar Network can support the NASA Lucy Mission!

There are 5 occultation opportunities for Patroclus and Menoetius in June and July, all of which are visible from Oceania. In each case, the timing of the observations for either asteroid is identical but their paths are different. You can locate the details in the calendar for Oceania occultations and see screenshots of the paths in the images to the right. Here are the launch dates and times:

  • July 1, 03:45 AWST. Duration = 5 minutes
  • July 6, 20:00 AWST. Duration = 8 minutes
  • July 23, 00:00 AWST. Duration = 6 minutes
  • July 26, 02:59 AWST. Duration = 4 minutes
  • July 29, 00:12 AWST. Duration = 6 minutes

The more positive (and negative) detections we can make over the course of this campaign, the more we can refine the position and velocity of the asteroid system. We can also contribute our positive chords to Lucy team scientists to refine these asteroids’ shapes.

Clear skies!

Predictions listed here are selected by our scientific team based on the number of Unistellar eVscopes available in the area and the scientific interest of the asteroids. We generate our own prediction using the Occult sofware, as well as using predictions made by IOTA (Steve Preston), IBEROC (Carlos Perelló), Lucky Stars of the Observatoire de Paris (Josselin  Desmars) and the Lucy team (Marc Buie).