If you have an eVscope and you want to participate to a scientific campaign on Presidents’ Day, this is something that may interest you. The asteroid 1356 Nyanza will occult a V-12.2 star for up to 6 seconds on February 17 at ~8pm PST and 11pm EST. Yes! This occultation will be visible across the US, from Redding, CA to Philadelphia, PA and Chicago, IL. If a large number of eVscope users observe this event, we will be able to derive the size, shape and eventual existence of moons around the asteroid. So don’t wait and take your eVscope out if you are located nearby the visibility path of the event!
Astronomers are very interested in the shape and the size of asteroids because this helps them understand how they formed. For instance, a few days ago, a group of astronomers revealed the first pictures of the asteroid Pallas, which is heavily cratered, suggesting that the 170-mile golf ball asteroid had a violent history.
Unfortunately, most main-belt objects are too small to be imaged directly using a telescope, even a 8m-class one in an ideal location like Chile or Hawaii. However, astronomers have discovered a trick that helps them measure the size of asteroids—one that relies on the fact that asteroids move with respect to stars and sometimes even occult a star. Because the orbits of several asteroids are well known, it’s possible to predict where and when such occultations can be seen—that is, where a shadow equal in size to the asteroid will move across the Earth (see the diagram below from IOTA). Observers located inside the shadow will see an event (or a drop in the brightness of the star).
We have already used our eVscope to observe several occultations (e.g. Andromache, Pluto, Orus). The most recent one was done in California in collaboration with the NASA Lucy team and will help them to derive the size and shape of Leucus, a Trojan asteroid which is also a target of the mission.
We propose to observe an occultation by a dark asteroid named (1356) Nyanza, a relatively unknown main-belt asteroid discovered in 1935 by a South-African astronomer named Cyril Jackson. Using the Occult program, we found out that the asteroid will occult a 12.2-mag star located in the Cancer constellation and that this event will visible in a small 40km-wide path crossing the USA.
Josselin Desmars, astronomer at the Observatoire de Paris Meudon, ran his own calculations and confirmed the event and its location. The kmz file and the embedded version shown below gives the location of the event based on the most recent estimate of the asteroid’s orbit. Observers located on the red line will be able to detect a long duration occultation (up to 6 seconds). The further the observer is located from the red central line, the shorter the occultation will be. However, the asteroid’s orbit is not well known and is very likely that the occultation could happen anywhere between the grey lines.
[Embedded map to be included soon]
Consequently, if you live nearby this area and the weather is nice on the evening of February 17, take your eVscope out and join us!
Here are the predicted times of the event for several locations along the path of the occultation:
This is a time critical event, so if you have time, I recommend you practice the day before. It will allow you to be sure that you know how to quickly set up, align, focus the eVscope, but also enter the coordinates in the menu (this can be tricky). Again, time accuracy is critical for these types of observations, so make sure you know how to use the time.is website and that you have found the right spot for your observation.
Keep in mind that this is a pilot program. We will improve the app so most of the operations described above can be done automatically. There is an average of 5-10 occultations per month and per location (in an 100 km radius area), so we will probably organize more of these events in the future!