As written by the students: Observing Asteroids

Article by: Daragh Logue, Peter McCormick, Ciaran McCaffrey
Assisted By: Maria Buckland, Sarah Bell, Adam McAfee

The Observatory and Planetarium has welcomed school students to visit for work experience. A previous Astronotes article described our work with the Faulkes Telescope Project. Below is an account written by three of our work experience students in 2018 March, based on the work done at Armagh Observatory and Planetarium by them and three other students.

We observed asteroid 2017 VR12. This is a 100-160m wide asteroid which rotates once every 1.4 hours. Under certain conditions it is seen (based on its shape) to look like a cat. It is of great interest to astronomers as it crosses earth’s orbit making it a very near earth asteroid – its closest approach was four times the distance to the moon on the 7th of March 2018. It is believed to originate from one of the largest bodies in the asteroid belt, Vesta. Our results, in which we measured the change in position with time, were submitted to the Minor Planet Centre which is administrated by the International Astronomical Union.

Above is an image of the near-Earth asteroid 2017 VR12. The nature of its appearance is due to its speed of movement across the sky. Although the exposure time was only 30 seconds, the very fast moving asteroid travelled around 25 arcseconds across the sky. At the time of observation, the asteroid was around 4 times the distance from the Earth as the moon is. Image obtained using 0.4-m telescope at Haleakala in Hawaii and operated by Las Cumbres Observatory.

We also observed asteroid 1981 Midas. This is a large asteroid, believed to be about 2km across. It was discovered by American astronomer Charles Kowal in 1973, and is classed as a potentially hazardous asteroid. Although it is predicted that Midas can approach 1.5 times the distance to the Moon, it does not pose a threat to earth in the near future.

Using the European Space Agency’s GAIA satellite which alerted us to its presence, we observed Gaia18amc. According to the Gaia alerts page, 18amc is a candidate supernova. It was cross referenced with an older sky survey image and was found to have appeared recently. We estimated its brightness using the magnitude of nearby known stars and using astronomical software to determine its brightness by comparing its brightness with other stars. We estimated Gaia18amc had a magnitude of 18.5.

The image shows the before image on the right without the new source present, and the after image on the left in which a new source has clearly appeared. Left image obtained using 0.4-m telescope at Haleakala, operated by Las Cumbres Observatory. Right from Digitized Sky Survey.

Another transient Gaia object which we observed was Gaia18amd. We received the alert again from the GAIA satellite. Using the same software we pinpointed the location of the object and compared this image to a previous sky survey. It was not present in the older sky survey, proving that this was a transient object. We again calculated its brightness using the same method as we used in Gaia18amc. This information has led us to conclude that this is likely to be a new supernova.
Another object we observed was ASASSN-18dw which was announced as going into a 4 magnitude outburst in a The Astronomer’s Telegram. It also matched the position of an already known reddish source near the star forming region of Orion. We used a table of star locations and magnitudes to figure out the real brightnesses of nearby objects. Using the same software, we repeated the method that we used earlier to find the actual brightness of ASASSN-18dw to be 14.68 magnitude. We then found a previous image and found its magnitude to have been roughly 19. This confirms our findings and the reports as published by The Astronomer’s Telegram.

In the highlighted area ASASSN-18dw is clearly visible and shows up as being quite bright. This is in stark contrast with previous images of the transient which showed it as being very small and faint. Image obtained using 0.4-m telescope at Cerro Tololo, operated by Las Cumbres Observatory.

The final asteroid we observed was 2011 XO3. It is about 1.2km – 2.7km in diameter. This asteroid does not pose a danger to earth, as the closest it has approached in recent years was 40 million kilometres on the 8th of February 2018, passing at a velocity of 68,000km/h.
We would like to thank The Faulkes Telescope Project and the Las Cumbres Observatory for allowing us to use their telescopes to gain these valuable images. Without them, the data collection that we were able to perform would not have been possible.