Observing Novae from Norway

By Vegard Rekaa

During May and June 2021, two bright Novae appeared in the night sky. The first in Cassiopeia (Nova Cas 2021) and the second in Hercules (Nova Her 2021). A nova appears when a white dwarf in a binary system of stars accumulates sufficient gas from its companion star. As this gas accumulates, the newly added layers are subject to a rapid fusion process and cause a sudden rise in the brightness of the white dwarf that can be visible throughout the galaxy.

These transient events have proven ideal for educational projects, where the students perform the observations and afterwards, find the magnitude of the star by comparing its brightness with known, previously measured stars in the same field of view. Novae also bring some dynamics into astronomy and are evidence that even the Universe changes over time. White dwarfs themselves are interesting objects for the students to study, as it is the future and final state of our own star, the Sun.

Teachers and students in Norway have been involved in measuring the light intensity of these stars during May and June 2021, and will probably follow the development of these stars throughout the summer. Figure 1 shows a series of their observations and their resulting light curve, clearly illustrating the changing brightness of the white dwarf.

Figure 1 – Images and data collected on Nova Her 2021 by students and teachers in Norway

Nova Cas 2021 was discovered by Yuji Nakamura in Japan on March 18th, just as the nova had reached magnitude +9.6. During the following days, the nova increased rapidly to +7.5 and +5.2 (lower numbers mean a greater brightness!), making it visible for naked-eye observations. Its position is RA 23h 24m 47.73s, Dec +61° 11’ 14.8” (J2000.0), which places it in the western parts of the constellation, Cassiopeia.

Nova Her 2021 was discovered on June 12th by Seiji Ueda in Japan. At the time it shone with magnitude +8.4 and after this, rose to +8 and +6.4. This means it is also observable with small telescopes, even in the light summer nights in the northern hemisphere. Its position is RA 18h 57m 31s, Dec +16° 53′ 40″ (J2000.0), which places it in the south-eastern corner of the constellation Hercules.

Only very few novae become bright enough to observe with the naked eye, while having the powerful instruments provided by the Faulkes Telescope Project at hand, teachers and students are now able to join in on the observations of those novae that are dimmer yet far more common.

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