Australian skies don't let you down

 tl;dr - Last week, three members of our school's astronomy group observed the exoplanet TIC 46432937 b using a remote telescope in Southern Australia. The light curve turned out exquisit and was promptly  submitted to the TRESCA database. Our successful observation constitutes a valuable contribution to the understanding of extrasolar planets.

Clear autunm skies are usually the best for astronomy. Looking up into the vast blue, you could easily feel drowning. However, not this year. Up to now the first three weeks of September were quite wet, again with an indisputable drowning risk. Luckily, as a local folk song states, the world is "groß und weit", and so the two freshly recruited members of the astronomy group, Magdalena and Miriam, didn't have to wait too long for their first mission. They teamed up with senior astronomer Alex and used a remote telescope in Australia to successfully prey their first exoplanet. 

The target, TIC 46432937 b, was only recently discovered by the TESS satellite. With its four wide-field cameras, TESS ploughs through the night sky, constantly looking for the signal of an exoplanet transit - a tiny yet periodic dip in brightness, the telltale sign of a distant world going round its star. 

TIC 46432937 b, the name does certainly not sound melodious. Exoplanet names are at best an acquired taste. Nevertheless, behind this acronym stands a quite compelling representative of its kind. With a mass that is over three times bigger than Jupiter's, it is able to dim the light of its host star by 56 mmag, almost 5%. The star, on the other hand, is a dwarf, a so called red dwarf to be precise. A star of spectral type M with a small radius (about half that of the Sun) and a relatively cool surface of about 3,400 °C. 

Small star + large planet = deep brightness dips. And that's what we saw.

The light curve of the exoplanet TIC 46432937 b.
The lower curve has the linear trend removed.

The exoplanet host star TIC 46432937 in
the Southern constellation Lepus (The Hare).

The three astronomers during their remote observation run.
From left to right: Alex, Magdalena and Miriam.

We found the shape of the light curve particularly interesting. Although we have a large planet and a small star, a central passage would produce a trough-shaped dip. After an initial decline, the brightness should remain steady while the planet passes the disk. The fact that the light curve doesn't exhibit such a plateau hints to a grazing transit. The model fit from the Exoplanet transit database confirms this. 

The geometry of the transit as expected (left) and measured (right).

To date, there are more than 5,000 known exoplanets in the sky and over 4,000 of them exhibit transits in front of their host stars. And the number keeps growing rapidly, so there's plenty of work to do for us out there. Ironically, as I write these words, it's pouring outside. Well, better go see the forecast for Australia then ... 🦘✨.

Christof Wiedemair

Here's our entry into the TRESCA database: LINK

Want to know more about our exoplanet? Here's the link to the discovery paper: LINK