Credit: O/G. Anglada-Escudé
This unusual Picture of the Week showcases the latest data gathered by ESO’s exoplanet hunter, the High Accuracy Radial velocity Planet Searcher (HARPS), during the ongoing Red Dots campaign,
a search for terrestrial planets around our nearest three red dwarf
stars: Proxima Centauri, Barnard’s Star, and Ross 154. The campaign was launched earlier in 2017 to build on the 2016 discovery
of Proxima b around our nearest stellar neighbour, Proxima Centauri.
Red Dots is designed as an open notebook science experiment, meaning the
public has access to the data and can even contribute observations. Can
you see a new exoplanet in these data of Proxima Centauri?
By
carefully tracing the movement of a star over time, graphs like these
can reveal the presence of exoplanets. Just as a star pulls on its
orbiting planets using gravity, planets pull on the star, causing the
star to wobble and shift the wavelength of its light by a small but
measureable amount. By analysing the predictable, repeating changes,
astronomers can infer the presence of a planet. The top left graph
displays the 2016 data that confirmed the existence of Proxima b,
showing how the planet is causing its parent star, Proxima Centauri, to
move towards and away from Earth over time. The curved line represents
the wobbling signal of the star, with the regular pattern of changing
radial velocities (RV) repeating every 11.2 days.
The top right
graph shows new measurements made with HARPS during the Red Dots
campaign. The new data once again confirms Proxima b’s signal (in
yellow), but also includes additional data patterns — visible here as a
downward slope in both the 2016 and 2017 data points — hinting that
there may be more to be discovered. To make a firmer statement on what
is causing these patterns, astronomers need to use quantitative
mathematical tools.
One such mathematical tool is called a periodogram,
which searches for repeating signals in the data — displayed here as
prominent peaks — that indicate the presence of a planet. The graph on
the bottom panel shows the periodogram for the new data. The first
signal (in white) corresponds to Proxima b. The second set of possible
periods (in red), of around 200 days, are produced from patterns seen in
the top panels. The presence of multiple peaks of similar heights means
a signal cannot be precisely pinpointed and that its origin remains
unclear.
The project will continue acquiring measurements until
the end of September this year. You can follow along as the Red Dots
campaign unfolds and even contribute observations via the Red Dots website, Facebook, or Twitter accounts.
Source: ESO/Images/Potw
