Exoplanets with Deep Transits

The list above shows the 35 stars presently known to dip in brightness by 0.02 magnitudes or more due to a transiting exoplanet.

The change in the star’s magnitude during transit is given by

\Delta m = 2.5\log_{10}\left ( 1+\delta \right )

where Δm is the drop in magnitude, and δ is the transit depth

The time between transits for these exoplanets ranges between 0.79 and 5.72 days, with a median period of 2.24 days.  You can generate your own ephemeris for any of these transiting exoplanets at:


The transit duration for these exoplanets ranges between 1.08 and 3.11 hours, with a median duration of 2.11 hours.

The exoplanets with the deepest transits, HATS-6 b at 0.035 magnitudes and Kepler-45 b at 0.034 magnitudes, cross stars that are 15.2 and 16.9 magnitude, respectively, so these events might be out of reach for most amateur photometrists.  The only other star hosting a transiting exoplanet with a Δm ≥ 0.03m is Tycho 5165-481-1 in Aquila (WASP-80 b) which at visual magnitude 11.9 is a better candidate for smaller instruments.  The brightest star on our list (by far) is HD 189733 in Vulpecula, magnitude 7.7, with a drop in brightness that is almost as good at 0.026 magnitudes.

Fakhouri, O. (2018). Exoplanet Orbit Database | Exoplanet Data Explorer. [online] Exoplanets.org. Available at: http://exoplanets.org/ [Accessed 11 Dec. 2018].

Faintest Constellations

There are a dozen constellations with no star brighter than +4.0 magnitude.  Many of them are deep in the southern sky.  They are:

ANTLIA, the Air Pump
Brightest Star: Alpha Antliae, apparent visual magnitude +4.25


CAELUM, the Engraving Tool
Brightest Star: Alpha Caeli, apparent visual magnitude +4.45


Brightest Star: Beta Camelopardalis, apparent visual magnitude +4.02

cuh-MEL-oh- PAR-duh-liss

CHAMAELEON, the Chameleon
Brightest Star: Alpha Chamaeleontis, apparent visual magnitude +4.047

cuh-MEAL-yun, or cuh-MEAL-ee-un

COMA BERENICES, Berenice’s Hair
Brightest Star: Beta Comae Berenices, apparent visual magnitude +4.25

COE-muh BER-uh-NICE-eez

CORONA AUSTRALIS, the Southern Crown
Brightest Star: Meridiana, apparent visual magnitude +4.087

cuh-ROE-nuh aw-STRAL-iss

MENSA, the Table Mountain
Brightest Star: Alpha Mensae, apparent visual magnitude +5.09


MICROSCOPIUM, the Microscope
Brightest Star: Gamma Microscopii, apparent visual magnitude +4.654


NORMA, the Carpenter’s Square
Brightest Star: Gamma2 Normae, apparent visual magnitude +4.02


SCULPTOR, the Sculptor
Brightest Star: Alpha Sculptoris, apparent visual magnitude +4.27


SEXTANS, the Sextant
Brightest Star: Alpha Sextantis, apparent visual magnitude +4.49


Brightest Star: Anser, apparent visual magnitude +4.45