WASP-44b

Lore & Background

WASP-44b was identified as a candidate transiting planet by the SuperWASP project using the WASP-South station at the South African Astronomical Observatory. The star WASP-44 was scanned in the Cetus constellation between July and November 2009, and over 15,755 photometric measurements were collected from both WASP-South and SuperWASP-North. A later 6,000-point data set from August to November 2010 was prepared too late for the discovery paper. In 2010, the CORALIE spectrograph on the 1.2m Leonhard Euler Telescope at La Silla Observatory confirmed the planet by detecting radial velocity variations and ruling out spectroscopic binary stars. The Euler telescope also observed a transit on September 14, 2010, lasting 4.2 hours, to refine the light curve.

The planet's host star, WASP-44, is a G-type star with 0.951 solar masses and 0.927 solar radii. It has an effective temperature of 5410 K, is richer in iron than the Sun (metallicity [Fe/H] = 0.06), and is estimated to be about 900 million years old, though this age is uncertain. The star shows no chromospheric activity and does not rotate rapidly. With an apparent magnitude of 12.9, it is not visible to the unaided eye.

WASP-44b has a mass 0.889 times that of Jupiter but a radius 1.002 times Jupiter's, indicating it is bloated due to intense heating from its close star. Its orbit is nearly edge-on as seen from Earth, with an inclination of 86.02°. The discovery team discussed the difficulty of constraining orbital eccentricity for Hot Jupiters, using WASP-44b along with WASP-45b and WASP-46b to study both circular and eccentric orbital models.

Reader's Guide

WASP-44b's discovery, reported by the Royal Astronomical Society in May 2011 alongside WASP-45b and WASP-46b, contributed to the study of orbital eccentricity in Hot Jupiters. The discovery team noted that eccentricity is often poorly constrained for such planets, and they used these three new planets to explore both circular and eccentric orbital models. The planet's bloated radius, despite being less massive than Jupiter, exemplifies the common effect of stellar heating on close-in gas giants. Its very short orbital period of 2.4 days and small orbital distance of 0.03473 AU place it among the class of ultra-short-period planets that challenge theories of planetary formation and migration. The fact that the star is iron-rich and relatively young (though with large age uncertainties) adds context for understanding the planet's composition and evolution. The discovery also demonstrated the effectiveness of the SuperWASP survey in identifying transiting planets, with follow-up radial velocity confirmation from the Euler telescope.

Did You Know?

• WASP-44b orbits its star at just 3% of the Earth-Sun distance.
• The planet completes one orbit every 58.171 hours.
• Its host star WASP-44 is 95% the mass and 92% the size of the Sun.
• The discovery was reported alongside those of WASP-45b and WASP-46b.