An Exoplanet Orbiting 51 Eridani

This brief (~4 second) video shows a Jupiter-sized exoplanet orbiting 51 Eridani. The star’s planetary system is face-on as seen from Earth, giving us a bird’s-eye view of the planet’s motion as it orbits about 18 billion km from the star. The video was assembled from five images taken over four years with the Gemini South Telescope in Chile. The Gemini Planet Imager blocks out most of the star’s light so that the much fainter and smaller exoplanet can be seen.

Video Credit: Jason Wang (Caltech) / Gemini Planet Imager Exoplanet Survey

It’s Raining Iron on WASP-76b

The star WASP-76 is about 360 light-years from Earth in the constellation of Pisces. This animations shows the orbit of one of its planets called WASP-76b. The planet’s orbit is very close to the star, and it is tidally locked, so on side faces the star all the time. Day side temperatures range above 2400 C, high enough to vaporise metals. Winds circulate iron vapor to the cooler night side where it condenses and falls as iron droplets.

Video Credit: ESO

A Red Dwarf

Proxima_CentauriA red dwarf is a small and relatively cool star on the main sequence. Red dwarfs range in mass from about 7 to roughly 50 percent the mass of the Sun and have surface temperatures of less than 4,000 K. They are by far the most common type of star in the Milky Way, but because they are dim in the visible light spectrum, individual red dwarfs cannot easily be observed. Indeed, not a single one can be seen by the naked eye from Earth. According to some estimates, three-fourths of the stars in the Milky Way are red dwarfs—as is our nearest neighbor.

Proxima Centauri  is a red dwarf about 4.24 light-years from the Sun and is the nearest known star to the Sun. Its distance to the second- and third-nearest stars, which form the bright binary Alpha Centauri, is sufficiently close (about .24 light-year) that it is very likely part of a triple star system with Alpha Centauri A and B, but its orbital period in that system may be greater than 500,000 years.

n 2016, a planet designated Proxima Centauri b was found orbiting the star at a distance of roughly 0.05 AU (7.5 million km) with an orbital period of about 11.2 Earth days. Its estimated mass is at least 1.3 times that of the Earth, and the planet’s average temperature is estimated to be within the range of where liquid water could exist. While the planet is within the “habitable zone,” Proxima Centauri is a red dwarf and a flare star, so it’s not considered likely to support life.

Image Credit: NASA

Looking at an Exoplanet

The SPHERE instrument on the Very Large Telescope at the European Southern Observatory has captured a series of images showing the passage of the exoplanet Beta Pictoris b around its parent star. SPHERE observed Beta Pictoris b directly, seeing it emerge from its passage in front of its parent star. The planet orbits its star at about the same distance as between the Sun and Saturn, approximately 1.3 billion km, making it the most closely orbiting exoplanet ever to have been directly imaged. In spite of the distance from its star, planet is still hot, around 1500 C.

Image Credit: ESO

Too Close for Comfort

Video Credit: NASA

UPDATE—A personal note: I contributed to the design of components of the Burst Alert Telescope instrument on Swift. My contributions include the ultra-quiet power regulators for the detectors in the instrument, the variable high-voltage supply for the detectors, and the pulse-width-modulation regulator for the thermal control system of the BAT. The same PWM regulator was also used in other locations on the satellite.

The Shadow Knows

twhydraeThese images were taken a year apart by the Hubble Space Telescope. They reveal a shadow moving counterclockwise around a gas-and-dust disk encircling the young star TW Hydrae. The two images at the top show an uneven brightness across the disk. In the bottom pair of images, which have have been subjected to enhanced image processing, the darkening becomes even more apparent. The dimmer areas of the disk are caused by a shadow spreading across the outer disk. The dotted lines approximate the shadow’s coverage, and the long arrows show how far the shadow has moved in a year (from 2015 to 2016), roughly 20 degrees. Using Hubble archival data, astronomers have determined that the shadow completes a rotation around the central star every 16 years. The feature is certainly a shadow because dust and gas in the disk do not orbit the star nearly that quickly. The, the feature must not be caused by a part of the physical disk. The shadow might be caused by the gravitational effect of an unseen planet orbiting close to the star. Such a planet could  disturb material from the main disk, creating a warped inner disk, and the twisted disk might block light from the star, casting a shadow onto the disk’s outer region.

Image Credits: NASA / ESA