Extrasolar Planets II


	HD168443 System The unusual system around the sun-like star HD168443 is located 123 light years away in the constellation Serpens. It is orbited by both a massive planet and another bulkier object of 17 - 40 Jupiter masses. Whether this bulky companion is a planet, a dim failed star called a brown dwarf, or some as-yet unidentified astronomical object is unclear. The star and inner planet are visible in the upper left, with the outer companion shown as a ringed world with a flare. Two rocky satellites orbit this large body.
	HD168443 c and Moons An alternate scenario to the view above is that moons orbiting the outer companion at HD168443 could cause tidal heating to occur, partially melting existing ice on one of these satellites. The moon at the upper left has the coloration of Io, indicating active volcanism. The star and inner planet are not shown in this view.

Transit of HD209458

In 1999 astronomers witnessed for the first time a distant planet passing in front of its star, providing direct and independent confirmation of the existence of extrasolar planets that previously had been inferred only from the wobble of their star.

The planet orbiting HD 209458 was discovered independently by two groups. Geoffrey Marcy of UC Berkeley and his colleagues, Paul Butler of the Carnegie Institute of Washington and Steve Vogt of UC Santa Cruz and Lick Observatory, observed a wobble in the star in late 1999. Collaborator Greg Henry at Tennessee State University observed a dip in the star's light two days later, confirming that the star had a companion.

The planetary transit was also seen by David Charbonneau of CfA and Timothy Brown from NCAR. They worked with David Latham from CfA and Michel Mayor from the Geneva Observatory, who respectively observed and confirmed the stellar wobble.

Astronomy Picture of the Day on November 15, 1999

Get a Print!

HD38529 System

HD38529 is a star located 137 light-years away in the constellation Orion. The inner 0.77 Jupiter mass planet whips around its star in 14.3 days at an average distance of 0.13 AU. A second companion exists farther out with a 2207-day orbit, shown here as a large ringed planet with three satellites. The moon close up has icy sheets and ridges similar to those found on Europa and a thin atmosphere.

Astronomy Picture of the Day on August 10, 2000

HD177830 b and Moon

HD177830 b is a 1.52 Jupiter mass planet orbiting the K0 star HD177830, located 192 light-years away in the constellation Vulpecula. This planet is likely to be within its habitable zone.
A moon found here could have liquid water and look similar to our own home world.

Tau Boötes b

This planet orbits the 4.5-magnitude star Tau Boötes. It has a mass of 4.13 Jupiters, and its orbit is 3.3 days long. Shown here is the Jupiter-like planet with its star in the background.

HD222582 b and Moon

The planet orbiting this G3 star has one of the most eccentric planet orbits known to date. The 572-day orbit takes it from 0.39 AU to 2.31 AU from its star. It is located in the constellation Aquarius, 137 light-years distant. The water on this world's satellite, if one exists, goes through seasonal periods of melting and refreezing.

47 Ursae Majoris b and Moon

47 Ursae Majoris b may resemble Jupiter in appearance and may have moons with frozen water. In this painting, there is one moon with icy polar caps. Lightning can be seen on the dark side of the planet. The sun-like star appears in the distance.

HD46375 b HD46375 b has at least 80% the mass of Saturn and is located 109 light-years away in the constellation Monoceros. It orbits its star at a distance of .041 AU, giving it an average temperature of 2070 degrees Fahrenheit. Shown here is the planet with its K1 main sequence star. The ring is composed of dust and pebbles. A ring particle has been ejected from its orbit around the planet and appears close up. In the distance is an M dwarf star, believed to be a common proper motion companion to HD46375b. Farther away is the Rosette Nebula.

HD16141 b
and Moon This planet is 70 percent the mass of Saturn and orbits .35 AU around the sun-like star HD16141 (also known as 79 Ceti). This is about the distance between Mercury and our Sun. The planet is located 117 light-years away in the constellation Cetus. HD16141b is shown in this image from the vantage point of a hypothetical moon. Any moon in existence here will be a parched 1530 degrees Fahrenheit.

The Upsilon Andromedae System [Thumbnail]

The first planetary system ever found around a normal star consists of three planets in orbit around Upsilon Andromedae. The innermost (and first known) of the three planets, Upsilon Andromedae b, contains at least three-quarters of the mass of Jupiter and orbits only 0.06 AU from the star. It traverses a circular orbit every 4.61 days. The middle planet contains at least twice the mass of Jupiter and it takes 242 days to orbit the star once. It resides approximately 0.83 AU from the star, similar to the orbital distance of Venus. The outermost planet has a mass of at least four Jupiters and completes one orbit every 3.5 to 4 years, placing it 2.5 AU from the star. The system was independently discovered by The California Planet Survey, Noyes et al at CfA, and Timothy Brown of NCAR.

Upsilon Andromedae b

Orbiting its star in 4.61 days, this planet has a mass of at least 0.7 Jupiters. The planet may be tidally locked, with one side facing the star at all times. In this image, the star is shown with the planet in the background. Gases heated by the star stream from the substellar point to the dark side of the planet.

Astronomy Picture of the Day: April 16, 1999

70 Virginis b
and Moons

This Jupiter-like planet may have moons with liquid water. In this painting, the planet is shown with a ring and two moons. One moon is small and gold in color, while the other resembles Earth, having oceans and land formations.

16 Cygni B Planet and Moon I

There are three stars in this system: two stars similar to our sun and one red dwarf. The planet has an eccentric orbit which, when compared to our own solar system, stretches from inside Venus's orbit to well beyond that of Mars. A hypothetical moon is located near the planet. If such a moon had water at one time in its history, the water would have existed as ice during part of its orbit around the star. As it neared the star the ice would have heated up, melted, and vaporized, forming a comet-like tail.

16 Cygni B Planet and Moon II

If a moon exists near the planet at 16 Cygni B, as hypothesized above, any existing water would be lost over eons of orbits around its star. In this image there is still a polar ice cap and some frost on the ground. Riverbeds and channels similar to those found on Mars can be seen. Recent impact craters dot the surface of the moon and obliterate some of the features of the channels. Co-discovered by Cochran and Hatzes.

Gliese 876 b

Gliese 876 is a red dwarf star. The outermost planet has a mass of 1.89 Jupiters and an orbital period of 61 days. Shown here are the planet and star as seen from a possible moon.
Co-discovered by Delfosse et al of the
Geneva Observatory in Switzerland.

HD217107 b

A metal rich, solar mass star warms this planet of 1.28 Jupiter masses.
Its orbital period is 7 days, with an eccentricity of 0.14.
Astronomy Picture of the Day:
December 29, 1999

HD187123 b HD187123 b is one of the "hot Jupiters", described as extrasolar planets that orbit very close in to their stars. At one time it was believed that such planets would look blue. With an orbit of just 3.097 days, this world has half of a Jupiter mass.

HD195019 b

Located in the constellation Delphinus, the planet around HD195019 resides 0.14 Astronomical Units (one A.U. equals the mean distance from the Earth to the Sun) from its host star and circuits the star once every 18.3 days. It has an estimated mass equal to 3.5 Jupiters.