Astronomy Now Home
Home Magazine Resources Store

On Sale Now!

The October 2014 issue of Astronomy Now is on sale! Order direct from our store (free 1st class post & to UK addresses). Astronomy Now is the only astronomy magazine specially designed to be read on tablets and phones. Download the app from Google Play Store or the Apple App Store.

Top Stories

Earthshine used to test life detection method
...By imagining the Earth as an exoplanet, scientists observing our planet's reflected light on the Moon with ESO's Very Large Telescope have demonstrated a way to detect life on other worlds...

Solid buckyballs discovered in space
...Astronomers using NASA’s Spitzer Space Telescope have detected a particular type of molecule, given the nickname “buckyball”, in a solid form for the first time...

Steamy water-world gets the Hubble treatment
...Hubble Space Telescope observations of a 7 Earth-mass planet find an unusual water-rich world swathed in a thick, steamy atmosphere...

Brown dwarf in tight orbit around young Sun-like star
Posted: 30 July 2010

Bookmark and Share

A very young brown dwarf star has been found in a tight orbit around a nearby Sun-like star.

Brown dwarfs are also known as failed stars, since although they are larger than gas giants they don't possess the mass to sustain the nuclear fusion that fully-fledged stars boast.

The relative size of a brown dwarf star compared with Jupiter, the Sun and Earth. Image: Jon Lomberg/Gemini Observatory.

Using the Near-Infrared Coronagraphic Imager (NICI) on the eight-metre Gemini-South Telescope in Chile, an international team of astronomers made a rare find: a very young brown dwarf in orbit around a 12 million year old Sun-like star, around 160 light years away. The star is so young that the astronomers say it still sports a belt of cold circumstellar gas.

But the most exciting part of the discovery is that the 36 Jupiter-mass brown dwarf, PZ Tel B, and its primary star PZ Tel A are separated by just 18 AU a similar distance that separates Uranus and the Sun. Most young brown dwarfs and planetary companions discovered through direct imaging are separated by over 50 AUs.

"Because PZ Tel A is a rare star being both close and very young, it had been imaged several times in the past," says Laird Close of the University of Arizona. "So we were quite surprised to see a new companion around what was thought to be a single star."

PZ Tel B resides just 18 AU from its parent star. Image: Beth Biller and the Gemini NICI Planet-Finding Campaign).

An image taken in 2003 of the system showed that PZ Tel B had been obscured by the glare from its parent star, suggesting that the star is on a more elliptical orbit than previously thought. "PZ Tel B travels on a particularly eccentric orbit in the last 10 years, we have literally watched it careen through its inner Solar System," says Beth Biller, lead author of the paper discussing the results, which will appear in Astrophysical Journal Letters. "This can best be explained by a highly eccentric, or oval-shaped, orbit."

The system is an important case study for the early stages of Solar System formation, and will help astronomers determine the types of planets that can form around PZ Tel A. It will also add to the ever-growing inventory of solar system configurations found outside our own.

The images were achieved by using an adaptive optics system coupled to a coronagraph to block out the excess starlight, combined with analysis techniques to reveal the orbital motion of PZ Tel B. NICI is particularly adept at this, and is currently being used to carry out a 300-star survey that is set to reveal more closely separated objects.

The Planets
From tiny Mercury to distant Neptune and Pluto, The Planets profiles each of the Solar System's members in depth, featuring the latest imagery from space missions. The tallest mountains, the deepest canyons, the strongest winds, raging atmospheric storms, terrain studded with craters and vast worlds of ice are just some of the sights you'll see on this 100-page tour of the planets.

Hubble Reborn
Hubble Reborn takes the reader on a journey through the Universe with spectacular full-colour pictures of galaxies, nebulae, planets and stars as seen through Hubble's eyes, along the way telling the dramatic story of the space telescope, including interviews with key scientists and astronauts.

3D Universe
Witness the most awesome sights of the Universe as they were meant to be seen in this 100-page extravaganza of planets, galaxies and star-scapes, all in 3D!


© 2014 Pole Star Publications Ltd.