Young Star's Companion Has Only Forty Times the Mass of Jupiter

Feb 25, 2005
Figure 1

Astronomers have weighed DH Tauri's companion and have found that it is a brown dwarf with only 40 times the mass of Jupiter. DH Tauri is a young star only one million years old in the constellation Taurus. It is so young it will not begin nuclear fusion for another one hundred million years. It is 460 light years away and two thirds as massive as the Sun. Its companion is among the coolest and lightest of known brown dwarfs orbiting young stars. If the companion had been less massive it probably would have been a planet. A team from the National Astronomical Observatory of Japan, Kobe University, the University of Tokyo, and the Graduate University for Advanced Studies conducted this research.

The search for planets outside our solar system (extrasolar planets) motivates much of modern astronomy. Subaru Telescope is contributing to this search by observing many nearby young stars in the constellation Taurus with its Coronagraphic imager with Adaptive Optics (CIAO). (See our April 2004 press release for more information on this program and an image of a protoplanetary disk.)

CIAO's speciality is observing faint objects near bright objects. CIAO sharpens an image using a technique called adaptive optics, and blocks the light from a bright object using a mask called a coronagraph.

The research team targeted young stars since planets and brown dwarfs are brighter when they are young. Planets weigh less than 13 times the mass of Jupiter. Brown dwarfs are 13 to 80 times more massive than Jupiter. Unlike stars like the Sun, brown dwarfs don't have enough mass to generate energy through nuclear fusion.

So far, extrasolar planets orbiting around normal stars have been detected only by indirect means, such as observing the wobble in the main star caused by the gravitational tug and pull with the orbiting planet. No direct image of an extrasolar planet around a normal star exists to date. If astronomers could get a direct image of an extrasolar planet, they can begin to study physical properties such as temperature and composition.

When the research team took an image of the star DH Tauri (abbreviated as DH Tau), they noticed an object 250 times fainter 2.3 arcseconds away. At the distance of DH Tauri (460 light years), this separation is equivalent to 330 times the distance between Earth and the Sun. Although the object was in older images of DH Tauri, its location in the new image revealed that it was not an unrelated background object, but a companion that orbits DH Tauri.

Figure 2

Figure 2: The spectrum of the companion from 1 to 2.5 μm.


To understand the physical nature of this companion, the team made followup observations using a spectrograph on Subaru (the Cooled Infrared Spectrograph and Camera; CISCO), The companion's spectrum in the 1 to 2.5 μm region shows signatures of water and potassium. From these, the research team can infer that the surface temperature of the companion is about 2700 to 2800 degrees Kelvin, its surface gravity is 4 times that of Jupiter and its mass is only 40 times larger than Jupiter. This puts the companion in the brown dwarf category.

Yoichi Itoh from the Kobe University says "this discovery gives substance to our hope that we can find a planet with a mass comparable to Jupiter using our technique and strategy." "We are getting ever closer to our goal of getting an image of an extrasolar planet," he says.

Source: National Astronomical Observatory of Japan


Explore further: US astronauts to step out on spacewalk for repairs

add to favorites email to friend print save as pdf

Related Stories

A sharp eye on Southern binary stars

Apr 17, 2014

Unlike our sun, with its retinue of orbiting planets, many stars in the sky orbit around a second star. These binary stars, with orbital periods ranging from days to centuries, have long been the primary ...

Sakurai's Object: Stellar evolution in real time

Apr 02, 2014

(Phys.org) —Stellar lifetimes are measured in billions of years, so changes in their appearance rarely take place on a human timescale. Thus an opportunity to observe a star passing from one stage of life ...

Review: Updated HTC One phone worth considering

Mar 25, 2014

The HTC One might be the best smartphone you never heard of. The phone won critical acclaim last year, yet it barely made a dent in the marketplace. It's overshadowed by Apple's iPhones and Samsung's Galaxy ...

Hardy star survives supernova blast

Mar 20, 2014

(Phys.org) —When a massive star runs out fuel, it collapses and explodes as a supernova. Although these explosions are extremely powerful, it is possible for a companion star to endure the blast. A team ...

Recommended for you

How many moons does Venus have?

1 hour ago

There are dozens upon dozens of moons in the Solar System, ranging from airless worlds like Earth's Moon to those with an atmosphere (most notably, Saturn's Titan). Jupiter and Saturn have many moons each, ...

A star's early chemistry shapes life-friendly atmospheres

2 hours ago

Born in a disc of gas and rubble, planets eventually come together as larger and larger pieces of dust and rock stick together. They may be hundreds of light-years away from us, but astronomers can nevertheless ...

User comments : 0

More news stories

How many moons does Venus have?

There are dozens upon dozens of moons in the Solar System, ranging from airless worlds like Earth's Moon to those with an atmosphere (most notably, Saturn's Titan). Jupiter and Saturn have many moons each, ...

Male-biased tweeting

Today women take an active part in public life. Without a doubt, they also converse with other women. In fact, they even talk to each other about other things besides men. As banal as it sounds, this is far ...

High-calorie and low-nutrient foods in kids' TV

Fruits and vegetables are often displayed in the popular Swedish children's TV show Bolibompa, but there are also plenty of high-sugar foods. A new study from the University of Gothenburg explores how food is portrayed in ...