A Planet With Planets? Spitzer Finds Cosmic Oddball

November 30, 2005
A Planet With Planets? Spitzer Finds Cosmic Oddball

Planets are everywhere these days. They have been spotted around more than 150 stars, and evidence is growing that they also circle "failed," or miniature, stars called brown dwarfs. Now, astronomers using NASA's Spitzer Space Telescope say they have found what may be planets-in-the-making in the strangest of places - around a brown dwarf that itself is the size of a planet.

Image: This artist's concept compares a hypothetical solar system centered around a tiny "sun" (top) to a known solar system centered around a star, called 55 Cancri, which is about the same size as our sun. Image credit: NASA/JPL-Caltech

The little brown dwarf, called Cha 110913-773444, is one of the smallest known. At eight times the mass of Jupiter, it is even smaller than several planets around other stars.

Yet, this tiny orb might eventually host a tiny solar system. Spitzer's infrared eyes found, swirling around it, a flat disk made up of dust that is thought to gradually clump together to form planets. Spitzer has previously uncovered similar planet-forming disks around other brown dwarfs, but Cha 110913-773444 is the true dwarf of the bunch.

"Our goal is to determine the smallest 'sun' with evidence for planet formation," said Dr. Kevin Luhman of Pennsylvania State University, University Park, lead author of a new paper describing the findings in the Dec. 10 issue of Astrophysical Journal Letters. "Here, we have a sun that is so small it is the size of a planet."

Brown dwarfs are born like stars, condensing out of thick clouds of gas and dust. But unlike stars, brown dwarfs do not grow large enough to trigger nuclear fusion. They remain relatively cool spheres of gas and dust.

Astronomers have become more confident in recent years that brown dwarfs share another trait in common with stars - planets. The evidence is in the planet-forming disks. Such disks are well-documented around stars, but only recently have they been located in increasing numbers around brown dwarfs. So far, Spitzer has found dozens of disk-sporting brown dwarfs, five of which show the initial stages of the planet-building process. The dust in these five disks is beginning to stick together into what may be the "seeds" of planets (See www.nasa.gov/vision/universe/starsgalaxies/spitzer-20051020.html).

Last year, Luhman and his colleagues used Spitzer to uncover what was then the smallest of brown dwarfs hugged by a disk. At only 15 times the mass of Jupiter, the brown dwarf, called OTS 44, is comparable to the most massive extrasolar planets (See www.nasa.gov/vision/universe/starsgalaxies/spitzer-020705.html).

Now, the team has again used Spitzer, this time to detect a disk around Cha 110913-773444, which has only about half the mass of OTS 44. The object itself was discovered by Spitzer with the help of NASA's Hubble Space Telescope, the 4-meter Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile and the Gemini South Observatory, also in Chile. Its cool and dusty disk, however, could be seen by only Spitzer's infrared eyes. The teeny brown dwarf is young at 2 million years old, and lives 500 light-years away in the Chamaeleon constellation.

So, what makes this oddball a brown dwarf and not a planet? "There are two camps when it comes to defining planets versus brown dwarfs," said Dr. Giovanni Fazio, co-author of the new paper from the Harvard-Smithsonian Center for Astrophysics. "Some go by size and others go by how the object formed. For instance, this new object would be called a planet based on its size, but a brown dwarf based on how it formed. The question then becomes what do we call any little bodies that might be born from this disk - planets or moons?"

If one were to call the object a planet, then it would seem Spitzer has discovered its first "moon-forming" disk. But, no matter what the final label may be, one thing is clear: the universe produces some strange solar systems very different from our own.

Source: NASA (by Whitney Clavin/JPL)

Explore further: What smacks into Ceres stays on Ceres, research suggests

Related Stories

The (possible) dwarf planet 2007 OR10

September 3, 2015

Over the course of the past decade, more and more objects have been discovered within the trans-Neptunian region. With every new find, we have learned more about the history of our solar system and the mysteries it holds. ...

The dwarf planet Quaoar

August 28, 2015

The vast Kuiper Belt, which orbits at the outer edge of our solar system, has been the site of many exciting discoveries in the past decade or so. Otherwise known as the Trans-Neptunian region, small bodies have been discovered ...

The dwarf planet Haumea

August 14, 2015

The Trans-Neptunian region has become a veritable treasure trove of discoveries in recent years. Since 2003, the dwarf planets and "plutoids" of Eris, Sedna, Makemake, Quaoar, and Orcus were all observed beyond the orbit ...

The dwarf planet Orcus

August 31, 2015

Since the early 2000s, more and more objects have been discovered in the outer solar system that resemble planets. However, until they are officially classified, the terms Kuiper Belt Object (KBO) and Trans-Neptunian Object ...

What is A dwarf planet?

August 18, 2015

The term dwarf planet has been tossed around a lot in recent years. As part of a three-way categorization of bodies orbiting the sun, the term was adopted in 2006 due to the discovery of objects beyond the orbit of Neptune ...

Recommended for you

NASA's space-station resupply missions to relaunch

November 29, 2015

NASA's commercial space program returns to flight this week as one of its private cargo haulers, Orbital ATK, is to launch its first supply shipment to the International Space Station in more than 13 months.

CERN collides heavy nuclei at new record high energy

November 25, 2015

The world's most powerful accelerator, the 27 km long Large Hadron Collider (LHC) operating at CERN in Geneva established collisions between lead nuclei, this morning, at the highest energies ever. The LHC has been colliding ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.