Skip to Content
Uncategorized

First Planet Discovered Orbiting a Brown Dwarf

Astronomers have long supposed that planets can form around brown dwarfs just as they do around ordinary stars. Now they’ve found the first example

Astrophysical calculations show that any star that is smaller than about 1/10th of the mass of the sun cannot sustain hydrogen fusion reactions at its core. These failed stars never light up. Instead they wander the galaxy as warm, dark balls of hydrogen known as brown dwarfs.

Brown dwarfs probably form through the same process that lead to ordinary stars but merely on a smaller scale. If that’s correct, planets should also form in the protoplanetary disks of gas and dust around brown dwarfs. Indeed, astronomers have seen a number of protoplanetary disks of this type.

Until now, however, they’ve never seen a planet orbiting a brown dwarf. That’s not really surprising.

The standard methods for detecting planets look for the way a star wobbles as a planet orbits or at how its magnitude changes as a planet passes in front. But given that brown dwarfs are dim and difficult to see, these methods have yet to produce fruit.

All that changes today with the announcement by an international team of astronomers that they’ve discovered a planet orbiting a brown dwarf the first time. These guys have made their discovery using an entirely different method of detection called gravitational lensing. This occurs when one body passes in front of another and its gravity focuses light from the more distant object towards Earth. That works regardless of the brightnesses involved.

The brown dwarf in question is almost 6000 light years from Earth in the Fish Hook constellation. Astronomers first noticed an unusual change in its brightness in April 2012. Further investigation showed that this was indeed a lensing event.

These guys conclude that the brown dwarf is being orbited by a planet about twice the mass of Jupiter at a distance of just under one astronomical unit. The brown dwarf itself is about 10 times larger than its companion.

That’s the first time astronomers have found an object orbiting a brown dwarf that can be truly described as a planet. The technical definition of a planet is that it must have formed in the parent object’s protoplanetary disk.

Astronomers have seen other planet-sized objects orbiting brown dwarfs but only at distances of several tens of astronomical units. That’s too far to have been part of the protoplanetary disk. “Thus,…,they are not bona fide planets,” say the team.

So that’s a modest first for this team. It raises the question of what kind of conditions exist on such a planet and, of course, whether these could support life.

This planet almost certainly does not fall into that category but where there is one planet, there are almost certainly others. Astronomers can now have some fun speculating on the Goldilocks zones around brown dwarfs where conditions are just right for life and how to spot the interesting planets inside them.

Ref: arxiv.org/abs/1307.6335 : Microlensing Discovery Of A Tight, Low Mass-Ratio Planetary-Mass Object Around An Old, Field Brown Dwarf

Deep Dive

Uncategorized

Uber Autonomous Vehicles parked in a lot
Uber Autonomous Vehicles parked in a lot

It will soon be easy for self-driving cars to hide in plain sight. We shouldn’t let them.

If they ever hit our roads for real, other drivers need to know exactly what they are.

stock art of market data
stock art of market data

Maximize business value with data-driven strategies

Every organization is now collecting data, but few are truly data driven. Here are five ways data can transform your business.

Cryptocurrency fuels new business opportunities

As adoption of digital assets accelerates, companies are investing in innovative products and services.

Mifiprex pill
Mifiprex pill

Where to get abortion pills and how to use them

New US restrictions could turn abortion into do-it-yourself medicine, but there might be legal risks.

Stay connected

Illustration by Rose WongIllustration by Rose Wong

Get the latest updates from
MIT Technology Review

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

Explore more newsletters

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at customer-service@technologyreview.com with a list of newsletters you’d like to receive.