Herschel observatory's population of trans-Neptunian objects

June 10, 2014
Credit: ESA/Herschel/PACS/SPIRE; acknowledgements: M. Rengel and P. Lacerda (Max-Plack-Institute für Sonnensystemforschung, Germany), T. Müller (Max-Planck-Institut für extraterrestrische Physik) and the Herschel “TNOs are Cool” Team.

(Phys.org) —ESA's Herschel space observatory has observed 132 of the known 1400 cold worlds that inhabit a region of the Solar System beyond the orbit of Neptune, some 4.5–7.5 billion km from the Sun.

These 'trans-Neptunian objects', or TNOs, include worlds such as Pluto, Eris, Haumea and Makemake, and make up a vast population of such objects thought to occupy these far-flung reaches of the Solar System.

TNOs are particularly cold, at around –230ºC, but these lend themselves to observations by Herschel, which observes at far-infrared to sub-millimetre wavelengths. Indeed, the observed the from 132 such objects during its nearly four-year lifetime.

These measurements provided their sizes and albedos (the fraction of visible light reflected from the surface), properties that are not otherwise easily accessible. The graphic presented here shows a sample of the population of TNOs observed with Herschel, arranged to showcase these properties.

What is most striking is their diversity. They range from just below 50 km to almost 2400 km in diameter; Pluto and Eris are the largest. Two worlds have distinctly elongated shapes: Haumea (seen in white) and Varuna (brown). Some even host their own moons (not shown).

The albedo measurement implies a variety of surface compositions: low albedo (brown) is an indication of dark surface materials, such as organic material, while higher albedo (white) suggests pure ices.

TNOs are thought to be some of the most primitive remnants of the planet-forming era. Thus the results of the Herschel "TNOs are cool: A survey of the trans-Neptunian region" open key time programme are being used to test different models of Solar System formation and evolution.

Explore further: Hubble harvests distant solar system objects

Related Stories

Hubble harvests distant solar system objects

September 13, 2010

Beyond the orbit of Neptune reside countless icy rocks known as trans-Neptunian objects (TNOs). One of the biggest, Pluto, is classified as a dwarf planet. The region also supplies us with comets such as famous Comet Halley. ...

How many planets are in the solar system?

May 28, 2013

I'm just going to warn you, this is a controversial topic. Some people get pretty grumpy when you ask: how many planets are in the Solar System? Is it eight, ten, or more?

Herschel intercepts asteroid Apophis

January 9, 2013

(Phys.org)—ESA's Herschel space observatory made new observations of asteroid Apophis as it approached Earth this weekend. The data shows the asteroid to be bigger than first estimated, and less reflective.

Dwarf planet Makemake reveals its secrets for the first time

November 21, 2012

Astronomers have used three telescopes at ESO's observatories in Chile to observe the dwarf planet Makemake as it drifted in front of a distant star and blocked its light. The new observations have allowed them to check for ...

Recommended for you

Hotspots in an active galactic nucleus

October 24, 2016

The nucleus of a so-called "active" galaxy contains a massive black hole that is vigorously accreting material. As a result, the nucleus often ejects bipolar jets of rapidly moving charged particles that radiate brightly ...

Kepler has caught hundreds of asteroids

October 24, 2016

Previously, the Kepler space telescope looked straight out from the solar system in a direction almost perpendicular to the ecliptic and the plane of the planets. This way, it could observe the same spot all year long, as ...

Uranus may have two undiscovered moons

October 24, 2016

NASA's Voyager 2 spacecraft flew by Uranus 30 years ago, but researchers are still making discoveries from the data it gathered then. A new study led by University of Idaho researchers suggests there could be two tiny, previously ...


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.