Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Hubble observations confirm that planets form from disks around stars

10.10.2006
The NASA/ESA Hubble Space Telescope, in collaboration with ground-based observatories, has at last confirmed what philosopher Emmanuel Kant and scientists have long predicted: that planets form from debris disks around stars.

More than 200 years ago, the philosopher Emmanuel Kant first proposed that planets are born from disks of dust and gas that swirl around their home stars. Though astronomers have detected more than 200 extrasolar planets and have seen many debris disks around young stars, they have yet to observe a planet and a debris disk around the same star. Now, the NASA/ESA Hubble Space Telescope, in collaboration with ground-based observatories, has at last confirmed what Kant and scientists have long predicted: that planets form from debris disks around stars.


Artist’s concept of nearest exoplanet to our Solar System This is an artist's concept of a Jupiter-mass planet orbiting the nearby star Epsilon Eridani. Located 10.5 light-years away, it is the closest known exoplanet to our Solar System. The planet is in an elliptical orbit that carries it as close to the star as Earth is from the Sun, and as far from the star as Jupiter is from the Sun. Epsilon Eridani is a young star, only 800 million years old. It is still surrounded by a disk of dust that extends 30 billion kilometres from the star. The disk appears as a linear sheet of reflecting dust in this view because it is seen edge-on from the planet’s orbit, which is in the same plane as the dust disk. The planet’s rings and satellites are purely hypothetical in this view, but plausible. As a gas giant, the planet is uninhabitable for life as we know it. However, any moons might have conditions suitable for life. Astronomers determined the planet’s mass and orbital tilt in 2006 by using Hubble to measure the unseen planet's gravitational pull on the star as it slowly moved across the sky. Evidence for the planet first appeared in 2000 when astronomers measured a telltale wobble in the star. Credit: NASA, ESA, and G. Bacon (STScI)

The Hubble observations by an international team of astronomers led by G. Fritz Benedict and Barbara E. McArthur of the University of Texas, Austin, USA, show for the first time that a planet is aligned with its star’s circumstellar disk of dust and gas. The planet, detected in year 2000, orbits the nearby Sun-like star Epsilon Eridani, located 10.5 light-years from Earth in the constellation Eridanus. The planet’s orbit is inclined 30 degrees to Earth, the same angle at which the star’s disk is tilted. The results will appear in the November issue of the Astronomical Journal.

The planets in our Solar System share a common alignment, evidence that they were created at the same time in the Sun’s disk. But the Sun is a middle-aged star – 4.5 billion years old – and its debris disk dissipated long ago. Epsilon Eridani, however, still retains its disk because it is young, only 800 million years old.

The Hubble observations also helped Benedict’s team determine the planet’s true mass, which they calculate as 1.5 times Jupiter’s mass. Previous estimates measured only the lower limit, at 0.7 the mass of Jupiter. The planet, called Epsilon Eridani b, is the nearest extrasolar planet to Earth. It orbits its star every 6.9 years.

“Because of Hubble, we know for sure that it is a planet and not a failed star,” McArthur explained. Some astronomers have argued that a few of the known extrasolar planets could be brown dwarfs because their precise masses are not known. If an object is less than 10 Jupiter masses, it is a planet, not a brown dwarf.

McArthur was part of an earlier team at the University of Texas at Austin’s McDonald Observatory who discovered Epsilon Eridani b. They detected the planet using the radial-velocity method, which measures a star’s subtle motion toward and away from Earth to find unseen companions.

Epsilon Eridani is a young and active star, so some astronomers claimed that what appeared as a planet-induced wobble of the star could have been the actions of the star itself. Turbulence in the atmosphere may have produced apparent velocity changes that were intrinsic to the star and not due to a planet’s influence.

The current Benedict-McArthur team calculated the planet’s mass and its orbit by making extremely precise measurements of the star’s location as it wobbled on the sky, a technique called astrometry. The slight wobbles are caused by the gravitational tug of the unseen planet, like a small dog pulling its master on a leash. The team studied over a thousand astrometric observations from Hubble collected over three years. The astronomers combined these data with other astrometric observations made at the University of Pittsburgh’s Allegheny Observatory. They then added those measurements to hundreds of ground-based radial-velocity measurements made over the past 25 years at European Southern Observatory in Chile, McDonald Observatory at the University of Texas, Lick Observatory at the University of California Observatories, and the Canada-France-Hawaii Telescope in Hawaii. This combination allowed them to accurately determine the planet’s mass by deducing the tilt of its orbit.

If astronomers don’t know how a planet’s orbit is tilted with respect to Earth, they can only estimate a minimum mass for the planet. If only the radial velocity wobble along the line of sight is known, the planet’s mass could be significantly larger if the orbit were tilted to a nearly face-on orientation to Earth. The star would only move toward and away from Earth slightly, even though it had a massive companion.

“You can’t see the wobble induced by the planet with the naked eye,” Benedict said. “But Hubble’s fine guidance sensors are so precise that they can measure the wobble. We basically watched three years of a nearly seven-year-long dance of the star and its invisible partner, the planet, around their orbits. The fine guidance sensors measured a tiny change in the star’s position, equivalent to the width of a Euro coin 1200 km away.”

Epsilon Eridani has long captivated the attention of science fiction writers, as well as astronomers. In 1960, years before the first extrasolar planet was detected, astronomer Frank Drake listened for radio transmissions from inhabitants of any possible planets around Epsilon Eridani as part of Project Ozma’s search for intelligent extraterrestrial life. In the fictional “Star Trek” universe, Epsilon Eridani is considered by some fans to be the parent star for the planet Vulcan, Mr. Spock’s home.

No Vulcan or any other alien could live on this gas giant planet. If moons circled the planet, they would spend part of their orbit close enough to Epsilon Eridani to have surface temperatures like that of Earth, and possibly liquid water. However, the planet’s looping, “roller-coaster” orbit also would carry the moons far away from the star, a distance equal to Jupiter’s 800-million-kilometre separation from the Sun, where oceans would freeze. If a moon were massive enough, like Saturn’s giant moon Titan, it could have a sufficiently dense atmosphere that would retain heat. Such an atmosphere would suppress wide swings in surface temperatures, like covering up with a heavy blanket on a cold night. This could make such a moon potentially habitable for life as we know it, Benedict said.

Although Hubble and other telescopes cannot image the gas giant planet now, they may be able to snap pictures of it in 2007, when its orbit is closest to Epsilon Eridani. The planet may be bright enough in reflected sunlight to be imaged by Hubble, other space-based cameras, and large ground-based telescopes.

Lars Christensen | alfa
Further information:
http://www.spacetelescope.org/news/html/heic0613.html

More articles from Physics and Astronomy:

nachricht Hubble sees Neptune's mysterious shrinking storm
16.02.2018 | NASA/Goddard Space Flight Center

nachricht Supermassive black hole model predicts characteristic light signals at cusp of collision
15.02.2018 | Rochester Institute of Technology

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

Im Focus: Autonomous 3D scanner supports individual manufacturing processes

Let’s say the armrest is broken in your vintage car. As things stand, you would need a lot of luck and persistence to find the right spare part. But in the world of Industrie 4.0 and production with batch sizes of one, you can simply scan the armrest and print it out. This is made possible by the first ever 3D scanner capable of working autonomously and in real time. The autonomous scanning system will be on display at the Hannover Messe Preview on February 6 and at the Hannover Messe proper from April 23 to 27, 2018 (Hall 6, Booth A30).

Part of the charm of vintage cars is that they stopped making them long ago, so it is special when you do see one out on the roads. If something breaks or...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Fingerprints of quantum entanglement

16.02.2018 | Information Technology

'Living bandages': NUST MISIS scientists develop biocompatible anti-burn nanofibers

16.02.2018 | Health and Medicine

Hubble sees Neptune's mysterious shrinking storm

16.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>