Featured Research

from universities, journals, and other organizations

Too Close For Comfort: Hubble Discovers An Evaporating Planet

Date:
April 7, 2003
Source:
Space Telescope Science Institute
Summary:
For the first time, astronomers using NASA's Hubble Space Telescope have observed the atmosphere of an extrasolar planet evaporating off into space. Much of the planet may eventually disappear, leaving only a dense core. The planet is a type of extrasolar planet known as a "hot Jupiter." These giant gaseous planets orbit their parent stars very closely, drawn to them like moths to a flame.

For the first time, astronomers using NASA's Hubble Space Telescope have observed the atmosphere of an extrasolar planet evaporating off into space. Much of the planet may eventually disappear, leaving only a dense core. The planet is a type of extrasolar planet known as a "hot Jupiter." These giant gaseous planets orbit their parent stars very closely, drawn to them like moths to a flame.

The scorched planet, called HD 209458b, orbits only 4 million miles (7 million kilometers) from its yellow, Sun-like star. The Hubble observations reveal a hot and puffed up evaporating hydrogen atmosphere surrounding the planet. This huge envelope of hydrogen resembles a comet with a tail trailing behind the planet. The planet circles the parent star in a tight, 3.5-day orbit. Earth also has an extended atmosphere of escaping hydrogen gas, but the loss rate is much lower.

An international team of astronomers, led by Alfred Vidal-Madjar of the Institut d'Astrophysique de Paris, CNRS, France, is reporting this discovery in the March 13 NATURE Magazine. "We were astonished to see that the hydrogen atmosphere of this planet extends over 124,000 miles (200,000 kilometers)," says Vidal-Madjar.

HD 209458b is too close to the star for Hubble to photograph directly. However, astronomers could observe the planet indirectly since it blocks light from a small part of the star during transits across the disk of the star, thereby dimming it slightly. Light passing through the atmosphere around the planet is scattered and acquires a signature from the atmosphere. In a similar way, the Sun's light is reddened as it passes obliquely through the Earth's atmosphere at sunset. Astronomers used Hubble's Space Telescope Imaging Spectrograph (STIS) to measure how much of the planet's atmosphere filters light from the star. They saw a startling drop in the star's hydrogen emission. A huge puffed up atmosphere can best explain this result.

The planet's outer atmosphere is extended and heated so much by the nearby star that it starts to escape the planet's gravity. "The atmosphere is heated, the hydrogen escapes the planet's gravitational pull and is pushed away by the starlight, fanning out in a large tail behind the planet - like that of a comet," says Alain Lecavelier des Etangs at the Institut d'Astrophysique de Paris, CNRS, France. Astronomers estimate the amount of hydrogen gas escaping HD 209458b to be at least 10,000 tons per second, but possibly much more.

Hot Jupiters orbit precariously close to their stars. They are giant gaseous planets that must have formed in the cold outer reaches of the star system and then spiraled into their close orbits. This new discovery might help explain why hot Jupiters so often orbit a few million miles from their parent stars. Like HD 209458b, they are not usually found much closer than 4 million miles. Currently, the closest distance is 3.5 million miles (5.7 million kilometers). Hot Jupiters have orbits that are as brief as three days, but not shorter. Perhaps the evaporation of the atmosphere plays a role in setting an inner boundary for orbits of hot Jupiters.

HD 209458b has a diameter 1.3 times that of Jupiter, and two-thirds the mass. Its orbit is one-eighth the size of Mercury's orbit around the Sun. The parent star is similar to our Sun and lies 150 light-years from Earth. It is visible with binoculars as a seventh magnitude star in the constellation Pegasus. In 1999 this star suddenly entered the astronomical "Hall of Fame" when HD 209458b was seen passing in front of the star and partly eclipsing it. This was the first confirmed transiting extrasolar planet ever discovered. In 2001 Hubble detected the element sodium in the lower part of HD 209458b's atmosphere, the first signature of an atmosphere on any extrasolar planet.

The team is composed of A. Vidal-Madjar, A. Lecavelier des Etangs and J.-M. Dιsert (Institut d'Astrophysique de Paris, CNRS, France), G. Ballester (University of Arizona), R. Ferlet and G. Hιbrard (Institut d'Astrophysique de Paris, France), and M. Mayor (Geneve Observatory, Switzerland). They observed three transits of the planet in front of the star with Hubble. Observations of the atomic hydrogen envelope were made in ultraviolet (Lyman-alpha) light with Hubble's STIS. Hubble's position above the atmosphere makes it the only telescope that can currently perform this type of ultraviolet study.


Story Source:

The above story is based on materials provided by Space Telescope Science Institute. Note: Materials may be edited for content and length.


Cite This Page:

Space Telescope Science Institute. "Too Close For Comfort: Hubble Discovers An Evaporating Planet." ScienceDaily. ScienceDaily, 7 April 2003. <www.sciencedaily.com/releases/2003/04/030407080909.htm>.
Space Telescope Science Institute. (2003, April 7). Too Close For Comfort: Hubble Discovers An Evaporating Planet. ScienceDaily. Retrieved April 23, 2014 from www.sciencedaily.com/releases/2003/04/030407080909.htm
Space Telescope Science Institute. "Too Close For Comfort: Hubble Discovers An Evaporating Planet." ScienceDaily. www.sciencedaily.com/releases/2003/04/030407080909.htm (accessed April 23, 2014).

Share This



More Space & Time News

Wednesday, April 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Nuclear-Level Asteroids Might Be More Common Than We Realize

Nuclear-Level Asteroids Might Be More Common Than We Realize

Newsy (Apr. 23, 2014) — The B612 Foundation says asteroids strike Earth much more often than previously thought, and are hoping to build an early warning system. Video provided by Newsy
Powered by NewsLook.com
NASA Chief Outlines Plan for Human Mission to Mars

NASA Chief Outlines Plan for Human Mission to Mars

AFP (Apr. 22, 2014) — NASA administrator Charles Bolden, speaking at the 'Human to Mars Summit' in Washington, says that learning more about the Red Planet can help answer the 'fundamental question' of 'life beyond Earth'. Duration: 00:48 Video provided by AFP
Powered by NewsLook.com
Nasa Gives You An Excuse to Post a Selfie on Earth Day

Nasa Gives You An Excuse to Post a Selfie on Earth Day

TheStreet (Apr. 22, 2014) — NASA is inviting all social media users to take a selfie of themselves alongside nature and to post it to Twitter, Facebook, Flickr, Instagram, or Google Plus with the hashtag #globalselfie. NASA's goal is to crowd-source a collection of snapshots of the earth, ground-up, that will be used to create one "unique mosaic of the Blue Marble." This image will be available to all in May. Since this is probably one of the few times posting a selfie to Twitter won't be embarrassing, we suggest you give it a go for a good cause. Video provided by TheStreet
Powered by NewsLook.com
SpaceX's Dragon Spacecraft Captured by International Space Station

SpaceX's Dragon Spacecraft Captured by International Space Station

Reuters - US Online Video (Apr. 20, 2014) — SpaceX's unmanned Dragon spacecraft makes a scheduled Easter Sunday rendezvous with the International Space Station. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins