Blue Marble 2000

Credit: R. Stockli, A. Nelson, F. Hasler,
NASA/ GSFC/ NOAA/ USGS

Explanation: This newly released digital portrait of our planet is reminiscent of the Apollo-era pictures of the “big blue marble” Earth from space. To create it, researchers at Goddard Space Flight Center’s Laboratory for Atmospheres combined data from a Geostationary Operational Environmental Satellite (GOES), the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), and the Polar Orbiting Environmental Satellites (POES) with aUSGS elevation model of Earth’s topography. Stunningly detailed, the planet’s western hemisphere is cast so that heavy vegetation is green and sparse vegetation is yellow, while the heights of mountains and depths of valleys have been exaggerated by 50 times to make vertical relief visible. Hurricane Linda is the dramatic storm off North America’s west coast. And what about the Moon? The lunar image was reconstructed from GOES data and artistically rescaled for this visualization.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

Mercury on the Horizon

Credit: Juan Carlos Casado

Explanation: Have you ever seen the planet Mercury? Because Mercury orbits so close to the Sun, it is never seen far from the Sun, and so is only visible near sunrise or sunset. If trailing the Sun, Mercurywill be visible for several minutes before it follows the Sun behind the Earth. If leading the Sun, Mercury will be visible for only several minutes before the Sun rises and hides it with increasing glare. Aninformed skygazer can usually pick Mercury out of a dark horizon glow with little more than determination. Above, a lot of determination has been combined with a little digital trickery to show Mercury’s successive positions during the middle of last month. Each picture was taken from the same location in Spain when the Sun was 10 degrees below the horizon and superposed on the single most photogenic sunset.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

A Wind From The Sun

Credit: SOHO Consortium, UVCS, EIT, ESA, NASA

Explanation: A wind from the Sun blows through our Solar System. The behaviour of comet tails as they flapped and waved in this interplanetary breeze gave astronomers the first hint of its existence. Streaming outward at 250-400 miles/second, electrons and ions boiling off the Sun’s incredibly hot but tenuous corona account for the Solar Wind – now known to affect the Earth and other planets along with voyaging spacecraft. Rooted in the Solar Magnetic Field, the structure of the corona is visible extending a million miles above the Sun’s surface in this composite image from the EIT and UVCS instruments onboard theSOHO spacecraft. The dark areas, known as coronal holes, represent the regions where the highest speed Solar Wind originates.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

Sun Storm: A Coronal Mass Ejection

Credit: SOHO Consortium, ESA, NASA

Explanation: Late last month another erupting filament lifted off the active solar surface and blasted this enormous bubble of magnetic plasma into space. Direct light from the sun is blocked in this picture of the event with the sun’s relative position and size indicated by a white half circle at bottom center. The field of view extends 2 million kilometers or more from the solar surface. While hints of these explosive events, called coronal mass ejections or CMEs, were discovered by spacecraft in the early 70s this dramatic image is part of a detailed record of this CME’s development from the presently operating SOlar and Heliospheric Observatory (SOHO) spacecraft. Near the minimum of the solar activity cycle CMEs occur about once a week, but as we approach solar maximum rates of two or more per day are anticipated. Though this CME was clearly not headed for Earth, strong CMEs are seen to profoundly influence space weather, and those directed toward our planet and can have serious effects.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

The Pipe Dark Nebula

Credit & Copyright: Jerry Lodriguss

Explanation: The dark nebula predominant at the lower left of the above photograph is known as the Pipe Nebula. The dark clouds, suggestively shaped like smoke rising from a pipe, are caused by absorption of background starlight by dust. These dust clouds can be traced all the way to the Rho Ophiuchi nebular clouds on the right. The brightest star in the field is Antares. Many types of nebula are highlighted here: the red are emission nebula, the blue are reflection nebula, and the dark are absorption nebula. This picture has been digitally enhanced.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

Southwest Mercury

Credit: Mariner 10, NASA

Explanation: The planet Mercury resembles a moon. Mercury’s old surface is heavily cratered like many moons. Mercury is larger than most moons but smaller than Jupiter’s moon Ganymede and Saturn’s moon Titan. Mercury is much denser and more massive than any moon, though, because it is made mostly of iron. In fact, the Earth is the only planet more dense. A visitor to Mercury’s surface would see some strange sights. Because Mercury rotates exactly three times every two orbits around the Sun, and because Mercury’s orbit is so elliptical, a visitor to Mercury might see the Sun rise, stop in the sky, go back toward the rising horizon, stop again, and then set quickly over the other horizon. From Earth, Mercury’s proximity to the Sun cause it to be visible only for a short time just after sunset or just before sunrise.

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)

Jupiter from Voyager

Picture Credit: NASA, JPL, NSSDC, Voyager

Explanation: Imagine a hurricane that lasted for 300 years! This picture of the planet Jupiter was taken by the Voyager 1 spacecraft as it passed the planet in 1979. Jupiter, a gas giant planet with no solid surface, is the largest planet in the solar system and is made mostly of the hydrogen and helium. Clearly visible in the photo is the Great Red Spot, a giant, hurricane-like storm system that rotates with the clouds of Jupiter. It is so large three complete Earths could fit inside it. Astronomers have observed this giant storm on Jupiter for over 300 years.

Original material on this page is copyrighted to Robert J. Nemiroff and Jerry T. Bonnell.

The Night Side of Saturn

Picture Credit: NASA, Jet Propulsion Laboratory,Voyager Project

Explanation: This image of Saturn was made in November 1980 by the Voyager 1 spacecraft as it flew past the ringed gas giant planet. From a spectacular vantage point, looking back toward the inner solar system, the robot spacecraft recorded this view of the night side of Saturn casting a sharp shadow across the bright rings. No Earth based telescope could ever take a similar picture. Since Earth is closer to the sun than Saturn, only the day side of the planet is visible from the Earth.

Original material on this page is copyrighted to Robert J. Nemiroff and Jerry T. Bonnell.