Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2016 July 15

NGC 2736: The Pencil Nebula
Image Credit & Copyright: Howard Hedlund & Dave Jurasevich, Las Campanas Obs.

Explanation: Moving from top to bottom in the frame near the center of this sharply detailed color composite, thin, bright, braided filaments are actually long ripples in a cosmic sheet of glowing gas seen almost edge-on. The shock wave plows through interstellar space at over 500,000 kilometers per hour. Cataloged as NGC 2736, its elongated appearance suggests its popular name, the Pencil Nebula. The Pencil Nebula is about 5 light-years long and 800 light-years away, but represents only a small part of the Vela supernova remnant. The Vela remnant itself is around 100 light-years in diameter, the expanding debris cloud of a star that was seen to explode about 11,000 years ago. Initially, the shock wave was moving at millions of kilometers per hour but has slowed considerably, sweeping up surrounding interstellar material. In the narrowband, wide field image, red and blue-green colors track the characteristic glow of ionized hydrogen and oxygen atoms.

Moon, Saturn, Antares on July 15

Tonight – July 15, 2016 – the very bright waxing gibbous moon will erase many stars from the slate of night. Will you see the planet Saturn in the moon’s glare? Probably, if you look, and if clouds don’t hide them. If not, try covering the moon with your finger to gaze at nearby Saturn. Although the supergiant red star Antares is not as bright as Saturn, it might be easier to see since it’s a little farther from the moon’s glare. Follow the links below to find out more about the two celestial lights that are closest to the moon on July 15, 2016.

Ringed planet Saturn

Supergiant star Antares

Saturn, sixth planet out from the sun, is the farthest world you can easily see with your unaided eye. It’s 10 Astronomical Units from the sun (10 times the Earth-sun distance), and, right now, it’s about 9.3 Astronomical Units from Earth. One Astronomical Unit equals about 93 million miles (150 million km).

Saturn is often called the jewel of the solar system because of its gorgeous ring system. Saturn’s rings are enormously expansive and wide, but extremely thin. The main rings extend nearly as far the moon’s distance from Earth, yet are only about one kilometer thick. With even a modest telescope, you should be able to see Saturn’s rings easily in July 2016, as they are inclined at 26^o from edge-on.

Saturn, the second-largest planet after Jupiter, has a diameter that’s a good 9 times greater than Earth’s. Like Jupiter, Saturn is a gas giant world, composed of mainly hydrogen and helium.

Unlike the inner rocky planets – Mercury, Venus, Earth and Mars – Saturn and Jupiter have no solid surfaces on which to stand.

Antares is the brightest star in the constellation Scorpius the Scorpion. It is a red supergiant star. In fact, this star dwarfs the sun to almost nothingness. While the volume of the sun is approximately 1.3 million times that of our planet Earth, Antares has the volume of hundreds of millions of suns. If by some bit of magic Antares were suddenly substituted for our sun, the surface of the star would extend well past the orbit of Mars!

Antares is classified as an M1 supergiant star. The M1 designation says that Antares is reddish in color and cooler than many other stars. Its surface temperature of 3500 kelvins (about 5800 degrees F.) is in contrast to about 10,000 degrees F. for our sun.

Even though Antares’ surface temperature is relatively low, Antares’ tremendous surface area – the surface from which light can escape – makes this star very bright. In fact, Antares approaches 11,000 times the brilliance of our puny sun, a G2 star.

Stellar luminosity: The true brightnesses of stars

But that is just in visible light. When all wavelengths of electromagnetic radiation is considered, Antares pumps out more than 60,000 times the energy of our sun!

Bottom line: Look at the moon on July 15, 2016, and you’ll likely notice two nearby objects. One is the planet Saturn, and the other is the star Antares.

Author

The Words of Confucius

The firm, the enduring, the simple, and the modest are near to virtue.

Your Charm for Today

Today’s Meaning:
The hand indicates you will need to extend effort to protect this aspect from outside influences. The devices attached indicate you will need tools to be successful in your protection.

General Description:
The use of a representation of the Hand as a talisman can be traced back to at least 800 years B.C., when it was used as a charm against enchantment. Many varieties of the Hand exist; in some the elaboration is very marked, each devise represents some particular charm. Life size models of these Hands were supposed to guard the house against all the influences of magic and evil, and smaller replicas protected their wearers from every description of harm. The extended thumb and first two fingers, the third and fourth fingers closed, is the position still assumed during the benediction in some Christian Churches of today.