Archives

Astronomy Picture of the Day

Human as Spaceship
Space Image Credit: NASA, ESA, Hubble, and J. Maiz- Apellániz (IAA); Acknowledgement: D. De Martin;
Human Image Copyright: Charis Tsevis; Composition: R. J. Nemiroff

Explanation: You are a spaceship soaring through the universe. So is your dog. We all carry with us trillions of microorganisms as we go through life. These multitudes of bacteria, fungi, and archaea have different DNA than you. Collectively called your microbiome, your shipmates outnumber your own cells. Your crew members form communities, help digest food, engage in battles against intruders, and sometimes commute on a liquid superhighway from one end of your body to the other. Much of what your microbiome does, however, remains unknown. You are the captain, but being nice to your crew may allow you to explore more of your local cosmos.

Tomorrow’s picture: volcanic clouds

Astronomy Picture of the Day

1901 Photograph: The Orion Nebula
Image Credit: George Ritchey, Yerkes Observatory – Digitization Project: W. Cerny,
R. Kron, Y. Liang, J. Lin, M. Martinez, E. Medina, B. Moss, B. Ogonor, M. Ransom, J. Sanchez (Univ. of Chicago)

Explanation: By the turn of the 20th century advances in photography contributed an important tool for astronomers. Improving photographic materials, long exposures, and new telescope designs produced astronomical images with details not visible at the telescopic eyepiece alone. Remarkably recognizable to astrophotographers today, this stunning image of the star forming Orion Nebula was captured in 1901 by American astronomer and telescope designer George Ritchey. The original glass photographic plate, sensitive to green and blue wavelengths, has been digitized and light-to-dark inverted to produce a positive image. His hand written notes indicate a 50 minute long exposure that ended at dawn and a reflecting telescope aperture of 24 inches masked to 18 inches to improve the sharpness of the recorded image. Ritchey’s plates from over a hundred years ago preserve astronomical data and can still be used for exploring astrophysical processes.

Tomorrow’s picture: human spaceship


Astronomy Picture of the Day

The Perseids and the Plough
Image Credit & Copyright: Jeff Dai (TWAN)

Explanation: Despite interfering moonlight, many denizens of planet Earth were able to watch this year’s Perseid meteor shower. This pastoral scene includes local skygazers admiring the shower’s brief, heavenly flashes in predawn hours near peak activity on August 13 from Nalati Grassland in Xinjiang, China. A composite, the image registers seven frames taken during a two hour span recording Perseid meteor streaks against a starry sky. Centered along the horizon is the Plough, the north’s most famous asterism, though some might see the familiar celestial kitchen utensil known as the Big Dipper. Perhaps the year’s most easily enjoyed meteor shower, Perseid meteors are produced as Earth itself sweeps through dust from periodic comet Swift-Tuttle. The dust particles are vaporized at altitudes of 100 kilometers or so as they plow through the atmosphere at 60 kilometers per second.

Tomorrow’s picture: just so story

Astronomy Picture of the Day

Saturn Behind the Moon
Image Credit: Peter Patonai (Astroscape Photography)

Explanation: What’s that next to the Moon? Saturn. In its monthly trip around the Earth — and hence Earth’s sky — our Moon passed nearly in front of Sun-orbiting Saturn earlier this week. Actually the Moon passed directly in front of Saturn from the viewpoints of a wide swath of Earth’s Southern Hemisphere. The featured image from Sydney, Australia captured the pair a few minutes before the eclipse. The image was a single shot lasting only 1/500th of a second, later processed to better highlight both the Moon and Saturn. Since Saturn is nearly opposite the Sun, it can be seen nearly the entire night, starting at sunset, toward the south and east. The gibbous Moon was also nearly opposite the Sun, and so also visible nearly the entire night — it will be full tomorrow night. The Moon will occult Saturn again during every lap it makes around the Earth this year.

Tomorrow’s picture: open space

Astronomy Picture of the Day

Supernova Cannon Expels Pulsar J0002
Image Credit: F. Schinzel et al. (NRAO, NSF), Canadian Galactic Plane Survey (DRAO), NASA (IRAS); Composition: Jayanne English (U. Manitoba)

Explanation: What could shoot out a neutron star like a cannon ball? A supernova. About 10,000 years ago, the supernova that created the nebular remnant CTB 1 not only destroyed a massive star but blasted its newly formed neutron star core — a pulsar — out into the Milky Way Galaxy. The pulsar, spinning 8.7 times a second, was discovered using downloadable software Einstein@Home searching through data taken by NASA’s orbiting Fermi Gamma-Ray Observatory. Traveling over 1,000 kilometers per second, the pulsar PSR J0002+6216 (J0002 for short) has already left the supernova remnant CTB 1, and is even fast enough to leave our Galaxy. Pictured, the trail of the pulsar is visible extending to the lower left of the supernova remnant. The featured image is a combination of radio images from the VLA and DRAO radio observatories, as well as data archived from NASA’s orbiting IRAS infrared observatory. It is well known that supernovas can act as cannons, and even that pulsars can act as cannonballs — what is not known is how supernovas do it.

Tomorrow’s picture: around antares

Astronomy Picture of the Day

Perseid Meteors over Slovakia
Image Credit & Copyright: Petr Horálek

Explanation: Tonight is a good night to see meteors. Comet dust will rain down on planet Earth, streaking through dark skies during the peak of the annual Perseid Meteor Shower. The featured composite image was taken during last year’s Perseids from the Poloniny Dark Sky Park in Slovakia. The unusual building in the foreground is a planetarium on the grounds of Kolonica Observatory. Although the comet dust particles travel parallel to each other, the resulting shower meteors clearly seem to radiate from a single point on the sky in the eponymous constellation Perseus. The radiant effect is due to perspective, as the parallel tracks appear to converge at a distance, like train tracks. The Perseid Meteor Shower is expected to peak after midnight tonight, although unfortunately this year the sky will be brightened by a near full Moon.

Tomorrow’s picture: supernova cannonball

Astronomy Picture of the Day

Arp 87: Merging Galaxies from Hubble
Image Credit: NASA, ESA, Hubble Heritage Team (STScI, AURA)

Explanation: This dance is to the death. Along the way, as these two large galaxies duel, a cosmic bridge of stars, gas, and dust currently stretches over 75,000 light-years and joins them. The bridge itself is strong evidence that these two immense star systems have passed close to each other and experienced violent tides induced by mutual gravity. As further evidence, the face-on spiral galaxy on the right, also known as NGC 3808A, exhibits many young blue star clusters produced in a burst of star formation. The twisted edge-on spiral on the left (NGC 3808B) seems to be wrapped in the material bridging the galaxies and surrounded by a curious polar ring. Together, the system is known as Arp 87 and morphologically classified, technically, as peculiar. While such interactions are drawn out over billions of years, repeated close passages should ultimately result in the death of one galaxy in the sense that only one galaxy will eventually result. Although this scenario does look peculiar, galactic mergers are thought to be common, with Arp 87 representing a stage in this inevitable process. The Arp 87 pair are about 300 million light-years distant toward the constellation Leo. The prominent edge-on spiral galaxy at the far left appears to be a more distant background galaxy and not involved in the on-going merger.

Tomorrow’s picture: perseid meteors