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.

2021 December 22

Launch of the IXPE Observatory

Image Credit & Copyright: Jordan Sirokie

Explanation: Birds don’t fly this high. Airplanes don’t go this fast. The Statue of Liberty weighs less. No species other than human can even comprehend what is going on, nor could any human just a millennium ago. The launch of a rocket bound for space is an event that inspires awe and challenges description. Pictured here, a SpaceX Falcon 9 rocket lifted off from Kennedy Space Center, Florida earlier this month carrying the Imaging X-ray Polarimetry Explorer (IXPE). IXPE is scheduled to observe high-energy objects such as neutron stars, black holes, and the centers of distant galaxies to better determine the physics and geometries that create and control them. From a standing start, the 300,000+ kilogram rocket ship lifted IXPE up to circle the Earth, where the outside air is too thin to breathe. Rockets bound for space are now launched from somewhere on Earth every few days.

Launch Update: James Webb Space Telescope

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.

2021 December 19

Planetary Alignment over Italy

Image Credit & Copyright: Antonio Finazzi

Explanation: It is not a coincidence that planets line up. That’s because all of the planets orbit the Sun in (nearly) a single sheet called the plane of the ecliptic. When viewed from inside that plane — as Earth dwellers are likely to do — the planets all appear confined to a single band. It is a coincidence, though, when three of the brightest planets all appear in nearly the same direction. Such a coincidence was captured earlier this month. Featured above (right to left), Venus, Saturn, and Jupiter were all imaged together in a line just after sunset, from the San Fermo Hills, Bergamo, Italy. Joining the alignment are Earth’s Moon, and the position of the more distant Uranus. Bands of clouds streak across the sky toward the setting Sun. As Comet Leonard fades, this planetary alignment — absent the Moon — should persist for the rest of the month.

Discovery + Outreach: Graduate student research position open for APOD

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.

2021 December 14

HH 666: Carina Dust Pillar with Jet

Image Credit: NASA, ESA, Hubble; Processing & Copyright: Mehmet Hakan Özsaraç

Explanation: To some, it may look like a beehive. In reality, the featured image from the Hubble Space Telescope captures a cosmic pillar of dust, over two-light years long, inside of which is Herbig-Haro 666 — a young star emitting powerful jets. The structure lies within one of our galaxy’s largest star forming regions, the Carina Nebula, shining in southern skies at a distance of about 7,500 light-years. The pillar‘s layered outline are shaped by the winds and radiation of Carina’s young, hot, massive stars, some of which are still forming inside the nebula. A dust-penetrating view in infrared light better shows the two, narrow, energetic jets blasting outward from a still hidden infant star.

Open Science: Browse 2,600+ codes in the Astrophysics Source Code Library

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.

2021 December 13

Meteors and Auroras over Iceland

Image Credit & Copyright: James Boardman-Woodend; Annotation: Judy Schmidt

Explanation: What’s going on behind that mountain? Quite a bit. First of all, the mountain itself, named Kirkjufell, is quite old and located in western Iceland near the town of Grundarfjörður. In front of the steeply-sloped structure lies a fjord that had just begun to freeze when the above image was taken — in mid-December of 2012. Although quite faint to the unaided eye, the beautiful colors of background aurorae became quite apparent on the 25-second exposure. What makes this image of particular note, though, is that it also captures streaks from the Geminids meteor shower — meteors that might not have been evident were the aurora much brighter. Far in the distance, on the left, is the band of our Milky Way Galaxy, while stars from our local part of the Milky Way appear spread across the background. Tonight the Geminids meteor shower peaks again and may well provide sky enthusiasts with their own memorable visual experiences.

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.

2021 December 12

Comet Leonard Before Star Cluster M3

Image Credit & Copyright: Dan Bartlett

Explanation: Comet Leonard is now visible to the unaided eye — but just barely. Passing nearest to the Earth today, the comet is best seen this week soon after sunset, toward the west, low on the horizon. Currently best visible in the north, by late December the comet will best be seen from south of Earth’s equator. The featured image of Comet C/2021 A1 (Leonard) was taken a week ago from California, USA. The deep exposure shows in great detail the comet’s green gas coma and developing dust tail. The comet — across our inner Solar System and only light-minutes away — was captured passing nearly in front of globular star cluster M3. In contrast, M3 is about 35,000 light-years away. In a week, Comet Leonard will pass unusually close to Venus, but will continue on and be at its closest to the Sun in early January.

Tomorrow’s picture: meteor mountain

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.

2021 December 10

Eclipse on a Polar Day

Image Credit & Copyright: Stephanie Ziyi Ye

Explanation: During polar day, in Arctic and Antarctic summer, the Sun stays above the horizon for periods of 24 hours or more. Recorded on December 4, this fisheye timelapse image tracks the Sun in multiple frames as it completes a circle in the summer sky above Union Glacier, Antarctica. Of course on that date, Union Glacier’s sky did grow dark even though the Sun was above the horizon. Captured during the brief period of totality, an eclipsed Sun is at bottom center of the composite view. Near the edge of the total eclipse path across planet Earth, the Moon’s shadow darkens the sky above.

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.

2021 December 8

Comet Hale-Bopp Over Val Parola Pass

Image Credit & Copyright: A. Dimai, (Col Druscie Obs.), AAC

Explanation: Comet Hale-Bopp, the Great Comet of 1997, became much brighter than any surrounding stars. It was seen even over bright city lights. Away from city lights, however, it put on quite a spectacular show. Here Comet Hale-Bopp was photographed above Val Parola Pass in the Dolomite mountains surrounding Cortina d’Ampezzo, Italy. Comet Hale-Bopp‘s blue ion tail, consisting of ions from the comet’s nucleus, is pushed out by the solar wind. The white dust tail is composed of larger particles of dust from the nucleus driven by the pressure of sunlight, that orbit behind the comet. Comet Hale-Bopp (C/1995 O1) remained visible to the unaided eye for 18 months — longer than any other comet in recorded history. The large comet is next expected to return around the year 4385. This month, Comet Leonard is brightening and may soon become visible to the unaided eye.

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.

2021 December 7

Ninety Gravitational Wave Spectrograms and Counting

Image Credit: NSF, LIGO, VIRGO, KAGRA, Georgia Tech, Vanderbilt U.; Graphic : Sudarshan Ghonge & Karan Jani

Explanation: Every time two massive black holes collide, a loud chirping sound is broadcast out into the universe in gravitational waves. Humanity has only had the technology to hear these unusual chirps for the past seven years, but since then we have heard about 90 — during the first three observing runs. Featured above are the spectrograms — plots of gravitational-wave frequency versus time — of these 90 as detected by the giant detectors of LIGO (in the USA), VIRGO (in Europe), and KAGRA (in Japan). The more energy received on Earth from a collision, the brighter it appears on the graphic. Among many science firsts, these gravitational-radiation chirps are giving humanity an unprecedented inventory of black holes and neutron stars, and a new way to measure the expansion rate of our universe. A fourth gravitational wave observing run with increased sensitivity is currently planned to begin in 2022 December.

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.

2021 December 2

NGC 6822: Barnard’s Galaxy

Image Credit & Copyright: Dietmar Hager, Eric Benson

Explanation: Grand spiral galaxies often seem to get all the glory, flaunting their young, bright, blue star clusters in beautiful, symmetric spiral arms. But small galaxies form stars too, like nearby NGC 6822, also known as Barnard’s Galaxy. Beyond the rich starfields in the constellation Sagittarius, NGC 6822 is a mere 1.5 million light-years away, a member of our Local Group of galaxies. A dwarf irregular galaxy similar to the Small Magellanic Cloud, NGC 6822 is about 7,000 light-years across. Brighter foreground stars in our Milky Way have a spiky appearance. Behind them, Barnard’s Galaxy is seen to be filled with young blue stars and mottled with the telltale pinkish hydrogen glow of star forming regions in this deep color composite image.

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.

2021 December 1

A Blue-Banded Blood Moon

Image Credit: Angel Yu

Explanation: What causes a blue band to cross the Moon during a lunar eclipse? The blue band is real but usually quite hard to see. The featured HDR image of last week’s lunar eclipse, however — taken from Yancheng, China — has been digitally processed to equalize the Moon’s brightness and exaggerate the colors. The gray color of the bottom right is the Moon‘s natural color, directly illuminated by sunlight. The upper left part of the Moon is not directly lit by the Sun since it is being eclipsed — it in the Earth’s shadow. It is faintly lit, though, by sunlight that has passed deep through Earth’s atmosphere. This part of the Moon is red — and called a blood Moon — for the same reason that Earth’s sunsets are red: because air scatters away more blue light than red. The unusual blue band is different — its color is created by sunlight that has passed high through Earth’s atmosphere, where red light is better absorbed by ozone than blue. A total eclipse of the Sun will occur tomorrow but, unfortunately, totality be visible only near the Earth’s South Pole.

Almost Hyperspace: Random APOD Generator

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.

2021 November 28

A High Cliff on Comet Churyumov-Gerasimenko

Image Credit & Licence: ESA, Rosetta spacecraft, NAVCAM; Additional Processing: Stuart Atkinson

Explanation: This high cliff occurs not on a planet, not on a moon, but on a comet. It was discovered to be part of the dark nucleus of Comet Churyumov-Gerasimenko (CG) by Rosetta, a robotic spacecraft launched by ESA that rendezvoused with the Sun-orbiting comet in 2014. The ragged cliff, as featured here, was imaged by Rosetta in 2014. Although towering about one kilometer high, the low surface gravity of Comet CG would likely make it an accessible climb — and even a jump from the cliff survivable. At the foot of the cliff is relatively smooth terrain dotted with boulders as large as 20 meters across. Data from Rosetta indicates that the ice in Comet CG has a significantly different deuterium fraction — and hence likely a different origin — than the water in Earth’s oceans. Rosetta ended its mission with a controlled impact onto Comet CG in 2016. Comet CG has just completed another close approach to Earth and remains visible through a small telescope.

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.

2021 November 27

Messier 101

Image Credit: NASA, ESA, CFHT, NOAO;
Acknowledgement – K.Kuntz (GSFC), F.Bresolin (U.Hawaii), J.Trauger (JPL), J.Mould (NOAO), Y.-H.Chu (U. Illinois)

Explanation: Big, beautiful spiral galaxy M101 is one of the last entries in Charles Messier’s famous catalog, but definitely not one of the least. About 170,000 light-years across, this galaxy is enormous, almost twice the size of our own Milky Way. M101 was also one of the original spiral nebulae observed by Lord Rosse’s large 19th century telescope, the Leviathan of Parsontown. Assembled from 51 exposures recorded by the Hubble Space Telescope in the 20th and 21st centuries, with additional data from ground based telescopes, this mosaic spans about 40,000 light-years across the central region of M101 in one of the highest definition spiral galaxy portraits ever released from Hubble. The sharp image shows stunning features of the galaxy’s face-on disk of stars and dust along with background galaxies, some visible right through M101 itself. Also known as the Pinwheel Galaxy, M101 lies within the boundaries of the northern constellation Ursa Major, about 25 million light-years away.

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.

2021 November 26