Here is your weekly reminder of Psalm 19 — the planet Mercury.
Mercury is the smallest planet, as well as the planet closest to the Sun. It has a remarkably long day — a Mercury day lasts 88 Earth days — and a relatively short year (116 Earth days). Because of the peculiar ratio of its orbital period to its rotational period, a hypothetical observer on Mercury would experience only one day for every two years.
Mercury has no atmosphere, so the range of surface temperatures is extreme — -280 F during the night (the part of Mercury that faces away from the Sun) and up to 800 F during the day (the part of Mercury that faces toward the Sun).
Mercury has the most eccentric orbit in the Solar System, which means that out of all the planets, its orbit is the most like an ellipse. The part of its orbit closest to the Sun (the perihelion) precesses, which means Mercury’s orbit spirals around the Sun like a spirograph. Newton’s version of gravity could account for some of this precession, but not all of it. The reason for the discrepancy remained a mystery for centuries, until Einstein formulated his General Theory of Relativity, which explained the precession in terms of the way the Sun warps space around Mercury.
Here is your weekly reminder of Psalm 19 — the radio galaxy Hercules A.
Hercules A is a radio galaxy — an active galactic nucleus that emits an unusually high amount of radiation in the radio part of the EM spectrum. It’s about 2 billion light-years from Earth, and is the highest radio-emitting object in the constellation Hercules. Even though this galaxy is named for the constellation in which it appears, it certainly lives up to its name — it’s about 1,000 times more massive than the Milky Way, contains a black hole that is 1,000 times more massive than the black hole in the center of the Milky Way, and, as you can see in the image, it’s shooting out radio jets that span an incredible 1.5 million light-years in length.
This image is a composite of visible light (Hercules A in the center, as well as the stars in the foreground and other galaxies in the background) and radio light (the jets and lobes). The jets and lobes are comprised of charged particles accelerated to near-light speed and twisted magnetic fields. The jets and magnetic fields emanate from a region very close to the central, supermassive black hole.
Image credit: NASA, ESA, S. Baum and C. O’Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA).
Here is your weekly reminder of Psalm 19 — the Bubble Nebula.
The Bubble Nebula is a shell of gas surrounding a massive hot star. Stellar winds from the star push the bubble of gas out, while radiation from the star excites the hydrogen gas in the bubble and causes it to glow. The magenta wisps at the bottom of the image are remnants from a star that went supernova long ago.
The nebula resides in a giant molecular gas cloud in the constellation Cassiopeia, and is about 7,000 – 11,000 light-years away. The Bubble itself is 3 – 5 light-years in size, and, if you could see it with your naked eye, would be half the apparent size of the full Moon on the sky.
Image credit:T.A. Rector/University of Alaska Anchorage, H. Schweiker/WIYN and NOAO/AURA/NSF.
Here is your weekly reminder of Psalm 19 — Centaurus A.
Centaurus A is an active galaxy, also known as an AGN (active galactic nucleus). This means an unusually large amount of energy is radiating from its central region (i.e. its nucleus) compared with normal, quiescent galaxies like our own Milky Way. There is strong evidence that every AGN is powered by a supermassive black hole actively feeding on gaseous material; that material becomes superheated as it spirals down and releases a huge amount of radiation. The supermassive black hole in Centaurus A is measured to be 55 million times the mass of our Sun.
An extreme case of an AGN is a quasar, which can outshine a thousand Milky Way-type galaxies. Centaurus A is a less-extreme type of AGN called a radio galaxy, which means it emits an unusually large amount of radiation in the radio part of the spectrum.
The image above is a composite image showing the galaxy in visible light, with submillimeter emission in orange and X-ray emission in blue. Submillimeter radiation falls between the infrared and microwave parts of the electromagnetic spectrum; neither submillimeter nor X-ray emission can be detected with the human eye, so this is what’s called a false-color image. If we had eyes that could detect this sort of emission, this is what the galaxy might look like to us.
Centaurus A is about 12 million light-years from Earth, appearing in the constellation Centaurus. Its brightness makes it the fifth-brightest galaxy in the sky.
Image credit: ESO/WFI (Optical); MPIfR/ESO/APEX/A.Weiss et al. (Submillimetre); NASA/CXC/CfA/R.Kraft et al. (X-ray)
Here is your weekly reminder of Psalm 19 — galaxy M74.
Galaxy M74 is a perfect example of what’s called a grand design spiral galaxy, and it’s one of my all-time favorites. M74 appears face-on from our position on Earth, allowing us to see its symmetrical arms spiral gracefully out of its center. Note the blue clusters of star formation and glowing pink pockets of excited hydrogen gas. The dark swirls are dust lanes that obscure starlight, much the way dust in the Earth’s atmosphere blocks sunlight. M74 (the 74th object in the Messier catalog) is about 32 million light-years from Earth and appears in the constellation Pisces.
Image of M74 credit:NASA, ESA, and the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration.
This image shows Mars from 2500 km above its surface. The great slash covering more than half of Mars’ apparent diameter is Valles Marineris (Mariner Valley), named after its discoverer, the Mariner 9 orbiter that visited the Red Planet in the early 1970s. Valles Marineris dwarfs the Grand Canyon — it is 4,000 km long, 200 km wide, and in some parts it is 7 km deep. To put this into perspective, consider that the distance from Seattle to New York is 4,600 km.
Why do we love Mars so much? I think it’s because for two centuries Mars offered the most tantalizing possibility of extraterrestrial life in the universe. It started in the 18th century when William Herschel was moved by similarities between the Red Planet and Earth to speculate that it may be inhabited, and was further fueled a century later by Giovanni Schiaparelli’s observations of what he thought were canals on its surface.
We’ve observed Mars in much greater detail through several NASA missions, including landers, and have found no compelling evidence that is now or has ever been inhabited. Yet that hardly seems to matter. Perhaps it is because Mars offers a challenge that’s tantalizingly within reach — to visit the planet and perhaps even colonize it — that we remain so fascinated with our nearest planetary neighbor.
Here is your weekly reminder of Psalm 19 — the Horsehead Nebula.
The Horsehead is one of the best-known nebulae, owing to its distinctive shape in the likeness of — you guessed it — a horse’s head. This is one small part of a region of ongoing star formation in the great Orion Molecular Cloud Complex. The pink color in the cloud is a result of hydrogen gas excited by the ultraviolet light from a nearby star.
Most images of the Horsehead Nebula show it in visible light; the above image is in infrared, which allows us to peer into the inner structure of the cloud. Visible light is blocked by dusty gas, but longer wavelength infrared light can penetrate the dust.
Here is your weekly reminder of Psalm 19 — Saturn’s Rings and Titan.
At least I think it’s Titan. It’s one of Saturn’s moons, anyway. This image was taken by the Cassini spacecraft as it orbited Saturn. The spacecraft is named after the 17th century Italian astronomer, Giovanni Cassini, who studied Saturn extensively.
Here you can see the outer rings of Saturn, including the Cassini Division (the large division between the rings) and the Encke Gap (the smaller gap between the outermost rings). The rings are made of icy and rocky particles that range in size from a thousandth of a millimeter (about the size of smoke particles) up to a meter. It is not known for certain how the rings were formed. One hypothesis is that a moon of Saturn was either ripped apart by Saturn’s gravity or smashed by an asteroid, and the debris formed the rings; another is that the rings are made of leftover material from the formation of the solar system.
Image of Saturn and Titan, credit: Cassini Imaging Team, SSI, JPL, ESA, NASA.
Here is your weekly reminder of Psalm 19 — the Antennae Galaxies.
This spectacular pair of colliding spiral galaxies is located 45 million light-years from Earth. They started their encounter a few hundred million years ago, but the entire collision will likely last a couple billion years. Drawn together by their mutual gravitational attraction, they will undergo several passes and collisions before their stars and gas finally settle down to make a new, single galaxy. The interaction has sparked intense star formation, visible as the blue regions, surrounded by excited hydrogen gas, visible in pink.
The Antennae Galaxies derive their name from the long streams of stars that extend from the galaxies like antennae, seen in wider-field images, like the one below.
The Milky Way Galaxy is on a collision course with its nearest neighbor, the Andromeda galaxy. At some point during this future encounter, the collision will probably look much the same as the Antennae Galaxies:
Top image of the Antennae Galaxies, credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration. The wide-field ground-based image was taken by Robert Gendler.
Here is your weekly reminder of Psalm 19 — Jupiter and Io.
Last week, we were reminded of God’s handiwork with little Pluto, as imaged by the New Horizons spacecraft. New Horizons was launched in January 2006, and a little more than a year later it made a flyby of Jupiter, using the giant planet’s gravity to gain speed and shorten its journey to Pluto by three years. NASA made the most of that flyby to take images of Jupiter and its moons with unprecedented detail. The above image is a composite of Jupiter in infrared and its moon, Io, in true color. The blue and red in Jupiter’s atmosphere show high- and low-altitude clouds, respectively. The blueish flare on the night side of Io shows scattered sunlight off of a volcanic plume.
Image of Jupiter and Io, credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute/Goddard Space Flight Center.